The presence of serum anti‐SARS‐CoV‐2 IgA appears to protect primary health care workers from COVID‐19

Abstract

The patterns of humoral and cellular responses to SARS-CoV-2 were studied in Swedish primary health care workers (n = 156) for 6 months during the Covid-19 pandemic. Serum IgA and IgG to SARS-CoV-2, T-cell proliferation and cytokine secretion, demographic and clinical data, PCR-verified infection, and self-reported symptoms were monitored. The multivariate method OPLS-DA was used to identify immune response patterns coupled to protection from Covid-19. Contracting Covid-19 was associated with SARS-CoV-2-specific neutralizing serum IgG, T cell, IFN-γ, and granzyme B responses to SARS-CoV-2, self-reported typical Covid-19 symptoms, male sex, higher BMI, and hypertension. Not contracting Covid-19 was associated with female sex, IgA-dominated, or no antibody responses to SARS-CoV-2, airborne allergy, and smoking. The IgG-responders had SARS-CoV-2-specific T-cell responses including a cytotoxic CD4+ T-cell population expressing CD25, CD38, CD69, CD194, CD279, CTLA-4, and granzyme B. IgA-responders with no IgG response to SARS-CoV-2 constituted 10% of the study population. The IgA responses were partially neutralizing and only seen in individuals who did not succumb to Covid-19. To conclude, serum IgG-dominated responses correlated with T-cell responses to SARS-CoV-2 and PCR-confirmed Covid-19, whereas IgA-dominated responses correlated with not contracting the infection.

Correlates of protection against SARS‐CoV‐2 infection and COVID‐19 disease

“…Chan and colleagues studied pediatric and adult COVID‐19 patients and were able to show spike‐specific IgA in the nasal epithelial lining fluid which appeared to inversely correlate with severity of disease; those with mild disease having higher titers of neutralizing antibody within the first week of illness 35 . A protective role for IgA has also been postulated by Hennings and colleagues who found healthcare workers who did not contract COVID‐19 had higher serum IgA specific for spike protein although they did not study mucosal antibody 36 . Relatively, few studies have focussed on mucosal responses post‐vaccination.…”

“… 35 A protective role for IgA has also been postulated by Hennings and colleagues who found healthcare workers who did not contract COVID‐19 had higher serum IgA specific for spike protein although they did not study mucosal antibody. 36 Relatively, few studies have focussed on mucosal responses post‐vaccination. Nickel and colleagues 37 studied serum and salivary responses following natural infection and vaccination and were unable to detect spike and RBD specific IgG following BNT162b2 vaccination in saliva, in contrast to patients with COVID‐19 who all developed salivary IgG 15‐30 days following the onset of symptoms.…”

“…35 A protective role for IgA has also been postulated by Hennings and colleagues who found healthcare workers who did not contract COVID-19 had higher serum IgA specific for spike protein although they did not study mucosal antibody. 36 Relatively, few studies have focussed on mucosal responses post-vaccination. Nickel and colleagues 37 Also in this study, higher spike and RBD-specific IgA (but not IgG) measured at 2-4 weeks post-dose 2 was associated with protection from subsequent infection.…”

High but Short-lived anti-SARS-CoV2 neutralizing, IgM, IgA, and IgG levels among mRNA-vaccinees compared to naturally-infected participants

“…Most importantly, it is believed that IgA antibodies have the ability to protect unvaccinated subjects against COVID-19 (30). Recently a study, which examined the patterns of humoral and cellular responses to SARS-CoV-2 for 6 months during the COVID-19 pandemic, reported that subjects who had IgA antibodies only, never succumbed to COVID-19, as opposed to subjects with both IgG antibodies and T cells who contracted the disease (30). It is worth noting that IgA antibody responses in nasal secretions of volunteers infected with the common cold coronavirus 229E have been linked to shorter durations of viral shedding (31).…”

“…Furthermore, in natural infection, anti-S1-IgA is known to dominate the early NTAb response (29). Most importantly, it is believed that IgA antibodies have the ability to protect unvaccinated subjects against COVID-19 (30). Recently a study, which examined the patterns of humoral and cellular responses to SARS-CoV-2 for 6 months during the COVID-19 pandemic, reported that subjects who had IgA antibodies only, never succumbed to COVID-19, as opposed to subjects with both IgG antibodies and T cells who contracted the disease (30).…”