Biology subjects

Vigan-Womas, I.

Publications and source records attributed to Vigan-Womas, I..

3 recordsLinked to original sources

bioRxiv2025

Differential association of SARS-CoV-2 IgG responses with anti-OC43 IgG in a Senegalese cohort

Numerous studies elucidated the kinetics of the humoral immune response post-SARS-CoV-2 infection. However, in sub-Saharan Africa, the evolution of SARS-CoV-2 IgG antibody responses and their interaction with pre-existing seasonal human coronavirus (HCoVs: OC43, 229E, NL63, HKU1) immunity remain underexplored. A prospective cohort study was conducted in Senegal during the first year of the COVID-19 pandemic (March to December 2020). A total of 204 patients with laboratory-confirmed COVID-19 were included. Patients were classified as symptomatic (n=157) or asymptomatic (n=47) based on clinical presentation. Plasma samples (n=705) were collected over 6 months from SARS-CoV-2 positive individuals. IgG levels against SARS-CoV-2 and HCoVs were measured using a multiplex bead-based assay. Among the 204 participants included (95 [46.6%] female, median age, 44 [7-95]), SARS-CoV-2 IgG were detectable 6 months post-infection, peaking at 1 month for most antigens, except for Spike (S), which peaked at 3 months. Elderly patients (>60 years) exhibited higher IgG levels against both SARS- CoV-2 and HCoVs. Symptomatic patients had higher IgG levels than asymptomatic individuals, especially for WTS, RBD, S2, and N. Anti-HCoV IgG levels remained stable post-infection, with OC43 peaking at week 3 in symptomatic patients. A positive correlation was found between anti-SARS-CoV- 2 and anti-OC43 IgG in symptomatic patients. The study highlights persistent SARS-CoV-2 IgG antibodies for up to 6 months and suggests a link between pre-existing HCoV-OC43 immunity and COVID-19 outcomes in Senegal. These findings could help shape future vaccine strategies, considering the influence of circulating HCoVs on long- term protection against SARS-CoV-2. Author summaryUnderstanding how our immune system responds to SARS-CoV-2, the virus responsible for COVID- 19, is essential for guiding public health countermeasures and informing vaccine development strategies. In our study, we monitored, in COVID-19 patients, the evolution of IgG antibody responses against SARS-CoV-2 structural proteins over a six-month period. Additionally, we examined how previous exposure to common seasonal coronaviruses might influence immune responses to SARS-CoV-2. Conducting this research in an African context is particularly important, as data on immune responses to SARS-CoV-2 in this region are scarce. Our results provide valuable insights into the complex interplay between immune responses elicited by SARS-CoV-2 and pre-existing immunity from seasonal circulating coronaviruses. These findings enhance our understanding of immune memory and cross-reactivity, two critical factors for assessing long-term protection and optimizing vaccine strategies. By shedding light on the dynamics of antibody responses over time within a sub-Saharan population, our research contributes to the global effort aimed at developing effective interventions against COVID-19 and preparing for future coronavirus outbreaks.

immunology↗

bioRxiv2019

Differential contribution of Anopheles coustani and Anopheles arabiensis to the transmission of Plasmodium falciparum and Plasmodium vivax in two neighboring villages of Madagascar

BackgroundMalaria is still a heavy public health concern in Madagascar. Few studies combining parasitology and entomology have been recently conducted despite the need for such information to design proper vector control measures. In a region of moderate to intense transmission of both Plasmodium falciparum and Plasmodium vivax, we conducted a combined parasitology and entomology survey in two nearby villages, across a malaria transmission season from December 2016 to April 2017.\n\nMethodology/Principal findingsCommunity-based surveys were conducted in the two close by villages at three time points during a single malaria transmission season. Plasmodium carriage in the human populations was determined by Rapid Diagnostic Tests (RDTs), microscopy and real-time PCR. Anthropophilic mosquitoes were captured by human landing captures and presence of Plasmodium sporozoites was assessed by robust Real Time PCR. Overall human malaria prevalence was 8.0% by RDT, 4.8% by microscopy and 11.9% by PCR, mainly due to P. falciparum detected in 92.2% of the PCR positive samples and Plasmodium vivax (5.7%). No significant differences in Plasmodium human carriage was observed between the 2 villages at any time point. Of the 1553 anopheline mosquitoes tested, 13 were found carrying Plasmodium sporozoites, the majority of them being captured outdoor. The mosquito sporozoite indices were not significantly different between the two villages. However, our entomological analysis revealed that Anopheles coustani was the main vector in one village, being responsible of 25.5 infective bites during the whole survey, whereas it was Anopheles arabiensis in the other village with 15 infective bites. In addition, we found a significant higher number of endophagic An. coustani and An. arabiensis in one village compared to the other.\n\nConclusions/SignificanceDespite similar human malaria prevalence in two close by villages, the entomological survey demonstrated the contribution of two different mosquito species in each village, and importantly the role of a suspected secondary malaria vector, An. coustani, as the main vector in one village. This, along with its higher endophagic rate in that village, highlights the importance of combining parasitology and entomology surveys for better targeting the actual local malaria vector. Such study should contribute to the malaria pre-elimination goal established under the 2018-2022 National Malaria Strategic Plan.\n\nAuthor SummaryMalaria is still a major health concern in many countries in sub-Saharan Africa such as Madagascar. In this study, we determined the contribution of malaria vectors in the transmission of Plasmodium parasites in two nearby villages in an area of moderate to high malaria transmission in Madagascar. We collected, during a single malaria transmission season, parasitological data in the human population and entomological data in the mosquito population, in order to evaluate Plasmodium carriage in these two populations. The results showed that despite similarity in human malaria prevalence and in vector species diversity in each village, the contribution of vectors was different between the two villages. An. arabiensis was the major vector in Ambohitromby while it was An. coustani that played this role in Miarinarivo. Importantly, this study is the first that clearly demonstrates that An. coustani could act as a major local vector in Madagascar. Such study should help deploying adapted malaria vector control and contributing to the malaria pre-elimination goal established under the 2018-2022 National Malaria Strategic Plan.

microbiology↗

bioRxiv2018

Genetic diversity in two Plasmodium vivax protein ligands for reticulocyte invasion

The interaction between Plasmodium vivax Duffy binding protein (PvDBP) and Duffy antigen receptor for chemokines (DARC) has been described as critical for the invasion of human reticulocytes, although increasing reports of P. vivax infections in Duffy-negative individuals questions its unique role. To investigate the genetic diversity of the two main protein ligands for reticulocyte invasion, PvDBP and P. vivax Erythrocyte Binding Protein (PvEBP), we analyzed 458 isolates collected in Cambodia and Madagascar. First, we observed a high proportion of isolates with multiple copies PvEBP from Madagascar (56%) where Duffy negative and positive individuals coexist compared to Cambodia (19%) where Duffy-negative population is virtually absent. Whether the gene amplification observed is responsible for alternate invasion pathways remains to be tested. Second, we found that the PvEBP gene was less diverse than PvDBP gene (12 vs. 33 alleles) but provided evidence for an excess of nonsynonymous mutations with the complete absence of synonymous mutations. This finding reveals that PvEBP is under strong diversifying selection, and confirms the importance of this protein ligand in the invasion process of the human reticulocytes and as a target of acquired immunity. These observations highlight how genomic changes in parasite ligands improve the fitness of P. vivax isolates in the face of immune pressure and receptor polymorphisms.

genetics↗