Les immunostimulants orientent la reponse locale au virus de l''I.B.R. vers la production d''Interferon

Immuno-adjuvants like MDP or levamisole inoculated in the calf through general route increase the respiratory mucosa response to the irradiation inactivated IBRV.

We have shown from the 2nd day of the inoculation an interferon activity in the nasal mucus. This interferon partially destroyed at pH2 and at 56°C, persists in the respiratory fluids for one week. It is never found in the sera of the animals.

This inactivated virus given through nasal route does not stimulate antibody production in the local system or in the serum.

The dose of levamisole administered is critical: 5 mg/kg are the minimal quantity required to give a favourable answer whereas the 2.5 mg/kg normally used are without effect.

The interferon presence in the respiratory fluids gives a satisfactory interpretation of the good resistance to respiratory infection obtained in 500 calves with this treatment: inactivated virus by nasal route and immuno-adjuvant by intradermic or intramuscular route.