A Brucella suis locus involved in membrane homeostasis and virulence in mice

RUIZ-RANWEZ, V.; ESTEIN, S.; BIALER, M.G.; RUSSO D.M.; POSADAS, D. M.; ABDIAN P.L.; ZORREGUIETA A.

Medellin

Congreso; IMMUNOCOLOMBIA 2015.11th Congress of the Latin American Association of Immunology. 10o Congreso de la Asociación Colombiana de Alergia, Asma e Inmunología.; 2015

Latin American Association of Immunology and Asociación Colombiana de Alergia, Asma e Inmunología

Brucella species exhibit characteristic surface properties, which make them furtive pathogens and more resistant to several host defense compounds such as polycationic peptides. We have identified a gene of Brucella suis encoding a hypothetical protein (MapA)(highly conserved in the genus) that is predicted to contain two AsmA_2domains, which are related to envelope biogenesis functions. The B. suis delta mapA mutant did not show differences compared with the parental strain regarding growth, outer membrane protein profiles, tolerance to acidic pH, oxidative stress or to complement from porcine serum. In contrast, the mutant was impaired in the ability to bind to HeLa cells. Besides, the mutant showed enhanced sensitivity to Triton X-100, Polymyxin B and Lysozyme.Lipopolysaccharide analysis suggests that the O-antigen region is not alteredin the delta mapA mutant. Interestingly, the mutant colonies showed much less crystal violet staining compared with the wild type. In addition, Fluorescein(FITC)-conjugated goat anti- Brucella (S) antibody showed similar degree ofr eactivity to the mutant and the wild type strain. Finally, we evaluated the virulence of the mutant using the mouse model. The number of Colony FormingUnits (CFU) recovered from spleens of mice infected with the mutant, 15 and 45days post infection, was lower compared with the wild type strain. Buffered Plate Antigen Test (BPAT) is the most common serological test in brucellosis.This test detects anti-Brucella antibodies, mainly anti-LPS antibodies. Sera collected from mice inoculated with mutant or wild type strain did not show difference in reactivity to BPAT antigen supporting the idea that the O-antigen region is not altered in the delta mapA mutant strain. We propose that MapA is involved in cell envelope biogenesis, which in turn influences bacterial virulence. In future studies we will evaluate this mutant as a vaccine against virulent Brucella suis.