Emergence of genotype III St. Louis encephalitis virus in the western United States potentially linked to a wetland in Argentina.

St. Louis encephalitis virus (SLEV) is endemic in the Americas and its transmission networks involve Culex mosquitoes and avian species. In 2015, a human encephalitis outbreak took place in Arizona and California, indicating the re-emergence of this pathogen in the US. Viral strains isolated in that outbreak belong to genotype III SLEV previously detected only in South America. In this study, genotype III SLEV was detected in mosquitoes collected in Mar Chiquita Lagoon (Córdoba, Argentina), an overwintering site for numerous migratory bird species. The genotype III SLEV sequence detected in this site shares the closest known ancestor with those introduced in Arizona in 2015. Our results highlight the potential significance of wetlands as key sites for arbovirus maintenance and emergence.

Survival-based CRISPR genetic screens across a panel of permissive cell lines identify common and cell-specific SARS-CoV-2 host factors.

SARS-CoV-2 depends on host cell components for infection and replication. Identification of virus-host dependencies offers an effective way to elucidate mechanisms involved in viral infection and replication. If druggable, host factor dependencies may present an attractive strategy for anti-viral therapy. In this study, we performed genome wide CRISPR knockout screens in Vero E6 cells and four human cell lines including Calu-3, UM-UC-4, HEK-293 and HuH-7 to identify genetic regulators of SARS-CoV-2 infection. Our findings identified only ACE2, the cognate SARS-CoV-2 entry receptor, as a common host dependency factor across all cell lines, while other host genes identified were largely cell line specific, including known factors TMPRSS2 and CTSL. Several of the discovered host-dependency factors converged on pathways involved in cell signalling, immune-related pathways, and chromatin modification. Notably, the chromatin modifier gene KMT2C in Calu-3 cells had the strongest impact in preventing SARS-CoV-2 infection when perturbed.

Identifying cell receptors for the nanoparticle protein corona using genome screens.

Nanotechnology provides platforms to deliver medical agents to specific cells. However, the nanoparticle's surface becomes covered with serum proteins in the blood after administration despite engineering efforts to protect it with targeting or blocking molecules. Here, we developed a strategy to identify the main interactions between nanoparticle-adsorbed proteins and a cell by integrating mass spectrometry with pooled genome screens and Search Tool for the Retrieval of Interacting Genes analysis. We found that the low-density lipoprotein (LDL) receptor was responsible for approximately 75% of serum-coated gold nanoparticle uptake in U-87 MG cells. Apolipoprotein B and complement C8 proteins on the nanoparticle mediated uptake through the LDL receptor. In vivo, nanoparticle accumulation correlated with LDL receptor expression in the organs of mice. A detailed understanding of how adsorbed serum proteins bind to cell receptors will lay the groundwork for controlling the delivery of nanoparticles at the molecular level to diseased tissues for therapeutic and diagnostic applications.

Melatonin protects gingival mesenchymal stem cells and promotes differentiation into osteoblasts.

Melatonin (MEL) has antioxidant properties and participates in osteogenic differentiation. In periodontitis, in which increased oxidative stress and bone resorption are involved, mesenchymal stem cells derived from the gingiva (GMSCs) combined with MEL could be relevant for osteogenic regeneration. In this study, we studied the antioxidant and differentiating effect of MEL on an in vitro system of GMSCs. Primary culture of GMSCs from Wistar rats was developed to evaluate differentiation into osteoblasts with an appropriate medium with or without MEL. Marker genes of mesenchymal stem cells by real time-polymerase chain reaction, clonogenic capacity, and cell migration after wound assay were used to characterize GMSCs as mesenchymal stem cells. Alkaline phosphatase activity and the alizarin red technique were used to evaluate osteogenic activity and differentiation. MEL increased alkaline phosphatase activity and alizarin red values, promoting osteogenic differentiation. Besides this, MEL protected GMSCs in a model of cellular damage related to oxidative stress, returning viability to baseline. MEL was more effective in promoting and protecting GMSCs by the production of osteogenic cells when oxidative stress is present. This evidence supports the use of MEL as a novel bone-regenerative therapy in periodontal diseases.

