Differential Susceptibility and Innate Immune Response of Aedes aegypti and Aedes albopictus to the Haitian Strain of the Mayaro Virus

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.

Evolutionary Profile of Mayaro Virus in the Americas: An Update into Genome Variability

The Mayaro virus (MAYV) is an arbovirus with emerging potential, though with a limited understanding of its epidemiology and evolution due to the lack of studies and surveillance. Here, we investigated 71 MAYV genome sequences from the Americas available at GenBank and characterized the phylogenetic relationship among virus strains. A phylogenetic analysis showed that sequences were grouped according to the genotypes L, D, and N. Genotype D sequences were closely related to sequences collected in adjacent years and from their respective countries, suggesting that isolates may have originated from circulating lineages. The coalescent analysis demonstrated similar results, indicating the continuous circulation of the virus between countries as well. An unidentified sequence from the USA was grouped with genotype D, suggesting the insertion of this genotype in the country. Furthermore, the recombination analysis detected homologous and three heterologous hybrids which presented an insertion into the nsP3 protein. Amino acid substitutions among sequences indicated selective pressure sites, suggesting viral adaptability. This also impacted the binding affinity between the E1-E2 protein complex and the Mxra8 receptor, associated with MAYV entry into human cells. These results provide information for a better understanding of genotypes circulating in the Americas.

A Review of Pathogens Transmitted by the Container-Inhabiting Mosquitoes, Aedes Albopictus, A Global Public Health Threat

Dengue virus (DENV), Chikungunya virus (CHIKV), and Zika virus (ZIKV) are highly pathogenic human arboviruses transmitted by the Aedes (Stegomyia) albopictus (Skuse) (Diptera: Culicidae) or Ae. Albopictus mosquito. These arboviruses are responsible for causing fever, hemorrhagic conditions, and neurological diseases in humans post-bite from an infected Aedes mosquito. Over the past 80 years, the Ae. albopictus has infested every habitable continent, bar Antarctica, thereby escalating the probability of global insect-borne infectious disease outbreaks. This research follows the global transmission pattern of Ae. albopictus and provides a summary of disease prevention and control strategies for mosquito-borne infections, as implemented by the World Health Organization (WHO) and both Asian and European countries. Consequently, this study can aid in the prevention and control of mosquito-borne diseases while acting as a basis for international collaboration on effectively managing arbovirus infection issues in public health.

Virucidal antiviral activity of Maytenus quadrangulata extract against Mayaro virus: Evidence for the presence of catechins

ETHNOPHARMACOLOGICAL RELEVANCE

Mayaro virus (MAYV) is an arbovirus endemic to the Amazon region, which comprises the states of the North and Midwest region of Brazil and encompasses the largest tropical forest in the world, the Amazon Forest. The confirmation of its potential transmission by Aedes aegypti and recent cases in Brazil, mainly in large centers in the northern region, led to the classification of Mayaro fever as an emerging disease. Traditional medicine is commonly used to treat various diseases, mainly by local riverside populations. Some species of the genus Maytenus, which have similar morphologies, are popularly used to treat infections and inflammations. In this context, our research group has studied and confirmed the antiviral activity of several plant-derived compounds. However, several species of this same genus have not been studied and therefore deserve attention.

AIM OF THE STUDY

This study aimed to demonstrate the effects of ethyl acetate extracts of leaves (LAE) and branches (TAE) of Maytenus quadrangulata against MAYV.

MATERIALS AND METHODS

Mammalian cells (Vero cells) were used to evaluate the cytotoxicity of the extracts. After cell infection by MAYV and the treatment with the extracts, we evaluated the selectivity index (SI), the virucidal effect, viral adsorption and internalization, and the effect on viral gene expression. The antiviral action was confirmed by quantifying the viral genome using RT-qPCR and by analyzing the effect on virus yield in infected cells. The treatment was performed based on the effective concentration protective for 50% of the infected cells (EC₅₀).

