Early immune responses in experimental maedi.

Ten Finnish sheep were infected with maedi virus either by the respiratory tract or by intracerebral injection. After respiratory tract infection, virus specific lymphocyte stimulation was detected between two and seven weeks and complement fixing antibodies between seven weeks and three months. After intracerebral injection, lymphocyte stimulation was detected between five and nine weeks and complement fixing antibodies between nine weeks and four months. Neutralising antibodies were not found in six sheep killed within four months but were found in two of four sheep four and five months after infection. Virus was recovered with varying frequency from the peripheral blood leucocytes and tissues of all the sheep and also from the cerebrospinal fluid of intracerebrally inoculated sheep. The histological changes in sheep inoculated via the respiratory tract were comparable to known early maedi lesions; no changes were found in the central nervous system (CNS). The intracerebrallly inoculated sheep showed very mild periventricular inflammation in the CNS.