First evidence of enterovirus A71 and echovirus 30 in Uruguay and genetic relationship with strains circulating in the South American region.

Human enteroviruses (EVs) comprise more than 100 types of coxsackievirus, echovirus, poliovirus and numbered enteroviruses, which are mainly transmitted by the faecal-oral route leading to diverse diseases such as aseptic meningitis, encephalitis, and acute flaccid paralysis, among others. Since enteroviruses are excreted in faeces, wastewater-based epidemiology approaches are useful to describe EV diversity in a community. In Uruguay, knowledge about enteroviruses is extremely limited. This study assessed the diversity of enteroviruses through Illumina next-generation sequencing of VP1-amplicons obtained by RT-PCR directly applied to viral concentrates of 84 wastewater samples collected in Uruguay during 2011-2012 and 2017-2018. Fifty out of the 84 samples were positive for enteroviruses. There were detected 27 different types belonging to Enterovirus A species (CVA2-A6, A10, A16, EV-A71, A90), Enterovirus B species (CVA9, B1-B5, E1, E6, E11, E14, E21, E30) and Enterovirus C species (CVA1, A13, A19, A22, A24, EV-C99). Enterovirus A71 (EV-A71) and echovirus 30 (E30) strains were studied more in depth through phylogenetic analysis, together with some strains previously detected by us in Argentina. Results unveiled that EV-A71 sub-genogroup C2 circulates in both countries at least since 2011-2012, and that the C1-like emerging variant recently entered in Argentina. We also confirmed the circulation of echovirus 30 genotypes E and F in Argentina, and reported the detection of genotype E in Uruguay. To the best of our knowledge this is the first report of the EV-A71 C1-like emerging variant in South-America, and the first report of EV-A71 and E30 in Uruguay.

Environmental Surveillance through Next-Generation Sequencing to Unveil the Diversity of Human Enteroviruses beyond the Reported Clinical Cases.

The knowledge about circulation of Human Enteroviruses (EVs) obtained through medical diagnosis in Argentina is scarce. Wastewater samples monthly collected in Córdoba, Argentina during 2011-2012, and then in 2017-2018 were retrospectively studied to assess the diversity of EVs in the community. Partial VP1 gene was amplified by PCR from wastewater concentrates, and amplicons were subject of next-generation sequencing and genetic analyses. There were 41 EVs detected, from which ~50% had not been previously reported in Argentina. Most of the characterized EVs (60%) were detected at both sampling periods, with similar values of intratype nucleotide diversity. Exceptions were enterovirus A71, coxsackievirus B4, echovirus 14, and echovirus 30, which diversified in 2017-2018. There was a predominance of types from EV-C in 2017-2018, evidencing a common circulation of these types throughout the year in the community. Interestingly, high genetic similarity was evidenced among environmental strains of echovirus 30 circulating in 2011-2012 and co-temporal isolates obtained from patients suffering aseptic meningitis in different locations of Argentina. This study provides an updated insight about EVs circulating in an important region of South America, and suggests a valuable role of wastewater-based epidemiology in predicting outbreaks before the onset of cases in the community.

Molecular survey of flaviviruses and orthobunyaviruses in Amblyomma spp. ticks collected in Minas Gerais, Brazil / Investigação molecular de flavivírus e orthobunyaviruses em carrapatos do gênero Amblyomma spp. coletados em Minas Gerais, Brasil

Abstract Due to anthropic environmental changes, vector-borne diseases are emerging worldwide. Ticks are known vectors of several pathogens of concern among humans and animals. In recent decades, several examples of tick-borne emerging viral diseases have been reported (Crimean Congo hemorrhagic fever virus, Powassan virus, encephalitis virus, heartland virus, severe fever with thrombocytopenia syndrome virus). Unfortunately, few studies addressing the presence of viruses in wild ticks have been carried out in South America. With the aim of detecting flaviviruses and orthobunyaviruses in ticks, we carried out molecular detection in wild ticks collected in the state of Minas Gerais, Brazil. No Flavivirus-positive ticks were detected; however, we detected activity of Orthobunyavirus in 8 Amblyomma tick specimens. One of those individuals was positive for Bunyamwera orthobunyavirus, which represents the first report of this virus among ticks in South America. Further studies related to the ecology of zoonotic diseases are needed to increase knowledge of this topic, including attempts at viral isolation, full genome sequencing and biological characterization. In this way, we will obtain a better picture of the real risk of ticks as a vector for viral diseases for humans and animals on our continent, where no tick-borne viral disease is known to occur.

