Snapshot of Anti-SARS-CoV-2 IgG Antibodies in COVID-19 Recovered Patients in Guinea.

Background: Because the regular vaccine campaign started in Guinea one year after the COVID-19 index case, the profile of naturally acquired immunity following primary SARS-CoV-2 infection needs to be deepened. Methods: Blood samples were collected once from 200 patients (90% of African extraction) who were recovered from COVID-19 for at least ~2.4 months (72 days), and their sera were tested for IgG antibodies to SARS-CoV-2 using an in-house ELISA assay against the Receptor Binding Domain (RBD) of the SARS-CoV-2 spike1 protein (RBD/S1-IH kit). Results: Results revealed that 73% of sera (146/200) were positive for IgG to SARS-CoV-2 with an Optical Density (OD) ranging from 0.13 to 1.19 and a median value of 0.56 (IC95: 0.51-0.61). The median OD value at 3 months (1.040) suddenly decreased thereafter and remained stable around OD 0.5 until 15 months post-infection. The OD median value was slightly higher in males compared to females (0.62 vs. 0.49), but the difference was not statistically significant (p-value: 0.073). In contrast, the OD median value was significantly higher among the 60-100 age group (0.87) compared to other groups, with a noteworthy odds ratio compared to the 0-20 age group (OR: 9.69, p-value: 0.044*). Results from the RBD/S1-IH ELISA kit demonstrated superior concordance with the whole spike1 protein ELISA commercial kit compared to a nucleoprotein ELISA commercial kit. Furthermore, anti-spike1 protein ELISAs (whole spike1 and RBD/S1) revealed higher seropositivity rates. Conclusions: These findings underscore the necessity for additional insights into naturally acquired immunity against COVID-19 and emphasize the relevance of specific ELISA kits for accurate seropositivity rates.

Assessing One Health capacities for transboundary zoonotic diseases at the Libya-Tunisia border.

BACKGROUND: The dynamic nature of zoonotic emergence, spillover and spread necessitates multisectoral coordination beyond national borders to encompass cross-boundary and regional cooperation. Designated points of entry (POEs), specifically ground crossings, serve as critical locales for establishing and maintaining robust prevention, detection, notification, coordination, and response mechanisms to transboundary emerging and re-emerging disease threats. In order to better assess One Health capacities for transboundary zoonotic diseases (TZD) prevention, detection and response we adapted an existing tool, One Health Systems Assessment for Priority Zoonoses (OHSAPZ), for a cross-border, POE setting in North Africa. METHODS: The One Health Transboundary Assessment for Priority Zoonoses (OHTAPZ) tool was used to support prioritization of transboundary zoonoses and analyze operational capacities between national and subnational-level human and animal health stakeholders from Libya and Tunisia. Country partners jointly identified and prioritized five TZDs of concern. Case study scenarios for each priority pathogen were used to elicit current disease operations, as well as multisectoral and bilateral engagement networks. Finally, a gap analysis was performed to determine bilateral strengths and weaknesses to TZDs. RESULTS: The five priority TZDs jointly confirmed to undergo One Health assessment were avian influenza (low and high pathogenic strains); brucellosis; Rift Valley fever; Crimean-Congo hemorrhagic fever; and rabies. Using the qualitative information collected, a transboundary systems map schematic was developed outlining the movement of human patients, animals, diagnostic samples, and routes of communication and coordination both within and between countries for zoonotic diseases. CONCLUSIONS: Analysis of current operations (prevention, detection, surveillance, laboratory capacity, quarantine/isolation, and response) and the resulting transboundary systems map schematic helped identify existing capacity strengths for certain priority pathogens, as well as challenges to timely information-sharing and coordination. We developed targeted recommendations to address these limitations for joint action planning between Libya and Tunisia.

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

Management 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.

Culture filtrate protein 32 as a potential target to attenuate the heterogeneous antibody response against Mycobacterium tuberculosis Antigens in different endemic settings.

Background: We previously reported the development of an enzyme-linked immunosorbent assay for the detection of the immunoglobulin G (IgG) response to Mycobacterium tuberculosis virulence factor - culture filtrate protein 32 (CFP32). The assay achieved high performance in comparing healthy Bacillus Calmette-Guerin-vaccinated controls with active tuberculosis (TB) patients from the Tunisian population. Herein, we aimed to assess the anti-CFP32 IgG response in suspected or confirmed active pulmonary TB individuals in different endemic settings. Methods: Serum samples were obtained from 224 donors from African and Latin American countries with variable levels of TB endemicity and different ethnical origins. Receiver operating characteristic curve was used to evaluate the performance of the serological assay. Results: The area under the curve was 0.70. The use of a cutoff level of 0.65 gave 67% and 68% sensitivity and specificity, respectively, regardless of ethnicity and endemicity. Except for the suspected Latin American group, overall multiple comparisons of medians pointed out the stability of the anti-CFP32 IgG response across the different endemic settings. Therefore, endemicity and ethnicity seem not to affect anti-CFP32 IgG response, mainly for detecting confirmed active TB individuals. Conclusions: These findings suggest that the inclusion of CFP32 epitopes in multi-antigen TB assay could attenuate serological differences related to heterogeneous endemicity and ethnicity. For this purpose, we further identified B-cell epitopes belonging to CFP32 by an in silico analysis.