A longitudinal study of antibody responses to endemic HCoV and novel SARS-CoV-2 among mother-child pairs in Zambia

Background: Seroprevalence estimates of endemic human coronaviruses (HCoV) and novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are limited in Zambia. Information on development of acquired immunity to endemic HCoV in early life is also scarce and the potential cross-protective effect of HCoV immunity on SARS-CoV-2 remains debatable. We investigated seroprevalence of endemic HCoV in mother-child dyads and SARS-CoV-2 in children and explored the association between HCoV and SARS-CoV-2 antibodies in children to elucidate coronavirus seroepidemiology in Zambia. Methods: We measured endemic HCoV NL63, 229E, OC43 and HKU1 and SARS-CoV-2 Spike protein subunit 1 (S1) specific immunoglobulin G (IgG) using an immunoassay. We tested plasma samples collected from Zambian mother-child dyads before the coronavirus disease 2019 pandemic in 2018 and 2019, and during the pandemic in 2020 and 2021. We determined HCoV S1 IgG seropositivity in mothers and children and SARS-CoV-2 S1 IgG seropositivity in children. We correlated HCoV antibodies in the mother-child pairs and longitudinally profiled HCoV antibodies in children to investigate development of HCoV immunity and contribution of maternal immunity. We compared child HCoV S1 IgG and SARS-CoV-2 S1 IgG antibodies before and during the pandemic to explore cross-reactivity. Results: HCoV and SARS-CoV-2 S1 IgG antibodies were detected among mothers and children. Child HCoV seroconversion occurred following waning of maternal immunity but there was no significant correlation between HCoV and SARS-CoV-2 S1 IgG before and during the pandemic. A rise in SARS-CoV-2 S1 IgG seroprevalence among children was observed following the second and third epidemic waves of the COVID-19 pandemic in Zambia. Conclusions: Endemic HCoV NL63, 229E, OC43 and HKU1 widely circulated and are acquired early in Zambia. SARS-CoV-2 seroprevalence in children speaks to the susceptibility of this population to infection that necessitates their inclusion in control measures.