Biologic response modifiers as antivirals in immunosuppressed hosts

Protective effect of adenylate deaminase (from Penicillium lanoso-viride) against acute infections in mice

We examined the effects of the immunomodulator-adenylate deaminase (E.C. 3.5.4.6) from Penicillium lanoso-viride on experimental mice infections. Prophylactic intraperitoneal administration of adenylate deaminase (ADA) increased survival time and numbers of survivors after infection with Salmonella typhimurium, Pseudomonas aeruginosa and influenza A (H3N2) virus. Protection against influenza virus after intranasal ADA application was also observed. The influence of ADA was time and dose dependent. The most pronounced protection was obtained by administration of 3 U ADA/mice 24 h prior to infection. ADA had no antibiotic effect against these bacterial strains. Protective effects of ADA were studied in immunosuppressed mice under different regimes of treatment including cyclosporin A and trypan blue. The results indicated, that the protective effect of ADA is of a complex nature and probably depends on both T-cell and macrophage components.

Biologic response modifiers as antivirals in immunosuppressed hosts

A wide variety of immunomodulators/biologic response modifiers (BRM) have been demonstrated to provide broad spectrum antiviral activity against both RNA and DNA viruses in several animal species. Dramatic decreases in mortality, reduced virus titers in tissues, and reduced histopathology can be produced. The antivirally effective agents include microbially derived materials, polyanions, cytokines, and chemically diverse small molecular weight chemicals. Antiviral efficacy with BRM treatment has been shown in numerous kinds of immunosuppression, emphasizing the potential for BRM treatment in immunocompromised patients. The greatest protective effects are observed with prophylactic or early therapeutic treatment. BRMs act indirectly, most likely by activating cells and/or inducing antiviral mediators early in the course of viral pathogenesis. In general, viral specific immune responses in BRM-treated and infected mice are absent or similar to those in untreated mice. Because BRMs are pleiotropic in their immunomodulatory effects, it has been difficult to establish whether one cell type or mediator is critical for the broad spectrum antiviral activity. Interferon appears to be critical for some small molecular weight synthetic compounds, but does not appear to explain all the antiviral activity of certain large molecular weight polyanions. Whether there is a unified antiviral mechanism among different BRMs remains to be determined.