Roles of Type 1, 2, and 3 Innate Lymphoid Cells in Herpes Simplex Virus 1 Infection In Vitro and In Vivo.

Innate lymphoid cells (ILCs) play important roles in host defense and inflammation. They are classified into three distinct groups based on their cytokine and chemokine secretion patterns and transcriptome profiles. Here, we show that ILCs isolated from mice can be infected with herpes simplex virus 1 (HSV-1) but that subsequent replication of the virus is compromised. After infection, type 2 ILCs expressed significantly higher levels of granulocyte colony-stimulating factor (G-CSF), interleukin 1α (IL-1α), IL-6, IL-9, RANTES, tumor necrosis factor alpha (TNF-α), CXCL1, CXCL2, CXCL10, CCL3, and CCL4 than infected type 1 or type 3 ILCs. Transcriptome-sequencing (RNA-seq) analysis of the ILCs 24 h after HSV-1 infection revealed that 77 herpesvirus genes were detected in the infected type 3 ILCs, whereas only 11 herpesvirus genes were detected in infected type 1 ILCs and 27 in infected type 2 ILCs. Compared with uninfected cells, significant upregulation of over 4,000 genes was seen in the HSV-1-infected type 3 ILCs, whereas 414 were upregulated in the infected type 1 ILCs and 128 in the infected type 2 ILCs. In contrast, in all three cell types, only a limited number of genes were significantly downregulated. Type 1, type 2, and type 3 ILC-deficient mice were used to gain insights into the effects of the ILCs on the outcome of ocular HSV-1 infection. No significant differences were found on comparison with similarly infected wild-type mice or on comparison of the three strains of deficient mice in terms of virus replication in the eyes, levels of corneal scarring, latency-reactivation in the trigeminal ganglia, or T-cell exhaustion. Although there were no significant differences in the survival rates of infected ILC-deficient mice and wild-type mice, there was significantly reduced survival of the infected type 1 or type 3 ILC-deficient mice compared with type 2 ILC-deficient mice. Adoptive transfer of wild-type T cells did not alter survival or any other parameters tested in the infected mice. Our results indicate that type 1, 2, and 3 ILCs respond differently to HSV-1 infection in vitro and that the absence of type 1 or type 3, but not type 2, ILCs affects the survival of ocularly infected mice.IMPORTANCE In this study, we investigated for the first time what roles, if any, innate lymphoid cells (ILCs) play in HSV-1 infection. Analysis of isolated ILCs in vitro revealed that all three subtypes could be infected with HSV-1 but that they were resistant to replication. The expression profiles of HSV-1-induced cytokines/chemokines and cellular and viral genes differed among the infected type 1, 2, and 3 ILCs in vitro While ILCs play no role or a redundant role in the outcomes of latency-reactivation in infected mice, absence of type 1 and type 3, but not type 2, ILCs affects the survival of infected mice.