Genetic modification of a vaginal strain of Lactobacillus fermentum and its maintenance within the reproductive tract after intravaginal administration

Many micro-organisms cause important diseases of the female genital tract. Because systematic vaccination does not usually provide a good immune response at mucosal sites, commensal lactobacilli from the female genital tract were developed as vehicles to deliver continued doses of foreign antigen directly to the genital mucosal surface with the aim of stimulating strong local mucosal immune responses. Lactobacilli were shown to be common inhabitants of the genital tract of the animal model studied, the guinea-pig. One species, Lactobacillus fermentum, was found in all guinea-pigs studied and was chosen for genetic manipulation. Improved methods of electroporation were developed to enable the routine transformation of L. fermentum BR11 strain with the broad host range plasmid pNZ17. This recombinantly modified Lactobacillus strain was shown to possess good segregational stability over 120 generations in the absence of antibiotic selection. When this recombinant L. fermentum strain was administered to the vaginal tract of three guinea-pigs it persisted for only 5 days. Despite the relatively short period of persistence in these initial experiments, this novel vaccine approach could provide an effective means of stimulating mucosal immunity in the female genital tract