Safety assessments of recombinant DTaP vaccines developed in South Korea

Abstract

Purpose: Pertussis bacteria have many pathogenic and virulent antigens and severe adverse reactions have occurred when using inactivated whole-cell pertussis vaccines. Therefore, inactivated acellular pertussis (aP) vaccines and genetically detoxified recombinant pertussis (rP) vaccines are being developed. The aim of this study was to assess the safety profile of a novel rP vaccine under development in comparison to commercial diphtheria-tetanus-acellular pertussis (DTaP) vaccines.

Materials and methods: The two positive control DTaP vaccines (two- and tri-components aP vaccines) and two experimental recombinant DTaP (rDTaP) vaccine (two- and tri-components aP vaccines adsorbed to either aluminum hydroxide or purified oat beta-glucan) were used. Temperature histamine sensitization test (HIST), indirect Chinese hamster ovary (CHO) cell cluster assay, mouse-weight-gain (MWG) test, leukocytosis promoting (LP) test, and intramuscular inflammatory cytokine assay of the injection site performed for safety assessments.

Results: HIST results showed absence of residual pertussis toxin (PTx) in both control and experimental DTaP vaccine groups, whereas in groups immunized with tri-components vaccines, the experimental tri-components rDTaP absorbed to alum showed an ultra-small amount of 0.0066 IU/mL. CHO cell clustering was observed from 4 IU/mL in all groups. LP tests showed that neutrophils and lymphocytes were in the normal range in all groups immunized with the two components vaccine. However, in the tri-components control DTaP vaccine group, as well as two- and tri-components rDTaP with beta-glucan group, a higher monocyte count was observed 3 days after vaccination, although less than 2 times the normal range. In the MWG test, both groups showed changes less than 20% in body temperature and body weight before the after the final immunizations. Inflammatory cytokines within the muscle at the injection site on day 3 after intramuscular injection revealed no significant response in all groups.

Conclusion: There were no findings associated with residual PTx, and no significant differences in both local and systemic adverse reactions in the novel rDTaP vaccine compared to existing available DTaP vaccines. The results suggest that the novel rDTaP vaccine is safe.

Keywords: Bordetella pertussis; Diphtheria-tetanus-acellular pertussis vaccines; Murine model study; Recombinant DTaP vaccine; Safety.

Fig. 1. Temperature histamine sensitization test results showing (A) the linear line of reference pertussis toxin (PTx) (NIBSC 15/126) Standard, (B) the results of bivalent control or experimental diphtheria-tetanus-acellular pertussis (DTaP) vaccines, and (C) the results of trivalent control or experimental DTaP vaccines. NIBSC, National Institute for Biological Standards and Control; rP, recombinant pertussis; CI, confidence interval; SEM, standard error of mean.

Fig. 2. Leukocytes distributions at 3 days after immunization with bivalent diphtheria-tetanus-acellular pertussis (DTaP) vaccines. (A) Neutrophil concentration. (B) Lymphocyte concentration. (C) Monocyte concentration. Horizontal bold blue line indicates upper limit of monocyte normal ranges. WBC, white blood cell; rP, recombinant pertussis. ^a)The normal range of mouse blood cell counts was provided by Charles River Laboratories (Wilmington, MA, USA).

Fig. 3. (A, B) Leukocytes distributions at 1 and 3 days after immunization with trivalent diphtheria-tetanus-acellular pertussis (DTaP) vaccines. WBC, white blood cell; rP, recombinant pertussis. ^a)The normal range of mouse blood cell counts was provided by Charles River Laboratories (Wilmington, MA, USA).

Fig. 4. Weight and temperature changes after immunization with bivalent diphtheria-tetanus-acellular pertussis (DTaP) vaccines. (A) Weight changes in grams versus days after post-vaccination. (B) Weight changes in percentages versus days after post-vaccination. (C) Temperature changes in Celsius versus days after post-vaccination. (D) Temperature changes in percentages versus days after post-vaccination. WBC, white blood cell; rP, recombinant pertussis; SEM, standard error of mean; CI, confidence interval.

Fig. 5. Weight and temperature changes after immunization with trivalent diphtheria-tetanus-acellular pertussis (DTaP) vaccines. (A) Presenting weight changes in grams versus days after post-vaccination. (B) Weight changes in percentages versus days after post-vaccination. (C) Temperature changes in Celsius versus days after post-vaccination. (D) Temperature changes in percentages versus days after post-vaccination. WBC, white blood cell; rP, recombinant pertussis; SEM, standard error of mean; CI, confidence interval.

Fig. 6. Inflammatory muscular cytokines at vaccine injection sites 3 days after immunizations with bivalent diphtheria-tetanus-acellular pertussis (DTaP) vaccines (A) and trivalent DTaP vaccines (B). rP, recombinant pertussis; IL, interleukin; IFN-γ, interferon-γ; TNF-α, tumor necrosis factor-α; SDF-1, stromal cell-derived factor-1; NEG, negative control; I-TAC, interferon-inducible T cell α chemoattractant; TCA-3, T-cell activation gene-3; KC, keratinocyte-derived cytokine; TECK, thymus-expressed chemokine; LIX, lipopolysaccharide-induced CXC chemokine; TIMP, tissue inhibitors of metalloproteinase; BLC, B-lymphocyte chemoattractant; MCP-1, monocyte chemotactic protein-1; MCSF, macrophage-colony stimulating factor; MIG, monokine induced by gamma interferon; MIP, macrophage inflammatory protein; GCSF, granulocyte-colony stimulating factor.