Neurological manifestations of Flaviviridae, Togaviridae, and Peribunyaviridae as vector-borne viruses.

Vector-borne viruses pose a significant health problem worldwide, as they are transmitted to humans through the bite of infected arthropods such as mosquitoes and ticks. In recent years, emerging and re-emerging vector-borne diseases have gained attention as they can cause a wide spectrum of neurological manifestations. The neurological manifestations of vector-borne viruses encompass a board spectrum of clinical manifestations, ranging from mild and self-limiting symptoms to severe and life-threatening conditions. Common neurological complications include viral encephalitis, acute flaccid paralysis, aseptic meningitis, and various neuromuscular disorders. The specific viruses responsible for these neurological sequelae vary by geographic region and include Orthoflavivirus nilense, Zika virus, dengue virus, chikungunya virus, Japanese encephalitis virus, and tick-borne encephalitis virus. This review focuses on the pathogenesis of these neurologic complications and highlights the mechanisms by which vector-borne viruses invade the central nervous system and trigger neuroinflammatory responses. Diagnostic challenges and strategies for early detection of neurological manifestations are discussed, emphasising the importance of clinical suspicion and advanced laboratory testing.

Performance assessment of a multi-epitope chimeric antigen for the serological diagnosis of acute Mayaro fever.

Mayaro virus (MAYV), which causes mayaro fever, is endemic to limited regions of South America that may expand due to the possible involvement of Aedes spp. mosquitoes in its transmission. Its effective control will require the accurate identification of infected individuals, which has been restricted to nucleic acid-based tests due to similarities with other emerging members of the Alphavirus genus of the Togaviridae family; both in structure and clinical symptoms. Serological tests have a more significant potential to expand testing at a reasonable cost, and their performance primarily reflects that of the antigen utilized to capture pathogen-specific antibodies. Here, we describe the assembly of a synthetic gene encoding multiple copies of antigenic determinants mapped from the nsP1, nsP2, E1, and E2 proteins of MAYV that readily expressed as a stable chimeric protein in bacteria. Its serological performance as the target in ELISAs revealed a high accuracy for detecting anti-MAYV IgM antibodies. No cross-reactivity was observed with serum from seropositive individuals for dengue, chikungunya, yellow fever, Zika, and other infectious diseases as well as healthy individuals. Our data suggest that this bioengineered antigen could be used to develop high-performance serological tests for MAYV infections.

The NLRP3 inflammasome is involved with the pathogenesis of Mayaro virus.

Mayaro virus (MAYV) is an arbovirus that circulates in Latin America and is emerging as a potential threat to public health. Infected individuals develop Mayaro fever, a severe inflammatory disease characterized by high fever, rash, arthralgia, myalgia and headache. The disease is often associated with a prolonged arthralgia mediated by a chronic inflammation that can last months. Although the immune response against other arboviruses, such as chikungunya virus (CHIKV), dengue virus (DENV) and Zika virus (ZIKV), has been extensively studied, little is known about the pathogenesis of MAYV infection. In this study, we established models of MAYV infection in macrophages and in mice and found that MAYV can replicate in bone marrow-derived macrophages and robustly induce expression of inflammasome proteins, such as NLRP3, ASC, AIM2, and Caspase-1 (CASP1). Infection performed in macrophages derived from Nlrp3-/-, Aim2-/-, Asc-/-and Casp1/11-/-mice indicate that the NLRP3, but not AIM2 inflammasome is essential for production of inflammatory cytokines, such as IL-1ß. We also determined that MAYV triggers NLRP3 inflammasome activation by inducing reactive oxygen species (ROS) and potassium efflux. In vivo infections performed in inflammasome-deficient mice indicate that NLRP3 is involved with footpad swelling, inflammation and pain, establishing a role of the NLRP3 inflammasome in the MAYV pathogenesis. Accordingly, we detected higher levels of caspase1-p20, IL-1ß and IL-18 in the serum of MAYV-infected patients as compared to healthy individuals, supporting the participation of the NLRP3-inflammasome during MAYV infection in humans.

