The immunogenicity and reactogenicity profile of a candidate hepatitis B vaccine in an adult vaccine non-responder population

A controlled clinical trial comparing the safety and immunogenicity of a new adjuvanted hepatitis B vaccine with a standard hepatitis B vaccine

A randomised trial was conducted in 285 adults not immune to hepatitis B (HB) to compare the safety and immunogenicity of a commercial aluminium-adjuvanted HB vaccine with and without an additional new adjuvant (AgB/RC-210-04 or AgB study groups, respectively). The additional adjuvant RC-529 is a fully synthetic monosaccharide mimetic of monophosphoryl lipid A. Subjects in the AgB/RC-210-04 (n=136) and AgB (n=149) groups were vaccinated intramuscularly on days 0, 30, and 180, according to the standard vaccination schedule for hepatitis B vaccines. Serum levels of anti-HBs were measured on days 30, 60, 90, 180, and 210. Standard safety assessments were made throughout the study period. The rates of seroprotection (anti-HBs > or =10.0 mIU/ml) were significantly greater for the AgB/RC-210-04 group at all time points: at day 90, the seroprotection rate, the primary endpoint of the trial, was 99% for AgB/RC-210-04 compared with 84% for AgB (p<0.0001). Similarly, geometric mean anti-HBs titres were significantly higher at all time points for the AgB/RC-210-04 group. There were more local reactions in the AgB/RC-210-04 group, however they were transient and this double-adjuvanted formulation was well tolerated. We conclude that the addition of a synthetic adjuvant to the AgB vaccine significantly enhanced the immunogenicity of the commercial vaccine AgB. The results indicate furthermore that a two-dose regime of the double-adjuvanted vaccine (schedule: 0-1 month) may be sufficient to achieve seroprotection in nearly 100% of individuals.

Sustained efficacy up to 4.5 years of a bivalent L1 virus-like particle vaccine against human papillomavirus types 16 and 18: follow-up from a randomised control trial

BACKGROUND

Effective vaccination against HPV 16 and HPV 18 to prevent cervical cancer will require a high level of sustained protection against infection and precancerous lesions. Our aim was to assess the long-term efficacy, immunogenicity, and safety of a bivalent HPV-16/18 L1 virus-like particle AS04 vaccine against incident and persistent infection with HPV 16 and HPV 18 and their associated cytological and histological outcomes.

METHODS

We did a follow-up study of our multicentre, double-blind, randomised, placebo-controlled trial reported in 2004. We included women who originally received all three doses of bivalent HPV-16/18 virus-like particle AS04 vaccine (0.5 mL; n=393) or placebo (n=383). We assessed HPV DNA, using cervical samples, and did yearly cervical cytology assessments. We also studied the long-term immunogenicity and safety of the vaccine.

FINDINGS

More than 98% seropositivity was maintained for HPV-16/18 antibodies during the extended follow-up phase. We noted significant vaccine efficacy against HPV-16 and HPV-18 endpoints: incident infection, 96.9% (95% CI 81.3-99.9); persistent infection: 6 month definition, 94.3 (63.2-99.9); 12 month definition, 100% (33.6-100). In a combined analysis of the initial efficacy and extended follow-up studies, vaccine efficacy of 100% (42.4-100) against cervical intraepithelial neoplasia (CIN) lesions associated with vaccine types. We noted broad protection against cytohistological outcomes beyond that anticipated for HPV 16/18 and protection against incident infection with HPV 45 and HPV 31. The vaccine has a good long-term safety profile.

INTERPRETATION

Up to 4.5 years, the HPV-16/18 L1 virus-like particle AS04 vaccine is highly immunogenic and safe, and induces a high degree of protection against HPV-16/18 infection and associated cervical lesions. There is also evidence of cross protection.

Immunogenicity and safety of an adjuvanted hepatitis B vaccine in pre-hemodialysis and hemodialysis patients

BACKGROUND

Due to their impaired immune system, patients with renal insufficiency have a suboptimal response to hepatitis B (HB) vaccination and frequent boosters are needed to maintain protection. GlaxoSmithKline Biologicals has developed a HB vaccine containing a new adjuvant system AS04 for use in this immunocompromised patient population.

