Neurological disease caused by Oropouche virus in northern Brazil: should it be included in the scope of clinical neurological diseases?

Emergence of Oropouche fever in Latin America: a narrative review

Since its discovery in 1955, the incidence and geographical spread of reported Oropouche virus (OROV) infections have increased. Oropouche fever has been suggested to be one of the most important vector-borne diseases in Latin America. However, both literature on OROV and genomic sequence availability are scarce, with few contributing laboratories worldwide. Three reassortant OROV glycoprotein gene variants termed Iquitos, Madre de Dios, and Perdões virus have been described from humans and non-human primates. OROV predominantly causes acute febrile illness, but severe neurological disease such as meningoencephalitis can occur. Due to unspecific symptoms, laboratory diagnostics are crucial. Several laboratory tests have been developed but robust commercial tests are hardly available. Although OROV is mainly transmitted by biting midges, it has also been detected in several mosquito species and a wide range of vertebrate hosts, which likely facilitates its widespread emergence. However, potential non-human vertebrate reservoirs have not been systematically studied. Robust animal models to investigate pathogenesis and immune responses are not available. Epidemiology, pathogenesis, transmission cycle, cross-protection from infections with OROV reassortants, and the natural history of infection remain unclear. This Review identifies Oropouche fever as a neglected disease and offers recommendations to address existing knowledge gaps, enable risk assessments, and ensure effective public health responses.

Exposure of domestic animals to Mayaro and Oropouche viruses in urban and peri-urban areas of West-Central Brazil

Oropouche and Mayaro viruses are enzootic arboviruses of public health concern throughout Latin America. Recent outbreaks of OROV in northern region and sporadic autochthonous cases in western region of Brazil, suggest a silent circulation of these neglected viruses. Aiming to investigate the exposure of different species of domestic animals to MAYV and OROV in urban and peri-urban areas of West-Central Brazil, we performed a cross-sectional serosurvey by plaque reduction neutralization test (PRNT). Our findings included neutralizing antibodies for both arboviruses in cattle, dogs and horses, suggesting eventual role of domestic animals in enzootic arbovirus surveillance in Brazil.

Outbreak of Oropouche virus in frontier regions in western Amazon

Oropouche virus (OROV) is characterized as a re-emerging arbovirus of great concern for public health, being responsible for several outbreaks of acute fever identified in Latin American countries, registering more than half a million reported cases. The incidence of reports of this virus is intrinsically favored by environmental conditions, in which such characteristics are related to the increase and distribution of the vector population to areas of human traffic. Moreover, there is a problem regarding the lack of diagnosis in Brazil that aggregates the success of the etiologic agent. Thus, by means of molecular techniques, we identified 27 positive cases of the OROV circulating in border locations in western Amazon, with 44.44% (12/27) of the cohort characterized as infected individuals with reported symptoms, mainly ranging from fever, myalgia, and back pain. Among the positive samples, it was possible to obtain a total of 48.14% (13/27) samples to analyze the S and M segments of Oropouche, which showed similarities among the Brazilian sequences. Thus, it was possible to verify the circulation of the OROV in Rondonia and border areas, in which the tracking of neglected arboviruses is necessary for the genomic surveillance of emerging and re-emerging viruses.IMPORTANCEThe western Amazon region is known for outbreaks of acute febrile illnesses, to which the lack of specific diagnostics for different pathogens hinders the management of patients in healthcare units. The Oropouche virus has already been recorded in the region in the 1990s. However, this is the first study, after this record, to perform the detection of individuals with acute febrile illness using a screening test to exclude Zika, dengue, and chikungunya, confirmed by sequencing the circulation of the virus in the state of Rondonia and border areas. We emphasize the importance of including diagnostics for viruses such as Oropouche, which suffers underreporting for years and is related to seasonal periods in Western Amazon locations, a factor that has a direct influence on public health in the region. In addition, we emphasize the importance of genomic surveillance in the elucidation of outbreaks that affect the resident population of these locations.

