Anti-A and SARS-CoV-2: An Intriguing Association

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