Effect of inactivated poliovirus vaccine on the antibody response to Bordetella pertussis antigens when combined with diphtheria-pertussis-tetanus vaccine

Low-dose Thimerosal in pediatric vaccines: Adverse effects in perspective

Vaccines are prophylactics used as the first line of intervention to prevent, control and eradicate infectious diseases. Young children (before the age of six months) are the demographic group most exposed to recommended/mandatory vaccines preserved with Thimerosal and its metabolite ethylmercury (EtHg). Particularly in the less-developed countries, newborns, neonates, and young children are exposed to EtHg because it is still in several of their pediatric vaccines and mothers are often immunized with Thimerosal-containing vaccines (TCVs) during pregnancy. While the immunogenic component of the product has undergone more rigorous testing, Thimerosal, known to have neurotoxic effects even at low doses, has not been scrutinized for the limit of tolerance alone or in combination with adjuvant-Al during immaturity or developmental periods (pregnant women, newborns, infants, and young children). Scientific evidence has shown the potential hazards of Thimerosal in experiments that modeled vaccine-EtHg concentrations. Observational population studies have revealed uncertainties related to neurological effects. However, consistently, they showed a link of EtHg with risk of certain neurodevelopment disorders, such as tic disorder, while clearly revealing the benefits of removing Thimerosal from children's vaccines (associated with immunological reactions) in developed countries. So far, only rich countries have benefited from withdrawing the risk of exposing young children to EtHg. Regarding Thimerosal administered to the very young, we have sufficient studies that characterize a state of uncertainty: the collective evidence strongly suggests that Thimerosal exposure is associated with adverse neurodevelopmental outcomes. It is claimed that the continued use of Thimerosal in the less-developed countries is due to the cost to change to another preservative, such as 2-phenoxyethanol. However, the estimated cost increase per child in the first year of life is lower than estimated lifetime cost of caring for a child with a neurodevelopmental disorder, such tic disorder. The evidence indicates that Thimerosal-free vaccine options should be made available in developing countries.

Adsorption of Toll-Like Receptor 4 Agonist to Alum-Based Tetanus Toxoid Vaccine Dampens Pro-T Helper 2 Activities and Enhances Antibody Responses

Aluminum salts gels (alum) are TLR-independent adjuvants and have been used to boost antibody responses in alum-based vaccines such as diphtheria, pertussis, and tetanus toxoid (DPT) triple vaccine. However, the pro-Th2 activity of alum-based vaccine formulations has not been fully appreciated. Here we found that alum-based tetanus toxoid (TT) vaccine was biased toward a Th-2 profile as shown by TT-induced airway eosinophilic inflammation, type 2 cytokine production, and high levels of IgE anaphylactic antibodies. The adsorption into alum of prototypic TLR4 agonists such as lipopolysaccharides (LPS) derived from Escherichia coli consistently dampened TT-induced Th2 activities without inducing IFNγ or Th1-like responses in the lung. Conversely, adsorption of monophosphoryl lipid A (MPLA) extracted from Salmonella minnesota, which is a TIR-domain-containing adapter-inducing interferon-β- (TRIF-) biased TLR4 agonist, was less effective in decreasing Th-2 responses. Importantly, in a situation with antigenic competition (OVA plus TT), TT-specific IgG1 or IgG2a was decreased compared with TT sensitization. Notably, LPS increased the production of IgG1 and IgG2a TT-specific antibodies. In conclusion, the addition of LPS induces a more robust IgG1 and IgG2a TT-specific antibody production and concomitantly decreases Th2-cellular and humoral responses, indicating a potential use of alum/TLR-based vaccines.

