To investigate the diversity in kinetic change of adaptive immunity to experimental bacterial meningitis in T1/T2 doubly transgenic mice infected with variant strains of Haemophilus influenzae

• Main Authors: Shyi-Jou Chen, 陳錫洲
• Other Authors: Chih-Chien Wang
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/38533652174726587474

博士 === 國防醫學院 === 醫學科學研究所 === 94 === To investigate the immunopathogenic mechanism of Haemophilus influenzae meningitis, we established an experimental meningitis model and elucidated the immune responses in T1/T2 doubly transgenic mice based on BALB/c mice background. These mice carry two transgenes that express two distinct cell-surface markers: a human Thy1 transgene (hThy1) under the control of the murine IFN-γ promoter, and a murine Thy1.1 transgene (mThy1.1) under the control of the murine IL-4 promoter, designated T1 and T2, respectively. These mice were infected with variant strains of H. influenzae including invasive and colonized nontypeable H. influenzae (NTHi). Moreover, mice inoculated with H. influenzae type b (Hib) were dissected for comparison. We disclosed mice infected with Hib, invasive NTHi (INTHi) or colonized NTHi (CNTHi) revealing most severe, moderate and less mild in disease severity in terms of clinical score, mortality rate and histopathology of brain respectively. In addition, mice infected with Hib displayed severest symptoms and lowest total splenocyte counts on day 3 after infection. Simultaneously, we examined the significantly low percentage of CD19+ B cells, the relatively high level of CD4+ T cells and significantly high percentage of CD8+ T cells in Hib-infected mice. We observed a rapid induction of the Th1 response, since the IFN-γ-producing CD4+ T cells significantly increased in all infected T1/T2 doubly transgenic mice. Furthermore, T1/T2 doubly transgenic mice infected with CNTHi expressed the most significant Th1 response, in terms of preferential increase of CD4+ T cells, as well as the highest percentage and longest maintenance of Th1 cells. In contrast, in transgenic mice infected with invasive Hib, the Th1/Th2 paradigm shifted to Th2 response. On day 7 after infection, the Th1 response gradually declined and the Th2 response rather sustained in Hib infected mice. This was due to a significant increase in IL-4-producing CD4+ T cells, accompanied by a rapid decline of Th1 cells. Mice infected with INTHi revealed intermediate Th1/Th2 responses between those of mice infected with CNTHi and Hib. Two weeks after infection, both Th1 and Th2 cells were barely detectable. Moreover, we demonstrated using an antigen-specific re-stimulation test to analyze the effector function of lymphocyte subsets that CD8+ T cells contributed to more predominantly production of IFN-γ than CD4+ T cells did; and CD4+ T cells partly contributed to the secretion of IL-4 from flowcytometry of intracellular cytokine staining in Hib infected mice. In conclusion, the preferential Th1/Th2 trend in H. influenzae meningitis is correlated with clinical severity as well as characteristics of the pathogens themselves.Our results support that these transgenic mice provide an available model to dissect the complex kinetic change of adaptive immunity in bacterial infectious diseases.