Journal Article

Lower Humoral and Cellular Immunity Following Asymptomatic SARS-CoV-2 Infection Compared to Symptomatic Infection in Education (The ACE Cohort)

Somerville, Michelle, Fairclough, Lucy, Burns, Ellie, Potts, Martin, Gomez, Nancy, Metaxaki, Marina, Godkin, Andrew, Tighe, Paddy, Harvey-Cowlishaw, Tyler, Steers, Graham, Scurr, Martin, Gallimore, Awen, Bartlett, Laura, Lauder, Sarah N, Jackson, Hannah, Onion, David, Hopkins, Georgina, Tucis, Davis, Brown, Michaela, Smart, Kathryn, Krishna, Benjamin, Rees, Tara, Perera, Marianne, Wills, Mark, Santos, Rute, Capitani, Lorenzo, Burnell, Stephanie

2024

Overview

PurposeAsymptomatic SARS-CoV-2 infections were widely reported during the COVID-19 pandemic, acting as a hidden source of infection. Many existing studies investigating asymptomatic immunity failed to recruit true asymptomatic individuals. Thus, we conducted a longitudinal cohort study to evaluate humoral- and cell-mediated responses to infection and vaccination in well-defined asymptomatic young adults (the Asymptomatic COVID-19 in Education [ACE] cohort).MethodsAsymptomatic testing services located at three UK universities identified asymptomatic young adults who were subsequently recruited with age- and sex-matched symptomatic and uninfected controls. Blood and saliva samples were collected after SARS-CoV-2 Wuhan infection, and again after vaccination. 51 participant’s anti-spike antibody titres, neutralizing antibodies, and spike-specific T-cell responses were measured, against both Wuhan and Omicron B.1.1.529.1.ResultsAsymptomatic participants exhibited reduced Wuhan-specific neutralization antibodies pre- and post-vaccination, as well as fewer Omicron-specific neutralization antibodies post-vaccination, compared to symptomatic participants. Lower Wuhan and Omicron-specific IgG titres in asymptomatic individuals were also observed pre- and post-vaccination, compared to symptomatic participants. There were no differences in salivary IgA levels. Conventional flow cytometry analysis and multi-dimensional clustering analysis indicated unvaccinated asymptomatic participants had significantly fewer Wuhan-specific IL-2 secreting CD4+ CD45RA+ T cells and activated CD8+ T cells than symptomatic participants, though these differences dissipated after vaccination.ConclusionsAsymptomatic infection results in decreased antibody and T cell responses to further exposure to SARS-CoV-2 variants, compared to symptomatic infection. Post-vaccination, antibody responses are still inferior, but T cell immunity increases to match symptomatic subjects, emphasising the importance of vaccination to help protect asymptomatic individuals against future variants.

• Publisher: Springer Nature B.V
• Subject: Antibodies / Asymptomatic / Asymptomatic infection / CD4 antigen / CD45RA antigen / CD8 antigen / Cell-mediated immunity / COVID-19 / COVID-19 vaccines / Flow cytometry / Humoral immunity / Immunoglobulin A / Immunoglobulin G / Infections / Lymphocytes T / Saliva / Severe acute respiratory syndrome coronavirus 2 / Vaccination / Young adults