Immunogenicity of individual vaccine components in a bivalent nicotine vaccine differ according to vaccine formulation and administration conditions

Structurally distinct nicotine immunogens can elicit independent antibody responses against nicotine when administered concurrently. Co-administering different nicotine immunogens together as a multivalent vaccine could be a useful way to generate higher antibody levels than with monovalent vaccines alone. The immunogenicity and additivity of monovalent and bivalent nicotine vaccines was studied across a range of immunogen doses, adjuvants, and routes to assess the generality of this approach. Rats were vaccinated with total immunogen doses of 12.5 - 100 μg of 3′-aminomethyl nicotine conjugated to recombinant Pseudomonas exoprotein A (3′-AmNic-rEPA), 6-carboxymethylureido nicotine conjugated to keyhole limpet hemocyanin (6-CMUNic-KLH), or both. Vaccines were administered s.c. in alum or i.p. in Freund’s adjuvant at matched total immunogen doses. When administered s.c. in alum, the contributions of the individual immunogens to total nicotine-specific antibody (NicAb) titers and concentrations were preserved across a range of doses. Antibody affinity for nicotine varied greatly among individuals but was similar for monovalent and bivalent vaccines. However when administered i.p. in Freund’s adjuvant the contributions of the individual immunogens to total NicAb titers and concentrations were compromised at some doses. These results support the possibility of co-administering structurally distinct nicotine immunogens to achieve a more robust immune response than can be obtained with monovalent immunogens alone. Choice of adjuvant was important for the preservation of immunogen component activity.

Enhanced immunogenicity of a bivalent nicotine vaccine

The efficacy of nicotine vaccines for smoking cessation is dependent upon their ability to elicit sufficiently high serum antibody concentrations. This study compared two nicotine immunogens representing different hapten presentations, 3'-aminomethyl nicotine conjugated to recombinant Pseudomonas exoprotein A (3'-AmNic-rEPA) and 6-carboxymethlureido nicotine conjugated to keyhole limpet hemocyanin (6-CMUNic-KLH), and assessed whether their concurrent administration would produce additive serum antibody concentrations in rats. Effects of vaccination on nicotine pharmacokinetics were also studied. Vaccination of rats with these immunogens produced non cross-reacting nicotine-specific antibodies (NicAb). Serum NicAb concentrations elicited by each individual immunogen were not affected by whether the immunogens were administered alone as monovalent vaccines or together as a bivalent vaccine. The total NicAb concentration in the bivalent vaccine group was additive compared to that of the monovalent vaccines alone. Higher serum NicAb concentrations, irrespective of which immunogen elicited the antibodies, were associated with greater binding of nicotine in serum, a lower unbound nicotine concentration in serum, and lower brain nicotine concentration. These results demonstrate that it is possible to design immunogens which provide distinct nicotine epitopes for immune presentation, and which produce additive serum antibody levels. The concurrent administration of these immunogens as a bivalent vaccine may provide a general strategy for enhancing the antibody response to small molecules such as nicotine.

Combination Vaccines

Infections are still a leading cause of morbidity and mortality in children under five years of age, most of which can be prevented by vaccination. However, there are too many vaccines to be administered, increasing the cost of immunization and visits to the paediatrician. Combination vaccines can be an answer to these problems till the development of a single vaccine containing all the possible antigens. Researchers are aiming at development of an ideal vaccine, which can be given orally at birth, has negligible side effects, is heat stable and is affordable to all the parents.

On technological and immunological benefits of multivalent single-injection microsphere vaccines

PURPOSE

With the aim of developing multivalent vaccines for single-injection, we examined the feasibility of combining antigens in biodegradable microspheres. Such vaccines are expected to improve vaccination coverage by reducing the number of vaccination sessions required to generate immunity.

METHODS

Mono- and multivalent vaccines of Haemophilus influenzae type b (Hib) conjugate, diphtheria toxoid (DT), tetanus toxoid (TT), and pertussis toxin (PT) in poly (lactic acid) and poly(lactic-coglycolic acid) microspheres were prepared by spray drying, and the influence of coencapsulated antigens and excipients on antigen loading, release, and stability was examined. Two tetravalent formulations were tested in guinea pigs.

RESULTS

Monovalent Hib and PT vaccines showed loading efficiencies of 10% (Hib) and 30% (PT) in both polymers. The loading efficiencies increased upon addition of trehalose and, even more, when the antigens were coencapsulated in di- and trivalent combinations. Highest loading efficiencies (> 80%) were achieved with trivalent formulations (DT + PT + Hib) that also contained coencapsulated albumin. The percentage of antigen released during 24 h of incubation was typically 10-40% and decreased as loading efficiency increased. Enzyme-linked immunosorbent assay (ELISA) data revealed that TT, DT, and PT remained antigenic throughout the encapsulation and subsequent release processes. Finally, all antigens maintained their immunogenicity, since strong and sustained antibody responses were elicited after a single injection of tetravalent microsphere vaccines (DT + TT + PT + Hib) in guinea pigs.

