Transcriptomic analysis of the immune response to vaccination and vaccine components by high-throughput RNA sequencing (RNA-Seq) in sheep

Abstract

The sheep is an important domestic animal and it is a useful model organism for cardiology research, respiratory and reproductive medicine. Sheep can be affected by a variety of infectious diseases and vaccinations are an integral part of a flock health management program. Aluminum is the most widely used adjuvant in both human and veterinary vaccines under the form of aluminum salts. Whereas they function as an excellent adjuvant, their toxic effects are only partially known. In fact, a form of autoimmune/autoinflammatory syndrome induced by adjuvants has been described in commercial sheep, linked to the repetitive inoculation of aluminum-containing adjuvants through vaccination. In order to characterise the immune response to vaccination in general, and to adjuvants in particular, blood samples were taken from animals involved in a repetitive vaccination experiment at the beginning and at the end of the treatment. RNA was extracted from PBMC and total RNA and miRNAs were analysed by RNA-Seq technology. A total of 845,89 milllions paired-end reads were obtained from the total RNA sequencing and 206 millions reads from the miRNA sequencing of the 12 samples analysed. An alignment of the reads to the Ovis aries Oar_v3.1 genome yielded a mean of 62.57% of the reads per total RNA-Seq sample that aligned to unique locations in the ovine genome. In the case of miRNAs, 43.35% and 37.35% were aligned to unique locations and multiple locations respectively. Functional characterisation of differentially expressed genes and regulatory elements is currently underway. To the best of our knowledge, this study represents the first application of RNA-Seq technology for transcriptomic studies in response to vaccination in sheep. The identification of gene signatures that are activated by vaccines and adjuvants will provide insight into the mechanisms that underlie the immune response and could help in improving them. Moreover, the sheep could be used also as a model to disentangle the autoimmune/ autoinflammatory syndrome induced by adjuvants or other similar diseases affecting both human and animals.