Pro- and anti-inflammatory cytokine expression in wild Akodon azarae: individual variability due to host factors, seasonality and parasite infections

Abstract

The variability of intrinsic and extrinsic factors to which wild populations are exposed may have consequences for the immune response, and hence, the host’s susceptibility to parasite infection may be affected. The present study aimed at evaluating the relationship between markers of anti- and pro-inflammatory immune responses and individual characteristics (age, sex, body condition), parasite parameters and seasonality in the mouse Akodon azarae (Cricetidae: Sigmodontinae). Expression levels of anti-inflammatory (IL-10 and TGF-β) and pro-inflammatory (TNF-α) cytokines in wild rodents were determined using real-time reverse transcription-polymerase chain reaction. The associations of each anti-inflammatory cytokine with endo- and ectoparasites depended on individual variables and seasonality. TGF-β was associated with endoparasites and body condition, while IL-10 was associated with ectoparasites. TNF-α showed a positive association with ectoparasites, which tended to be reversed when endoparasite abundance was high. In addition, levels of this cytokine tended to decrease with ectoparasite richness in autumn. Overall, we found that the association between ectoparasites and pro-inflammatory markers depended on season and endoparasite abundance, while its association with anti-inflammatory responses depended on both age and season. For each cytokine evaluated, there may be different factors that influence the results of mice-parasite interaction, such as co-infections, seasonality and host factors (e.g., age, sex, body condition). The information generated by this study is relevant to better understand infection dynamics and host-parasite interactions in wild rodents of this group.