Biology subjects

Duffy, P. E.

Publications and source records attributed to Duffy, P. E..

4 recordsLinked to original sources

bioRxiv2022

Aotus nancymaae model predicts human immune response to the placental malaria vaccine candidate VAR2CSA

Placental malaria vaccines (PMV) are being developed to prevent severe sequelae of placental malaria (PM) in pregnant women and their offspring. The leading candidate vaccine antigen VAR2CSA mediates parasite binding to placental receptor chondroitin sulfate A (CSA). Despite promising results in small animal studies, recent human trials of the first two PMV candidates (PAMVAC and PRIMVAC) generated limited cross-reactivity and cross-inhibitory activity to heterologous parasites. Here, we immunized Aotus nancymaae monkeys with three PMV candidates (PAMVAC, PRIMVAC and ID1-ID2a_M1010) adjuvanted with Alhydrogel(R), and exploited the model to investigate boosting of functional vaccine responses during PM episodes as well as with nanoparticle antigens. PMV candidates induced high levels of antigen-specific IgG with significant cross-reactivity across PMV antigens by ELISA. Conversely, PMV antibodies recognized native VAR2CSA and blocked CSA-adhesion of only homologous parasites and not heterologous parasites. PM episodes did not significantly boost VAR2CSA antibody levels or serum functional activity; nanoparticle and monomer antigens alike boosted serum reactivity but not functional activities. Overall, PMV candidates induced functional antibodies with limited heterologous activity in Aotus monkeys, similar to responses reported in humans. The Aotus model appears suitable for preclinical down-selection of PMV candidates and assessment of antibody boosting by PM episodes. Research in Context Evidence before this studyThe Plasmodium falciparum erythrocyte membrane protein VAR2CSA is the leading vaccine candidate antigen to protect pregnant women against placental malaria (PM), which causes serious adverse pregnancy outcomes particularly in first-time mothers living in malaria-endemic areas. Two VAR2CSA-based vaccines (PAMVAC and PRIMVAC) induced strong heterologous functional antibodies in small animals, but induced antibodies with limited cross-inhibitory functional activity in human clinical trials. These observations highlighted the need to establish new animal models that could better recapitulate human pathogenesis and immunity. In ongoing development of a nonhuman primate model for PM, we established an Aotus nancymaae model susceptible to P. falciparum infection during pregnancy that reproduces all the immunoparasitological and histological features of human PM. In this study, we explore the new Aotus model as a platform for evaluating PM vaccine (PMV) immunogenicity and for boosting of vaccine responses during PM episodes. Added value of this studyIn this manuscript, we demonstrate that PMV (including PAMVAC and PRIMVAC) are immunogenic in Aotus monkeys, inducing antibodies with mainly homologous and little heterologous functional activity, as seen in humans but contrary to preclinical reports on these vaccines in small animals. Implications of all the available evidenceOur findings suggest Aotus is a suitable model to assess immunogenicity of VAR2CSA-derived vaccines, in contrast to small animal models. PMV data from human trials and Aotus monkeys suggest that improvements to current VAR2CSA immunogens and/or adjuvants are needed to enhance protective antibody responses, as are studies that evaluate the potential for natural infection to boost vaccine antibody in pregnancy. Therefore, the Aotus PM model may be useful to assess second-generation PMVs seeking to increase strain-transcending activity and to prioritize these for further clinical development.

immunology↗

bioRxiv2021

A single full-length VAR2CSA ectodomain variant purifies broadly neutralizing antibodies against placental malaria isolates

Placental malaria (PM) is a deadly syndrome most frequent and severe in first pregnancies. PM results from accumulation of Plasmodium falciparum (Pf)-infected erythrocytes (IE) that express the surface antigen VAR2CSA and bind to chondroitin sulfate A (CSA) in the placenta. Women become PM-resistant over successive pregnancies as they develop anti-adhesion and anti-VAR2CSA antibodies, supporting VAR2CSA as the leading PM-vaccine candidate. However, the first VAR2CSA subunit vaccines failed to induce broadly neutralizing antibody and it is still unclear whether naturally acquired protective antibodies target variant or conserved epitopes. This is crucial to determine whether effective vaccines will require incorporation of many or only a single VAR2CSA allele. Here, IgG from multigravidae was sequentially purified on five full-length VAR2CSA ectodomain variants, thereby depleting IgG reactivity to each. The five VAR2CSA variants purified [~]0.7% of total IgG and yielded both strain-transcending and strain-specific reactivity to VAR2CSA and IE-surface antigen. IgG purified on the first VAR2CSA antigen displayed broad cross-reactivity to both recombinant and native VAR2CSA variants, and inhibited binding of all isolates to CSA. IgG remaining after depletion on all variants showed significantly reduced binding-inhibition activity compared to initial total IgG. These findings demonstrate that a single VAR2CSA ectodomain variant displays neutralizing epitopes shared by multiple parasites, including maternal isolates, and suggest that a broadly effective PM-vaccine can be achieved with a limited number of VAR2CSA variants.