Oropouche virus: A neglected global arboviral threat

The Oropouche virus is an important arthropod-borne virus in the Peribunyaviridae family that can cause febrile illnesses, and it is widely distributed in tropical regions such as Central and South America. Since the virus was first identified, a large number of related cases are reported every year. No deaths have been reported to date, however, the virus can cause systemic infections, including the nervous and blood systems, leading to serious complications. The transmission of Oropouche virus occurs through both urban and sylvatic cycles, with the anthropophilic biting midge Culicoides paraensis serving as the primary vector in urban areas. Direct human-to-human transmission of Oropouche virus has not been observed. Oropouche virus consists of three segments, and the proteins encoded by the different segments enables the virus to replicate efficiently in the host and to resist the host's immune response. Phylogenetic analyses showed that Oropouche virus sequences are geographically distinct and have closer homologies with Iquitos virus and Perdoes virus, which belong to the family Peribunyaviridae. Despite the enormous threat it poses to public health, there are currently no licensed vaccines or specific antiviral treatments for the disease it causes. Recent studies have utilised imJatobal virusmunoinformatics approaches to develop epitope-based peptide vaccines, which have laid the groundwork for the clinical use of vaccines. The present review focuses on the structure, epidemiology, immunity and phylogeny of Oropouche virus, as well as the progress of vaccine development, thereby attracting wider attention and research, particularly with regard to potential vaccine programs.

Low-density lipoprotein receptor-related protein 1 (LRP1) as an auxiliary host factor for RNA viruses

Viruses with an RNA genome are often the cause of zoonotic infections. In order to identify novel pro-viral host cell factors, we screened a haploid insertion-mutagenized mouse embryonic cell library for clones that are resistant to Rift Valley fever virus (RVFV). This screen returned the low-density lipoprotein receptor-related protein 1 (LRP1) as a top hit, a plasma membrane protein involved in a wide variety of cell activities. Inactivation of LRP1 in human cells reduced RVFV RNA levels already at the attachment and entry stages of infection. Moreover, the role of LRP1 in promoting RVFV infection was dependent on physiological levels of cholesterol and on endocytosis. In the human cell line HuH-7, LRP1 also promoted early infection stages of sandfly fever Sicilian virus and La Crosse virus, but had a minor effect on late infection by vesicular stomatitis virus, whereas encephalomyocarditis virus was entirely LRP1-independent. Moreover, siRNA experiments in human Calu-3 cells demonstrated that also SARS-CoV-2 infection benefitted from LRP1. Thus, we identified LRP1 as a host factor that supports infection by a spectrum of RNA viruses.

Retrospective molecular investigation of Mayaro and Oropouche viruses at the human-animal interface in West-central Brazil, 2016-2018

Mayaro virus (MAYV, Togaviridae) and Oropouche orthobunyavirus (OROV, Peribunyaviridae) are emerging enzootic arboviruses in Latin America. Outbreaks of febrile illness associated with MAYV and OROV have been reported among humans mainly in the northern region of Brazil since the 1980s, and recent data suggest these viruses have circulated also in more populated areas of western Brazil. MAYV shares mosquito vectors with yellow fever virus and it has been historically detected during yellow fever epidemics. Aiming to investigate the transmission of OROV and MAYV at the human-animal interface during a yellow fever, chikungunya and Zika outbreaks in Brazil, we conducted a retrospective molecular investigation in 810 wild and domestic animals, 106 febrile patients, and 22.931 vectors collected from 2016 to 2018 in Cuiaba and Campo Grande metropolitan regions, western Brazil. All samples tested negative for OROV and MAYV RNA by RT-qPCR. Findings presented here suggest no active circulation of MAYV and OROV in the sampled hosts. Active surveillance and retrospective investigations are instrumental approaches for the detection of cryptic and subclinical activity of enzootic arboviruses and together serve as a warning system to implement appropriate actions to prevent outbreaks.

Modulation of HERV Expression by Four Different Encephalitic Arboviruses during Infection of Human Primary Astrocytes

Human retroelements (HERVs) are retroviral origin sequences fixed in the human genome. HERVs induction is associated with neurogenesis, cellular development, immune activation, and neurological disorders. Arboviruses are often associated with the development of encephalitis. The interplay between these viruses and HERVs has not been fully elucidated. In this work, we analyzed RNAseq data derived from infected human primary astrocytes by Zika (ZikV), Mayaro (MayV), Oropouche (OroV) and Chikungunya (ChikV) viruses, and evaluated the modulation of HERVs and their nearby genes. Our data show common HERVs expression modulation by both alphaviruses, suggesting conserved evolutionary routes of transcription regulation. A total of 15 HERVs were co-modulated by the four arboviruses, including the highly upregulated HERV4_4q22. Data on the upregulation of genes nearby to these elements in ChikV, MayV and OroV infections were also obtained, and interaction networks were built. The upregulation of 14 genes common among all viruses was observed in the networks, and 93 genes between MayV and ChikV. These genes are related to cellular processes such as cellular replication, cytoskeleton, cell vesicle traffic and antiviral response. Together, our results support the role of HERVs induction in the transcription regulation process of genes during arboviral infections.

