Whooping cough caused by an infection with Bordetella pertussis or Bordetella parapertussis is a highly contagious respiratory disease. Globally, pertussis is the most prevalent vaccine-preventable disease. Even though the introduction of whole-cell (wP) and acellular pertussis (aP) vaccines has greatly reduced the burden of the disease, whooping cough still remains a problem in neonates and adolescents. B. pertussis is responsible for about 30 million cases of the disease each year, 90% of which are found in developing countries. About 300,000 of those infected, mostly infants, die from the infection. Various countries, especially developing nations, have reported an increase in infant morbidity due to pertussis. Recently, a rise in pertussis cases has also been observed in developed nations such as United States and Canada. Thus, novel vaccines against pertussis are urgently needed that would provide early and life-long protection.
Neonatal vaccination is challenging due to the presence of maternal antibodies (MatAbs) and the bias towards mounting Th2-type immune responses following early life vaccination. Our objective was to generate a novel vaccine against whooping cough that would offer protection in infancy in the presence of vaccine-neutralizing MatAbs. In order to first establish the model of interference, we vaccinated neonatal mouse pups and piglets in the presence and absence of passive immunity. Our experiments revealed that MatAbs interfered with active immunization using pertussis toxoid (PTd) and the level of passively transferred antibodies directly correlated with the level of interference that was observed. Nevertheless, we showed that this phenomenon could be overcome by using a second booster immunization or by co-formulating the toxoid with innate stimuli such as CpG ODN. Moreover, we also demonstrated that vaccination in the presence of MatAbs does not prevent responses to booster doses given later in life.
In order to improve the vaccine efficacy and immunogenicity we co-formulated the antigen with a novel adjuvant combination composed of CpG ODN, innate defense regulator peptide (IDRP) and polyphosphazene (PP). The model antigen ovalbumin (OVA) and adjuvants were formulated into PP microparticle and soluble formulations. These formulations were titrated and delivered to neonatal mice via parenteral and mucosal routes. Our experiments revealed that co-formulation of the antigen with the novel adjuvant platform resulted in a higher antibody production as compared to vaccinating with antigen alone. In addition, both the soluble and microparticle formulations composed of the adjuvant combination induced elevated anti-OVA IgG2a titers thus indicating a Th1-type response shift in neonatal mice. Intranasal route of vaccination was shown to be superior to parenteral vaccination as it resulted in the production of high concentrations of systemic IgG2a and IgA antibodies.
Lastly, we co-formulated PTd and filamentous hemagglutinin (FHA) with the novel adjuvant formulation and tested them in the presence and absence of passive immunity in the murine and porcine models of pertussis. Vaccines composed of the new adjuvant formulations induced an earlier onset of immunity, superior anti-pertussis IgG2a and IgA titers, and a balanced Th1/Th2-type responses when compared to immunization with Quadracel, one of the commercially available pediatric vaccines for pertussis. Most importantly, despite having half of the antigens of the Quadracel, the novel vaccine formulations offered protection against challenge infection in the presence of passively transferred MatAbs. Taken together our results demonstrate this novel vaccine formulation and delivery to be an excellent candidate for neonatal vaccination
