Biology subjects

Shit, B.

Publications and source records attributed to Shit, B..

8 recordsLinked to original sources

bioRxiv2025

DIET IMPACTS THE EFFECTS OF THERMAL STRESS ON INFECTION OUTCOMES

BackgroundClimate change can lead to warmer environments, facilitating higher pathogen growth and increasing disease burden. Climate change can also reduce the nutritional value of food resources, causing malnutrition, which can lead to impaired immunity and disease vulnerability. However, despite these associations, no experiments have tested how dietary manipulations and temperature variations interact to drive the effects of pathogenic infections. In this work, we conducted laboratory experiments with the model insect Drosophila melanogaster to test these effects. ResultsVirgin flies raised on low-carbohydrate diets exhibited improved post-infection survival rates and more resilience to pathogen burden compared to those reared on standard or high-carbohydrate diets. However, such a survival advantage of the low-carbohydrate diet was lost in mated individuals. Notably, temperature stress decreased survival rates in flies only when they were reared on a standard diet. This effect was not observed in flies raised on high- or low-carbohydrate diets, indicating that the impact of temperature on infection responses might depend on diet. Besides, flies developing on a low-carbohydrate diet showed greater fertility at ambient temperatures than those on other diets, indicating an apparent lack of fitness costs associated with improved post-infection response. Also, high-carbohydrate diets conferred greater resistance to starvation, suggesting differences in resource allocation among somatic maintenance tasks that could increase vulnerability to pathogens. ConclusionOverall, these findings imply a complex interaction between diet, temperature, and fitness traits that influences variation in infection responses. As many organisms around the world face environmental warming and poor diets, examining these patterns and processes can provide a deeper understanding of variations in health and disease responses amid a changing climate.

ecology↗

bioRxiv2024

Evolutionary history with chronic malnutrition enhances pathogen susceptibility at older ages

Juvenile malnutrition is a global public health concern that negatively impacts the development and maturation of the immune system, leading to increased susceptibility to infectious diseases. Such adverse effects on immunity might increase with ageing, worsening disease conditions later in life. Furthermore, malnutrition may persist across generations, imposing strong natural selection to survive the nutrient shortage. However, it is unclear how the evolutionary history of ancestral generations with chronic malnutrition could influence pathogen resistance and infection susceptibility, as well as their age-specific changes in extant generations. To address this, we used Drosophila melanogaster populations adapted against chronic juvenile malnutrition and exposed them to a bacterial pathogen, Providencia rettgeri, during their early and late adulthood. Surprisingly, we observed that in populations adapted to chronic malnutrition, young flies survived infection better by tolerating the infection, while control flies displayed higher infection susceptibility despite carrying a similar pathogen load. However, this pattern in post-infection survival is reversed with ageing. There was no change in pathogen resistance, but evolved flies succumbed more to infection than control flies regardless of the input infection doses. Our study thus revealed new evolutionary insights into the development of contrasting early vs late-life immune strategies and age-specific vulnerabilities to infection as a function of early-life malnutrition.

evolutionary biology↗

bioRxiv2023

The immune regulation and epidemiological consequences of immune priming in Drosophila

Invertebrates lack the immune machinery underlying vertebrate-like acquired immunity. However, in many insects past infection by the same pathogen can prime the immune response, resulting in improved survival upon reinfection. Here, we investigated the generality, specificity and mechanistic basis of innate immune priming in the fruit fly Drosophila melanogaster when infected with the gram-negative bacterial pathogen Providencia rettgeri. We find that priming in response to P. rettgeri infection is a long-lasting and pathogen-specific response. We further explore the epidemiological consequences of immune priming and find it has the potential to curtail pathogen transmission by reducing pathogen shedding and spread. The enhanced survival of individuals previously exposed to a non-lethal bacterial inoculum coincided with a transient decrease in bacterial loads, and we provide strong evidence that the effect of priming requires the IMD-responsive antimicrobial-peptide Diptericin-B in the fat body. Further, we show that while Diptericin B is the main effector of bacterial clearance, it is not sufficient for immune priming, which requires regulation of IMD by peptidoglycan recognition proteins. This work underscores the plasticity and complexity of invertebrate responses to infection, providing novel experimental evidence for the effects of innate immune priming on population-level epidemiological outcomes.

immunology↗

bioRxiv2022

Correlated responses to experimental evolution of increased post-infection survival in Drosophila melanogaster: Life-history trade-offs and reaction to novel stressors

