The correlation between severe complications and blood group types in COVID-19 patients, with possible role of T polyagglutination in promoting thrombotic tendencies

Introduction: Coronavirus disease-19 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is still posing detrimental effects on people. An association between contracting COVID-19 and the ABO blood group type has been determined. However, factors that determine the severity of COVID-19 are not yet fully understood. Thus, the current study aimed to investigate whether the ABO blood group type has a role in the severity of complications due to COVID-19. Materials and methods: Eighty-Six ICU-admitted COVID-19 patients and 80 matched -healthy controls were recruited in the study from Baish general hospital, Saudi Arabia. ABO blood grouping, complete blood count (CBC), CBC-derived inflammatory markers, coagulation profile, D-Dimer and anti-T antigen were reported. Results: Our data showed that patients with blood groups O and B are more protective against severe complications from COVID-19, as compared to patients with blood groups A and AB. This could be partially attributed to the presence of anti-T in blood group A individuals, compared to non-blood group A. Conclusion: The current study reports an association between the ABO blood group and the susceptibility to severe complications from COVID-19, with a possible role of anti-T in driving the mechanism of the thrombotic tendency, as it was also correlated with an elevation in D-dimer levels.

COVID-19 convalescent plasma: Mechanisms of action and rationale for use: A narrative review

The use of convalescent plasma (CP) transfusions for patients with coronavirus disease 2019 (COVID-19) has gained great interest during the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic. This review aims at summarizing the literature on the potential mechanisms of action of COVID-19 CP (CCP) and the rationale for use. A narrative review of the literature was conducted using PubMed, Google Scholar, and the Cochrane Database through October 2020. The rationale of CCP deployment was based on historical use in other outbreaks and pandemics and the emergent need at the time of lack of proven therapies and vaccines. There are many proposed mechanisms of action including direct neutralization and suppression of viremia, antibody-dependent cellular cytotoxicity, modification of the inflammatory response, restoration of the coagulation factors, immunomodulation of the hypercoagulable state and the potential role of ABO naturally occurring iso-agglutinins. Many donor, product, and patient factors can impact the response to CCP, such as antibody titer in the CCP product, CCP dose, frequency of administration, the severity of underlying illness, and the timing of administration from time of disease onset. Based on current evidence, CCP appears to be safe. However, it remains unknown whether it impacts the improvement of clinical symptoms, time to death, and all-cause mortality. In conclusion, the use of CCP offers quick access as an empirical therapy when specific therapies are not available or under development. Ongoing clinical trials are expected to add to the breadth of knowledge on the safety and efficacy of CCP use in patients with COVID-19.Copyright © 2021 AME Publishing Company.

SARS-CoV-2 and Helicobacter pylori and some hematological parameters: A case-control study

Background: The SARS-CoV-2 associated with bacterial infection represents a serious public health challenge. Recently, there is a remarkable increase in the number of researches that confirms the effect of Helicobacter pylori on pulmonary diseases. Aim(s): The goal of this research was to see how H. pylori affected the presentation of COVID-19 infections as a prospective risk factor. Material(s) and Method(s): This research was conducted in Babylon, Iraq, from January 1, 2022, to March 5, 2022. A total of 180 people were engaged in this study, with 90 patients identified with SARS-CoV-2 by polymerase chain reaction testing and 90 people serving as a control group. Antibody screening assays on blood samples were used to look for antibodies against H. pylori. The samples were processed for complete blood count and ABO blood group. Result(s): COVID-19 infection was more frequent in females than in males, especially between 31 and 45 years. When compared to healthy people, COVID-19 patients had a higher white blood cell count (P = 0.0001) and a lower lymphocyte count (P = 0.0001). H. pylori and COVID-19 have been found to have a strong relationship, especially in females. When comparing patients to healthy people, blood group A is the most common. Conclusion(s): People with H. pylori infections are considerably more sensitive to COVID-19 than people without H. pylori infections (P = 0.011). In combination with SARS-CoV-2, IgG for H. pylori might be a risk factor.Copyright © 2023 Journal of Medical Society Published by Wolters Kluwer-Medknow.

Anti-human leukocyte antigen and anti-ABO antibodies after SARS-CoV-2 mRNA vaccination in kidney transplant recipients.