RESULTS

The leaves (LAE; EC₅₀ 12.0 μg/mL) and branches (TAE; EC₅₀ 101.0 μg/mL) extracts showed significative selectivity against the virus, with SI values of 79.21 and 9.91, respectively, which were considered safe. Phytochemical analysis revealed that the antiviral action was associated with the presence of catechins, mainly in LAE. This extract was chosen for the subsequent studies since it reduced the viral cytopathic effect and virus production, even at high viral loads [MOI (multiplicity of infection) 1 and 5]. The effects of LAE resulted in a marked reduction in viral gene expression. The viral title was drastically reduced when LAE was added to the virus before infection or during replication stages, reducing virus production up to 5-log units compared to infected and untreated cells.

CONCLUSION

Through kinetic replication, MAYV was not detected in Vero cells treated with LAE throughout the viral cycle. The virucidal effect of LAE inactivates the viral particle and can intercept the virus at the end of the cycle when it gains the extracellular environment. Therefore, LAE is a promising source of antiviral agents.

Susceptibility of Aedes albopictus, Ae. aegypti and human populations to Ross River virus in Kuala Lumpur, Malaysia

BACKGROUND

Emerging arboviruses such as chikungunya and Zika viruses have unexpectedly caused widespread outbreaks in tropical and subtropical regions recently. Ross River virus (RRV) is endemic in Australia and has epidemic potential. In Malaysia, Aedes mosquitoes are abundant and drive dengue and chikungunya outbreaks. We assessed risk of an RRV outbreak in Kuala Lumpur, Malaysia by determining vector competence of local Aedes mosquitoes and local seroprevalence as a proxy of human population susceptibility.

METHODOLOGY/PRINCIPAL FINDINGS

We assessed oral susceptibility of Malaysian Ae. aegypti and Ae. albopictus by real-time PCR to an Australian RRV strain SW2089. Replication kinetics in midgut, head and saliva were determined at 3 and 10 days post-infection (dpi). With a 3 log10 PFU/ml blood meal, infection rate was higher in Ae. albopictus (60%) than Ae. aegypti (15%; p<0.05). Despite similar infection rates at 5 and 7 log10 PFU/ml blood meals, Ae. albopictus had significantly higher viral loads and required a significantly lower median oral infectious dose (2.7 log10 PFU/ml) than Ae. aegypti (4.2 log10 PFU/ml). Ae. albopictus showed higher vector competence, with higher viral loads in heads and saliva, and higher transmission rate (RRV present in saliva) of 100% at 10 dpi, than Ae. aegypti (41%). Ae. aegypti demonstrated greater barriers at either midgut escape or salivary gland infection, and salivary gland escape. We then assessed seropositivity against RRV among 240 Kuala Lumpur inpatients using plaque reduction neutralization, and found a low rate of 0.8%.

CONCLUSIONS/SIGNIFICANCE

Both Ae. aegypti and Ae. albopictus are susceptible to RRV, but Ae. albopictus displays greater vector competence. Extensive travel links with Australia, abundant Aedes vectors, and low population immunity places Kuala Lumpur, Malaysia at risk of an imported RRV outbreak. Surveillance and increased diagnostic awareness and capacity are imperative to prevent establishment of new arboviruses in Malaysia.

Dynamic of Mayaro Virus Transmission in Aedes aegypti, Culex quinquefasciatus Mosquitoes, and a Mice Model

