Transinfection and growth discrepancy of Drosophila Wolbachia strain wMel in cell lines of the mosquito Aedes albopictus

Aim: The Wolbachia strain wMel can protect Drosophila melanogaster against pathogenic RNA viruses. To analyse the potential of this inhibitory effect against arboviruses vectorized by these mosquitoes, we here first transinfected the Aedes albopictus Aa23 and C6/36 cell lines with the Wolbachia strain wMel and then monitored their infection dynamics. Methods and Results: Wolbachia strain wMel was transferred into A. albopictus Aa23 and C6/36 cell lines using the shell vial technique. The presence of the bacterium in the transinfected cells was monitored by quantitative PCR and fluorescence in situ hybridization. Bacteria could be detected in the cytoplasm of both the Aa23 and C6/36 cell lines. However, the dynamics and stability of the bacterial infection differed depending on the initial cell background. The Aa23 cell line, which had been treated with a tetracycline antibiotic 2 years previously to eliminate its natural Wolbachia wAlbB‐infecting strain, lost the introduced Wolbachia wMel strain after 12 passages postinfection. In contrast, the C6/36 cell line, which had originally been aposymbiotic, displayed a stable infection with Wolbachia wMel. The bacterial density in C6/36 was greater than that of the A. albopictus RML12 cell line from which the wMel strain had originated. Conclusions: Transient or persistent transinfection of A. albopictus Aa23 and C6/36 cell lines with Wolbachia wMel strain was achieved. The results indicate the influence of the genetic background of mosquito cells in maintaining Wolbachia originating from a distant dipteral host. Significance and Impact of the Study: The cell model built here can now be used to investigate the viral inhibitory effect of the Wolbachia wMel strain against arboviruses such as dengue and chikungunya, which are transmitted by the mosquito A. albopictus.     

Wolbachia modulates Chikungunya replication in Aedes albopictus

The Aedes albopictus mosquito has been involved as the principal vector of recent major outbreaks due to the chikungunya virus (CHIKV). The species is naturally infected by two strains of Wolbachia (wAlbA and wAlbB). Wolbachia infections are thought to have spread by manipulating the reproduction of their hosts; cytoplasmic incompatibility is the mechanism used by Wolbachia to invade natural populations of many insects including Ae. albopictus. Here, we report a study on the effects of removing Wolbachia from Ae. albopictus on CHIKV replication and examine the consequences of CHIKV infection on some life‐history traits (survival and reproduction) of Wolbachia‐free Ae. albopictus. We found that Wolbachia‐free mosquitoes maintained a highly heterogeneous CHIKV replication compared to Wolbachia‐infected individuals. In Wolbachia‐infected Ae. albopictus, the regular increase of CHIKV followed by a steady viral load from day 4 post‐infection onwards was concomitant with a decline in Wolbachia density. This profile was also detected when examining the two key organs for viral transmission, the midgut and the salivary glands. Moreover, Wolbachia‐free Ae. albopictus was not altered in life‐history traits such as survival, oviposition and hatching characteristics whether infected or not with CHIKV. We found that Wolbachia is not essential for viral replication, its presence could lead to optimize replication from day 4 post‐infection onwards, coinciding with a decrease in Wolbachia density. Wolbachia may regulate viral replication in Ae. albopictus, with consequences on survival and reproduction.     

Native Wolbachia from Aedes albopictus Blocks Chikungunya Virus Infection In Cellulo

Wolbachia, a widespread endosymbiont of terrestrial arthropods, can protect its host against viral and parasitic infections, a phenotype called "pathogen blocking". However, in some cases Wolbachia may have no effect or even enhance pathogen infection, depending on the host-Wolbachia-pathogen combination. The tiger mosquito Aedes albopictus is naturally infected by two strains of Wolbachia, wAlbA and wAlbB, and is a competent vector for different arboviruses such as dengue virus (DENV) and Chikungunya virus (CHIKV). Interestingly, it was shown in some cases that Ae. albopictus native Wolbachia strains are able to inhibit DENV transmission by limiting viral replication in salivary glands, but no such impact was measured on CHIKV replication in vivo. To better understand the Wolbachia/CHIKV/Ae. albopictus interaction, we generated a cellular model using Ae. albopictus derived C6/36 cells that we infected with the wAlbB strain. Our results indicate that CHIKV infection is negatively impacted at both RNA replication and virus assembly/secretion steps in presence of wAlbB. Using FISH, we observed CHIKV and wAlbB in the same mosquito cells, indicating that the virus is still able to enter the cell in the presence of the bacterium. Further work is needed to decipher molecular pathways involved in Wolbachia-CHIKV interaction at the cellular level, but this cellular model can be a useful tool to study the mechanism behind virus blocking phenotype induced by Wolbachia. More broadly, this underlines that despite Wolbachia antiviral potential other complex interactions occur in vivo to determine mosquito vector competence in Ae. albopictus.     

