A cellular pertussis vaccine (Infanrix-DTPa; SB-3). A review of its immunogenicity, protective efficacy and tolerability in the prevention of Bordetella pertussis infection

Protection of mice against experimental cryptococcosis using glucan particle-based vaccines containing novel recombinant antigens

Meningitis due to Cryptococcus neoformans is responsible for upwards of 180,000 deaths worldwide annually, mostly in immunocompromised individuals. Currently there are no licensed fungal vaccines, and even with anti-fungal drug treatment, cryptococcal meningitis is often fatal. Our lab previously demonstrated vaccination with recombinant cryptococcal proteins delivered in glucan particles (GPs) protects mice against an otherwise lethal infection. The aim of the present study was to discover additional cryptococcal antigens affording vaccine-mediated protection. Sixteen proteins, each with evidence of extracellularity, were selected for in vivo testing based on their abundance in protective alkaline extracts of an acapsular C. neoformans strain, their known immunogenicity, and/or their high transcript level during human infection. Candidate antigens were recombinantly expressed in E. coli, purified and loaded into GPs. BALB/c and C57BL/6 mice received three subcutaneous injections of GP-based vaccine, and survival was assessed for 84 days following a lethal orotracheal challenge with strain KN99. As with our six published GP-vaccines, we saw differences in overall protection between mouse strains such that BALB/c mice typically demonstrated better survival than C57BL/6 mice. From these studies, we identified seven new proteins which, when administered as GP-vaccines, protect BALB/c and/or C57BL/6 mice against cryptococcal infection. With these results, we expand the pool of novel protective antigens to eleven proteins and demonstrate the potential for selection of highly transcribed extracellular proteins as vaccine targets. These screens highlight the efficacy of GP-subunit vaccines and identify promising antigens for further testing in anti-cryptococcal, multi-epitope vaccine formulations.

Application of radiation technology in vaccines development

One of the earliest methods used in the manufacture of stable and safe vaccines is the use of chemical and physical treatments to produce inactivated forms of pathogens. Although these types of vaccines have been successful in eliciting specific humoral immune responses to pathogen-associated immunogens, there is a large demand for the development of fast, safe, and effective vaccine manufacturing strategies. Radiation sterilization has been used to develop a variety of vaccine types, because it can eradicate chemical contaminants and penetrate pathogens to destroy nucleic acids without damaging the pathogen surface antigens. Nevertheless, irradiated vaccines have not widely been used at an industrial level because of difficulties obtaining the necessary equipment. Recent successful clinical trials of irradiated vaccines against pathogens and tumors have led to a reevaluation of radiation technology as an alternative method to produce vaccines. In the present article, we review the challenges associated with creating irradiated vaccines and discuss potential strategies for developing vaccines using radiation technology.

Emerging Vaccine Technologies

Vaccination has proven to be an invaluable means of preventing infectious diseases by reducing both incidence of disease and mortality. However, vaccines have not been effectively developed for many diseases including HIV-1, hepatitis C virus (HCV), tuberculosis and malaria, among others. The emergence of new technologies with a growing understanding of host-pathogen interactions and immunity may lead to efficacious vaccines against pathogens, previously thought impossible.

Seroprevalence of diphtheria toxoid IgG antibodies in children, adolescents and adults in Poland

BACKGROUND

Recommendations for diphtheria immunization are to apply an effective primary immunization in infancy and to maintain immunity throughout life. Immunity against diphtheria depends primarily on antibody to the diphtheria toxin. This study evaluated the seroprevalence of IgG diphtheria antitoxin in sera of healthy children, adolescents and adults in Poland.

METHODS

A total of 1387 serum samples collected between 2010 and 2012 from individuals with ages ranging from 1 month to 85 years were investigated. Antibody concentrations were measured with an enzyme-linked immunosorbent assay (Anti-Diphtheria Toxoid ELISA IgG, Euroimmun, Germany).