Mayaro virus (MAYV) is transmitted by Haemagogus spp. mosquitoes and has been circulating in Amazon areas in the North and Central West regions of Brazil since the 1980s, with an increase in human case notifications in the last 10 years. MAYV introduction in urban areas is a public health concern as infections can cause severe symptoms similar to other alphaviruses. Studies with Aedes aegypti have demonstrated the potential vector competence of the species and the detection of MAYV in urban populations of mosquitoes. Considering the two most abundant urban mosquito species in Brazil, we investigated the dynamics of MAYV transmission by Ae. aegypti and Culex quinquefasciatus in a mice model. Mosquito colonies were artificially fed with blood containing MAYV and infection (IR) and dissemination rates (DR) were evaluated. On the 7th day post-infection (dpi), IFNAR BL/6 mice were made available as a blood source to both mosquito species. After the appearance of clinical signs of infection, a second blood feeding was performed with a new group of non-infected mosquitoes. RT-qPCR and plaque assays were carried out with animal and mosquito tissues to determine IR and DR. For Ae. aegypti, we found an IR of 97.5-100% and a DR reached 100% in both 7 and 14 dpi. While IR and DR for Cx. quinquefasciatus was 13.1-14.81% and 60% to 80%, respectively. A total of 18 mice were used (test = 12 and control = 6) for Ae. aegypti and 12 (test = 8 and control = 4) for Cx. quinquefasciatus to evaluate the mosquito-mice transmission rate. All mice that were bitten by infected Ae. aegypti showed clinical signs of infection while all mice exposed to infected Cx. quinquefasciatus mosquitoes remained healthy. Viremia in the mice from Ae. aegypti group ranged from 2.5 × 10⁸ to 5 × 10⁹ PFU/mL. Ae. aegypti from the second blood feeding showed a 50% IR. Our study showed the applicability of an efficient model to complete arbovirus transmission cycle studies and suggests that the Ae. aegypti population evaluated is a competent vector for MAYV, while highlighting the vectorial capacity of Ae. aegypti and the possible introduction into urban areas. The mice model employed here is an important tool for arthropod-vector transmission studies with laboratory and field mosquito populations, as well as with other arboviruses.

Wolbachia wPip Blocks Zika Virus Transovarial Transmission in Aedes albopictus

Wolbachia is being developed as a biological tool to suppress mosquito populations and/or interfere with their transmitted viruses. Adult males with an artificial Wolbachia infection have been released, successfully yielding population suppression in multiple field trials. The main characteristic of the artificial Wolbachia-infected mosquitoes used in the suppression program is the lower vector competence than that in native infected/uninfected mosquitoes in horizontal and vertical transmission. Our previous studies have demonstrated that the Aedes albopictus HC line infected with a trio of Wolbachia strains exhibited almost complete blockade of dengue virus (DENV) and Zika virus (ZIKV) in horizontal and vertical transmission. However, the extent to which Wolbachia inhibits virus transovarial transmission is unknown since no studies have been performed to determine whether Wolbachia protects ovarian cells against viral infection. Here, we employed ovarian cells of the Ae. albopictus GUA (a wild-type mosquito line superinfected with two native Wolbachia strains, wAlbA and wAlbB), HC, and GT lines (tetracycline-cured, Wolbachia-uninfected mosquitoes), which exhibit key traits, and compared them to better understand how Wolbachia inhibits ZIKV transovarial transmission. Our results showed that the infection rate of adult GT progeny was significantly higher than that of GUA progeny during the first and second gonotrophic cycles. In contrast, the infection rates of adult GT and GUA progeny were not significantly different during the third gonotrophic cycle. All examined adult HC progeny from three gonotrophic cycles were negative for ZIKV infection. A strong negative linear correlation existed between Wolbachia density and ZIKV load in the ovaries of mosquitoes. Although there is no obvious coexistence area in the ovaries for Wolbachia and ZIKV, host immune responses may play a role in Wolbachia blocking ZIKV expansion and maintenance in the ovaries of Ae. albopictus. These results will aid in understanding Wolbachia-ZIKV interactions in mosquitoes. IMPORTANCE Area-wide application of Wolbachia to suppress mosquito populations and their transmitted viruses has achieved success in multiple countries. However, the mass release of Wolbachia-infected male mosquitoes involves a potential risk of accidentally releasing fertile females. In this study, we employed ovarian cells of the Ae. albopictus GUA, HC, and GT lines, which exhibit key traits, and compared them to better understand how Wolbachia inhibits ZIKV transovarial transmission. Our results showed an almost complete blockade of ZIKV transmission in HC female mosquitoes. Wolbachia in natively infected GUA mosquitoes negative affected ZIKV, and this interference was shown by slightly lower loads than those in HC mosquitoes. Overall, our work helps show how Wolbachia blocks ZIKV expansion and maintenance in the ovaries of Ae. albopictus and aids in understanding Wolbachia-ZIKV interactions in mosquitoes.