METHODS

In an open, randomized clinical trial conducted in pre-hemodialysis (documented creatinine clearance < or =30 mL/min) and hemodialysis patients, over 15 years of age and naïve for HB, the immunogenicity and safety of single doses of HB-AS04 (Fendrix, GlaxoSmithKline Biologicals) were compared to double doses of commercially available HB vaccine (Engerix, GlaxoSmithKline Biologicals) administered at 0, 1, 2, and 6 months, and followed-up for 36 months.

RESULTS

The HB-AS04 vaccine elicited a more rapid onset of protection than the currently licensed vaccine for this particular population, with 74% versus 52% of subjects seroprotected at month 3. After the vaccination course, seroprotection rates increased to 91% versus 84% in the HB-AS04 and standard vaccine groups, respectively. Differences persisted up to 36 months post-vaccination (73% vs. 52%, respectively). Antibody concentrations were higher following the HB-AS04 vaccine at all post-vaccination time points. During the follow-up, significantly fewer subjects primed with the HB-AS04 vaccine needed a booster dose as a consequence of anti-HBs loss below seroprotective levels (11/62 subjects in the HB-AS04 group vs. 22/57 subjects in the standard vaccine group, respectively, P = 0.014). The HB-AS04 was more locally reactogenic than the standard immunization regimen, with pain at the injection site occurring with 41% of HB-AS04 doses versus 19% of standard vaccine doses. The occurrence of grade 3 pain was less than 1% in both groups and all events resolved within the 4-day follow-up period.

CONCLUSION

The improved immunogenicity profile and clinically acceptable reactogenicity of HB-AS04 vaccine are of key importance to provide a more rapid, enhanced, and longer seroprotection to these immunocompromised patients at risk for HB infection.

Vaccinology at the beginning of the 21st century

Today, the main challenges for vaccinologists include improving vaccines against as yet undefeated pathogens, rapid identification and response to emerging diseases and successful intervention in chronic diseases in which ongoing immune responses are insufficient. Reverse genetics and reverse vaccinology are now used to generate rapidly new vaccine strains and to mine whole genomes in the search for promising antigens. The rational design of adjuvants has become possible as a result of the discovery of the receptors that recognize microbial patterns and lead to dendritic cell activation. Antigen-loaded dendritic cells, DNA in naked, formulated or viral form, and other delivery systems are used to maximize immune responses. Although work on the ‘easy’ vaccines has already been completed, it is hoped that a combination of conceptual and technical innovation will enable the development of more complex and sophisticated vaccines in the future.

Prevention of hepatitis B in nonresponders to initial hepatitis B virus vaccination

Although vaccination against hepatitis B virus (HBV) is highly successful, 5% to 10% of individuals do not experience a response with an adequate antibody level to hepatitis B surface antigen (anti-HBs). Contributing causes for nonresponse to the vaccine are genetic predisposition, immunosuppression, and certain chronic illnesses. The distinction between true nonresponse (after adequate immunization) and waning anti-HBs levels is important. The latter is not uncommon in populations in areas of the world with low endemicity for HBV infection. Data from subjects with waning anti-HBs levels show that immunologic memory may still protect these individuals against acute HBV infection or may prevent chronic infection with HBV for < or =10 years after immunization. Recent reports from Asia and Alaska describe cases of chronic HBV infection 15 years after immunization in subjects who have very low levels of anti-HBs. Thus, nonresponders or those with waning immunity who may be at risk of HBV infection in subsequent years may require a booster dose. Clinical algorithms to reimmunize nonresponders have been described and are discussed in this article. Experimental hepatitis B vaccines have shown some promise in nonresponders but are not commercially available in the United States.

CPG 7909 adjuvant improves hepatitis B virus vaccine seroprotection in antiretroviral-treated HIV-infected adults

BACKGROUND

HIV patients are vaccine hyporesponsive.

METHODS

We evaluated CPG 7909, a synthetic oligodeoxynucleotide containing immunostimulatory CpG motifs, as an adjuvant to Engerix-B. A randomized, double-blind controlled trial was conducted to determine safety and hepatitis B virus (HBV) immunogenicity in adult HIV subjects on effective antiretroviral therapy. HBV-susceptible subjects, half of whom had failed previous vaccination, were vaccinated at 0, 1 and 2 months with a double dose of Engerix-B with/without (+/-) 1 mg CPG 7909. HBV immune subjects (anti-HBsAg titres > or = 10 mIU/l) received either CPG 7909 alone or saline. Safety, anti-HBs titres and lymphocyte proliferation response (LPR) to HBsAg were assessed over 12 months.

