Applying proteomics to investigate bacterial pathogens of veterinary importance

摘要

Proteomics offers alternative methods to assess pathogenic mechanisms of infection which can be specifically applied to animal models of disease. These concepts are illustrated using two different, yet significant, bacterial pathogens of veterinary importance.Pathogenic species of Leptospira cause leptosprrosis, a disease of many domestic animal species including dogs, cattle, sheep and pigs. Leptospires colonize the renal tubules of reservoir hosts of infection, from which they are excreted via urine into the environment. Rattus norvegicus is a reservoir host for Leptospira interrogans and experimentally infected rats remain clinically normal, yet persistently excrete large numbers of leptospires from colonized renal tubules via urine, despite a specific host immune response. Whilst persistent renal colonization and shedding is facilitated in part by differential antigen expression by leptospires to evade host immune responses, there is limited understanding of kidney and urinary proteins expressed by thehost that facilitates such biological equilibrium. Urine pellets were collected from experimentally infected rats shedding leptospires and compared to urine from non-infected controls spiked with in vitro cultivated leptospires for analysis by 2-dimensional difference gel electrophoresis (DIGE). Differentially expressed host proteins include membrane metallo endopeptidase, napsin A aspartic peptidase, vacuolar H+ATPase, kidney aminopeptidase and immunoglobulin G and A. Loa22, a virulence factor of Leptospira, as well as the GroEL, were increased in leptospires excreted in urine compared to in vitro cultivated leptospires. Urinary IgG from infected rats was specific for leptospires. Results confirm differential protein expression by both host and pathogen during chronic disease and include markers of kidney function and immunoglobulin which are potential biomarkers of infection.