Is there a need for a new generation of vaccines against pertussis?

Expanding the role of bacterial vaccines into life-course vaccination strategies and prevention of antimicrobial-resistant infections

A crisis in bacterial infections looms as ageing populations, increasing rates of bacteraemia and healthcare-associated infections converge with increasing antimicrobial resistance and a paucity of new antimicrobial classes. New initiatives are needed to develop bacterial vaccines for older adults in whom immune senescence plays a critical role. Novel vaccines require an expanded repertoire to prevent mucosal diseases such as pneumonia, skin and soft tissue infections and urinary tract infections that are major causes of morbidity and mortality in the elderly, and key drivers of antimicrobial resistance. This review considers the challenges inherent to the prevention of bacterial diseases, particularly mucosal infections caused by major priority bacterial pathogens against which current vaccines are sub-optimal. It has become clear that prevention of many lung, urinary tract and skin infections requires more than circulating antibodies. Induction of Th1/Th17 cellular responses with tissue-resident memory (Trm) cells homing to mucosal tissues may be a pre-requisite for success.

Immunogenicity and safety of primary and booster vaccination with 2 investigational formulations of diphtheria, tetanus and Haemophilus influenzae type b antigens in a hexavalent DTPa-HBV-IPV/Hib combination vaccine in comparison with the licensed Infanrix hexa

Safety and immunogenicity of 2 investigational formulations of diphtheria, tetanus and Haemophilus influenzae type b antigens of the combined diphtheria-tetanus-acellular pertussis-hepatitis B-inactivated poliomyelitis-Hib vaccine (DTPa-HBV-IPV/Hib) were evaluated in a Primary (NCT01248884) and a Booster vaccination (NCT01453998) study.

In the Primary study, 721 healthy infants (randomized 1:1:1) received 3 doses of DTPa-HBV-IPV/Hib formulation A (D_AT_APa-HBV-IPV/Hib), or B (D_BT_BPa-HBV-IPV/Hib) or the licensed DTPa-HBV-IPV/Hib vaccine (Infanrix hexa, GSK; control group) at 2, 3, 4 months of age. Infants were planned to receive a booster dose at 12–15 months of age with the same formulation received in the Primary study; however, following high incidence of fever associated with the investigational formulations in the Primary study, the Booster study protocol was amended and all infants yet to receive a booster dose (N = 385) received the licensed vaccine.

In the Primary study, non-inferiority of 3-dose vaccination with investigational formulations compared with the licensed vaccine was not demonstrated due to anti-pertactin failing to meet the non-inferiority criterion. Post-primary vaccination, most infants had seroprotective levels of anti-diphtheria (100% of infants), anti-tetanus antigens (100%), against hepatitis B (≥ 97.5% across groups), polyribosyl-ribitol-phosphate (≥ 88.0%) and poliovirus types 1–3 (≥ 90.5%). Seropositivity rates for each pertussis antigen were 100% in all groups.

Higher incidence of fever (> 38°C) was reported in infants receiving the investigational formulations (Primary study: 75.0% [A] and 72.1% [B] vs 58.8% [control]; Booster study, before amendment: 49.4% and 46.6% vs 37.4%, respectively).

The development of the investigational formulations was not further pursued.

Epidemiology of pertussis in two Ibero-American countries with different vaccination policies: lessons derived from different surveillance systems

Background

Pertussis is a re-emerging disease worldwide despite its high vaccination coverage. European and Latin-American countries have used different surveillance and vaccination policies against pertussis. We compared the epidemiology of this disease in two Ibero-American countries with different vaccination and surveillance policies.

Methods

We compared the epidemiology of pertussis in Spain and the Dominican Republic (DR). We present a 10-year observational study of reported pertussis based on suspected and/or probable cases of pertussis identified by the national mandatory reporting system in both countries between 2005 and 2014. Both countries have a similar case definition for pertussis surveillance, although Spain applies laboratory testing, and uses real time PCR and/or culture for case confirmation while in DR only probable and/or suspected cases are reported. We analyzed incidence, hospitalization, case-fatality rates, mortality and vaccination coverage.

Results

The average annual incidence in children aged <1 year was 3.40/100,000 population in Spain and 12.15/100,000 in DR (p = 0.01). While the incidence in DR was generally higher than in Spain, in 2011 it was six times higher in Spain than in DR. The highest infant mortality in Spain was 0.017/100,000 in 2011, and the highest in DR was 0.08/100,000 in 2014 (p = 0.01). The proportion of hospitalized cases per year among children <1 year varied between 22.0% and 93.7% in Spain, and between 1.1% and 29.4% in DR (p = 0.0002), while mortality varied from 0 to 0.017 and 0 to 0.08 per 100,000 population in Spain and DR, respectively (p = 0.001). Vaccination coverage was 96.5% in Spain and 82.2% in DR (p = 0.001).