INTRODUCTION: In this study, we evaluated whether SARS-CoV-2 mRNA vaccines induce anti-human leukocyte antigen (HLA) antibodies and anti- ABO blood type antibodies (ABOAb) in kidney transplant recipients (KTRs). METHODS: Sixty-three adult KTRs with functioning grafts who received two doses of the SARS-CoV-2 mRNA vaccine were enrolled in this cohort. Changes in anti-ABO blood type immunoglobulin IgM and IgG antibody titers, flow panel reactive antibody (PRA), de novo donor-specific anti-human leukocyte antigen antibodies (DSA), and kidney allograft function before and after vaccination were evaluated. RESULTS: Only one patient experienced conversion from negative to positive flow PRA after vaccination. However, there was no DSA in single antigen flow-bead assays. The mean fluorescence intensity (MFI) in the eight DSA-positive recipients did not significantly change before and after vaccination (p = .383), and no additional DSA was produced after vaccination in those patients. No significant elevation of ABOAb titer was observed for either IgM (p = .438) or IgG (p = .526) after vaccination. There was no significant deterioration in estimated glomerular filtration rate (eGFR) after vaccination (p = .877) or elevation of the urine protein-to-creatinine ratio (p = .209) after vaccination. One episode of AMR was observed in addition to a preexisting acute cellular rejection. CONCLUSIONS: The SARS-CoV-2 mRNA vaccine did not induce anti-HLA antibody or ABOAb production in KTRs.

The association of ABO blood group distribution and clinical characteristics in patients with SARS-CoV-2.

INTRODUCTION: SARS-COV-2, the novel severe acute respiratory syndrome coronavirus, has become a life-threatening public health crisis. This kind of pandemic is frightening the world with clinical, psychological, and emotional distress and leading to an economic slowdown. To explore any association between the ABO blood type and the susceptibility to coronavirus disease 2019 (COVID-19), we compared ABO blood group distribution among 671 COVID-19 patients with the local control population. METHODOLOGY: The study was conducted in Blood Bank Hospital in Erbil, Kurdistan Region, Iraq. The ABO-typed blood samples were obtained from 671 patients infected with SARS-CoV-2 between February and June 2021. RESULTS: Our results demonstrated that the risk of SARS-COV-2 was higher for patients with blood group A than those with not-A blood type patients. Of the 671 patients with COVID-19, 301 had type A (44.86%), 232 had type B (34.58%), 53 had type AB blood (7.9%), and 85 had type O (12.67%). CONCLUSIONS: We concluded that the Rh-negative blood type has a protective effect on SARS-COV-2. Our results also indicate that the decreased susceptibility of individuals with blood group O and the increased susceptibility of individuals with blood group A to COVID-19 could be linked to the presence of natural anti-blood group antibodies, particularly anti-A antibody, in the blood. However, there might be other mechanisms that require further study.

Association of ABO blood group with susceptibility to SARS-CoV-2 infection in Rupandehi district of Nepal.

Objectives: Recent studies after the outbreak of coronavirus disease 2019 have shown an association of the ABO blood group to the susceptibility of severe acute respiratory syndrome coronavirus 2 infection. Anti-A and anti-B antibodies, carbohydrate clustering, interleukin-6 levels and host transmembrane protease serine subtype 2 were suggested to cause the variable susceptibility of severe acute respiratory syndrome coronavirus 2 infection to the ABO blood groups. This study aims to find the association of the ABO blood group with severe acute respiratory syndrome coronavirus 2 infection susceptibility in Nepal. Methods: Population-based matched case-control study was conducted from October 2021 to February 2022 in Rupandehi district of Nepal. A total of 1091 reverse transcription-polymerase chain reaction confirmed coronavirus disease 2019 cases and 2182 controls were included in the study by convenient sampling method. Results: A statistically significant association of severe acute respiratory syndrome coronavirus 2 infection was observed for the blood group AB between cases and controls (11.5% vs 8.5%; odds ratio = 1.4, 95% confidence interval = 1.10-1.78). However, there was no association of severe acute respiratory syndrome coronavirus 2 infection for blood group A (26.7% vs 28.23%; odds ratio = 0.93, 95% confidence interval = 0.79-1.09), B (26.9% vs 29.84%; odds ratio = 0.86, 95% confidence interval = 0.73-1.02) and O (34.9% vs 33.41%; odds ratio = 1.07, 95% confidence interval = 0.92-1.25). Conclusion: This study reported slightly more susceptibility to severe acute respiratory syndrome coronavirus 2 infection among individuals with blood group AB.