Evolution of increased immune defence is often limited by costs: correlated changes in other traits (viz. life-history traits) that otherwise reduce the fitness of the host organisms. Experimental evolution studies are useful for understanding the evolution of immune function, and correlated changes in other traits. We experimentally evolved replicate Drosophila melanogaster populations to better survive infection challenge with an entomopathogenic bacteria, Enterococcus faecalis. Within 35 generations of forward selection, selected populations showed marked increase in post-infection survival compared to ancestrally paired controls. We next measured various life-history traits of these populations. Our results show that the selected populations do not differ from control populations for larval development time and body weight at eclosion. No difference is also observed in case of fecundity and longevity (following the acute phase of infection), either when the flies are subjected to infection or when the flies were uninfected; although infected flies from all populations die much earlier compared to uninfected flies. Selected flies and control flies are also equally good at surviving abiotic stressors (starvation and desiccation), although infected flies from all populations are more susceptible to stress than uninfected flies. Therefore, we conclude that (a) D. melanogaster populations can rapidly evolve to be more immune to infection with E. faecalis; (b) evolution of increased defence against E. faecalis entails no life-history cost for the hosts; and (c) evolving defence against a biotic threat (pathogen) does not make flies more resistant to abiotic stressors.

evolutionary biology↗

bioRxiv2022

Ageing leads to nonspecific antimicrobial peptide responses in Drosophila melanogaster

Evolutionary theory predicts a late-life decline in the force of natural selection, possibly leading to late-life deregulations of the immune system. A potential outcome of such immune-deregulation is the inability to produce specific immunity against target pathogens. We tested this possibility by infecting multiple Drosophila melanogaster lines (with bacterial pathogens) across age-groups, where either individual or different combinations of Imd- and Toll-inducible antimicrobial peptides (AMPs) were deleted using CRISPR gene editing. We show a high degree of non-redundancy and pathogen-specificity of AMPs in young flies: in some cases, even a single AMP could confer complete resistance. In contrast, ageing led to a complete loss of such specificity, warranting the action of multiple AMPs across Imd- and Toll-pathways during infections. Moreover, use of diverse AMPs either had no survival benefits, or even accompanied survival costs post-infection. These features were also sexually dimorphic: females expressed a larger repertoire of AMPs than males, but extracted equivalent survival benefits. Finally, age-specific expansion of the AMP-pool was associated with downregulation of negative-regulators of the Imd-pathway and a potential damage to renal function, as features of poorly-regulated immunity, Overall, we could establish ageing as an important driver of nonspecific AMP responses, across sexes and bacterial infections.

immunology↗

bioRxiv2022

Effect of larval diet on adult immune function is contingent upon selection history and host sex in Drosophila melanogaster

Mounting an immune response requires a considerable energy investment by the host. This makes expression of immune phenotypes susceptible to changes in availability of resources. There is ample evidence in scientific literature to suggest that hosts become more vulnerable to infection by pathogens and parasites when access to nutrition is limited. Using populations of Drosophila melanogaster experimentally evolved to better survive bacterial infections, we explore if host selection history influences host response to resource deprivation in terms of immune function. We find that when reared on a suboptimal diet (both in larval and adult stages), adult flies from evolved populations are still more immune to infections compared to flies from control populations. Furthermore, we observe a sex-dependent effect of interaction between selection history and diet on immune function. We thus conclude that immune function of hosts adapted to pathogen challenge is less affected by resource limitation compared to non-adapted hosts.

evolutionary biology↗

bioRxiv2021

Recurrent evolution of cross-resistance in response to selection for improved post-infection survival in Drosophila melanogaster

The host susceptibility to one pathogen can decrease, increase, or remain unaffected by virtue of the host evolving resistance towards a second pathogen. Negative correlations between a host susceptibility to different pathogens is an often-cited explanation for maintenance of genetic variation in immune function determining traits in a host population. In this study, we investigated the change in susceptibility of Drosophila melanogaster flies to various novel bacterial pathogens after being experimentally selected for increased resistance to one particular bacterial pathogen. We independently selected flies to become more resistant towards Enterococcus faecalis and Pseudomonas entomophila, and baring a few exceptions the evolved populations exhibited cross-resistance against the range of pathogens tested in the study. Neither the identity of the native pathogen nor the host sex was major determining factors in predicting the pattern of cross-resistance exhibited by the selected populations. We therefore report that a generalized cross-resistance to novel pathogens can repeatedly evolve in response to selection for resistance against a single pathogen.

evolutionary biology↗

bioRxiv2019

Mating enhances immune function of Drosophila melanogaster populations against bacterial pathogens

Immunity and reproduction are two important processes that affect fitness of an organisms. Sexual activity has been previously shown to determine the degree to which a population is able to survive various infections. While many studies have demonstrated a trade-off between immune function and reproduction, many studies have found synergistic relation between the two fitness determinants. Besides it is generally hypothesised that sexes may differ in immunity due to relative cost they incur during reproduction with males losing in immunity to rather increase their reproductive success. In this study, we test the effect of immune function on the survival of mated and virgin replicates of a large outbred baseline D. melanogaster population that was infected with four different bacterial infections. We find enhanced survival in mated flies than virgin flies in response to all four bacterial infections across all replicates. While investigating sexual dimorphism in immune function, we find no difference in sexes in their ability to survive the imposed bacterial infections. Synergistic interaction between reproduction and immunity may exist if it improves Darwinian fitness of either sexes of a population under selection, and are not necessarily limited by each other due to trade-off over finite resources.

evolutionary biology↗