ORCID Profile
0000-0001-5786-6989
Current Organisations
Fairfield Travel Health
,
Peter MacCallum Cancer Institute
,
Burnet Institute
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Applied Statistics | Biological Mathematics | Applied Mathematics | Operations Research |
Expanding Knowledge in the Biological Sciences | Disease Distribution and Transmission (incl. Surveillance and Response) | Expanding Knowledge in the Mathematical Sciences
Publisher: American Society for Microbiology
Date: 09-2009
DOI: 10.1128/IAI.00158-09
Abstract: In iduals repeatedly infected with malaria acquire protection from infection and disease immunity is thought to be primarily antibody-mediated and directed to blood-stage infection. Merozoite surface proteins involved in the invasion of host erythrocytes are likely targets of protective antibodies. We hypothesized that Papua New Guinean children ( n = 206) who acquire high antibody levels to two Plasmodium vivax merozoite proteins, Duffy binding protein region II (PvDBPII) and the 19-kDa C-terminal region of P. vivax merozoite surface protein 1 (PvMSP1 19 ), would have a delay in the time to reinfection following treatment to clear all blood-stage malaria infections. Ninety-four percent of the children were reinfected with P. vivax during biweekly follow-ups for 6 months. Since PvDBPII is polymorphic, we examined whether in iduals acquired strain-specific immunity to PvDBPII. Children with high antibody levels to a prevalent PvDBPII allele (O) were associated with a delay in the time to reinfection with the same variant of P. vivax by 25% compared to parasites expressing other PvDBPII alleles (age-adjusted hazard ratio, 0.75 [95% confidence interval, 0.56 to 1.00 by Cox regression]) and 39% lower incidence density parasitemia ( P = 0.01). Two other prevalent alleles (AH and P) showed a similar trend of 16% and 18% protection, respectively, against parasites with the same PvDBPII allele and reduced incidence density parasitemia. Antibodies directed to PvDBPII PNG-P and -O were both associated with a 21 to 26% reduction in the risk of P. vivax infections with higher levels of parasitemia ( parasites/μl), respectively. There was no association with high antibody levels to PvMSP1 19 and a delay in the time to P. vivax reinfection. Thus, anti-PvDBPII antibodies are associated with strain-specific immunity to P. vivax and support the use of PvDBPII for a vaccine against P. vivax .
Publisher: American Society of Tropical Medicine and Hygiene
Date: 05-08-2020
Publisher: Public Library of Science (PLoS)
Date: 10-09-2019
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C6AN02075E
Abstract: Total Reflectance Infrared Spectroscopy (ATR-FTIR) has the potential to become a new diagnostic tool for malaria and other diseases.
Publisher: The American Association of Immunologists
Date: 15-07-2013
Abstract: The development of effective malaria vaccines and immune biomarkers of malaria is a high priority for malaria control and elimination. Ags expressed by merozoites of Plasmodium falciparum are likely to be important targets of human immunity and are promising vaccine candidates, but very few Ags have been studied. We developed an approach to assess Ab responses to a comprehensive repertoire of merozoite proteins and investigate whether they are targets of protective Abs. We expressed 91 recombinant proteins, located on the merozoite surface or within invasion organelles, and screened them for quality and reactivity to human Abs. Subsequently, Abs to 46 proteins were studied in a longitudinal cohort of 206 Papua New Guinean children to define Ab acquisition and associations with protective immunity. Ab responses were higher among older children and those with active parasitemia. High-level Ab responses to rhoptry and microneme proteins that function in erythrocyte invasion were identified as being most strongly associated with protective immunity compared with other Ags. Additionally, Abs to new or understudied Ags were more strongly associated with protection than were Abs to current vaccine candidates that have progressed to phase 1 or 2 vaccine trials. Combinations of Ab responses were identified that were more strongly associated with protective immunity than responses to their single-Ag components. This study identifies Ags that are likely to be key targets of protective human immunity and facilitates the prioritization of Ags for further evaluation as vaccine candidates and/or for use as biomarkers of immunity in malaria surveillance and control.
Publisher: Oxford University Press (OUP)
Date: 11-11-2016
Abstract: Antibodies play a key role in acquired human immunity to Plasmodium falciparum (Pf) malaria and target merozoites to reduce or prevent blood-stage replication and the development of disease. Merozoites present a complex array of antigens to the immune system, and currently, there is only a partial understanding of the targets of protective antibodies and how responses to different antigens are acquired and boosted. We hypothesized that there would be differences in the rate of acquisition of antibodies to different antigens and how well they are boosted by infection, which impacts the acquisition of immunity. We examined responses to a range of merozoite antigens in 2 different cohorts of children and adults with different age structures and levels of malaria exposure. Overall, antibodies were associated with age, exposure, and active infection, and the repertoire of responses increased with age and active infection. However, rates of antibody acquisition varied between antigens and different regions within an antigen following exposure to malaria, supporting our hypothesis. Antigen-specific responses could be broadly classified into early response types in which antibodies were acquired early in childhood exposure and late response types that appear to require substantially more exposure for the development of substantial levels. We identified antigen-specific responses that were effectively boosted after recent infection, whereas other responses were not. These findings advance our understanding of the acquisition of human immunity to malaria and are relevant to the development of malaria vaccines targeting merozoite antigens and the selection of antigens for use in malaria surveillance.
