CYTOKINE AND CHEMOKINE PRODUCTION IN HSV-1 LATENTLY INFECTED TRIGEMINAL GANGLION-CELL CULTURES - EFFECTS OF HYPERTHERMIC STRESS

The establishment of a primary trigeminal ganglion (TG) cell culture l atently infected with herpes simplex virus type 1 (HSV-1) has been use ful in studying stress-induced reactivation of the latent virus. Howev er, the immune profile of this culture system prior to and after stres s has never been established. In the present manuscript, cytokine and chemokine production were measured in primary cultures of TG cells obt ained from uninfected and HSV-1 latently infected mice. Supernates fro m TG cell cultures contained detectable interleukin (IL)-6 but not IL- 1 beta, IL-2, IL-10, interferon (IFN)-gamma or tumor necrosis factor ( TNF)-alpha as determined by ELISA. The basal level of IL-6 in uninfect ed TG cell cultures was 20.5 +/- 2.3 ng/ml, whereas latently infected TG cells produced significantly less IL-6 (12.1 +/- 1.9 ng/ml). Supern ates from TG cell cultures also contained detectable levels of C-10, M CP-1 and eotaxin but little to no MIP-1 alpha, MLP-1 beta, or MIP-2. W hile there were no differences in the basal level of MCP-1 and eotaxin in TG cell cultures from HSV-1-infected and uninfected mice, C10 leve ls were significantly higher in TG cultures originating from infected mice compared to uninfected ones (5.86 +/- 0.61 ng/ml compared to 1.18 +/- 0.16 ng/ml). Hyperthermic stress (43 degrees C, 180 min), which i nduces reactivation of latent HSV-1 from TG cell cultures, significant ly reduced IL-6 and C-10 levels from both uninfected and latently infe cted TG cell cultures. However, there was no correlation between cytok ine/chemokine levels and HSV-1 reactivation. Immunofluorescent studies showed TG cell cultures contained 10% MAC-3(+) staining cells (macrop hage specific) but no dendritic cells. By comparison, cells from fresh ly isolated TG contained 6% positive dendritic cells but < 1% MAC-3(+) cells. Both in vivo and in vitro TG consisted of a low percentage of CD3(+) and CD8(+) cells. Hyperthermic stress (43 degrees C for 3 h) el iminated the lymphocyte population as determined by RT-PCR. Whereas no spontaneous reactivation has been reported in mice, spontaneous react ivation occurred in 4.5% (10/220) of TG cell cultures surveyed over a 20 day period. Collectively, the dichotomy between HSV-1 replication a nd reactivation comparing the in vitro and in vivo HSV-1 latency model s may reside, in part, to the differences in the levels of cytokines, chemokines and immune cell populations within the microenvironment of the in vitro and in vivo TG. (C) 1998 Elsevier Science B.V. All rights reserved.