Immunogenicity of new virosome influenza vaccine in elderly people

New vaccine approaches for seasonal and pandemic influenza

Inactivated influenza vaccines have been available since the late 1940s for the prevention of influenza disease. Based on the available scientific evidence, many public health authorities, including the World Health Organization, recommend annual use of these vaccines for specific populations, including the elderly. Despite these recommendations, actual vaccination uptake rates are very limited in many countries. Influenza vaccine research is confounded by the variable nature of the influenza viruses and annual influenza epidemics and by non-specific clinical diagnostic criteria. These confounding factors complicate evaluation not only of overall vaccine effectiveness, but also of the relative efficacy and effectiveness of different vaccine formulations. This paper summarizes recent advances in the development of seasonal and (pre-)pandemic vaccines, discusses the methodologic constraints on influenza vaccine research, and proposes measures to reduce the level of potential bias and confounding in influenza vaccine research.

Influenza virus-specific cytotoxic T lymphocytes: a correlate of protection and a basis for vaccine development

Since influenza A viruses of the H5N1 subtype continue to circulate in wild and domestic birds and cause an ever increasing number of human cases, it is feared that H5N1 viruses may cause the next influenza pandemic. Therefore, there is considerable interest in the development of vaccines that confer protection against infections with these viruses or ideally, protection against influenza viruses of different subtypes. For the development of broad-protective vaccines the induction of virus-specific cytotoxic T lymphocytes (CTL) may be an important target, since it has been demonstrated that CTL contribute to protective immunity and are largely directed to epitopes shared by influenza viruses of various subtypes. In the present paper, the possibility to develop (cross-reactive) CTL-inducing vaccines is discussed.

Emerging vaccines for influenza

BACKGROUND

Influenza remains one of the leading causes of morbidity and mortality worldwide. The available vaccines are least effective in the populations at greatest risk--children, the elderly, and the immunocompromised. Furthermore, avian influenza and other novel strains have the potential to cause the next influenza pandemic. Research efforts have accelerated worldwide to develop new vaccines to provide better immunity against annual epidemics and a potential pandemic.

OBJECTIVE

To summarize the global research efforts at developing new influenza vaccines, adjuvants, and delivery devices.

METHOD

MEDLINE and Pharmaprojects databases were searched for publications and continuing research on new influenza vaccine technologies.

RESULTS/CONCLUSIONS

Technologies such as DNA vaccines, live recombinant viral vector vaccines, and virus-like particles have shown significant promise for immunogenicity and protection from experimental challenge to influenza. New modalities for vaccine delivery and methods for rapid vaccine production are also being investigated. With the possibility of an influenza pandemic increasing the need to develop new vaccines, the global research community has made large strides to meet this challenge.

Influenza vaccines and vaccination strategies in birds

Although it is well accepted that the present Asian H5N1 panzootic is predominantly an animal health problem, the human health implications and the risk of human pandemic have highlighted the need for more information and collaboration in the field of veterinary and human health. H5 and H7 avian influenza (AI) viruses have the unique property of becoming highly pathogenic (HPAI) during circulation in poultry. Therefore, the final objective of poultry vaccination against AI must be eradication of the virus and the disease. Actually, important differences exist in the control of avian and human influenza viruses. Firstly, unlike human vaccines that must be adapted to the circulating strain to provide adequate protection, avian influenza vaccination provides broader protection against HPAI viruses. Secondly, although clinical protection is the primary goal of human vaccines, poultry vaccination must also stop transmission to achieve efficient control of the disease. This paper addresses these differences by reviewing the current and future influenza vaccines and vaccination strategies in birds.

Development of a mucosal vaccine for influenza viruses: preparation for a potential influenza pandemic

Highly pathogenic avian H5N1 influenza A virus has caused influenza outbreaks in poultry and migratory birds in Southeast Asia, Africa and Europe, and there is concern that it could cause a new pandemic. This fear of an emerging pandemic of a new influenza strain underscores the urgency of preparing effective vaccines to meet the pandemic. One way to mitigate current concerns is to develop an influenza vaccine that is fully functional against drift influenza viruses. In our current situation, in which we cannot predict which strain will cause a pandemic, cross-protective immunity using potential and novel mucosal vaccines plays a particularly important role in preventing the spread of highly pathogenic influenza virus.