Publisher: Springer Science and Business Media LLC
Date: 05-04-2017
Publisher: MyJove Corporation
Date: 02-11-2018
DOI: 10.3791/56797
Abstract: We demonstrate a method of quantification and detection of parasites in aqueous red blood cells (RBCs) by using a simple benchtop Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectrometer in conjunction with Multivariate Data Analysis (MVDA). 3D7 P. falciparum were cultured to 10% parasitemia ring stage parasites and used to spike fresh donor isolated RBCs to create a dilution series between 0-1%. 10 µL of each s le were placed onto the center of the ATR diamond window to acquire the spectrum. The s le data was treated to improve the signal to noise ratio and to remove the contribution of water, and then the second derivative was applied to resolve spectral features. The data were then analyzed using two types of MVDA: first Principal Component Analysis (PCA) to determine any outliers and then Partial Least Squares Regression (PLS-R) to build the quantification model.
Publisher: Faculty Opinions Ltd
Date: 04-11-2014
DOI: 10.12703/P6-100
Publisher: Cold Spring Harbor Laboratory
Date: 26-04-2021
DOI: 10.1101/2021.04.25.21255897
Abstract: SARS-CoV-2, the coronavirus causing COVID-19, has infected and killed several millions of people worldwide. Since the first COVID-19 outbreak in December 2019, SARS-CoV-2 has evolved with a few genetic variants associated with higher infectivity. We aimed to identify polymorphic loci in SARS-CoV-2 that can be used to define and monitor the viral epidemiology and population genetics in different geographical regions. Between December 2019 and September 2020, we s led 5,959 SARS-CoV-2 genomes. More than 80% of the genomes s led in Africa, Asia, Europe, North America, Oceania and South America were reportedly isolated from clinical infections in older patients, ≥ 20 years. We used the first indexed genome (NC_045512.2) as a reference and constructed multilocus genotypes (MLGs) for each s led genome based on amino acids detected at 74 polymorphic loci located in ORF1ab, ORF3a, ORF8, matrix (M), nucleocapsid (N) and spike (S) genes. Eight of the 74 loci were informative in estimating the risk of carrying infections with mutant alleles among different age groups, gender and geographical regions. Four mutant alleles - ORF1ab L 4715 , S G 614 , and N K 203 and R 204 reached 90% prevalence globally, coinciding with peaks in transmission but not COVID-19 severity, from March to August 2020. During this period, the MLG genetic ersity was moderate in Asia, Oceania and North America in contrast to Africa, Europe and South America, where lower genetic ersity and absence of linkage disequilibrium indicated clonal SARS-CoV-2 transmission. Despite close relatedness to Asian MLGs, MLGs in the global population were genetically differentiated by geographic region, suggesting structure in SARS-CoV-2 populations. Our findings demonstrate the utility of the 74 loci as a genetic tool to study and monitor SARS-CoV-2 transmission dynamics and evolution, which can inform future control interventions.
Publisher: Springer Science and Business Media LLC
Date: 10-02-2016
DOI: 10.1038/SREP20859
Abstract: During pregnancy immunolglobulin G (IgG) antibodies are transferred from mother to neonate across the placenta. Studies in high transmission areas have shown transfer of P. falciparum -specific IgG, but the extent and factors influencing maternal-foetal transfer in low transmission areas co-endemic for both P. falciparum and P. vivax are unknown. Pregnant women were screened weekly for Plasmodium infection. Mother-neonate paired serum s les at delivery were tested for IgG to antigens from P. falciparum , P. vivax and other infectious diseases. Antibodies to malarial and non-malarial antigens were highly correlated between maternal and neonatal s les (median [range] spearman ρ = 0.78 [0.57–0.93]), although Plasmodium spp. antibodies tended to be lower in neonates than mothers. Estimated gestational age at last P. falciparum infection, but not P. vivax infection, was positively associated with antibody levels in the neonate ( P. falciparum merozoite, spearman ρ median [range] 0.42 [0.33–0.66], Pf VAR2CSA 0.69 P. vivax ρ = 0.19 [0.09–0.3]). Maternal-foetal transfer of anti-malarial IgG to Plasmodium spp. antigens occurs in low transmission settings. P. vivax IgG acquisition is not associated with recent exposure unlike P. falciparum IgG, suggesting a difference in acquisition of antibodies. IgG transfer is greatest in the final weeks of pregnancy which has implications for the timing of future malaria vaccination strategies in pregnant women.
Publisher: Public Library of Science (PLoS)
Date: 29-10-2008
Publisher: Springer Science and Business Media LLC
Date: 11-02-2016
DOI: 10.1038/SREP20613
Abstract: MSP2 is an intrinsically disordered protein that is abundant on the merozoite surface and essential to the parasite Plasmodium falciparum . Naturally-acquired antibody responses to MSP2 are biased towards dimorphic sequences within the central variable region of MSP2 and have been linked to naturally-acquired protection from malaria. In a phase IIb study, an MSP2-containing vaccine induced an immune response that reduced parasitemias in a strain-specific manner. A subsequent phase I study of a vaccine that contained both dimorphic forms of MSP2 induced antibodies that exhibited functional activity in vitro . We have assessed the contribution of the conserved and variable regions of MSP2 to the generation of a strain-transcending antibody response by generating MSP2 chimeras that included conserved and variable regions of the 3D7 and FC27 alleles. Robust anti-MSP2 antibody responses targeting both conserved and variable regions were generated in mice, although the fine specificity and the balance of responses to these regions differed amongst the constructs tested. We observed significant differences in antibody subclass distribution in the responses to these chimeras. Our results suggest that chimeric MSP2 antigens can elicit a broad immune response suitable for protection against different strains of P. falciparum .
