The Current Progress in the Quest for Vaccines Against the Semliki Forest Virus Complex

The Semliki Forest virus (SFV) complex comprises of arboviruses that are transmitted by arthropod vectors and cause acute febrile illness in humans. In the last seven decades, re-emergence of these viruses has resulted in numerous outbreaks globally, affecting regions including Africa, Americas, Asia, Europe and the Caribbean. These viruses are transmitted to humans by the bite of infected mosquitoes. Symptoms of infection include high fever, severe joint pain, skin rash, muscle pain and headache. Fatal cases were reported, and mortality rate increased during the epidemic of these viruses. There is therefore a need to control the spread of these emerging arboviruses. Given that vaccination is one of the most effective ways to protect populations against viral outbreaks, efforts have been made to develop and test potential vaccine candidates. However, there are still no licensed vaccines available against the medically important viruses in the SFV complex. This review first summarizes the current knowledge of the SFV complex disease pathogenesis. Next, seven strategies that have been applied in vaccine development against these viruses are reviewed, indicating the immune response and efficacies of these vaccine candidates in in vivo models of infection. Finally, the more promising candidates that have entered clinical trials are discussed and insights into the future development of vaccines for viruses of the SFV complex are given.

Potential therapeutics and vaccines: Current progress and challenges in developing antiviral treatments or vaccines for Oropouche virus

Oropouche virus (OROV), an emerging arbovirus, poses a significant public health challenge in tropical and subtropical regions, with no licensed vaccines or antiviral therapies currently available. This review explores recent advancements in therapeutic strategies and vaccine development for OROV, focusing on molecular mechanisms of viral replication, identification of potential antiviral targets, and the role of immunotherapy in managing infections. Promising antiviral candidates, including ribavirin, mycophenolic acid, and interferon, have demonstrated efficacy in in vitro studies, offering a foundation for further investigation. The challenges of preclinical and clinical development, such as high mutation rates, immune response variability, and vaccine delivery hurdles, are critically analyzed. By addressing the progress and remaining gaps, this article aims to provide a comprehensive overview to inform future research and facilitate the development of effective antiviral strategies and vaccines for OROV.

Characterisation of the virome of Culicoides brevitarsis Kieffer (Diptera: Ceratopogonidae), a vector of bluetongue virus in Australia

Culicoides spp., a common biting midge genus, are haematophagous insects that can transmit pathogens to humans and other animals. Some species transmit arboviruses, including bluetongue virus, epizootic haemorrhagic disease virus, African horse sickness virus and Schmallenberg virus to vertebrates, which can be detrimental to livestock and wild animals. Culicoides spp. can also have a diversity of insect-specific viruses (ISVs) that can only be transmitted between insects and others related to known arboviruses. For Culicoides brevitarsis and other Culicoides spp. in Australia, the virome is largely unexplored. We used high-throughput sequencing to characterise the virome of C. brevitarsis collected from Casino, New South Wales, Australia. For virus detection, the total RNA was extracted from pools of C. brevitarsis followed by rRNA depletion and Illumina short-read-based RNA sequencing. The reads were quality-checked, filtered and assembled into contigs, compared with the non-redundant protein and conserved domain databases for viral detection and genome organisation, respectively. The phylogenetic analysis was used to further characterise the viruses. We detected new virus diversity including ten viruses belonging to eight different families with complete or near-complete coding regions. Seven of these were novel virus species belonging to the families: Chuviridae, Orthomyxoviridae, Peribunyaviridae, Qinviridae, Rhabdoviridae and Solemoviridae. In addition, the novel Peribunyaviridae virus should also be considered part of a new genus. Whilst most of the detected viruses grouped into families with viruses that can infect insects, animals or both, the novel species of Solemoviridae was closely related to an economically important plant pathogen, the sugarcane yellow leaf virus. Our quantitative PCR-based screening confirmed the absence of any Wolbachia endosymbiont within the collected samples. Furthermore, we detected fragments of three more virus families known to infect fungi and plants. The detection of potential arboviruses and ISVs in Culicoides spp. is important in understanding virus epidemiology.

Human brain tissue cultures: a unique ex vivo model to unravel the pathogenesis of neurotropic arboviruses

Arboviruses are transmitted by arthropods, and their spread from endemic to nonendemic regions has been accelerated by deforestation, climate change, and global mobility. Arbovirus infection in human results in symptoms ranging from mild to life-threatening, with the impairment of central nervous system functions being reported in severe cases. Despite its clinical relevance, the mechanisms by which arboviruses led to neural dysfunction are still poorly understood. The lack of a widespread human central nervous system model to study the virus-host interaction challenges the advance of our knowledge on these mechanisms. In this context, human brain-derived ex vivo models have the advantage of preserving cellular diversity, cell connections, and tissue cytoarchitecture found in human brain, raising them as a powerful strategy to elucidate the cellular-molecular alterations underlying brain diseases. Here, we review recent advances in the field of neurotropic arboviruses obtained using ex vivo human brain tissue as the experimental model.