The Efficacy of Vaccines to Prevent Infectious Diseases in the Elderly

Infectious diseases still represent a major challenge to human progress and survival. Especially elderly persons are more frequently and severely affected by infectious diseases and they display distinct features with respect to clinical presentation and treatment. Although vaccinations are considered a vital medical procedure for preventing morbidity and mortality caused by infectious diseases, the protective effect of vaccinations is abrogated in elderly persons. This is due to a decline in the functions of the immune system referred to as immunosenescence. The first part of this chapter will therefore summarize the status quo of the efficacy of vaccines in preventing morbidity and mortality caused by typical infectious diseases in the elderly, such as influenza, pneumonia and tuberculosis. The second part will then elucidate the underlying age-related mechanisms which may contribute to the decreased efficacy of vaccines. Based on the complex mechanisms involved in immunosenescence, strategies will be outlined which may be succesfful in enhancing protective immune responses following vaccination in elderly persons.

Influenza vaccination in systemic lupus erythematosus: safe and protective?

Patients with systemic lupus erythematosus (SLE) show decreased immune responsiveness and are vulnerable for infectious diseases, due to the underlying disease and the frequent use of immunosuppressive drugs. Influenza has a high incidence in the population and is associated with increased morbidity and mortality in immunocompromised patients. Therefore, routine influenza vaccination of SLE patients seems indicated. However, there have been concerns about the safety of influenza vaccination in SLE as vaccination was thought to activate the autoimmune response. Safety of influenza vaccination has been studied, and, as far as SLE patients with quiescent disease are concerned, it is now generally accepted that influenza vaccination is safe. Another point of concern is vaccine efficacy. In immunocompromised patients, the immunogenicity of vaccines may be reduced. In the immune response to influenza (vaccination) both humoral and cell-mediated responses are involved. In SLE, research on the immune response to influenza vaccination has focused on humoral immune responses, demonstrating a blunted humoral response. Future research should focus on cell-mediated immune responses as well, as these are important for clearing of influenza infection and are expected to be impaired in SLE. Because of the decreased immunogenicity of the current influenza vaccine in SLE, new influenza vaccination strategies should be explored to improve vaccination efficacy.

Safety and efficacy of influenza vaccination in systemic lupus erythematosus patients with quiescent disease

OBJECTIVE

to assess the safety and efficacy of influenza vaccination in patients with systemic lupus erythematosus (SLE), and to evaluate the influence of immunosuppressive drugs on the immune response.

METHODS

SLE patients (n=56) and healthy controls (n=18) were studied. All patients had quiescent disease (SLE disease activity index

RESULTS

Influenza vaccination did not result in changes in disease activity and was well tolerated. SLE patients had fewer seroconversions or fourfold titre rises for A/H1N1 (p<0.001) and A/H3N2 (p<0.001) than healthy controls, while for B/Hong Kong the difference was of borderline significance (p=0.051). With regard to immunosuppressive treatment, fewer SLE patients using azathioprine developed fourfold titre rises against A/H3N2 (p=0.041), and fewer achieved titres of >or=40 against A/H3N2 (p=0.030) compared with the other patient groups.

CONCLUSIONS

Influenza vaccination in SLE patients with quiescent disease is safe but is less effective than in controls. Use of azathioprine was associated with a trend to decreased vaccination efficacy.

Collapse

Key Words

• sle
• influenza vaccination
• safety
• efficacy

Collapse

MESH Headings

• Adult
• Aged
• Antibodies, Viral/blood
• Azathioprine/therapeutic use
• Case-Control Studies
• Female
• Hemagglutination Inhibition Tests
• Humans
• Hydroxychloroquine/therapeutic use
• Immunosuppressive Agents/therapeutic use
• Influenza Vaccines/administration & dosage
• Influenza Vaccines/adverse effects
• Influenza Vaccines/immunology
• Lupus Erythematosus, Systemic/drug therapy
• Lupus Erythematosus, Systemic/immunology
• Male
• Middle Aged
• Orthomyxoviridae/immunology
• Prednisone/therapeutic use
• Statistics, Nonparametric
• Vaccination/adverse effects

