| Summary: | 碩士 === 國防醫學院 === 病理及寄生蟲學研究所 === 85 === Japanese encephalitis (JE) is the most common mosquito-home encephalitis in Asia. JE patients usually present neuronal involvement rather than other organ involvement. The mechanism of human immune responses to this virus is still not clear. The specific aims of this study are: (1) to investigate the infectivity of Japanese encephalitis virus (JEV) in human blood, plasma and blood cells including erythrocytes, granulocytes, lymphocytes, monocytes and macrophages; (2) to explore JEV-induced cell mediated immunity including lymphoproliferation, and cytokine profiles (Th1/Th2 responses); and (3) to search for whether antibody cross neutralization or cross enhancement in those individuals infected with dengue virus (DV) after JEV infection. We found that JEV did not replicate in plasma, but whole blood supported JEV replication when a higher dose (>10(6) plaque forming unit (pfu/ml) virus was inoculated. However, JEV at MOI=l did not replicate in human erythrocytes, granulocytes or lymphocytes, but replicated well in both monocyte and macrophages with expression of viral NS3 antigen and viral yields of 80 ±30 pfu/ml in monocytes and 62.5 ±37.5 pfu/ml in macrophages. In addition, studies on the infection of monocytes and macrophages with JEV at M01=l for 3 days, showed that JEV replicated more efficiently in macrophages (3120 ±248 pfu/ml) than monocytes (91 ±6 pfti/ml), suggesting that the monocytic lineage of cells may harbor JEV through its latent infections. Studies on the cell mediated immunity demonstrated that JEV-induced lymphoproliferation was not consistently present in the human leukocytes. Production of IFNr by JEV-stimulated mononuclear leukocytes was higher than by non-JEV-stimulated cells (148 ±188 vs 49.8 ±62.9 pg/ml), whereas IL-4 production was not detectable, indicating JEV induced a Th1 immune response. For those with different immune status. Hepatitis B carriers among Taiwan population generated the highest Th1 response whereas neonates elicited the lowest Th1 reaction. Subsequent heterologous flavivirus experiments found that lymphocytes, obtained from DV-1-infected donors, in response to JEV for 6 days revealed higher Th1 reaction than those from non-immune donors (IFNr: 92.7 ±166 vs 17.9 ±7.8 pg/ml). The presence of flavivirus immune sera switched Thi toward Th2 response as demonstrated by increase ofIL-1O and decrease of IFNr. Furthermore, both DV and JEV immune sera that neutralized JEV in BHK-21 cells did enhance JEV infections in human mononuclear cells. In conclusion, JEV higher than 10(6) pfu/ml were able to infect human blood cells and elicited a Th1 immune reaction, whereas both specific and cross-reactive antibodies that could neutralize JEV infections in non-Fc-receptor bearing cells did enhance JEV infections in Fc-receptor bearing human leukocytes.
|
|---|