白纹伊蚊和埃及伊蚊对基孔肯雅病毒的易感性和传播性的研究

用４株基孔肯雅病毒经口感染白纹伊蚊和埃及伊蚊,进行了易感性和传播性的研究。结果表明,这两种蚊虫对基孔肯雅病毒易感。无论白纹伊蚊或埃及伊蚊,感染后第５－６天即可通过吸血将病毒传播给乳鼠,至第８－１３天,传播率可高达５５．５５％－１００％。感染蚊亦可经叮咬将病毒传播给小鸡。埃及伊蚊的易感性和传播率高于白纹伊蚊。实验还发现,不同来源毒株之间存在一定差异,如分离自云南白纹伊蚊的Ｍ８１株的感染率和传播率均高于其它毒株。这些结果表明,白纹伊蚊和埃及伊蚊在基孔肯雅病毒的保存和传播中起重要作用。     

Fitness advantage and cytoplasmic incompatibility in Wolbachia single- and superinfected Aedes albopictus

Wolbachia are obligate, maternally inherited, intracellular bacteria that infect numerous insects and other invertebrates. Wolbachia infections have evolved multiple mechanisms to manipulate host reproduction and facilitate invasion of naive host populations. One such mechanism is cytoplasmic incompatibility (CI) that occurs in many insect species, including Aedes albopictus (Asian tiger mosquito). The multiple Wolbachia infections that occur naturally in A. albopictus make this mosquito a useful system in which to study CI. Here, experiments employ mosquito strains that have been introgressed to provide genetically similar strains that harbor differing Wolbachia infection types. Cytoplasmic incompatibility levels, host longevity, egg hatch rates, and fecundity are examined. Crossing results demonstrate a pattern of additive unidirectional cytoplasmic incompatibility. Furthermore, relative to uninfected females, infected females are at a reproductive advantage due to both cytoplasmic incompatibility and a fitness increase associated with Wolbachia infection. In contrast, no fitness difference was observed in comparisons of single- and superinfected females. We discuss the observed results in regard to the evolution of the Wolbachia/A. albopictus symbiosis and the observed pattern of Wolbachia infection in natural populations.     

A decade of stability for wMel Wolbachia in natural Aedes aegypti populations

Mosquitoes carrying Wolbachia endosymbionts are being released in many countries for arbovirus control. The wMel strain of Wolbachia blocks Aedes-borne virus transmission and can spread throughout mosquito populations by inducing cytoplasmic incompatibility. Aedes aegypti mosquitoes carrying wMel were first released into the field in Cairns, Australia, over a decade ago, and with wider releases have resulted in the near elimination of local dengue transmission. The long-term stability of Wolbachia effects is critical for ongoing disease suppression, requiring tracking of phenotypic and genomic changes in Wolbachia infections following releases. We used a combination of field surveys, phenotypic assessments, and Wolbachia genome sequencing to show that wMel has remained stable in its effects for up to a decade in Australian Ae. aegypti populations. Phenotypic comparisons of wMel-infected and uninfected mosquitoes from near-field and long-term laboratory populations suggest limited changes in the effects of wMel on mosquito fitness. Treating mosquitoes with antibiotics used to cure the wMel infection had limited effects on fitness in the next generation, supporting the use of tetracycline for generating uninfected mosquitoes without off-target effects. wMel has a temporally stable within-host density and continues to induce complete cytoplasmic incompatibility. A comparison of wMel genomes from pre-release (2010) and nine years post-release (2020) populations show few genomic differences and little divergence between release locations, consistent with the lack of phenotypic changes. These results indicate that releases of Wolbachia-infected mosquitoes for population replacement are likely to be effective for many years, but ongoing monitoring remains important to track potential evolutionary changes.     