Blood-Type-A is a COVID-19 infection and hospitalization risk in a Turkish cohort.

We have shown in an ethnically homogenous Turkey cohort with more than six thousand cases and 25 thousand controls that ABO blood types that contain anti-A antibody (O and B) are protective against COVID-19 infection and hospitalization, whereas those without the anti-A antibody (A and AB) are risks. The A + AB frequency increases from 54.7 % in uninfected controls to 57.6 % in COVID-19 outpatients, and to 62.5 % in COVID-19 inpatients. The odds-ratio (OR) for lacking of anti-A antibody risk for infection is 1.16 (95 % confidence interval (CI) 1.1-1.22, and Fisher test p-value 1.8 × 10-7). The OR for hospitalization is 1.23 (95 %CI 1.06-1.42, Fisher test p-value 0.005). A linear regression treating controls, outpatients, inpatients as three numerical levels over anti-A antibody leads to a p-value of 5.9 × 10-9. All these associations remain to be statistically significant after conditioning over age, even though age itself is a risk for both infection and hospitalization. We also attempted to correct the potential effect from vaccination, even though vaccination information is not available, by using the date of the data collection as a surrogate to vaccination status. Although no significant association between infection/hospitalization with Rhesus blood system was found, forest plots are used to illustrate possible trends.

A population-based, retrospective cohort study of the association between ABO blood group and risk of COVID-19.

BACKGROUND: Several studies have investigated associations between ABO blood group and risk of COVID-19, with inconsistent results. OBJECTIVE: To study associations between ABO blood group and risk of different stages of COVID-19. METHODS: The study was based on nationwide registers encompassing all blood-grouped persons in Sweden, and all of their COVID-19-related outcomes. Associations between ABO blood group and COVID-19 outcomes were estimated using Poisson regression models. Analyses were conducted overall and stratified by vaccination status. RESULTS: A total of 4,986,878 individuals were included. The incidence rate ratios of testing positive for COVID-19 were 1.08 (95% confidence interval [CI], 1.07-1.08), 1.06 (95% CI, 1.05-1.07), and 1.01 (95% CI, 1.00-1.01) for blood groups A, AB, and B, respectively, as compared to O. Similar associations were seen for risk of hospital admissions, intensive care unit admissions, and risk of death. For most outcomes, associations with ABO blood group were much attenuated or even reversed in vaccinated individuals. CONCLUSIONS: Individuals with blood groups A, AB, and B are at increased risk of contracting COVID-19 as well as developing more severe forms of the disease.

Relationship between COVID-19 infection and ABO and Rh blood group systems

Purpose: The aim of this study was to determine whether there is a relationship between COVID-19 infection and ABO and Rh blood groups.Materials and Methods: 1360 patients with positive SARS-CoV-2 RNA test between April 2020 and March 2022 and 80219 healthy controls whose blood groups were determined before March 2020 were included in this study. Patients were classified according to disease severity as mild, moderate, severe and critical.Results: Patient and control groups were matched in terms of age and gender using case-control matched method. 1360 patients and 1161 controls were included in the analysis. Of the patients, 42.1% (n=572) had mild, 41.5% (n=564) moderate, 13.8% (n=187) severe and 2.7% (n=37) critical course of infection. It was observed that patients with blood group A were 1.33 times more at risk (OR: 1.33, 95%Cl: 1.12-1.56) for the development of COVID-19 infection compared to patients with other blood groups. No relationship was found between ABO and Rh blood groups and severe-critical COVID-19 disease, need for intensive care and mortality. However, when patients are divided into two groups as mild and non-mild (moderate, severe, critical);the frequency of having O and B blood groups was found to be significantly higher in non-mild cases than in mild cases ( (53.3% and 46.7%), (64.5% and 35.5%, respectively). Conclusion: In our study, while A blood group was found to be at risk for the development of COVID-19 infection, no relationship was found between Rh blood groups and susceptibility to the disease. In addition, the rate of O and B blood groups was found to be higher in patients who did not have mild disease.

