Abstract
Purpose :
Herpes Simplex Virus-1 (HSV-1) is the leading cause of infectious blindness in developed countries. Both mice and humans develop similar pathology after intracorneal (i.c) HSV-1 infection, making mice a useful model to understand underlying mechanisms of disease. Mice lacking γδ T cells exhibit reduced Interleukin 17A (IL-17A), increased virus titers and develop lethal encephalitis after i.c. infection. To understand the diversity of the γδ T cell response required for immunoprotection, we analyzed whether the T cell receptor (TCR) Vγ repertoire changed after viral infection. Further, we investigated whether a particular subset of γδ T cells was responsible for IL-17A production following i.c. HSV-1 infection.
Methods :
C57Bl/6 mice received 1x106 PFUs HSV-1 injected into the stroma of the cornea. One to two days post infection (P.I.) corneas were excised and digested in LiberaseTM. The cells were immunostained for surface markers and for intracellular cytokines, and analyzed using flow cytometry. In separate experiments, RNA was isolated from whole corneas, and reverse transcriptase (RT)-PCR was used to identify particular TCR Vγ usage. ELISAs were used to measure the levels of secreted IL-1α and CCL20.
Results :
By 48 hours P.I. there is a significant increase in the number of CCR6+ IL-17A+ γδ T cells compared to uninfected corneas (n=3-5, P=0.008). TCR Vγ1 was detected in both uninfected and infected corneas, and were also found to be predominantly CCR6 negative. TCR Vγ2 (P=0.051) and Vγ4 (P=0.004) subsets were readily observed in infected corneas. To determine whether IL-1α and IL-23 are capable of mediating IL-17A production in the cornea, as shown in other tissues, we performed flow cytometric analysis: CCR6+ γδ T cells expressed IL-1R1 and IL-23R. Moreover, CCL20, the ligand for CCR6, and IL-1α, a signal for IL-17A production, were both detected by ELISA 15 hours P.I.
Conclusions :
Two major subsets of γδ T cells (based on CCR6 expression) participate in the response to i.c. HSV-1 infection. This study supports the concept that CCR6+ γδ T cells are responsible for IL-17A production via recruitment by CCL20 and signaling by IL-1α and IL-23.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.