Enhancement of Th2 responses to replicative herpes simplex virus type 1 vectors by immunomodulative chemotherapy

Replicating, neuroattenuated γ134.5-deleted herpes simplex virus (HSV)-vectors are tools for experimental therapy of gliomas and autoimmune diseases. Immunomodulative treatment with Linomide (quinoline-3-carboxamide) has earlier been shown to facilitate some virus infections and reduce autoimmunity. Now we aimed at elucidating the safety of immunomodulatory therapy during infection of mice with HSV vectors. We focused on immunological and virological changes in the nervous system. BALB/c mice were infected intranasally with the HSV-1 recombinant viruses R3616, R3659 and R8306 (with mouse IL-4 transgene) and either treated with Linomide or left untreated as control groups. Treatment with Linomide was started 7 days before infection. Virological analysis consisted of viral culture and PCR for HSV DNA. Cytokine responses were studied with quantitative RT-PCR and EIA. Immunomodulatory treatment did not change the clinical course of infections. The expression of IL-4 and IL-10 in brains increased in Linomide-treated mice, particularly in infection with R8306. The expression of IL-23p19 was decreased in brains in Linomide-treated, vector-infected mice, in comparison with nontreated but virus-infected animals. Immunomodulatory treatment did not increase the viral load in brains in any of the mouse groups infected with R3616, R3659 or R8306. Immunomodulative treatment with Linomide did not compromise the safety of replicating HSV-vectors, not even the one with IL-4 transgene, suggesting that combination of immunomodulation with virotherapy may be beneficial in the treatment of certain diseases of the central nervous system. Further investigations are needed to elucidate the effects of immunomodulatory therapy in order to improve vector survival and efficacy of gene therapy.