Publisher: Public Library of Science (PLoS)
Date: 20-09-2012
Publisher: Springer Science and Business Media LLC
Date: 11-09-2017
Publisher: Springer Science and Business Media LLC
Date: 10-05-2015
Publisher: Oxford University Press (OUP)
Date: 15-10-2010
DOI: 10.1086/656413
Abstract: Antibodies targeting blood stage antigens are important in protection against malaria, but the principle targets remain unclear. Erythrocyte-binding antigens (EBAs) are important erythrocyte invasion ligands used by merozoites and may be targets of protective immunity, but there are limited data examining their potential importance. We examined antibodies among 206 Papua New Guinean children who were treated with antimalarials at enrollment and observed prospectively for 6 months for reinfection and malaria. Immunoglobulin (Ig) G, IgG subclasses, and IgM to different regions of EBA175, EBA140, and EBA181 expressed as recombinant proteins were assessed in comparison with several other merozoite antigens. High levels of IgG to each of the EBAs were strongly associated with protection from symptomatic malaria and high density parasitemia, but not with risk of reinfection per se. The predominant IgG subclasses were either IgG1 or IgG3, depending on the antigen. The predominance of IgG1 versus IgG3 reflected structural features of specific regions of the proteins. IgG3 was most strongly associated with protection, even for those antigens that had an IgG1 predominant response. The EBAs appear important targets of acquired protective immunity. These findings support their further development as vaccine candidates.
Publisher: Springer Science and Business Media LLC
Date: 07-06-2019
Publisher: Springer Science and Business Media LLC
Date: 03-08-2016
Publisher: Cold Spring Harbor Laboratory
Date: 04-04-2019
DOI: 10.1101/597831
Abstract: The development of effective malaria vaccines remains a global health priority. Currently, the most advanced vaccine, known as RTS,S, has only shown modest efficacy in clinical trials. Thus, the development of more efficacious vaccines by improving the formulation of RTS,S for increased efficacy or to interrupt malaria transmission are urgently needed. The RTS,S vaccine is based on the presentation of a fragment of the sporozoite antigen on the surface of virus-like particles (VLPs) based on human hepatitis B virus (HBV). In this study, we have developed and evaluated a novel VLP platform based on duck HBV (known as Metavax) for malaria vaccine development. This platform can incorporate large and complex proteins into VLPs and is produced in a Hansenula cell line compatible with cGMP vaccine production. Here, we have established the expression of leading P. falciparum malaria vaccine candidates as VLPs. This includes Pfs230 and Pfs25, which are candidate transmission-blocking vaccine antigens. We demonstrated that the VLPs effectively induce antibodies to malaria vaccine candidates with minimal induction of antibodies to the duck-HBV scaffold antigen. Antibodies to Pfs230 also recognised native protein on the surface of gametocytes, and antibodies to both Pfs230 and Pfs25 demonstrated transmission-reducing activity in standard membrane feeding assays. These results establish the potential utility of this VLP platform for malaria vaccines, which may be suitable for the development of multi-component vaccines that achieve high vaccine efficacy and transmission-blocking immunity.
Publisher: Springer Science and Business Media LLC
Date: 05-02-2019
DOI: 10.1038/S41467-019-08528-Z
Abstract: Antibodies against P . falciparum merozoites fix complement to inhibit blood-stage replication in naturally-acquired and vaccine-induced immunity however, specific targets of these functional antibodies and their importance in protective immunity are unknown. Among malaria-exposed in iduals, we show that complement-fixing antibodies to merozoites are more strongly correlated with protective immunity than antibodies that inhibit growth quantified using the current reference assay for merozoite vaccine evaluation. We identify merozoite targets of complement-fixing antibodies and identify antigen-specific complement-fixing antibodies that are strongly associated with protection from malaria in a longitudinal study of children. Using statistical modelling, combining three different antigens targeted by complement-fixing antibodies could increase the potential protective effect to over 95%, and we identify antigens that were common in the most protective combinations. Our findings support antibody-complement interactions against merozoite antigens as important anti-malaria immune mechanisms, and identify specific merozoite antigens for further evaluation as vaccine candidates.
Publisher: Oxford University Press (OUP)
Date: 21-06-2018
DOI: 10.1093/BIOINFORMATICS/BTY474
Abstract: A sliding window analysis over a protein or genomic sequence is commonly performed, and we present a Python tool, BioStructMap, that extends this concept to three-dimensional (3D) space, allowing the application of a 3D sliding window analysis over a protein structure. BioStructMap is easily extensible, allowing the user to apply custom functions to spatially aggregated data. BioStructMap also allows mapping of underlying genomic sequences to protein structures, allowing the user to perform genetic-based analysis over spatially linked codons—this has applications when selection pressures arise at the level of protein structure. The Python BioStructMap package is available at ndrewguy/biostructmap and released under the MIT License. An online server implementing standard functionality is available at biostructmap.burnet.edu.au. Supplementary data are available at Bioinformatics online.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 05-2015
Publisher: The American Association of Immunologists
Date: 15-11-2010
Abstract: Abs targeting blood-stage Ags of Plasmodium falciparum are important in acquired immunity to malaria, but major targets remain unclear. The P. falciparum reticulocyte-binding homologs (PfRh) are key ligands used by merozoites during invasion of erythrocytes. PfRh2a and PfRh2b are functionally important members of this family and may be targets of protective immunity, but their potential role in human immunity has not been examined. We expressed eight recombinant proteins covering the entire PfRh2 common region, as well as PfRh2a- and PfRh2b-specific regions. Abs were measured among a cohort of 206 Papua New Guinean children who were followed prospectively for 6 mo for reinfection and malaria. At baseline, Abs were associated with increasing age and active infection. High levels of IgG to all PfRh2 protein constructs were strongly associated with protection from symptomatic malaria and high-density parasitemia. The predominant IgG subclasses were IgG1 and IgG3, with little IgG2 and IgG4 detected. To further understand the significance of PfRh2 as an immune target, we analyzed PfRh2 sequences and found that polymorphisms are concentrated in an N-terminal region of the protein and seem to be under ersifying selection, suggesting immune pressure. Cluster analysis arranged the sequences into two main groups, suggesting that many of the haplotypes identified may be antigenically similar. These findings provide evidence suggesting that PfRh2 is an important target of protective immunity in humans and that Abs act by controlling blood-stage parasitemia and support its potential for vaccine development.
