Efficacy of a cold-adapted, intranasal, equine influenza vaccine: challenge trials.

A randomised, controlled, double-blind, influenza virus, aerosol challenge of horses was undertaken to determine the efficacy of a cold-adapted, temperature sensitive, modified-live virus, intranasal, equine influenza vaccine. Ninety 11-month-old influenza-naïve foals were assigned randomly to 3 groups (20 vaccinates and 10 controls per group) and challenged 5 weeks, 6 and 12 months after a single vaccination. Challenges were performed on Day 0 in a plastic-lined chamber. Between Days 1 and 10, animals were examined daily for evidence of clinical signs of influenza. Nasal swabs for virus isolation were obtained on Day 1 and Days 1 to 8 and blood samples for serology were collected on Days 1, 7 and 14. There was no adverse response to vaccination in any animal. Following challenge at 5 weeks and 6 months, vaccinates had significantly lower clinical scores (P = 0.0001 and 0.005, respectively), experienced smaller increases in rectal temperature (P = 0.0008 and 0.0007, respectively) and shed less virus (P<0.0001 and P = 0.03, respectively) over fewer days (P<0.0001 and P = 0.002, respectively) than did the controls. After the 12 month challenge, rectal temperatures (P = 0.006) as well as the duration (P = 0.03) and concentration of virus shed (P = 0.04) were significantly reduced among vaccinated animals. The results of this study showed that 6 months after a single dose of vaccine the duration and severity of clinical signs were markedly reduced amongst vaccinated animals exposed to a severe live-virus challenge. Appropriate use of this vaccine should lead to a marked reduction in the frequency, severity and duration of outbreaks of equine influenza in North America.

Spontaneous cardiomyopathy and exophthalmos in cotton rats (Sigmodon hispidus).

Exophthalmos and clinical signs of heart failure occurred sporadically in 3- to 12-month-old cotton rats (Sigmodon hispidus) in a colony originally derived from three male and four female littermates. Macroscopic lesions in severely affected animals included subcutaneous edema, hydrothorax, right ventricular dilatation, unilateral or bilateral atrial thrombosis, and exophthalmos. Hearts from 17 cotton rats that were found dead or were euthanatized because of exophthalmos or dyspnea and 33 control cotton rats were examined microscopically. Myocardial lesions were present in 46 of 46 cotton rats > or = 1 month of age and consisted of multifocal cardiac myocyte necrosis, mineralization, and mononuclear inflammatory cell infiltration. Cotton rats > 5 months of age also had foci of interstitial fibrosis and myocyte atrophy. Twelve of 24 (50%) necropsied cotton rats had chronic pulmonary congestion, and livers from eight of 24 (33%) had chronic periacinar congestion and atrophy. Thrombi were present in one or both cardiac atria in nine of 50 (18%) hearts, and in at least one orbital venous sinus in 14 of 24 (58%) necropsied cotton rats and in 12 of 14 (86%) with exophthalmos. Exophthalmos in this colony of cotton rats appears to have resulted predominantly from orbital venous sinus thrombosis caused by stasis of venous blood secondary to right heart failure associated with a heritable cardiomyopathy.

Minorities in the health professions: a current perspective.

This article discusses the problem of adequate minority representation in the health professions. Discussed here are some contours of the vexing problem of adequate minority participation in the health professions and a brief discussion of some programs that appear to be working. By "minority" here we mean underrepresented minorities in the health professions--Afro-Americans, Hispanic Americans, and native Americans. Asian Americans are not an underrepresented minority in this respect.

Monoclonal antibodies to bovine coronavirus glycoproteins E2 and E3: demonstration of in vivo virus-neutralizing activity.

Six monoclonal antibodies (MAbs) to bovine coronavirus (BCV, Quebec isolate) E2 and E3 glycoproteins which were found previously to be neutralizing in vitro were examined for virus-neutralizing activity in vivo. Surgically ligated intestinal loops of newborn colostrum-deprived calves were virus-inoculated, mock-infected or inoculated with a mixture of virus and antibody. Of the six BCV-specific MAbs, four were found to be protective against a virulent field isolate of BCV, as indicated by a reduction in villous atrophy. These MAbs were specific to antigenic domain A and antigenic domains A1 and A2 on the E2 and E3 glycoproteins respectively. MAbs to antigenic domains B and C on the E2 and E3 glycoproteins, respectively, were not protective.

Electron microscopic examination of cells of Pasteurella haemolytica-A1 in experimentally infected cattle.

Several modern electron microscopy techniques were used to examine Pasteurella haemolytica (biotype A, serotype 1) (strain B122) recovered from experimentally infected cattle and in situ within the lung tissue of experimentally infected cattle. Glycocalyx four to five times thicker than that seen on P. haemolytica grown in vitro was evident on bacterial cells recovered from live infected calves by pulmonary lavage. Fimbriae were also present on cells recovered by lavage. A thick glycocalyx was also seen on P. haemolytica-A1 within the lungs of experimentally infected cattle at necropsy. In summary, cells of P. haemolytica-A1 in experimentally infected cattle have fimbriae and glycocalyx on their cell surfaces and these structures appear to be important in bacterial colonization of the bovine respiratory tract and pathogenesis of shipping fever (Pasteurella) pneumonia.

A porcine-murine hybridoma that secretes porcine monoclonal antibody of defined specificity.

Spleen cells from a pig hyperimmunized with Escherichia coli were fused with nonproducer mouse plasmacytoma cells. Stable hybridoma lines secreting porcine immunoglobulins were obtained. One line secreted monoclonal porcine immunoglobulin G, which reacted specifically with E coli in an enzyme-linked immunosorbent assay and precipitated a polypeptide of molecular weight of 50,000. This is the first report of a stable porcine-murine hybridoma producing porcine antibody of defined specificity.

Chronic shedding of bovine enteric coronavirus antigen-antibody complexes by clinically normal cows.

Using an ELISA for the detection of virus-specific immune complexes, ten cows were found to be shedding bovine enteric coronavirus. The shedding patterns from five of these animals were followed for a period of 12 weeks, and all were found to be chronically shedding virus. Despite the presence of both faecal and serum antibody the infection was not cleared; therefore, the role of cell-mediated immunity (CMI) was investigated by immunosuppressing the chronically shedding cows with dexamethasone. No major role for CMI in maintaining the chronic infection could be determined, although immunosuppression did result in a temporary reduction in the shedding of virus-specific immune complexes.

Bovine-murine hybridoma that secretes bovine monoclonal antibody of defined specificity.

Spleen cells from a calf hyperimmunized with bovine enteric coronavirus were fused with nonproducer mouse plasmacytoma cells. Stable hybridoma lines secreting bovine immunoglobulins were obtained. One line secreted monoclonal bovine immunoglobulin G2, which reacted specifically with bovine enteric coronavirus in an enzyme-linked immunosorbent assay, inhibited virus hemagglutination, and precipitated a structural polypeptide with a molecular weight of 26,000 daltons.