An immunoprotective molecule, the major secretory protein of Legionella pneumophila, is not a virulence factor in a guinea pig model of Legionnaires' disease.

Abstract

We have examined whether a molecule that is capable of inducing immune protection, the major secretory protein (MSP) of Legionellapneumophila, is required for virulence in a guinea pig model of Legionnaires' disease. To do so, we have compared the virulence in guinea pigs of an isogenic pair of L. pneumophila, Philadelphia 1 strain, one of which produces MSP (MSP+) and one of which does not (MSP-).Both the MSP-strain and the MSP+ strain of L. pneumophila are highly virulent for guinea pigs, inducing similar signs and progression of illness. Both strains are lethal and have comparable LD50s and LD100s. Both strains multiply in the lungs of guinea pigs at a similar rate, and both strains produce indistinguishable pathological lesions in the lungs. Both strains maintain a stable phenotype with guinea pig passage, i.e., the MSP-strain does not regain the capacity to secrete MSP and the MSP+ strain retains its capacity to secrete MSP after lung passage.

Recombinant BCG expressing Mycobacterium tuberculosis major extracellular proteins

“…Over fifteen years ago, we proposed a hypothesis to address these issues -the Extracellular Protein Hypothesis [16][17][18][19][20][21][22]. The Extracellular Protein Hypothesis has three major components.…”

Demonstration of the intracellular production of tissue-destructive protease by Legionella pneumophila multiplying within guinea-pig and human alveolar macrophages

“…More recently, described a transposon mutant of L. pneumophila Philadelphia 1 strain which was deficient in protease (major secretory protein, MSP) production. When tested in an aerosol infection guinea-pig model, the mutant was as lethal as its parent strain (Blander et al, 1990). It was thus concluded that the MSP is not a virulence factor of L.…”

Interferon-gamma (IFN-γ) production by human T lymphocytes uponLegionella pneumophilastimulationin vitro

“…[25]. Immunization with MSP or the formalin-killed bacterium induced protective immunity in guinea pigs [25,26]. The bacterial culture supernatant used in the present study may contain a variety of antigenic substances which induce IL-4 mRNA, and we do not know yet whether MSP induces IL-4 mRNA.…”

“…In order to investigate the roles of substances released from the bacterium in the immune response, we improved the methods for bacterial culture. !t is known that L. pneumophila can be cultured in a liquid medium which contains yeast extract [25]. To avoid the effects of unrelated substances derived from the ingredients on the T cell response, we cultured the bacterium in the RPMI 1640-based synthetic medium (see Materials and Methods).…”

“…A major secretory protein (MSP) from L. pneumophila culture supernatants, with a molecular mass of 39 kD, was reported by Blander etal. [25]. Immunization with MSP or the formalin-killed bacterium induced protective immunity in guinea pigs [25,26].…”