Insect-specific virus evolution and potential effects on vector competence.

The advancement in high-throughput sequencing technology and bioinformatics tools has spurred a new age of viral discovery. Arthropods is the largest group of animals and has shown to be a major reservoir of different viruses, including a group known as insect-specific viruses (ISVs). The majority of known ISVs have been isolated from mosquitoes and shown to belong to viral families associated with animal arbovirus pathogens, such as Flaviviridae, Togaviridae and Phenuiviridae. These insect-specific viruses have a strict tropism and are unable to replicate in vertebrate cells, these properties are interesting for many reasons. One is that these viruses could potentially be utilised as biocontrol agents using a similar strategy as for Wolbachia. Mosquitoes infected with the viral agent could have inferior vectorial capacity of arboviruses resulting in a decrease of circulating arboviruses of public health importance. Moreover, insect-specific viruses are thought to be ancestral to arboviruses and could be used to study the evolution of the switch from single-host to dual-host. In this review, we discuss new discoveries and hypothesis in the field of arboviruses and insect-specific viruses.

ICTV Virus Taxonomy Profile: Togaviridae.

The Togaviridae is a family of small, enveloped viruses with single-stranded, positive-sense RNA genomes of 10-12 kb. Within the family, the genus Alphavirus includes a large number of diverse species, while the genus Rubivirus includes the single species Rubella virus. Most alphaviruses are mosquito-borne and are pathogenic in their vertebrate hosts. Many are important human and veterinary pathogens (e.g. chikungunya virus and eastern equine encephalitis virus). Rubella virus is transmitted by respiratory routes among humans. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Togaviridae, which is available at www.ictv.global/report/togaviridae.

Wolbachia significantly impacts the vector competence of Aedes aegypti for Mayaro virus.

Wolbachia, an intracellular endosymbiont present in up to 70% of all insect species, has been suggested as a sustainable strategy for the control of arboviruses such as Dengue, Zika and Chikungunya. As Mayaro virus outbreaks have also been reported in Latin American countries, the objective of this study was to evaluate the vector competence of Brazilian field-collected Ae. aegypti and the impact of Wolbachia (wMel strain) upon this virus. Our in vitro studies with Aag2 cells showed that Mayaro virus can rapidly multiply, whereas in wMel-infected Aag2 cells, viral growth was significantly impaired. In addition, C6/36 cells seem to have alterations when infected by Mayaro virus. In vivo experiments showed that field-collected Ae. aegypti mosquitoes are highly permissive to Mayaro virus infection, and high viral prevalence was observed in the saliva. On the other hand, Wolbachia-harboring mosquitoes showed significantly impaired capability to transmit Mayaro virus. Our results suggest that the use of Wolbachia-harboring mosquitoes may represent an effective mechanism for the reduction of Mayaro virus transmission throughout Latin America.

Viral Macrodomains: Unique Mediators of Viral Replication and Pathogenesis.

Viruses from the Coronaviridae, Togaviridae, and Hepeviridae families ​all contain genes that encode a conserved protein domain, called a macrodomain; however, the role of this domain during infection has remained enigmatic. The recent discovery that mammalian macrodomain proteins enzymatically remove ADP-ribose, a common post-translation modification, from proteins has led to an outburst of studies describing both the enzymatic activity and function of viral macrodomains. These new studies have defined these domains as de-ADP-ribosylating enzymes, which indicates that these viruses have evolved to counteract antiviral ADP-ribosylation, likely mediated by poly-ADP-ribose polymerases (PARPs). Here, we comprehensively review this rapidly expanding field, describing the structures and enzymatic activities of viral macrodomains, and discussing their roles in viral replication and pathogenesis.

Insect-Specific Viruses: A Historical Overview and Recent Developments.

