1. INSERM U404, Université Claude Bernard Lyon, IFR128 BioScience Lyon-Gerland, Lyon, France.
2. INSERM U548, Laboratoire d’Immunochimie, Université J. Fourier, CEA-G/DRDC, Grenoble, France.
3. CIRAD/EMVT, Programme Santé Animale, Montpellier, France.
4. Present address: Animal Production Unit, FAO/EA Agriculture and Biotechnology Laboratory, IAEA Labratories, Vienna, Austria.