Lactogenic immunity: modulation of immune response and protection against RV diarrhea in a calf model.

GISELA MARCOPPIDO; LORENA GARAICOECHEA; DANIELA RODRIGUEZ; MARINA MOSGOVOJ; FERNANDO FERNANDEZ; MARÍA M. VENA; VIVIANA PARREÑO

Ouro Preto, Brazil

Simposio; 8º International Veterinary Immunology Symposium.; 2007

Society for Veterinary Immunology

Bovine rotavirus (BRV) is a major cause of diarrhea in neonatal calves worldwide. It is postulated that continuos levels of passive and active antibodies (Abs) in the intestinal lumen provide efficient protection against infection and illness. Passive protection against RV and the modulation of the immune response in calves fed supplemented-milk with anti-BRV Abs derived from immune colostrum was evaluated. Newborn calves (n=31) were divided in 4 experimental groups (G): G1= colostrum-deprived; G2=receiving colostrum and fed milk without Abs; G3 and G4=receiving colostrum and fed supplemented milk with 2 concentrations of colostrum Abs (IgG1=1024 and 4096). Milk supplementation was extended for 14 days. The calves were orally inoculated with IND (P[5]G6) BRV at 2 days of age (0 post-inoculation day (dpi) and re-challenged at 21dpi. All calves of control groups (G1 and G2) and 50%  of the animals from G3 and G4 were euthanized at 21 dpi. The rest of the animals were  euthanized at 35 dpi. Anti-BRV Abs titers in serum were evaluated weekly and fecal Abs were daily analyzed by isotype-specific ELISA and virus neutralization. The number of BRV-specific antibody secreting cells (ASC) in intestinal and systemic lymphoid tissue was evaluated by ELISPOT. After BRV inoculation, all control calves became infected and suffered severe diarrhea. In G3, all the calves were infected, but only 62,5% (5/8) developed diarrhea. In G4, 40% (4/10) of the calves were fully protected, while asymptomatic infection was observed in other 4 animals and 20% (2/10) of the calves developed diarrhea. These calves showed a significant delay in the onset of diarrhea and virus shedding, both of shorter duration, compared to control groups. Full protection against challenge (21 dpi) was observed in all of the calves from G3 (4/4) and in 4 animals (4/5) from G4. A decreasing magnitude of the IgM and IgA mediated anti-BRV immune response in serum and feces in milk-supplemented groups was observed, as  the amount of colostrum added to the milk increased. The number of Anti-BRV ASC was lower in systemic lymphoid tissue and tended to dissappear in G4. However, in the milk-supplemented groups, a large number of IgA and IgG1 anti-BRV AS was detected along the mucosal lymphoid tissue , mainly in Duodenum and Yeyunum. Calf feeding with BRV-immune milk during the first two weeks of life is an efficient strategy to reduce BRV infection without interfering in the development of the neonatal mucosal immune response.