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We detected Mayaro virus (MAYV) in 3.4% (28/822) of febrile patients tested during 2018-2021 from Roraima State, Brazil. We also isolated MAYV strains and confirmed that these cases were caused by genotype D. Improved surveillance is needed to better determine the burden of MAYV in the Amazon Region. [ABSTRACT FROM AUTHOR]

• Over 75% of adult individuals had antidengue antibodies in the city of Manaus. • Dengue virus-positive individuals do not cross-neutralize zika virus efficiently. • Varying degree of cross-reactivity against emerging and endemic Flaviviruses. Several Flaviviruses can co-circulate. Pre-existing immunity to one virus can modulate the response to a heterologous virus; however, the serological cross-reaction between these emerging viruses in dengue virus (DENV)-endemic regions are poorly understood. A cross-sectional study was performed among the residents of Manaus city in the state of Amazonas, Brazil. The serological response was assessed by hemagglutination inhibition assay (HIA), enzyme-linked immunosorbent assay, and neutralization assay. A total of 74.52% of the participants were immunoglobulin G-positive (310/416), as estimated by lateral flow tests. Overall, 93.7% of the participants were seropositive (419/447) for at least one DENV serotype, and the DENV seropositivity ranged between 84.8% and 91.0%, as determined by HIA. About 93% had antiyellow fever virus 17D-reactive antibodies, whereas 80.5% reacted to wild-type yellow fever virus. Zika virus (ZIKV) had the lowest seropositivity percentage (52.6%) compared with other Flaviviruses. Individuals who were DENV-positive with high antibody titers by HIA or envelope protein domain III enzyme-linked immunosorbent assay reacted strongly with ZIKV, whereas individuals with low anti-DENV antibody titers reacted poorly toward ZIKV. Live virus neutralization assay with ZIKV confirmed that dengue serogroup and ZIKV-spondweni serogroup are far apart; hence, individuals who are DENV-positive do not cross-neutralize ZIKV efficiently. Taken together, we observed a high prevalence of DENV in the Manaus-Amazon region and a varying degree of cross-reactivity against emerging and endemic Flaviviruses. Epidemiological and exposure conditions in Manaus make its population susceptible to emerging and endemic arboviruses. [ABSTRACT FROM AUTHOR]

Currently, there are no evidence-based treatment options for long COVID-19, and it is known that SARS-CoV-2 can persist in part of the infected patients, especially those with immunosuppression. Since there is a robust secretion of SARS-CoV-2-specific highly-neutralizing IgA antibodies in breast milk, and because this immunoglobulin plays an essential role against respiratory virus infection in mucosa cells, being, in addition, more potent in neutralizing SARS-CoV-2 than IgG, here we report the clinical course of an NFκB-deficient patient chronically infected with the SARS-CoV-2 Gamma variant, who, after a non-full effective treatment with plasma infusion, received breast milk from a vaccinated mother by oral route as treatment for COVID-19. After such treatment, the symptoms improved, and the patient was systematically tested negative for SARS-CoV-2. Thus, we hypothesize that IgA and IgG secreted antibodies present in breast milk could be useful to treat persistent SARS-CoV-2 infection in immunodeficient patients. [ABSTRACT FROM AUTHOR]

Previous studies have indicated that antibody responses can be robustly induced after the vaccination in individuals previously infected by SARS-CoV-2. To evaluate anti-SARS-CoV-2 humoral responses in vaccinated individuals with or without a previous history of COVID-19, we compared levels of anti-SARS-CoV-2 antibodies in the sera from 21 vaccinees, including COVID-19-recovered or -naïve individuals in different times, before and after immunization with an inactivated COVID-19 vaccine. Anti-SARS-CoV-2-specific antibodies elicited after COVID-19 and/or immunization with an inactivated vaccine were measured by ELISA and Plaque Reduction Neutralizing assays. Antibody kinetics were consistently different between the two vaccine doses for naïve individuals, contrasting with the SARS-CoV-2-recovered subjects in which we observed no additional increase in antibody levels following the second dose. Sera from SARS-CoV2-naïve individuals had no detectable neutralizing activity against lineage B.1 SARS-CoV-2 or Gamma variant five months after the second vaccine dose. Contrarily, SARS-CoV-2-recovered subjects retained considerable neutralizing activity against both viruses. We conclude that a single inactivated SARS-CoV-2 vaccine dose may be sufficient to induce protective antibody responses in individuals with previous history of SARS-CoV-2 infection. [ABSTRACT FROM AUTHOR]