Relative Wolbachia density of field-collected Aedes albopictus mosquitoes in Thailand

Female Aedes albopictus mosquitoes from natural populations of different geographical regions of Thailand were collected and allowed to oviposit to determine relative Wolbachia A and Wolbachia B densities of their offspring (F1) by using real-time quantitative PCR (RTQ-PCR). An important aspect of this work is that all Aedes albopictus mosquitoes were collected from the field. Twenty-seven offspring were from diverse areas of Thailand (Songkhla, Konkaen, Chantaburi, and Kanchanaburi). The range of relative Wolbachia A density in F, mosquitoes was from 0.007 to 1250.78 (bacteria-to-host ratio), whereas relative Wolbachia B densities ranged from 0 to 348.2 (bacteria-to-host ratio). These data are in contrast to those from a previous study that showed a very low amount (less than 0.10) of both relative Wolbachia density types for laboratory strains. The percent transmission of Wolbachia density from mother to each individual offspring cannot be predicted and was not related to the sex of the F1. Obtaining confirmation for variations and unpredictable Wolbachia transmission load raises some concerns about using Wolbachia as a gene-driving system in nature for population replacement if Wolbachia density is involved in cytoplasmic incompatibility in this mosquito.     

A wMel Wolbachia variant in Aedes aegypti from field-collected Drosophila melanogaster with increased phenotypic stability under heat stress

Mosquito-borne diseases remain a major cause of morbidity and mortality. Population replacement strategies involving the wMel strain of Wolbachia are being used widely to control mosquito-borne diseases. However, these strategies may be influenced by temperature because wMel is vulnerable to heat. wMel infections in Drosophila melanogaster are genetically diverse, but few transinfections of wMel variants have been generated in Aedes aegypti. Here, we successfully transferred a wMel variant (termed wMelM) originating from a field-collected D. melanogaster into Ae. aegypti. The new wMelM variant (clade I) is genetically distinct from the original wMel transinfection (clade III), and there are no genomic differences between wMelM in its original and transinfected host. We compared wMelM with wMel in its effects on host fitness, temperature tolerance, Wolbachia density, vector competence, cytoplasmic incompatibility and maternal transmission under heat stress in a controlled background. wMelM showed a higher heat tolerance than wMel, likely due to higher overall densities within the mosquito. Both wMel variants had minimal host fitness costs, complete cytoplasmic incompatibility and maternal transmission, and dengue virus blocking under laboratory conditions. Our results highlight phenotypic differences between Wolbachia variants and wMelM shows potential as an alternative strain in areas with strong seasonal temperature fluctuations.     

Transovarial Transmission of Chikungunya Virus by Aedes albopictus Mosquitoes Ingesting Microfilariae of Dirofilaria immitis under Laboratory Conditions

Female Aedes albopictus mosquitoes of the Miki strain were experimentally fed on defibrinated sheep blood containing 5× 10⁷ PFU of chikungunya virus and 20,000 microfilariae of Dirofilaria immitis per milliliter. Fully engorged mosquitoes transmitted the virus to a small percentage of the F1 progeny, but females of the F1 generation did not transmit the virus to the F2 progeny. The control mosquitoes that ingested the virus without microfilariae did not transmit the virus to their eggs, larvae, or pupae in the F1 or F2 generations. These results showed that A. albopictus of this strain that concurrently ingested the virus and microfilariae transmitted the virus by the transovarial route under experimental conditions.     

Differential Susceptibilities of Aedes aegypti and Aedes albopictus from the Americas to Zika Virus

BackgroundSince the major outbreak in 2007 in the Yap Island, Zika virus (ZIKV) causing dengue-like syndromes has affected multiple islands of the South Pacific region. In May 2015, the virus was detected in Brazil and then spread through South and Central America. In December 2015, ZIKV was detected in French Guiana and Martinique. The aim of the study was to evaluate the vector competence of the mosquito spp. Aedes aegypti and Aedes albopictus from the Caribbean (Martinique, Guadeloupe), North America (southern United States), South America (Brazil, French Guiana) for the currently circulating Asian genotype of ZIKV isolated from a patient in April 2014 in New Caledonia.Conclusions/SignificanceThis study suggests that although susceptible to infection, Ae. aegypti and Ae. albopictus were unexpectedly low competent vectors for ZIKV. This may suggest that other factors such as the large naïve population for ZIKV and the high densities of human-biting mosquitoes contribute to the rapid spread of ZIKV during the current outbreak.     