Coupled small molecules target RNA interference and JAK/STAT signaling to reduce Zika virus infection in Aedes aegypti

The recent global Zika epidemics have revealed the significant threat that mosquito-borne viruses pose. There are currently no effective vaccines or prophylactics to prevent Zika virus (ZIKV) infection. Limiting exposure to infected mosquitoes is the best way to reduce disease incidence. Recent studies have focused on targeting mosquito reproduction and immune responses to reduce transmission. Previous work has evaluated the effect of insulin signaling on antiviral JAK/STAT and RNAi in vector mosquitoes. Specifically, insulin-fed mosquitoes resulted in reduced virus replication in an RNAi-independent, ERK-mediated JAK/STAT-dependent mechanism. In this work, we demonstrate that targeting insulin signaling through the repurposing of small molecule drugs results in the activation of both RNAi and JAK/STAT antiviral pathways. ZIKV-infected Aedes aegypti were fed blood containing demethylasterriquinone B1 (DMAQ-B1), a potent insulin mimetic, in combination with AKT inhibitor VIII. Activation of this coordinated response additively reduced ZIKV levels in Aedes aegypti. This effect included a quantitatively greater reduction in salivary gland ZIKV levels up to 11 d post-bloodmeal ingestion, relative to single pathway activation. Together, our study indicates the potential for field delivery of these small molecules to substantially reduce virus transmission from mosquito to human. As infections like Zika virus are becoming more burdensome and prevalent, understanding how to control this family of viruses in the insect vector is an important issue in public health.

Emergent Arboviruses: A Review About Mayaro virus and Oropouche orthobunyavirus

Arthropod-borne viruses have a significant impact on public health worldwide, and their (re) emergence put aside the importance of other circulating arboviruses. Therefore, this scoping review aims to identify and characterize the literature produced in recent years, focusing on aspects of two arboviruses: Mayaro virus and Oropouche orthobunyavirus. The Mayaro and Oropouche viruses were isolated for the first time in Trinidad and Tobago in 1954 and 1955, respectively, and have more recently caused numerous outbreaks. In addition, they have been incriminated as candidate diseases for human epidemics. These viruses have been drawing the attention of public health authorities worldwide following recent outbreaks. To determine the global epidemiological profile of these viruses, we used the Dimensions Database, which contains more than 100 million publications. In general, we identified 327 studies published from 1957 to 2020 for Mayaro virus, and 152 studies published from 1961 to 2020 for Oropouche orthobunyavirus. Interestingly, we observed that Mayaro and Oropouche had a significant increase in the number of publications in recent years. Thus, this comprehensive review will be helpful to guide future research based on the identified knowledge gaps.

Favipiravir Inhibits Mayaro Virus Infection in Mice

Mayaro virus (MAYV) is an emergent alphavirus that causes MAYV fever. It is often associated with debilitating symptoms, particularly arthralgia and myalgia. MAYV infection is becoming a considerable health issue that, unfortunately, lacks a specific antiviral treatment. Favipiravir, a broad-spectrum antiviral drug, has recently been shown to exert anti-MAYV activity in vitro. In the present study, the potential of Favipiravir to inhibit MAYV replication in an in vivo model was evaluated. Immunocompetent mice were orally administrated 300 mg/kg/dose of Favipiravir at pre-, concurrent-, or post-MAYV infection. The results showed a significant reduction in infectious viral particles and viral RNA transcripts in the tissues and blood of the pre- and concurrently treated infected mice. A significant reduction in the presence of both viral RNA transcript and infectious viral particles in the tissue and blood of pre- and concurrently treated infected mice was observed. By contrast, Favipiravir treatment post-MAYV infection did not result in a reduction in viral replication. Interestingly, Favipiravir strongly decreased the blood levels of the liver disease markers aspartate- and alanine aminotransferase in the pre- and concurrently treated MAYV-infected mice. Taken together, these results suggest that Favipiravir is a potent antiviral drug when administered in a timely manner.

