Immune stability predicts tuberculosis infection risk in a wild mammal

Abstract

Immunity is one of the most variable phenotypic traits in animals; however, some individuals may show less fluctuation in immune traits, resulting in stable patterns of immune variation over time. It is currently unknown whether immune variation has consequences for infectious disease risk. In this study, we identified moderately stable immune traits in wild African buffalo and asked whether the stability of these traits affected bovine tuberculosis (TB) infection risk. We found that adaptive immune traits such as the level of interferon-γ (IFN-γ) released after white blood cell stimulation, the number of circulating lymphocytes and the level of antibodies against bovine adenovirus-3 were moderately repeatable (i.e. stable) over time, whereas parameters related to innate immunity either had low repeatability (circulating eosinophil numbers) or were not repeatable (e.g. neutrophil numbers, plasma bacteria killing capacity). Intriguingly, individuals with more repeatable IFN-γ and lymphocyte levels were at a significantly higher risk of acquiring TB infection. In stark contrast, average IFN-γ and lymphocyte levels were poor predictors of TB risk, indicating that immune variability rather than absolute response level better captured variation in disease susceptibility. This work highlights the important and under-appreciated role of immune variability as a predictor of infection risk.

Functionally distinct T-helper cell phenotypes predict resistance to different types of parasites in a wild mammal

“…One limitation of our study is its cross-sectional nature: longitudinal data is required to determine whether age-related variation is driven by within-individual change or selective effects and how such variation impacts on demography 64 . The small number of longitudinal studies measuring Th-related phenotypes in the wild suggest they are weakly to moderately repeatable within individuals 29,31,65 . Indeed, higher repeatability of IFN-γ in wild buffalo has been shown to predict higher risk of bTB infection, suggesting that the variation on adaptive immune responses could benefit the host by protecting it from infection 65 .…”

“…The small number of longitudinal studies measuring Th-related phenotypes in the wild suggest they are weakly to moderately repeatable within individuals 29,31,65 . Indeed, higher repeatability of IFN-γ in wild buffalo has been shown to predict higher risk of bTB infection, suggesting that the variation on adaptive immune responses could benefit the host by protecting it from infection 65 . Further studies examining longitudinal changes across functional Th subsets and relating these to parasite pressure and demographic rates are likely to illuminate the causes and consequences of variation in Th function for natural populations.…”

Adverse effects of Diptera flies on northern ungulates: Rangifer, Alces, and Bison

“…In sheep, subsequent declines in density and exposure do not favour selection for these costly attributes, because individuals have a good likelihood of surviving and reproducing without the costly trait (Hayward et al 2014). The specific ability to switch a response on and off may be a better indicator of resistance to parasites than the extent to which the immune system can mount a general response (Seguel et al 2019). The major histocompatibility complex (MHC) is a large library of genes that code for antigens.…”