Collapse

Grants Collapse

Affiliation(s)

A Holvast Department of Clinical Immunology, University Medical Center Groningen, University of Groningen, PO Box 30.001, 9700 RB Groningen, Netherlands.
A Huckriede
J Wilschut
G Horst
J J C De Vries
C A Benne
C G M Kallenberg
M Bijl

Collapse

A new intranasal influenza vaccine based on a novel polycationic lipid—ceramide carbamoyl-spermine (CCS)

Although most pathogens use the mucosal routes for invasion, the majority of currently available vaccines are administered parenterally. Injectable vaccines induce good systemic immunity but often unsatisfactory mucosal immunity. A non-injectable mucosal vaccine, which can be self-administered intranasally, may provide both effective systemic and mucosal immunity and can be used for vaccination of large populations within a short period of time in case of a sudden epidemic. Here, we report on a new intranasal (i.n.) influenza vaccine, based on a novel polycationic sphingolipid, N-palmitoyl D-erythro-sphingosyl carbamoyl-spermine (ceramide carbamoyl-spermine = CCS), having combined carrier and adjuvant activities, which elicits, in mice, strong systemic (serum) and local (lung and nasal) humoral and cellular responses, and provides protective immunity. In a comparative study, we show that both unmodified commercial vaccine and vaccine formulated with neutral or anionic liposomes were poorly immunogenic upon i.n. administration. Of five vaccine formulations based on well-established monocationic lipids in the form of unsized liposomes, three (DC-Chol, DDAB, and DSTAP-based) resulted in low serum and local responses, while two others (DMTAP and DOTAP-based vaccines) induced both systemic and local vigorous Th1+Th2 immune responses. However, only the vaccine formulated with CCS was equivalent or superior to the commercial vaccine co-administered with cholera toxin as an adjuvant. Furthermore, the CCS-based influenza vaccine was highly efficacious following a single or a repeated (x2) i.n. or a single i.m. administration, without an added adjuvant, in both young (2 months) and old (18 months) mice. It elicited high titers of strain cross-reactive hemagglutination inhibition (HI) antibodies, and the high antibody titers and protective immunity persisted for at least 9 months. No systemic adverse effects, and only a mild local inflammatory response, were observed in mice and rabbits vaccinated i.n. with the CCS vaccine formulation. A similar approach may prove efficacious for i.n. vaccination against other pathogens.

Use of a dialyzable short-chain phospholipid for efficient solubilization and reconstitution of influenza virus envelopes

Virosomes are reconstituted viral envelopes that can serve as vaccines and as vehicles for cellular delivery of various macromolecules. To further advance the use of virosomes, we developed a novel dialysis procedure for the reconstitution of influenza virus membranes that is easily applicable to industrial production and compatible with encapsulation of a variety of compounds. This procedure relies on the use of 1,2-dicaproyl-sn-glycero-3-phosphocholine (DCPC) as a solubilizing agent. DCPC is a short-chain lecithin with detergent-like properties and with a critical micelle concentration of 14 mM. DCPC effectively dissolved the influenza virus membranes after which the nucleocapsids could be removed by ultracentrifugation. The solubilized membrane components were reconstituted either by removal of DCPC by dialysis or by a procedure involving initial dilution of the solubilized membrane components followed by dialysis. Both protocols resulted in removal of 99.9% of DCPC and simultaneous formation of virosomes. Analysis of the virosome preparations by equilibrium sucrose density gradient centrifugation revealed co-migration of phospholipid and protein for virosomes produced by either method. Moreover, both virosome preparations showed morphological and fusogenic characteristics similar to native influenza virus. Size, homogeneity and spike density of the virosomes varied with the two different reconstitution procedures employed. The recovery of viral membrane proteins and phospholipids in the virosomes was found to be higher for the dilution/dialysis procedure than for the simple dialysis protocol. This novel procedure for the production of virosomes is straightforward and robust and allows further exploitation of virosomes as vaccines or as drug delivery vehicles not only in academia, but also in industrial settings.

