ABO Blood Group Incompatibility Protects Against SARS-CoV-2 Transmission

Abstract

ABO blood groups appear to be associated with the risk of SARS-CoV-2 infection, but the underlying mechanisms and their real importance remain unclear. Two hypotheses have been proposed: ABO compatibility-dependence (neutralization by anti-ABO antibodies) and ABO-dependent intrinsic susceptibility (spike protein attachment to histo-blood group glycans). We tested the first hypothesis through an anonymous questionnaire addressed to hospital staff members. We estimated symptomatic secondary attack rates (SAR) for 333 index cases according to spouse ABO blood group compatibility. Incompatibility was associated with a lower SAR (28% vs. 47%; OR 0.43, 95% CI 0.27–0.69), but no ABO dependence was detected in compatible situations. For the second hypothesis, we detected no binding of recombinant SARS-CoV-2 RBD to blood group-containing glycans. Thus, although no intrinsic differences in susceptibility according to ABO blood type were detected, ABO incompatibility strongly decreased the risk of COVID-19 transmission, suggesting that anti-ABO antibodies contribute to virus neutralization.

ABO blood group and link to COVID-19: A comprehensive review of the reported associations and their possible underlying mechanisms

“…The risk of symptomatic COVID-19 transmission was significantly lower for ABO-incompatible couples, while ABO compatibility was associated with higher transmissibility regardless of the ABO blood type of the partner. This supports that all blood types are equally susceptible to COVID-19, and the protection provided by ABO-incompatibility may be due to ABO antibodies [ 123 ].…”

“…This could explain, for instance, the genetic association reported by Valenti et al between non-secretor status and lower risk of severe outcomes among blood type A-individuals [ 80 ]. Conversely, Boukhari et al failed to detect any preferential biding of recombinant RBD to both A type I saccharide and lung tissue from A and O donors, as well as to salivary mucin from secretor-phenotype saliva [ 123 ]. Furthermore, although individuals with blood type A1 display more than fourfold higher A epitope density compared to those with A2 subtype, comparable rates of infection between A1 and A2 participants were reported by Schetelig et al, which suggests that the A antigen itself does not facilitate viral entry [ 48 ].…”

Persistence of Naturally Acquired and Functional SARS-CoV-2 Antibodies in Blood Donors One Year after Infection

“…There are several studies indicating that the AB0 blood group might be an important factor regarding an infection with SARS-CoV-2 [ 33 , 34 , 35 ]. Concerning the infection risk, contradictory results are available: While some studies show a significantly lower infection risk for blood group 0 [ 36 , 37 , 38 , 39 , 40 , 41 ], others show no specific infection risk for any AB0 blood group [ 21 , 42 , 43 ]. Different cohort groups studied might explain discrepant results: While those studies documenting a lower infection risk for blood group 0 mainly focus on patients with severe disease course, studies indicating no difference focus on cases of rather mild disease course.…”

Lower Levels of ABO Anti-A and Anti-B of IgM, IgG and IgA Isotypes in the Serum but Not the Saliva of COVID-19 Convalescents

“…In light of these observations, we hypothesized that natural anti-A and/or anti-B might play a protective role against SARS-CoV-2 infection when transmitted between individuals with different ABO blood types [ 30 , 31 ]. Assuming that ABO antibody activity in saliva reflects its activity in the respiratory mucosa, differences in ABO antibody concentrations in saliva were also expected.…”