Profiling Transcriptional Response of Dengue-2 Virus Infection in Midgut Tissue of Aedes aegypti

Understanding the mosquito antiviral response could reveal target pathways or genes of interest that could form the basis of new disease control applications. However, there is a paucity of data in the current literature in understanding antiviral response during the replication period. To illuminate the gene expression patterns in the replication stage, we collected gene expression data at 2.5 days after Dengue-2 virus (DENV-2) infection. We sequenced the whole transcriptome of the midgut tissue and compared gene expression levels between the control and virus-infected group. We identified 31 differentially expressed genes. Based on their function, we identified that those genes fell into two major functional categories - (1) nucleic acid/protein process and (2) immunity/oxidative stress response. Our study has identified candidate genes that can be followed up for gene overexpression/inhibition experiments to examine if the perturbed gene interaction may impact the mosquito’s immune response against DENV. This is an important step to understanding how mosquitoes eliminate the virus and provides an important foundation for further research in developing novel dengue control strategies.

Mayaro Virus: The Potential Role of Microbiota and Wolbachia

The Mayaro virus (MAYV) is an arbovirus that circulates mainly in tropical forests or rural areas in Latin America and is transmitted mainly by Haemagogus mosquitoes. The objective of this study was to evaluate the vector competence, microbiome, and the presence of Wolbachia in three Aedes albopictus populations infected with MAYV. The vector competence was assessed based on viral infection and transmission by RT-qPCR. In addition, the microbiome was evaluated by amplification of the 16S rRNA V4 region and PCR to detect the presence of Wolbachia (strain wAlbA/wAlbB). Our results show that all three populations were susceptible to MAYV infection. The potential transmission of the MAYV was consistent in all populations of naïve mosquitoes injected (more than 50%). The microbiome analysis revealed 118 OTUs (operational taxonomic unit) from the three populations, 8 phyla, 15 classes, 26 orders, 35 families, 65 genera, and 53 species. All populations had Pseudomonas and Wolbachia as predominant genera. There was no difference between the variables for MAYV and Wolbachia (wAlbA or wAlbB) in the abdomen. However, in the head + thorax samples at 14 dpi, there was a difference between the two populations, indicating a possible correlation between the presence of Wolbachia (wAlbB) and infection. Overall, we show evidence that Ae. albopictus displays significant infection and transmission competence for the MAYV in the laboratory, and its bacterial microbiota play an important role in the host, mainly the strains of Wolbachia. The influence of the intestinal microbiota of Ae. albopictus is poorly known, and a better understanding of these interactions would open new perspectives for disease control through the manipulation of microbial communities. The exact contribution of this mosquito species to the transmission of the MAYV in the field remains to be confirmed.

Mayaro Virus Infects Human Brain Cells and Induces a Potent Antiviral Response in Human Astrocytes

Mayaro virus (MAYV) and chikungunya virus (CHIKV) are known for their arthrotropism, but accumulating evidence shows that CHIKV infections are occasionally associated with serious neurological complications. However, little is known about the capacity of MAYV to invade the central nervous system (CNS). We show that human neural progenitors (hNPCs), pericytes and astrocytes are susceptible to MAYV infection, resulting in the production of infectious viral particles. In primary astrocytes, MAYV, and to a lesser extent CHIKV, elicited a strong antiviral response, as demonstrated by an increased expression of several interferon-stimulated genes, including ISG15, MX1 and OAS2. Infection with either virus led to an enhanced expression of inflammatory chemokines, such as CCL5, CXCL10 and CXCL11, whereas MAYV induced higher levels of IL-6, IL-12 and IL-15 in these cells. Moreover, MAYV was more susceptible than CHIKV to the antiviral effects of both type I and type II interferons. Taken together, this study shows that although MAYV and CHIKV are phylogenetically related, they induce different types of antiviral responses in astrocytes. This work is the first to evaluate the potential neurotropism of MAYV and shows that brain cells and particularly astrocytes and hNPCs are permissive to MAYV, which, consequently, could lead to MAYV-induced neuropathology.