RESULTS

Vaccinations with Engerix B +/- CPG 7909 were well tolerated locally and systemically. HIV suppression and CD4 cell counts were maintained. Anti-HBs titers were significantly higher in vaccinees receiving CPG 7909, for all time points after the second dose. Seroprotective titres (> or = 10 mIU/ml) by 6 and 8 weeks, and 12 months were found in 89, 89, and 100% of subjects receiving CPG 7909 compared to 53, 42, and 63% of controls respectively (P = 0.029, 0.005, and 0.008). HBsAg LPR was increased at all time-points up to 12 months after vaccination with addition of CPG 7909 (P < 0.05).

CONCLUSIONS

Addition of CPG 7909 achieves rapid, higher, and sustained HBV seroprotection and increases HBV-specific T helper cell response to HBV vaccine in HIV subjects. These results confirm a potential adjuvant role for CPG 7909 in vaccine hyporesponsive populations including those living with HIV.

PyNTTTTGT prototype oligonucleotide IMT504 is a potent adjuvant for the recombinant hepatitis B vaccine that enhances the Th1 response

PyNTTTTGT oligodeoxinucleotides (ODNs) cause activation, proliferation and immunoglobulin secretion on B cells, and the expression of co-stimulatory molecules on plasmacytoid dendritic cells of primates. It has now been discovered that these ODNs are also active on rat cells. This fact allowed us to investigate the adjuvant properties of PyNTTTTGT ODNs in a human Hepatitis B vaccine using this animal model. A very significant increment, as compared with the antigen alone, was observed in the antibody production induced by vaccination with the recombinant Hepatitis B surface antigen adjuvated with the PyNTTTTGT prototype IMT504 ODN. Analysis of the IgG subclass distribution in the sera of vaccinated animals indicated that, although an increase was observed in the titer of all the IgG subclasses, the increase on the Th1-associated IgG2b subclass was clearly more pronounced. Remarkably, this effect on the IgG2b titer was observed even if alum, a Th2 promoting adjuvant, was present together with IMT504 in the vaccine formulation. The increase in the Th1 response induced by IMT504 was also suggested by in vitro gamma interferon secretion assays. Monkeys of the species Cebus apella immunized with the recombinant Hepatitis B surface antigen plus alum and IMT504 also showed titers of antibodies against the antigen several times superior to the titers observed in control animals immunized with the antigen plus alum without ODN. Since rat and monkey cells are significantly less immunostimulated "in vitro" by PyNTTTTGT ODNs than human cells, the present results reasonably predict a very good performance of these ODNs as adjuvants in human vaccination.

Taking a Toll on human disease: Toll-like receptor 4 agonists as vaccine adjuvants and monotherapeutic agents

Toll-like receptor (TLR) agonists are being developed for use as vaccine adjuvants and as stand-alone immunomodulators because of their ability to stimulate innate and adaptive immune responses. Among the most thoroughly studied TLR agonists are the lipid A molecules that target the TLR4 complex. One promising candidate, monophosphoryl lipid A, which is a derivative of lipid A from Salmonella minnesota, has proven to be safe and effective as a vaccine adjuvant in > 120,000 human doses. A new class of synthetic lipid A mimetics, the aminoalkyl glucosaminide 4-phosphates (AGPs), have been engineered specifically to target human TLR4 and are showing promise as vaccine adjuvants and as monotherapeutic agents capable of eliciting nonspecific protection against a wide range of infectious pathogens. In this review, the authors provide an update of the preclinical and clinical experiences with the TLR4 agonists, MPL (Corixa Corporation) adjuvant and the AGPs.