Sex and ABO Blood Differences in SARS-CoV-2 Infection Susceptibility.

Data consisting of millions of cases cannot still explain the immunopathogenesis mechanism between severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and host cell for ongoing coronavirus disease 2019 (COVID-19) pandemics. Epidemiological studies among different populations suggested different impacts of ABO and Rh antibodies on the COVID-19 susceptibility. Thus, the ABO blood group and the SARS-CoV-2 infection paradox remain unclear. Therefore, the present retrospective case-control study aimed to investigate the possible association between ABO blood groups and Rh blood types on SARS-CoV-2 infection in the Turkish Cypriot population. A total of 18,639 Turkish Cypriot subjects (297 SARS-CoV-2 COVID-19 patients and 18,342 healthy) were included in this study. Personal and clinical characteristics including age, gender, SARS-CoV-2 infection status, the ABO blood group and Rh blood types were evaluated and compared between two groups. As a result, ABO blood group was shown to be associated with a higher risk of SARS-CoV-2 infection as well as with male sex ( p = 0.018). There was no association between Rh blood type and COVID-19. Overall, this study is the first largest sample group study to show the distribution of ABO blood group and Rh blood types in the healthy Turkish Cypriot population. Based on the current evidence, there are insufficient data to guide public health policies regarding COVID-19 pathogenesis.

Probability of Covid-19 in Abo Blood Type during Second Wave in Southern Rajasthan, India

Objectives: Along the course human history of scientific research, the severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) is the most concerning global health problem. Second wave of COVID-19 has adversely affected India. However, India embarked on its immunization program on January 16, 2021, operating 3006 vaccination centers onset Covaxin and CoviShield. This study aimed to ascertain if there is an association amidst ABO blood type and probability of COVID-19 infection in wave. Method(s): This is analytical and observational study conducted on 713 SARS-COVID-19-positive patients of a known ABO blood type, who attended outpatient department and inpatient department during March 26-May 20, 2021, in tertiary care hospital Udaipur (Raj.) Serum inflammatory markers were evaluated by Cobas 6000. Result(s): Out of the 713 patients who were tested positive, 15.56% was blood group Type A, 19.91% was blood group Type B, 13.65% was blood group Type AB, and 46.28% was blood group Type O. On statistical analysis, there were positive association between O+ blood type and peak inflammatory marker (interleukin-6 and D-Dimer). Patients with blood Type O who received a test were more likely to test positive and blood Type B+, A+, A+, AB+, O-, A-, B-, and AB- were less likely to test positive. Conclusion(s): The present study shows an evidence for interrelation between ABO blood groups and SARS-COVID-19. Reported infection prevalence is moderately increased among O+ blood type individuals. Determination of level of inflammatory markers might prove to be helpful to clinicians so as to keep track of severity of infection and evaluate the prognosis of SARS-COVID-19 with specific ABO blood groups. Copyright © 2022 The Authors. Published by Innovare Academic Sciences Pvt Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

Correlation between severe acute respiratory syndrome Coronavirus-2 and cytomegalovirus

