Transcriptomic profiling reveals early immune activation and metabolic remodeling in lymphoid tissues following in ovo Marek's disease virus mRNA vaccination in chickens.

Abstract

Marek's disease virus (MDV) is a highly contagious oncogenic alphaherpesvirus that continues to threaten global poultry production, highlighting the need for next-generation vaccines. Although in ovo delivery of conventional MDV vaccines has been effective, vaccine leakiness has accelerated viral evolution by promoting the selection of more virulent, immune-evasive strains. mRNA vaccines offer a flexible and rapidly adaptable platform capable of inducing potent immune responses, yet their application against MDV remains unexplored in the in ovo context. Here, we report the first in ovo administration of a bivalent MDV mRNA vaccine encoding glycoprotein B (gB) and phosphoprotein 38 (pp38). RNA sequencing of the spleen and bursa of Fabricius at 12-, 24-, and 48-hours post-vaccination revealed distinct, time- and tissue-specific transcriptional programs. In the spleen, differential expression analysis (fold-change &#x2265; 2, padj < 0.05) demonstrated early activation of caudal-type homeobox 1 (CDX1) and signal transducer and activator of transcription 1 (STAT1), together with interferon-stimulated antiviral genes MX dynamin-like GTPase 1 (MX1), 2'-5'-oligoadenylate synthetase-like (OASL), and interferon-induced protein with tetratricopeptide repeats 5 (IFIT5). In contrast, the bursa exhibited persistent modulation of colipase (CLPS), chymotrypsinogen B1 (CTRB1), and deoxyribonuclease I (DNASE1), indicating metabolic and apoptotic remodeling. These results demonstrate that in ovo mRNA vaccination against MDV rapidly activates organ-specific immune and metabolic pathways, providing a transcriptomic framework for the rational design of poultry mRNA vaccines.