The COVID-19 pandemic is the biggest public health threat facing the world today. Multiple vaccines have been approved; however, the emergence of viral variants such as the recent Omicron raises the possibility of booster doses to achieve adequate protection. In Brazil, the CoronaVac (Sinovac, Beijing, China) vaccine was used; however, it is important to assess the immune response to this vaccine over time. This study aimed to monitor the anti-SARS-CoV-2 antibody responses in those immunized with CoronaVac and SARS-CoV-2 infected individuals. Samples were collected between August 2020 and August 2021. Within the vaccinated cohort, some individuals had a history of infection by SARS-CoV-2 prior to immunization, while others did not. We analyzed RBD-specific and neutralizing-antibodies. Anti-RBD antibodies were detected in both cohorts, with a peak between 45–90 days post infection or vaccination, followed by a steady decline over time. In those with a previous history of COVID-19, a higher, longer, more persistent response was observed. This trend was mirrored in the neutralization assays, where infection, followed by immunization, resulted in higher, longer lasting responses which were conditioned on the presence of levels of RBD antibodies right before the vaccination. This supports the necessity of booster doses of CoronaVac in due course to prevent serious disease.

Objetivo: Estudo com abordagem teórico-experimental aplicada à expressão gênica de formas de DNA do DENV em células de mamíferos, comparada à presença de fragmentos oriundos de RNA viral descritos na literatura em células de artrópodes, experimentalmente infectadas pelo DENV. Metodologia: Trata-se de um estudo bilateral, de natureza teórico-experimental, com base na intervenção primária, realizado in vitro, sob uma abordagem técnica comparativa. Técnicas laboratoriais de expressão gênica por PCR convencional, procedimentos de verificação para análise e registros de dados da literatura foram obtidos e processados ​​no Laboratório de Biogênese Viral, vinculado ao Setor de Arbovirologia e Febres Hemorrágicas do Instituto Evandro Chagas. Resultados: A análise experimental indicou a presença de formas de DNA de DENV-4 em células infectadas persistentemente por inoculação a 72 hpi. Como função comparativa, as células C6 / 36 apresentaram sequências de DNA viral incorporadas em regiões de retrotransposons LTR, permitindo sugerir que a maioria dos eventos de integração são mediados por transcriptases reversas derivadas de retrotransposons. Conclusão: Diante dos resultados demonstrados, fica evidente a necessidade de estudos que caracterizem a capacidade do RNA viral de ser convertido em formas de DNA, bem como a influência dessa característica na permanência desses fragmentos após a infecção, para quais proteínas esses genes pertence, como esses genes modificam e interagem na replicação viral e a relação da patogenicidade e tropismo associada à plasticidade molecular da proteína pós-mutação, durante a replicação viral.

Introduction: The Mayaro virus (MAYV) is an arbovirus belonging to the Togaviridae family of the alphavirus genus, which is transmitted by hematophagous arthropods to vertebrate hosts, whereas non-human primates are considered primary reservoirs. Objective: To evaluate the expression of messenger RNAs (mRNA) of crucial proteins in the microRNA pathway and inflammatory cytokines in human cells during infection by the MAYV. Materials and Methods: Viral samples propagated in RD cell cultures. The RNAs were collected and extracted at predetermined times. The total RNA was then used to detect mRNA by PCR in real time (qRT-PCR). Results: the Mayaro virus RNA was verified in the cells during all the days of infection. The AgR2 mRNA protein dropped sharply by 2 dpi and 3 dpi. Conclusion: The present study demonstrated the reduction of proteins in infection with the Mayaro virus.

Objective: Evaluate the messenger RNAs (mRNA) PIWI proteins expression during infection with VDEN 4 in human hepatocyte cells. Materials and Methods: VDEN4 strain H778494 (JQ513335) was used, which was stored in Aedes albopictus cell culture (Clone C6 / 36) at the Arbovirology and Hemorrhagic Fevers section of the Evandro Chagas Institute. The techniques of cell cultures, stock (C6/36), inoculation, extraction, viral load quantification, RTqPCR and statistical analyzes were performed at the Viral Biogenesis Laboratory. Results: According to the results obtained, two cells (HepG2 and Huh7.5) demonstrated a higher level of viral replication at 72 hours post infection (hpi). The PIWI 2 target alter its mRNA expression during VDEN4 infection. The PIWI 4 target expression, was observed an altered expression in the infected cells. Thus, it was found that they are in different poles, while the viral load in the first three days showed high expression. The expression of mRNA was low in relation to the normal rate given by the uninfected cells. Conclusion: In our findings, it was observed that PIWI2 and 4 proteins have an inverse relationship to the viral infection process by VDEN4, when there is an increase in viral replication, these two proteins end up having a significant reduction in their expression. Probably, this reduction of expression is involved with the biogenesis process of apoptosis-regulating microRNAs.

Objective: Evaluate the miRNA-15 expression profile involved in cellular apoptotic regulation factors. Methodology: We used the H818308 Asian strain of ZIKV without neurological damage. The inoculations occurred in human embryonic kidney cells (HEK-293). After inoculation, samples were extracted for RT-qPCR quantification of viral RNA and miR-15. The level of activation of caspases 1, 3/7 and 8 of cells was performed using chemofluorescence. Results: The ZIKV infection alters the expression of genes and their regulators, affecting several cellular physiological processes such as apoptosis. Conclusion: Therefore, it is important to emphasize that renal progenitor cells (HEK-293) are susceptible to VZIK infection. The genetic deregulation resulting from infection directly affects important cellular processes such as apoptosis from the disordered miRNA-15 expression during the infection period.

The COVID-19 pandemic is the biggest public health threat facing the globe today. Multiple vaccines have been approved, however the emergence of viral variants such as the recent Omicron, raises the possibility of booster doses to achieve adequate protection. In Brazil, the CoronaVac (Sinovac) vaccine was used, however it’s important to assess the immune response to this vaccine over time. This study aimed to monitor the anti-SARS-CoV-2 antibody responses in those immunized with CoronaVac and SARS-CoV-2 infected individuals. Samples were collected between August 2020 and August 2021. Within the vaccinated cohort, some individuals had history of infection by SARS-CoV-2 prior to immunization and others not. We analyzed RBD-specific and neutralizing- antibodies. Anti-RBD antibodies were detected in both cohorts, with a peak between 45-90 days post infection or vaccination, followed by a steady decline over time. In those with previous history of COVID-19, a higher, longer, more persistent response was observed. This trend was mirrored in the neutralization assays, where infection followed by immunization resulted in higher, longer lasting responses which were conditioned on the presence of levels of RBD antibodies right before the vaccination. This supports the necessity of booster doses of CoronaVac in due course to prevent serious disease.