Reactogenicity and immunogenicity of an inactivated influenza vaccine administered by intramuscular or subcutaneous injection in elderly adults

In many countries there is no clear recommendation regarding the preferred route of administration of inactivated influenza vaccines. In a randomised, observer blind study of 720 elderly subjects, a split, trivalent influenza vaccine was significantly more immunogenic for both A strains (H3N2 and H1N1, p = 0.0016 and 0.003, respectively) when given intramuscularly compared to subcutaneously. This difference was due entirely to a gender effect, with females in the intramuscular (IM) group having a significantly greater serological response than females in the subcutaneous (SC) group for both of these strains. Similar results were seen with local adverse effects. These data suggest that vaccination practices that ensure intramuscular injection are required for optimal administration of influenza vaccines in the elderly.

The virosome concept for influenza vaccines

There is a need for more efficacious inactivated influenza vaccines, since current formulations show suboptimal immunogenicity in at-risk populations, like the elderly. More effective vaccines are also urgently needed for an improved influenza pandemic preparedness. In this context, there is considerable interest in virosomes. Virosomes are virus-like particles, consisting of reconstituted influenza virus envelopes, lacking the genetic material of the native virus. Virosomes are produced from influenza virus through a detergent solubilization and removal procedure. Properly reconstituted virosomes retain the cell binding and membrane fusion properties of the native virus, mediated by the viral envelope glycoprotein haemagglutinin. These functional characteristics of virosomes form the basis for their enhanced immunogenicity. First, the repetitive arrangement of haemagglutinin molecules on the virosomal surface mediates a cooperative interaction of the antigen with Ig receptors on B lymphocytes, stimulating strong antibody responses. In addition, virosomes interact efficiently with antigen-presenting cells, such as dendritic cells, resulting in activation of T lymphocytes. In a murine model system, virosomes, as compared to conventional subunit vaccine, which consists of isolated influenza envelope glycoproteins, induce a more balanced T helper 1 versus T helper 2 response, virosomes in particular eliciting stronger T helper 1 responses than subunit vaccine. Also, as a result of fusion of the virosomes with the endosomal membrane, part of the virosomal antigen gains access to the major histocompatibility class I presentation pathway, thus priming cytotoxic T lymphocyte activity. Finally, virosomes represent an excellent platform for inclusion of lipophilic adjuvants for further stimulation of vaccine immunogenicity. By virtue of these characteristics, virosomes represent a promising novel class of inactivated influenza vaccines, which not only induce high virus-neutralizing antibody titres, but also prime the cellular arm of the immune system.

Clinical experience with inactivated, virosomal influenza vaccine

Current available influenza vaccines are safe and effective in preventing influenza. Nevertheless, there is a need for influenza vaccines with improved efficacy in the elderly. This need is underscored by both the observation that influenza has a major clinical and economic impact in the elderly and the fact that currently available vaccines are generally less effective in elderly than in younger subjects. Several approaches are currently being pursued in order to improve the efficacy of influenza vaccines in elderly individuals and others who have impaired immune responses to conventional influenza vaccines. A novel antigen-presenting strategy to overcome impaired immune responses is the use of virosomes. Previously, data on safety and reactogenicity have been published regarding the use of virosomal influenza vaccines. Data from three recent clinical trials are presented here. The first of these was a comparative study of a virosomal vaccine and a conventional subunit vaccine in "at-risk" adults with underlying chronic illness. The virosomal vaccine demonstrated comparable tolerability to the subunit vaccine, with about 98% of patients reporting tolerability to be good or very good. The vast majority of adverse events reported were mild to moderate in severity. With both vaccine types, mean HI titres decreased with age for both the A-H1N1 and B influenza virus strains, but for the A-H3N2 strain (the most virulent of the three strains), mean HI titres did not decrease with age, suggesting a better response with the virosomal vaccine when compared to the subunit vaccine. All three studies explored the long-term persistence of antibodies after vaccination with virosomal influenza vaccines. Immunogenicity declined over time but remained high at 4, 6 and 12 months post-vaccination compared to baseline, indicating that adequate seroprotection is achievable for the duration of the influenza season. Virosomal vaccines may induce better immunity in elderly subjects and may be more effective in reducing morbidity and mortality in this age group.

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.

