Clinical, virological and serological evaluation of the efficacy of peroral live rotavirus vaccination in calves kept under normal husbandry conditions

Monoclonal anti-idiotype induces antibodies against bovine Q17 rotavirus

This study describes, for the first time, the production and use of an "internal-image" anti-idiotypic monoclonal antibody (MAb) to elicit a rotavirus-specific antibody response. An immunoglobulin G2a MAb, designated RQ31 (MAb1), specific for the outer capsid protein VP4 of bovine Q17 rotavirus and capable of neutralizing viral infection in vitro was used to generate an anti-idiotypic MAb (MAb2). This MAb2, designated RQA2, was selected by enzyme-linked immunosorbent assay (ELISA) using F(ab')2 fragments of RQ31. RQA2 (MAb2) inhibited the binding of RQ31 (MAb1) to the virus but had no effect on the binding of other rotavirus-specific MAbs. The MAb2 also inhibited virus neutralization mediated by MAb1 in a dose-dependent fashion. Naive guinea pigs immunized with the MAb2 produced anti-anti-idiotypic antibodies (Ab3) that reacted with bovine Q17 rotavirus in an ELISA and neutralized rotavirus infection in vitro. The Ab3 response was characterized as MAb1-like because the Ab3 recognizes only the Q17 and neonatal calf diarrhea virus rotavirus strains in ELISA, as did RQ31 (MAb1). The Ab3 response also possessed two other characteristics of RQ31: the abilities to bind the 1.36 (double-capsid) but not the 1.38 (single-capsid) purified rotavirus fraction in ELISA and to immunoprecipitate the VP4 rotavirus protein.

Reduction in morbidity due to diarrhea in nursing beef calves by use of an inactivated oil-adjuvanted rotavirus-Escherichia coli vaccine in the dam

An outbreak of neonatal diarrhea occurred among beef calves (2000 animals) from one large Argentinian farm in 1985. Rotavirus was detected in 78% (106/136) and enterotoxigenic Escherichia coli in 1.5% of the samples (2/136) obtained from sick calves. In comparison rotavirus was identified in only 1.6% (1/63) of the samples from clinically healthy calves. The rotavirus strain responsible for the outbreak was characterized as serotype 6 belonging to group A. In the following three years the protective capacity of a combined rotavirus-E. coli inactivated vaccine administered to the dams during the last third of the gestation period was evaluated on this farm by comparison of morbidity due to diarrhea in calves from vaccinated vs. placebo cows within the same year. The morbidity due to diarrhea among calves from dams in the vaccinated and placebo groups was 34% and 77%, respectively in 1986; 23% and 47% in 1987, and 15% and 34%, in 1988. In 1987 morbidity of diarrhea in calves born from vaccinated heifers was 54% and 74% in calves from placebo heifers. In 1988 morbidity from diarrhea was 41% and 54%, respectively among calves in these two groups. In all experiments, calves from heifers showed significantly greater morbidity than calves from cows. Differences in diarrhea morbidity between the vaccinated and placebo groups were statistically significant (P less than 0.05). Additional studies showed that the diarrhea had a significant influence (P less than 0.05) on the average live weight of the calves at weaning (5 to 7 months) with an average weight loss of 7.8 kg per calf among the calves affected with diarrhea.

Immunization against bovine rotaviral infection

Calves fed with colostrum from cows vaccinated with an inactivated rotavirus vaccine were refractory to experimental infection with strain 81/36F of bovine rotavirus. In the field study, 458 pregnant cows from 26 herds were involved. In each herd, cows were selected and randomly subdivided in two groups. Cows in one group (248 head in total) were vaccinated, whereas cows in the other group (210 head in total) were left as unvaccinated controls. At calving, colostrum was collected from each cow and stored at -30 degrees C until used for feeding calves. The newborn calves, beginning the second day of life and for the next 7-10 days, were each fed a daily supplement of 400 ml of colostrum from its dam. The diarrhea occurred in 86 (40.9%) calves that had received colostrum from unvaccinated dams (normal colostrum), and in 7 (2.8%) calves which were fed colostrum from vaccinated dams (immune colostrum). The disease was very severe in the normal colostrum-fed calves and 52 of them died. By contrast, the 7 immune colostrum-fed calves displayed a rather mild enteric condition, and all recovered without any sequela being observed.

Further studies on passive immunization of newborn calves against rotaviral infection

An inactivated rotavirus vaccine was prepared with an adjuvant which gives a water-in-oil emulsion. The vaccine when injected into cows in their last month of pregnancy, proved to be as effective as the traditional vaccine, prepared with the Freud's incomplete adjuvant, in enhancing the lactogenic immunity. Thus, feeding experimentally infected calves with colostrum and first milk from vaccinated cows prevented diarrhea and reduced significantly rotavirus shedding. Because of its low grade viscosity the water-in-oil emulsifier facilitates inoculation of the vaccine and is therefore recommended as an adjuvant in the preparation of inactivated rotavirus vaccine.

