An infectious personality: immune personalities and their role in the transmission of wildlife infectious diseases

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Immune function is one of the most variable traits in animals with significant differences between individuals and between populations. However, it is increasingly recognized that in animal populations many individuals experience predictable and relatively stable immune responses over time. This within-individual stability in a context of high between-individual variance leads to intermediate to high repeatability in some immune traits, and the term "immune personality" has been used to describe these consistent responses over time and across environments. The origin of these immune personalities in free-ranging animal populations is not clear but recent evidence from lab animal and human populations suggests that most of the diversity in immune phenotypes is due to early life exposure to environmental pathogens and microbial commensals (microbiome). These early life microbial exposures can directly stimulate different immune pathways leaving a long-lasting imprinting in the immune system and sometimes higher levels of within-individual variance in immune traits. Interestingly, preliminary studies in people suggest that more variable immune responses overtime predict better response to vaccination. Similarly, we recently found in a wild animal population that immune personalities characterized by lower levels of within-individual variance increase tuberculosis infection risk. Therefore, wild animals exposed to different pathogens and microbiomes during early life could develop unique immune personalities that increase their chances to disseminate infectious diseases. To test this hypothesis, in this research program we will use a unique host parasite system (South American fur seal and hookworm [Uncinaria sp.]) that allows for easy manipulation of early life exposure to pathogens and commensals and allows for longitudinal tracking of immune personalities and naturally acquired infections. Using this model, we will: i) characterize the effects of neonatal hookworm infection on the host microbiome, and ii) test the effects of this disturbed microbiomes during early life on the adult immune personality. Simultaneously, we will assess the impact of these different immune personalities on the infection risk and shedding patterns of influenza viruses and seal tuberculosis (Mycobacterium pinnipediae). This research program will reveal the most important drivers of immune personalities in wildlife systems and will determine the extent of the effects of these personalities on the transmission of important infectious diseases. A better understanding on the drivers and consequences of immune personalities in free-ranging animal populations will be critical to identify through environmental monitoring individuals and populations at higher risk of infection. This program will also offer better tools to predict the impact of environmental change on wildlife immunity and the emergence of important infectious diseases