Arthropod-borne viruses (arboviruses) have in recent years become a tremendous global health concern resulting in substantial human morbidity and mortality. With the widespread utilization of molecular technologies such as next-generation sequencing and the advancement of bioinformatics tools, a new age of viral discovery has commenced. Many of the novel agents being discovered in recent years have been isolated from mosquitoes and exhibit a highly restricted host range. Strikingly, these insect-specific viruses have been found to be members of viral families traditionally associated with human arboviral pathogens, including but not limited to the families Flaviviridae, Togaviridae, Reoviridae, and Bunyaviridae. These agents therefore present novel opportunities in the fields of viral evolution and viral/vector interaction and have tremendous potential as agents for biocontrol of vectors and or viruses of medical importance.

Neuroinvasion and Inflammation in Viral Central Nervous System Infections.

Neurotropic viruses can cause devastating central nervous system (CNS) infections, especially in young children and the elderly. The blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB) have been described as relevant sites of entry for specific viruses as well as for leukocytes, which are recruited during the proinflammatory response in the course of CNS infection. In this review, we illustrate examples of established brain barrier models, in which the specific reaction patterns of different viral families can be analyzed. Furthermore, we highlight the pathogen specific array of cytokines and chemokines involved in immunological responses in viral CNS infections. We discuss in detail the link between specific cytokines and chemokines and leukocyte migration profiles. The thorough understanding of the complex and interrelated inflammatory mechanisms as well as identifying universal mediators promoting CNS inflammation is essential for the development of new diagnostic and treatment strategies.

Efficacy and safety of an inactivated vaccine against Salmonid alphavirus (family Togaviridae).

Pancreas disease (PD) in salmonid fish is caused by an infection with Salmonid alphavirus (SAV) and remains as one of the major health problems in the European fish farming industry. Sequence studies have revealed a genetic diversity among viral strains. A subtype of SAV (SAV3) is causing an epizootic in farmed salmonids in Norway. Here we evaluate efficacy and safety of an inactivated virus vaccine based on ALV405, a strain of SAV3 that was isolated from Norwegian salmon. The vaccine provided an average relative percent survival (RPS) of 98.5 in an intraperitoneal challenge model, and induced nearly total protection against PD in a cohabitant challenge model. It provided significant protection against SAV-induced mortality also in a field trial under industrial conditions. Local reactions seen as melanization and adhesions in the visceral cavity were less severe than those induced by two commercial vaccines. Finally, we demonstrated that the protection is not impaired when the ALV405 antigen is combined with other viral or bacterial antigens in a polyvalent vaccine. The results confirm that efficient and safe protection against SAV infection and development of PD is possible using an inactivated virus vaccine, both alone and as a component in a polyvalent vaccine.

[Virology of the family Togaviridae].

Many pathogens important for medicine, veterinary medicine or public health belong to the genera alphavirus and rubivirus within the family Togaviridae. 29 species of alphaviruses have been reported, and most of them are arboviruses. Chikungnya virus re-emerged in Kenya in 2004 and the epidemics spread to the Indian Ocean islands and many countries in South Asia, South-East Asia and Europe. On the other hand, rubella virus, a sole member of the genus rubivirus, is the causative agent of rubella and congenital rubella syndrome (CRS). Because human is only a natural host of the virus and effective live attenuated vaccines are available, immunization activities are strengthened globally to eliminate rubella and CRS, together with measles.

Vaccines and animal models for arboviral encephalitides.

