SARS-CoV-2-specific humoral response was analyzed over time in a group of healthcare workers with or without exposure to SARS-CoV-2, who underwent vaccination with BBIBP-CorV (Sinopharm) vaccine in Argentina. Seroconversion rates in unexposed subjects after the first and second doses were 40% and 100%, respectively, showing a significant increase in antibody concentrations from dose 1 to dose 2 ( p < 0.0001). The highest antibody concentrations were found in younger subjects and women, remaining significantly associated in a multivariable linear regression model ( p = 0.005). A single dose of the BBIBP-CorV vaccine induced a strong antibody response in individuals with prior SARS-CoV-2infection, while a second dose did not increase this response. A sharp increase in antibody concentrations was observed following SARS-CoV-2 infection in those participants who became infected after the first and second doses ( p = 0.008). Individuals with SARS-CoV-2 exposure prior to vaccination showed significantly higher anti-spike IgG antibody levels, at all-time points, than those not exposed ( p < 0.001). Higher antibody titers were induced by a single dose in previously SARS-CoV-2 infected individuals than those induced in naïve subjects by two doses of the vaccine ( p < 0.0001). Three months after the second dose both groups showed a decline in antibody levels, being more abrupt in unexposed subjects. Overall, our results showed a trend towards lower antibody concentrations over time following BBIBP-CorV vaccination. Sex and age seem to influence the magnitude of the humoral response in unexposed subjects while the combination of exposure to SARS-CoV-2 plus vaccination, whatever the sequence of the events was, produced a sharp increase in antibody levels. Evaluation of the humoral responses over time and the analysis of the induction and persistence of memory B and T cell responses, are needed to assess long-term immune protection induced by BBIBP-CorV vaccine.

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The fast spread of COVID-19 has overcrowded Public Health Systems facilities in major countries due to the large number of seriously ill patients, particularly those requiring admission to intensive care units. Reducing viral load, along with other recommended epidemiological measures, such as social distancing and home confinement, can in time significantly help to reduce the infection R0 (Basic Reproductive Rate) and then mitigate disease burden. Early negativization or otherwise reduction of the viral load can potentially diminish disease severity, resulting in a better-controlled public health response, avoiding collapse of healthcare systems. Nitazoxanide, a widely used thiazolide approved by the FDA as an antiparasitic drug, also approved in Brazil for Norovirus and Rotavirus treatments, has an excellent safety record for a variety of indications. Nitazoxanide exhibits activity in vitro against MERS-CoV and other coronaviruses; and a specific antiviral effect (in micro molar doses) against SARS-CoV-2. The objective of this study was to evaluate the efficacy and safety of Nitazoxanide in reducing the SARS-COV 2 viral load within 7 days of treatment in respiratory samples from COVID-19-infected patients with mild to moderate disease, compared to placebo. An interim analysis showed that the ratio of patients with a viral load reduction ≥ 35% from baseline up to day 7 of treatment was significantly greater for Nitazoxanide compared to placebo (47.8% vs. 15.4%; Δ 34.6%; 95% CI: 64.7; 4.6: p = 0.037).

During the first months of SARS‐CoV‐2 evolution in a new host, contrasting hypotheses have been proposed about the way the virus has evolved and diversified worldwide. The aim of this study was to perform a comprehensive evolutionary analysis to describe the human outbreak and the evolutionary rate of different genomic regions of SARS‐CoV‐2. The molecular evolution in nine genomic regions of SARS‐CoV‐2 was analyzed using three different approaches: phylogenetic signal assessment, emergence of amino acid substitutions, and Bayesian evolutionary rate estimation in eight successive fortnights since the virus emergence. All observed phylogenetic signals were very low and tree topologies were in agreement with those signals. However, after four months of evolution, it was possible to identify regions revealing an incipient viral lineage formation despite the low phylogenetic signal, since fortnight 3. Finally, the SARS‐CoV‐2 evolutionary rate for regions nsp3 and S, the ones presenting greater variability, was estimated as 1.37 x 10 ‐3 and 2.19 x 10 ‐3 substitution/site/year, respectively. In conclusion, results from this work about the variable diversity of crucial viral regions and determination of the evolutionary rate are consequently decisive to understand essential features of viral emergence. In turn, findings may allow the first time characterization of the evolutionary rate of S protein, crucial for vaccine development. This article is protected by copyright. All rights reserved.

The spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become the main target for antiviral and vaccine development. Despite its relevance, e information is scarse about its evolutionary traces. The aim of this study was to investigate the diversification patterns of the spike for each clade of SARS-CoV-2 through different approaches. Two thousand and one hundred sequences representing the seven clades of the SARS-CoV-2 were included. Patterns of genetic diversifications and nucleotide evolutionary rate were estimated for the spike genomic region. The haplotype networks showed a star shape, where multiple haplotypes with few nucleotide differences diverge from a common ancestor. Four

Direct acting antiviral (DAA) therapy against hepatitis C virus (HCV) increases sustained virologic response rates. Nevertheless, drug resistance has occasionally been associated with failure to DAA. However, the information about the prevalence of NS5A and NS5B resistance-associated substitutions (RASs) in Argentina is very scarce. In this study, we determine the prevalence of NS5A and NS5B resistances to treatment in Argentinean DAA treatment-naïve patients chronically infected with genotype 1 (HCV-1). In this retrospective cross-sectional study, 108 HCV-1-infected patients were studied. RASs in NS5A and NS5B were analyzed by Sanger at baseline and phylogenetic analysis was performed. NS5A and NS5B RASs were detected in 25.8% and 6.3% of the analyzed sequences, respectively. The most frequent primary RASs for NS5A were L31M (7.5%) and Y93H (3.2%) and for NS5B was L159F (3.8%). No association between the presence of RASs and the outcome of DAA treatment was found in this study. Additionally, most of the Argentinean samples were randomly distributed among sequences around the world in the phylogenetic analysis. Only one significant Argentinean cluster was observed in both regions but without any particular RASs pattern. Baseline RASs in NS5A and NS5B were frequently observed in HCV-1-infected patients from Buenos Aires, Argentina but not related to treatment outcome. No clusters related to RASs transmission were observed in the phylogenetic analysis. The frequency of RASs detected in this study supports the need for more molecular epidemiology studies on RASs to adjust local treatment guidelines with the incorporation of autochthonous data. K E Y W O R D Sdirect-acting antiviral, hepatitis C virus, molecular epidemiology, therapy

The aim of this study was to assess the prevalence of hepatitis E virus (HEV) in a young population from the Northeast region of Argentina. Four hundred and twelve patients under 18 years old, from rural areas of Chaco Province, were tested for anti‐HEV immunoglobulin G (IgG) using enzyme‐linked immunosorbent assay. Anti‐HEV IgG antibodies were detected in 7 out of 412 patients, accounting for an overall 1.7% prevalence. HEV infection in developing countries is associated to lack of clean drinking water. Consequently, the seroprevalence observed in children in rural areas of Chaco, Argentina, where the access to tap water is less than 15%, was unexpectedly low.

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