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R.D. Dix, D.G. Espinosa–Heidmann, S. Pereira–Simon, D.M. Miller, S.W. Cousins; Severe Experimental Choroidal Neovascularization During Chronic Cytomegalovirus Infection Is Not Associated With Productive Virus Infection Of The Choroid . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4158.
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© ARVO (1962-2015); The Authors (2016-present)
We have reported previously that chronic cytomegalovirus (CMV) infection may serve as a novel risk cofactor for evolution of wet age–related macular degeneration (AMD). Firstly, patients with wet AMD exhibit a higher frequency of elevated CMV–specific serum IgG titers when compared with patients with dry AMD. Secondly, chronic infection of mice with murine CMV (MCMV) results in more severe experimental choroidal neovascularization (CNV). To better understand the mechanism by which MCMV contributes to increased severity of experimental CNV, studies were performed to test the hypothesis that CNV is associated with direct productive virus infection of choroid tissues.
Groups of C57BL/6 mice were injected intraperitoneally with UV–inactivated MCMV or a non–lethal dose of infectious MCMV. At various times after virus injection (6 days, 6 weeks, and 12 weeks), CNV was induced by laser treatment and CNV severity determined 4 weeks later by choroidal flatmount analysis. Additionally, pooled choroid tissues as well as systemic tissues and cell populations were collected for evidence of MCMV–specific ie1 and gH gene sequences using PCR assay.
As expected, most severe CNV developed in mice with chronic 12–week MCMV infection. Salivary gland, spleen, and splenic macrophages collected at times of acute or chronic MCMV infection provided positive PCR assay signals for MCMV–specific DNA indicating extensive systemic virus infection. Purified CD34+ cells of bone marrow origin collected from mice with chronic MCMV infection were also positive for MCMV DNA. However, whereas pooled choroid tissues from eyes of acutely infected mice showed virus infection, MCMV–specific DNA was not detected in pooled choroid tissues from eyes of chronically infected animals. This was confirmed by our inability to recover infectious virus from whole eyes of chronically infected animals using standard plaque assay.
No evidence was found for direct MCMV infection of ocular tissues at time of chronic virus infection when CNV was most severe. We conclude that MCMV replication within choroid tissues does not contribute directly to increased CNV severity. More likely, chronic MCMV infection promotes CNV indirectly by pro–inflammatory activation of circulating macrophages.
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