SARS-CoV-2 is considered a global emergency, resulting in an exacerbated crisis in the health public in the world. Although there are advances in vaccine development, it is still not available for many countries. On the other hand, an immunological response that mediates protective immunity or indicates that predict disease outcome in SARS-CoV-2 infection remains undefined. This work aimed to assess the antibody levels, avidity, and subclasses of IgG to RBD protein, in symptomatic patients with severe and mild forms of COVID-19 in Brazil using an adapted in-house RBD-IgG ELISA. The RDB IgG-ELISA showed 100% of specificity and 94.3% of sensibility on detecting antibodies in the sera of hospitalized patients. Patients who presented severe COVID-19 had higher anti-RBD IgG levels compared to patients with mild disease. Additionally, most patients analyzed displayed low antibody avidity, with 64.4% of the samples of patients who recovered from the disease and 84.6% of those who died in this avidity range. Our data also reveals an increase of IgG1 and IgG3 levels since the 8th day after symptoms onset, while IgG4 levels maintained less detectable during the study period. Surprisingly, patients who died during 8-14 and 15-21 days also showed higher anti-RBD IgG4 levels in comparison with the recovered (P < 0.05), suggesting that some life-threatening patients can elicit IgG4 to RBD antibody response in the first weeks of symptoms onset. Our findings constitute the effort to clarify IgG antibodies' kinetics, avidity, and subclasses against SARS-CoV-2 RDB in symptomatic patients with COVID-19 in Brazil, highlighting the importance of IgG antibody avidity in association with IgG4 detection as tool laboratory in the follow-up of hospitalized patients with more significant potential for life-threatening.

Foram utilizadas 26 ovelhas Santa Inês cíclicas. No tratamento 1, controle (n= 8), utilizou-se esponja com MAP por 14 dias e 300UI eCG (D14). No tratamento 2 (n= 9) foi empregado o protocolo Ovsynch: 25 µg de GnRH (D0), 37,5 µg de PGF2a (D7) e 25 µg de GnRH (D9). No tratamento 3 (n= 9) utilizou-se o protocolo Ovsynch adaptado, antecipando em 2 dias as aplicações de PGF2a e GnRH. A detecção de estro foi feita com auxílio de rufiões tendo início no T1, 12 h após o término do tratamento e no T2 e T3, imediatamente após a aplicação de PGF2a. Todas as ovelhas em estro foram cobertas duas vezes com intervalo de 12 horas. A taxa de prenhez (TP) foi avaliada por ultra-sonografia, 30 dias após a última cobertura. Do total de fêmeas sincronizadas, 88,46% em média, apresentaram estro, não evidenciando diferença entre os grupos (p>0,05). O intervalo entre o final do tratamento e o início do estro foi maior (p