CONCLUSIONS

This study reveals technologic benefit as well as an immunological potential of multivalent single-injection microsphere vaccines. The results support our hypothesis that coencapsulation of several antigens may intrinsically improve entrapment of antigenic and immunogenic antigen probably by virtue of increased protein concentration during microencapsulation leading to mutual stabilization of the components.

Combination vaccines

The biotechnology revolution has stimulated vaccine development, blessing us with new, safe, and effective vaccines, but burdening our vaccination schedule. The incorporation of multiple individual vaccines into combination vaccines can simplify vaccine administration programs and permit the inclusion of new antigens in the vaccine schedule. Although the development, evaluation, and implementation of combination vaccines pose numerous challenges and raise controversies that remain unresolved, there is a reasonable prospect of United States licensure within the next few years of several new combination vaccines for infant use. Approval in the United States of combination vaccines in use elsewhere might be speeded by improved vaccination tracking systems and post marketing efficacy surveillance, which would provide confidence that material reductions in efficacy could be detected following licensure, and thereby ease concerns regarding moderate, but perhaps immaterial, declines in immunogenicity seen with some combinations.

Combination vaccines

The past decade has shown a marked increase in the number of vaccines currently licensed and recommended for use in infants and children. Although most agree that it is desirable to combine as many of these vaccines as possible into a single injection, safety and efficacy must not be sacrificed. Clearly, a resurgence in Hib meningitis or measles (for example) would not be an acceptable price for the convenience of a single injection; but it is not clear how large a reduction in immunogenicity can be incurred without paying such a price. This conundrum has slowed the licensure of useful combination vaccines, despite a consensus that parents and practitioners have reached a limit to the number of injections they will deliver to young children. We anticipate US licensure for infant use of (at least) one DTaP-IPV-Hib vaccine and one DTaP-IPV-HB vaccine within the next few years, given the apparent lack of material reduction in immunogenicity of these specific combination products. Licensure in the United States of some of the other combinations now used in Europe is also possible, given supporting national surveillance data or improvements in our understanding of the correlates of immunity. Enhanced vaccination tracking systems and postmarketing efficacy surveillance should provide confidence that material reductions in efficacy could be detected following licensure, and thereby ease the approval of combinations that result in moderate, but perhaps immaterial, declines in immunogenicity.

Diminution of the anti-polyribosylribitol phosphate response to a combined diphtheria-tetanus-acellular pertussis/Haemophilus influenzae type b vaccine by concurrent inactivated poliovirus vaccination

BACKGROUND

Prelicensure studies of Haemophilus influenzae type b vaccines (Hib) and diphtheria-tetanus-acellular pertussis vaccines (DTaP) were evaluated with concurrent oral poliovirus vaccine (OPV). However, inactivated poliovirus vaccine (IPV) is now recommended. A trial was conducted in which infants received a DTaP and Hib vaccine, separately (+) or combined (/), with either all OPV, all IPV or sequential IPV-OPV for the primary series of vaccinations.

METHODS

In this protocol 567 infants were equally randomized to receive one of the following: Reference Arm A, DTaP + Hib + OPV; Treatment Arm B, DTaP/Hib + OPV; Treatment Arm C, DTaP/Hib + IPV at 2 and 4 months and OPV at 6 months; or Treatment Arm D, DTaP/Hib + IPV. antibodies against all administered antigens were measured at 7 months of age. Children with an antibody response to Hib (anti-polyribosylribitol phosphate (anti-PRP) <0.15 microg/ml had an antibody titer repeated after the toddler booster immunization.

