Expression of SipA and SopD Effectors of Salmonella Typhimurium during systemic infection of mice

GIACOMODONATO MN, SARNACKI SH, NOTO LLANA MA, UZZAU S, RUBINO S, CERQUETTI MC

Rosario, Argentina

Congreso; SAIB 2006. XLII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2006

SAIB. Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Salmonella pathogenicity island 1 (SPI1) mediates invasion of epithelial cells. SipA and SopD are required in this step of Salmonella infection. We studied the expression of SipA and SopD in vivo. SopD and sipA tagged strains (3xFLAG) of S. Typhimurium were used during the experiments. Firstly, strains were grown under SPI1 or SPI2 conditions, supernatants and pellets were used to investigate secreted and cell associated proteins, respectively. Expression and secretion were analyzed by SDS-page and immunoblotting with anti-FLAG antibodies. SipA and SopD expression was observed under SPI1 and SPI2 conditions. However, secretion only occurred under SPI1 conditions. Hep-2 cells were infected with these strains at a moi of 10:1. Bacteria recovered from infected monolayers showed SipA and SopD expression at 24 hs post infection (p.i.). In a mouse model of systemic infection, internalized bacteria were recovered from lymph nodes (LN) and spleen after intraperitoneal inoculation. Western blot analysis revealed that SopD and SipA were expressed in vivo 18 hs and 5 days p.i. Moreover, SopD translocation was detected in LN macrophages. These results indicate that S. Typhimurium colonizing deep organs expresses effector proteins that may participate during late stages of systemic infection.