Delayed viral clearance despite high number of activated T cells during the acute phase in Argentinean patients with hantavirus pulmonary syndrome.

BACKGROUND: The hallmarks of HPS are increase of vascular permeability and endothelial dysfunction. Although an exacerbated immune response is thought to be implicated in pathogenesis, clear evidence is still elusive. As orthohantaviruses are not cytopathic CD8+ T cells are believed to be the central players involved in pathogenesis. METHODS: Serum and blood samples from Argentinean HPS patients were collected from 2014 to 2019. Routine white blood cell analyses, quantification and characterization of T-cell phenotypic profile, viral load, neutralizing antibody response and quantification of inflammatory mediators were performed. FINDINGS: High numbers of activated CD4+ and CD8+ T cells were found in all HPS cases independently of disease severity. We found increased levels of some proinflammatory mediators during the acute phase of illness. Nonetheless, viral RNA remained high, showing a delay in clearance from blood up to late convalescence, when titers of neutralizing antibodies reached a high level. INTERPRETATION: The high activated phenotypic profile of T cells seems to be unable to resolve infection during the acute and early convalescent phases, and it was not associated with the severity of the disease. Thus, at least part of the activated T cells could be induced by the dysregulated inflammatory response in an unspecific manner. Viral clearance seems to have been more related to high titers of neutralizing antibodies than to the T-cell response. FUNDING: This work was supported mainly by the Administración Nacional de Laboratorios e Institutos de Salud (ANLIS) "Dr. Carlos Malbrán". Further details of fundings sources is included in the appendix.

Emerging hantaviruses in Central Argentina: First case of Hantavirus Pulmonary Syndrome caused by Alto Paraguay virus, and a novel orthohantavirus in Scapteromys aquaticus rodent.

Orthohantaviruses are emerging rodent-borne pathogens that cause Hantavirus Pulmonary Syndrome in humans. They have a wide range of rodent reservoir hosts and are transmitted to humans through aerosolized viral particles generated by the excretions of infected individuals. Since the first description of HPS in Argentina, new hantaviruses have been reported throughout the country, most of which are pathogenic to humans. We present here the first HPS case infected with Alto Paraguay virus reported in Argentina. Until now, Alto Paraguay virus was considered a non-pathogenic orthohantavirus since it was identified in a rodent, Holochilus chacarius. In addition to this, with the goal of identifying potential hantavirus host species in the province of Santa Fe, we finally describe a novel orthohantavirus found in the native rodent Scapteromys aquaticus, which differed from other hantaviruses described in the country so far. Our findings implicate an epidemiological warning regarding these new orthohantaviruses circulating in Central Argentina as well as new rodent species that must be considered as hosts from now on.

Epidemiological description, case-fatality rate, and trends of Hantavirus Pulmonary Syndrome: 9 years of surveillance in Argentina.

Hantavirus pulmonary syndrome (HPS) is an endemic disease in Argentina, one of the most affected countries in the Americas. Andes virus (ANDV) is the main Orthohantavirus species causing HPS in Argentina. In this study, the geographical distribution, clinical presentation, and epidemiological features of HPS from all endemic regions of Argentina were analyzed. We focused on the clinical and epidemiological data from 533 HPS cases confirmed during the period 2009 to 2017 by the National Reference Laboratory for Hantavirus. A case-fatality rate of 21.4% was registered, and most of the cases presented a severe clinical picture requiring intensive care treatment (84%). Since HPS first detection in 1995 the case-fatality rate showed a general trend towards a decrease. After more than 22 years of experience in HPS diagnosis and surveillance, we discuss some possible factors implicated in this tendency. This clinical and epidemiological analysis gives a global perspective, being useful to detect trends and patterns, to update preventive actions at a national level, and evaluate their impact on public health.

Induction of protective immunity in a Syrian hamster model against a cytopathogenic strain of Andes virus.

Andes virus (ANDV) is responsible for the Hantavirus Pulmonary Syndrome cases in Argentina and neighboring countries, with moderate to high case-fatality rates. ANDV has some particular features, which make it unique among other members of the Hantavirus genus such as person-to-person transmission and causing a disease similar to Hantavirus Pulmonary Syndrome in the hamster as an animal model. The kinetics of replication in Vero E6 cells of an ANDV strain isolated in Argentina, called Andes/ARG, was studied. Cytopathic effect and the formation of clear plaques were observed and therefore Andes/ARG could be quantified by classic plaque assay. The Andes/ARG strain was found to be highly lethal in Syrian hamsters allowing experiments to demonstrate the protective potential of vaccines. A recombinant nucleocapsid protein of ANDV induced a long lasting antibody response and protective immunity against a homologous challenge, but to a lower extent against heterologous challenge by the Seoul virus.