Background: Severe acute respiratory syndrome coronavirus-2 (SARS-CoV2), which causes the novel betacoronavirus 2019 disease (COVID-19), has become the first global pandemic in 100 years. Cytomegalovirus (CMV) is a prevalent herpesvirus that affects 40%-70% of the general population. This study aimed to see how CMV affected the presentation of COVID-19 infections as a prospective risk factor. Material and Methods: This study was conducted in Babylon, Iraq, from January to March, 2022. A total of 120 people were engaged in this study divided into four groups: mild, moderate, severe, and control group, 30 individuals in each group. Ninety patients identified with SARS-CoV-2 by PCR testing and 30 people serving as a control group. IgG antibody titer in blood samples were detected by mini vidas biomerieux. The samples were processed with the complete blood count (CBC) and ABO blood group. Independent T and Chi-square tests were used to examine the data using SPSS 21 software. Results: COVID-19 infection was more frequent in females than males. The COVID-19 patients were detected to have increased white blood cell count (p < 0.0001) and decreased lymphocytes compared to the healthy persons (p < 0.0001). No significant correlation between CMV and COVID-19 was discovered. CMV titer was not associated with disease severity. Blood group A is the most predominant type in patients compared to healthy persons. Conclusion: This study revealed no significant correlation between the severity of COVID-19 and CMV in spite of slightly increased in severe patients at mean 66.53 compared to the control group 58.80 (p = 0.26). Reactivation of CMV in COVID-19 patients may be associated with complications, so more attention should be taken into consideration regarding this virus, especially in severe patients. © 2022 Medical Journal of Dr. D.Y. Patil Vidyapeeth ;Published by Wolters Kluwer - Medknow.

The association between different blood group systems and susceptibility to COVID-19: a single center cross-sectional study from Saudi Arabia.

Background: Since the beginning of COVID-19 pandemic, many associated factors have been investigated to clarify the susceptibility and severity among the affected individuals. Biological markers can play an important role in identification of individual susceptibility to such pandemic. Growing evidence suggest the influence of different blood group systems on susceptibility to COVID-19 virus, with a particular blood type conferring selection advantage. Objectives: The study aimed to determine the association of ABO, Rhesus (D) and P1 blood groups with COVID-19 susceptibility in Taif city, Western Saudi Arabia. Methods: ABO, D and P1 blood antigens were determined in 104 blood samples of COVID-19 patients versus 100 control samples using either automated immunohematology analyser or test tube method. Statistical differences between patients and control samples were calculated based on p-value where results of ≤ 0.05 were considered significant. Results: O+ve blood group constituted the predominant type among the studied samples. Determination of P1 antigen showed significant association where Anti-P1 was positive in 76.9% of patients compared to 61.0% of controls with a P value of 0.01 conferring the susceptibility of P1+ve patients to COVID-19. Conclusion: Although our study showed no significant association between ABO and D, and susceptibility to COVID-19, there was a significant association between P1+ve and COVID-19. P1+ve participants were 2.131 times more associated with the risk of COVID-19 infection than those with Anti P1-ve. Thus, P1 antigen can be used as a biological marker for identification of individuals susceptibility to COVID-19. It is strongly advised that such individuals should consider extra protective measures. Further studies on other contributing factors should also be considered for more scientific clarity.

Correlation between ABO blood type, susceptibility to SARS-CoV-2 infection and COVID-19 disease severity: A systematic review.

Objectives: To verify the association between the ABO blood type and the risk of SARS-CoV-2 infection and COVID-19 disease severity. Methods: This review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), using the 2020 PRISMA Checklist and flow diagram, and articles selected for review were analyzed using the Newcastle-Ottawa Quality Rating Scale. The research question was: "Would the ABO blood group influence the risk of infection and clinical course of patients infected with SARS-CoV-2?", The following databases were used: Embase, PubMed, Virtual Health Library (VHL), Web of Science, ScienceDirect and Scopus. The protocol for this review was registered in the Prospective Register of Systematic Reviews (PROSPERO), number CRD42021245945. Results: We found 798 articles across PubMed, Embase, Scopus, Web of Science, Science Direct and Virtual Health Library and 54 articles were included in the final analysis. Among 30 studies evaluating the risk of COVID-19 infection, 21 found significant correlations with ABO blood groups, 14 of them revealing an increased risk in blood group A and 15 studies showing a decreased risk in blood group O. Most studies found no significant correlation with disease severity or mortality. Conclusion: The qualitative assessment of available information suggests that blood group A may be a risk factor for COVID-19 infection and that blood group O may have a protective effect. We were unable to determine a clear association between the ABO blood group and mortality. These conclusions are based on highly heterogenous evidence.

