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Background: Dengue epidemics have been reported in Brazil since 1981. In Manaus, a large city in the Amazon region, dengue is endemic with all four-virus serotypes (DENV-1, -2, -3, and -4) simultaneously causing human disease. In 2008, during a surveillance of dengue virus in mosquitoes in the district of Tancredo Neves in Manaus, 260 mosquitoes of Aedes genus were captured, identified and grouped into pools of 10 mosquitoes. Findings: RNA extracts of mosquito pools were tested by a RT-Hemi-Nested-PCR for detection of flaviviruses. One amplicon of 222 bp, compatible with dengue virus serotype 4, was obtained from a pool of Aedes aegypti. The nucleotide sequence of the amplicon indicated that the mosquitoes were infected with DENV-4 of genotype I. This virus of Asian origin has been described in Manaus in 2008 infecting acute febrile illness patients. Conclusion: This is the first report of dengue virus serotype 4 genotype I infecting Aedes aegypti in the Americas. [ABSTRACT FROM AUTHOR]

Copyright of Revista do Instituto de Medicina Tropical de São Paulo is the property of Instituto de Medicina Tropical de Sao Paulo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista do Instituto de Medicina Tropical de São Paulo is the property of Instituto de Medicina Tropical de Sao Paulo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A letter to the editor about the outbreak of Saint Louis encephalitis virus in Brazil is presented.

The Hepacivirus genus comprises single-stranded positive-sense RNA viruses within the family Flaviviridae. Several hepaciviruses have been identified in different mammals, including multiple rodent species in Africa, Asia, Europe, and North America. To date, no rodent hepacivirus has been identified in the South American continent. Here, we describe an unknown hepacivirus discovered during a metagenomic screen in Akodon montensis, Calomys tener, Oligoryzomys nigripes, Necromys lasiurus, and Mus musculus from São Paulo State, Brazil. Molecular detection of this novel hepacivirus by RT-PCR showed a frequency of 11.11% (2/18) in Oligoryzomys nigripes. This is the first identification of hepavivirus in sigmondonine rodents and in rodents from South America. In sum, our results expand the host range, viral diversity, and geographical distribution of the Hepacivirus genus. [ABSTRACT FROM AUTHOR]

Chikungunya virus (CHIKV) and Mayaro virus (MAYV) are closely related members of the Semliki Forest virus antigenic complex classified as belonging to the genus Alphavirus of the family Togaviridae. These viruses cause human disease, with sudden fever and joint inflammation that can persist for long periods. CHIKV is the causative agent of large outbreaks worldwide, and MAYV infection represents a growing public health concern in Latin America, causing sporadic cases and geographically limited outbreaks. Considering the relationship between CHIKV and MAYV, the present study aimed to evaluate if preexisting CHIKV immunity protects against MAYV infection. Immunocompetent C57BL/6 mice were intraperitoneally infected with CHIKV and, 4 weeks later, they were infected with MAYV in their hind paw. We observed that the preexistence of CHIKV immunity conferred partial cross-protection against secondary MAYV infection, reducing disease severity, tissue viral load, and histopathological scores. Interestingly, CHIKV antibodies from humans and mice showed low cross-neutralization to MAYV, but neutralizing activity significantly increased after secondary infection. Furthermore, depletion of adaptive immune cells (CD41 T, CD81 T, and CD191 B cells) did not alter the cross-protection phenotype, suggesting that distinct cell subsets or a combination of adaptive immune cells stimulated by CHIKV are responsible for the partial cross-protection against MAYV. The reduction of proinflammatory cytokines, such as interferon gamma (IFN-g), in animals secondarily infected by MAYV, suggests a role for innate immunity in cross-protection. Our findings shed light on how preexisting immunity to arthritogenic alphaviruses may affect secondary infection, which may further develop relevant influence in disease outcome and viral transmission. IMPORTANCE Mosquito-borne viruses have a worldwide impact, especially in tropical climates. Chikungunya virus has been present mostly in developing countries, causing millions of infections, while Mayaro virus, a close relative, has been limited to the Caribbean and tropical regions of Latin America. The potential emergence and spread of Mayaro virus to other high-risk areas have increased the scientific community’s attention to an imminent worldwide epidemic. Here, we designed an experimental protocol of chikungunya and Mayaro virus mouse infection, which develops a measurable and quantifiable disease that allows us to make inferences about potential immunological effects during secondary virus infection. Our results demonstrate that previous chikungunya virus infection is able to reduce the severity of clinical outcomes during secondary Mayaro infection. We provide scientific understanding of immunological features during secondary infection with the closely related virus, thus assisting in better comprehending viral transmission and the pathological outcome of these diseases. [ABSTRACT FROM AUTHOR]

