Establishment of the national reference standard for tetanus toxoid in Thailand.

The use of reference materials is the basis of standardization and quality control of biologicals such as vaccines produced by different manufacturers and lot-to-lot consistency. The aim of this study was to establish a secondary local and national reference standard of adsorbed tetanus toxoid that can be used for tetanus toxoid vaccine potency testing. Concentrated bulk of tetanus toxoid was adjuvanted and aliquoted before lyophilization. Lyophilized product was tested for biological and physicochemical qualities, including moisture content, identity, appearance, antigen content, degree of adsorption, and sterility. The potency of the candidate reference material was calibrated against the 4th World Health Organization International Standard (WHO IS) for tetanus toxoid by two independent laboratories (BioNet-Asia and Thai National Control Laboratory) using the WHO mouse challenge test. A total of 839 vials with lyophilized tetanus toxoid reference material were produced. Potency was estimated at 115 IU/vial [intra-laboratory geometric coefficient of variation (GCV) of 7 tests was 16.5%] and 112 IU/vial (intra-laboratory GCV of 5 tests was 38.6%) at the two laboratories, with an inter-laboratory GCV of 25.5%. The potency of the candidate standard was assigned a value of 114 IU/vial. The candidate reference standard was approved by The Thai National Central Laboratory (NCL) as the Thai national tetanus toxoid reference standard.

Co-species housing in mice and rats: effects on physiological and behavioral stress responsivity.

Co-species housing of mice and rats is common practice at most breeding facilities and research laboratories, neglecting the possible effects on the animals. We investigated physiological as well as behavioral stress-reactivity in mice and rats which were either derived from a co-species or species-separated housing condition at the breeding facilities. The animals were kept under the housing condition they were used to or assigned to the opposite one. Co-species housing had a significant impact on acute stress reactivity in mice and rats but only if they were used to this housing condition throughout their lives. Moreover, the stress-effects appeared to be long lasting. Assigning animals, derived from a species-separated housing condition, to co-species housing led to chronic stress in mice and affected experimental behavior of rats. Our findings led to the conclusion that co-species housing in mice and rats should be avoided, supporting the recommendations by the U.S. National Institutes of Health (NIH) and the Dutch Ministry of Health, Welfare and Sport (VWS). In order to support the interpretation, facilitate the reproducibility and comparability and subsequently the generalizability of experimental results, breeding facilities should at least provide detailed information about their housing conditions.