Expression of microRNAs in response to a TLR dependent adjuvant PorB from Neisseria meningitidis (VAC6P.943)

Abstract

Abstract MicroRNAs (miRs) are small non-coding RNAs that are involved in post-translational modulation of gene expression. Not much is known about the role of miRs in vaccine adjuvant activity. In this study, we investigated miRs elicited by PorB, a TLR2 dependent adjuvant from N. meningitidis, in vivo and in vitro. Mice (WT) were immunized 3 times, 2 weeks apart with Ova +/- PorB. Splenic RNA was obtained 24 hours after each immunization and analyzed by microarrays. Bone marrow-derived macrophages (BMDM) from WT, MyD88 or TLR2 knock out mice were stimulated with PorB, RNA was isolated and miRs expression was determined by RT-PCR. The in vivo study revealed that miR505 and miR15a expression was increased, while miR689 and miR666 expression was decreased when PorB was included in the vaccine preparation. Interestingly the differential expression of these miRs were seen after the 2nd but not after the 1st or 3rd immunization, suggesting that the regulatory events driven by PorB occurred after the 2nd immunization. We also observed a high increase in the expression of miR155 upon stimulation with PorB in vitro, however the miR155 expression was dampened in BMDM from TLR2 knock out mice and completely abrogated in MyD88 knock out mice. PorB seems to be able to induce high level of miR155 in a TLR2 independent as well as TLR2 dependent mechanism. These data increase our understanding of the association of miR expression and PorB adjuvant activity.