Resumo Alterações ambientais causadas pelo homem têm levado à emergência de doenças transmitidas por vetores no mundo. Carrapatos são vetores conhecidos de vários patógenos de importância médica e veterinária, tendo sido reportado nas últimas décadas um grande número de enfermidades virais emergentes transmitidas por eles (vírus da Febre Hemorrágica da Crimeia-Congo, vírus Powassan, vírus da Encefalite, vírus Heartland e vírus da Síndrome da Febre Trombocitopênica Severa). Infelizmente, poucos estudos envolvendo a pesquisa de vírus em carrapatos foram conduzidos na América do Sul até o momento, e nas últimas décadas um elevado número de enfermidades virais emergentes transmitidas por estes artrópodes foi relatado. Com o objetivo de investigar a presença de flavivírus e orthobunyavírus em carrapatos, foi conduzida uma análise molecular em espécimes coletados no estado de Minas Gerais, Brasil. Em nenhum carrapato foi detectada a presença de Flavivirus, no entanto, em 8 espécimes do gênero Amblyomma, foi detectada a presença de Orthobunyavirus, dos quais um espécime foi positivo para Bunyamwera orthobunyavirus. Novos estudos relacionados à ecologia de doenças zoonóticas, incluindo tentativas de isolamento viral, sequenciamento completo do genoma e caracterização biológica, são necessários. Desta forma, será possível ter uma base sobre os riscos da transmissão de vírus patogênicos por carrapatos em nosso continente, uma vez que até agora isso é desconhecido.

Molecular survey of flaviviruses and orthobunyaviruses in Amblyomma spp. ticks collected in Minas Gerais, Brazil.

Due to anthropic environmental changes, vector-borne diseases are emerging worldwide. Ticks are known vectors of several pathogens of concern among humans and animals. In recent decades, several examples of tick-borne emerging viral diseases have been reported (Crimean Congo hemorrhagic fever virus, Powassan virus, encephalitis virus, heartland virus, severe fever with thrombocytopenia syndrome virus). Unfortunately, few studies addressing the presence of viruses in wild ticks have been carried out in South America. With the aim of detecting flaviviruses and orthobunyaviruses in ticks, we carried out molecular detection in wild ticks collected in the state of Minas Gerais, Brazil. No Flavivirus-positive ticks were detected; however, we detected activity of Orthobunyavirus in 8 Amblyomma tick specimens. One of those individuals was positive for Bunyamwera orthobunyavirus, which represents the first report of this virus among ticks in South America. Further studies related to the ecology of zoonotic diseases are needed to increase knowledge of this topic, including attempts at viral isolation, full genome sequencing and biological characterization. In this way, we will obtain a better picture of the real risk of ticks as a vector for viral diseases for humans and animals on our continent, where no tick-borne viral disease is known to occur.

Environmental Surveillance of Human Enteroviruses in Córdoba City, Argentina: Prevalence and Detection of Serotypes from 2009 to 2014.

Environmental surveillance is an effective approach to investigate the circulation of human enteroviruses (EVs) in the population. EVs excreted by patients who present diverse clinical syndromes can remain infectious in the environment for several weeks, and limited data on circulating environmental EVs are available. A 6-year (2009-2014) surveillance study was conducted to detect non-polio enteroviruses (NPEVs) in the urban sewage of Cordoba city, Argentina. Echovirus 6 (E-6) was the most prevalent (28%), followed by E-14 (17%), E-16 (14%), Coxsackievirus (CV) A9 (11%), E-20 (9%), and CVA24 (6%). Other minority serotypes (E-7, E-13, E-21, E-25, and CVB4) were found, which together represented 14% of the total. In the absence of a systematic EV disease surveillance system, the detection and characterization of sewage-borne NPEVs will help us better understand the changes in EV disease trends and the epidemic background of circulating EVs, which could help interpret the EV trends and warn of future outbreaks in this area.

