Evaluation of pre-pandemic antibody response to Severe Acute Respiratory Syndrome Coronavirus-2 (SARs-CoV-2) IN Ugandan participants

Abstract

The COVID-19 severity rate in Sub-Saharan African countries such as Uganda has been surprisingly observed to be lower compared to elsewhere in the world. This may be attributed to prior exposure of the population to various coronaviruses which might have built substantial cross-reactive antibodies in the Ugandan pre-pandemic population against SARS-CoV-2. This was a cross-sectional study carried out to evaluate the antibody response of 50 serum samples collected between 2013 to 2015 before the COVID-19 pandemic period. The study was carried at UVRI/MRC/LSHTM Entebbe, Uganda which provided all the pre-COVID-19 serum samples, the necessary equipment for the examination and analysis of samples. Indirect ELISA Technique was used to screen for IgG antibodies against Nucleocapsid(N) and Spike(S) proteins of SARS-CoV-2, in the serum samples of the participants used in this study. A 30% proportion of the study population possessed cross-reactive antibodies against N- and 18% possessed antibodies against S-protein antigens. The positive cross-reactive response (in form of ODs) was observed to be higher against N-protein than that against S-protein. The median antibody responses of individuals against N-protein with Median 0.5380 (Interquartile range [IQR] 0.4153-0.8108) was higher than the median antibody responses in individuals against S-protein 0.2010 (IQR 0.1285 - 0.3510). There was a significant deviation between antibody responses for individuals against N-protein and S-protein (P<0.001). Therefore, cross-reactive antibodies were detected against both N- and S-proteins in the pre-pandemic population and these could be playing a role in reducing the severity of COVID-19 in Uganda.