Publisher: Public Library of Science (PLoS)
Date: 05-03-2015
Publisher: American Society for Microbiology
Date: 03-2009
DOI: 10.1128/IAI.01129-08
Abstract: Substantial evidence indicates that antibodies to Plasmodium falciparum merozoite antigens play a role in protection from malaria, although the precise targets and mechanisms mediating immunity remain unclear. Different malaria antigens induce distinct immunoglobulin G (IgG) subclass responses, but the importance of different responses in protective immunity from malaria is not known and the factors determining subclass responses in vivo are poorly understood. We examined IgG and IgG subclass responses to the merozoite antigens MSP1-19 (the 19-kDa C-terminal region of merozoite surface protein 1), MSP2 (merozoite surface protein 2), and AMA-1 (apical membrane antigen 1), including different polymorphic variants of these antigens, in a longitudinal cohort of children in Papua New Guinea. IgG1 and IgG3 were the predominant subclasses of antibodies to each antigen, and all antibody responses increased in association with age and exposure without evidence of increasing polarization toward one subclass. The profiles of IgG subclasses differed somewhat for different alleles of MSP2 but not for different variants of AMA-1. In iduals did not appear to have a propensity to make a specific subclass response irrespective of the antigen. Instead, data suggest that subclass responses to each antigen are generated independently among in iduals and that antigen properties, rather than host factors, are the major determinants of IgG subclass responses. High levels of AMA-1-specific IgG3 and MSP1-19-specific IgG1 were strongly predictive of a reduced risk of symptomatic malaria and high-density P. falciparum infections. However, no antibody response was significantly associated with protection from parasitization per se. Our findings have major implications for understanding human immunity and for malaria vaccine development and evaluation.
Publisher: Cold Spring Harbor Laboratory
Date: 04-2019
DOI: 10.1101/595538
Abstract: 1. Malaria caused by Plasmodium falciparum is one of the major threats to human health globally. Despite huge efforts in malaria control and eradication, highly effective vaccines are urgently needed, including vaccines that can block malaria transmission. Chimeric virus-like particles (VLP) have emerged as a promising strategy to develop new malaria vaccine candidates. We developed yeast cell lines and processes for the expression of malaria transmission-blocking vaccine candidates Pfs25 and Pfs230 as VLP and VLP were analyzed for purity, size, protein incorporation rate and expression of malaria antigens. In this study, a novel platform for the display of Plasmodium falciparum antigens on chimeric VLP is presented. Leading transmission-blocking vaccine candidates Pfs25 and Pfs230 were genetically fused to the small surface protein (dS) of the duck hepatitis B virus (DHBV). The resulting fusion proteins were co-expressed in recombinant Hansenula polymorpha (syn. Pichia angusta, Ogataea polymorpha ) strains along with the wild-type dS as the VLP scaffold protein. Through this strategy, chimeric VLP containing Pfs25 or the Pfs230-derived fragments Pfs230c or Pfs230D1M were purified. Up to 100 mg chimeric VLP were isolated from 100 g dry cell weight with a maximum protein purity of 90 % on the protein level. Expression of the Pfs230D1M construct was more efficient than Pfs230c and enabled VLP with higher purity. VLP showed reactivity with transmission-blocking antibodies and supported the surface display of the malaria antigens on the native VLP. The incorporation of leading Plasmodium falciparum transmission-blocking antigens into the dS-based VLP scaffold is a promising novel strategy for their display on nano-scaled particles. Competitive processes for efficient production and purification were established in this study.
Publisher: American Society of Tropical Medicine and Hygiene
Date: 05-10-2010
Publisher: American Chemical Society (ACS)
Date: 20-04-2018
DOI: 10.1021/ACS.CHEMREV.7B00661
Abstract: New technologies to diagnose malaria at high sensitivity and specificity are urgently needed in the developing world where the disease continues to pose a huge burden on society. Infrared and Raman spectroscopy-based diagnostic methods have a number of advantages compared with other diagnostic tests currently on the market. These include high sensitivity and specificity for detecting low levels of parasitemia along with ease of use and portability. Here, we review the application of vibrational spectroscopic techniques for monitoring and detecting malaria infection. We discuss the role of vibrational (infrared and Raman) spectroscopy in understanding the processes of parasite biology and its application to the study of interactions with antimalarial drugs. The distinct molecular phenotype that characterizes malaria infection and the high sensitivity enabling detection of low parasite densities provides a genuine opportunity for vibrational spectroscopy to become a front-line tool in the elimination of this deadly disease and provide molecular insights into the chemistry of this unique organism.
