From our understanding, WT strain could utilize selleck chemicals the synergic effect of toxins and high level of cytokines to accelerate the penetration of deep tissue and BBB. These might be the reason why the strain could cause severe human diseases in Sichuan, 2005. Conclusions Microarray technology has been used to analyse the globle porcine transcriptional response to infection with various pathogenic microorganisms recently. Study on the transcriptional response to the Gram positive bacterium SS2 by using the Affymetrix GeneChip Porcine Genome Array has not been reported until now. Although great efforts have been made to understand the molecular basis of this infection, the response to SS2 infection is still largely unknown. Transcriptome analysis based on S.

suis infected spleens could improved the interference received by the cells analysis, and also supply the solid supplementary for analysis on alveolar macro phages. Highly pathogenic S. suis could persistently induce cytokines mainly by TLR2 pathway, and even tually the high level of cytokines and toxins secreted by phagocytosis resistant bacteria could destroy deep tis sues, and cause meningitis, septicaemia, pneumonia, endocarditis, and arthritis. Methods Bacterial strains SS2 strain 05ZY which was isolated from the brain of a diseased piglet collected in Sichuan outbreak in China 2005 showed high virulence to pigs, and was applied to infect pigs. An isogenic HP0197 mutant derived strain 05ZY showed no obvious virulence to pigs was applied as a control.

Animals infection and tissue collection All the experimental protocols were approved by the Laboratory Animal Monitoring Committee of Hubei Province and performed accordingly. A total of 12 pigs of high health status were assigned to three groups, within four in each. The pigs were determined to be SS2 free by antibody based ELISA and nasal swabs based bacteriologic test. One hour before inoculation, all pigs were given 2 ml of 1% acetic acid intranasally to enhance the sensitivity of the S. suis challenge. Two groups were inoculated intrana sally with 1 ml of 2��106CFU of WT strain or HP0197 respectively, and the rest group inoculated with PBS was served as control. All pigs inoculated with WT showed typical symptoms at day 3 while pigs inoculated with HP0197 or PBS showed no significant clinical signs. Blood samples from each group were detected for bac terial burden.

Bacteria could be found in the blood of pigs in the WT group at day 3 post inoculation while no bacterium was found from the blood of pigs inocu lated with isogenic mutant strain or PBS at the same time point. All pigs were sacrificed at day 3, and their tissue samples were cultured to prove in vivo bacterial burden. Bacteria were found in the spleens of the WT group, AV-951 and no bacterium was found in the other two groups. Spleen samples were aseptically collected and immediately frozen in liquid nitrogen for future RNA isolation.