Pathogenicity of Life-Shortening Wolbachia in Aedes albopictus after Transfer from Drosophila melanogaster

Maternally inherited Wolbachia bacteria have evolved mechanisms to manipulate the reproduction of their invertebrate hosts, promoting infection spread. A high fitness cost to the host is maladaptive for obligate endosymbionts, and prior studies show rapid selection of new Wolbachia associations toward commensal or mutualistic symbioses. Here, wMelPop Wolbachia is transferred from Drosophila melanogaster into the mosquito Aedes albopictus. Characterization of the resulting strain provides an extreme example of Wolbachia as a pathogen. In addition to reduced longevity and fecundity, abnormally high Wolbachia density is associated with embryonic mortality that masks the typical pattern of cytoplasmic incompatibility. The results are consistent with earlier reports that show unpredictable shifts in the Wolbachia phenotype after interspecific transfer, which can complicate proposed strategies to modify the age structure of medically important vector populations.Wolbachia bacteria have been identified within a diverse array of invertebrates, where infections are responsible for a variety of host effects including male killing, parthenogenesis, feminization and cytoplasmic incompatibility (CI) (29). The CI phenotype is characterized by early embryonic arrest and a reduction in the number of viable progeny (7, 8, 18, 39). Strict maternal inheritance via embryonic cytoplasm is observed with Wolbachia, and although Wolbachia numbers can be high in testes (24), transmission of the infection to offspring via males has not been reported (17, 41). Instead, an unidentified “modification” of sperm acts to initiate CI in fertilized embryos, unless “rescued” by a compatible Wolbachia infection in their mates (8). The cost of CI to hosts falls upon uninfected females and infected males within the host population, and since males are a dead-end for Wolbachia infection, the resulting dynamics can lead to the spread of infection above an unstable equilibrium threshold (18).Wolbachia bacteria are generally described as “reproductive parasites,” and Wolbachia-host interactions include examples that span the symbiosis spectrum. Field and laboratory studies support hypothesized trends from pathogenicity toward commensalisms and/or mutualism (16, 25, 40). Since mutualistic examples are hypothesized to represent older associations, it follows that maladapted symbioses will be more common among new associations, including artificially generated infections. It is surprising, therefore, that additional examples of pathogenic Wolbachia symbioses have not been identified to date, especially given examples of Wolbachia transinfection. To date, there are two reported examples of pathogenic Wolbachia: an artificially generated association between the isopod Porcellio dilatatus and Wolbachia injected from Armadillium (2) and the wMelPop Wolbachia infection in Drosophila (27). Both examples are similar in that host mortality occurs relatively late and is associated with Wolbachia overproliferation in adult tissues (22, 27). A prior artificial transfer of the wMelPop infection into D. simulans led to a transient exaggeration of pathogenic effects, which were ameliorated in later generations (24, 25).A recent report of the stable introduction of wMelPop into the medically important mosquito disease vector Aedes aegypti (26) suggests a potential strategy to control disease transmission utilizing the heritable Wolbachia infection. Since female mosquitoes must survive an extrinsic incubation period to transmit dengue or other pathogens, a Wolbachia-induced shift in the population age structure toward younger females is expected to reduce pathogen transmission (6, 9).Aedes albopictus (Asian tiger mosquito) is a globally invasive mosquito that has spread via accidental human transport and competitive dominance, resulting in its displacement of numerous resident mosquito populations (15, 30, 31). Its relevance as a disease vector has been elevated recently due to its role in recent chikungunya outbreaks (1, 14, 21, 36).Populations of A. albopictus are normally superinfected with two Wolbachia strains: wAlbA and wAlbB (23, 37). The infection is among the most mutualistic of associations described for Wolbachia in insects (12). Here, we introduced wMelPop into A. albopictus as the first step toward modifying age structure of an A. albopictus population in order to decrease disease transmission such as dengue. However, the wMelPop infection in A. albopictus was maladaptive and provided an extreme example of Wolbachia as a pathogen.     

High Efficiency of Temperate Aedes albopictus to Transmit Chikungunya and Dengue Viruses in the Southeast of France

Background

Since 2005, cases of chikungunya (CHIK) were caused by an unusual vector, Aedes albopictus. This mosquito, present in Europe since 1979, has gained importance since its involvement in the first CHIK outbreak in Italy in 2007. The species is capable of transmitting experimentally 26 arboviruses. However, the vectorial status of its temperate populations has remained little investigated. In 2010, autochthonous cases of CHIK and dengue (DEN) were reported in southeastern France. We evaluated the potential of a French population of Ae. albopictus in the transmission of both viruses.

