Utveckling och applicering av en aviditets-ELISA för bovint respiratoriskt syncytialt virus

Sammanfattning: Bovine Respiratory Syncytial Virus (BRSV) is a common cause of respiratory disease among young cattle. The virus causes severe losses; the herd mortality rate can sometimes be as high as 20 %. In this study the avidity (i.e the antigen binding force) of BRSV specific antibodies was measured to see if there was a difference between antibodies produced during an acute phase of infection and antibodies produced by earlier infected animals. A commercially available ELISA-testkit against BRSV-specific antibodies was used and an incubation step with 6M urea was added. The effect of the urea is that it breaks the weak bonds between antibodies and antigen while the stronger bonds remain intact. Four different groups of animals were included in this study; seven calves that were naturally infected, three acutely infected calves with known time of infection, five cows that were seropositive during several years and four experimentally infected calves that had been a part of a vaccine trial. The results of this study showed that antibodies produced during the acute phase of an infection had a low avidity and that the avidity increased with time after infection. Antibodies produced by animals that have been seropositive for a long time and the maternally derived antibodies had a high avidity. There was no correlation between the amount of antibodies and avidity.