DnaJ, a promising vaccine candidate against Ureaplasma urealyticum infection.

Ureaplasma urealyticum (U. urealyticum, Uu) is a common sexually transmitted pathogen that is responsible for diseases such as non-gonococcal urethritis, chorioamnionitis, and neonatal respiratory diseases. The rapid emergence of multidrug-resistant bacteria threatens the effective treatment of Uu infections. Considering this, vaccination could be an efficacious medical intervention to prevent Uu infection and disease. As a highly conserved molecular chaperone, DnaJ is expressed and upregulated by pathogens soon after infection. Here, we assessed the vaccine potential of recombinant Uu-DnaJ in a mouse model and dendritic cells. Results showed that intramuscular administration of DnaJ induced robust humoral- and T helper (Th) 1 cell-mediated immune responses and protected against genital tract infection, inflammation, and the pathologic sequelae after Uu infection. Importantly, the DnaJ protein also induced the maturation of mouse bone marrow-derived dendritic cells (BMDCs), ultimately promoting naïve T cell differentiation toward the Th1 phenotype. In addition, adoptive immunization of DnaJ-pulsed BMDCs elicited antigen-specific Immunoglobulin G2 (IgG2) antibodies as well as a Th1-biased cellular response in mice. These results support DnaJ as a promising vaccine candidate to control Uu infections. KEY POINTS: • A novel recombinant vaccine was constructed against U. urealyticum infection. • Antigen-specific humoral and cellular immune responses after DnaJ vaccination. • Dendritic cells are activated by Uu-DnaJ, which results in a Th1-biased immune response.