EFFECT OF BOVINE RESPIRATORY SYNCYTIAL VIRUS-INFECTION ON HYPERSENSITIVITY TO INHALED MICROPOLYSPORA-FAENI

Respiratory syncytial Virus causes mild-to-severe respiratory disease in human infants and young children; a closely related bovine respirat ory syncytial virus causes a similar disease pattern in carves. Increa sed disease severity in atopic children suggests that allergic reactiv ity may enhance the severity of RSV-induced disease. To examine the as sociation between bovine respiratory syncytial virus (BRSV) infection and allergic reactivity two groups of carves were exposed to aerosoliz ed Micropolyspora faeni (Mf) during an experimental BRSV infection. On e group exposed to Mf concurrent with BRSV was challenge-exposed to Mf while infected a second time with BRSV, while the other similarly sen sitized and infected group was mock challenged. A control group was ex posed only to Mf aerosol and another control group was infected with v irus but not exposed to Mf aerosol. Parameters examined included: clin ical signs, Mf-specific IgG and IgE, BRSV-specific antibody and IgE, l eukotrienes C-4 and B-4 prostaglandins E(2), F-2 alpha and D-2, and lu ng pathology. While the initial BRSV infection failed to enhance sensi tization to inhaled Mf, a second BRSV infection excerbated cinical sig ns resulting from Mf aerosol. Consideration of eicosanoid and antibody profiles together with clinical signs suggests that mechanisms of bot h type I and type III hypersensitivity were operative during Mf challe nge of sensitized carves.