RESULTS

The results showed that among 1387 individuals examined, 547 (39.4%) had anti-diphtheria toxoid IgG antibody levels below 0.1 IU/ml (36.9% ≤ 18 years and 40.5% >18 years old, respectively). The 212 (50.8%) children and 542 (55.9%) adults showed only basic protection (0.1-1.0 IU/ml) and need immediate booster. High levels of anti-diphtheria toxoid IgG antibodies (>1.0 IU/ml) were found more often in children and adolescent (12.2%) than in adults (3.6%) and this was statistically significant (P < 0.05). The proportion of seronegatives (< 0.1 IU/ml) in children below 2 years old, adolescents and young adults to 25 years old decreased from 53.5% to 17.4%. However, in older individuals the seronegative proportion tended to increase with age, from 22.7% in adults (26-30 years old) to 67.1% in subjects > 60 years old. Characteristically, in individuals > 40 years old high levels of anti-diphtheria toxoid IgG antibodies (>1.0 IU/ml) were not seen. There were no statistically significant differences in results in relation to gender.

CONCLUSIONS

The present study showed inadequate immunity levels to diphtheria amongst the Polish population, especially in adults > 40 years old and children ≤ 2 years old. To prevent reemergence of diphtheria an information campaign reminding people about recommendations concerning diphtheria booster vaccination in adults should be conducted. Moreover, the immunogenicity of the DTP vaccine used in Poland should be verified.

Virulence determinants involved in differential host niche adaptation of Neisseria meningitidis and Neisseria gonorrhoeae

Neisseria meningitidis and Neisseria gonorrhoeae are the only pathogenic species of the genus Neisseria. Although these two species are closely related, they specialized on survival in completely different environments within the human host-the nasopharynx in the case of N. meningitidis versus the urogenital tract in the case of N. gonorrhoeae. The genetic background of these differences has not yet been determined. Here, we present a comparison of all characterized transcriptional regulators in these species, delineating analogous functions and disclosing differential functional developments of these DNA-binding proteins with a special focus on the recently characterized regulator FarR and its contribution to divergent host niche adaptation in the two Neisseria spp. Furthermore, we summarize the present knowledge on two-partner secretion systems in meningococci, highlighting their overall expression among meningococcal strains in contrast to the complete absence in gonococci. Concluding, the decisive role of these two entirely different factors in host niche adaptation of the two human pathogenic Neisseria species is depicted, illuminating another piece of the puzzle to locate the molecular basis of their differences in preferred colonization sites and pathogenicity.

A functional two-partner secretion system contributes to adhesion of Neisseria meningitidis to epithelial cells

Neisseria meningitidis is a frequent commensal of the human nasopharynx causing severe invasive infections in rare cases. A functional two-partner secretion (TPS) system in N. meningitidis, composed of the secreted effector protein HrpA and its cognate transporter HrpB, is identified and characterized in this study. Although all meningococcal strains harbor at least one TPS system, the hrpA genes display significant C-terminal sequence variation. Meningococcal genes encoding the TPS effector proteins and their transporters are closely associated and transcribed into a single mRNA. HrpA proteins are translocated across the meningococcal outer membrane by their cognate transporters HrpB and mainly released into the environment. During this process, HrpA is proteolytically processed to a mature 180-kDa form. In contrast to other known TPS systems, immature HrpA proteins are stable in the absence of HrpB and accumulate within the bacterial cell. A small percentage of mature HrpA remains associated with the bacteria and contributes to the interaction of meningococci with epithelial cells.

DTPa-HBV-IPV/Hib vaccine (Infanrix hexa)

Primary vaccination of infants with diphtheria-tetanus-acellular pertussis-hepatitis B recombinant (adsorbed)-inactivated poliomyelitis-adsorbed conjugated Haemophilus influenzae type b vaccine (DTPa-HBV-IPV/Hib; Infanrix hexa)-inactivated poliomyelitis-absorbed conjugated Haemophilus influenzae type b vaccine (DTPa-HBV-IPV/Hib) refers to Infanrix hexa trade mark.) provided high levels of seroprotection against diphtheria toxoid, tetanus toxoid, poliovirus 1, 2 and 3, pertussis antigens (pertussis toxoid, filamentous haemagglutinin and pertactin), hepatitis B virus surface antigen and H. influenzae polyribosyl-ribitol-phosphate (PRP) antigen. Most infants (97%) had anti-PRP levels >/=0.15 micro g/mL after a booster dose at 18 months. Primary vaccination with the DTPa-HBV-IPV/Hib vaccine produced a similar immune response to that with two different pentavalent plus monovalent vaccine combinations. Coadministration of DTPa-HBV-IPV/Hib vaccine and a heptavalent pneumonococcal conjugate vaccine resulted in a high level of seroprotection and was well tolerated. Primary or booster vaccination with DTPa- HBV-IPV/Hib vaccine was well tolerated. Commonly reported local adverse reactions included redness, pain and swelling. Systemic symptoms were usually mild to moderate, and included fussiness, fever, restlessness and sleepiness.

