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Abstract This study compares the effects of virus-cell interactions among SARS-CoV-2 variants of concern (VOCs) isolated in Brazil in 2021, hypothesizing a correlation between cellular alterations and mortality and between viral load and transmissibility. For this purpose, reference isolates of Alpha, Gamma, Zeta, and Delta variants were inoculated into monolayers of Vero-E6 cells. Viral RNA was quantified in cell supernatants by RT‒PCR, and infected cells were analyzed by Transmission Electron Microscopy (TEM) for qualitative and quantitative evaluation of cellular changes 24, 48, and 72 hours postinfection (hpi). Ultrastructural analyses showed that all variants of SARS-CoV-2 altered the structure and function of mitochondria, nucleus, and rough endoplasmic reticulum of cells. Monolayers infected with the Delta variant showed the highest number of modified cells and the greatest statistically significant differences compared to those of other variants. Viral particles were observed in the cytosol and the cell membrane in 100 % of the cells at 48 hpi. Alpha showed the highest mean particle diameter (79 nm), and Gamma and Delta were the smallest (75 nm). Alpha and Gamma had the highest particle frequency per field at 48 hpi, while the same was observed for Zeta and Delta at 72 hpi and 24 hpi, respectively. The cycle threshold of viral RNA varied among the target protein, VOC, and time of infection. The findings presented here demonstrate that all four VOCs evaluated caused ultrastructural changes in Vero-E6 cells, which were more prominent when infection occured with the Delta variant.
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BACKGROUND The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) B.1.1.33-derived lineage named N.9 was described recently in Brazil and it's considered a potential variant of interest (VOI) due to the presence of E484K substitution at the receptor-binding domain (RBD) of the Spike (S) protein. OBJECTIVE To describe the first detection of variant N.9 in Rio de Janeiro State. METHODS SARS-CoV-2 N.9 was confirmed by quantitative reverse transcription polymerase chain reaction (qRT-PCR), whole-genome sequencing and phylogenetic analysis. FINDINGS Here, we report two SARS-CoV-2 N.9 lineage strains in Rio de Janeiro. One of them had only the E484K substitution of the six N.9 lineage-defining mutations. Other three strains pre-defined as N.9 have the same genomic profile. These four strains are grouped within the B.1.1.33 lineage and basal to the N.9 lineage in our phylogenetic analysis, and we call them "N.9-like/B.1.1.33 + E484K". MAIN CONCLUSIONS The phylogenetic analysis shows four independent introductions of N.9 in the state of Rio de Janeiro in October and December 2020, January and March 2021. SARS-CoV-2 N.9 dissemination in the Rio de Janeiro could have been limited by the emergence and dominance of other variants, mainly by the lineage P.2 VOI Zeta that emerged in the same period and co-circulated with N.9, as observed in the neighboring State of São Paulo.
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Humanos , SARS-CoV-2 , COVID-19 , Filogenia , Brasil , MutaciónRESUMEN
Human bocaviruses (HBoV) are mainly associated with respiratory and gastroenteric infections. These viruses belong to the family Parvoviridae, genus Bocaparvovirus and are classified in four subtypes (HBoV1-4). Recombination and point mutation have been described as basis of parvovirus evolution. In this study three viral sequences were obtained from positives HBoV sewage samples collected in two Uruguayan cities and were characterised by different methods as recombinant strains. This recombination event was localised in the 5' end of VP1 gene and the parental strains belonged to subtypes 3 and 4. These three Uruguayan strains are identical at the nucleotide sequences in the analysed genome region of the virus. As far as we known, this study represents the first detection of HBoV recombinants strains in the Americas.