Antiviral activity of a thymic factor in experimental viral infections. I. Thymic hormonal effect on survival, interferon production and NK cell activity in Mengo virus-infected mice.
A partially purified thymic factor, thymostimulin (TS), significantly increased the survival rate of adult, immune-intact mice infected with the neurotropic Mengo virus. TS treatment was begun after virus inoculation by daily i.p. injections. In untreated C57BL/6 mice, LD50 was reached with 1 X 10(4) PFU, but 10-fold more virus (i.e., 1 X 10(5) PFU) was needed to reach LD50 in TS-treated animals. TS effect on survival, though, could be observed with several virus doses (1 X 10(3) to 1 X 10(6) PFU) (p less than 0.001). A significant effect on survival was also observed with outbred ICR mice (p less than 0.005). Serum interferon (IFN) levels in the Mengo virus-infected mice were relatively low (average peak 300 U/ml), but were significantly increased (two- to ninefold) in the TS-treated mice. Peak serum levels were reached earlier in TS than in control animals (24 hr and 72 hr, respectively). Both acid-labile and acid-stable type I IFN production were augmented by TS in the Mengo virus-infected mice. Natural killer activity was also enhanced by TS, in particular on the second day after virus inoculation. In addition, MP-virus was used as a second, unrelated virus challenge. This virus caused a nonlethal infection, with relatively high levels of serum IFN (average peak 10,000 U/ml). TS increased IFN levels (two- to eight-fold) also in this challenge system. In conclusion, TS causes a nonspecific enhancement of endogenous production of IFN and has a significant effect on the survival of lethally infected mice. The data indicate a potential application of thymic factors for the treatment of viral infections.
D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology*; D004660:Encephalitis / Q000188:drug therapy / Q000276:immunology / Q000401:mortality; D004769:Enterovirus Infections / Q000188:drug therapy / Q000276:immunology* / Q000401:mortality; D007372:Interferons / Q000096:biosynthesis*; D007694:Killer Cells, Natural / Q000276:immunology*; D008297:Male; D008574:Mengovirus / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D008813:Mice, Inbred ICR; D013154:Spleen / Q000276:immunology / Q000378:metabolism; D013949:Thymus Extracts / Q000494:pharmacology*
D000998:Antiviral Agents; D013949:Thymus Extracts; C031407:thymostimulin; D007372:Interferons