A longitudinal molecular study of the ecology of malaria infections in free-ranging mandrills

The Genome of Plasmodium gonderi: Insights into the Evolution of Human Malaria Parasites

Plasmodium species causing malaria in humans are not monophyletic, sharing common ancestors with nonhuman primate parasites. Plasmodium gonderi is one of the few known Plasmodium species infecting African old-world monkeys that are not found in apes. This study reports a de novo assembled P. gonderi genome with complete chromosomes. The P. gonderi genome shares codon usage, syntenic blocks, and other characteristics with the human parasites Plasmodium ovale s.l. and Plasmodium malariae, also of African origin, and the human parasite Plasmodium vivax and species found in nonhuman primates from Southeast Asia. Using phylogenetically aware methods, newly identified syntenic blocks were found enriched with conserved metabolic genes. Regions outside those blocks harbored genes encoding proteins involved in the vertebrate host-Plasmodium relationship undergoing faster evolution. Such genome architecture may have facilitated colonizing vertebrate hosts. Phylogenomic analyses estimated the common ancestor between P. vivax and an African ape parasite P. vivax-like, within the Asian nonhuman primates parasites clade. Time estimates incorporating P. gonderi placed the P. vivax and P. vivax-like common ancestor in the late Pleistocene, a time of active migration of hominids between Africa and Asia. Thus, phylogenomic and time-tree analyses are consistent with an Asian origin for P. vivax and an introduction of P. vivax-like into Africa. Unlike other studies, time estimates for the clade with Plasmodium falciparum, the most lethal human malaria parasite, coincide with their host species radiation, African hominids. Overall, the newly assembled genome presented here has the quality to support comparative genomic investigations in Plasmodium.

A meta-analysis of impacts of immune response and infection on oxidative status in vertebrates

Inferring from patterns observed in biomedical research, ecoimmunological theory predicts that oxidative stress is a ubiquitous physiological cost that contributes to generating variation in immune function between individuals or species. This prediction is, however, often challenged by empirical studies testing the relationship between immune response or infection and oxidative status markers. This points out the importance of combining ecological immunology and oxidative stress ecology to further our understanding of the proximate causes and fitness consequences of individual variation in health, and adaptability to natural and anthropogenic environmental changes. I reviewed evidence and performed phylogenetic meta-analyses of changes in oxidative status markers owing to either injection of an antigen or infection in captive and free-living vertebrates (141 studies, 1262 effect sizes, 97 species). The dataset was dominated by studies on fish, birds and mammals, which provided 95.8% of effect sizes. Both antigen injection and parasite exposure were associated with changes of oxidative status. There were significant effects of taxonomic class and experimental environment (captivity vs. wild). In contrast with my predictions, age category (young vs. adult), study design (correlational vs. experimental) and proxies of pace of life (clutch size, litter size, and body mass; for birds and mammals only) were negligible in this dataset. Several methodological aspects (type of immunostimulant, laboratory assay, tissue analysed) showed significant effects on both strength and direction of effect. My results suggest that alterations of oxidative status are a widespread consequence of immune function across vertebrates. However, this work also identified heterogeneity in strength and direction of effect sizes, which suggests that immune function does not necessarily result in oxidative stress. Finally, this work identifies methodological caveats that might be relevant for the interpretation and comparability of results and for the application in conservation programs.

Ecological, parasitological and individual determinants of plasma neopterin levels in a natural mandrill population

Investigating how individuals adjust their investment into distinct components of the immune system under natural conditions necessitates to develop immune phenotyping tools that reflect the activation of specific immune components that can be measured directly in the field. Here, we examined individual variation of plasma neopterin, a biomarker of Th1 immunity in wild mandrills (Mandrillus sphinx), who are naturally exposed to a suite of parasites, including simian retroviruses and malaria agents. We analyzed a total of 201 plasma samples from 99 individuals and examined the effect of sex, age, social rank, reproductive state and disease status on neopterin levels. We found higher neopterin concentrations in males than females, but were unable to disentangle this effect from possible confounding effects of retroviral infections, which affect nearly all adult males, but hardly any females. We further detected a non-linear age effect with heightened neopterin levels in early and late life. In addition, adult males that harbored very high parasitaemia for Plasmodium gonderi also showed high neopterin levels. There was no effect of social rank in either male or female mandrills, and no effect of female reproductive state. Taken together, these results indicate that plasma neopterin may prove useful to investigate individual variation in investment into specific immune components, as well as to monitor the dynamics of immune responses to naturally occurring diseases that elicit a Th1 immune response.