Development and clinical testing of multivalent vaccines based on a diphtheria-tetanus-acellular pertussis vaccine: difficulties encountered and lessons learned

The widespread use of whole-cell pertussis vaccines in the second half of the 20th century have reduced the incidence of the disease significantly. However, in some countries, concerns about the reactogenicity and potential neurological damage associated with whole-cell vaccines led to a decrease in vaccine acceptance and an increase in morbidity and mortality of pertussis in several countries. This prompted the development of less reactogenic acellular pertussis vaccines combined with diphtheria and tetanus toxoids, initially in Japan and later in other countries. In Europe, the improved diphtheria, tetanus and acellular pertussis (DTPa) vaccine was first introduced in March 1994. The pertussis component of this DTPa vaccine, developed by Glaxo SmithKline, consists of pertussis toxoid, filamentous haemagglutinin and pertactin. The vaccine is well tolerated, with a lower incidence of adverse reactions than after administration of whole-cell vaccines. The long-lasting efficacy and effectiveness of DTPa vaccines have been extensively documented and these are now the cornerstone of a large range of combined vaccines including DTPa-hepatitis B (HBV), DTPa-inactivated polio (IPV) and DTPa-HBV-IPV. A lyophilised Haemophilus influenzae type b (Hib) vaccine can be reconstituted with all of these liquid combinations. The introduction of well-tolerated and efficacious DTPa vaccines and their more polyvalent combinations has improved the acceptance and simplified the implementation of childhood immunisation. This paper is a review of the technical and scientific difficulties encountered and the lessons learned over the 10-year period that it took to develop and introduce six multivalent vaccines using the Glaxo SmithKline DTPa as a building block.

Which strategy for pertussis vaccination today?

Pertussis (whooping cough) remains an epidemic disease responsible for infant and child morbidity and mortality, and is perceived as a serious public health problem. Since the widespread use of whole-cell pertussis vaccines in the 1940s, vaccination programs have varied greatly between countries. National specificity is a function of several factors. The most important are: vaccine efficacy and tolerability;vaccine coverage and distribution; and vaccine acceptance by parents and professionals. During the 1970s, Sweden, England, Wales and Japan provided contrasting examples of the attitude of health authorities to the use of whole-cell vaccines. The increase in pertussis incidence was noted as a consequence of active opposition to this vaccine. The re-emergence of pertussis in the 1990s, in countries with high vaccination coverage and increased incidence of disease in individuals >15 years and <6 months of age, has drawn attention to the role of booster doses of pertussis vaccines and their introduction into regular vaccination programs. The use of acellular vaccines for booster doses for adolescents and adults would seem unambiguous because of their decreased reactogenicity, although the exact schedule has yet to be established. The choice between the two kinds of vaccines is more difficult for primary courses, where safety and efficacy profiles are similar, and the attitude towards acellular vaccines varies from country to country. In this case, the strategy adopted results from the national history of pertussis infection and from the quality of the available whole-cell vaccine. Two contrasting examples are the US, where acellular vaccines were licensed for the primary series in the 1990s, and the UK, where whole-cell vaccines are exclusively used for primary immunization. The changing epidemiology of pertussis, and its local diversification, would suggest that at present it is difficult to define a single worldwide strategy with only one kind of vaccine and one schedule. In order to control pertussis incidence, each country should continue to determine the best national vaccination program established in very close relation to the past and present epidemiological situation and available healthcare resources.

Interchangeability of 2 diphtheria-tetanus-acellular pertussis vaccines in infancy

OBJECTIVE

Currently, 4 diphtheria-tetanus-acellular pertussis (DTaP) vaccines are licensed for pediatric use in the United States, and 2 are commercially available. Although a single manufacturer's DTaP vaccine should be used for all 3 doses of the primary immunization series, some circumstances result in infants receiving DTaP vaccines from more than 1 manufacturer. The purpose of this study was to evaluate the safety and immunogenicity of a mixed sequence of 2 different DTaP vaccines.

