Public Health Rep

19316437PMCnul

ANTIGENICITY OF POLYPEPTIDES (POLY ALPHA AMINO ACIDS) : XVI. GENETIC CONTROL OF IMMUNOGENICITY OF SYNTHETIC POLYPEPTIDES IN MICE

The ability of mice to form antibodies against the random terpolymer glu57lys38ala5 is controlled by a codominant Mendelian factor. Three of 7 inbred strains were 100 per cent responders; the others were completely negative. All of these strains could make antibody to related polymers with higher alanine content (10 and 40 mole per cent). Breeding studies using the progeny of Swiss mice indicated that a similar genetic factor was involved

Overview of Currently Approved Serological Methods with a Focus On Diphtheria and Tetanus Toxoid Potency Testing

AbstractVaccines are biological products made from living organisms. The natural complexity of biological molecules along with the inherent uncertainties of product manufacturing introduces the likelihood that random alterations can impact the quality of the vaccine each time it is made. The factors that can affect the final product are often unknown. Testing for potency of vaccine bulk or product dispensed into final containers was designed with the hope of ensuring that a vaccine is effective when used during its approved dating period and that its protective activity was not inadvertently altered during any phase of production. Ideally, potency testing measures a biological or biochemical property of the vaccine that is related to its ability to elicit protective immunity in the target population and provide some assurance that consistent clinical benefit is derived from each lot of product. Potency methods vary depending on the nature and composition of the vaccine. In vivo potency testing might entail immunizing groups of laboratory animals and then challenging them directly to measure survival, or involve serological potency assays in which sera from immunized laboratory animals are tested for the ability to neutralize pathogens or toxins. In the U.S., diphtheria toxoid and tetanus toxoid potency tests have customarily involved a serological method. This approach uses fewer animals than would have been required using a direct challenge method, while providing satisfactory evidence that each toxoid lot could induce protective immunity. This paper will discuss the details of the original U.S. test method for diphtheria and tetanus toxoid potency and present issues that must be considered when developing and validating non-animal-based approaches to refine or replace these tests

On Technological and Immunological Benefits of Multivalent Single-Injection Microsphere Vaccines

Purpose. With the aim of developing multivalent vaccines for single-injection, we examined the feasibility of combining antigens in biodegradable microspheres. Such vaccines are expected to improve vaccination coverage by reducing the number of vaccination sessions required to generate immunity. Methods. Mono- and multivalent vaccines of Haemophilus influenzae type b (Hib) conjugate, diphtheria toxoid (DT), tetanus toxoid (TT), and pertussis toxin (PT) in poly (lactic acid) and poly(lactic-coglycolic acid) microspheres were prepared by spray drying, and the influence of coencapsulated antigens and excipients on antigen loading, release, and stability was examined. Two tetravalent formulations were tested in guinea pigs. Results. Monovalent Hib and PT vaccines showed loading efficiencies of 10% (Hib) and 30% (PT) in both polymers. The loading efficiencies increased upon addition of trehalose and, even more, when the antigens were coencapsulated in di- and trivalent combinations. Highest loading efficiencies (>80%) were achieved with trivalent formulations (DT + PT + Hib) that also contained coencapsulated albumin. The percentage of antigen released during 24 h of incubation was typically 10-40% and decreased as loading efficiency increased. Enzyme-linked immunosorbent assay (ELISA) data revealed that TT, DT, and PT remained antigenic throughout the encapsulation and subsequent release processes. Finally, all antigens maintained their immunogenicity, since strong and sustained antibody responses were elicited after a single injection of tetravalent microsphere vaccines (DT + TT + PT + Hib) in guinea pigs. Conclusions. This study reveals technologic benefit as well as an immunological potential of multivalent single-injection microsphere vaccines. The results support our hypothesis that coencapsulation of several antigens may intrinsically improve entrapment of antigenic and immunogenic antigen probably by virtue of increased protein concentration during microencapsulation leading to mutual stabilization of the component