RPSA distribution and expression in tissues and immune cells of pathogen-infected mice

40S ribosomal protein SA (RPSA), a component of the small ribosomal subunit, is a high-affinity receptor of laminin that is widely expressed in cells and involves in many biological processes. However, it hasn't been reported which tissues and cells may be targeted by RPSA-mediated pathogen regulation. Therefore, in this study, a gram-positive bacterium Streptococcus suis Type 2 (SS2), gram-negative bacterium Actinobacillus pleuropneumoniae (A.pleuropneumoniae), and porcine circovirus Type 2 (PCV2) were used to infect ICR mice.

The effects of infection with the three pathogens on expression levels of RPSA in mouse tissues and peripheral blood immune cells were analysed by immunohistochemistry and flow cytometry. The results suggested that the pathological changes in mice infected with SS2 were mainly manifested as congestion and inflammatory infiltration in the meninges, lungs, hearts and livers. The mice infected with A.pleuropneumoniae or PCV2 showed lung lesions and mild hepatocyte degeneration, respectively. In uninfected mice, RPSA protein was expressed to various degrees in all tissues except the spleen. After SS2 infection for 3 d, the expression of RPSA in the liver and brain increased, while decreased significantly in the heart and duodenum. These results were corroborated on examining the correlation between RPSA expression and the process of SS2 infection, except that there was no significant difference between the expression levels in the heart at 1 d and 3 d. After A.pleuropneumoniae and PCV2 infection for 3 d, the expression of RPSA decreased in the heart, and brain, respectively. Additionally, under physiological conditions, RPSA expression in CD4⁺ T cells, CD8⁺ T cells, neutrophils, and macrophages in the peripheral blood of mice was higher than that in B cells and NK cells. After SS2 infection for 3 d, RPSA expression increased significantly in CD4⁺ T cells and CD8⁺ T cells but decreased significantly in macrophages. The expression of RPSA after A.pleuropneumoniae and PCV2 infection were similar, and RPSA expression decreased only in macrophages.

The results revealed that RPSA showed different expression levels in tissues and immune cells due to different pathogens causing disease courses, suggesting different target tissues and target cells in RPSA-mediated pathogenesis after infection, which supports the systematic study of the pathogenesis of RPSA in infectious diseases.