Broad Cross-reactive IgA and IgG Against Human Coronaviruses in Milk Induced by COVID-19 Vaccination and Infection

  

It is currently unclear if SARS-CoV-2 infection or mRNA vaccination can also induce IgG

and IgA against common human coronaviruses (HCoVs) in lactating parents. Here we prospectively

analyzed human milk (HM) and blood samples from lactating parents to measure the temporal

patterns of anti-SARS-CoV-2 specific and anti-HCoV cross-reactive IgA and IgG responses. Two

cohorts were analyzed: a vaccination cohort (n = 30) who received mRNA-based vaccines for

COVID-19 (mRNA-1273 or BNT162b2), and an infection cohort (n = 45) with COVID-19 disease.

Longitudinal HM and fingerstick blood samples were collected pre- and post-vaccination or, for

infected subjects, at 5 time-points 14–28 days after confirmed diagnosis. The anti-spike(S) and antinucleocapsid(

N) IgA and IgG antibody levels against SARS-CoV-2 and HCoVs were measured by

multiplex immunoassay (mPlex-CoV).We found that vaccination significantly increased the anti-S

IgA and IgG levels in HM. In contrast, while IgG levels increased after a second vaccine dose, blood

and HM IgA started to decrease. Moreover, HM and blood anti-S IgG levels were significantly

correlated, but anti-S IgA levels were not. SARS2 acute infection elicited anti-S IgG and IgA that

showed much higher correlations between HM and blood compared to vaccination. Vaccination and

infection were able to significantly increase the broadly cross-reactive IgG recognizing HCoVs in

HM and blood than the IgA antibodies in HM and blood. In addition, the broader cross-reactivity of

IgG in HM versus blood indicates that COVID-19 vaccination and infection might provide passive

immunity through HM for the breastfed infants not only against SARS-CoV-2 but also against

common cold coronaviruses.