ABSTRACT
IgG and IgA O antibodies were studied in milk and sera of guinea pigs subcutaneously immunized at various stages of pregnancy with Shigella ribosomal vaccines (SRV) from Shigella sonnei and Shigella flexneri. Both vaccines induced O antibodies in milk, the level of IgA antibodies being significantly higher than that of IgG antibodies. The immune milk provided a clear-cut protection against experimental Shigella-induced keratoconjunctivitis. These results are consistent with the previously shown ability of parenteral SRV to stimulate gut-associated lymphoid tissue and confirm the involvement of secretory IgA O antibodies in the protection induced by the parenteral SRV. The high level of milk antibodies in vaccinated guinea pigs suggests the possibility to use the parenteral SRV for developing lactogenic immunity.
Subject(s)
Bacterial Vaccines/therapeutic use , Immunoglobulin A/biosynthesis , Milk/immunology , Shigella flexneri/immunology , Shigella sonnei/immunology , Animals , Animals, Newborn/immunology , Dysentery, Bacillary/immunology , Guinea Pigs , Immunoglobulin G/biosynthesis , Keratoconjunctivitis, Infectious/immunology , Keratoconjunctivitis, Infectious/prevention & controlABSTRACT
The parenteral Shigella ribosomal vaccine (SRV), which previously was shown to protect guinea pigs and monkeys, has been compared with lypopolysaccharide (LPS) for its ability to induce a systemic and a local immune response. Injection of SRV caused a significant rise of the serum O antibodies of different classes and the appearance of IgA O antibodies in tears of guinea pigs and saliva and bile of monkeys. In guinea pigs, the local IgA response to parenteral SRV was much more intensive than that to feeding of high doses of LPS, while in monkeys it was nearly as high as that to challenge with a high dose of live pathogen. These data provide an immunological basis for the protective effect of SRV and are in disagreement with the widely accepted view of the inefficiency of parenteral antigens in stimulating mucosal immunity. The results are interpreted from the viewpoint of the role of ribosomes as a delivery system for the Shigella O antigen which provides high potency of SRV in stimulating local lymphoid tissue and makes it a good vaccine candidate.