Oropouche orthobunyavirus infection is mediated by the cellular host factor Lrp1

Oropouche orthobunyavirus (OROV; Peribunyaviridae) is a mosquito-transmitted virus that causes widespread human febrile illness in South America, with occasional progression to neurologic effects. Host factors mediating the cellular entry of OROV are undefined. Here, we show that OROV uses the host protein low-density lipoprotein-related protein 1 (Lrp1) for efficient cellular infection. Cells from evolutionarily distinct species lacking Lrp1 were less permissive to OROV infection than cells with Lrp1. Treatment of cells with either the high-affinity Lrp1 ligand receptor-associated protein (RAP) or recombinant ectodomain truncations of Lrp1 significantly reduced OROV infection. In addition, chimeric vesicular stomatitis virus (VSV) expressing OROV glycoproteins (VSV-OROV) bound to the Lrp1 ectodomain in vitro. Furthermore, we demonstrate the biological relevance of the OROV-Lrp1 interaction in a proof-of-concept mouse study in which treatment of mice with RAP at the time of infection reduced tissue viral load and promoted survival from an otherwise lethal infection. These results with OROV, along with the recent finding of Lrp1 as an entry factor for Rift Valley fever virus, highlight the broader significance of Lrp1 in cellular infection by diverse bunyaviruses. Shared strategies for entry, such as the critical function of Lrp1 defined here, provide a foundation for the development of pan-bunyaviral therapeutics.

Arboviral Infections in Neurological Disorders in Hospitalized Patients in São José do Rio Preto, São Paulo, Brazil

Arbovirus infections are increasingly important causes of disease, whose spectrum of neurological manifestations are not fully known. This study sought to retrospectively assess the incidence of arboviruses in cerebrospinal fluid samples of patients with neurological symptoms to inform diagnosis of central and peripheral nervous system disorders. A total of 255 cerebrospinal fluid (CSF) samples collected from January 2016 to December 2017 were tested for dengue virus (DENV 1-4), Zika virus (ZIKV), and Chikungunya virus (CHIKV) in addition to other neurotropic arboviruses of interest, using genetic and serologic assays. Of the 255 CSF samples analyzed, 3.53% (09/255) were positive for arboviruses presenting mainly as meningitis, encephalitis, and cerebrovascular events, of which ZIKV was detected in 2.74% (7/255), DENV in 0.78% (2/255), in addition to an identified ILHV infection that was described previously. All the cases were detected in adults aged 18 to 74 years old. Our findings highlight the scientific and clinical importance of neurological syndromes associated with arboviruses and demonstrate the relevance of specific laboratory methods to achieve accurate diagnoses as well as highlight the true dimension of these diseases to ultimately improve public health planning and medical case management.

Presence and Multi-Species Spatial Distribution of Oropouche Virus in Brazil within the One Health Framework

Oropouche virus (OROV) is an emerging vector-borne arbovirus with high epidemic potential, causing illness in more than 500,000 people. Primarily contracted through its midge and mosquito vectors, OROV remains prevalent in its wild, non-human primate and sloth reservoir hosts as well. This virus is spreading across Latin America; however, the majority of cases occur in Brazil. The aim of this research is to document OROV’s presence in Brazil using the One Health approach and geospatial techniques. A scoping review of the literature (2000 to 2021) was conducted to collect reports of this disease in humans and animal species. Data were then geocoded by first and second subnational levels and species to map OROV’s spread. In total, 14 of 27 states reported OROV presence across 67 municipalities (second subnational level). However, most of the cases were in the northern region, within the tropical and subtropical moist broadleaf forests biome. OROV was identified in humans, four vector species, four genera of non-human primates, one sloth species, and others. Utilizing One Health was important to understand the distribution of OROV across several species and to suggest possible environmental, socioeconomic, and demographic drivers of the virus’s presence. As deforestation, climate change, and migration rates increase, further study into the spillover potential of this disease is needed.

An Overview of Neglected Orthobunyaviruses in Brazil

Dozens of orthobunyaviruses have been isolated in Brazil, and at least thirteen have been associated with human disease. The Oropouche virus has received most attention for having caused explosive epidemics with hundreds of thousands of cases in the north region between the 1960sand the 1980s, and since then has been sporadically detected elsewhere in the country. Despite their importance, little is known about their enzootic cycles of transmission, amplifying hosts and vectors, and biotic and abiotic factors involved in spillover events to humans. This overview aims to combine available data of neglected orthobunyaviruses of several serogroups, namely, Anopheles A, Anopheles B, Bunyamwera, California, Capim, Gamboa, Group C, Guama, Simbu and Turlock, in order to evaluate the current knowledge and identify research gaps in their natural transmission cycles in Brazil to ultimately point to the future direction in which orthobunyavirus research should be guided.