Arthropod-borne viruses ("arboviruses") cause significant human illness ranging from mild, asymptomatic infection to fatal encephalitis or hemorrhagic fever. The most significant arboviruses causing human illness belong to genera in three viral families, Togaviridae, Flaviviridae, and Bunyaviridae. These viruses represent a significant public health threat to many parts of the world, and, as evidenced by the recent introduction of the West Nile virus (WNV) to the Western Hemisphere, they can no longer be considered specific to any one country or region of the world. Like most viral diseases, there are no specific therapies for the arboviral encephalitides; therefore, effective vaccines remain the front line of defense for these diseases. With this in mind, the development of new, more effective vaccines and the appropriate animal models in which to test them become paramount. In fact, for many important arboviruses (e.g. California serogroup and St. Louis encephalitis viruses), there are currently no approved vaccines available for human use. For others, such as the alphaviruses, human vaccines are available only as Investigational New Drugs, and thus are not in widespread use. On the other hand, safe and effective vaccines against tick-borne encephalitis virus (TBEV) and Japanese encephalitis virus (JEV) have been in use for decades. New challenges in vaccine development have been met with new technologies in vaccine research. Many of the newer vaccines are now being developed by recombinant DNA technology. For example, chimeric virus vaccines have been developed using infectious clone technology for many of the arboviruses including, WNV, JEV, and TBEV. Other successful approaches have involved the use of naked DNA encoding and subsequently expressing the desired protective epitopes. Naked DNA vaccines have been used for TBEV and JEV and are currently under development for use against WNV. The development of less expensive, more authentic animal models to evaluate new vaccines against arboviral diseases will become increasingly important as these new approaches in vaccine research are realized. This article reviews the current status of vaccines, both approved for use and those in developmental stages, against the major arboviral encephalitides causing human disease. In addition, research on animal models, both past and present, for these diseases are discussed.

Determination of natural versus laboratory human infection with Mayaro virus by molecular analysis.

A laboratory worker developed clinical signs of infection with Mayaro virus (Togaviridae), an arbovirus of South and Central America, 6 days after preparation of Mayaro viral antigen and 10 days after a trip to a rain forest. There was no evidence of skin lesions during the antigen preparation, and level 3 containment safety measures were followed. Therefore, molecular characterization of the virus was undertaken to identify the source of infection. RT-PCR and DNA sequence comparisons proved the infection was with the laboratory strain. Airborne Mayaro virus contamination is thus a hazard to laboratory personnel.

Importancia de la microscopía electrónica de transmisión en el diagnóstico de la epidemia de encefalitis equina venezolana de 1995 en la Guajira Venezolana / The importance of transmission electron microscopy in the diagnosis of venezuelan equine encephalitis during the epidemic of 1995 in the venezuelan Guajira

Se estudió con el microscopio electrónico de transmisión el cerebro de 25 ratones lactantes, inoculados intercerebralmente con el sobrenadante de células VERO cultivadas e infectadas con el virus de la EEV, como control positivo, con muestras de suero o líquido cefalorraquídeo de pacientes con síntomas y signos de encefalitis, con sueros de pacientes sanos, con sueros de equinos enfermos y con solución borato-salina de albúmina bovina, como control negativo. Las muestras se tomaron del brote epizoótico y epidémico en Octubre del año 1995 en la región de la Guajira Venezolana al norte del Estado Zulia. El estudio ultraestructural se hizo a ciegas, pero, confirmo la presencia de pacientes de Togavirus en el 100 por ciento de los casos examinados cuando correspondían a muestras virológicamente positivas. Se destaca la utilidad, precisión y la rapidez del método empleado

Porcine reproductive and respiratory syndrome: NEB-1 PRRSV infection did not potentiate bacterial pathogens.