Introdução: A doença causada pelo coronavírus de 2019 (COVID-19) é um problema global complexo, apresentando uma ampla gama de manifestações clínicas, desde casos assintomáticos até formas graves com risco de morte. Evidências epidemiológicas sugerem que as crianças tendem a apresentar formas mais leves da doença e uma menor taxa de mortalidade após a infecção pelo SARS-CoV-2, com exceção de uma síndrome inflamatória multissistêmica (MISC) associada a comorbidades em uma parcela relativamente pequena de crianças. Objetivo: Investigar as diferenças de resposta imune celular e humoral entre crianças e adultos com COVID-19, com o intuito de identificar fatores que possam contribuir para essa variação na sintomatologia. Método: Realizamos uma caracterização minuciosa do plasma e das células mononucleares de sangue periférico (PBMCs) em pacientes adultos e pediátricos com COVID-19, coletados em três momentos diferentes: durante a fase aguda da doença e após três e seis meses. Usando citometria de fluxo com múltiplos parâmetros, identificamos 78 subtipos diferentes de células imunes e analisamos um conjunto de dados extenso, totalizando 38.670 pontos, incluindo anticorpos IgA e IgG anti-SARS-CoV-2 e a frequência de células T efetoras específicas. Resultados: Nossos resultados revelaram diferenças significativas na cinética e no perfil de respostas de memória entre crianças e adultos. Vimos que, durante a fase aguda da infecção, as crianças e os adultos exibiram semelhanças e diferenças em suas respostas imunes, que pudemos distinguir por meio da Análise de Componentes Principais (PCA) e de clusterização hierárquica. Crianças também possuem altos títulos virais e produzem uma resposta imune forte, mas diferente para SARS-CoV-2 quando comparado com adultos. No momento de diagnóstico, crianças apresentaram altas frequências de células T CD8+ que produzem TNF em resposta a peptídeos da proteína N, enquanto a resposta de adultos com doença leve ou moderada foi baixa. Essa resposta foi reduzida em todos os adultos, que apresentam mais células T específicas para a proteína S. O estudo sequencial mostra que as crianças apresentam um aumento de títulos de IgG e IgA para N, mas não para a proteína S. A análise imparcial de tSNE demonstrou que em crianças, a resposta anti-N de células T CD8+TNF+ evoluiu para células T CD8+ de memória efetora e terminalmente diferenciada (EMRA), em apenas 3 meses, dominando a população de memória T, 6 meses após a infecção inicial. Essa resposta se correlaciona com anticorpos anti-N, mas não com anti-S. Todos os grupos analisados produziram anticorpos neutralizantes para a variante original, no entanto, foi vista uma perda de potencial de neutralização contra variantes de preocupação (VOCs). Conclusão: Nossos resultados sugerem que a proteção da doença e a reinfecção por VOCs pode ser funcionalmente diferente. Eles mostram a importância de se vacinar crianças, que permanecem sob risco apesar de já terem sido previamente infectadas. [ABSTRACT FROM AUTHOR]

Even after two years of the pandemic, a completely effective treatment against SARS-CoV-2 has not yet been established. Considering this fact and the emergence of successive new viral variants, the development of therapies based on natural polyclonal antibodies recovered from convalescent plasma remains relevant. This study presents a comparison between different methods of screening antibodies in samples of 41 individuals previously diagnosed with COVID-19. We found a significant correlation between Abbot Architect anti-SARS-CoV-2 IgG and Abbott Allinity SARS-CoV-2 IgG II Quantitative assay intensity of reactivity and neutralizing antibody (nAb) titers. Thus, we propose an initial antibody screening with IgG anti-N Abbott Architect test, with an index of, for example, > 3.25 or SARS-CoV-2 IgG II Quantitative Abbott Allinity assay > 137.65 AU/mL as good predictors of Nab ≥ 1:80. For the quantitative method, this threshold demonstrated a 100 % sensitivity and 80 % specificity, with 97.3 % accuracy. An interesting observation was the increase in the neutralizing activity of the anti-SARS-CoV-2 antibodies with the longest interval between the end of the symptoms and the collection, demonstrating that the delay in plasma collection does not affect the achievement of adequate nAbs levels. These results demonstrate the possibility of using faster and more widely available commercial serological tests with a good correlation with viral neutralization tests in culture, allowing for optimized large-scale donor selection, which will be of utmost importance for the development of therapies such as hyperimmune immunoglobulin. • Commercial serological tests for anti-SARS-CoV-2 antibodies show good correlation with neutralizing antibodies in culture. • This study demonstrates accurate cut-off points in serological tests for the selection of donors with nAbs > 1:80. • We propose a strategy for the selection of donors that can be useful for the production of therapeutics on a large scale. [ABSTRACT FROM AUTHOR]