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Here, we report the complete genome sequence of the Aporé virus (Bunyavirales: Arenaviridae), obtained from a wild rodent Oligoryzomys mattogrossae captured in Mato Grosso do Sul state, Brazil. The genome of this virus showed strong similarity to highly pathogenic mammarenavirus from South America.

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Tacaribe virus (TCRV) was first isolated from 11 Artibeus species bats captured in Trinidad in the 1950s during a rabies virus surveillance program. Despite significant effort, no evidence of infection of other mammals, mostly rodents, was found, suggesting that no other vertebrates harbored TCRV. For this reason, it was hypothesized that TCRV was naturally hosted by artibeus bats. This is in stark contrast to other arenaviruses with known hosts, all of which are rodents. To examine this hypothesis, we conducted experimental infections of Jamaican fruit bats (Artibeus jamaicensis) to determine whether they could be persistently infected without substantial pathology. We subcutaneously or intranasally infected bats with TCRV strain TRVL-11573, the only remaining strain of TCRV, and found that low-dose (10(4) 50% tissue culture infective dose [TCID(50)]) inoculations resulted in asymptomatic and apathogenic infection and virus clearance, while high-dose (10(6) TCID(50)) inoculations caused substantial morbidity and mortality as early as 10 days postinfection. Uninoculated cage mates failed to seroconvert, and viral RNA was not detected in their tissues, suggesting that transmission did not occur. Together, these data suggest that A. jamaicensis bats may not be a reservoir host for TCRV.

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Chronic infections in specific rodents appear to be crucial to the long-term persistence of arenaviruses in nature. The cane mouse, Zygodontomys brevicauda, is a natural host of Guanarito virus (family Arenaviridae), the etiologic agent of Venezuelan hemorrhagic fever. The purpose of this study was to elucidate the natural history of Guanarito virus infection in Z. brevicauda. Thirty-nine laboratory-reared cane mice each were inoculated subcutaneously with 3.0 log10 plaque-forming units of the Guanarito virus prototype strain INH-95551. No lethality was associated with infection in any animal, regardless of age at inoculation. The 13 newborn, 14 weanling, and 8 of the 12 adult animals developed chronic viremic infections characterized by persistent shedding of infectious virus in oropharyngeal secretions and urine. These findings indicate that Guanarito virus infection in Z. brevicauda can be chronic and thus support the concept that this rodent species is the natural reservoir of Guanarito virus.

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Sao descritos os achados clinico-laboratoriais da infeccao acidental pelo virus SP H 114202 (Arenavirus, familia Arenaviridae), um virus novo causador de febre hemorragica humana. O paciente, tecnico de laboratorio, apresentou quadro febril por 13 dias. A doenca cursou com febre elevada (39ºC) diaria, cefaleia, calefrios e mialgias por 8 dias. A partir do 3§ dia surgiram nauseas, vomitos alimentares e anorexia e no 10§ dia, epigastralgia, diarreia e gengivorragia....

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Here in is described the clinical and laboratorial findings of a laboratory-acquired infection caused by the virus SP H 114202 (Arenavirus, family Arenaviridae) a recently discovered agent responsible for a viral hemorrhagic fever. The patient was sick for 13 days. The disease had an abrupt onset characterized by high fever (39 degree C.), headache, chills and myalgias for 8 days. In addition, on the 3rd day, the patient developed nausea and vomiting, and in the 10th, epigastralgia, diarrhea and gengivorrhagia. Leucopenia was seen within the 1st week of onset, with counts as low as 2,500 white cells per mm3. Counts performed after the 23rd day of the onset were within normal limits. With the exception of moderate lymphocytosis, no changes were observed in differential counts. An increase in the titer of antibodies by complement fixation, neutralization and ELISA (IgM) was detected. Suckling mice and baby hamsters were inoculated intracerebrally with 0.02 ml of blood samples collected in the 2nd and 7th days of disease. Attempts to isolate the virus were also made in Vero cells. No virus was isolated. This virus was isolated before in a single occasion in São Paulo State, in 1990, from the blood of a patient with hemorrhagic fever with a fatal outcome. The manipulation of the virus under study, must be done carefully, since the transmission can occur through aerosols.