Environmental Surveillance of Enteroviruses in Central Argentina: First Detection and Evolutionary Analyses of E14.

Environmental surveillance is an effective approach to investigate the circulation of human enteroviruses in the population. Enteroviruses E14, CVA9, E-6, E16, E20, E25, E13, and CVA24 were detected in sewage and a watercourse in central Argentina. E14 was the most frequent serotype and was found for the first time in environmental samples in our region. Phylogenetic and coalescence analyses showed at least two recent introduction events.

Changing epidemiology of hepatitis C virus genotypes in the central region of Argentina.

The aim of this study was to analyze the prevalence of hepatitis C virus (HCV) genotypes in Córdoba province, Argentina, over a 12-year period and to study the changes at the molecular level. The HCV genotype was determined in 357 HCV-infected patients, and the phylogeny and demographic reconstruction for HCV-1 was assessed. A significant reduction in HCV-2 prevalence with respect to HCV-1 in Córdoba after 2003 was observed. These findings are consistent with the epidemiological changes observed in South America. Nevertheless, the consequences of these changes remain to be elucidated.

Genetic and evolutionary characterization of Venezuelan equine encephalitis virus isolates from Argentina.

Venezuelan equine encephalitis viruses (VEEV) are emerging pathogens of medical and veterinary importance circulating in America. Argentina is a country free from epizootic VEEV activity, with circulation of enzootic strains belonging to Rio Negro virus (RNV; VEEV subtype VI) and Pixuna virus (PIXV, VEEV subtype IV). In this work, we aim to report the sequencing and phylogenetic analyses of all Argentinean VEE viruses, including 7 strains previously isolated from mosquitoes in 1980, 5 sequences obtained from rodents in 1991 and 11 sequences amplified from mosquitoes between 2003 and 2005. Two genomic regions, corresponding to the non-structural protein 4 (nsP4) and the protein E3/E2 (PE2) genes were analyzed, but only 8 samples could be amplified in the last one (longer and more variable fragment of 702 bp). For both genomic fragments, phylogenetic trees showed the absence of lineages within RNV group, and a close genetic relationship between Argentinean strains and the prototype strain BeAr35645 for PIXV clade. The analysis of nsP4 gene opens the possibility to propose a possible geographic clustering of strains within PIXV group (Argentina and Brazil). Coalescent analysis performed on RNV sequences suggested a common ancestor of 58.3 years (with a 95% highest posterior density [HPD] interval of 16.4-345.7) prior to 1991 and inferred a substitution rate of 9.8×10(-5)substitutions/site/year, slightly lower than other enzootic VEE viruses. These results provide, for the first time, information about genetic features and variability of all VEEVs detected in Argentina, creating a database that will be useful for future detections in our country. This is particularly important for RNV, which has indigenous circulation.

Spreading of hepatitis C virus subtypes 1a and 1b through the central region of Argentina.

The recent history of the hepatitis C virus (HCV) subtypes 1a and 1b in the central region of Argentina is hypothesized by phylogeographic reconstruction using coalescent based Bayesian analyses. Direct partial E2 sequences from HCV 1a and 1b infected patients attending different health-care centers of the country were analyzed. The inferred date of the most recent common ancestor (tMRCA) for HCV-1a was: 1962 (between 1943 and 1977) and for HCV-1b was earlier: 1929 (between 1895 and 1953). Diverse ancestral populations were inferred from both subtypes in Córdoba and in Buenos Aires cities and after that, HCV spread within and between larger cities and to other smaller cities. The analyses suggested that HCV-1b was dispersed first and it is currently in a stationary phase whereas HCV-1a was dispersed latter and it is still in a growth phase. Finally, as it was observed in the developed countries, while the transmission of HCV-1b appears to have been somehow prevented, the HCV-1a may still represent a concern in the public health. Further work should be carried out to address their current transmission rate (and its main transmission route) in the Argentinean population.