Improved immune responses to influenza vaccination in the elderly using an immunostimulant patch

The elderly have greater morbidity and mortality due to influenza, and respond poorly to influenza vaccination compared to younger adults. This study was designed to determine if the adjuvant heat-labile enterotoxin from Escherichia coli (LT), administered as an immunostimulant (IS) patch on the skin with influenza vaccination, improves influenza immune responses in the elderly. Three weeks following vaccination, hemagglutination inhibition (HAI) responses in LT IS patch recipients showed improvement over those of elderly receiving vaccine alone, as demonstrated by significance or trends in fold rise [A/Panama (P = 0.004), A/New Caledonia (P = 0.09)], seroconversion [A/New Caledonia (63% versus 40%, P = 0.01), A/Panama (54% versus 36%, P = 0.08)] and seroprotection [26%, 20% and 16% greater for the patch group for A/New Caledonia, A/Panama and B/Shandong strains, respectively]. The data suggest that an LT IS patch may further enhance influenza vaccine immune responses in the elderly.

Strong local and systemic protective immunity induced in the ferret model by an intranasal virosome-formulated influenza subunit vaccine

The proliferation of influenza viruses causes costly, recurrent, annual epidemics. Current vaccines, mainly administered parenterally, have been shown to be suboptimal in terms of efficacy, particularly where local IgA responses are concerned. Recent investigations of virosomes as delivery systems for viral HA and NA antigens have demonstrated an improved immune response. This paper investigates the efficacy of a novel virosome-based intranasal influenza vaccine by its ability to reduce disease symptoms and its effect on viral shedding in nasal secretions of immunised ferrets. The use of ferrets in the study of influenza vaccines is based on the good comparability between ferret and human response to the disease. Intranasal, as opposed to parenteral, administration of a trivalent virosome-based subunit vaccine adjuvanted with HLT provides an almost total prevention of virus shedding combined with a high level of immunological protection against homologous virus challenge. The ease of application of an intranasal vaccine may have positive repercussions in the adoption of influenza vaccinations, particularly in 'at-risk' groups.

Liposomes as Protein Carriers in Immunology

Liposomes are excellent carriers for protein antigens since they can contain large amounts of antigen, potentially in association with adjuvants. Liposomes may be made to mimic the pathogens that stimulated the evolution of the immune system. As such, numerous mechanisms exist to promote their uptake by antigen presenting cells and exposure of encapsulated antigens to the lymphocytes of the immune system for the induction of responses. The review is intended to describe the 30 year history of the use of liposomes are carriers of protein antigens, notably from the perspective of what we have learned about the immune system using liposomes.

Virosomes as new carrier system for cancer vaccines

HER-2/neu, a tumor-associated antigen (TAAg), plays a critical role in oncogenesis of various tumor types, and its selective overexpression by malignant tumor cells makes it an ideal target for immunotherapy. A prerequisite for clinical vaccines is the construction of safe and highly immunogenic reagents able to generate efficient immune responses against TAAg. Previous protein vaccines, consisting of the extracellular domain of HER-2/neu (pNeuECD), were shown to elicit an immune response that did not provide protection from transplantable tumors expressing HER-2/neu. Here we showed that virosomes, which consist of reconstituted viral envelopes without viral genetic material, can act as a carrier and an adjuvant for a truncated protein pNeuECD. Mice vaccinated with pNeuECD either encapsulated in virosomes or bound to the virosomal membrane (Vir-pNeuECD), generated rNeu-specific humoral and cytotoxic immune responses. In addition, Vir-p(NeuECD) induced significant tumor rejection and additionally did not lead to delayed tumor formation when compared with free pNeuECD in complete Freund's adjuvant. There was no difference between the virosomal constructs. Taken together these results suggest that virosomes, as clinically approved safe vaccines, can be used to elicit both humoral and cell-mediated responses against TAAg and induce tumor rejection. Our model is providing important preclinical data to design human vaccination trials for patients with tumors overexpressing HER-2/neu, either as a primary vaccination or as a boost in combination with other vaccines in a context of an adjuvant treatment plan.

