Biology subjects

Verwimp, S.

Publications and source records attributed to Verwimp, S..

8 recordsLinked to original sources

bioRxiv2026

Genomic Potential vs. Pathogenic Reality: Functional Virulence Variation in Pseudomonas aeruginosa

Despite the rapid expansion of bacterial genome sequencing, predicting pathogen virulence from genomic information remains a major challenge. To study this association, we integrate comparative genomics, functional phenotyping, host-pathogen interaction assays, and infection outcomes across a diverse collection of 28 Pseudomonas aeruginosa isolates, representing clinically relevant diversity in serotype, type IV pilus group, and flagellar type. While virulence-associated systems were broadly retained across the strain collection, isolates displayed substantial variation in phenotypic behavior and pathogenicity. Genotypic classifications based on pilus, flagellar, siderophore, or secretion system characteristics were poor predictors of virulence-associated phenotypes. Pathogenicity in a Galleria mellonella model varied markedly among strains and was most strongly associated with surface-associated motility, whereas other virulence traits and quorum-sensing genotypes showed limited predictive value. In a three-dimensional lung epithelial cell model, inflammatory responses were negatively correlated with activity of the type III secretion system effector ExoS, suggesting a role in modulation of host immune signaling. Together, these findings demonstrate that virulence emerges from functional deployment of conserved virulence repertoires, rather than their mere presence. By linking genomic diversity to phenotypic expression, pathogenicity, and host responses within a single strain collection, this study highlights fundamental limitations of gene-content-based virulence prediction and underscores the importance of integrating genomic and functional data to better understand P. aeruginosa virulence.

microbiology↗

bioRxiv2026

The Heat shock protein 70 machinery is crucial in the production of infectious chikungunya virus progeny

Over the past decades, chikungunya virus (CHIKV), a re-emerging arthropod-borne alphavirus, has caused outbreaks in many (sub)tropical regions, but also in more temperate regions of the world, including Europe. CHIKV poses a significant health burden due to high infection rates during epidemics, symptom progression into chronic arthritic manifestations, and the lack of specific antiviral treatments. Multiple studies have shown that several viruses rely on host molecular chaperones, particularly the central Heat shock protein 70 (Hsp70), for replication. Hsp70s are guided by co-chaperones that drive their functionality and specificity. Here, we used chemical inhibitors of Hsp70-co-chaperone interactions to study the role of this molecular chaperone machinery in CHIKV replication. Our findings revealed that Hsp70 inhibition significantly reduces the CHIKV infectious particle production without affecting host-cell viability. Inhibition of the Hsp70-co-chaperone interaction primarily impedes the post-RNA replication stages of the CHIKV infectious cycle, affecting viral protein expression and reducing both the number and infectivity of released virions. Moreover, Hsp70 inhibition displayed antiviral activity in skin explants. Together, these results suggest that targeting the Hsp70 network could be a viable antiviral strategy against CHIKV infections. Author summaryAs obligatory intracellular parasites, viruses rely entirely on the machinery of the host cell to produce new viral particles. In our study, we investigated whether a specific group of host proteins, known as molecular chaperones, is important for the replication of chikungunya virus (CHIKV), a reemerging mosquito-borne virus that can cause long-lasting joint pains and lacks specific antiviral treatments. We focused on one key family of molecular chaperones, called Heat shock protein 70s (Hsp70s), which supports protein folding and quality control in cells. We used chemical compounds to block Hsp70 function and observed that CHIKV replication was strongly reduced, while host cells remained healthy. We found that Hsp70 is especially important in the later stages of the virus life cycle, where it helps produce viral proteins and new infectious virus particles. When Hsp70 was blocked, fewer and less infectious virus particles were produced. We also showed that this effect holds true in biopsies of mouse skin tissue, which mimics the initial site of infection. These findings identify Hsp70 as an important host factor for CHIKV that may serve as a potential target for new antiviral therapies.

microbiology↗

bioRxiv2025

Low risk of transmission of prototype and newly emerged Oropouche virus strains by European Culex pipiens, Aedes albopictus, and Anopheles atroparvus mosquitoes