Assessment of Mayaro virus vector competence of the mosquito Aedes aegypti (Linnaeus, 1762) populations in Argentine using dose-response assays

Mayaro virus (MAYV; Alphavirus: Togaviridae) is an emerging pathogen in Latin America, causing fever and polyarthritis. Sporadic outbreaks of MAYV have occurred in the region, with reported human cases being imported to Europe and North America. Although primarily a risk for those residing in the Amazon basin's tropical forests, recent reports highlight that urbanization would increase the risk of MAYV transmission in Latin America. Urban emergence depends on human susceptibility and the ability of mosquitos like Aedes aegypti  (Linnaeus, 1762) (Diptera: Culicidae) to transmit MAYV. Despite the absence of active MAYV transmission in Argentine, the risk of introduction is substantial due to human movement and the presence of Ae. aegypti in the region. This study aimed to evaluate the susceptibility of different Argentine Ae. aegypti populations to MAYV genotype L (MAYV-L) using dose-response assays and determine barriers to virus infection, dissemination and transmission. Immature mosquito stages were collected in Buenos Aires, Córdoba and Rosario cities. Female Ae. aegypti (F2) were orally infected by feeding on five concentrations of MAYV-L, ranging from 1.0 to 6.0 log10 PFU/mL. Abdomens, legs and saliva were analysed using viral plaque assays. Results revealed that MAYV-L between infection and dissemination were associated with viral doses rather than the population origin. Infection rates varied between 3% and 65%, with a 50% infectious dose >5.5 log10 PFU/mL. Dissemination occurred at 39%, with a 50% dissemination dose of ~6.0 log10 PFU/mL. Dissemination among infected mosquitoes ranged from 60% to 86%, and transmission from disseminated mosquitoes ranged from 11% to 20%. Argentine Ae. aegypti populations exhibited a need for higher viral doses of MAYV-L than those typically found in humans to become infected. In addition, only a small proportion of infected mosquitoes were capable of transmitting the virus. Understanding MAYV transmission in urban areas is crucial for public health interventions.

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.

Acridones as promising drug candidates against Oropouche virus

Oropouche virus (OROV) is an emerging vector-borne arbovirus found in South America that causes Oropouche fever, a febrile infection similar to dengue fever. It has a high epidemic potential, causing illness in over 500,000 cases diagnosed since the virus was first discovered in 1955. Currently, the prevention of human viral infection depends on vaccination, but availability for many viruses is limited, and they are classified as neglected viruses. At present, there are no vaccines or antiviral treatments available. An alternative approach to limiting the spread of the virus is to selectively disrupt viral replication mechanisms. Here, we demonstrate the inhibitory effect of acridones, which efficiently inhibited viral replication by 99.9 % in vitro. To evaluate possible mechanisms of action, we conducted tests with dsRNA, an intermediate in virus replication, as well as MD simulations, docking, and binding free energy analysis. The results showed a strong interaction between FAC21 and the OROV endonuclease, which possibly limits the interaction of viral RNA with other proteins. Therefore, our results suggest a dual mechanism of antiviral action, possibly caused by ds-RNA intercalation. In summary, our findings demonstrate that a new generation of antiviral drugs could be developed based on the selective optimization of molecules.

The Others: A Systematic Review of the Lesser-Known Arboviruses of the Insular Caribbean

The Caribbean enjoys a long-standing eminence as a popular tourist destination; however, over the years it has also amassed the sobriquet "arbovirus hotspot". As the planet warms and vectors expand their habitats, a cognizant working knowledge of the lesser-known arboviruses and the factors that influence their emergence and resurgence becomes essential. The extant literature on Caribbean arboviruses is spread across decades of published literature and is quite often difficult to access, and, in some cases, is obsolete. Here, we look at the lesser-known arboviruses of the insular Caribbean and examine some of the drivers for their emergence and resurgence. We searched the scientific literature databases PubMed and Google Scholar for peer-reviewed literature as well as scholarly reports. We included articles and reports that describe works resulting in serological evidence of the presence of arboviruses and/or arbovirus isolations in the insular Caribbean. Studies without serological evidence and/or arbovirus isolations as well as those including dengue, chikungunya, Zika, and yellow fever were excluded. Of the 545 articles identified, 122 met the inclusion criteria. A total of 42 arboviruses were identified in the literature. These arboviruses and the drivers that affect their emergence/resurgence are discussed.

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.

Targeting Host PIM Protein Kinases Reduces Mayaro Virus Replication

Mayaro virus (MAYV) manipulates cell machinery to successfully replicate. Thus, identifying host proteins implicated in MAYV replication represents an opportunity to discover potential antiviral targets. PIM kinases are enzymes that regulate essential cell functions and also appear to be critical factors in the replication of certain viruses. In this study we explored the consequences of PIM kinase inhibition in the replication of MAYV and other arboviruses. Cytopathic effects or viral titers in samples from MAYV-, Chikungunya-, Una- or Zika-infected cells treated with PIM kinase inhibitors were evaluated using an inverted microscope or plaque-forming assays. The expression of viral proteins E1 and nsP1 in MAYV-infected cells was assessed using an immunofluorescence confocal microscope or Western blot. Our results revealed that PIM kinase inhibition partially prevented MAYV-induced cell damage and also promoted a decrease in viral titers for MAYV, UNAV and ZIKV. The inhibitory effect of PIM kinase blocking was observed for each of the MAYV strains tested and also occurred as late as 8 h post infection (hpi). Finally, PIM kinase inhibition suppressed the expression of MAYV E1 and nsP1 proteins. Taken together, these findings suggest that PIM kinases could represent an antiviral target for MAYV and other arboviruses.