Author(s):
Masood, Kiran Iqbal ; Qaiser, Shama ; Abidi, Syed Hani ; Khan, Erum ; Mahmood, Syed Faisal ; Hussain, Areeba ; Ghous, Zara ; Imtiaz, Khekahsan ; Ali, Natasha ; Hasan, Muhammad ; Memon, Haris Ali ; Yameen, Maliha ; Ali, Shiza ; Baloch, Sadaf ; Lakhani, Gulzar ; Alves, Paula M. ; Iqbal, Najeeha Talat ; Ahmed, Kumail ; Iqbal, Junaid ; Bhutta, Zulfiqar A. ; Hussain, Rabia ; Rottenberg, Martin ; Simas, J. Pedro ; Veldhoen, Marc ; Ghias, Kulsoom ; Hasan, Zahra
Date: 2023
Persistent ID: http://hdl.handle.net/10400.14/43333
Origin: Veritati - Repositório Institucional da Universidade Católica Portuguesa
Subject(s): IgG; Interferon-gamma; Receptor binding domain; SARS-CoV-2; Spike; T cells
Description
Background: Protection against SARS-CoV-2 is mediated by humoral and T cell responses. Pakistan faced relatively low morbidity and mortality from COVID-19 through the pandemic. To examine the role of prior immunity in the population, we studied IgG antibody response levels, virus neutralizing activity and T cell reactivity to Spike protein in a healthy control group (HG) as compared with COVID-19 cases and individuals from the pre-pandemic period (PP). Methods: HG and COVID-19 participants were recruited between October 2020 and May 2021. Pre-pandemic sera was collected before 2018. IgG antibodies against Spike and its Receptor Binding Domain (RBD) were determined by ELISA. Virus neutralization activity was determined using a PCR-based micro-neutralization assay. T cell – IFN-γ activation was assessed by ELISpot. Results: Overall, the magnitude of anti-Spike IgG antibody levels as well as seropositivity was greatest in COVID-19 cases (90%) as compared with HG (39.8%) and PP (12.2%). During the study period, Pakistan experienced three COVID-19 waves. We observed that IgG seropositivity to Spike in HG increased from 10.3 to 83.5% during the study, whilst seropositivity to RBD increased from 7.5 to 33.3%. IgG antibodies to Spike and RBD were correlated positively in all three study groups. Virus neutralizing activity was identified in sera of COVID-19, HG and PP. Spike reactive T cells were present in COVID-19, HG and PP groups. Individuals with reactive T cells included those with and without IgG antibodies to Spike. Conclusions: Antibody and T cell responses to Spike protein in individuals from the pre-pandemic period suggest prior immunity against SARS-CoV-2, most likely from cross-reactive responses. The rising seroprevalence observed in healthy individuals through the pandemic without known COVID-19 may be due to the activation of adaptive immunity from cross-reactive memory B and T cells. This may explain the more favourable COVID-19 outcomes observed in this population.
