Omp19 plays a key role in Brucella abortus´s ability to establish chronic infection after oral ingestion

CARAVAJAL MARIANELA; KARINA A. PASQUEVICH; GUAIMAS, FRANCISCO; LAURA BRUNO; GABRIELA S. RISSO; COMERCI DIEGO; CASSATARO JULIANA

Congreso; Reunión Conjunta de Sociedades de Biociencias; 2017

Oral infection is one of the principal ways in which brucellosis is acquired. Animals usually sniff and lick fetal and placental tissues from abortions caused by brucellae. Transmission of brucellosis to humans may occur by consumption of infected, unpasteurized animal milk products. We have previously demonstrated that U-Omp19 from Brucella spp. is a broad-spectrum protease inhibitor: inhibits main gastrointestinal and lysosomal proteases; moreover Omp19 has a role in B. abortus virulence after intragastric ?gavage- infection. In this work, the role of Omp19 in B. abortus oral infection was studied in depth. In this case BALB/c mice were directly inoculated at the oral cavity with wt or a mutant B. abortus strain without Omp19 (Δomp19). At 20 days post infection there were very few colonies of Δomp19 strain at the spleens indicating this strain was highly attenuated (P<0.01 vs wt). Omp19 protects B. abortus from main gut proteases since Δomp19 strain was more susceptible to mouse intestine lysates and to pancreatin (commercial pig pancreatic extract) than wt strain (P<0.001). When incubated with intestinal extracts the wt strain could grow but a bacteriostatic effect was evident in Δomp19 strain. This bacteriostatic effect was also found in vivo in gut isolated Δomp19 strain 2h after oral infection of mice. Confocal microscopy images revealed that when exposed to pancreatin wt strain formed normal colonies, but Δomp19 strain formed no or small colonies, with a significant reduction in the number of cell divisions (P<0.05). Cell cycle progression analysis by flow cytometry indicated a pancreatin-induced cell cycle arrest at G1 in Δomp19 strain that was not evident in wt strain. Thus, Omp19 deficiency leads to B. abortus cell division defects and cell cycle arrest when exposed to pancreatic proteases. Altogether these results demonstrate that Omp19 has a crucial role in the establishment of chronic Brucella infection after oral route.