Background: Passive antibody therapy with convalescent plasma (CP) represents a promising alternative for the treatment of SARS CoV 2 infection. The efficacy of CP therapy has been associated with high titers of neutralizing antibodies (nAbs) in the plasma of recovered patients, but the assays for quantifying nAbs are not widely available. Our goal was to develop a strategy to predict high titers of nAbs based on the results of anti-SARS CoV 2 immunoassays and the clinical characteristics of the CP potential donors. Methods: Two hundred and fourteen CP donors were enrolled and tested for the presence of anti-SARS CoV 2 antibodies using two commercial immunoassays (IA): Anti SARS CoV 2 ELISA IgG EUROIMMUN and Anti SARS CoV 2 Chemiluminescence IgG Abbott. In parallel, quantification of neutralizing antibodies (nAbs) was performed using the Cytopathic effect-based virus neutralization test (CPE VNT). Three criteria for identifying donors with high titers of nAbs (more than 160) were tested: Criterion1: Curve ROC Method; Criterion 2: Conditional decision tree considering only the results from the IA and Criterion 3: Conditional decision tree including both the IA results and the clinical variables. Results: The performance of Abbott and EUROIMMUN immunoassays was similar referring to both S/CO and predictive value for identifying nAbs titers more than 1:160. Regarding the three studied criteria for identifying CP donors with high nAbs titers (more than 1:160): 1) Criterion 1 showed 76.1% accuracy when the S/CO cut-off of 4.65 was used, 2) Criterion 2 presented 76.1% accuracy if the S/CO more than 4.57 was applied and 3) Criterion 3 had 71.6% accuracy if either S/CO more than 4.57 or S/CO between 2.68 and 4.57 and the last COVID-19-related symptoms occurred less than 19 days from donor recruiting were used. Conclusion: The results of SARS-CoV-2 immunoassays (S/CO) can be used to predict high nAbs titers of potential CP donors. This study has proposed three different criteria for identifying donors with more than 160 nAbs titer based on either solely S/CO results or S/CO together with clinical variables, all with high efficacy and accuracy.

No abstract

Background SARS-CoV-2 serologic surveys estimate the proportion of the population with antibodies against historical variants which nears 100% in many settings. New analytic approaches are required to exploit the full information in serosurvey data. Method Using a SARS-CoV-2 anti-Spike (S) protein chemiluminescent microparticle assay, we attained a semi-quantitative measurement of population IgG titres in serial cross-sectional monthly samples of routine blood donations across seven Brazilian state capitals (March 2021-November 2021). In an ecological analysis (unit of analysis: age-city-calendar month) we assessed the relative contributions of prior attack rate and vaccination to antibody titre in blood donors. We compared blood donor anti-S titre across the seven cities during the growth phase of the Delta variant of concern (VOC) and use this to predict the resulting age-standardized incidence of severe COVID-19 cases. Results On average we tested 780 samples per month in each location. Seroprevalence rose to >95% across all seven capitals by November 2021. Driven proximally by vaccination, mean antibody titre increased 16-fold over the study. The extent of prior natural infection shaped this process, with the greatest increases in antibody titres occurring in cities with the highest prior attack rates. Mean anti-S IgG was a strong predictor (adjusted R2 =0.89) of the number of severe cases caused by the Delta VOC in the seven cities. Conclusions Semi-quantitative anti-S antibody titres are informative about prior exposure and vaccination coverage and can inform on the potential impact of future SARS-CoV-2 variants.

A púrpura trombocitopênica trombótica (PTT) é uma doença rara e fatal que deve ser diagnosticada e tratada prontamente a fim de se obter melhor resposta terapêutica. Apresentamos um caso de PTT aguda grave tratada com plasmaférese e rituximabe. Ao diagnóstico, a paciente apresentava anemia hemolítica microangiopática, icterícia, febre, convulsões, seguidas por coma e choque hipovolêmico. Os exames laboratoriais iniciais mostravam DHL=2.860 IU/L, contagem de plaquetas de 37 x 10 9 /L, hemoglobina de 5,1 g/dL e no esfregaço de sangue periférico havia a presença de esquizócitos. Iniciado tratamento para PTT com pulsoterapia com metilprednisolona e plasmaféreses terapêuticas diárias com troca de uma volemia plasmática e substituição com plasma fresco congelado. Após cinco sessões de plasmaférese, houve piora no quadro neurológico, acompanhado por aumento importante de DHL, ALT, AST e a contagem de plaquetas era de 72 x 10 9 /L. Iniciamos o uso de rituximabe na dose padrão de 375mg/m 2 /semana/4 semanas e passamos a utilizar plasma pobre em crioprecipitado como reposição durante as plasmaféreses. Dois dias após a mudança na conduta terapêutica, houve importante melhora do quadro neurológico, estabilização da contagem de plaquetas e queda acentuada de DHL. Após 23 procedimentos de plasmaférese e quatro doses de rituximabe, a paciente apresentou remissão completa, mantida há 34 meses. A plasmaférese terapêutica com plasma pobre em crioprecipitado e o uso concomitante de rituximabe foi uma estratégia útil no tratamento deste caso de PTT aguda grave. Porém, ensaios clínicos prospectivos e randomizados são necessários para confirmar estes achados.

2, the authors stated that "a recent study shows a high prevalence of anti-HBc (16%) in blood donors" and referred our paper (ALMEIDA NETO et al., 2001) 1 . Actually, we have not studied the prevalence of this marker in blood donors. We did find 16% of false-positive results after retesting 112 isolated anti-HBc seropositive blood donors.