Prediction of Covid-19 infection severity using ABO blood group types and Rh factor

Background and Objective: Biological markers for the prediction of acquiring Covid-19 risk are deficient and there is a dire need of immediate research data. The objective of the study was to predict the link of ABO blood group types along with Rh factor distribution with the severity of Covid-19. Methods: This was an observational cross-sectional survey conducted in medicine department of Pakistan Ordnance Factory Hospital, Wah Cantt Pakistan, from August 2020 to December 2020 after approval of IRB. Participants tested positive for presence of Covid-19 infection by polymerase chain reaction (PCR) were included in the study. Covid-19 infection severity was measured through mild, moderate and severe disease categories and analyzed. ABO blood group and Rh subgroups data for all the Covid-19 infected patients were obtained from the laboratory section of the hospital and analyzed. Data was entered in SPSS v 26 and analyzed. Cox regression model was used to find out the severity of Covid-19. Results: Total 248 patients were included;75% patients were male and 25% were females. The mean age of the patients was 52.77±15.58 years. A very significant association was found between ABO blood group types, Rh factor antigen and severity of Covid-19 (p=0.001). When stratified ABO, Rh antigen blood group with health status of all patients there was a very significant association between them (p=0.013). An insignificant association between male and female odds ratio of ABO blood group types but blood group B, Rh positive antigen was more susceptible in Covid-19 positive patients. Conclusion: There is a link between ABO blood group types along with Rh factor antigen (B+ and O+) with the severity of Covid-19 positive patients. ABO blood group types and Rh factor can be used as a potential marker/tool to predict the susceptibility of acquiring Covid-19 infection as well as for severity of the infection.

Association between blood group and COVID-19: A case-control study

Context: COVID-19 is an emerging infectious disease and blood group has an influence on the susceptibility of infectious diseases including COVID-19. Aim: The present study was conducted with the aim to observe the association of ABO blood groups with COVID-19. Setting and Design: A nonexperimental hospital-based case-control research design was adopted to conduct the study with 200 COVID-19 patients who met the inclusion criteria. Subjects and Methods: Informed consent was obtained from the participants after explained the purpose of the study. Data were collected by interview method using a structured questionnaire and medical record was also utilized to collect the data. The collected data were prepared for analysis using Microsoft Excel. Statistical Analysis Used: Both descriptive and inferential statistical methods were used to analyze the data using the software SPSS 16 version. Results: The results of the study revealed that out of 200 participants, 83 (42.5%) belonged to A+, 68 (33%) belonged to B+, 7 (14%) belonged to O+, 18 (9%) belonged to AB +, and 4 (%) belonged to A-blood group. Conclusion: The findings of the current study concluded that the prevalence rate of COVID-19 was higher among non-O blood group than in the O blood group and the blood group is associated with the severity of illness. Despite further studies on the individuals with confirmed exposure to COVID-19 infection should be conducted with large samples to generalize the findings. © 2022 Wolters Kluwer Medknow Publications. All rights reserved.

Blood group O is associated with post-COVID-19 syndrome in outpatients with a low comorbidity index.

BACKGROUND: ABO blood group system modulates the inflammatory response and has been implicated in COVID-19. Group O protects against SARS-CoV-2 infection, but there are no data regarding post-COVID-19 syndrome (PCS). Our aim was to assess this possible association. METHODS: Case-control study in a community setting, with subjects who had experienced mild COVID-19. Cases were PCS+, controls were PCS-, and the exposure variable, group O. We collected age, sex, BMI, smoking, comorbidities, inflammatory markers, anti-SARS-CoV-2 IgG antibodies, blood type and clinical data. Five composite inflammatory indices were developed. Multivariate analyses were performed. RESULTS: We analysed 121 subjects (56.2% women), mean age 45.7 ± 16 years. Blood group frequencies were 41.5%, 7.9%, 5.9%, and 44.5% for A, B, AB and O, respectively. Thirty-six patients were PCS+, without significant differences between cases and controls. Compared to non-O, a higher prevalence of PCS (p = .036), and number of symptoms of PCS (p = .017) were noted in group O. Concerning biomarkers, PCS + and PCS- showed no differences in A, B, and AB groups. In contrast, group O PCS + patients had significantly lower albumin-to-globulin ratio and higher lymphocyte count, fibrinogen, CRP levels, and higher percentages of 3 composite indices, than PCS- subjects. Group O showed a 6-fold increased risk of PCS, compared to non-O (adjusted OR = 6.25 [95%CI, 1.6-23]; p = .007). CONCLUSIONS: Group O has shown a consistent relationship with PCS, characterised by a more intense inflammatory burden than the other blood groups. Blood group O could be part of the immunological link between acute COVID-19 and PCS.

