Anti-A and SARS-CoV-2: An intriguing association

ABSTRACT

Background/Case Studies It is not clear which individual characteristics can determine susceptibility and intensity of symptoms, however, age, sex, ethnicity, hypertension and some haematological biomarkers, as Ddimer, thrombocytopenia and lymphopenia were associated with a worse outcome. Recently, it has been hypothesized that ABO blood groups can be related to susceptibility to the SARS-CoV-2 infection. Considering that the first studies reported A group as a risk factor and O group as a protection, some authors have been suggesting that the anti-A antibodies, and not the blood group, could be responsible for the findings. Study Design/Methods: A retrospective study with 430 COVID-19 individuals (268 COVID-19 convalescent plasma donors-CCPD and 162 COVID-19 inpatients-CIP) from two Brazilian reference hospitals, confirmed by RTPCR, and 2,212 healthy volunteer blood donors (VBD) as control group, that were evaluated and divided into two groups one with anti-A (O/B blood groups) and one without anti-A group (A/AB blood groups). Immunoglobulins and neutralizing antibody titres were measured for CCPD and CIP. Multivariate logistic regression and nonparametric tests were performed. Results/Findings: Although O blood group was the most frequent ABO group among VBD, A blood group was more frequent among COVID-19 individuals (CCPD 47.8%, CIP 43.2%, VBD 35.5%, p<0.001). There was no statistical difference in blood groups distribution between CCPD and CIP (p=0.268). In our cohort, for each increased age year there was 6% more chance for COVID-19 (OR 1.06;CI 95% 1.05-1.06, p<0.001), males showed 27% more chance for the disease (OR 1.27;CI 95%1.02-1.59, p=0.035) and O/B blood groups showed 38% less infection prevalence (OR 0.62;CI 95% 0.5-0.7, p<0.001). Considering the fact that higher anti-A is usually described in the O blood group, data from O versus B blood groups individuals were analysed and the former showed 34% less chance for COVID-19 (OR 0.66;CI 95%0.46-0.95, p=0.026). There was no difference regarding ABO group found when COVID-19 inpatients of all blood types were analysed. Immunoglobulins A, M and G (IgA, IgM and IgG) and neutralizing antibodies (NAbs) for SARS-CoV-2 were lower in COVID-19 individuals O/B blood groups (NAbs p=0.008, IgM p=0.03, IgG p=0.02, IgA p=0.03). Conclusions: In our retrospective cohort, the COVID-19 individuals O/B blood groups (which produces anti-A) had 38% less chance to have a diagnosis of COVID-19 (p<0.001) and the same groups showed lower titers of neutralizing antibodies, IgM, IgG and IgA. Groups O/B showed a protective factor against the SARS-CoV-2 infection, but it was not associated to COVID-19 inpatients (versus COVID-19 convalescent plasma donors) suggesting that blood type is not associated to SARSCoV- 2 infection severity.