The importance of IFNα2A (Roferon-A) in HSV-1 latency and T cell exhaustion in ocularly infected mice

IFNβ absence compensates for LAT functions in latency reactivation and T cell exhaustion

Type I interferons (IFNs) generate strong antiviral immunity following viral infection in mice and humans. These type I IFNs are encoded by at least 14 IFNα genes and a single IFNβ gene. We showed that the absence of one of the IFNα genes (IFNα2A-/-) affected latency levels in herpes simplex virus type 1 (HSV-1) ocularly infected mice but not in infected control mice, and the absence of IFNα2A did not affect viral reactivation in ocularly infected mice. Since the role of IFNβ in HSV-1 latency reactivation and the potential effect of latency-associated transcript (LAT) on IFNβ activity is not known, we ocularly infected IFNβ-/- mice with different doses of LAT-plus [LAT(+)] and LAT-minus [LAT(-)] viruses. Wild-type (WT) control mice and IFNβ-/- mice were infected similarly. Virus titers in the eye, viral and cellular transcripts in the eye and trigeminal ganglia (TG) of infected mice on days 3 and 5 post-infection, eye disease, survival, latency-reactivation levels, and T cell exhaustion were measured in latently infected mice. Virus replication and viral and cellular transcripts in the eye of infected IFNβ-/- mice were similar to those in WT mice, while eye disease and survival in IFNβ-/- mice differed significantly from WT mice. WT mice infected with LAT(-) virus showed reduced latency, slower reactivation, and less T cell exhaustion than mice infected with LAT(+) virus. However, using different doses of each virus, latency levels, time of reactivation, and T cell exhaustion were similar between LAT(+) and LAT(-) viruses. These results suggest that the absence of IFNβ expression compensates for the function of LAT with regard to levels of latency, T cell exhaustion, and reactivation but does not affect viral and cellular transcripts during primary infection.IMPORTANCEInterferon β (IFNβ) is a type I interferon that plays an important role in controlling primary herpes simplex virus type 1 (HSV-1) infection. To evaluate the importance of IFNβ on HSV-1 latency reactivation and its relationship to LAT, we infected IFNβ-/- mice with LAT(+) and LAT(-) viruses. In the absence of IFNβ, latency levels in mice infected with LAT(-) virus were similar to those of mice infected with LAT(+) virus. The absence of IFNβ also reduced the time of reactivation in mice infected with LAT(-) virus to that of LAT(+) virus. Our results show a strong correlation between the functions of LAT and IFNβ during latent but not primary stages of HSV-1 infection.

Immunological Control of Herpes Simplex Virus Type 1 Infection: A Non-Thermal Plasma-Based Approach

Herpes simplex virus type 1 (HSV-1) causes a lifelong infection due to latency established in the trigeminal ganglia, which is the source of recurrent outbreaks of cold sores. The lifelong persistence of HSV-1 is further facilitated by the lack of cure strategies, unsuccessful vaccine development, and the inability of the host immune system to clear HSV-1. Despite the inefficiencies of the immune system, the course of HSV-1 infection remains under strict immunological control. Specifically, HSV-1 is controlled by a CD8+ T cell response that is cytotoxic to HSV-1-infected cells, restricts acute infection, and uses noncytolytic mechanisms to suppress reactivation in the TG. When this CD8+ T cell response is disrupted, reactivation of latent HSV-1 occurs. With antiviral therapies unable to cure HSV-1 and prophylactic vaccine strategies failing to stimulate a protective response, we propose non-thermal plasma (NTP) as a potential therapy effective against recurrent HSV-1 infection. We have demonstrated that NTP, when applied directly to HSV-1-infected cells, has antiviral effects and stimulates cellular stress and immunomodulatory responses. We further propose that the direct effects of NTP will lead to long-lasting indirect effects such as reduced viral seeding into the TG and enhanced HSV-1-specific CD8+ T cell responses that exert greater immune control over HSV-1 infection.