METHODS

In this multicenter, observer-blinded, controlled study, 449 infants were randomized into 1 of 3 groups (1:1:1 ratio) to receive Tripedia at 2, 4, and 6 months of age (control group); Tripedia at 2 and 4 months of age and Infanrix at 6 months of age; or Tripedia at 2 months and Infanrix at 4 and 6 months of age. Other vaccines were administered concurrently as separate injections according to the recommended childhood immunization schedule. Safety was monitored closely, and standard enzyme immunoassays were used to measure antibody concentrations to each antigen of the DTaP vaccines.

RESULTS

The rates of injection-site and systemic adverse events were similar in each study group, and there were no clinically significant differences among groups after any dose. Infants in all 3 groups responded well to each antigen contained in both vaccines, with 97% to 100% seroprotection or vaccine response rates after the 3-dose primary series. Postvaccination geometric mean antibody concentrations and seroprotection or vaccine response rates to nearly all vaccine antigens were as high or higher in the mixed-sequence groups as in the control group.

CONCLUSION

Initiating the primary immunization series with 1 or 2 doses of Tripedia and completing the 3-dose series with Infanrix is as safe and at least as immunogenic as administering Tripedia for all 3 doses.

Diphtheria-tetanus-acellular pertussis vaccine adsorbed (Triacelluvax; DTaP3-CB): a review of its use in the prevention of Bordetella pertussis infection

DTaP3-CB (Triacelluvax) is an acellular pertussis (aP) vaccine containing 3 antigens from purified Bordetella pertussis bacteria combined with diphtheria and tetanus toxoids (DT). In addition to purified filamentous haemagglutinin and pertactin, DTaP3-CB contains pertussis toxin which has been genetically rather than chemically detoxified. As shown in randomised, double-blind clinical trials in infants, DTaP3-CB elicits an immune response similar to or greater than that of whole cell (DTwP) vaccines. Results of a large multicentre study comparing DTaP3-CB with 12 acellular and 1 DTwP vaccine indicate that DTaP3-CB, like all acellular vaccines, induces variable immune responses to different pertussis antigens; however, antibody titres to pertussis toxin are normally higher after immunisation with the genetically detoxified vaccine than with other 3- or 4-component vaccines. When given as a fourth or fifth booster dose, DTaP3-CB produced a significant immune response in infants primed with 3 doses of either a DTaP or DTwP vaccine. Virtually all infants immunised with DTaP3-CB had a serological response to diphtheria and tetanus toxoids. Data from 2 very large efficacy studies indicate that DTaP3-CB has high and long lasting protective efficacy against culture-confirmed pertussis which is greater than that of a 2-component vaccine (DTaP2-SB) and the whole cell DTwP-CON vaccine after a 3-, 5- and 12-month immunisation schedule and after a 2-, 4- and 6-month schedule with the DTwP-CON vaccine. However, the DTwP-CON whole cell vaccine has been noted for its low immunogenicity in 1 study and low efficacy and immunogenicity in another study. On the other hand, DTaP3-CB vaccine has similar efficacy to DTaP3-SB (after immunisation at 2, 4 and 6 months), DTaP5-CON and DTwP-EVANS against culture-confirmed pertussis with > or =21 days cough in infants immunised according to a 3-, 5- and 12-month schedule. Infants immunised with DTaP3-CB experienced significantly fewer adverse events such as pain, redness, swelling and irritability than infants given DTwP. DTaP3-CB has a similar tolerability profile to other acellular vaccines and is associated with similar rates of local tenderness, irritability, fever (> or =40 degrees C) and persistent crying. Comparative trials have shown that infants immunised with DTaP3-CB had a lower incidence of pain at the site of injection and fever (> or =38 degrees C) compared with other acellular vaccines, although this may have little clinical significance. Concomitant administration of DTaP3-CB with hepatitis B, oral polio or Haemophilus influenzae type B vaccines did not affect the immunogenicity of these other paediatric vaccines.

CONCLUSION

Data from clinical trials with DTaP3-CB vaccine indicate that this vaccine induces high and long lasting efficacy. It is at least as efficacious as most whole cell vaccines and generally similar in efficacy to the most efficacious acellular pertussis vaccines containing 3 or more pertussis antigens. DTaP3-CB is better tolerated than whole cell vaccines and has a similar tolerability profile to other acellular vaccines; the possible lower risk of severe adverse events remains to be confirmed. The low reactogenicity of DTaP3-CB is likely to make it well tolerated and therefore well accepted for the immunisation of infants, thereby enabling wider implementation of vaccination programmes.