Conclusions

Pertussis is a public health problem in both countries. Surveillance, prevention and control measures should be improved, especially in DR. Current vaccination programs are not sufficient for preventing continued pertussis transmission, even in Spain which has high vaccination coverage.

A Bordetella pertussis proteoliposome induces protection in mice without affecting the immunogenicity of diphtheria and tetanus toxoids in a trivalent formulation

In this study, a formulation of Bordetella pertussis proteoliposome (PLBp), diphtheria, and tetanus toxoids and alum (DT-PLBp) was evaluated as a trivalent vaccine candidate in BALB/c mice. Vaccine-induced protection was estimated using the intranasal challenge for pertussis and enzyme-linked immunosorbent assay fvto assess serological responses for diphtheria or tetanus. Both, diphtheria-tetanus-whole cell pertussis (DTP) and diphtheria-tetanus vaccines (DT) were used as controls. Animals immunized with DT-PLBp, PLBp alone, and DTP showed total reduction of CFU in lungs 7 days after intranasal challenge. Likewise, formulations DT-PLBp, DTP, and DT elicited antibody levels ≥2 IU/mL against tetanus and diphtheria, considered protective when neutralization tests are used. Overall, results showed that combination of PLBp with tetanus and diphtheria toxoids did not affect the immunogenicity of each antigen alone.

Predicting future trends in the burden of pertussis in the 21st century: implications for infant pertussis and the success of maternal immunization

Support is growing for maternal immunization using acellular pertussis (aP) vaccines to prevent severe pertussis disease and deaths among very young, unvaccinated infants. Vaccine effectiveness of maternal immunization is 91% in preventing laboratory-confirmed pertussis in infants aged <3 months. To date, most mothers were primed in childhood with whole-cell pertussis vaccines. Soon, the generation of aP-primed individuals will become the new mothers-to-be. The shorter duration of protection afforded by aP vaccines, which is more pronounced with repeated aP boosters, may lead to increased pertussis circulation among aP-primed parents. Maternal Tdap immunization in aP-primed mothers-to-be may become less effective. Additional measures to protect young infants may eventually be needed, along with new vaccines that induce higher quality and more durable responses.

Vaccine Adjuvants: from 1920 to 2015 and Beyond

The concept of stimulating the body’s immune response is the basis underlying vaccination. Vaccines act by initiating the innate immune response and activating antigen presenting cells (APCs), thereby inducing a protective adaptive immune response to a pathogen antigen. Adjuvants are substances added to vaccines to enhance the immunogenicity of highly purified antigens that have insufficient immunostimulatory capabilities, and have been used in human vaccines for more than 90 years. While early adjuvants (aluminum, oil-in-water emulsions) were used empirically, rapidly increasing knowledge on how the immune system interacts with pathogens means that there is increased understanding of the role of adjuvants and how the formulation of modern vaccines can be better tailored towards the desired clinical benefit. Continuing safety evaluation of licensed vaccines containing adjuvants/adjuvant systems suggests that their individual benefit-risk profile remains favorable. Adjuvants contribute to the initiation of the innate immune response induced by antigens; exemplified by inflammatory responses at the injection site, with mostly localized and short-lived effects. Activated effectors (such as APCs) then move to draining lymph nodes where they direct the type, magnitude and quality of the adaptive immune response. Thus, the right match of antigens and adjuvants can potentiate downstream adaptive immune responses, enabling the development of new efficacious vaccines. Many infectious diseases of worldwide significance are not currently preventable by vaccination. Adjuvants are the most advanced new technology in the search for new vaccines against challenging pathogens and for vulnerable populations that respond poorly to traditional vaccines.

