Immuno-profiles of BALB/c mice inoculated with Salmonella vector delivering B-cell mitogen hydroxyproline epimerase.

The enzyme 4-hydroxyproline 2-epimerase (PrpA) involves in modulation of host immunity and is also reported as a potent B-cell mitogen. Live attenuated Salmonella Typhimurium (ST) vector constitutively expressing heterologous Brucella abortus PrpA protein (ST-PrpA) was inoculated in BALB/c mice in order to investigate the influence of the enzyme, on safety aspects, humoral and cellular immunity as well as protective efficacies against wild type challenges. No aggravation of morbidity was observed upon mice inoculation of ST-PrpA. Immunized mice showed significantly quicker anti-Salmonella IgG responses as compared to ST only immunization. This finding is in congruency with the increase IL-4 production evident in in vitro pulsed mice splenocytes. Increase protection against Salmonella challenge was also observed. These findings suggest that PrpA can be used as a protein adjuvant in a live Salmonella delivery system, in order to increase humoral responses effectively without major interference on the cell mediated immunity.