Comparison of immunogenicity and tolerability of a virosome-adjuvanted and a split influenza vaccine in children

OBJECTIVE

To compare the immunogenicity and safety of a virosome-adjuvanted influenza vaccine (Inflexal V; Berna Biotech, Berne, Switzerland) and a split influenza vaccine (Fluarix; GlaxoSmithKline Biologicals, Rixensart, Belgium) in children.

SUBJECTS AND METHODS

The subjects, 453 children ages 6 to 71 months, were stratified into primed and unprimed and age groups (6 to 35 and 36 to 71 months) and then randomized 1:1 to receive virosome-adjuvanted (n = 224) or split influenza vaccine (n = 229), a half or full dose was given intramuscularly according to age. Unprimed children received a second dose after 4 weeks. Blood samples (n = 326) collected pre-and 28 days postvaccination were analyzed by hemagglutination inhibition test. Safety assessments were made at baseline and follow-up visits by the investigators and by parents for the 4 days after vaccinations.

RESULTS

Both vaccines induced an effective immune response. Seroconversion rates (>4-fold titer rise) against the WHO recommended strains A/New Caledonia (H3N2), A/Moscow (H1N1) and B/Hongkong (B) were 80.1, 66.0 and 90.4% for the virosome-adjuvanted and 75.9, 62.9 and 89.4% for the split influenza vaccine, respectively. Unprimed children's seroconversion rates for H3N2 were significantly higher (P = 0.02) for the virosome-adjuvanted (88.8%) than for split influenza vaccine (77.5%). Seroprotection rates (titer of > 40) for H3N2, H1N1 and B, respectively, were 87.8, 80.1 and 90.4% after vaccination with the virosome-adjuvanted vaccine and 82.9, 78.2 and 89.4% after the split influenza vaccine. Unprimed children's seroprotection rate was significantly higher (P = 0.03) for H3N2 after the virosome-adjuvanted (88.8%) than those for the split influenza vaccine (78.3%). Equivalent geometric mean titer fold increases were evident for both vaccines. No serious adverse events were seen. Pain/ tenderness, redness and swelling/induration was found in 25.4, 11.2 and 8.9% for the virosome-adjuvanted vaccine and in 24.0, 9.2 and 6.1% for the split influenza vaccine, respectively. The rates of fever, malaise/irritability and shivering was 6.3, 11.6 and 2.7% for the virosome-adjuvanted vaccine and 8.3, 11.8 and 2.6% for the split influenza vaccine, respectively.

CONCLUSIONS

The virosome-adjuvanted influenza vaccine showed greater immunogenicity over the split influenza vaccine in unprimed children and showed a trend toward better immunogenicity in the rest of the study population. Both vaccines were well-tolerated.

Influenza virosomes enhance class I restricted CTL induction through CD4+ T cell activation

Immunopotentiating reconstituted influenza virosomes (IRIV) are one of the few adjuvants currently licensed for human use. While their adjuvant capacity in the induction of humoral responses is clearly documented, few data exist on their effects on T cell immune response. Here we addressed IRIV adjuvance in the induction of HLA class I restricted cytotoxic T lymphocytes (CTL) in vitro. Lymphocyte stimulation with IM(58-66) and IRIV resulted in marked expansion of specific CTL as compared to cultures performed in the presence of either antigen alone or antigen and control liposomes (L). Studies addressing underlying adjuvant mechanisms demonstrated that IRIV activated CD4/CD45RO+ T cells, induced a cytokine profile consistent with T helper 1 (Th1) stimulation and increased the percentage of CD4+ T cells expressing CXCR3. Furthermore, supernatants from IRIV stimulated PBMC cultures promoted dendritic cell maturation. Most importantly, IRIV mediated CTL adjuvance required the presence of live CD4+ T cells. Powerful adjuvant effects of IRIV were also observed in the induction of CTL specific for the melanoma associated Melan-A/MART-1(27-35), HLA-A0201 restricted epitope. Taken together these findings indicate that IRIV are endowed with a high adjuvant capacity for HLA class I restricted CTL induction, largely attributable to their ability to antigenically stimulate CD4+ T cells.

