Linear epitope mapping of the humoral response against SARS-CoV-2 in two independent African cohorts

Abstract Profiling of the antibody responses to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) proteins in African populations is scarce. Here, we performed a detailed IgM and IgG epitope mapping study against 487 peptides covering SARS-CoV-2 wild-type structural proteins. A panel of 41 pre-pandemic and 82 COVID-19 RT-PCR confirmed sera from Madagascar and Senegal were used. We found that the main 36 immunodominant linear epitopes identified were (i) similar in both countries, (ii) distributed mainly in the Spike and the Nucleocapsid proteins, (iii) located outside the RBD and NTD regions where most of the reported SARS-CoV-2 variant mutations occur, and (iv) identical to those reported in European, North American, and Asian studies. Within the severe group, antibody levels were inversely correlated with the viral load. This first antibody epitope mapping study performed in patients from two African countries may be helpful to guide rational peptide-based diagnostic assays or vaccine development

Seroprevalence of anti-SARS-CoV-2 antibodies in Senegal: a national population-based cross-sectional survey, between October and November 2020

Posté le 17 septembre 2021.International audienceObjectivesA nationwide cross-sectional epidemiological survey was conducted to capture the true extent of coronavirus disease 2019 (COVID-19) exposure in Senegal.MethodsMulti-stage random cluster sampling of households was performed between October and November 2020, at the end of the first wave of COVID-19 transmission. Anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies were screened using three distinct ELISA assays. Adjusted prevalence rates for the survey design were calculated for each test separately, and thereafter combined. Crude and adjusted prevalence rates based on test performance were estimated to assess the seroprevalence. As some samples were collected in high malaria endemic areas, the relationship between SARS-CoV-2 seroreactivity and antimalarial humoral immunity was also investigated.ResultsOf the 1463 participants included in this study, 58.8% were female and 41.2% were male; their mean age was 29.2 years (range 0.20–84.8.0 years). The national seroprevalence was estimated at 28.4% (95% confidence interval 26.1–30.8%). There was substantial regional variability. All age groups were impacted, and the prevalence of SARS-CoV-2 was comparable in the symptomatic and asymptomatic groups. An estimated 4 744 392 (95% confidence interval 4 360 164–5 145 327) were potentially infected with SARS-CoV-2 in Senegal, while 16 089 COVID-19 RT-PCR laboratory-confirmed cases were reported by the national surveillance. No correlation was found between SARS-CoV-2 and Plasmodium seroreactivity.ConclusionsThese results provide a better estimate of SARS-CoV-2 dissemination in the Senegalese population. Preventive and control measures need to be reinforced in the country and especially in the south border regions

Seroprevalence of anti-SARS-CoV-2 antibodies in Senegal: a national population-based cross-sectional survey, between October and November 2020

Posté le 17 septembre 2021.Background: Senegal reported the first COVID-19 case on March 2, 2020. A nationwide cross-sectional epidemiological survey was conducted to capture the true extent of COVID-19 exposure.Methods: Multi-stage random cluster sampling of households was carried out between October 24 and November 26, 2020, at the end of the first wave of COVID-19 transmission. Anti-SARS-CoV-2 antibodies (IgG and/or IgM) were screened using three distinct ELISA assays. Adjusted prevalence for the survey design were calculated for each test separately, and thereafter combined. Crude, adjusted prevalence based on tests performances and weighted prevalence by sex-age strata were estimated to assess the seroprevalence.Findings: Of the 1,463 participants included in this study, 58·8% were women and the mean age of participants was 29·2 years (range 0·25–82·0). The national seroprevalence was estimated at 28 . 4% (95% CI: 26·1-30·8). There was substantial regional variability. Four regions recorded the highest seroprevalence: Ziguinchor (56·7%), Sedhiou (48·0%), Dakar (44·0%) and Kaolack (32·7%) whereas, Louga (11·1%) and Matam (11·2%), located in the Center-North, were less impacted in our analysis. All age groups were impacted and the prevalence of SARS-CoV-2 was comparable in symptomatic and asymptomatic groups. We estimated 4,744,392 SARS-CoV-2 (95% CI: 4,360,164 – 5,145,327) potential infected in Senegal compared to 16,089 COVID-19 RT-PCR laboratory-confirmed cases reported at the time of the survey.Interpretation: These results provide an estimate of SARS-CoV-2 virus dissemination in the Senegalese population. Preventive and control measures need to be reinforced in the country and especially in the south border regions

Development and comparative evaluation of SARS-CoV-2 S-RBD and N based ELISA tests in various African endemic settings

International audienceManagement of the COVID-19 pandemic relies on molecular diagnostic methods supported by serological tools. Herein, we developed S-RBD- and N- based ELISA assays useful for infection rate surveillance as well as the follow-up of acquired protective immunity against SARS-CoV-2. ELISA assays were optimized using COVID-19 Tunisian patients' sera and prepandemic controls. Assays were further validated in 3 African countries with variable endemic settings. The receiver operating curve was used to evaluate the assay performances. The N- and S-RBD-based ELISA assays performances, in Tunisia, were very high (AUC: 0.966 and 0.98, respectively, p < 0.0001). Cross-validation analysis showed similar performances in different settings. Cross-reactivity, with malaria infection, against viral antigens, was noticed. In head-to-head comparisons with different commercial assays, the developed assays showed high agreement. This study demonstrates, the added value of the developed serological assays in low-income countries, particularly in ethnically diverse populations with variable exposure to local endemic infectious diseases