Determinants of immunological and virological responses to antiretroviral therapy amongst HIV-infected adults in central Argentina: negative influence of hepatitis C infection.

BACKGROUND: The purpose of this study was to update the epidemiological data on the prevalence of coinfection with hepatitis C virus (HCV) and HIV, and to identify whether specific clinical and epidemiological factors influenced the response of HIV-positive adults to highly active antiretroviral therapy (HAART). METHODS: This retrospective observational cohort study of 238 HIV-infected patients evaluated the effect of different epidemiological and clinical parameters (including HCV coinfection) on therapy response among HIV-infected adults initiating HAART. Multiple logistic regression models were used to identify factors associated with therapy response and estimated risk coefficients. RESULTS: Seroprevalence of HCV infection in this population was 26% (62/238). We did not observe a significant association between immunological or virological response relating to patient gender or HAART regimen. However, this analysis showed that HCV serological status, age at HIV diagnosis, duration of treatment and WHO clinical stage of AIDS (<200 CD4 cells/ml independently of viral load either < or > to 100,000 copies/ml), were significantly associated with immunological and virological responses to HAART. CONCLUSIONS: These results show further evidence that hepatitis C serostatus is associated with a reduced response to HAART.

Hepatitís C en Córdoba: implicancías de la coínfección HIV/HCV y cambíos locales en el perfil epidemiológico molecular / Hepatitis C in Córdoba: implications of HIV / HCV coinfection and local changes in the molecular epidemiological profile

El virus de la Hepatitis C es considerado una de las principales causas de hepatitis crónica, cirrosis hepática y cáncer hepático. La coinfección con HIV acelera la progresión de la enfermedad hepática, aumenta la efectividad de la transmisión de HCV por vías no parenterales y ha sido asociada a la disminución de la efectividad de la terapia HAART. A nivel mundial, la distribución y el patrón molecular de HCV son marcadamente heterogéneos y se modifican continuamente debido tanto a cambios culturales, asociados a nuevas conductas de riesgo, como a movimientos poblacionales. El objetivo del presente trabajo fue estudiar la prevalencia y la diversidad genética de la infección por HCV en individuos coinfectados con HIV de Córdoba, evaluar su influencia en la terapia antiretroviral (HAART) y en la transmisión de HCV, y detectar posibles cambios en el patrón regional de distribución de genotipos en los últimos 10 años. En este estudio se incluyeron las siguientes muestras obtenidas de pacientes de Córdoba: a) 349 muestras de suero obtenidas de individuos crónicamente infectados por HCV colectados entre 1999-2009; b) 86 sueros de pacientes coinfectados HCV/HIV obtenidos de un total de 558 pacientes HIV+, colectados en dos periodos entre 2003-2007; y c) 37 muestras de fluidos biológicos de pacientes monoinfectados (n=21) y coinfectados HCV/HIV (n=16) [hisopado cervical (n=16), saliva (n=37), plasma seminal (n=21) y células mononucleares de sangre periférica (n=37)].Para la detección molecular de HCV se utilizó RT-nested PCR de la región 5’ no codificante (5’ NC), y para la caracterización genómica y posterior análisis filogenético y evolución viral, se amplificaron y secuenciaron las regiones no estructural 5B y E1/E2.

