MicroRNAs As Biomarkers of Immunomodulation in Migration Champions

Pollutant exposure has been linked to immunosuppression and disease outbreaks in various wildlife species. Yet, our understanding of the molecular mechanisms involved in pollutant-induced immunomodulation remains limited. Recently, microRNAs have been identified as key regulators of the immune response and important determinants of disease outcomes. MicroRNAs are a class of small noncoding RNAs that bind specific mRNA transcripts (from the host cell as well as from viruses) and prevent their translation into proteins. Alterations in microRNA expression have been found after exposure to various pollutants and pathogens (e.g. influenza virus). Recent in vitro studies have demonstrated that pollutants deregulate microRNA pathways involved in antiviral responses. MicroRNAs might therefore be a mechanistic link in our understanding of pollutant-induced immunomodulation. The presence and stability of microRNAs in blood makes them potentially interesting biomarkers of pollution-induced disease outcomes. As part of the COAST IMPACT project, we study the potential of microRNAs as biomarkers of pollution exposure and disease in migratory shorebirds of the East Asian Australian flyway (EAAF). EAAF shorebirds are facing significant conservation threats and many populations are declining. The role of pollutant exposure in these declines remains unclear. The detrimental effects of pollution exposure might further be exacerbated in these birds due to their energy-demanding annual extreme migrations, where lipophilic pollutants can redistribute in tissues and potentially cause toxicity. Next-generation sequencing was used to characterise the microRNA profiles in serum from shorebirds with different avian influenza virus status. We will present potential target sequences of the identified serum microRNAs in the shorebird transcriptome and virome. Furthermore, blood pollutant concentrations will be analysed alongside microRNA profiles to investigate potential microRNA signatures of pollution exposure. The identification of specific microRNA profiles associated with infectious disease and/or pollution exposure could (i) elucidate the molecular mechanisms inducing pollutant-induced immunomodulation, and (ii) facilitate the assessment of pollution exposure effects in free-living birds of conservation concern.