Parenteral immunization of mice with a genetically inactivated pertussis toxin DNA vaccine induces cell-mediated immunity and protection

Abstract

The immunogenicity and protective efficacy of a DNA vaccine encoding a genetically inactivated S1 domain of pertussis toxin was evaluated using a murine respiratory challenge model of Bordetella pertussis infection. It was found that mice immunized via the intramuscular route elicited a purely cell-mediated immune response to the DNA vaccine, with high levels of gamma interferon (IFN-c) and interleukin (IL)-2 detected in the S1-stimulated splenocyte supernatants and no serum IgG. Despite the lack of an antibody response, the lungs of DNA-immunized mice were cleared of B. pertussis at a significantly faster rate compared with mock-immunized mice following an aerosol challenge. To gauge the true potential of this S1 DNA vaccine, the immune response and protective efficacy of the commercial diphtheria-tetanus-acellular pertussis (DTaP) vaccine were included as the gold standard. Immunization with DTaP elicited a typically strong T-helper (Th)2-polarized immune response with significantly higher titres of serum IgG than in the DNA vaccine group, but a relatively weak Th1 response with low levels of IFN-c and IL-2 detected in the supernatants of antigen-stimulated splenocytes. DTaP-immunized mice cleared the aerosol challenge more efficiently than DNA-immunized mice, with no detectable pathogen after day 7 post-challenge.

Development of improved vaccines against whooping cough: Current status

“…130 Li et al 131 reported that a recombinant pertussis DNA vaccine expressing the pertussis toxin subunit 1 (PTS1), filamentous hemagglutinin (FHA) gene and pertactin (PRN) in pVAX1 were reported to elicit both antibody and cell-mediated immune responses in NIH strain of mice upon delivery by a parenteral route. This was in contrast to our studies 132 in which a genetically-inactivated pertussis toxin pcDNA3.1-based DNA vaccine administered by the intramuscular route was found to generate a purely cell-mediated immune response. We have further found that boosting DNA vaccine-primed mice with pertussis toxoid yielded excellent antibody as well as cell-mediated immune responses (Fry S, Chen, Daggard and Mukkur T, unpublished).…”

Comparative studies of the immunogenicity and protective potential of biofilmvsplanktonicStaphylococcus aureusvaccine against bovine mastitis using non-invasive mouse mastitis as a model system

“…Methods used for the stimulation of splenocytes cultured in vitro and collection of splenocyte supernatants were as described elsewhere (Fry et al 2008). Estimation of IFN-γ, as an indirect indicator of cell mediated immunity (CMI) was carried out for vaccinated and control groups of mice following stimulation with planktonic or biofilm S. aureus respectively.…”

“…Anti-S. aureus specific antibody isotypes, IgG, IgG 1 and IgG 2a, of pre-challenge serum samples of mice immunized with either planktonic or biofilm vaccine were determined following the indirect ELISA procedure as described elsewhere (Fry et al 2008). Formalin-killed S. aureus 51 suspended in PBS representing planktonic or biofilm cells was used to coat the wells in the Nunc-Immuno ™ MicroWell ™ 96 plates (Castle Hill, NSW, Australia).…”

“…The enzyme substrate used was p-nitrophenyl-phosphate and absorbance was measured at 405 nm using an ELISA plate reader (Model 550, BioRad, Gladesville, NSW, Australia). Specific absorbance normalized for plate to plate variation vs serum dilutions was plotted to calculate antibody titres as described elsewhere (Fry et al 2008). …”

Genetically detoxified pertussis toxin (PT-9K/129G): implications for immunization and vaccines

“…Innovative approaches based on the use of live-attenuated strains expressing PT-9K/129G [82], of the whole cell vaccine made from Bordetella strain overexpressing PT-9K/129G [83], of outer membrane vesicles derived from the wild-type strain [84], of genetically detoxified S1 delivered as DNA vaccine [85,86] or expressed by BCG [87], although very promising and probably effective in inducing a Th1 immune response, are still at the experimental stage. On the other hand, evidence that the vaccine containing the genetically detoxified PT-9K/129G induced an earlier and longer-lasting protection from disease at lower doses compared with chemically inactivated PT suggests that the superior immunogenicity and protective efficacy is due to better quality of the immune response.…”