WHO Working Group meeting on standardization of acellular pertussis vaccines: Potency assay

Evaluation of acellular pertussis vaccine: comparisons among different strains of mice

The current study was designed to comparatively analyze the reactions of different mouse strains in response to acellular pertussis(aP) vaccine, with attempt to further provide a reference for aP vaccine evaluation. NIH mice, ICR mice, and BALB/c mice adopted from different pharmacopoeias and studies were utilized to measure the immune protection and immunogenicity of the same batch of aP vaccine according to the MICA from some Asian pharmacopoeias and the pertussis serological potency test (PTST) method from European Pharmacopoeia. Based on our results, the aP vaccine detected by NIH mice had the best potency. So the NIH mice were more suitable for detecting the immune protection of aP vaccine by the Modified intracerebral challenge assay (MICA)method. Given that the levels of PT-IgG and FHA-IgG antibodies in ICR mice were the highest, and the levels of Th1 and Th2 cells were significantly increased (P < 0.01), it was more suitable for the detection of immunogenicity of aP vaccine by PSPT method. Spleen lymphocytes were stimulated by PT and FHA. And the levels of IL-4 in ICR mice and NIH mice were significantly increased, so were the levels of IL-17, IL-23, IL-27, and TNF-α in BALB/c mice. NIH mice have stronger adaptive immunity and the weakest inflammatory response, and ICR mice have enhanced adaptive immunity and inflammatory responses, both of which can be thereby used for evaluation by different pharmacopoeia methods. NIH was more suitable for the MICA method of Chinese Pharmacopoeia, and ICR for the PSPT method of European Pharmacopoeia.

3-Self behavior modification programs base on the PROMISE Model for clients at metabolic risk

The objectives of this mixed methods research were 1) to study effects of the health behavior modification program (HBMP) conducted under the principles of the PROMISE Model and the CIPP Model and 2) to compare the 3-self health behaviors and the biomedical indicators before with after the program completion. During the program, three sample groups including 30 program leaders, 30 commanders and 120 clients were assessed, and there were assessments taken on 4,649 volunteers who were at risk of metabolic syndrome before and after the program conducted in 17 hospitals. The collected data were analyzed by the t-test and the path analysis. The research instruments were questionnaires used for program evaluation, structuralized interview forms, and questionnaires used for 3-self health behavior assessment. The findings were as follows: 1) During the program, the assessment result deriving from comparing the overall opinions toward the program among the three sample groups showed no difference (F=2.219), 2) The program management factors based on the PROMISE Model (positive reinforcement, optimism, context, and process or activity provision) had an overall influence on the product or success of the HBMP (p< 0.05) with size effects at 0.37, 0.13, 0.31 and 0.88 respectively. All of the factors could predict the product of the program by 69%. 3) After participating in the program, the clients’ 3-self health behaviors (self-efficacy, self-regulation, and self-care) were significantly higher than those appeared before the participation (p< 0.05), and their biomedical indicators (BMI, blood pressure, waistline, blood glucose, lipid profiles, cholesterol, and HbA1c) were significantly lower than those measured before the program (p< 0.05).

Feasibility of the use of ELISA in an immunogenicity-based potency test of anthrax vaccines

Complexities of lethal challenge animal models have prompted the investigation of immunogenicity assays as potency tests of anthrax vaccines. An ELISA was used to measure the antibody response to protective antigen (PA) in mice immunized once with a commercially available (AVA) or a recombinant PA vaccine (rPAV) formulated in-house with aluminum hydroxide. Results from the anti-PA ELISA were used to select a single dose appropriate for the development of a potency test. Immunization with 0.2 mL of AVA induced a measurable response in the majority of animals. This dose was located in the linear range of the vaccine dose-antibody response curve. In the case of rPAV, practical limitations prevented the finding of the best single dose for the potency testing of purified vaccines. In additional immunogenicity experiments neither the magnitude of the response to a single dose of vaccine, nor the estimation of the dose necessary to induce a measurable response were able to consistently detect brief exposure of vaccines to potentially damaging temperatures. However, differences detected for rPAV in the proportion of mice responding to the same dose of treated and untreated vaccine suggested that further assay development to increase the sensitivity of the latter design may be warranted.

Synergic effect of genotype changes in pertussis toxin and pertactin on adaptation to an acellular pertussis vaccine in the murine intranasal challenge model

The Bordetella pertussis pertussis toxin and pertactin (Prn) are protective antigens and are contained in acellular pertussis vaccines. Polymorphisms in the A subunit of pertussis toxin (PtxA) and pertactin have been proposed to mediate vaccine resistance and contribute to pertussis reemergence. To test this hypothesis, previous studies compared clinical isolates expressing different alleles for the proteins. However, other virulence factors or virulence factor expression levels also may vary, confounding the analysis. To overcome these limitations, we constructed isogenic mutants of B. pertussis Tohama expressing the alleles ptxA1 or ptxA2 and prn1 or prn2 and compared the efficacies of an acellular pertussis vaccine against the mutants in a mouse model. While the vaccine was effective against all of the B. pertussis strains regardless of the allele expression pattern, the strain expressing ptxA1 and prn2 displayed a survival advantage over the other strains. These results suggest that an allele shift to the ptxA1 prn2 genotype may play a role in the emergence of pertussis in vaccinated populations.

Vaccines and biosimilarity: a solution or a problem?

Biosimilarity is a significant issue for vaccines and a reasonable approach to this could facilitate licensing of follow-on products of similar design. However, the definitions and guideline criteria developed for similar versions of biotherapeutics may be too restrictive for vaccines, as the molecular composition of their active substances can rarely be defined precisely, and immunogenicity is an essential rather than an undesirable characteristic. Similarity in antigenic composition may be more relevant. The criteria that determine biosimilarity need more careful definition; superficial similarity may conceal significant differences in performance that can only be disclosed by careful clinical evaluation. These issues have been reviewed in detail for current types of bacterial and viral vaccines. For truly biosimilar products, limited clinical studies could be acceptable provided that they permit side-by-side comparison with the original product or another suitable reference. The prospect of the development of biosimilar products also emphasizes the need for improved regulatory tests capable of detecting subtle but biologically significant differences in vaccines. The need for an acceptable definition of biosimilarity and guidelines relevant to vaccines is emphasized.