Intrathecal antibody production in two cases of yellow fever vaccine associated neurotropic disease in Argentina.

During the period 2007-2008 several epizootics of Yellow fever with dead of monkeys occurred in southeastern Brasil, Paraguay, and northeastern Argentina. In 2008 after a Yellow fever outbreak an exhaustive prevention campaign took place in Argentina using 17D live attenuated Yellow fever vaccine. This vaccine is considered one of the safest live virus vaccines, although serious adverse reactions may occur after vaccination, and vaccine-associated neurotropic disease are reported rarely. The aim of this study was to confirm two serious adverse events associated to Yellow fever vaccine in Argentina, and to describe the analysis performed to assess the origin of specific IgM against Yellow fever virus (YFV) in cerebrospinal fluid (CSF). Both cases coincided with the Yellow fever vaccine-associated neurotropic disease case definition, being clinical diagnosis longitudinal myelitis (case 1) and meningoencephalitis (case 2). Specific YFV antibodies were detected in CSF and serum samples in both cases by IgM antibody-capture ELISA. No other cause of neurological disease was identified. In order to obtain a conclusive diagnosis of central nervous system (CNS) infection the IgM antibody index (AI(IgM) ) was calculated. High AI(IgM) values were found in both cases indicating intrathecal production of antibodies and, therefore, CNS post-vaccinal YFV infection could be definitively associated to YFV vaccination.

Partial genetic characterization of Seoul hantavirus in rats from Buenos Aires City, Argentina, and generation of a Seoul recombinant nucleoprotein antigen

Hemorrhagic fever with renal syndrome (HFRS) is a severe infectious disease characterized by fever, hemorrhage, renal impairment, and thrombocytopenia. At least seven hantaviruses cause HFRS: Hantaan, Seoul (SEOV) (distributed worldwide), Dobrava/Belgrade, Saaremaa, Amur, Thailand and Puumala. To investigate the epidemiology of HFRS and virus transmission in Argentina, we constructed a prokaryotic plasmid encoding the SEOV rNP, of 430 amino acids. After expression, the rNP was tested as an antigen for use in an enzyme-linked immunosorbent assay for infection diagnosis. To determine the current level of virus transmission in wild brown rats or Norway rats (Rattus norvegicus) captured in Buenos Aires City, Argentina, we tested tissues from rats that were determined to be serologically positive for the SEOV, and the viral genome were detected by RT-PCR using specific primers for two fragments of M segment-encoding Gn and Gc proteins. The viral genome was detected in 11 of 21 seropositive rats (52.4 per cent) captured in two parklands. Sequence analysis of a 333-nt region of the Gc-encoding M segment revealed 97 per cent and 96 per cent identity with strains of SEOV from Baltimore and Brazil, respectively. Our genetic data confirm a very low diversity among SEOV virus strains...

A febre hemorrágica com síndrome renal (FHSR) é uma doença grave, caracterizada por febre, hemorragia, falência renal e trombocitopenia. Pelo menos sete hantavírus causam a FHSR: Hantaan, Seoul (SEOV) (de distribuição global), Dobrava-Belgrade, Saaremaa, Amur, Thailand e Puumala. Para investigar a epidemiologia da FHRS e a transmissão viral na Argentina, criamos um plasmídio procariótico que "codifica" a nucleoproteína recombinante do vírus SEOV de 430 aminoácidos. Após a expressão, a nucleoproteína recombinante foi testada como antígeno para uso em ensaio imunoenzimático (ELISA) para diagnóstico da infecção. Para determinar o nível atual de transmissão viral em populações de ratos-marrons ou ratazanas (Rattus norvegicus) capturadas na cidade de Buenos Aires, Argentina, testamos tecidos de ratos selecionados para serem sorologicamente positivos para o vírus SEOV, e o seu genoma viral foi detectado após submetido a RT-PCR utilizando primers específicos para dois fragmentos de proteínas Gn e Gc codificadas pelo segmento M. O genoma viral foi detectado em 11 das 21 ratazanas soropositivas (52,4 por cento), previamente capturadas em dois parques. A análise sequencial de uma região gênica (333 nt) do segmento M "codificador" da proteína Gc apresentou 97 por cento e 96 por cento de similaridade com as cepas de SEOV coletadas em Baltimore e no Brasil, respectivamente. Os dados genéticos levantados confirmam a informação de que há uma diversidade muito pequena entre as cepas do vírus SEOV...