Platelet activation and blood extracellular vesicles: The influence of venepuncture and short blood storage

Extracellular vesicles (EVs) as membrane-bound particles released by various cells are potential tools for diagnosis and treatment. Blood cells, particularly platelets, are the source of circulating EVs.

MATERIAL

EVs were enriched with gradient ultracentrifugation and measured by nanoparticle tracking assay. A flow cytometric multiplex assay was used for cellular source determination. Activation of platelets was measured as a percentage of CD62p+/CD61+ platelets and correlated with the concentration and size of released EVs.

RESULTS

In general there was no statistically significant correlation between EVs` concentration and degree of platelet activation. EVs from different cellular sources were detected. Comparing different needle thicknesses, there was a decrease in the EVs concentration for the 16G needle versus the 21G needle, but no difference was observed for EVs` size and phenotype or platelets activation. During blood storage, platelet activation increased, but there was no effect on the EVs` concentration, size, or phenotype.

CONCLUSIONS

Preanalytical factors like needle thickness and storage time can affect the MVs' properties. Activation of platelets during blood collection or blood storage occurs; however, it is difficult to determine its effect on the physiological properties of EVs since the mechanisms of EVs` biogenesis and especially clearness are not precisely known.

Simple prediction of COVID-19 convalescent plasma units with high levels of neutralization antibodies

BACKGROUND

Hyperimmune convalescent COVID-19 plasma (CCP) containing anti-SARS-CoV-2 neutralizing antibodies (NAbs) was proposed as a therapeutic option for patients early in the new coronavirus disease pandemic. The efficacy of this therapy depends on the quantity of neutralizing antibodies (NAbs) in the CCP units, with titers ≥ 1:160 being recommended. The standard neutralizing tests (NTs) used for determining appropriate CCP donors are technically demanding and expensive and take several days. We explored whether they could be replaced by high-throughput serology tests and a set of available clinical data.

METHODS

Our study included 1302 CCP donors after PCR-confirmed COVID-19 infection. To predict donors with high NAb titers, we built four (4) multiple logistic regression models evaluating the relationships of demographic data, COVID-19 symptoms, results of various serological testing, the period between disease and donation, and COVID-19 vaccination status.

RESULTS

The analysis of the four models showed that the chemiluminescent microparticle assay (CMIA) for the quantitative determination of IgG Abs to the RBD of the S1 subunit of the SARS-CoV-2 spike protein was enough to predict the CCP units with a high NAb titer. CCP donors with respective results > 850 BAU/ml SARS-CoV-2 IgG had a high probability of attaining sufficient NAb titers. Including additional variables such as donor demographics, clinical symptoms, or time of donation into a particular predictive model did not significantly increase its sensitivity and specificity.

CONCLUSION

A simple quantitative serological determination of anti-SARS-CoV-2 antibodies alone is satisfactory for recruiting CCP donors with high titer NAbs.

ABO blood group does not influence the level of anti-SARS-CoV-2 antibodies in convalescent plasma donors

BACKGROUND

The association of the ABO blood group with COVID-19 disease has been confirmed by several studies, with the blood group A patients being more susceptible and prone to a more severe clinical course of the disease. Additionally, several authors also addressed the association of ABO-types and the levels of anti-SARS-CoV-2 antibodies in convalescents, mostly supporting a theory that the non-O blood group convalescents present with higher levels of anti-SARS-CoV-2 antibodies.

STUDY DESIGN AND METHODS

Since previous findings were based on small convalescent cohorts, we quantified the anti-SARS-CoV-2 antibody levels in total 3187 convalescent plasma donors with three commercial serological and one standard neutralizing antibody test. The majority of donors had undergone a mild form of the disease and the median time of sampling was 66 days after diagnosis.

RESULTS

None of the antibody quantitation results showed any significant association with the ABO blood group types. The same result was evident in the subgroup of vaccinated individuals (n=370) and the subgroups when stratified according to post-COVID-19 periods (0-60, 60-120, and 120-180 days).

CONCLUSION

In conclusion, we found no evidence to confirm that the ABO blood group types influence the level of SARS-CoV-2 antibody response in COVID-19 convalescent plasma donors.