Recombinant hepatitis B vaccine (Engerix-B): a review of its immunogenicity and protective efficacy against hepatitis B

Engerix-B (Hep-B[Eng]) is a noninfectious recombinant DNA vaccine containing hepatitis B surface antigen (HBsAg). It is produced from genetically engineered yeast (Saccharomyces cerevisiae). Intramuscular Hep-B(Eng) [0-, 1-, 6-month schedule] has excellent immunogenicity in healthy neonates and infants, children, adolescents and adults, with seroprotection rates of 85-100% seen approximate, equals 1 month after the final dose of vaccine; seroprotection was defined as an antibody against HBsAg (anti-HBs) titre of > or =10 IU/L. The use of alternative Hep-B(Eng) immunisation schedules (e.g. a 0-, 1-, 2-, 12-month schedule in neonates and infants, 0-, 12-, 24-month or two-dose schedules in children and adolescents, and accelerated schedules in adults) have also been associated with high rates of seroprotection. Seroprotection rates were generally similar with Hep-B(Eng) and the recombinant vaccine Recombivax HB (Hep-B[Rax]) or plasma-derived vaccines (PDVs) approximate, equals 1 month after the final dose (although anti-HBs geometric mean titres were significantly higher with Hep-B[Eng] than with Hep-B[Rax]). One month after the final dose, adults had significantly higher seroprotection rates with the recombinant triple-antigen vaccine Bio-Hep-B (Hep-B[Bio]) than with Hep-B(Eng), although seroprotection rates in healthy infants were similar with Hep-B(Eng) and Hep-B(Bio). Hep-B(Eng) had excellent immunogenicity in several groups considered at high risk of acquiring hepatitis B (e.g. neonates born to hepatitis B carrier mothers and healthcare workers). The immunogenicity of Hep-B(Eng) was reduced in patients with conditions associated with impaired immune function (e.g. patients undergoing haemodialysis or being treated for malignancy), although it had good immunogenicity in patients with diabetes mellitus.Hep-B(Eng) had excellent protective efficacy against HBsAg carriage in healthy infants and children, and in neonates born to hepatitis B carrier mothers (protective efficacy of 95-99%). Hep-B(Eng) also demonstrated good protective efficacy in a number of other high-risk groups. Hep-B(Eng) is generally well tolerated with a tolerability profile similar to that of Hep-B(Rax), Hep-B(Bio) and PDVs. In conclusion, Hep-B(Eng) is a well established, highly immunogenic hepatitis B vaccine with good tolerability and excellent protective efficacy; it offers flexibility through a variety of immunisation schedules. In addition, it appears that Hep-B(Eng) confers immunity for at least 10 years. Hep-B(Eng) has an important role in mass vaccination campaigns against hepatitis B, as well as in groups considered at high risk of acquiring hepatitis B.

Immunogenetics of the response to HBsAg vaccination

The major envelope protein of the hepatitis B virus (HBV), the HBsAg, constitutes the current preventative vaccine, which represents the first subunit viral vaccine developed. The genetics of the immune response to HBsAg has been extensively studied both in humans and mice. Murine studies begun over 20 years ago indicated that at least two MHC class II and one MHC class III genes regulate anti-HBs immune responses. Additional MHC-linked genes influence the immune responses to the higher molecular weight (pre-S) components of the HBV envelope. The murine studies predicted even more complex MHC gene regulation of human immune responses to the HBsAg and that complexity certainly has been demonstrated during the ensuing years. This brief review is an attempt to summarize our current understanding of the MHC genes that influence the immune response to the HBsAg and possible mechanisms of action.

Enhancement of antigen-specific immunity via the TLR4 ligands MPL adjuvant and Ribi.529

MPL (Corixa) adjuvant is a chemically modified derivative of lipopolysaccharide that displays greatly reduced toxicity while maintaining most of the immunostimulatory activity of lipopolysaccharide. MPL adjuvant has been used extensively in clinical trials as a component in prophylactic and therapeutic vaccines targeting infectious disease, cancer and allergies. With over 33,000 doses administered to date, MPL adjuvant has emerged as a safe and effective vaccine adjuvant. Recently, scientists at Corixa Corporation have developed a library of synthetic lipid A mimetics (aminoalkyl glucosaminide 4-phosphates) with demonstrated immunostimulatory properties. Similar to MPL adjuvant, these synthetic compounds signal through Toll-like receptor 4 to stimulate the innate immune system. One of these compounds, Ribi.529 (RC-529), has emerged as a leading adjuvant with a similar efficacy and safety profile to MPL adjuvant in both preclinical and clinical studies.