High SARS-CoV-2 seroprevalence in Lagos, Nigeria with robust antibody and cellular responses

Abstract

Background Early evidence suggested that the impact of the COVID-19 pandemic was less severe in Africa compared to other parts of the world. However, more recent studies indicate higher SARS-CoV-2 infection and COVID-19 mortality rates on the continent than previously documented. Research is needed to better understand SARS-CoV-2 seroprevalence and immunity in Africa. Methods Our collaboration with the Lagos State COVID-19 Taskforce, enabled secondary analyses of immune responses in healthcare workers (HCWs) and Oxford/AstraZeneca COVID-19 vaccine recipients from the general population across 5 local government areas (LGAs) in Lagos State, Nigeria. Western blots were used to simultaneously detect SARS-CoV-2 spike and nucleocapsid (N) antibodies and stimulation of peripheral blood mononuclear cells with N followed by an IFN-γ ELISA was used to examine T cell responses. Findings Antibody data demonstrated high SARS-CoV-2 seroprevalence of 71.6% (96/134) in HCWs and 54.8% (63/115) in the general population. Antibodies directed to only SARS-CoV-2 N, suggesting pre-existing coronavirus immunity, were seen in 10.4% (14/134) of HCWs and 20.0% (23/115) of the general population. T cell data showed that IFN-γ responses against SARS-CoV-2 N were robust in detecting exposure to the virus, demonstrating 87.5% sensitivity and 92.3% specificity. Interpretation These results have important implications for understanding the paradoxical high SARS-CoV-2 infection with low mortality rate in Africa as compared to other parts of the world, as well as for the development of T cell-based diagnostics and vaccines.

West African pre-pandemic cross-reactive antibody and cellular responses against SARS-CoV-2

“…In early 2021, we studied the immune responses in Nigerian healthcare workers (HCWs) at Lagos University Teaching Hospital (n=134) and in Oxford/AstraZeneca COVID-19 vaccine recipients from the general population (n=116) across five local government areas (LGAs) in Lagos state. 5 Antibodies directed to only SARS-CoV-2 N in the absence of S antibody reactivity were detected in 9.7% (13/134) of HCWs and 15.5% (18/116) of the general population. This antibody profile directed to the SARS-CoV-2 N alone was suggestive of pre-existing cross-reactive immunity stemming from prior hCoV infection.…”

“…1-2). 5,26 In one of the few studies conducted on samples from Africa prior to the COVID-19 pandemic, Tso et al reported higher reactivity to hCoV N and S antigens with significantly higher rates of cross-reactivity in Zambia (14.1%) and Tanzania (19%) compared to the US (2.4%). 27 In a multi-national study, Pedersen et al reported higher SARS-CoV-2 N reactivity in Gabon (20/116,17.2%) compared to reactivity in Canada, Denmark, and Brazil.…”

“…Multiple US and European studies described CD4+ T cell reactivity in SARS-CoV-2 unexposed individuals, attributed to pre-existing memory responses to hCoVs. [3][4][5][6][7] In a UK household study, exposed contacts that remained PCR-negative showed significantly higher frequency of crossreactive (p=.0139) and nucleocapsid (N)-specific IL-2 secreting memory T cells (p=.0355). 3 Swadling et al in a study of potentially abortive SARS-CoV-2 infection in UK healthcare workers (HCWs) described pre-existing T cell reactivity directed against the early transcribed replication-transcription complex (RTC).…”

“…4 Studies of pre-pandemic samples collected from Africa have also demonstrated cross-reactive T cell responses against several SARS-CoV-2 antigens. 5,6 These studies have led to the hypothesis that prior hCoV infection might provide protective cross-reactive memory, perhaps more likely in younger individuals in whom infections with hCoVs are more prevalent and recent. As described by Lipsitch et al, pre-existing cross-reactive memory T cells could lower respiratory tract viral load thereby limiting the duration and severity of disease with potential to reduce viral spread.…”

High pre‐Delta and early‐Omicron SARS‐CoV‐2 seroprevalence detected in dried blood samples from Kinshasa (D.R. Congo)

“…In contrast, studies in the DRC have found seroprevalences ranging from 48% 12 to 70% 13,14 . A similar phenomenon has occurred in neighboring countries such as Republic of the Congo, 15 Cameroon, 16 Gambia, 17 Somalia, 18 Uganda, 12,14,19 Tanzania, 20 Nigeria 12,21,22 and Kenya, 23–25 where growing evidence indicates pandemic burden has been grossly underestimated.…”