Methodology and Principal Findings

We used two strains of each virus, CHIK and DEN: one strain was isolated from an imported case, and one from an autochthonous case. We used as controls Aedes aegypti from India and Martinique, the source of the imported cases of CHIK and DEN, respectively. We showed that Ae. albopictus from Cagnes-sur-Mer (AL-CSM) was as efficient as the typical tropical vector Ae. aegypti from India to experimentally transmit both CHIK strains isolated from patients in Fréjus, with around 35–67% of mosquitoes delivering up to 14 viral particles at day 3 post-infection (pi). The unexpected finding came from the high efficiency of AL-CSM to transmit both strains of DENV-1 isolated from patients in Nice. Almost 67% of Ae. albopictus AL-CSM which have ensured viral dissemination were able to transmit at day 9 pi when less than 21% of the typical DEN vector Ae. aegypti from Martinique could achieve transmission.

Conclusions/Significance

Temperate Ae. albopictus behaves differently compared to its counterpart from tropical regions, where recurrent epidemic outbreaks occur. Its potential responsibility for outbreaks in Europe should not be minimized.     

Chikungunya Virus and Aedes Mosquitoes: Saliva Is Infectious as soon as Two Days after Oral Infection

Background

Aedes aegypti and Aedes albopictus are potential vectors of chikungunya virus (CHIKV). The recent CHIKV outbreaks were caused by a new variant characterized by a mutation in the E1 glycoprotein gene (E1-226V) which has favored a better transmissibility by Ae. albopictus. As Ae. albopictus tends to replace Ae. aegypti in many regions, one question remained: is Ae. albopictus as efficient as Ae. aegypti to transmit the variant E1-226V of CHIKV?

Methodology and Findings

We infected orally both species with the variant E1-226V and estimated the infection, the viral dissemination, and the transmission rate by real time RT-PCR. Additionally, we used an in vitro assay to determine the amount of virus delivered by mosquitoes in their saliva. We found that Ae. aegypti as well as Ae. albopictus ensured a high replication of the virus which underwent an efficient dissemination as detectable in the salivary glands at day 2 post-infection (pi). Infectious CHIKV particles were delivered by salivary glands from day 2 with a maximum at day 6 pi for Ae. albopictus (10^3.3 PFU) and day 7 pi for Ae. aegypti (10^2.5 PFU).

Conclusions

Ae. albopictus is slightly more efficient than Ae. aegypti to transmit the variant E1-226V of CHIKV. These results will help to design an efficient vector control to limit transmission as soon as the first human cases are diagnosed.     

Mathematical studies on the sterile insect technique for the Chikungunya disease and Aedes albopictus

Chikungunya is an arthropod-borne disease caused by the Asian tiger mosquito, Aedes albopictus. It can be an important burden to public health and a great cause of morbidity and, sometimes, mortality. Understanding if and when disease control measures should be taken is key to curtail its spread. Dumont and Chiroleu (Math Biosc Eng 7(2):315-348, 2010) showed that the use of chemical control tools such as adulticide and larvicide, and mechanical control, which consists of reducing the breeding sites, would have been useful to control the explosive 2006 epidemic in Réunion Island. Despite this, chemical control tools cannot be of long-time use, because they can induce mosquito resistance, and are detrimental to the biodiversity. It is therefore necessary to develop and test new control tools that are more sustainable, with the same efficacy (if possible). Mathematical models of sterile insect technique (SIT) to prevent, reduce, eliminate or stop an epidemic of Chikungunya are formulated and analysed. In particular, we propose a new model that considers pulsed periodic releases, which leads to a hybrid dynamical system. This pulsed SIT model is coupled with the human population at different epidemiological states in order to assess its efficacy. Numerical simulations for the pulsed SIT, using an appropriate numerical scheme are provided. Analytical and numerical results indicate that pulsed SIT with small and frequent releases can be an alternative to chemical control tools, but only if it is used or applied early after the beginning of the epidemic or as a preventive tool.     

Induction of cell migration by transient Wolbachia pipientis infection in Aedes albopictus cell line

Wolbachia is a genus of maternally transmitted bacteria having an endosymbiotic relationship with arthropod and nematode species. These bacteria manipulate host development, sex-determination, and reproduction. In addition, they are known to potentially suppress vector-borne diseases by interfering with pathogen transmission. Although the occurrence of Wolbachia infection in insects has been known, the underlying mechanisms that mediate their interactions remain unclear. To examine the influence of Wolbachia adaptation on the host, we infected wAlbA and wAlbB strain from Aedes albopictus into the C6/36 cell line derived from Ae. albopictus. The transient Wolbachia infection was characterized by induction of cell migration without cell proliferation. The production of nitrite and reactive oxygen species (ROS) was induced by transient Wolbachia infection. Cells with transient Wolbachia infection exhibited elevated expression of Toll-like receptor 6 (TLR6) and myeloid differentiation primary response 88 (Myd88). Conversely, the expression of TLR2, TLR4, TLR7, Cactus, Ankyrin, and Argonaute2 (AGO2) was inhibited upon Wolbachia infection. These results suggest that Wolbachia has an influence on the cell migration ability as well as host innate immune response in vitro. Considering these results, transient Wolbachia strain transfer in C6/36 cells might be an important approach for studying Wolbachia-host interactions and might help gain a deeper understanding of the early adaptation of Wolbachia in the original host insect.     

