Modulation by cyclosporin A of murine natural resistance against herpes simplex virus infection. I. Interference with the susceptibility to herpes simplex virus infection

Effect of cyclosporin A on an experimental chronic viral infection of the central nervous system

The effects of cyclosporin A (CsA) on neuropathological lesions induced by a chronic viral infection have been tested in the experimental model of the mouse hepatitis virus 3 (MHV3) infection. Daily injections of CsA (50 mg/kg) inhibited the expression of the MHV3-induced ependymitis, meningitis, hydrocephalus and vasculitis. The effect was preserved even if CsA treatment was initiated 15 days after virus infection but was lost if CsA treatment was given later on or for a shorter period of time. Viral titers in brains of chronically infected mice were not affected by CsA treatment. During the first week following MHV3 infection, CsA treatment increased both the percentage of acute death (31 vs. 10%) and the viral titers in brain and liver of infected mice. In this model, the timing of CsA treatment appeared critical for the balance between its beneficial effect on CNS lesions and the risk of increased acute mortality.

Effects of 7,12-dimethylbenz[a]anthracene, benzo[a]pyrene and cyclosporin A on murine cytomegalovirus infection: studies of resistance mechanisms

Susceptibility to murine cytomegalovirus (MCMV) was enhanced by treating B6C3F1 and CD-1 mice subcutaneously with 100 mg 7,12-dimethyl-benz[a]anthracene (DMBA)/kg fractionated over a 2 week period prior to sub-lethal infection. Virus-augmented natural killer cell (NKC) activity was depressed in B6C3F1 mice treated with 100 mg DMBA/kg, while serum interferon (IFN) levels were unaffected. Treatment with 50 mg DMBA/kg had no effect on susceptibility to virus or virus-augmented NKC activity. Susceptibility to MCMV was not affected by treating mice with 400 mg benzo[a]pyrene (B[a]P)/kg using the same exposure regimen. Virus-augmented NKC activity was suppressed in B[a]P-treated mice, but the magnitude of the suppression (18%) was much less than that for DMBA-treated mice (39%). Susceptibility to MCMV, virus-augmented NKC and IFN induction were not affected in mice treated intraperitoneally with 50 mg cyclosporin A (CSA)/kg/day for 5 days and infected on the 5th day of treatment. In contrast, enhanced susceptibility to MCMV and depressed NKC activity were observed in mice treated by the same exposure regimen on days 1-5 post infection. Susceptibility was not affected by CSA given on days 5-9 post infection. The data are useful not only because they show that DMBA and appropriately-timed CSA treatments suppress virus augmented NKC and enhance susceptibility to MCMV, but also because they help to define the relative importance of certain immune responses in defending against the infection, thus improving the usefulness of MCMV as a host resistance model for immunotoxicity testing. The data suggest that chemicals which depress NKC are likely to enhance susceptibility to MCMV, and conversely that effects on NKC should be suspected when chemical exposure enhances susceptibility to MCMV.

Effects of cyclosporin A on humoral immune response and resistance against vesicular stomatitis virus in mice

The effect of cyclosporin A (CS-A) on the antiviral humoral response was studied by using vesicular stomatitis virus (VSV); VSV provided the opportunity to simultaneously assess both T-independent and T-dependent antibody responses. The T-independent anti-VSV immunoglobulin M (IgM) response was virtually unaffected, whereas the T-dependent primary anti-VSV IgG response was suppressed by CS-A; in contrast, the secondary IgG response was highly resistant to CS-A. Moreover, once the switch from IgM to IgG had occurred, the primary response also became refractory to suppression by CS-A. We concluded that the effect of CS-A on the primary anti-VSV antibody response was mediated via impairment of a T-dependent mechanism; in contrast, memory T cells or memory B cells or both were quite resistant to the suppressive effects of CS-A. CS-A treatment rendered mice highly susceptible to VSV infection; under CS-A treatment, mortality was 100% after infection via footpads, whereas immunocompetent mice survived. Since CS-A does not impair induction of early T-independent anti-VSV IgM neutralizing antibodies, this high mortality in CS-A treated mice illustrates the crucial role of CS-A-sensitive cells in resistance against VSV.

Mechanism of recovery from acute virus infection. II. Effect of treatment of mice with cyclosporin A on their ability to eliminate the lymphocytic choriomeningitis virus

Illness and death of mice infected by intracerebral inoculation with lymphocytic choriomeningitis virus are pathologic immune phenomena, and mice thus infected were protected when immunosuppressed with cyclosporin A (CSA), although the virus multiplied extensively in all major organs. Concentrations remained high as long as the drug was administered but declined when the treatment was discontinued; also, cytotoxic T lymphocytes appeared. Virus elimination was slower and cytotoxic T cell activity lower than in mice not previously treated with CSA.

In vivo effects of cyclosporine on influenza A virus-infected mice

Cyclosporine (cyclosporin A, CsA) administered to mice substantially affects their immune response to an influenza A virus infection. If treated with CsA for 21 days, the mouse lungs contain high titers of virus which are cleared more slowly than in controls. Indicators of pathological damage--lung weight, extent of consolidation, fine morphology, and the extent of infiltration of dividing cells into the lung--showed that administration of CsA greatly decreased the level of inflammation. The production of hemagglutination-inhibiting (HI) antibody was delayed but reached almost control levels and NK cell activity in the lung was also comparable to control levels. In contrast, a delayed-type hypersensitivity (DTH) response to the virus could not be elicited in the CsA-treated, infected mice at 6 or 12 days after infection. Cytotoxic-T-cell (Tc-cell) activity was present in the lungs of such mice though its appearance was delayed and the activity recovered was less than that of the control infected mice. If administered with a dose of virus lethal for normal mice. CSA-treated mice survived, probably due to the greatly reduced level of immunopathological damage in the infected lung.

Cyclosporine: immunology, toxicity and pharmacology in experimental animals

Cyclosporine (CsA) is the first of a new order of pharmacological immune suppressants and represents a significant advance in the clinical control of graft rejection. In laboratory animals, its capacity to prolong allograft survival has been well documented, including reports of indefinite donor-specific immunological tolerance after shortterm CsA treatment. There is also evidence that CsA can inhibit the onset or progress of a variety of experimental autoimmune diseases. Underlying these properties of the drug is its capacity to selectively interfere with T helper cell activation and lymphokine production, although some direct effects on B cells have also been reported. In addition, sparing of suppressor cells may in part explain the mode of action of CsA which, at the molecular level, is not understood. CsA-induced nephrotoxicity in the rat has been extensively studied and is characterized by reversible proximal tubular cell damage. This problem may be aggravated by concomitant administration of other potentially nephrotoxic drugs, such as gentamicin, or by therapeutic agents which interfere with the metabolism of CsA. CsA is metabolized in the liver and excreted in the bile. Although the pathway of hepatic metabolism of CsA has not been precisely elucidated, animal studies suggest that agents capable of inducing metabolism of the drug CsA could be used to alleviate its nephrotoxic properties.