Publisher: Cold Spring Harbor Laboratory
Date: 20-05-2020
DOI: 10.1101/2020.05.14.20102475
Abstract: Background: SARS-CoV-2, the viral agent responsible for coronavirus disease 2019 (COVID-19) was identified in Wuhan, China at the end of December 2019. It rapidly spread to the rest of the world, and was declared a Public Health Emergency of International Concern on the 30th of January 2020. Our understanding of the virus, it is clinical manifestations and treatment options continues to evolve at an unparalleled pace. Objective: This review sought to summarise the key literature regarding transmission, case definitions, clinical management and trials, and performed a systematic review of reported clinical data on COVID-19. Synthesis methods: Two reviewers selected all the literature independently, and extracted information according to pre-defined topics. Results: COVID-19 is pandemic with ~4 million cases and 270,000 deaths in 210 countries as of 8 May 2020. Our review of reports showed that SARS-CoV-2 was mainly transmitted via inhalation of respiratory droplets containing the virus and had an incubation period of four to six days. The commonly reported symptoms were fever (80%) and cough (60%) across the spectrum of clinical disease - mild, moderate, severe and critical. Categorization of these cases for home care or hospital management need to be well defined considering the age of the patient and the presence of underlying co-morbidities. The case definitions we reviewed varied among affected countries, which could have contributed to the differences observed in the mean case fatality rates among continents: Oceania (1%), Asia (3%), Africa (4%), South America (5%), North America (6%) and Europe (10%). Asymptomatic cases, which constituted an estimated 80% of COVID-19 cases are a huge threat to control efforts. Conclusion: The presence of fever and cough may be sufficient to warrant a COVID-19 testing but using these symptoms in isolation will miss a proportion of cases. A clear definition of a COVID-19 case is important for managing, treating and tracking clinical illness. While several treatments are in development or in clinical trials for COVID-19, home care of mild/moderate cases and hospital care for severe and critical cases remain the recommended management for the disease. Quarantine measures and social distancing can help control the spread of SARS-CoV-2.
Publisher: Oxford University Press (OUP)
Date: 10-09-2012
Publisher: American Society for Microbiology
Date: 02-2015
DOI: 10.1128/IAI.02398-14
Abstract: In iduals in areas of Plasmodium falciparum endemicity develop immunity to malaria after repeated exposure. Knowledge of the acquisition and nature of protective immune responses to P. falciparum is presently limited, particularly for young children. We examined antibodies (IgM, IgG, and IgG subclasses) to merozoite antigens and their relationship to the prospective risk of malaria in children 1 to 4 years of age in a region of malaria endemicity in Papua New Guinea. IgG, IgG1, and IgG3 responses generally increased with age, were higher in children with active infection, and reflected geographic heterogeneity in malaria transmission. Antigenic properties, rather than host factors, appeared to be the main determinant of the type of IgG subclass produced. High antibody levels were not associated with protection from malaria in contrast, they were typically associated with an increased risk of malaria. Adjustment for malaria exposure, using a novel molecular measure of the force of infection by P. falciparum , accounted for much of the increased risk, suggesting that the antibodies were markers of higher exposure to P. falciparum . Comparisons between antibodies in this cohort of young children and in a longitudinal cohort of older children suggested that the lack of protective association was explained by lower antibody levels among young children and that there is a threshold level of antibodies required for protection from malaria. Our results suggest that in populations with low immunity, such as young children, antibodies to merozoite antigens may act as biomarkers of malaria exposure and that, with increasing exposure and responses of higher magnitude, antibodies may act as biomarkers of protective immunity.
Publisher: Wiley
Date: 05-05-2009
DOI: 10.1038/ICB.2009.27
Abstract: Malaria is a leading cause of mortality and morbidity globally, and effective vaccines are urgently needed. Malaria vaccine approaches can be broadly grouped as pre-erythrocytic, blood stage and transmission blocking. This review focuses on blood-stage vaccines, and considers the evidence supporting the development of blood-stage vaccines, the advantages and challenges of this approach, potential targets, human vaccine studies and future directions. There is a strong rationale for the development of vaccines based on antigens of blood-stage parasites. Symptomatic malaria is caused by blood-stage parasitemia and acquired immunity in humans largely targets blood-stage antigens. Several candidate vaccines have proved efficacious in animal models and at least one vaccine showed partial efficacy in a clinical trial. At present, all leading candidate blood-stage antigens are merozoite proteins, located on the merozoite surface or within the apical organelles. Major challenges and priorities include overcoming antigenic ersity, identification of protective epitopes, understanding the nature and targets of protective immune responses, and defining antigen combinations that give the greatest efficacy. Additionally, objective criteria and approaches are needed to prioritize the large number of candidate antigens, and strong candidates need to be tested in clinical trials as quickly as possible.
Publisher: Springer Science and Business Media LLC
Date: 26-08-2016
Publisher: Elsevier BV
Date: 03-2021
Publisher: Public Library of Science (PLoS)
Date: 19-09-2011
Publisher: American Chemical Society (ACS)
Date: 28-04-2017
DOI: 10.1021/ACS.ANALCHEM.6B04578
Abstract: New diagnostic tools that can detect malaria parasites in conjunction with other diagnostic parameters are urgently required. In this study, Attenuated Total Reflection Fourier transform infrared (ATR-FTIR) spectroscopy in combination with Partial Least Square Discriminant Analysis (PLS-DA) and Partial Least Square Regression (PLS-R) have been applied as a point-of-care test for identifying malaria parasites, blood glucose, and urea levels in whole blood s les from thick blood films on glass slides. The specificity for the PLS-DA was found to be 98% for parasitemia levels >0.5%, but a rather low sensitivity of 70% was achieved because of the small number of negative s les in the model. In PLS-R the Root Mean Square Error of Cross Validation (RMSECV) for parasite concentration (0-5%) was 0.58%. Similarly, for glucose (0-400 mg/dL) and urea (0-250 mg/dL) spiked s les, relative RMSECVs were 16% and 17%, respectively. The method reported here is the first ex le of multianalyte/disease diagnosis using ATR-FTIR spectroscopy, which in this case, enabled the simultaneous quantification of glucose and urea analytes along with malaria parasitemia quantification using one spectrum obtained from a single drop of blood on a glass microscope slide.