High prevalence and lack of diversity of Wolbachia pipientis in Aedes albopictus populations from Northeast Brazil

The use of Wolbachia as a tool to control insect vectors has recently been suggested. In this context, studies on the prevalence and diversity of this bacterium in wild populations are relevant. Here, we evaluated the diversity of two Wolbachiagenes (ftsZ and wsp) and the prevalence of this endosymbiont in wild Aedes albopictus. Using semi-nested polymerase chain reaction, our results showed that 99.3% of the individuals were superinfected with Wolbachia. In regards to genetic diversity, the two genes showed no variation within or among mosquito populations. An analysis of other Wolbachia markers may help to clarify the relationship between insect and endosymbiont.     

Dissemination and Transmission of the E1-226V Variant of Chikungunya Virus in Aedes albopictus Are Controlled at the Midgut Barrier Level

Emergence of arboviruses could result from their ability to exploit new environments, for example a new host. This ability is facilitated by the high mutation rate occurring during viral genome replication. The last emergence of chikungunya in the Indian Ocean region corroborates this statement since a single viral mutation at the position 226 on the E1 glycoprotein (E1-A226V) was associated with enhanced transmission by the mosquito Aedes albopictus in regions where the major mosquito vector, Aedes aegypti, is absent.We used direct competition assays in vivo to dissect out the mechanisms underlying the selection of E1-226V by Ae. albopictus. When the original variant E1-226A and the newly emerged E1-226V were provided in the same blood-meal at equal titers to both species of mosquitoes, we found that the proportion of both variants was drastically different in the two mosquito species. Following ingestion of the infectious blood-meal, the E1-226V variant was preferentially selected in Ae. albopictus, whereas the E1-226A variant was sometimes favored in Ae. aegypti. Interestingly, when the two variants were introduced into the mosquitoes by intrathoracic inoculations, E1-226V was no longer favored for dissemination and transmission in Ae. albopictus, showing that the midgut barrier plays a key role in E1-226V selection.This study sheds light on the role of the midgut barrier in the selection of novel arbovirus emerging variants. We also bring new insight into how the pre-existing variant E1-226V was selected among other viral variants including E1-226A. Indeed the E1-226V variant present at low levels in natural viral populations could rapidly emerge after being selected in Ae. albopictus at the midgut barrier level.     

Impact of Wolbachia on Infection with Chikungunya and Yellow Fever Viruses in the Mosquito Vector Aedes aegypti

Incidence of disease due to dengue (DENV), chikungunya (CHIKV) and yellow fever (YFV) viruses is increasing in many parts of the world. The viruses are primarily transmitted by Aedes aegypti, a highly domesticated mosquito species that is notoriously difficult to control. When transinfected into Ae. aegypti, the intracellular bacterium Wolbachia has recently been shown to inhibit replication of DENVs, CHIKV, malaria parasites and filarial nematodes, providing a potentially powerful biocontrol strategy for human pathogens. Because the extent of pathogen reduction can be influenced by the strain of bacterium, we examined whether the wMel strain of Wolbachia influenced CHIKV and YFV infection in Ae. aegypti. Following exposure to viremic blood meals, CHIKV infection and dissemination rates were significantly reduced in mosquitoes with the wMel strain of Wolbachia compared to Wolbachia-uninfected controls. However, similar rates of infection and dissemination were observed in wMel infected and non-infected Ae. aegypti when intrathoracic inoculation was used to deliver virus. YFV infection, dissemination and replication were similar in wMel-infected and control mosquitoes following intrathoracic inoculations. In contrast, mosquitoes with the wMelPop strain of Wolbachia showed at least a 10⁴ times reduction in YFV RNA copies compared to controls. The extent of reduction in virus infection depended on Wolbachia strain, titer and strain of the virus, and mode of exposure. Although originally proposed for dengue biocontrol, our results indicate a Wolbachia-based strategy also holds considerable promise for YFV and CHIKV suppression.