Reinhard Glück

Eleven years of Inflexal V-a virosomal adjuvanted influenza vaccine.

Since the introduction to the Swiss market in 1997, Crucell (former Berna Biotech Ltd.), has sold over 41 million doses worldwide of the virosomal adjuvanted influenza vaccine, Inflexal V. Since 1992, 29 company sponsored clinical studies investigating the efficacy and safety of Inflexal V have been completed in which 3920 subjects participated. During its decade on the market, Inflexal V has shown an excellent tolerability profile due to its biocompatibility and purity. The vaccine contains no thiomersal or formaldehyde and its purity is reflected in the low ovalbumin content. By mimicking natural infection, the vaccine is highly efficacious. Inflexal V is the only adjuvanted influenza vaccine licensed for all age groups and shows a good immunogenicity in both healthy and immunocompromised elderly, adults and children. This review presents and discusses the experience with Inflexal V during the past decade.

Immunogenicity and protectivity of a new liposomal hepatitis A vaccine.

In this study we investigated a new liposomal hepatitis A vaccine (Epaxal) developed by the Swiss Serum and Vaccine Institute clinically and immunologically using a one dose priming schedule and a booster injection after 1 year. This vaccine contains formalin inactivated hepatitis A virus particles attached to phospholipid vesicles together with influenza virus haemagglutinin. Two doses of the vaccine were administered at months 0 and 12 in 117 volunteers. Blood samples were drawn at days-7, 14 and 28 and after 6, 12 and 13 months, local and systemic reactions were monitored by means of questionnaires. Immunogenicity was evaluated as usual by the determination of anti-HAV from the collected sera using the ELISA technique. In order to evaluate the protective efficacy of the vaccine induced antibodies a sample of 25 sera mainly from vaccinees showing low ELISA titres was additionally analysed by means of a virus NT. The vaccine was excellently tolerable and highly immunogenic. Seroconversion evaluated by ELISA was 97 and 99%, respectively, 14 and 28 days after the first dose and 100% after the second dose. NT titres were well correlated with ELISA titres and showed similar seroconversion rates even in the early phase of immunization. The results of this study show that with two doses of the liposomal hepatitis A vaccine administered at months 0 and 12 early protection within 14 days and long lasting immunity can be achieved.

Immunogenicity of trivalent subunit versus virosome-formulated influenza vaccines in geriatric patients.

The safety and immunogenicity of a commercial trivalent subunit influenza vaccine and an experimental virosome-formulated influenza vaccine were evaluated among geriatric patients in a double-blind, randomized manner. The virosome vaccine was produced by incorporating hemagglutinin (HA) into the membrane of liposomes composed of phosphatidylcholine. Both vaccines elicited a significant (P < 0.01) rise in the geometric mean anti-HA antibody titer to all three vaccine components 1 month after immunization. However, significantly (P < 0.005) more subjects vaccinated with the virosome preparation mounted a more than fourfold rise to the A/Singapore and A/Beijing strains compared with those who received subunit vaccine. The percentage of patients who attained protective levels (anti-HA titer > or = 40) of anti-A/Beijing antibody was also significantly (P < 0.005) higher in the virosome group. Subjects who possessed non-protective baseline antibody levels to the A/Singapore and A/Beijing strains were more likely (P < 0.005-0.030) to achieve protective levels after immunization with the virosome vaccine than with the subunit vaccine. Of particular clinical significance was the fact that 68.4% of subjects immunized with the virosome vaccine attained protective levels of antibody to all three vaccine components versus 38% for the subunit vaccine (P = 0.010).

Immunogenicity and adverse effects of inactivated virosome versus alum-adsorbed hepatitis A vaccine: a randomized controlled trial

Immunogenicity and adverse effects of a novel inactivated hepatitis A vaccine based on virosomes (IRIV-HAV) was compared with a standard vaccine adsorbed to aluminium (Al-HAV). Seronegative volunteers (n = 301) were randomly allocated to one injection of IRIV-HAV or to two injections of Al-HAV, followed by a booster injection at 12 months. Two hundred and ninety-eight (99%) completed the first month and 215 (71%) could be evaluated at 1 year. Geometric mean antibody concentrations at days 0, 14 and at 12 months were similar in the two vaccine groups. Lower antibody concentrations were recorded with IRIV-HAV at day 28 (P < 0.0001) and at 13 months (P = 0.02). Seroconversion to protective antibody levels, however, was similar (98% at day 28, 94% at 12 months, 100% at 13 months). Local adverse effects were reported in 17% with IRIV-HAV but in 66% with Al-HAV (P < 0.0001) after the initial vaccination and in 32% and 42% following the booster vaccination (P = 0.05). In conclusion, IRIV-HAV may provide similar protection but cause less local adverse effects.

Safety and immunogenicity of intranasally administered inactivated trivalent virosome-formulated influenza vaccine containing Escherichia coli heat-labile toxin as a mucosal adjuvant.

A trivalent influenza virosome vaccine containing hemagglutinin and Escherichia coli heat-labile toxin (HLT) was administered intranasally to young adults and elderly subjects. Symptoms that followed immunization were mild and transient. A significant increase in serum hemagglutination inhibition (HI) antibody was noted for the 3 vaccine strains. There was no significant difference in postimmunization geometric mean titers or seroconversion rates between age groups. The percentage of subjects attaining protective HI titers (>/=40%) was comparable in both groups for the A/Bayern (P=.5) and B/Beijing (P=.3) strains but was higher among young adults (92.2%) versus elderly subjects (76.5%; P=.057) for the A/Wuhan strain. The proportion of subjects with nonprotective baseline titers who attained protective levels after immunization was similar in both age groups for the A/Bayern and B/Beijing components. For the A/Wuhan component, significantly (P=.017) more young adults achieved protective titers versus elderly subjects (85. 7% and 53.8%, respectively). Vaccination evoked a significant (P<. 005) increase in anti-HLT antibody titers.