Publisher: Springer Science and Business Media LLC
Date: 05-07-2006
Publisher: Elsevier BV
Date: 10-2015
DOI: 10.1016/J.MOLIMM.2015.03.255
Abstract: Monoclonal antibodies are being developed as therapeutics to complement drugs and vaccines or to fill the gap where no drugs or vaccines exist. These therapeutic antibodies (ThAb) may be especially important for infectious diseases in which there is antibiotic resistance, toxin-mediated pathogenesis, or for emerging pathogens. The unique structure of antibodies determines the specific nature of the effector function, so when developing ThAb, the desired effector functions need to be considered and integrated into the design and development processes to ensure maximum efficacy and safety. Antibody subclass is a critical consideration, but it is noteworthy that almost all ThAb that are licenced or currently in development utilise an IgG1 backbone. This review outlines the major structural properties that vary across subclasses, how these properties affect functional immunity, and discusses the various approaches used to study subclass responses to infectious diseases. We also review the factors associated with the selection of antibody subclasses when designing ThAb and highlight circumstances where different subclass properties might be beneficial when applied to particular infectious diseases. These approaches are critical to the future design of ThAb and to the study of naturally-acquired and vaccine-induced immunity.
Publisher: AMPCo
Date: 23-01-2012
DOI: 10.5694/MJA11.11026
Abstract: Murray Valley encephalitis virus (MVEV) is a mosquito-borne virus that is found across Australia, Papua New Guinea and Irian Jaya. MVEV is endemic to northern Australia and causes occasional outbreaks across south-eastern Australia. 2011 saw a dramatic increase in MVEV activity in endemic regions and the re-emergence of MVEV in south-eastern Australia. This followed significant regional flooding and increased numbers of the main mosquito vector, Culex annulirostris, and was evident from the widespread seroconversion of sentinel chickens, fatalities among horses and several cases in humans, resulting in at least three deaths. The last major outbreak in Australia was in 1974, during which 58 cases were identified and the mortality rate was about 20%. With the potential for a further outbreak of MVEV in the 2011-2012 summer and following autumn, we highlight the importance of this disease, its clinical characteristics and radiological and laboratory features. We present a suspected but unproven case of MVEV infection to illustrate some of the challenges in clinical management. It remains difficult to establish an early diagnosis of MVEV infection, and there is a lack of proven therapeutic options.
Publisher: Public Library of Science (PLoS)
Date: 04-09-2019
Publisher: Springer Science and Business Media LLC
Date: 09-11-2016
Publisher: Oxford University Press (OUP)
Date: 07-2015
DOI: 10.1093/CID/CIV525
Publisher: Springer Science and Business Media LLC
Date: 17-08-2018
Publisher: Public Library of Science (PLoS)
Date: 25-01-2017
Publisher: Elsevier BV
Date: 03-2017
DOI: 10.1016/J.JMB.2017.02.003
Abstract: Merozoite surface protein 2 (MSP2) is an intrinsically disordered antigen that is abundant on the surface of the malaria parasite Plasmodium falciparum. The two allelic families of MSP2, 3D7 and FC27, differ in their central variable regions, which are flanked by highly conserved C-terminal and N-terminal regions. In a vaccine trial, full-length 3D7 MSP2 induced a strain-specific protective immune response despite the detectable presence of conserved region antibodies. This work focuses on the conserved C-terminal region of MSP2, which includes the only disulphide bond in the protein and encompasses key epitopes recognised by the mouse monoclonal antibodies 4D11 and 9H4. Although the 4D11 and 9H4 epitopes are overlapping, immunofluorescence assays have shown that the mouse monoclonal antibody 4D11 binds to MSP2 on the merozoite surface with a much stronger signal than 9H4. Understanding the structural basis for this antigenic difference between these antibodies will help direct the design of a broad-spectrum and MSP2-based malaria vaccine. 4D11 and 9H4 were reengineered into antibody fragments [variable region fragment (Fv) and single-chain Fv (scFv)] and were validated as suitable models for their full-sized IgG counterparts by surface plasmon resonance and isothermal titration calorimetry. An alanine scan of the 13-residue epitope 3D7-MSP2
Publisher: Oxford University Press (OUP)
Date: 23-03-2018
Abstract: Human immunization with a polymorphic malaria vaccine candidate, MSP2, induced functional cross-reactive antibodies targeting conserved epitopes. This contrasts with naturally acquired antibodies, which target polymorphic epitopes, mediating immune escape. Findings reveal potential to overcome antigenic ersity for effective malaria vaccines.
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5CC00438A
Abstract: APTEC: aptamer-tethered enzyme capture as a novel rapid diagnostic test for malaria.
Publisher: Springer Science and Business Media LLC
Date: 11-09-2017
Publisher: Oxford University Press (OUP)
Date: 31-01-2016
Publisher: Springer Science and Business Media LLC
Date: 11-05-2021
Publisher: Public Library of Science (PLoS)
Date: 29-10-2015
Publisher: The American Association of Immunologists
Date: 15-07-2013
Abstract: Abs that inhibit Plasmodium falciparum invasion of erythrocytes form an important component of human immunity against malaria, but key target Ags are largely unknown. Phenotypic variation by P. falciparum mediates the evasion of inhibitory Abs, contributing to the capacity of P. falciparum to cause repeat and chronic infections. However, Ags involved in mediating immune evasion have not been defined, and studies of the function of human Abs are limited. In this study, we used novel approaches to determine the importance of P. falciparum erythrocyte-binding Ags (EBAs), which are important invasion ligands, as targets of human invasion-inhibitory Abs and define their role in contributing to immune evasion through variation in function. We evaluated the invasion-inhibitory activity of acquired Abs from malaria-exposed children and adults from Kenya, using P. falciparum with disruption of genes encoding EBA140, EBA175, and EBA181, either in idually or combined as EBA140/EBA175 or EBA175/EBA181 double knockouts. Our findings provide important new evidence that variation in the expression and function of the EBAs plays an important role in evasion of acquired Abs and that a substantial amount of phenotypic ersity results from variation in expression of different EBAs that contributes to immune evasion by P. falciparum. All three EBAs were identified as important targets of naturally acquired inhibitory Abs demonstrated by differential inhibition of parental parasites greater than EBA knockout lines. This knowledge will help to advance malaria vaccine development and suggests that multiple invasion ligands need to be targeted to overcome the capacity of P. falciparum for immune evasion.