Transmission potential of Mayaro virus by Aedes albopictus, and Anopheles quadrimaculatus from the USA

BACKGROUND

Mayaro virus (MAYV; Alphavirus, Togaviridae) is an emerging pathogen endemic in South American countries. The increase in intercontinental travel and tourism-based forest excursions has resulted in an increase in MAYV spread, with imported cases observed in Europe and North America. Intriguingly, no local transmission of MAYV has been reported outside South America, despite the presence of potential vectors.

METHODS

We assessed the vector competence of Aedes albopictus from New York and Anopheles quadrimaculatus for MAYV.

RESULTS

The results show that Ae. albopictus from New York and An. quadrimaculatus are competent vectors for MAYV. However, Ae. albopictus was more susceptible to infection. Transmission rates increased with time for both species, with rates of 37.16 and 64.44% for Ae. albopictus, and of 25.15 and 48.44% for An. quadrimaculatus, respectively, at 7 and 14 days post-infection.

CONCLUSIONS

Our results suggest there is a risk of further MAYV spread throughout the Americas and autochthonous transmission in the USA. Preventive measures, such as mosquito surveillance of MAYV, will be essential for early detection.

Adenoviral-Vectored Mayaro and Chikungunya Virus Vaccine Candidates Afford Partial Cross-Protection From Lethal Challenge in A129 Mouse Model

Mayaro (MAYV) and chikungunya viruses (CHIKV) are vector-borne arthritogenic alphaviruses that cause acute febrile illnesses. CHIKV is widespread and has recently caused large urban outbreaks, whereas the distribution of MAYV is restricted to tropical areas in South America with small and sporadic outbreaks. Because MAYV and CHIKV are closely related and have high amino acid similarity, we investigated whether vaccination against one could provide cross-protection against the other. We vaccinated A129 mice (IFNAR -/-) with vaccines based on chimpanzee adenoviral vectors encoding the structural proteins of either MAYV or CHIKV. ChAdOx1 May is a novel vaccine against MAYV, whereas ChAdOx1 Chik is a vaccine against CHIKV already undergoing early phase I clinical trials. We demonstrate that ChAdOx1 May was able to afford full protection against MAYV challenge in mice, with most samples yielding neutralizing PRNT80 antibody titers of 1:258. ChAdOx1 May also provided partial cross-protection against CHIKV, with protection being assessed using the following parameters: survival, weight loss, foot swelling and viremia. Reciprocally, ChAdOx1 Chik vaccination reduced MAYV viral load, as well as morbidity and lethality caused by this virus, but did not protect against foot swelling. The cross-protection observed is likely to be, at least in part, secondary to cross-neutralizing antibodies induced by both vaccines. In summary, our findings suggest that ChAdOx1 Chik and ChAdOx1 May vaccines are not only efficacious against CHIKV and MAYV, respectively, but also afford partial heterologous cross-protection.

Mayaro Virus Pathogenesis and Transmission Mechanisms

Mayaro virus (MAYV), isolated for the first time in Trinidad and Tobago, has captured the attention of public health authorities worldwide following recent outbreaks in the Americas. It has a propensity to be exported outside its original geographical range, because of the vast distribution of its vectors. Moreover, most of the world population is immunologically naïve with respect to infection with MAYV which makes this virus a true threat. The recent invasion of several countries by Aedesalbopictus underscores the risk of potential urban transmission of MAYV in both tropical and temperate regions. In humans, the clinical manifestations of MAYV disease range from mild fever, rash, and joint pain to arthralgia. In the absence of a licensed vaccine and clinically proven therapeutics against Mayaro fever, prevention focuses mainly on household mosquito control. However, as demonstrated for other arboviruses, mosquito control is rather inefficient for outbreak management and alternative approaches to contain the spread of MAYV are therefore necessary. Despite its strong epidemic potential, little is currently known about MAYV. This review addresses various aspects of MAYV, including its epidemiology, vector biology, mode of transmission, and clinical complications, as well as the latest developments in MAYV diagnosis.