Vaccine Adjuvants: from 1920 to 2015 and Beyond

The concept of stimulating the body's immune response is the basis underlying vaccination. Vaccines act by initiating the innate immune response and activating antigen presenting cells (APCs), thereby inducing a protective adaptive immune response to a pathogen antigen. Adjuvants are substances added to vaccines to enhance the immunogenicity of highly purified antigens that have insufficient immunostimulatory capabilities, and have been used in human vaccines for more than 90 years. While early adjuvants (aluminum, oil-in-water emulsions) were used empirically, rapidly increasing knowledge on how the immune system interacts with pathogens means that there is increased understanding of the role of adjuvants and how the formulation of modern vaccines can be better tailored towards the desired clinical benefit. Continuing safety evaluation of licensed vaccines containing adjuvants/adjuvant systems suggests that their individual benefit-risk profile remains favorable. Adjuvants contribute to the initiation of the innate immune response induced by antigens; exemplified by inflammatory responses at the injection site, with mostly localized and short-lived effects. Activated effectors (such as APCs) then move to draining lymph nodes where they direct the type, magnitude and quality of the adaptive immune response. Thus, the right match of antigens and adjuvants can potentiate downstream adaptive immune responses, enabling the development of new efficacious vaccines. Many infectious diseases of worldwide significance are not currently preventable by vaccination. Adjuvants are the most advanced new technology in the search for new vaccines against challenging pathogens and for vulnerable populations that respond poorly to traditional vaccines.

A proteoliposome formulation derived from Bordetella pertussis induces protection in two murine challenge models

Whooping cough remains a health problem despite high vaccination coverage. It has been recommended that development of new strategies provide long-lasting immunity. The aim of this work was to evaluate the potential of proteoliposomes (PL) extracted from Bordetella pertussis as a vaccine candidate against whooping cough. The size of the B. pertussis PL was estimated to be 96.7 ± 50.9 nm by Scanning Correlation Spectroscopy and the polydispersity index was 0.268. Western blots using monoclonal antibodies revealed the presence of pertussis toxin, pertactin, and fimbriae 3. The Limulus Amebocyte Lisate (LAL) assay showed endotoxin levels lower than those reported for whole cell pertussis licensed vaccines, while the Pyrogen Test indicated 75 ng/mL/Kg. The PL showed high protection capacity in mouse challenge models. There was 89.7% survival in the intracerebral challenge and total reduction of the number of CFU in the intranasal challenge. No significant differences (p > 0.05) were observed between mice immunized with B. pertussis PL and the Cuban DTwP vaccine, whichever challenge model used. These results encouraged us to continue the development of the B. pertussis PL as a component of a new combined vaccine formulated with tetanus and diphtheria toxoids or as a booster dose for adolescents and adults.

Emergency department staff and susceptibility to pertussis: a seroprevalence study

OBJECTIVE

To determine the proportion of ED staff who are susceptible to pertussis. There was evidence that some winter leave in southern Tasmania might be a reason of pertussis infection among unimmunized staff. This results in loss of individual earning and loss of availability of staff during the peak demand periods in the ED. There is evidence in the literature that underdiagnosis and undertreatment of pertussis occurs worldwide.

METHODS

All ED staff were approached to participate in this seroprevalence study. A self-completed questionnaire was used to record pervious immunization history for pertussis. Blood samples were collected and analysed to detect and quantify immunoglobulin G and immunoglobulin A titres for pertussis. All confidence intervals (CI) are at 95%.

SETTINGS

The Royal Hobart Hospital and the co-located Hobart Private Hospital.

RESULTS

Ninety-seven of 106 eligible staff took part in the present study, a participation rate of 92% (CI 84-96). Ninety-one of 97 subjects (94%, CI 87-98) believed that they had been immunized for pertussis in childhood; six subjects had either not been immunized or were unsure (6%, CI 2-13). Twenty-three subjects (24%, CI 16-33) had been immunized as adults. There was serologic evidence of recent infection for 21 participants (22%, CI 14-31). Thirty-one participants (32%, CI 23-42) were susceptible to pertussis on the basis of low immunoglobulin G titres.

CONCLUSION

ED staff should routinely be offered booster immunization for pertussis.

Bacillus subtilis spores: a novel microparticle adjuvant which can instruct a balanced Th1 and Th2 immune response to specific antigen

There is a current need for safe, cheap, and effective vaccine adjuvants, to combine with sub-unit antigens to enhance their immunogenicity. In this study we have used probiotic Bacillus subtilis spores, known to be safe and fully tolerated by ingestion in man, and explored their ability to influence the magnitude and diversity of immune responses induced against two model antigens, tetanus toxoid fragment C (TT) and ovalbumin (OVA) in mice. The results show that B. subtilis spores not only increased antibody and T cell responses to a co-administered soluble antigen, but also broadened them, to include both antigen-specific CD4+ and CD8+ T cell responses as well as complement and non-complement fixing antibody isotypes. Furthermore, following intranasal immunization, spores augmented specific IgA to co-administered antigen both in the local respiratory and distal vaginal mucosa, as well as increased antigen-specific IgG antibody in draining LN and blood. Collectively, these data demonstrate that naturally occurring, non-pathogenic, non-commensal spores of B. subtilis both instruct and augment polyvalent immune responses and highlight their clinical potential in future vaccines to generate broad-based immunity.