Dix Richard, Cousins Scott
Department of Ophthalmology, Jones Eye Institute, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
Curr Eye Res. 2003 Mar-Apr;26(3-4):211-7. doi: 10.1076/ceyr.26.3.211.14902.
To determine if murine cytomegalovirus (MCMV)-infected eyes of mice with murine acquired immunodeficiency syndrome (MAIDS) that are destined to develop MCMV retinitis display elevated intraocular levels of interleukin-4 (IL-4) mRNA when compared with uninfected eyes of mice with MAIDS and unmanipulated, uninfected, eyes of normal healthy mice.
Groups of C57BL/6 mice with MAIDS and normal C57BL/6 mice were infected uniocularly with MCMV by subretinal MCMV injection. IL-4 levels in individual spleens collected five days later from groups of MAIDS mice and normal mice were assessed by quantitative ELISA. MCMV-infected eyes and uninfected contralateral eyes from another group of mice with MAIDS were also collected at five days postinfection and individually subjected to competitive RT-PCR assay and real-time RT-PCR assay for detection and quantification of IL-4 mRNA. Unmanipulated eyes from normal C57BL/6 mice served as controls.
IL-4 mRNA was detected at a level of 9.7 +/- 3.4 pg mRNA per 1000 ng total RNA in 100% of MCMV-infected eyes of mice with MAIDS by competitive RT-PCR assay, but could not be detected in any of the uninfected eyes of MAIDS mice. In comparison, the more sensitive technique of real-time RT-PCR assay detected copies of IL-4 cDNA in both MCMV-infected eyes and uninfected eyes of MAIDS mice. MCMV-infected eyes showed a 16-fold increase in the number of IL-4 cDNA copies when compared with uninfected eyes. Neither technique detected IL-4 mRNA in unmanipulated eyes of normal mice. As expected, spleen cells from mice with MAIDS expressed significantly greater levels of IL-4 when compared with spleen cells from normal mice.
MCMV-infected mice with MAIDS exhibited an expected preferential activation of Th2 cells as determined by increased levels of IL-4 in spleen cells when compared with spleen cells of normal mice. MCMV-infected eyes destined to develop retinitis during MAIDS also showed increased levels of detectable IL-4 mRNA when compared with uninfected eyes of mice with MAIDS. It is therefore possible that IL-4 synthesis by Th2 CD4+ T cells during retrovirus-induced immunosuppression serves to inhibit the perforin cytotoxic pathway that subsequently allows susceptibility to MCMV retinitis during MAIDS.
确定与患获得性免疫缺陷综合征（MAIDS）的未感染小鼠的眼睛以及正常健康未处理的未感染小鼠的眼睛相比，注定会发生巨细胞病毒性视网膜炎的患MAIDS小鼠的感染巨细胞病毒（MCMV）的眼睛中白细胞介素-4（IL-4）mRNA的眼内水平是否升高。
通过视网膜下注射MCMV，将患MAIDS的C57BL/6小鼠组和正常C57BL/6小鼠单眼感染MCMV。五天后从患MAIDS小鼠组和正常小鼠组收集的单个脾脏中的IL-4水平通过定量ELISA进行评估。在感染后五天，还收集了另一组患MAIDS小鼠的感染MCMV的眼睛和未感染的对侧眼睛，并分别进行竞争性逆转录聚合酶链反应（RT-PCR）测定和实时RT-PCR测定，以检测和定量IL-4 mRNA。正常C57BL/6小鼠未处理的眼睛用作对照。
通过竞争性RT-PCR测定，在100%患MAIDS小鼠的感染MCMV的眼睛中检测到IL-4 mRNA，水平为每1000 ng总RNA 9.7±3.4 pg mRNA，但在患MAIDS小鼠的任何未感染眼睛中均未检测到。相比之下，更灵敏的实时RT-PCR测定技术在患MAIDS小鼠的感染MCMV的眼睛和未感染的眼睛中均检测到IL-4 cDNA拷贝。与未感染的眼睛相比，感染MCMV的眼睛中IL-4 cDNA拷贝数增加了l6倍。两种技术在正常小鼠未处理的眼睛中均未检测到IL-4 mRNA。正如预期的那样，与正常小鼠的脾细胞相比，患MAIDS小鼠的脾细胞表达的IL-4水平明显更高。
与正常小鼠的脾细胞相比，患MAIDS且感染MCMV的小鼠表现出预期的Th2细胞优先激活，这通过脾细胞中IL-4水平升高来确定。在MAIDS期间注定会发生视网膜炎的感染MCMV的眼睛与患MAIDS小鼠的未感染眼睛相比，也显示出可检测到的IL-4 mRNA水平升高。因此，在逆转录病毒诱导的免疫抑制期间，Th2 CD4+ T细胞合成IL-4可能会抑制穿孔素细胞毒性途径，从而导致在MAIDS期间易患巨细胞病毒性视网膜炎。
