Immunogenicity and humoral and cell-mediated immune responses to leptospiral whole cell, outer envelope, and protoplasmic cylinder vaccines in hamsters and dogs.

The immunogenicity of 2 leptospiral cell structural components, the outer envelope (OE) and protoplasmic cylinder (PC), as well as the leptospire whole cell (WC), was compared in hamsters and dogs. The 50% protective dose for hamsters against death (PD50D) and kidney infection (PD50k) was evaluated for Leptospira interrogans serovars canicola, icterohaemorrhagiae, pomona, and grippotyphosa. All 3 immunogens had similar PD50D values. However, the PD50K values for OE and WC vaccines ranged from 0.05 to 0.80 micrograms (dry weight), whereas the PC vaccines ranged from 7.0 to 14.0 micrograms. Cellular and humoral responses of dogs to serovar canicola WC, OE, and PC vaccines were monitored for 21 weeks. Little difference was observed among the canine humoral responses to the different preparations. Protoplasmic cylinder vaccines sensitized the greater population of lymphoid cells followed by OE and WC. Cross-reactivity was greater in the blastogenic response of lymphoid cell populations than in the humoral response.