Antigen-specific human polyclonal antibodies from hyperimmunized cattle.

Antigen-specific human polyclonal antibodies (hpAbs), produced by hyperimmunization, could be useful for treating many human diseases. However, yields from available transgenic mice and transchromosomic (Tc) cattle carrying human immunoglobulin loci are too low for therapeutic applications. We report a Tc bovine system that produces large yields of hpAbs. Tc cattle were generated by transferring a human artificial chromosome vector carrying the entire unrearranged, human immunoglobulin heavy (hIGH) and kappa-light (hIGK) chain loci to bovine fibroblasts in which two endogenous bovine IgH chain loci were inactivated. Plasma from the oldest animal contained >2 g/l of hIgG, paired with either human kappa-light chain (up to approximately 650 microg/ml, fully human) or with bovine kappa- or lambda-light chain (chimeric), with a normal hIgG subclass distribution. Hyperimmunization with anthrax protective antigen triggered a hIgG-mediated humoral immune response comprising a high proportion of antigen-specific hIgG. Purified, fully human and chimeric hIgGs were highly active in an in vitro toxin neutralization assay and protective in an in vivo mouse challenge assay.

A possible role for Clostridium difficile in the etiology of calf enteritis.

Clostridium difficile was investigated as a possible cause of enteritis in calves. The organism and its toxins (TcdA and TcdB), respectively, were found in 25.3% and 22.9% of stool samples from diarrheic calves. Culture positive samples were more likely than culture negative samples to be toxin positive. However, toxin positive stools were more common among nondiarrheic calves, but diarrheic calves were nearly twice as likely to be culture positive. Ribotype 078 was dominant among isolates. Salmonella sp. was isolated from both diarrheic and nondiarrheic calves, but large numbers of E. coli were found more commonly in diarrheic calves than in nondiarrheic animals. Prevalence rates for coronavirus and Cryptosporidium sp. were substantially higher in nondiarrheic calves than in diarrheic, but rates of detection of rotavirus and Giardia sp. were more nearly equal between groups. Lesions in naturally infected calves included superficial mucosal erosion with associated fibrinous exudates. Neutrophils and eosinophils infiltrated lamina propria. Large Gram-positive rods morphologically compatible with C. difficile were abundant in the colonic lumen and the organism was isolated by bacteriologic culture. Toxins were found throughout the colon. Purified toxins A and B (individually and conjointly) caused comparable lesions, as well as fluid accumulation, in ligated intestinal loops. Our findings are in substantial agreement with those of others [Rodriguez-Palacios, A., Stampfli, H.R., Duffield, T., Peregrine, A.S., Trotz-Williams, L.A., Arroyo, L.G., Brazier, J.S., Weese, J.S., 2006. Clostridium difficile PCR ribotypes in calves, Canada. Emerg. Infect. Dis. 12, 1730-1736; Porter, M.C., Reggiardo, C., Bueschel, D.M., Keel, M.K., Songer, J.G., 2002. Association of Clostridium difficile with bovine neonatal diarrhea. Proc. 45th Ann. Mtg. Amer. Assoc. Vet. Lab. Diagn., St. Louis, MO, U.S.A.] and add strength to a working hypothesis that C. difficile infection and the accompanying intoxication can manifest as diarrhea in calves. It seems clear that calves serve as multiplying hosts for this organism.