Immunopotentiating reconstituted influenza virosomes (IRIVs) and other adjuvants for improved presentation of small antigens

Synthetic peptides, purified subunits or inactivated small virus particles require immunopotentiation if they are to be effective vaccines. A large range of procedures to enhance immunogenicity has evolved over the last decades: aluminium salts, proteosomes, immunostimulating complexes (ISCOMs), liposomes, conjugation with bacterial products or derivatives, combination with surface-active agents or application of cytokines have been the most described classes of adjuvants. We describe here the design of an inactivated hepatitis A vaccine adjuvanted with immunopotentiating reconstituted influenza virosomes (IRIVs). The formalin-inactivated hepatitis A particles are attached to reconstituted protein-lipid complexes consisting of a mixture of phospholipids and influenza virus glycoproteins. With this new vaccine design we combined different immunostimulating effects: immunopotentiation by phospholipid vesicles, recognition of the haemagglutinin (HA) epitopes by the immune system, binding capacity of HA to sialic acid-containing receptors of macrophages and immunocompetent cells and mediation of entry into the cytoplasm of macrophages by a membrane-fusion event triggered by HA. Hepatitis A seronegative human volunteers received one intramuscular injection with this new vaccine. There were only few mild local reactions and 14 days after vaccination 100% of the subjects were seropositive. Among the individuals (control group) who received an alum-adsorbed vaccine, 88% developed local reactions. The seroconversion rate was 44%. We conclude from these results that the IRIVs provide a new approach to the future design of adjuvanted vaccines.

Adjuvant activity of immunopotentiating reconstituted influenza virosomes (IRIVs).

Using immunopotentiating, reconstituted influenza virosomes (IRIV) as a delivery vehicle, a number of vaccines have been developed. In humans, IRIV-based vaccines containing hepatitis A and influenza antigens have been found to possess enhanced immunogenicity compared to alum-adsorbed vaccine for hepatitis A or commercial subunits or whole virion influenza vaccines. These vaccines were safe and did not engender any antiphospholipid antibodies against the liposome components of the IRIV. Hepatitis B, tetanus toxoid and diphtheria toxoid, and nucleic acids have also been incorporated into IRIVs. These vaccines are now undergoing clinical phase I testing. IRIVs are also being evaluated in phase I trials for their ability to deliver antigens by the intranasal route.

Mucosal antibody response induced with a nasal virosome-based influenza vaccine

A vaccination against influenza that elicits both a systemic antibody and a mucosal IgA response would improve on the protective efficacy of currently available vaccines. Previous studies have shown the safety and efficacy of virosomes as delivery systems in vaccination. This study was a controlled, randomised, double-blind, single centre, phase II trial assessing an intranasal virosome vaccine, adjuvanted with heat-labile toxin (HLT) from enterotoxigenic Escherichia coli, versus an intranasal without HLT and comparing it open to an intramuscular vaccine in a total of 88 healthy adults. The development of a new technique enabled for the first time the detection of neutralising IgA antibodies in very dilute nasal wash samples. It was demonstrated that intranasally administered inactivated influenza vaccine, adjuvanted with HLT, not only elicits a spectrum of humoral and cell-mediated responses in healthy adults, critical for the protection and recovery from influenza virus infection, but is also highly effective in eliciting IgA neutralising antibodies at the mucosa. Intranasal virosome-formulated, HLT-adjuvanted, influenza vaccine was effective and well tolerated in this study. Its potential to offer a high level of mucosal protection, not provided by conventional parenteral vaccination, could play a significant role in preventing morbidity and mortality associated with influenza.

Towards clinical testing of a single-administration tetanus vaccine based on PLA/PLGA microspheres

The availability of single-administration vaccines would assist in the control of global mortality caused by infectious diseases where protection can be achieved only upon repeated immunisations with appropriate vaccines. Biodegradable microspheres of poly(lactide-co-glycolide) have been studied pre-clinically for this purpose and shown to be promising for several protein and sub-unit antigens. In view of preparing a microsphere-based tetanus vaccine for clinical trials, final candidate vaccine-formulations were pre-clinically optimised here. Specifically, the importance of particular materials and processing for the induction of neutralising antibodies in guinea pigs were examined. The most efficacious vaccines were small-sized (<5 microm), co-adjuvanted with admixed alum and fabricated from fast-degrading polymers. Interestingly, the immunogenicity was less influenced by the type of antigen-stabilising excipient, the number of microsphere populations mixed together, or the microencapsulation technology, i.e. spray-drying versus coacervation, used. On the basis of these, we plan to prepare clinical samples for safety and immunogenicity testing in man.

Influenza virosomes as an efficient system for adjuvanted vaccine delivery

Immunopotentiating reconstituted influenza virosomes possess several characteristics defining them as vaccine adjuvants. Virosomes have been shown to provide vaccine components with protection from extracellular degradation; a regular, repetitive antigen structure aiding presentation to B lymphocytes and fully functional, fusion-active, influenza haemagglutinin envelope proteins that enables receptor-mediated uptake and intracellular processing of the antigen. In addition, virosomes, as vaccine delivery systems, have been shown to be safe and not to engender any antibodies against the phospholipid components. Through the use of virosomes as a delivery vehicle, a number of vaccines have been developed. In humans, virosome-based vaccines containing inactivated hepatitis A and influenza antigens have been found to be efficacious and well-tolerated and have been on the market for several years. Hepatitis B, nucleic acids, cytotoxic drugs, and tetanus and diphtheria toxoids have also been incorporated into virosomes. Further investigations are ongoing in order to define the full potential of virosomes in both prophylactic and immunotherapeutic applications.