Aluminium hydroxide adjuvants are crucial for livestock and human vaccines. Few studies have analysed their effect on the central nervous system in vivo. In this work, lambs received three different treatments of parallel subcutaneous inoculations during 16 months with aluminium-containing commercial vaccines, an equivalent dose of aluminium hydroxide or mock injections. Brain samples were sequenced by RNA-seq and miRNA-seq for the expression analysis of mRNAs, long non-coding RNAs and microRNAs and three expression comparisons were made. Although few differentially expressed genes were identified, some dysregulated genes by aluminium hydroxide alone were linked to neurological functions, the lncRNA TUNA among them, or were enriched in mitochondrial energy metabolism related functions. In the same way, the miRNA expression was mainly disrupted by the adjuvant alone treatment. Some differentially expressed miRNAs had been previously linked to neurological diseases, oxidative stress and apoptosis. In brief, in this study aluminium hydroxide alone altered the transcriptome of the encephalon to a higher degree than commercial vaccines that present a milder effect. The expression changes in the animals inoculated with aluminium hydroxide suggest mitochondrial disfunction. Further research is needed to elucidate to which extent these changes could have pathological consequences.

BackgroundMicroRNAs (miRNAs) are short endogenous, single-stranded, noncoding small RNA molecules of approximately 22 nucleotides in length. They regulate gene expression posttranscriptionally by silencing mRNA expression, thus orchestrating many physiological processes. The Small Ruminant Lentiviruses (SRLV) group includes the Visna Maedi Virus (VMV) and Caprine Arthritis Encephalitis (CAEV) viruses, which cause a disease in sheep and goats characterized by pneumonia, mastitis, arthritis and encephalitis. Their main target cells are from the monocyte/macrophage lineage. To date, there are no studies on the role of miRNAs in this viral disease.ResultsUsing RNA-seq technology and bioinformatics analysis, the expression levels of miRNAs during different clinical stages of infection were studied. A total of 212 miRNAs were identified, of which 46 were conserved sequences in other species but found for the first time in sheep, and 12 were completely novel. Differential expression analysis comparing the uninfected and seropositive groups showed changes in several miRNAs; however, no significant differences were detected between seropositive asymptomatic and diseased sheep. The robust increase in the expression level of oar-miR-21 is consistent with its increased expression in other viral diseases. Furthermore, the target prediction of the dysregulated miRNAs revealed that they control genes involved in proliferation-related signalling pathways, such as the PI3K-Akt, AMPK and ErbB pathways.ConclusionsTo the best of our knowledge, this is the first study reporting miRNA profiling in sheep in response to SRLV infection. The known functions of oar-miR-21 as a regulator of inflammation and proliferation appear to be a possible cause of the lesions caused in the sheep’s lungs. This miRNA could be an indicator for the severity of the lung lesions, or a putative target for therapeutic intervention.Electronic supplementary materialThe online version of this article (10.1186/s12864-018-5416-0) contains supplementary material, which is available to authorized users.

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Accumulative evidence has shown that short non-coding RNAs such as miRNAs can regulate the innate and adaptive immune responses. Aluminium hydroxide is a commonly used adjuvant in human and veterinary vaccines. Despite its extended use, its mechanism of action is not fully understood and very few in vivo studies have been done to enhance understanding at the molecular level. In this work, we took advantage of a previous long-term experiment in which lambs were exposed to three different treatments by parallel subcutaneous inoculations with aluminium-containing commercial vaccines, an equivalent dose of aluminium or mock injections. Spleen samples were used for miRNA-seq. A total of 46 and 16 miRNAs were found differentially expressed when animals inoculated with commercial vaccines or the adjuvant alone were compared with control animals, respectively. Some miRNAs previously related to macrophage polarization were found dysregulated exclusively by the commercial vaccine treatment but not in the aluminium inoculated animals. The dysregulated miRNAs in vaccine group let-7b-5p, miR-29a-3p, miR-27a and miR-101-3p are candidates for further research, since they may play key roles in the immune response induced by aluminium adjuvants added to vaccines. Finally, protein–protein interaction network analysis points towards leucocyte transendothelial migration as a specific mechanism in animals receiving adjuvant only.

Background Long non-coding RNAs (lncRNAs) are involved in several immune processes, including the immune response to vaccination, but most of them remain uncharacterised in livestock species. The mechanism of action of aluminium adjuvants as vaccine components is neither not fully understood. Results We built a transcriptome from sheep PBMCs RNA-seq data in order to identify unannotated lncRNAs and analysed their expression patterns along protein coding genes. We found 2284 novel lncRNAs and assessed their conservation in terms of sequence and synteny. Differential expression analysis performed between animals inoculated with commercial vaccines or aluminium adjuvant alone and the co-expression analysis revealed lncRNAs related to the immune response to vaccines and adjuvants. A group of co-expressed genes enriched in cytokine signalling and production highlighted the differences between different treatments. A number of differentially expressed lncRNAs were correlated with a divergently located protein-coding gene, such as the OSM cytokine. Other lncRNAs were predicted to act as sponges of miRNAs involved in immune response regulation. Conclusions This work enlarges the lncRNA catalogue in sheep and puts an accent on their involvement in the immune response to repetitive vaccination, providing a basis for further characterisation of the non-coding sheep transcriptome within different immune cells.