Oropouche virus (OROV) is an emerging arbovirus of growing public health concern, with increasing incidence and geographic spread. Since its discovery in 1955, OROV has caused multiple outbreaks in South and Central America, with a new introduction in Cuba since May 2024. Recent travel-related cases in Europe and the Americas underscore its potential for global dissemination. Assessing vector competence outside endemic regions is critical in the context of global travel and climate change. We evaluated the vector competence of three mosquito species commonly found in Europe--Culex (Cx.) pipiens, Aedes (Ae.) albopictus, and Anopheles (An.) atroparvus--using two OROV strains: the prototype TRVL9760 (1955, Trinidad and Tobago) and a recent isolate OROV-IRCCS-SCDC_1/2024 (2024, imported from Cuba to Italy). Mosquitoes were orally infected and examined at 7- and 14-days post-infection. We assessed infection (body), dissemination (peripheral tissues), and transmission potential (saliva) by measuring infectious virus particles using the gold standard focus-forming assays. Our findings show that Cx. pipiens and An. atroparvus were not susceptible to infection or did not allow transmission with OROV. In Ae. albopictus, low infection rates were observed: 6.7% of mosquitoes showed infection at day 7 with the prototype strain, and 3.1% at day 14 with OROV-IRCCS-SCDC_1/2024. All infected mosquitoes showed viral dissemination, but none had infectious virus in their saliva, indicating low risk for transmission. These results confirm limited vector competence of European mosquito species for OROV and emphasize the importance of continued entomological surveillance to inform future risk assessments.

microbiology↗

bioRxiv2025

Combinations of approved oral nucleoside analogues confer potent suppression of alphaviruses in vitro and in vivo

BackgroundAlphaviruses, including chikungunya virus (CHIKV), pose a significant global health threat, yet specific antiviral therapies remain unavailable. MethodsWe evaluated combinations of three oral directly acting antiviral drugs (sofosbuvir (SOF), molnupiravir (MPV), and favipiravir (FAV)), which are approved for other indications, against CHIKV, Semliki Forest virus (SFV), Sindbis virus (SINV), and Venezuelan Equine Encephalitis virus (VEEV) in vitro and in vivo. We assessed antiviral efficacy in human skin fibroblasts and liver cells, as well as in a mouse model of CHIKV-induced arthritis. FindingsIn human skin fibroblasts, synergistic antiviral effects were observed for combinations of MPV + SOF and FAV + SOF against CHIKV, and for FAV + SOF against SFV. In human liver cells, FAV + MPV conferred additive to synergistic activity against VEEV and SINV, while SOF synergized with FAV against SINV. In mice, MPV improved CHIKV-induced foot swelling and reduced systemic infectious virus titres. Combination treatment with MPV and SOF significantly reduced swelling and infectious virus titres compared to monotherapies of each drug. Sequencing of CHIKV RNA from joint tissue revealed that MPV caused dose- dependent increases in mutations in the CHIKV genome. Upon combination therapy of MPV with SOF, the number of mutations was significantly lower compared to monotherapy with several higher doses of MPV. InterpretationCombining these approved oral nucleoside analogues confers potent suppression of multiple alphaviruses in vitro and in vivo with enhanced control of viral genetic evolution in face of antiviral pressure. These drug combinations may ultimately lead to the development of potent combinations of pan-family alphavirus inhibitors. FundingThis work was supported by a PhD fellowship granted to S.V. by the Research Foundation - Flanders (FWO) (11D5923N). L.D.C. was also supported by Research Foundation - Flanders (FWO) PhD fellowship (11L1325N). Dr. Polyak and Schiffer are partially supported by R01AI121129. Research in ContextO_ST_ABSEvidence before this studyC_ST_ABSAlphaviruses such as chikungunya virus (CHIKV), Sindbis virus (SINV), and Venezuelan Equine Encephalitis virus (VEEV) are a major threat for global health. Alphaviruses are responsible for debilitating diseases with major public health implications, yet no antiviral drugs are currently approved for treating these virus infections. Existing treatment options are limited to supportive care and are unlikely to provide protection against future outbreaks of other alphaviruses. Previous studies have shown that oral approved nucleoside analogues such as favipiravir (FAV), molnupiravir (MPV), and sofosbuvir (SOF) have antiviral activity against certain RNA viruses, including alphaviruses. However, systematic in vivo evaluations of these drugs and testing of drug combinations in both in vitro and in vivo settings are limited. Added value of this studyThis study provides a comprehensive evaluation of combinations of FAV, MPV and SOF against multiple alphaviruses in two human cell lines and a CHIKV mouse model. We demonstrate that certain combinations of these drugs confer synergistic antiviral activity, effectively suppressing CHIKV, SFV, SINV, and VEEV replication in vitro. Moreover, in vivo, we show for the first time that MPV treatment results in reduced CHIKV-induced foot swelling and systemic virus replication. Combining MPV with SOF enhances antiviral activity in mice as compared to monotherapy. By sequencing the viral genome, we show that MPV increases the number of mutations in a dose-dependent manner. Combination therapy of MPV and SOF reduces the number of mutations compared to higher doses of MPV. These findings highlight the potential of nucleoside analogue combinations as a promising therapeutic strategy against alphavirus infections. Implications of all the available evidenceThe results of this study suggest that combination therapy with approved nucleoside analogues could provide an effective treatment strategy for alphavirus infections. The observed increased efficacy of drug combinations supports the potential for dose optimization to enhance efficacy while reducing toxicity and development of resistance. Future research should focus on clinical evaluation of these drug combinations, pharmacokinetic studies, and further exploration of their impact on viral evolution. Given the expanding geographical distribution of alphaviruses and the lack of available treatments, these findings provide a foundation for developing pan-alphavirus antiviral therapies that could improve patient outcomes and global outbreak preparedness.