A 2-phase study was conducted to evaluate the ability of the NEB-1 strain of porcine reproductive and respiratory syndrome virus (PRRSV) to potentiate common bacterial pathogens of swine. In phase I, 25 of 50 4-5-week-old specific-pathogen-free (SPF) pigs were exposed to NEB-1 PRRSV (day 0). Seven days after virus inoculation, 8 groups received 1 of 4 bacterial pathogens: Haemophilus parasuis, Streptococcus suis, Salmonella cholerasuis, and Pasteurella multocida. The ability of NEB-1 PRRSV to produce clinical disease, viremia, neutralizing antibody, gross and microscopic lesions and to potentiate bacterial pathogens was assessed. Response to NEB-1 PRRSV was similar among inoculated pigs; prolonged hyperthermia, lethargy, mild to moderate dyspnea, and cutaneous erythema were consistent clinical signs. No clinical differences were observed in groups after bacterial challenge. Virus was isolated from serum at weekly intervals through the end of the study, and all PRRSV-inoculated pigs had seroconverted by study termination. Two of 5 pigs died in non-PRRSV-inoculated groups challenged with H. parasuis and Streptococcus suis. Mortality in PRRSV-infected pigs was limited to 1 of 5 pigs from the Salmonella cholerasuis-challenged group. Gross lesions were seen in pigs dying after inoculation in H. parasuis- and Streptococcus suis-inoculated groups, in Salmonella cholerasuis- and P. multocida-challenged pigs, and in 1 non-PRRSV-inoculated control pig. Microscopic lesions consisted of mild to moderate proliferative interstitial pneumonia, nonsuppurative myocarditis, lymphoid hyperplasia, and nonsuppurative encephalitis in PRRSV-inoculated pigs. Findings in phase I indicated that NEB-1 PRRSV does not potentiate bacterial disease while inducing consistent clinical signs, viremia, seroconversion, and microscopic lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation and experimental oral transmission in pigs of a porcine reproductive and respiratory syndrome virus isolate.

A virus inducing a cytopathic effect on porcine alveolar macrophages was isolated from the lungs of a pig with respiratory problems and lesions of proliferative and necrotizing pneumonia. The isolate was found to react with porcine reproductive and respiratory syndrome virus (PRRSV) monoclonal antibodies by indirect immunofluorescence and was designated LHVA-93-3. The virus could also be propagated on the MARC-145 cell line. The LHVA-93-3 macrophage-passaged isolate was inoculated orally or intranasally in four-week-old specific pathogen-free pigs. Histologically, focal to multifocal lesions of proliferative, necrotizing and interstitial pneumonia could be observed in the lungs of pigs inoculated orally or intranasally, 6 and 10 days post-inoculation. Virus could be reisolated from essentially the same tissues including serum following both routes of infection. The distribution of PRRSV antigens in fixed tissues as determined by immunogold silver staining (IGSS) was similar in orally or intranasally inoculated pigs. The results of this experimental transmission study indicate that pigs may become infected by PRRSV following oral as well as intranasal exposure.

A highly virulent togavirus-like agent associated with the fulminating disease of guinea fowl.

During a 1986 natural lethal outbreak of fulminating disease in guinea poult flocks in southwestern France, enveloped virus particles were consistently observed in the gut contents of infected birds. For the present study, a protocol was developed for the purification of these particles. Sucrose-banded virus obtained from birds infected experimentally with virus from the outbreak was found to have a buoyant density of 1.18 g/ml. The purified virus showed hemagglutinating activity, was shown by electron microscopy to have a togavirus-like morphology, and also was shown to be transmissible and pathogenic through oral ingestion. In addition, other enveloped particles have been occasionally detected in gut contents of both infected and uninfected birds; the improbability of the viral nature of these interfering particles is discussed.

Different pathogenicity of encephalitic togaviruses in organotypic cultures of spinal cord slices.

The pathogenicity of two encephalitic Togaviruses, Sindbis virus (SV), an alphavirus, and West Nile virus (WNV), a flavivirus, was studied in organotypic cultures of fetal mouse spinal cord slices grown in roller tubes. After about 3 weeks in vitro, during which time the cultures became abundantly myelinated, they were infected either by 5 X 10(5) PFU SV or by 5 X 10(6) PFU WNV per culture. The viruses caused different patterns of cytopathogenicity: SV induced severe cytotoxicity in all glia cells and neurons with concomitant demyelination within 48 hr. In contrast, WNV, even 4 days after infection, caused only mild cytopathic effects mainly to neurons and astrocytes and a slight degree of damage to the myelin sheath. A most remarkable finding was the entrapment of WNV particles in the interperiod lines of the myelin sheaths. Treatment of cultures with mouse alpha and beta interferon prior to their infection with either virus protected the cultures from any viral damage. Long-term exposure of non-infected control organotypic cultures of fetal spinal cord slices to mouse interferons had no significant effect on neuronal and glial differentiation, and myelin formation.