These samples were excluded from the subsequent analysis to prevent the inclusion of non-specific signals.
HOW TO FIND SERUM SERIAL NUMBER PLUS
These samples had OD above 0.44, which corresponded to the mean plus 3 standard deviations (SD) of the Denmark group (Fig. 2/43, 4/121, 4/118, 30/146 and 1/12 samples from the Canada, Denmark, Brazil, Gabon and COVID-19 confirmed cases groups were positive for BSA-specific IgG. This study documents the presence of antibodies against SARS-CoV-2 N and S proteins in pre-pandemic sera (collected prior to November 2019) from individuals from various continents as well as the in vitro neutralization capacity and the in vivo protective efficacy of some of the sera with high antibody levels against SARS-CoV-2 N protein.įirst, IgG levels against BSA were analyzed. Among them, the N protein is highly conserved between coronavirus infected humans and animals, while the S protein is more genetically diverse 6, 9. Coronaviruses are also highly prevalent in wild animals, notably in bats viral nucleic acids have been detected from bats in Africa, Asia, America and Europe 7.ĭuring SARS-CoV-2 infections, the nucleocapsid (N) and spike (S) proteins are immune-dominant, with the great majority of the antibodies targeting these antigens 8. In contrast, human coronavirus (HCoV) 229E, OC43, NL-63 and HKU1 circulate worldwide in the human population (reviewed in 6). Severe acute respiratory syndrome coronavirus (SARS-CoV) caused a human outbreak between 20, while since 2012, frequent spill-over events of Middle East respiratory syndrome coronavirus (MERS-CoV) have led to sporadic human outbreaks in the Middle East. In addition to SARS-CoV-2, six coronaviruses are known to infect humans.
However, the initial delay in the emergence of the first COVID-19 cases, the strict quarantine/restriction measures put in place by African countries and lessons learned from previous outbreaks of emerging pathogens may have all contributed to the low number of COVID-19 cases reported in Africa 2, 5. Several seroprevalence studies conducted in African countries have suggested higher SARS-CoV-2 prevalence than expected based on confirmed case counts 3, 4.
Since then, various factors have been postulated to have contributed to the unexpectedly low numbers of reported cases of COVID-19 on the continent including high prevalence of mild symptomatic disease in a younger population and under-reporting associated with limited testing and health care capacity. The factors influencing the disparity in the spread of SARS-CoV-2 in various countries remain poorly understood.ĭue to the weak health system of a large number of African countries, initial models projected COVID-19 caseload and associated mortality of much higher magnitude on the African continent 2. More than 21 millions SARS-CoV-2 infections and 609,000 associated deaths have been reported in Brazil (, ). In contrast, South America and notably Brazil have been severely affected by the current pandemic. Surprisingly, only 151,000 of the 5 million COVID-19 related deaths have been reported on the African continent and, of those, the great majority (89,319 59%) have occurred in South Africa. As of July 2021, more than 249 million COVID-19 cases have been recorded worldwide, resulting in more than 3.9 million deaths. Since December 2019, SARS-CoV-2 has rapidly spread throughout the globe. The novel coronavirus, denoted severe acute respiratory syndrome (SARS) coronavirus (CoV) 2 (SARS-CoV-2), is the causative agent for the current coronavirus disease 2019 (COVID-19) pandemic 1. In Africa, seroprevalence studies using the N protein are over-estimating SARS-CoV-2 circulation. However, this pre-existing humoral immunity does not impact viral fitness in rodents suggesting that other human immune defense mechanisms could be involved. Overall, this study indicates that cross-reactive immunity against SARS-CoV-2 N protein was present in Africa prior to the pandemic. However, these antibodies failed to neutralize the virus either in vitro or in vivo. Antibodies against SARS-CoV-2 S and N proteins were rare in all populations except in Gabon and Senegal where N specific antibodies were prevalent. The protective efficacy of N specific antibodies isolated from Central African donors was tested by in vitro neutralization and in a mouse model of SARS-CoV-2 infection. In this study, the presence of antibodies against SARS-CoV-2 spike (S) and nucleocapsid (N) proteins in pre-pandemic samples from Africa, Europe, South and North America was examined by ELISA. However, the contribution of pre-existing immunity is yet to be investigated. Various hypotheses were postulated to explain the lower than anticipated impact on public health in Africa. To date, Africa has been relatively spared. Early predictions forecasted large numbers of severe acute respiratory syndrome coronavirus (SARS-CoV-2) cases and associated deaths in Africa.