The RNAi Pathway Is Important to Control Mayaro Virus Infection in Aedes aegypti but not for Wolbachia-Mediated Protection

Mayaro virus (MAYV), a sylvatic arbovirus belonging to the Togaviridae family and Alphavirus genus, is responsible for an increasing number of outbreaks in several countries of Central and South America. Despite Haemagogus janthinomys being identified as the main vector of MAYV, laboratory studies have already demonstrated the competence of Aedes aegypti to transmit MAYV. It has also been demonstrated that the WolbachiawMel strain is able to impair the replication and transmission of MAYV in Ae. aegypti. In Ae. aegypti, the small interfering RNA (siRNA) pathway is an important antiviral mechanism; however, it remains unclear whether siRNA pathway acts against MAYV infection in Ae. aegypti. The main objective of this study was to determine the contribution of the siRNA pathway in the control of MAYV infection. Thus, we silenced the expression of AGO2, an essential component of the siRNA pathway, by injecting dsRNA-targeting AGO2 (dsAGO2). Our results showed that AGO2 is required to control MAYV replication upon oral infection in Wolbachia-free Ae. aegypti. On the other hand, we found that Wolbachia-induced resistance to MAYV in Ae. aegypti is independent of the siRNA pathway. Our study brought new information regarding the mechanism of viral protection, as well as on Wolbachia mediated interference.

Epidemic Alphaviruses: Ecology, Emergence and Outbreaks

Over the past century, the emergence/reemergence of arthropod-borne zoonotic agents has been a growing public health concern. In particular, agents from the genus Alphavirus pose a significant risk to both animal and human health. Human alphaviral disease presents with either arthritogenic or encephalitic manifestations and is associated with significant morbidity and/or mortality. Unfortunately, there are presently no vaccines or antiviral measures approved for human use. The present review examines the ecology, epidemiology, disease, past outbreaks, and potential to cause contemporary outbreaks for several alphavirus pathogens.

Vector competence of Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus mosquitoes for Mayaro virus

Newly emerging or re-emerging arthropod-borne viruses (arboviruses) are important causes of human morbidity and mortality worldwide. Arboviruses such as Dengue (DENV), Zika (ZIKV), Chikungunya (CHIKV), and West Nile virus (WNV) have undergone extensive geographic expansion in the tropical and sub-tropical regions of the world. In the Americas the main vectors of DENV, ZIKV, and CHIKV are mosquito species adapted to urban environments, namely Aedes aegypti and Aedes albopictus, whereas the main vector of WNV is Culex quinquefasciatus. Given the widespread distribution in the Americas and high permissiveness to arbovirus infection, these mosquito species may play a key role in the epidemiology of other arboviruses normally associated with sylvatic vectors. Here, we test this hypothesis by determining the vector competence of Ae. aegypti, Ae. albopictus, and Cx. quinquefasciatus to Mayaro (MAYV) virus, a sylvatic arbovirus transmitted mainly by Haemagogus janthinomys that has been causing an increasing number of outbreaks in South America, namely in Brazil. Using field mosquitoes from Brazil, female mosquitoes were experimentally infected, and their competence for infection and transmission rates of MAYV was evaluated. We found consistent infection rate for MAYV in Ae. aegypti (57.5%) and Ae. albopictus (61.6%), whereas very low rates were obtained for Cx. quinquefasciatus (2.5%). Concordantly, we observed high potential transmission ability in Ae. aegypti and Ae. albopictus (69.5% and 71.1% respectively), in contrast to Cx. quinquefasciatus, which could not transmit the MAYV. Notably, we found that very low quantities of virus present in the saliva (undetectable by RT-qPCR) were sufficiently virulent to guarantee transmission. Although Ae. aegypti and Ae. albopictus mosquitoes are not the main vectors for MAYV, our studies suggest that these mosquitoes could play a significant role in the transmission of this arbovirus, since both species showed significant vector competence for MAYV (Genotype D), under laboratory conditions.