microbiology↗

bioRxiv2024

Depletion of skin bacteria by topical antibiotic treatment accelerates onset of Zika virus disease in mice.

Mosquito-borne flaviviruses have emerged as global health threats due to their rapid spread and high disease burden. The initial site of virus replication is the mosquito biting site in the host skin, yet the role of host skin bacteria remains unclear. Here, we observed accelerated progression of Zika virus (ZIKV)-induced disease in mice with depleted skin bacteria by topical antibiotic treatment prior to ZIKV infection. Increased viral loads in the blood, draining lymph node, spleen and brain of antibiotic-treated mice suggested faster ZIKV dissemination. Flow cytometry revealed increased frequencies of T cells in the lymph nodes, along with enhanced activation of T cells in the brain upon antibiotic treatment. The antibiotic-induced phenotype was rescued by restoring the skin bacteria prior to infection. Our findings demonstrate an increased susceptibility to ZIKV infection in mice with depleted skin microbiomes, suggesting a potential role of skin bacteria in modulating the infection outcome.

microbiology↗

bioRxiv2023

Identification of culturable fungi and bacteria in mosquito saliva and impact on arbovirus infection in vitro

Mosquito saliva plays a key role in arbovirus transmission and pathogenesis. This study isolated and identified culturable fungal and bacterial colonies from saliva harvested from Aedes aegypti (lab strain) and Culex pipiens (field-collected) mosquitoes. For the first time, Penicillium crustosum was identified in mosquito saliva. Culturable bacteria detected in mosquito saliva included Serratia marcescens, Serratia nematodiphila, Enterobacter spp., and Klebsiella spp., which were previously identified as mosquito or insect endosymbionts in the midgut or other organs. Analysis with 16S metagenomics showed that the bacterial community in saliva appeared more diverse than the bacterial communities in midguts. Blood feeding did not affect the fungal or bacterial load in mosquito saliva. Oral treatment of adult mosquitoes with antibiotics or an antifungal drug resulted in a significant reduction of resp. bacteria or fungi present in the mosquito saliva. Co-incubation of Semliki Forest virus with saliva from antibiotic or antifungal treated mosquitoes triggered a decrease in viral infection in human skin fibroblasts compared to non-treated saliva. This work lays the foundation for further exploration of the impact of fungi and bacteria in mosquito saliva on both vector competence and arbovirus infection in the mammalian host.