ABO Blood System and COVID-19 Susceptibility: Anti-A and Anti-B Antibodies Are the Key Points.

The implication of the ABO blood group in COVID-19 disease was formulated early, at the beginning of the COVID-19 pandemic more than 2 years ago. It has now been established that the A blood group is associated with more susceptibility and severe symptoms of COVID-19, while the O blood group shows protection against viral infection. In this review, we summarize the underlying pathophysiology of ABO blood groups and COVID-19 to explain the molecular aspects behind the protective mechanism in the O blood group. A or B antigens are not associated with a different risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection than that of other antigens. In this case, the cornerstone is natural anti-A and anti-B antibodies from the ABO system. They are capable of interfering with the S protein (SARS-CoV-2) and angiotensin-converting enzyme 2 (ACE2; host cell receptor), thereby conferring protection to patients with sufficient antibodies (O blood group). Indeed, the titers of natural antibodies and the IgG isotype (specific to the O blood group) may be determinants of susceptibility and severity. Moreover, older adults are associated with a higher risk of bad outcomes due to the lack of antibodies and the upregulation of ACE2 expression during senescence. A better understanding of the role of the molecular mechanism of ABO blood groups in COVID-19 facilitates better prognostic stratification of the disease. Furthermore, it could represent an opportunity for new therapeutic strategies.

ABO Blood Group in Relation to COVID-19 Susceptibility and Clinical Outcomes: A Retrospective Observational Study in the United Arab Emirates.

(1) Background: The association between ABO blood groups and COVID-19 outcomes was investigated in several studies. The results were controversial. This study aimed to explore the association between ABO blood groups and COVID-19 outcomes. (2) Methods: This retrospective study included 303 COVID-19 patients treated at the NMC Royal Hospital in the United Arab Emirates between 8 April 2020 and 30 June 2020. (3) Results: The mean age of patients included in the study was 39.3 ± 10.7 years, and 72.9% of patients were males. The prevalence of blood groups O, A, B, and AB was 40.3%, 27.7%, 25.1%, and 6.9%, respectively. The correlation between ABO blood groups and COVID-19 outcomes was insignificant except in the AB group, with significantly higher odds of disease severity. Increased age, higher body mass index (BMI), and being of male gender increased the risk for pneumonia among all blood groups. Both increased age and higher BMI increased the risk of mortality, and increased age increased the risk of disease severity. Troponin and platelet counts were significantly different in the A group compared to the non-A groups. Time to viral clearance was not different among blood groups. However, adjustment for Rh groups resulted in a significantly shorter time in the B group. (4) Conclusions: There was no significant association between ABO blood groups and COVID-19 outcomes, with the exception of group AB.

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.

Individuals with ABO type O, naturally possessing anti-A and anti-B antibodies in their serum, are underrepresented among patients infected with SARS-CoV-2 compared with healthy controls. The ABO antibodies might play a role in the viral transmission. Therefore, we aimed to quantify anti-A/anti-B, including their subclasses IgM, IgG and IgA, in the serum and saliva of Caucasians (n = 187) after mild COVID-19 to compare them with individuals who had never been infected with SARS-CoV-2. Two samples were collected within two months after the diagnosis (median days: 44) and two months later. ABO antibodies were determined by flow cytometry. Additionally, total IgA in saliva and antibodies specific to SARS-CoV-2 were tested by ELISA. COVID-19 convalescents had significantly lower levels of anti-A/anti-B IgM, IgG and IgA in their serum than control subjects (p < 0.001). Interestingly, no significant differences were observed in saliva. ABO antibody levels remained stable over the period considered. No relation of ABO to the level of SARS-CoV-2-specific antibodies was observed. Total IgA was lower in convalescents than in controls (p = 0.038). Whereas ABO antibodies in the saliva may not contribute to the pathogenesis of COVID-19, individual pre-existing high serum concentrations of anti-A/anti-B may have a protective effect against SARS-CoV-2 infection.