Antibody seropositivity in Central Africa and preliminary molecular determinants in the inflammatory pathogenesis of SARS-CoV-2

The majority of the world's human population has been susceptible to SARS-CoV-2 infection. Central and sub-Saharan Africa are among the regions with high seroprevalence despite low reported infection rates. In antiviral process, there is a complex network of interaction between the virus and infected host cells, in which microRNAs have been revealed to play an important role. This study aimed to assess anti-SARS-CoV-2 immunity in the Central African context and to explore the potential uses of microRNAs as molecular determinants in the inflammatory pathogenesis of SARS-CoV-2. Chad: Between August and October 2021, eleven hospitals of the N’Djamena were mobilised for data and sample collection from out-patients. An enzyme-linked immunodiagnostic technique was used to identify IgG antibodies against nucleocapsid protein of SARS-CoV-2. In addition, a pool of 100 samples was analysed for neutralizing antibodies (NAbs) against spike protein and anti-receptor binding domain (RBD) protein with a chemiluminescence immunoassay and VSV pseudo-neutralization test. Overall, 2,700 samples were collected and analyzed, the average age of participants was 31.9±12.6 years, with the most represented group being 25-34-year-olds (35.2%). Women represented 56.4% of the study population making the ratio women/men 1.3. Participants from the 7th district (22.5%) and the 1st district (22.3%) of N’Djamena were the most numerous. Concerning professions, the most represented were housewives (29.1%) and students (27.2%). The overall reported anti-nucleocapsid (anti-N) seroprevalence was 69.5% (95% CI 67.7-71.3), being 68.2% (95% CI: 65.8-70.5) in the female group and 71.2% (95% CI: 68.6 -73.8) in the male group. The most sensitized age group was >44 years with a seroprevalence rate of 73.9%. Participants under 15 years of age had the lowest positivity rate of 57.4%. The most sensitized socio-professional categories were civil servants 71.5% followed by housewives 70.9%, health personnel (which constituted 9.7% of the respondents) had 67.8% of positivity rate. Antibody detection by neutralization test indicated that, out of 100 samples tested, 59.0% were positive for NAbs and simultaneously anti-RBD were detected. For total antibodies anti-spike (anti-S), 58.0% of samples tested showed the simultaneous presence of anti-S and NAbs. However, 23.0% of samples were positive for anti-RBD and negative for NAbs, while 34.0% of anti-S positive samples were negative for NAbs. Considering only NAbs negative plasma samples, 56.1% (n=23/41) were positive for anti-RBD and 82.9% (n=34/41) were positive for total anti-S. Cameroon: A cross-sectional study performed in December 2020 and December 2021 among students and staffs of the Evangelical University of Cameroon (UEC), in Bandjoun, Cameroon. Covid-19 SD biosensor antigen rapid detection test (RDT) was performed using Standard Q Biosensor and, a year later, SARS-CoV-2 antibody-test was performed within the same population using another RDT for the detection of nucleocapsid antibodies (IgG and IgM) and chemiluminescence immunoassay (CLIA) for anti-N and anti-S detection. A total of 106 participants were enrolled (80% students), female sex was the most represented. Positivity to SARS-CoV-2 was 0% based on antigen RDTs. The seroprevalence of SARS-CoV 2 anti-nucleocapsid antibodies was estimated at 73.6% (95% CI. 64.5-81.0) for IgG and 1.9% (95% CI. 0.2-6.8) for IgM/IgG with RDTs; and 91.9% (95% CI. 84.7-96.4) for anti nucleocapsid and 95.9% (95% CI. 90.1-98.4) for anti-Spike using CLIA. Among the participants 95.3% (n=101) reported having developed at least one of the known Covid-19 symptoms (cough and headache being the most common). The 26.4% (n=28) of people who experienced at least one of these symptoms showed IgG antibodies against SARS-CoV-2. Concerning treatments, 40.6% (n=43) of participants took natural herbs, whereas 55.7% (n=59) took conventional drugs. The most used herb was Zingiber officinale, while the most used drugs were antibiotics. When the results of the LFIA and CLIA methods were combined, the data suggest that 79.8% had total anti-N antibodies (CLIA) and IgG antibodies (LFIA) and 78.0% of participants were positive for anti-S and IgG (LFIA). Considering all three methods simultaneously, 80.9% of patients were positive for anti-S, anti-N and IgG. Italy: This part of the study was initiated at the beginning of the pandemic, knowing the associated role of miRs in the regulation of inflammatory markers. Thus, twelve microRNAs (miRs 21, 146b, 155, 92, 142-3p, 122a, 181a, 125b, 17, let7i, 146a, 126) were selected based on the results of different published studies. 16 COVID-19 positive consenting patients were recruited for this study at the Policlinico Tor Vergata (PTV) in Rome. RNA was isolated from plasma and cDNAs were used to perform the real-time PCR assays. Evaluation of expression of these 12 inflamma-miRs showed a variable level of expression of these circulating miRs, as well as the correlation between the expression of some of them and inflammatory biomarkers. Our results indicated that ten inflammatory miRs (miR-92, miR-21, miR-215b, miR-155, miR-181a, miR-126, miR-17, miR-146a, let-7i and miR-146b) were significantly down-regulated, while miR-142-3p did not show significant difference with healthy donors. Circulating levels of miR-122a was directly and significantly correlated with TNF alpha expression, as well as it was miR-142-3p with IL-6. An inverse correlation was observed between the expression of miR-92, miR-181a, miR-25b, miR-155, miR-26 and the blood expression of lactate dehydrogenase. Bioinformatic prediction indicated that the plant conserved miR394, mtr-miR5557, ath miRf10305-akr, ptc-miRf12256-akr families, as well as the novel ginger miRs (novel miRNA26 and miRNA105), had functional homology for miR-92, miR-21, miR-155, miR 125b, let-7i-3 respectively (overall score ranging from 50-65.4%, seed_score 62.5-81.3% and significant P-values). The African epidemiological studies clearly indicate that SARS-CoV-2 has circulated intensively in the African community, despite the low mortality and morbidity reported, compared to the other continent. This could be correlated to the fact that most Africans have manifested less severe or asymptomatic forms of Covid-19. Several hypotheses have been proposed to understand this potential paradox. In view of our findings on the expression of inflammatory-microRNAs, the hypothesis for the future is that African anti-inflammatory plants, which are used by this population on a daily basis and as a means of prevention during the pandemic, could contribute, through cross-kingdom activity, to the protection of the African population against severe forms of Covid-19.