Pelleau, S. | bioRxiv Science

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↗

bioRxiv2024

Temporal patterns of haplotypic and allelic diversity reflect the changing selection landscape of the malaria parasite Plasmodium falciparum

Populations of the malaria parasite Plasmodium falciparum regularly confront orchestrated changes in frontline drug treatment that drastically alter the parasites selection landscape. When this has occurred, the parasite has successfully adapted to the new drugs through novel resistance mutations. These novel mutations, however, may emerge in a genetic background already shaped by prior drug selection. In some instances, selection imposed by distinct drugs has targeted the same loci in either synergistic or antagonistic ways, resulting in genomic signatures that can be hard to attribute to a specific agent. Here, we use two approaches for detecting sequential bouts of drug adaptation: haplotype-based selection testing and temporal changes in allele frequencies. Using a set of longitudinally acquired samples from French Guiana, we determine that since the introduction of the drug artemether-lumefantrine (AL) in 2007 there have been rapid hard selective sweeps at both known and novel loci. We additionally identify genomic regions where selection acted in opposing directions before and after widespread AL introduction. At four high-profile genes with demonstrated involvement in drug resistance (crt, mdr1, aat1, and gch1), we saw strong selection before and after drug regime change; however, selection favored different haplotypes in the two time periods. Similarly, the allele frequency analysis identified coding variants whose frequency trajectory changed sign under the new drug pressure. These selected alleles were enriched for genes implicated in artemisinin and/or partner drug resistance in other global populations. Overall, these results suggest that drug resistance in P. falciparum is governed by known alleles of large effect along with a polygenic architecture of more subtle variants, any of which can experience fitness reversals under distinct drug regimes.

genomics↗