microbiology↗

bioRxiv2022

First report of kdr L1014F and ace-1 G119S insecticide resistance in Belgian Culex mosquitoes

The emergence of West Nile virus and Usutu virus in Europe poses a significant risk to public health. In the absence of efficient antiviral therapy or vaccine candidates, the only strategy to control these arboviruses is to target the Culex (Diptera: Culicidae) mosquito vector. However, the selection pressure caused by exposure to insecticides for vector control or agricultural pest control can lead to insecticide resistance, thereby reducing the efficacy of insecticide-based vector control interventions. In Culex mosquitoes, two of the most common amino acid substitutions associated with insecticide resistance are the kdr L1014F in voltage gated sodium channels and G119S in acetylcholinesterase. In this study, Culex pipiens biotype pipiens, Culex torrentium, and Culex modestus were sampled from 2019 to 2021 in three distinct environmental habitats (urban, peri-urban, and agricultural) in and around the city of Leuven, Belgium. Individual mosquitoes were screened for two mutations resulting in L1014F and G119S amino acid substitutions. Both mutations were observed in Culex pipiens and Culex modestus but not in Culex torrentium mosquitoes across the four collection sites. Furthermore, multi-resistance or cross-resistance in Culex pipiens could be a threat in these areas, as both mutations were observed at low frequencies. These results provide the first report of kdr L1014F and ace-1 G119S resistance in Culex pipiens and Culex modestus mosquitoes from Belgium, highlighting the importance of mosquito surveillance to design effective arbovirus outbreak control strategies.

molecular biology↗

bioRxiv2021

Alphavirus and flavivirus infectivity is disrupted by components of the bacterial cell wall

The impact of the host microbiota on arbovirus infections is currently not well understood. Arboviruses are viruses transmitted through the bites of infected arthropods, predominantly mosquitoes or ticks. The first site of arbovirus inoculation is the biting site in the host skin, which is colonized by a complex microbial community that could possibly influence arbovirus infection. We demonstrated that pre-incubation of arboviruses with certain components of the bacterial cell wall, including lipopolysaccharides (LPS) of some Gram-negative bacteria and lipoteichoic acids or peptidoglycan of certain Gram-positive bacteria, significantly reduced arbovirus infectivity in vitro. This inhibitory effect was observed for arboviruses of different virus families, including chikungunya virus of the Alphavirus genus and Zika virus of the Flavivirus genus, showing that this is a broad phenomenon. A modest inhibitory effect was observed following incubation with a panel of heat-inactivated bacteria, including bacteria residing on the skin. No viral inhibition was observed after pre-incubation of cells with LPS. Furthermore, a virucidal effect of LPS on viral particles was noticed by electron microscopy. Therefore, the main inhibitory mechanism seems to be due to a direct effect on the virus particles. Together, these results suggest that bacteria are able to decrease the infectivity of alphaviruses and flaviviruses. ImportanceDuring the past decades the world has experienced a vast increase in epidemics of alphavirus and flavivirus infections. These viruses can cause severe diseases such as hemorrhagic fever, encephalitis and arthritis. Several alpha- and flaviviruses, such as chikungunya virus, Zika virus and dengue virus, are significant global health threats because of their high disease burden, their widespread (re-)emergence and the lack of (good) anti-arboviral strategies. Despite the clear health burden, alphavirus and flavivirus infection and disease are not fully understood. A knowledge gap in the interplay between the host and the arbovirus is the potential interaction with host skin bacteria. Therefore, we studied the effect of (skin) bacteria and bacterial cell wall components on alphavirus and flavivirus infectivity in cell culture. Our results show that certain bacterial cell wall components markedly reduced viral infectivity by directly interacting with the virus particle.

microbiology↗