Depression of contact hypersensitivity to oxazolone in mice exposed to Newcastle disease virus.

The effect of Newcastle disease virus (NDV) on delayed hypersensitivity to oxazolone in CBA mice was studied. There was a significant impairment of the ability of mice to develop cutaneous hypersensitivity shortly after injection of the virus. The effect was evident when NDV was administered up to 2 days before or within 24 h after sensitization, suggesting that NDV interferes with the process of sensitization. The degree of depression was related to the dose of virus inoculated. NDV inactivated by UV irradiation or heat did not depress contact sensitivity to oxazolone. These data are considered to support the hypothesis that the depression is mediated by a direct interaction between lymphocytes and NDV.