RESULTS

A significant diminution in the anti-PRP response was observed at 7 months of age in children given two or three doses of IPV concurrently with DTaP/Hib, compared with the groups given OPV. The geometric mean concentration of anti-PRP, percentage of children with > or = 0.15 microg/ml and percentage of children with > or = 1.0 microg/ ml, respectively, were: A, 4.4, 98%, 81%; B, 3.2, 94%, 78%; C, 1.3, 86%, 58% and D, 1.2, 84%, 53%.

CONCLUSION

In this trial concurrent IPV appeared to interfere with the anti-PRP response to DTaP/Hib vaccine, suggesting that introduction of new vaccines may require evaluation of immune responses to all concurrently administered vaccines.

New combination vaccines

Physicians can achieve full vaccination at each of the recommended visits by administering three or four injections, but for infants, four injections seem to be a maximum in light of the size of the infant thigh, which is the preferred injection site. Thus, physicians must make room for all of the new vaccines on the horizon. To accomplish that task, combinations will be necessary. Progress toward that goal is occurring.

Safety and immunogenicity of two inactivated poliovirus vaccines in combination with an acellular pertussis vaccine and diphtheria and tetanus toxoids in seventeen- to nineteen-month-old infants

OBJECTIVES

To compare the safety and immunity of an acellular pertussis vaccine containing pertussis toxoid, filamentous hemagglutinin, 69 kd protein, fimbriae 2 and 3 combined with diphtheria and tetanus toxoids given as single or separate injection with inactivated poliovirus vaccine (MRC-5-or Vero cell-derived) or live attenuated polio vaccine.

METHODS

A total of 425 healthy children between 17 and 19 months of age who were receiving the fourth dose of their routine immunization series were randomly allocated to receive either the acellular pertussis vaccine and oral poliovirus vaccine or one of two inactivated poliovirus vaccines as a combined injection or separate injections.

RESULTS

Although minor adverse events were commonly reported, differences between the groups were few. Fever and decreased feeding were less common in recipients of live attenuated poliovirus vaccine than the combination vaccine containing MRC-5 cell-derived inactivated poliovirus vaccine. A significant antibody response was demonstrated in all groups against all the antigens contained in the vaccines. Antibodies against poliovirus were higher in the groups immunized with the inactivated poliovirus vaccine than the live attenuated vaccine. Anti-69 kd protein antibodies were higher in the group given the MRC-5 cell-derived inactivated poliovirus vaccine as a combined injection than in the group given the separate injection or the group immunized with the live attenuated poliovirus vaccine.

CONCLUSION

The five-component acellular pertussis vaccine combined with diphtherid and tetanus toxoids is safe and immunogenic when combined with either MRC-5- or Vero cell-derived inactivated poliovirus vaccine. This will facilitate the implementation of acellular pertussis vaccine and the movement to inactivated poliovirus vaccine programs.

Safety and immunogenicity of an acellular pertussis diphtheria tetanus vaccine given as a single injection with Haemophilus influenzae b conjugate vaccine

To determine if an acellular pertussis-diphtheria-tetanus vaccine could be combined with a Haemophilus influenzae b conjugate vaccine as a single injection, we randomized 468 children between 17 and 21 months of age previously immunized with three doses of each vaccine to receive a five-component acellular pertussis vaccine combined with diphtheria and tetanus toxoids, and Haemophilus influenzae b-tetanus toxoid conjugate vaccine either as separate injections on separate days, separate injections on the same day, or as a single combined injection. Rates of adverse reactions were similar amongst the groups except for increased injection site tenderness (29.2% vs 17%, RR 1.76, 95% CI 1.09-2.85) and fussiness (36.4% vs 23.3%, RR 1.59, 95% CI 1.05-2.41) in the group given the combined injection rather than separate injections on separate days. Antibody levels against the capsular polysaccharide of H. influenzae b after the single combined injection (47.1 micrograms ml-1) were lower than after separate injections on the same day (66.0 micrograms ml-1; P < 0.05) but higher than when the injections were administered on separate days (28.4 micrograms ml-1; P < 0.001). We conclude that the five-component acellular pertussis vaccine is safe and immunogenic when combined with diphtheria and tetanus toxoids and H. influenzae b-tetanus toxoid conjugate vaccine in children receiving the fourth dose of the immunization series.