Neonatal calf diarrhea induced by rotavirus

This presentation summarizes the results of a comprehensive study on rotaviruses isolated in Italy from calves and rabbits affected by neonatal diarrhea. The results clearly indicated that rotavirus infection is widespread and supported the evidence for an etiologic role of these viruses in neonatal diarrhea. The evidence of differences in virulence among bovine rotaviruses appeared also to be confirmed. Conventionally reared calves were fully susceptible to the experimental infection induced by three rotaviruses originating from heterologous hosts, i.e. monkeys, pigs and rabbits, respectively. When rotavirus strains of bovine, simian, porcine and rabbit origin were compared by cross neutralization tests, it was found the simian and porcine strains were indistinguishable and both appeared to relate antigenically to the bovine strain. On the other hand, a reciprocal antigenic correlation was found between bovine and rabbit isolates. Finally, it was proven that feeding newborn calves with colostrum of their dams, previously vaccinated with an inactivated rotavirus vaccine, could prevent the neonatal diarrhea from occurring.

Field trial evaluation of an inactivated rotavirus vaccine against neonatal diarrhea of calves

Field trials were conducted using an inactivated rotavirus vaccine for prevention of calf neonatal diarrhea. For the trials, 458 pregnant cows from 26 herds were involved. In each herd, cows which had been inseminated within a period of two months were selected and randomly subdivided in two groups. Cows in one group (248 head in total) were vaccinated 6 weeks before calving and again 4 weeks later; cows in the other group (210 head in total) were left as unvaccinated controls. At calving, colostrum was collected from each cow and stored at -30 degrees C until used for feeding calves. The newborn calves, beginning the second day of life and for the next 7-10 consecutive days, each was fed a daily supplement of 400 ml of colostrum from its dam. The diarrhea occurred in 86 (40.9%) calves that had received colostrum from unvaccinated dams (normal colostrum), and in 7 (2.8%) calves which were fed colostrum from vaccinated dams (immune colostrum). The disease was very severe in the normal colostrum-fed calves and 52 of them died. Those calves which survived the disease underwent a significant loss of condition. By contrast, the 7 immune colostrum-fed calves displayed a rather mild enteric condition, and all recovered without any sequela being observed.

Intestinal antibody response after vaccination and infection with rotavirus of calves fed colostrum with or without rotavirus antibody

The intestinal and systemic antibody response of calves vaccinated and/or challenged with rotavirus was studied employing isotype-specific ELISAs for the detection of IgG1, IgG2, IgM and IgA antibodies to rotavirus. Monoclonal antibodies to bovine immunoglobulin isotypes of proven specificity were used as conjugated or catching antibody. Five days after oral inoculation (dpi) of a 5-day-old gnotobiotic calf with rotavirus, IgM rotavirus antibodies were excreted in faeces, followed 5 days later by IgA rotavirus antibodies. The increase in IgM rotavirus antibody titre coincided with the inability to detect further rotavirus excretion. Faeces IgM and IgA rotavirus antibody titres fell to low levels within 3 weeks post infection. IgG1 and IgG2 rotavirus antibodies were not detected in faecal samples. In serum, antibodies to rotavirus of all four isotypes were detected, starting with IgM at 5 dpi. Two SPF-calves, which were fed colostrum free of rotavirus antibodies, were vaccinated with a modified live rotavirus vaccine and challenged with virulent rotavirus 6 days later. Upon vaccination, the calves showed an antibody response similar to the response of the infected gnotobiotic calf. Intestinal IgM rotavirus antibodies were excreted before or on the day of challenge and appeared to be associated with protection against challenge infection with virulent virus and rotavirus-induced diarrhoea. In 3 control calves, which were challenged only, the antibody patterns also resembled that of the gnotobiotic calf and again the appearance of IgM rotavirus antibodies coincided with the end of the rotavirus detection period. Two other groups of 3 SPF-calves were treated similarly, but the calves were fed colostrum with rotavirus antibodies during the first 48 h of life. These calves excreted passively acquired IgG1 and IgG2 rotavirus antibodies in their faeces from 2 to 6 days after birth. After vaccination, no IgM or IgA antibody activity in serum or faeces was detectable. Upon challenge, all calves developed diarrhoea and excreted rotavirus. Seven to 10 days after challenge low levels of IgM rotavirus antibody were detected for a short period. These data indicate that the intestinal antibody response of young calves to an enteric viral infection is associated with the excretion of IgM antibodies, immediately followed by IgA antibodies. This response is absent or diminished in calves with passively acquired specific antibodies which may explain the failure to induce a protective intestinal immune response by oral vaccination with modified live rotavirus of calves fed colostrum containing rotavirus antibodies.