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La Fiebre Hemorrágica Venezolana es una enfermedad severa causada por el virus Guanarito que aparece en forma endemo-epidémica en Venezuela a partir de 1989. Los Arenavirus utilizan como reservorio a los roedores para persistir en la naturaleza, siendo específicos para la especie que les sirve como hospedador. La infección del humano ocurre por contacto con secreciones de estos animales. Para conocer el reservorio natural del virus Guanarito, se capturaron 256 ejemplares de roedores en 5 áreas representativas de los tipos de hábitat del Municipio Guanarito del Edo. Portuguesa. Los animales fueron clasificados en 9 especies y se recolectaron muestras de sangre y bazo para realizar estudios virológicos. El macerado de cada bazo fue inoculado en células VERO E6 para aislamiento viral y en la sangre se determinaron anticuerpos específicos para el virus Guanarito por la técnica de IFI. Los resultados indicaron una alta densidad de roedores en la Hoyada y la Arenosa donde las especies dominantes en orden e importancia fueron: Zygodontomys brevicauda, Sigmodon alstoni, Rattus rattus, Proechymys guairae y Oryzomys fulvecens. Todas estas especies se encontraron susceptibles a la infección por el virus Guanarito; el mayor porcentaje de roedores infetados se encontró en la especie Sigmodon alstoni (52,6 por ciento) y Zygodontomys brevicauda (26,3//). De especial interés fue el hallazgo que 9 de 13 animales de esta última especie, excretaba virus en presencia de anticuerpos humorales. Estos resultados indican que el virus Guanarito está ampliamente distribuido entre los roedores dominantes en esta zona del país, pero la especie Sigmodon alstoni es reservorio potencial del virus, las otras especies son reservorios que contribuyen a mantener el virus en la naturaleza y también constituyen una fuente de infección para el humano

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The major natural reservoir of Junin virus, the aetiological agent of Argentine haemorrhagic fever, is the cricetid Calomys musculinus. Neonatal animals experimentally infected with Junin virus (XJCl3 strain) developed typical disease and approximately 80% of them died. Most survivors become persistently infected. Antigenically variant viruses were isolated from the blood and brain of infected cricetids during the acute and chronic stages of the disease. These variants could be distinguished from the parental strain by kinetic neutralization assays using polyclonal antibodies. Some biological properties were shared with the parental virus strain including its virulence for newborn C. musculinus. These variant viruses may play a major role in chronic disease since we have shown that a viral isolate from an infected brain was poorly neutralized by serum obtained from the same animal.

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Tacaribe virus may represent a better alternative than attenuated strains of Junin virus (JV) for immunization against Argentine hemorrhagic fever (AHF) because of possible risk of persistent infection of disease associated with live, attenuated strains. Callithrix jacchus marmosets, which suffer 100% mortality if inoculated with the pathogenic XJ strain of JV, were used to evaluate possible Tacaribe virus persistence, subclinical, or long-term disease and the duration of protection against challenge with JV. Histologic studies did not show pathogenic changes due to Tacaribe virus in primates sacrificed from 7 to 480 days postinoculation (pi). No virus was recovered in tissue samples after primary culture or cocultures with sensitive cells. The presence of anti-Tacaribe neutralizing serum antibodies and protection against pathogenic JV were detected up to 480 days after a single dose of Tacaribe virus. However, anti-Junin antibodies were detected only after challenge. In other experiments, protection against JV was evaluated histologically and virologically. Two primates were immunized with Tacaribe virus, challenged with JV, and sacrificed 18 or 21 days later. Subclinical histopathologic findings were associated with recovery of JV only by the sensitive primary culture-coculture techniques. The immunogenicity, degree of protection, and safety of Tacaribe virus indicate its potential as a vaccine against human AHF.

