Preparation, characterization, and efficacy of cell wall and ribosomal vaccines from Legionella pneumophila

Abstract

Legionella pneumophila Washington and Philadelphia L-1 strains were mechanically disrupted and cell wall and ribosomal subunits isolated by differential centrifugation. Purity and physical characteristics of each preparation were determined by electron microscopy and chemical analyses. Mice vaccinated with either Washington or Philadelphia L-1 strain cell wall or ribosomal preparations were protected against challenge with the virulent Washington strain. Complete protection was afforded to mice with as little as 5ug of protein from ribosomes of the Washington strain when administered ip. A higher concentration of ribosomal protein was required to achieve full protection when vaccination was by the sc route. Complete protection with cell wall preparations from the Washington strain was achieved by both ip and sc vaccination with a dose of 5ug of cell wall protein. A dose of 5Oug of ribosomal antigen from the Philadelphia L-1 strain, when administered ip, resulted in 50% protection of mice against a lethal challenge with the Washington strain. Cell wall preparations, on the other hand, afforded full protection. Neither ribosomes or cell walls from Philadelphia L-1 protected mice when administered sc. Microagglutination titers with Washington strain antigen, unlike those with Philadelphia L-1 antigen, correlated with protective response. Immunoprecipitin analyses indicated greater cross-reactivity between strains in those antisera produced with cell wall or ribosomal preparations from the Washington strain than in those produced with the Philadelphia L-1 strain preparations.