Evaluation of a non-invasive, inhalational challenge method for rabies vaccine potency assay.

Veterinary rabies vaccines are essential for safeguarding the public from exposure to rabies virus, as vaccination of domestic animals provides a barrier between humans and wildlife reservoirs. Ensuring rabies vaccines are potent and effective is paramount in preventing human exposure to rabies virus. The National Institutes of Health (NIH) test, a mouse vaccination-challenge assay, is the most widely used and internationally recognized assay for potency testing of inactivated rabies vaccines, and it is currently considered the method of choice. In the NIH test, vaccinated mice are challenged by the intracranial (IC) route. The response to the IC challenge can be variable, which often results in invalid tests. In addition, the IC challenge-exposure raises animal welfare concerns. The objective of this study was to evaluate the intranasal route of challenge as a modification to the NIH test to reduce animal pain and suffering until harmonized requirements for in vitro testing of rabies vaccines are developed. Results confirm the intranasal route is an effective route of rabies challenge in mice. However, a valid challenge requires the use of a more concentrated inoculum, in comparison to the intracranial method.

Potency testing of veterinary rabies vaccines: replacement of challenge by in vitro testing: considerations for development of alternative assays.

Vaccination of domestic animals against rabies creates a critical barrier between wildlife reservoirs and the human population. Ensuring these vaccines are potent and effective is paramount in preventing human exposure to this deadly and costly disease. The National Institutes of Health (NIH) test is, at present, the most widely used and internationally recommended potency assay for batch testing inactivated rabies vaccines. This test has numerous inherent limitations and disadvantages, including a lack of precision. The NIH test requires a large number of animals and involves unrelieved pain and suffering. A relevant in vitro assay should provide a more accurate, reproducible, rapid, safe, and humane rabies vaccine potency test.

Regulatory considerations for emergency use of non-USDA licensed vaccines in the United States.

The Virus-Serum-Toxin Act of 1913 (21 US Code 151-159) provides the legal basis for the regulation of veterinary biologicals in the United States; the United States Department of Agriculture's Center for Veterinary Biologicals (CVB) has the regulatory authority for the issue of licences and permits for such products. The law was intended to establish standards and control the importation of products into the United States and the distribution of products interstate assuring the purity, safety, potency, and efficacy of veterinary biological products. Administrative regulations and standards appear in the Title 9, Code of Federal Regulations, Parts 101-118, with additional programme guidance found in CVB Notices, Veterinary Services Memoranda, General Licensing Considerations, and other guidance documents. Pre-licensing data evaluation procedures are designed to assess the purity, safety, potency, and effectiveness of each product and support all product label claims. To fulfil these criteria, data from all phases of product development are evaluated against these key elements. Under the standard licensing process, this spectrum of evaluation includes complete characterization and identification of seed material and ingredients, laboratory and host animal safety and efficacy studies, stability studies, and post-licensing monitoring of field performance. This comprehensive evaluation may not be possible during the emergence of a new animal disease. While there are no specific regulations addressing the licensing standards of products for an emerging animal disease, there are mechanisms that allow for the availability of products in an emergency animal health situation. These mechanisms include autogenous biologicals, conditional licences, experimental and emergency use authorizations, and the importation of products in use elsewhere in the world. Pre-approved vaccine banks provide an additional mechanism.

Serum antibody responses of cattle vaccinated with partially purified native Pasteurella haemolytica leukotoxin.

The objective of these experiments was to study the serum antibody responses of cattle to partially purified, native Pasteurella haemolytica A1 leukotoxin (LKT) formulated with a commercial aluminum hydroxide-DDA-bromide adjuvant. In two experiments, calves received two intramuscular injections 21 days apart and sera were obtained periodically. Serum antibody responses to P. haemolytica outer membrane proteins (OMPs), formalinized P. haemolytica, and LKT were determined. In Experiment A, Holstein calves (140 kg each) were vaccinated with either 10, 1.0 or 0.1 micrograms of LKT, 10(9) c.f.u. of live P. haemolytica, or adjuvanted diluent. In Experiment B, mixed-breed beef calves (200 kg each) were vaccinated with either 100, 50 or 10 micrograms of LKT, 10(9) c.f.u. live P. haemolytica, or adjuvanted diluent. Vaccination of dairy calves with 10 micrograms of partially purified LKT stimulated LKT neutralizing antibody responses similar to those stimulated by vaccination of one calf with live P. haemolytica. In Experiment B, which used larger and different breeds of cattle, two vaccinations 3 weeks apart with 50 micrograms LKT stimulated LKT neutralizing responses equivalent to or greater than those stimulated by vaccination with live P. haemolytica. In both experiments, LKT vaccines stimulated only low antibody responses to formalinized P. haemolytica or to OMPs.

Growth-condition dependent expression of Pasteurella haemolytica A1 outer membrane proteins, capsule, and leukotoxin.

Pasteurella haemolytica, strain P1148 (biotype A, serotype 1) was grown under iron-rich and iron-restricted conditions both with and without serum, and the outer membrane protein (OMP), capsule, and leukotoxin production studied. OMPs were evaluated by SDS-PAGE and examined by immunoblot to identify antigens recognized by sera from P. haemolytica A1 convalescent and vaccinated cattle. Capsule production was evaluated using fluorescent antibody staining and rapid plate agglutination reaction. Leukotoxin production was measured by neutrophil 51Cr-release assay. Expression of specific OMPs, amount and antigenic character of capsule, and quantity of leukotoxin produced by P. haemolytica A1 varied in response to alterations in the growth media. Immunoblots indicated the immune response of convalescent calves differs from vaccinated calves, and convalescent calves produce antibodies to novel OMPs induced by growth in iron-restricted conditions.

Intra-abdominal hemorrhage associated with a granulosa-thecal cell neoplasm in a mare.

A 9-year-old American Saddlebred mare was referred because of abdominal distention and signs of abdominal pain. Copious peritoneal fluid obtained by abdominocentesis appeared to be frank blood. Rectal and ultrasonographic evaluation of the abdomen revealed a large mass at the distal tip of the right uterine horn. The mare was euthanatized and necropsied and the mass was determined to be a granulosa-thecal cell neoplasm. The most common clinical sign of granulosa-thecal cell neoplasm is infertility or abnormal sexual behavior. Hemoperitoneum is infrequently associated with neoplasms in horses.