Publisher: Springer Science and Business Media LLC
Date: 07-2014
Publisher: Springer Science and Business Media LLC
Date: 02-06-2016
Publisher: Rockefeller University Press
Date: 11-07-2016
DOI: 10.1084/JEM.20151467
Abstract: Naive CD4+ T cells differentiate into specific effector subsets—Th1, Th2, Th17, and T follicular helper (Tfh)—that provide immunity against pathogen infection. The signaling pathways involved in generating these effector cells are partially known. However, the effects of mutations underlying human primary immunodeficiencies on these processes, and how they compromise specific immune responses, remain unresolved. By studying in iduals with mutations in key signaling pathways, we identified nonredundant pathways regulating human CD4+ T cell differentiation in vitro. IL12Rβ1/TYK2 and IFN-γR/STAT1 function in a feed-forward loop to induce Th1 cells, whereas IL-21/IL-21R/STAT3 signaling is required for Th17, Tfh, and IL-10–secreting cells. IL12Rβ1/TYK2 and NEMO are also required for Th17 induction. Strikingly, gain-of-function STAT1 mutations recapitulated the impact of dominant-negative STAT3 mutations on Tfh and Th17 cells, revealing a putative inhibitory effect of hypermorphic STAT1 over STAT3. These findings provide mechanistic insight into the requirements for human T cell effector function, and explain clinical manifestations of these immunodeficient conditions. Furthermore, they identify molecules that could be targeted to modulate CD4+ T cell effector function in the settings of infection, vaccination, or immune dysregulation.
Publisher: Springer Science and Business Media LLC
Date: 02-05-2018
Publisher: American Society of Hematology
Date: 03-06-2010
DOI: 10.1182/BLOOD-2009-09-243725
Abstract: During erythrocyte invasion, Plasmodium falciparum merozoites use multiple receptor-ligand interactions in a series of coordinated events, but current knowledge of these interactions is limited. Using real-time imaging of invasion, we established that heparin-like molecules block early, and essential, events in erythrocyte invasion by merozoites. All P falciparum isolates tested, and parasites using different invasion pathways were inhibited to comparable levels. Furthermore, it was not possible to select for heparin-resistant parasites. Heparin-like molecules occur naturally on the surface of human erythrocytes, where they may act as receptors for binding of merozoite surface proteins. Consistent with this, we demonstrated that MSP1-42, a processed form of merozoite surface protein 1 (MSP1) involved in invasion, bound heparin in a specific manner furthermore, binding was observed with the secondary processing fragment MSP1-33, but not MSP1-19. We defined key structural requirements of heparin-like molecules for invasion inhibition and interactions with MSP1-42. Optimal activity required a degree of sulfation more than or equal to 2, disulfation of the N-acetylglucosamine or hexuronic acid residue, and a minimum chain length of 6 monosaccharides. These findings have significant implications for understanding P falciparum invasion of erythrocytes and the development of novel therapeutics and vaccines.
Publisher: Springer Science and Business Media LLC
Date: 16-10-2014
Publisher: Elsevier BV
Date: 07-2011
DOI: 10.1016/J.IMBIO.2010.12.010
Abstract: This study aimed to evaluate whether intermittent preventive treatment in infants with sulfadoxine-pyrimethamine (IPTi-SP) had an effect on the acquisition of IgG against Plasmodium falciparum variant surface antigens (VSA) and growth-inhibitory antibodies in Manhiça, Mozambique. In addition, we assessed factors affecting the magnitude of these responses and the association between antibody levels and protection against malaria. IgG to VSA expressed by MOZ2, R29 and E8B parasite isolates were measured in plasma s les collected at 5, 9, 12 and 24 months of age by flow cytometry. Growth-inhibitory antibodies in dialyzed plasmas using GFP-D10 parasites were measured by flow cytometry at 12 and 24 months. IPTi-SP did not significantly modify the levels of IgG against VSA nor the growth-inhibitory capacity of antibodies up to 2 years of age. Age but not previous episodes of malaria influenced the magnitude of these responses. In addition, anti-VSA IgG levels were 7% higher in children with current P. falciparum infection and were associated with neighborhood of residence. Children aged 24 months had 10% less parasite growth than those aged 12 months (95% CI 0.88-0.93, P<0.0001). Growth-inhibitory antibodies correlated with levels of IgG against AMA-1, when evaluating the 10% (R(2)=0.444, P=0.049) and 20% (R(2)=0.230, P=0.037) highest inhibitory s les. None of the responses were associated with subsequent risk of malaria. In conclusion, IPTi-SP does not negatively affect the development of antibody responses thought to be major contributors to the acquisition of immunity to malaria in infancy.
Publisher: Springer Science and Business Media LLC
Date: 22-08-2019
Publisher: Springer Science and Business Media LLC
Date: 12-03-2018
DOI: 10.1038/S41598-018-22592-3
Abstract: Humoral immune responses against the malaria parasite are an important component of a protective immune response. Antibodies are often directed towards conformational epitopes, and the native structure of the antigenic region is usually critical for antibody recognition. We examined the structural features of various Plasmodium antigens that may impact on epitope location, by performing a comprehensive analysis of known and modelled structures from P. falciparum . Examining the location of known polymorphisms over all available structures, we observed a strong propensity for polymorphic residues to be exposed on the surface and to occur in particular secondary structure segments such as hydrogen-bonded turns. We also utilised established prediction algorithms for B-cell epitopes and MHC class II binding peptides, examining predicted epitopes in relation to known polymorphic sites within structured regions. Finally, we used the available structures to examine polymorphic hotspots and Tajima’s D values using a spatial averaging approach. We identified a region of Pf AMA1 involving both domains II and III under a high degree of balancing selection relative to the rest of the protein. In summary, we developed general methods for examining how sequence-based features relate to one another in three-dimensional space and applied these methods to key P. falciparum antigens.