Abstract: The hantavirus pulmonary syndrome (HPS) is an emerging syndrome in the Americas. The disease results from intense immune activation and changes in vascular permeability. The aim of this study was to determine the profile of serum cytokines in HPS patients looking for correlation with the clinical parameters, severity and outcome of illness. Studying 21 HPS patients, we found that IL-6 may have an important role in the pathogenesis of HPS, being associated with fatal outcome. Our results also support a mixed Th1/Th2 immune response during the course of HPS and that the magnitude of Th1 response effector cytokines is correlated to HPS severity. The decreased levels of TGF-β observed in HPS patients suggest that immunoregulatory activity could be damaged in these patients. [Copyright &y& Elsevier]

Background and Aim: Venezuelan equine encephalitis virus (VEEV) is an alphavirus that causes encephalitis with a high impact on public health in Latin America. However, only in Guatemala, Trinidad and Tobago, and Mexico have found antibodies in VEEV in bats, using immunohistochemistry, the sensitivity and specificity are improved; thus, it is better for demonstrating natural infection in bats as potential hosts. This study aimed to determine the presence of VEEV in tissues of frugivorous bats., Materials and Methods: A prospective descriptive cross-sectional study with a non-probabilistic sampling was carried out in 12 localities of Córdoba and Sucre area of the Colombian Caribbean. Two hundred and eighty-six bats were captured using fog nets, and the specimens according to taxonomic keys were classified. According to the Ethics Committee of the University of Córdoba, the bats were treated with analgesics and anesthetics. Blood samples were taken and then euthanized to obtain tissues and organs which were preserved in liquid N2 at -196°C. A portion of each organ was fixed in 10% buffered formalin for the detection of antigens by immunohistochemistry. Several pathological anatomy analyses were performed to determine the histological characteristics of tissue lesions of frugivorous bats naturally infected with the VEEV., Results: Of the 286 bats captured, 23 species were identified. In samples of the brain, spleen, and lung of two frugivorous bats (2/286=0.70%) Artibeus planirostris and Sturnira lilium , the presence of VEEV was confirmed by immunohistochemistry., Conclusion: A fragment of the nsP4 non-structural protein gene corresponding to the alphavirus was amplified. Two samples were positive (2/286=0.70%) in frugivorous bats; A. planirostris (code GenBank: MG820274) and S. lilium (code GenBank: MG820275). The present study showed the first molecular evidence and cellular evidence (histopathology and immunohistochemistry) of natural VEEV infection in frugivorous bats in Colombia; these bats could be a host of this zoonosis., (Copyright: © Guzmán, et al.)

Dengue fever is a noncontagious infectious disease caused by dengue virus (DENV). DENV belongs to the family Flaviviridae, genus Flavivirus, and is classified into four antigenically distinct serotypes: DENV-1, DENV-2, DENV-3, and DENV-4. The number of nations and people affected has increased steadily and today is considered the most widely spread arbovirus (arthropod-borne viral disease) in the world. The absence of an appropriate animal model for studying the disease has hindered the understanding of dengue pathogenesis. In our study, we have found that immunocompetent C57BL/6 mice infected intraperitoneally with DENV-1 presented some signs of dengue disease such as thrombocytopenia, spleen hemorrhage, liver damage, and increase in production of IFNγ and TNFα cytokines. Moreover, the animals became viremic and the virus was detected in several organs by real-time RT-PCR. Thus, this animal model could be used to study mechanism of dengue virus infection, to test antiviral drugs, as well as to evaluate candidate vaccines.

A new approach was developed for the rapid detection and identification of Brazilian alphaviruses and flaviviruses. The methodology involves the genus-specific detection of Alphavirus and Flavivirus by a duplex reverse transcription-PCR (D-RT-PCR), followed by multiplex nested PCR (M-N-PCR) or nested PCR (N-PCR) assays for species-specific identification. By this protocol, 25 arboviruses were specifically detected and identified. Detection levels between 10(1.3) and 10(3.5) 50% tissue culture infective doses (TCID(50))/ml of Flavivirus and Alphavirus strains were achieved by D-RT-PCR, and levels of <1 TCID(50)/ml were achieved by M-N-PCR assays. To assess the suitability and clinical application of this methodology, a total of 101 human or animal stored samples were analyzed. Results obtained suggest that this technique could be applied as a rapid diagnostic tool in clinical samples in which arbovirus infection is suspected and differential diagnosis is required, avoiding the need to test specimens by separate PCR methods.