IMMUNOGENICITY OF A NEW LOT OF FRANCISELLA-TULARENSIS LIVE VACCINE STRAIN IN HUMAN VOLUNTEERS

A new lot of Francisella tularensis live vaccine strain (LVS) was test ed for immunogenicity in 19 human volunteers, Scarification vaccinatio n induced specific cell-mediated and humoral immune responses, We note d a significant rise in antibodies against irradiation-killed LVS, for malin-killed virulent strain SCHU4, and an ether extracted antigen pre paration (EEx) beginning 14 days after vaccination. A main target of t he humoral immune response was lipopolysaccharide. Eighty percent of v accinated volunteers developed a positive Ige response to EEx by day 1 4 and 100% of vaccinees responded positively by day 21, Background IgA titers were lower than corresponding IgG or IgM titers, No early IgM rise was noted with any antigen, By day 14 after vaccination, in vitro lymphocyte responses to LVS,the rough variant of LVS, and EEx were si gnificantly increased compared to controls, Seventy percent of volunte ers had a positive in vitro lymphocyte response to EEx within 14 days of vaccination, We predict that EEx will be a useful antigen or diagno sing tularemia and for evaluating the immunogenicity of vaccines again st tularemia. We are testing this antigen using sera from human cases of tularemia and control sera.