Effect of recombinant HSV-1 expressing IL-4 or IFN-γ on macrophage responses in vitro and in vivo

Abstract

Purpose : We previously reported that altering macrophage polarization toward M2 by CSF-1 injection reduced both primary and latent infection in HSV-1 ocularly infected mice. In this study, we tested the hypothesis that pushing the immune response towards M2 and/or T_H2 by IL-4 is responsible for better protection against ocular HSV-1 infection, as compared with the induction of M1 and/or T_H1 by IFN-γ. These hypotheses were tested by using recombinant HSV-1 viruses expressing either IL-4 or IFN-γ.

Methods : Female C57BL/6 mice were ocularly infected with 2X10⁵ pfu/eye of HSV-1 recombinant viruses expressing IL-4 or IFN-γ or control viruses. Following ocular infection with each virus, primary virus replication in the eye, gC expression, survival, corneal scarring (CS), latency-reactivation on day 28 post infection (PI), and expression of CD4, CD8, PD1, IL-4 and IFN-γ transcripts in the corneas and TG on day 28 PI were determined by TaqMan qRT-PCR and FACS. Some of the infected mice were depleted of their macrophages by Cl₂MDP injection.

Results : Primary infection in the eye was significantly reduced in HSV-IL-4 infected mice on day 3 PI compared to mice infected with either HSV-IFN-γ or control viruses. CS was higher in HSV-IFN-γ infected mice compared with HSV-IL-4 or control viruses. Latent infection in TG was reduced in both HSV-IL-4 and HSV-IFN-γ groups compared with the control virus and the level of latency in HSV-IL-4 infected mice was significantly lower than HSV-IFN-γ infected mice. In addition, reactivation was also lower in HSV-IL-4 infected mice as compared with HSV-IFN-γ and control infected mice. The protective effect on primary and latent infection in the HSV-IL-4 group disappeared in macrophage-depleted mice.

Conclusions : Our findings demonstrate that: 1) Both HSV-IL-4 and HSV-IFN-γ viruses shifted macrophage polarization toward M2 and M1, respectively; 2) HSV-IL-4 was more effective in providing protection against both primary and latent infection and reactivation compared to HSV-IFN-γ or dLAT2903 virus; and 3) Macrophage depletion eliminated the protective effect of HSV-IL-4 on both primary and latent infection compared with other groups. Our results suggest that shifting the innate macrophage immune responses toward M2 and away from M1 would provide a better protection against both primary and latent infection as well as reactivation and eye disease.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.