Summary: The hepatitis C virus (HCV) is considered one of the major causes of chronic hepatitis, cirrhosis and liver cancer. Co-infection with HIV accelerates the progression of liver disease, increases the efficiency of transmission of HCV by non-parental routes and has been associated with the decrease in the effectiveness of HAART. Worldwide, HCV distribution and its molecular pattern are markedly heterogeneous and are continuously changing, due to cultural changes, associated to new risk behaviors, as well as population movements. The aim of this work was to study the prevalence and genetic diversity of HCV infection in HIV co-infected individuals of Córdoba, evaluate its influence on antiretroviral therapy (HAART) and in HCV transmission, and identify possible changes in HCV genotype distribution pattern of Córdoba in the last 10 years.This study included the following samples obtained from patients of Córdoba: a) 349 serum samples from chronically infected individuals collected between 1999-2009; b) 86 serum samples from HCV/HIV co-infected patients obtained from a total of 558 HIV+ patients, collected in 2 periods between 2003-2007; and c) 37 biological fluid samples of HCV moninfected (n=21) and HCV/HIV co-infected individuals (n=16) [cervical swab (n=16), saliva (n=37), seminal plasma (n=21) and peripheral blood mononuclear cells (n=37)]. RT-nested PCR of the 5’ non-coding region (5’ NC) was used for HCV molecular detection. For genomic characterization and subsequent phylogenetic and viral evolution analysis, non-structural 5B and E1/E2 genomic regions were amplified and sequenced.

Hepatitís C en Córdoba: implicancías de la coínfección HIV/HCV y cambíos locales en el perfil epidemiológico molecular / Hepatitis C in Córdoba: implications of HIV / HCV coinfection and local changes in the molecular epidemiological profile

El virus de la Hepatitis C es considerado una de las principales causas de hepatitis crónica, cirrosis hepática y cáncer hepático. La coinfección con HIV acelera la progresión de la enfermedad hepática, aumenta la efectividad de la transmisión de HCV por vías no parenterales y ha sido asociada a la disminución de la efectividad de la terapia HAART. A nivel mundial, la distribución y el patrón molecular de HCV son marcadamente heterogéneos y se modifican continuamente debido tanto a cambios culturales, asociados a nuevas conductas de riesgo, como a movimientos poblacionales. El objetivo del presente trabajo fue estudiar la prevalencia y la diversidad genética de la infección por HCV en individuos coinfectados con HIV de Córdoba, evaluar su influencia en la terapia antiretroviral (HAART) y en la transmisión de HCV, y detectar posibles cambios en el patrón regional de distribución de genotipos en los últimos 10 años. En este estudio se incluyeron las siguientes muestras obtenidas de pacientes de Córdoba: a) 349 muestras de suero obtenidas de individuos crónicamente infectados por HCV colectados entre 1999-2009; b) 86 sueros de pacientes coinfectados HCV/HIV obtenidos de un total de 558 pacientes HIV+, colectados en dos periodos entre 2003-2007; y c) 37 muestras de fluidos biológicos de pacientes monoinfectados (n=21) y coinfectados HCV/HIV (n=16) [hisopado cervical (n=16), saliva (n=37), plasma seminal (n=21) y células mononucleares de sangre periférica (n=37)].Para la detección molecular de HCV se utilizó RT-nested PCR de la región 5Æ no codificante (5Æ NC), y para la caracterización genómica y posterior análisis filogenético y evolución viral, se amplificaron y secuenciaron las regiones no estructural 5B y E1/E2.(AU)

Summary: The hepatitis C virus (HCV) is considered one of the major causes of chronic hepatitis, cirrhosis and liver cancer. Co-infection with HIV accelerates the progression of liver disease, increases the efficiency of transmission of HCV by non-parental routes and has been associated with the decrease in the effectiveness of HAART. Worldwide, HCV distribution and its molecular pattern are markedly heterogeneous and are continuously changing, due to cultural changes, associated to new risk behaviors, as well as population movements. The aim of this work was to study the prevalence and genetic diversity of HCV infection in HIV co-infected individuals of Córdoba, evaluate its influence on antiretroviral therapy (HAART) and in HCV transmission, and identify possible changes in HCV genotype distribution pattern of Córdoba in the last 10 years.This study included the following samples obtained from patients of Córdoba: a) 349 serum samples from chronically infected individuals collected between 1999-2009; b) 86 serum samples from HCV/HIV co-infected patients obtained from a total of 558 HIV+ patients, collected in 2 periods between 2003-2007; and c) 37 biological fluid samples of HCV moninfected (n=21) and HCV/HIV co-infected individuals (n=16) [cervical swab (n=16), saliva (n=37), seminal plasma (n=21) and peripheral blood mononuclear cells (n=37)]. RT-nested PCR of the 5Æ non-coding region (5Æ NC) was used for HCV molecular detection. For genomic characterization and subsequent phylogenetic and viral evolution analysis, non-structural 5B and E1/E2 genomic regions were amplified and sequenced.(AU)

Specific detection of all members of the Venezuelan Equine Encephalitis complex: development of a RT-Nested PCR.