Publisher: Public Library of Science (PLoS)
Date: 19-01-2010
Publisher: American Chemical Society (ACS)
Date: 11-03-2014
DOI: 10.1021/AC404188G
Abstract: Insecticide resistance is one of the most prevalent ex les of anthropogenic genetic change, yet our understanding of metabolic-based resistance remains limited by the analytical challenges associated with rapidly tracking the in vivo metabolites of insecticides at nonlethal doses. Here, using twin ion mass spectrometry analysis of the extracts of whole Drosophila larvae and excreta, we show that (i) eight metabolites of the neonicotinoid insecticide, imidacloprid, can be detected when formed by susceptible larval genotypes and (ii) the specific overtranscription of a single gene product, Cyp6g1, associated with the metabolic resistance to neonicotinoids, results in a significant increase in the formation of three imidacloprid metabolites that are formed in C-H bond activation reactions that is, Cyp6g1 is directly linked to the enhanced metabolism of imidacloprid in vivo. These results establish a rapid and sensitive method for dissecting the metabolic machinery of insects by directly linking single gene products to insecticide metabolism.
Publisher: Elsevier BV
Date: 10-2013
Abstract: To assess evidence of recent and past exposure to Murray Valley encephalitis virus (MVEV) and West Nile clade Kunjin virus (KUNV) in residents of the Murray Valley, Victoria, during a period of demonstrated activity of both viruses in early 2011. A cross-sectional serosurvey using two convenience s les: stored serum specimens from a diagnostic laboratory in Mildura and blood donors from the Murray Valley region. Specimens were collected between April and July 2011. The main outcome measure was total antibody (IgM and IgG) reactivity against MVEV and KUNV measured using an enzyme immunoassay and defined as inhibiting binding of monoclonal antibodies by >50%, when compared to negative controls. Evidence of recent exposure was measured by the presence of MVEV and KUNV IgM detected by immunofluorescence. Of 1,115 specimens, 24 (2.2%, 95% CI 1.3-3.0%) were positive for MVEV total antibody, and all were negative for MVEV IgM. Of 1,116 specimens, 34 (3.1%, 95% CI 2.0-4.0%) were positive for KUNV total antibody, and 3 (0.27%) were KUNV IgM positive. Total antibody seroprevalence for both viruses was higher in residents born before 1974. Despite widespread MVEV and KUNV activity in early 2011, this study found that seroprevalence of antibodies to both viruses was low (<5%) and little evidence of recent exposure. Our findings suggest both viruses remain epizootic in the region and local residents remain potentially susceptible to future outbreaks.
Publisher: Springer Science and Business Media LLC
Date: 08-09-2016
DOI: 10.1038/SREP33094
Abstract: Understanding the targets and mechanisms of human immunity to malaria is important for advancing the development of highly efficacious vaccines and serological tools for malaria surveillance. The PfRH5 and PfRipr proteins form a complex on the surface of P. falciparum merozoites that is essential for invasion of erythrocytes and are vaccine candidates. We determined IgG subclass responses to these proteins among malaria-exposed in iduals in Papua New Guinea and their association with protection from malaria in a longitudinal cohort of children. Cytophilic subclasses, IgG1 and IgG3, were predominant with limited IgG2 and IgG4, and IgG subclass-specific responses were higher in older children and those with active infection. High IgG3 to PfRH5 and PfRipr were significantly and strongly associated with reduced risk of malaria after adjusting for potential confounding factors, whereas associations for IgG1 responses were generally weaker and not statistically significant. Results further indicated that malaria exposure leads to the co-acquisition of IgG1 and IgG3 to PfRH5 and PfRipr, as well as to other PfRH invasion ligands, PfRH2 and PfRH4. These findings suggest that IgG3 responses to PfRH5 and PfRipr may play a significant role in mediating naturally-acquired immunity and support their potential as vaccine candidates and their use as antibody biomarkers of immunity.
Publisher: Springer Science and Business Media LLC
Date: 19-09-2017
Publisher: Elsevier BV
Date: 2015
DOI: 10.1016/J.STR.2015.10.028
Abstract: Disordered proteins are important antigens in a range of infectious diseases. Little is known, however, about the molecular details of recognition of disordered antigens by their cognate antibodies. Using a large dataset of protein antigens, we show that disordered epitopes are as likely to be recognized by antibodies as ordered epitopes. Moreover, the affinity with which antigens are recognized is, unexpectedly, only weakly dependent on the degree of disorder within the epitope. Structurally defined complexes of ordered and disordered protein antigens with their cognate antibodies reveal that disordered epitopes are smaller than their ordered counterparts, but are more efficient in their interactions with antibody. Our results demonstrate that disordered antigens are bona fide targets of antibody recognition, and that recognition of disordered epitopes is particularly sensitive to epitope variation, a finding with implications for the effects of disorder on the specificity of molecular recognition more generally.
Location: United Kingdom of Great Britain and Northern Ireland
Location: Australia
Start Date: 2012
End Date: 2014
Funder: Royal Australasian College of Physicians
View Funded ActivityStart Date: 2013
End Date: 2015
Funder: National Health and Medical Research Council
View Funded ActivityStart Date: 2012
End Date: 2015
Funder: National Health and Medical Research Council
View Funded ActivityStart Date: 04-2020
End Date: 04-2024
Amount: $520,000.00
Funder: Australian Research Council
View Funded Activity