Biology subjects

de Wit, S.

Publications and source records attributed to de Wit, S..

4 recordsLinked to original sources

bioRxiv2025

Feeding a low-protein diet exacerbates the susceptibility to Citrobacter rodentium and Dextran Sulfate Sodium-induced intestinal injury in mice.

Globally, almost half of all early childhood deaths are linked to severe undernutrition, herein referred to as severe malnutrition. Mortality in severely malnourished children is often attributed to common infectious diseases, including enteric infections. It has been proposed that impaired intestinal barrier function contributes to mortality, but direct evidence is limited and thus there exists a need to develop improved preclinical models to test these and other mechanistic hypotheses. In this study, we aimed to describe differences in response to enteric inflammation and infection in the colon of malnourished mice compared to well-nourished littermates. C57Bl/6 male weanlings were fed isocaloric diets, either a low 1% protein diet (LPD) or a control 18% protein diet (CPD) for 2-weeks either in combination with oral administration of dextran sodium sulfate (DSS), or Citrobacter rodentium (C. rodentium). LPD-fed mice were more susceptible to DSS or C. rodentium as evidenced by increased clinical severity scores, and reaching their humane endpoints. LPD-fed mice also showed more signs of colonic dysfunction with reduced levels of tight junction proteins, higher colonic pathogen load, and increased systemic inflammation and bacterial spread. Taken together, these observations show that malnourished animals have increased susceptibility to intestinal dysfunction caused by either chemical exposure or infection. These novel preclinical models can be used to further elucidate the processes involved in enteric dysfunction in malnutrition and to test therapies to improve intestinal repair and outcomes.

microbiology↗

bioRxiv2025

The cow udder is a potential mixing vessel for influenza A viruses

The incursion of high pathogenicity avian influenza A virus (IAV) into US dairy cows is unprecedented in the era of molecular diagnosis and pathogen sequencing. This raises questions over the likelihood of further outbreaks and whether dairy cattle could be a "mixing vessel" for novel strains of IAV. Using a panel of BSL2-safe reassortant viruses representing clade 2.3.4.4b H5 epizootic lineages circulating since 2020, we found that a cow B3.13 isolate displayed enhanced replication in cow mammary gland cells, along with increased viral polymerase activity and stronger interferon antagonism in cow cells compared to an earlier EA-2020-C genotype virus. However, multiple avian and mammalian IAV strains, including other clade 2.3.4.4b high pathogenicity genotypes, were replication competent in bovine cells, particularly those of the mammary gland, suggesting that there is a diverse circulating IAV pool with the potential to infect cows. Moreover, we show that cow mammary cells co-express -2,3 and -2,6 - linked sialic acids, and are susceptible to co-infection with human and avian IAVs. We conclude that the US cow influenza outbreak does not simply reflect a unique adaptation of the B3.13 genotype virus; rather, the bovine udder represents a permissive niche for IAV and a plausible site for reassortment, underscoring its potential role in generating novel influenza viruses with pandemic risk.

microbiology↗

bioRxiv2025

Synergy between HA cleavage site sequence and NA-mediated plasminogen recruitment as a virulence mechanism for low pathogenic avian influenza

An outbreak of H3N1 low pathogenic avian influenza virus (LPAIV) in Belgium in 2019 caused unexpected levels of mortality and morbidity in poultry. These viruses possess an NA polymorphism associated with plasminogen binding, as well as an unusual sequence around the HA cleavage site; accordingly, HA cleavage mediated by NA-driven plasminogen recruitment has been proposed to underly their systemic spread and pathogenicity. To test this, we established a reverse genetics system for A/chicken/Belgium/460/2019 and created single mutations in HA (K345R), and NA (S122N) that restored the viruses to normal consensus, as well as an HA/NA double mutant. Confirming previous work, trypsin-independent spread and HA cleavage of wild type Ck/Belgium was observed in the presence of fetal bovine serum containing plasminogen in vitro. Dose-dependent HA cleavage and trypsin-independent spread was also observed in the presence of purified chicken plasminogen. Compared to wild type virus, both HA cleavage and virus spread in vitro were reduced by the HA K345R mutation and further blocked by NA mutation S122N. Plasminogen-mediated HA cleavage was seen in a variety of avian cell lines and chicken organoids, excluding cell type-dependent effects. Furthermore, in ovo tests showed that mutant viruses unable to recruit plasminogen were less able to replicate systemically in chicken embryos. Bioinformatics analyses revealed other viruses which could potentially recruit plasminogen, including two independent outbreaks of H6N1 viruses, one of which we confirmed PLG-driven spread in vitro. We conclude that PLG-recruitment by NA is a general virulence mechanism of N1 LPAIVs Author summaryAvian influenza viruses (AIV) are divided into two broad categories - high or low pathogenicity - based on the sequence of their haemagglutinin (HA) and their lethality in chickens. The majority of AIV strains circulating in the wild are low pathogenicity both in waterfowl and when they spill over into domestic poultry. However, some low pathogenicity strains can cause severe disease in poultry despite not being classified as H5 or H7 high pathogenic AIVs with an HA polybasic protease cleavage site. A severe 2019 outbreak of an H3N1 strain has been suggested to result from the neuraminidase (NA) of the virus recruiting cellular plasminogen to proteolytically activate HA. Here, we tested this hypothesis by using reverse genetics to mutate the virus in a way predicted to block this. We found that indeed, the sequence of the NA at position 122 is the primary determinant of plasminogen-driven HA cleavage but that the unusual sequence at the HA cleavage site of the outbreak virus also contributes to pathogenicity. Furthermore, we show that N1 NA sequence can be used to identify other unexpectedly virulent strains of AIV. This work therefore adds to our ability to risk assess AIV strains from sequence-based surveillance.

microbiology↗

bioRxiv2022

Can the brain strategically go on automatic pilot? An fMRI study investigating the effect of if-then planning on behavioral flexibility

People often have good intentions but fail to adhere to them. Implementation intentions, a form of strategic planning, can help people to close this intention-behavior gap. Their effectiveness has been proposed to depend on the mental formation of a stimulus-response association between a trigger and target behavior, thereby creating an instant habit. If implementation intentions do indeed lead to reliance on habitual control, then this may come at the cost of reduced behavioral flexibility. Furthermore, we would expect a shift from recruitment of corticostriatal brain regions implicated in goal-directed control towards habit regions. To test these ideas, we performed a functional MRI study in which participants received instrumental training supported by either implementation or goal intentions, followed by an outcome-revaluation to test reliance on habitual versus goal-directed control. We found that implementation intentions led to increased efficiency during training, as reflected in higher accuracy, faster reaction times, and decreased engagement of the anterior caudate. However, implementation intentions did not reduce behavioral flexibility when goals changed during the test phase, nor did it affect the underlying corticostriatal pathways. Additionally, this study showed that slips of action towards devalued outcomes are associated with reduced activity in brain regions implicated in goal-directed control. In conclusion, our behavioral and neuroimaging findings suggest that strategic if-then planning does not lead to a shift from goal-directed towards habitual control.

neuroscience↗