Venezuelan Equine Encephalitis (VEE) complex belongs to alphavirus genus in the family Togaviridae. Several species of this complex are pathogenic to humans. VEE infections can produce severe or mild disease, and many cases remain undiagnosed. A specific and sensitive reverse transcriptase nested polymerase chain reaction (RT-Nested PCR) method was developed for the detection of all VEE subtypes, including Rio Negro Virus (RNV) (subtype VI), which circulates only in Argentina. Degenerated primers were designed and thermal cycling parameters were standardized. This technique is suitable for rapid and specific detection of these viruses, and may be useful for diagnosis and surveillance.

First detection of Rio Negro virus (Venezuelan equine encephalitis complex subtype VI) in Córdoba, Argentina.

Rio Negro virus (RNV) (Venezuelan equine encephalitis subtype VI) circulates only in Argentina; in northern provinces, isolates have been obtained from mosquitoes and rodents since 1980 and have been associated with acute febrile illness in humans. However, no studies of RNV have been performed in the central area of the country. We carried out molecular and serological detection of RNV in Córdoba, a province of the central part of the country, in mosquitoes and humans, respectively. One mosquito pool tested positive for alphavirus RNA by reverse transcriptase-nested polymerase chain reaction (RT-nested PCR). Subsequent sequencing determined that this alphavirus grouped with RNV. Serological studies detected antibodies to RNV in one human serum sample, which was obtained during the same period that RNV was detected using the aforementioned molecular methods. This is the first report of RNV circulation in the central area of Argentina, indicating an expansion of its original distribution. These results highlight the importance of strengthening surveillance procedures in endemic areas, as well as in new regions where RNV may emerge.

First detection of Rio Negro virus (Venezuelan equine encephalitis complex subtype VI) in Córdoba, Argentina

Rio Negro virus (RNV) (Venezuelan equine encephalitis subtype VI) circulates only in Argentina; in northern provinces, isolates have been obtained from mosquitoes and rodents since 1980 and have been associated with acute febrile illness in humans. However, no studies of RNV have been performed in the central area of the country. We carried out molecular and serological detection of RNV in Córdoba, a province of the central part of the country, in mosquitoes and humans, respectively. One mosquito pool tested positive for alphavirus RNA by reverse transcriptase-nested polymerase chain reaction (RT-nested PCR). Subsequent sequencing determined that this alphavirus grouped with RNV. Serological studies detected antibodies to RNV in one human serum sample, which was obtained during the same period that RNV was detected using the aforementioned molecular methods. This is the first report of RNV circulation in the central area of Argentina, indicating an expansion of its original distribution. These results highlight the importance of strengthening surveillance procedures in endemic areas, as well as in new regions where RNV may emerge.

Immunoglobulin G subclasses in antibody responses to St. Louis encephalitis virus infections.

The aim of this study was to recognize the specific antiviral response patterns of IgG1, IgG2, IgG3 and IgG4 subclasses, elicited during St. Louis encephalitis virus (SLEV) infection in humans. Eighty-five samples of human sera from 44 patients with SLEV infection were obtained between days 1 and 365 or later, after onset of the disease. These samples were processed by immunofluorescence assay for detection of IgG1-, IgG2-, IgG3- and IgG4-specific antibodies. We demonstrate the presence of all isotypes of IgG for more than a year in patients infected with SLEV. However; isotype IgG1 was present at the highest titers, with a peak between days 8 and 30 after onset of the disease.