Latent Ocular Murine Cytomegalovirus (MCMV) exacerbates the development of Choroidal Neovascularization (CNV) in VEGF-A^hyper mice

Abstract

Purpose : Human cytomegalovirus (HCMV) promotes angiogenesis and this process contributes to many vascular diseases. However, it remains unclear if this virus plays any role in CNV. The purpose of this study was to investigate if latent ocular MCMV exacerbates the development of CNV in VEGF-A^hyper mice following systemic neonatal infection.

Methods : MCMV (50 pfu per mouse) or medium as control was peritoneally injected into VEGF-A^hyper or wild type (WT) 129 mice at <3 days after birth. Mice were sacrificed at intervals post infection (p.i.), and eyes and extraocular tissues were collected for analysis by plaque assay, PCR to detect viral gene expression, and for the presence of MCMV early antigen (EA). At 6 months p.i., some eyes were analyzed by fundus imaging and fluorescence angiography, by H&E staining, by real time RT-PCR for MCMV gene transcripts and by ELISA to determine protein levels of VEGF-A and other inflammatory factors.

Results : At day 14 p.i., replicating virus was detected in the lungs, salivary glands and eyes of infected mice. MCMV EA was observed in the choroid in all eyes from both VEGF-A^hyper and WT mice. No replicating virus was detected in the eyes and extra ocular tissues at 6 months p.i., although virus DNA was still detected in all eyes and extraocular tissues from both VEGF-A^hyper and WT mice. Expression of MCMV IE1 mRNA was detected only in latently infected eyes of VEGF-A^hyper mice (3/7), but not in eyes of WT mice (0/9). CNV lesions were observed in only 3/18 eyes from non-infected VEGF-A^hyper mice, whereas lesions were observed in 14 of 18 eyes from MCMV latently infected VEGF-A^hyper mice. MCMV-infected VEGF-A^hyper mice also exhibited an increased average lesion size and severity while CNV lesions were not observed in any eyes from infected or non-infected WT mice. Protein levels of CCL5, TGF-β1, IL6 and VEGF-A were all significantly higher in MCMV-infected VEGF-A^hyper mice, compared to non infected VEGF-A^hyper mice and infected or non-infected WT mice.

Conclusions : MCMV disseminates to and remains latent in the eyes following systemic infection of neonatal VEGF-A^hyper mice or WT 129 mice. Prior overexpression of VEGF-A induces activation of MCMV genes which in turn, promotes the production of inflammatory/angiogenetic factors and the development of CNV in latently infected VEGF-A^hyper mice.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.