immunology↗

bioRxiv2020

IFN-{lambda}4 increases the risk of gastrointestinal infections and malaria in Malian children

Genetic polymorphisms within the IFNL3/IFNL4 genomic region, which encodes type III interferons, have been strongly associated with impaired clearance of hepatitis C virus (HCV) infection. We hypothesized that type III interferons might be important for the immune response to other pathogens as well. In a cohort of 914 Malian children, we analyzed episodes of malaria, gastrointestinal and respiratory infections using information for 30,626 clinic visits from birth through up to 5 years of follow-up. Genetic polymorphisms IFNL4-rs368234815 and IFNL3-rs4803217 that functionally affect type III interferons were genotyped with TaqMan assays. For both genetic variants and each infection, we evaluated time-to-first episode and calculated odds ratios (ORs) for the risk of an infection episode during follow-up, controlling for relevant covariates. Compared to children with the rs368234815-TT/TT genotype (IFN-{lambda}4-Null), each copy of the rs368234815-dG allele was associated with an earlier first episode of a gastrointestinal infection (p=0.003) and respiratory infection (p=0.045). The risk of experiencing an infection episode during the follow-up was also significantly increased with each copy of the rs368234815-dG allele - for gastrointestinal infections (OR=1.53, 95%CI (1.13-2.07), p=0.005) and malaria (OR=1.30, 95%CI (1.02-1.65), p=0.033). IFNL4-rs368234815 and IFNL3-rs4803217 were in moderate linkage disequilibrium in this population (r2=0.78), and all the associations for rs4803217 were weaker and lost significance after adjusting for rs368234815, implicating IFN-{lambda}4 and not IFN-{lambda}3 as the primary cause of these associations. We conclude that the ability to produce IFN-{lambda}4 may have broad health-related implications by negatively affecting the immune response and clinical outcomes of several common infections.

genetics↗

bioRxiv2019

CXCR4 and MIF are required for neutrophil extracellular trap release triggered by Plasmodium-infected erythrocytes

Neutrophil extracellular traps (NETs) evolved as a unique effector mechanism contributing to resistance against infection that can also promote tissue damage in inflammatory conditions. Malaria infection can trigger NET release, but the mechanisms and consequences of NET formation in this context remain poorly characterized. Here we show, similarly to previous reports, that patients suffering from severe malaria had increased amounts of circulating DNA and increased neutrophil elastase (NE) levels in plasma. We used cultured erythrocytes and isolated human neutrophils to show that Plasmodium-infected red blood cells release MIF, which in turn caused NET formation by neutrophils in a mechanism dependent on the C-X-C chemokine receptor type 4 (CXCR4). NET production was dependent on histone citrulination by PAD4 and independent of reactive oxygen species (ROS), myeloperoxidase (MPO) or NE. In vitro, NETs functioned to restrain parasite dissemination in a mechanism dependent on MPO and NE activities. Finally, C57/B6 mice infected with P. berghei ANKA, a well-established model of cerebral malaria, presented high amounts of circulating DNA, while treatment with DNAse increased parasitemia and accelerated mortality, indicating a role for NETs in resistance against Plasmodium infection. Author summaryProtozoans of the Plasmodium genre infect red blood cells and cause malaria in humans and various other mammalian species. Estimated malaria cases are at more than 200 million, with 450,000 deaths per year, being cerebral malaria a serious complication that accounts for the majority of deaths. Neutrophils are cells that participate in host defense against pathogens. These cells use various mechanisms to kill invading microrganisms, including the release of webs of DNA, called neutrophil extracellular traps (NETs). These NETs can help control infections but can also induce tissue damage and their role in malaria and the mechanisms of NET production during malaria infection are starting to be understood. Here we show that infected red blood cells produce a cytokine, macrophage migration inhibitory factor (MIF) that stimulates neutrophils to release NETs. These NETs function to limit Plasmodium dissemination and, thus, digestion of NETs with DNAse treatment causes increased parasitemia and accelerated death in an experimental model of cerebral malaria. Our study uncovers the mechanism by which infected red blood cells stimulate neutrophils to release NETs and suggest an important participation of this process in malaria control.

immunology↗