Evaluation of standard reagents for radial-immunodiffusion assays. In vitro control of rabies vaccines.

The RID assay is one of the in vitro methods used for in-process control in the production of rabies vaccines for veterinary use. It has been shown to be very useful for determining antigen concentration in the final bulk product. The work presented in this paper, including the production and standardization of candidate standard reagents for use in the Radial Immunodiffusion Assay (RID) was carried out at the Pan American Institute for Food Protection and Zoonoses (INPPAZ/PAHO/WHO). The study was completed with the cooperation of the Faculty of Veterinary Sciences, National University of La Plata (NULP), Argentina, where the validation of the proposed standards and the quality control of samples from 28 different batches of rabies vaccines produced with Pasteur strain rabies virus (PV) in BHK cells were performed. The activity of the vaccines was determined by in vivo (NIH) and in vitro (RID)assays. The results of the candidate reagents for the reagent standardization tests showed stability, sensitivity and reproducibility. The Relative Potency the 1.2 between the problem vaccines and the reference vaccine was estimated by variance and regression analysis. The results of our validation study show that the INPPAZ (PAHO/WHO) is capable of producing and distributing the above-mentioned standard reagents, as well as of providing support for the incorporation of the RID technique (sensitive, rapid and inexpensive) to the laboratories that manufacture rabies vaccines in Latin America and the Caribbean.

Fumonisin levels in commercial corn products in Buenos Aires, Argentina.

Fumonisins B1 (FB1) and B2 (FB2) were determined in 35 samples of corn flour and corn grits destined for human consumption and purchased directly from Buenos Aires food shops and supermarkets from October 1996 to January 1997 and during the month of January 1998. During the first period of sample collecting, 16 out of 19 samples were found to be contaminated. Considering all 19 samples, contamination levels were between not detected and 1860 ng/g FB1, and from not detected to 768 ng/g FB2. During the second period all 16 samples were found to be contaminated with levels ranging from 75 to 4987 ng/g FB1, and from not detected to 1818 ng/g FB2. The levels of FB1 and FB2 in the samples collected during January 1998 were significantly higher than the samples collected during the period from October 1996 to January 1997. No significant difference was found in terms of fumonisin levels between the branded and unbranded samples.

[Counterimmunoelectrophoresis technique for determining the antigenic potency of rabies vaccine]. / Evaluación de la técnica de contrainmunoelectroforésis para determinar la potencia antigénica de las vacunas antirrabicas.

The method recommended by the World Health Organization (WHO) for the potency assay of human and animal rabies vaccines as final product is the NIH test. Some in vitro techniques have been proposed for in process testing and supplement the in vivo test mentioned above. This paper presents the results obtained when using a counterimmunoelectrophoresis (CIE) techniques to determine the antigens content in samples of 84 and 40 samples of lots of suckling mouse rabies and tissue culture rabies vaccines, respectively. The evaluation of rabies vaccines under, at, near and up to 0.3 UI by the NIH and CIE tests showed that for practical use, a CIE titer of 1:4 would match the minimum of NIH potency test requirement. Low degree of CIE test variability within our laboratory was observed, when two working reference and 7 lots of rabies vaccines from different origin and activity were tested in five independent assays. All titres fell within one double dilution what is an indication of its reproducibility. Good sensitivity to detect antigen deterioration in thermal degradation test was observed when samples of 3 lots of liquid suckling mouse rabies vaccine were held stored at 4 degrees C or at 37 degrees C for 4 weeks and assays by CIE and NIH tests. Finally, CIE test could apply by manufactures to follow the concentration procedures to determine the final end point which could match a desired antigenic value in the NIH potency test.

Medición de niveles de antibióticos en vacunas oleosas antiaftosa por métodos químicos

Este artículo informa los resultados de un estudio para seleccionar las condiciones óptimas de trabajo para la utilización de la cromatografía en capa fina (TLC) en la determinación de los niveles de penicilina, neomicina y polimixina en vacuna oleosa antiaftosa. Se describen los procedimientos de elección para el quiebre de la emulsión y para extraer, purificar, concentrar, identificar y cuantificar los antibióticos. Se presentan los resultados obtenidos al exminar por TLC una serie de vacunas oleosas antiaftosa disponibles comercialmente. Los hallazgos se analizan en términos de la aplicación de esta metodología para el control de la calidad de estos inmunógenos y para el estudio de las reacciones posvacunación.

This paper reports the results of a study to select the optimal working conditions for rendering thin layer chromatography (TLC) useful for determining the levels of penicillin, neomycin and polymyxin in FMD oil vaccines. Procedures are described for breaking vaccine emulsions and for extracting, purifying, concentrating, identifying and quantifying the antibiotics contained in them. Subsequently, commercially avaiable FMD oil vaccines were examined by these procedures. Findings are discussed in terms of the application of TLC for quality control of immunogens and for studying post-vaccinal reactions.