A PCR detection method for testing Mycoplasma contamination of veterinary vaccines and biological products.

A rapid test method was developed for detecting mycoplasma contamination in veterinary biological products. The method reduces testing time by 2 weeks and shows comparable sensitivity to the current agar-based detection model. The primary goals for the development of the test were to reduce the testing time, incorporate a method that was easily adaptable across the veterinary biologics industry and reduce the subjective interpretation of results. We found that biological enrichment is necessary to maintain sensitivity of the detection method when compared to the standard culture-based test and that periodic sampling of enrichment cultures is essential to detect a wide variety of mycoplasma species that may be present as contaminants. The PCR detection method is comparable to the agar-based model and can reduce the overall testing time by up to 14 days.

Opportunities and strategies to further reduce animal use for Leptospira vaccine potency testing.

Hamsters are routinely infected with virulent Leptospira for two purposes in the regulation of biologics: the performance of Codified potency tests and maintenance of challenge culture for the Codified potency tests. Options for reducing animal use in these processes were explored in a plenary lecture at the "International Workshop on Alternative Methods for Leptospira Vaccine Potency Testing: State of the Science and the Way Forward" held at the Center for Veterinary Biologics in September 2012. The use of validated in vitro potency assays such as those developed by the U.S. Department of Agriculture for Leptospira (L.) canicola, Leptospira grippotyphosa, Leptospira pomona, and Leptospira icterohaemorrhagiae rather than the Codified hamster vaccination-challenge assay was encouraged. Alternatives such as reduced animal numbers in the hamster vaccination-challenge testing were considered for problematic situations. Specifically, the merits of sharing challenge controls, reducing group sizes, and eliminating animals for concurrent challenge dose titration were assessed. Options for maintaining virulent, stable cultures without serial passage through hamsters or with decreased hamster use were also discussed. The maintenance of virulent Leptospira without the use of live animals is especially difficult since a reliable means to maintain virulence after multiple in vitro passages has not yet been identified.

Development of in vitro assays for measuring the relative potency of leptospiral bacterins containing serogroups canicola, grippotyphosa, icterohaemorrhagiae, and pomona.

Historically, potency testing of bacterins containing Leptospira involved a hamster vaccination-challenge assay. The United States Department of Agriculture (USDA) has long recognized that an in vitro system has several inherent advantages over the animal model. This is a review of the work performed at the USDA to replace the hamster vaccination-challenge model used to test Leptospira bacterins. The work covered a span of approximately 20 years and resulted in the development of USDA monoclonal antibody based enzyme-linked immunosorbent assays (ELISAs) for the quantitation of antigen in bacterins containing Leptospira serogroups canicola, icterohaemorrhagiae, pomona, and grippotyphosa. The monoclonal antibodies used in the assay a) recognize lipopolysaccharide-like epitopes on the surface of the whole cell, b) agglutinate the homologous leptospiral serovars but do not agglutinate heterologous leptospiral serovars or heterologous bacterial species, and c) passively protect hamsters against a homologous challenge but fail to protect hamsters against heterologous challenges. Once developed, the performance of each ELISA was evaluated at the USDA followed by industry evaluation. Serials that passed the hamster vaccination-challenge assay yielded ELISA relative potency values of 1.0 or greater. These ELISAs have been shown to be a reproducible, sensitive, specific, and inexpensive alternative to the current Codified hamster potency assay.

USDA regulatory guidelines and practices for veterinary Leptospira vaccine potency testing.

Batch-release potency testing of leptospiral vaccines licensed by the United States Department of Agriculture (USDA) historically was conducted through animal vaccination-challenge models. The hamster vaccination-challenge assay was Codified in 1974 for bacterins containing Leptospira pomona, Leptospira icterohaemorrhagiae, and Leptospira canicola, and in 1975 for bacterins containing Leptospira grippotyphosa. In brief, 10 hamsters are vaccinated with a specified dilution of bacterin. After a holding period, the vaccinated hamsters, as well as nonvaccinated controls, are challenged with virulent Leptospira and observed for mortality. Eighty percent of vaccinated hamsters must survive in the face of a valid challenge. The high cost of the Codified tests, in terms of monetary expense and animal welfare, prompted the Center for Veterinary Biologics (CVB) to develop ELISA alternatives for them. Potency tests for other serogroups, such as Leptospira hardjo-bovis, that do not have Codified requirements for potency testing continue to be examined on a case-by-case basis.