Van De Wiele, C. | Search bioRxiv

bioRxiv2023

Belgian Culex pipiens pipiens are competent vectors for West Nile virus but not Usutu virus

BackgroundWest Nile virus (WNV) and Usutu virus (USUV) are emerging arboviruses in Europe transmitted by Culex mosquitoes. In Belgium, it is currently unknown which Culex species are competent vectors for WNV or USUV and if these mosquitoes carry Wolbachia, an endosymbiotic bacterium that can block arbovirus transmission. The aims of our study were to measure the vector competence of Belgian Culex mosquitoes to WNV and USUV and determine if a naturally acquired Wolbachia infection can influence virus transmission. Methodology/Principal FindingsWe captured 876 non-engorged female Culex mosquitoes from urban and peri-urban sites in Leuven, Belgium. We provided females with an infectious bloodmeal containing WNV lineage 2, USUV European (EU) lineage 3, or USUV African (AF) lineage 3. Blood-fed females (n=154) were incubated for 14 days at 25{degrees}C after which the body, head, and saliva were collected to measure infection (IR), dissemination (DR), and transmission (TR) rates, respectively. Mosquito species were identified by qRT-PCR or Sanger sequencing, the presence of infectious virus in mosquitoes was confirmed by plaque assays, and viral genome copies were quantified by qRT-PCR. We found that Culex pipiens pipiens were able to transmit WNV (11% IR, 40% DR, 100% TR) but not USUV (EU lineage: 13% IR, 0% DR; AF lineage: 16% IR, 17% DR, 0% TR). In contrast, Culex modestus was able to transmit USUV (AF lineage: 60% IR, 67% DR, 50% TR), but not WNV (0% IR). We found that the presence or absence of Wolbachia was species-dependent and did not associate with virus transmission. Conclusions/SignificanceThis is the first report that Belgian Culex mosquitoes can transmit both WNV and USUV, forewarning the risk of human transmission. More research is needed to understand the potential influence of Wolbachia on arbovirus transmission in Culex modestus mosquitoes. Author SummaryWest Nile virus and Usutu virus can cause seasonal epidemics in humans. They are maintained in a transmission cycle between wild birds and Culex mosquitoes, and humans that are bitten by infected mosquitoes can develop life-threatening neurological disease. Certain Culex species carry the symbiotic bacterium Wolbachia which can block virus transmission in mosquitoes. In Belgium, it is currently unknown which Culex species can transmit West Nile virus and/or Usutu virus, or if they carry Wolbachia bacteria. In our study, we captured wild mosquitoes from Belgium and infected them with West Nile virus or Usutu virus. We found that a common European species (Culex pipiens pipiens, the Northern House mosquito) could transmit West Nile virus, whereas a lesser known species (Culex modestus) could transmit Usutu virus. Wolbachia bacteria could be found in almost all Culex pipiens pipiens, but not in Culex modestus, suggesting that Wolbachia prevalence is species-specific. More research is needed to understand if Wolbachia can block virus transmission in Culex modestus. This is the first report on the ability of Culex mosquitoes to transmit West Nile virus and Usutu virus in Belgium, forewarning the risk of transmission to humans.

microbiology↗

bioRxiv2020

The quorum sensing peptide EntF* promotes colorectal cancer metastasis in mice: a new factor in the microbiome-host interaction.

BackgroundColorectal cancer, one of the most common malignancies worldwide, is associated with a high mortality rate, mainly caused by metastasis. Comparative metagenome-wide analyses between healthy individuals and cancer patients suggest a role for the human intestinal microbiota. Nevertheless, which microbial molecules are involved in this communication is largely unknown, with current studies mainly focusing on short chain fatty acids and amino acid metabolites as potential mediators. However, quorum sensing peptides are not yet considered in this microbiome-host interaction: their in vivo presence nor any in vivo host-effect have been reported. ResultsFor the first time, we showed that a quorum sensing peptide metabolite, EntF* produced by intestinal microbiota (E. faecium), is present in the blood circulation of mice. Moreover, it significantly promotes colorectal cancer metastasis in vivo, with metastatic lesions found in both liver and lung tissues, using an orthotopic mice model evaluating bioluminescence as well as macroscopic and microscopic presence of metastatic tumour nodules. In vitro tests on E-cadherin expression levels thereby indicated that the first, second, sixth and tenth amino acid of EntF* were critical for the epithelial-mesenchymal transition (EMT) effect, responsible for tumour metastasis. ConclusionThis paper adds a new group of molecules, the quorum sensing peptides, as an additional causative factor explaining the microbiome-host interaction. The presence of a selected quorum sensing peptide (metabolite) in the mouse was proven for the first time and its in vivo effect on colorectal metastasis was demonstrated. We anticipate our in vivo results to be a starting point for broader microbiome-health investigations, not only limited to colorectal cancer metastasis, but also for developing novel bio-therapeutics in other disease areas, giving due attention to the QSP produced by the microbiome.

molecular biology↗