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The effect of infection with Junin virus on growth and reproduction of its natural reservoir, Calomys musculinus, was studied. Eighty-five C. musculinus were inoculated intranasally at birth with 100 TCID50 of Cba An 9446 strain of Junin virus and observed for 480 days. No clinical signs of neurologic illness were registered. Infected animals showed an increased mortality rate of up to 70% between days 24-40 post-infection. This period of high mortality was preceded by low weight gain during lactation and registered until 60 days. From day 14 post-infection until day 480, Junin virus was recovered from blood, urine, and oral swab in all animals checked at any time. By day 480 post-infection, 100% of survivors showed widespread viral dissemination in brain, spleen, kidneys, and salivary glands. There was marked reduction in reproductive efficiency among infected animals. Out of 15 mating pairs, 2 (13.3%) littered at least once compared to 60% in the control group. The reduction of fertility and the altered survival rate of Junin virus-infected C. musculinus indicate that vertical transmission mechanisms per se are insufficient to maintain the infection in successive generations in the absence of horizontal transmission.

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Tacaribe virus is know to protect guinea pigs and primates against lethal challenge with Junín virus. A long-term study on the effect of Tacaribe virus infection in the guinea pig was carried out to determine the extent of cross-protection and whether antigen and/or viral persistence and tissue damage could be detected in immune animals. Viral titers, antigen expression in organs, and histologic lesions were sequentially searched for up to 540 days postinfection (pi). Neutralizing antibodies (Abs) and cross-protection to Junín virus were evaluated up to 660 days pi. Tacaribe virus titers and antigen peaked at 7-10 days pi to become undetectable after 30 days pi, except for a transient viral recovery from salivary gland. Virus was undetectable by coculture at 365 and 540 days pi. No immunoglobulins or C3 deposits were detected by immunofluorescence in brain or kidney at any stage, and histologic lesions were absent throughout. Anti-Tacaribe and anti-Junín neutralizing Abs were detected up to 660 days and full protection against challenge was achieved at 365 and 540 days, declining to 33% at 660 days pi. The results warrant consideration of Tacaribe virus as potential heterologous vaccine against Argentine hemorrhagic fever.

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Detection of viremia was attempted by three different methods in 30 cases of Argentine hemorrhagic fever (AHF). Cocultivation of peripheral blood mononuclear cells (PBMC) with Vero cell monolayers was the most sensitive, detecting Junin virus (JV) in 96% of the cases. Inoculation of whole blood into suckling mice and on Vero cells rendered 53 and 46% of positive isolations, respectively. The results presented suggest that PBMC are infected with JV during the acute period of AHF. JV was isolated with decreasing frequency up to 3 days after treatment with immune plasma, but no virus was recovered from PBMC during early convalescence.

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Neonatal Calomys musculinus experimental infection with Junín virus (JV) XJCl3 strain causes either death or a persistent infection in the major part of surviving animals. JV can be isolated from peritoneal macrophages early during infection, and from brain and salivary glands during the chronic state of disease. It was of interest to investigate the appearance of virus in blood of infected animals. For this purpose, we decided to study the development of viremia in inoculated cricetids. A high frequency of viremia was registered during the acute state of disease (figure 1), which became sporadic approximately from 20 days post-infection onwards. Considering the results above mentioned, the characteristic lymphotropism of arenaviruses and the well-known JV replication in human mononuclear cells, cultures of lympho-monocytes obtained from blood of infected C. musculinus were done in order to investigate the eventual detection of infectious virus in the supernatants. JV was isolated, although in low titres, from cultures established with mononuclear cells belonging to animals in the acute state of disease (table 1); in the case of chronically infected cricetids, attempts to isolate JV were negative. These results show that viremia is currently detected in experimentally infected C. musculinus and that circulating mononuclear cells are permissive for JV multiplication, during the acute state of disease.

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