Immunogenicity and safety of a novel IL-2-supplemented liposomal influenza vaccine (INFLUSOME-VAC) in nursing-home residents

Influenza and its complications account for substantial morbidity and mortality, especially among the elderly. In young adults, immunization provides 70-90% protection, while among the elderly the vaccine may be only </=50% effective; hence, the need for new, more immunogenic vaccines. We compared the safety and immunogenicity of a novel, interleukin-2 (IL-2) -supplemented trivalent liposomal influenza vaccine (designated INFLUSOME-VAC) with that of a commercial trivalent split virion vaccine in community-residing elderly volunteers (mean age 81 years) in winter of 2000/2001. Eighty-one individuals were randomly assigned to be vaccinated intramuscularly, either with the standard vaccine (n=33) or with INFLUSOME-VAC (n=48) prepared from the former. The two vaccines contained equal amounts of hemagglutinin (HA) ( approximately 15 microgram of each viral strain); INFLUSOME-VAC consisted of liposomal antigens admixed with liposomal human IL-2 (Lip IL-2) (33 microgram = 6x10(5) IU/dose). At 1 month post-vaccination, seroconversion rates (tested by hemagglutination inhibition) for the A/New Caledonia (H1N1) and A/Moscow (H3N2) strains were significantly higher (P=0.04) in the INFLUSOME-VAC group (65 versus 45%, 44 versus 24%, respectively). Moreover, INFLUSOME-VAC induced a greater anti-neuraminidase (NA-N2) response (P<0.05). Anti-IL-2 antibodies were undetected, and no increase in anti-phospholipid IgG antibodies was found in the INFLUSOME-VAC group. Adverse reactions were similar in both groups. Thus, INFLUSOME-VAC appears to be both safe and more immunogenic than the currently used vaccine in the elderly.

Virosomal adjuvanted antigen delivery systems

The development of novel and increasingly safer vaccines frequently utilizes well-characterized antigens, in particular highly purified proteins or synthetic peptides. In spite of some achievements, this approach is frequently impeded by the fact that such antigens are often poor immunogens when administered alone. This fact has necessitated the development of suitable adjuvants that possess the ability to enhance the immunogenicity of a given antigen, preferably with little or no side effects. This paper discusses one of the successes of vaccinology of the past decade: virosomal vaccines. The principles of the concept, immunoadjuvant action and application of virosomes in two currently licensed vaccines are detailed, with specific reference to the induction of both humoral and cellular immunity.

Immunogenicity and safety of a novel liposomal influenza subunit vaccine (INFLUSOME-VAC) in young adults

Influenza and its complications account for substantial morbidity and mortality among young adults and especially among the elderly. In young adults, immunization provides 70-90% protection, while among the elderly the vaccine may be only 30-40% effective; hence the need for new, more immunogenic vaccines. We compared the safety and immunogenicity of a novel IL-2-supplemented liposomal influenza vaccine (designated INFLUSOME-VAC) with that of a commercial subunit vaccine and a commercial split virion vaccine in young adults (mean age 28 years) in the winter of 1999-2000. Seventy-three healthy young adults were randomly assigned to be vaccinated intramuscularly with the following: a commercial subunit vaccine (n = 17, group A), INFLUSOME-VAC (n = 36, group B), and a commercial split virion vaccine (n = 20, group C). The three vaccines contained equal amounts of hemagglutinin (approximately 15 microg each) from the strains A/Sydney (H3N2), A/Beijing (H1N1), and B/Yamanashi. INFLUSOME-VAC induced higher geometric mean HI titers and higher-fold increases in HI titers against all three strains, compared with the two commercial vaccines. In addition, seroconversion rates for the A/Sydney and B/Yamanashi strains were significantly higher (P < 0.05) compared with the split virion vaccine, and significantly higher for the three strains compared with the subunit vaccine (69-97% vs 35-65%, P < or = 0.02). Moreover, the anti-neuraminidase response was significantly greater (P = 0.05) in group B vs group A. INFLUSOME-VAC caused mild local pain at the injection site in a significantly higher proportion of the vaccinees (83%). Thus, INFLUSOME-VAC is an immunogenic and safe vaccine in young adults.

Influenza vaccine in chronic lymphoproliferative disorders and multiple myeloma

OBJECTIVE

Vaccination against influenza in patients with chronic lymphoproliferative disorders (CLPD) and multiple myeloma (MM) is still a matter of clinical uncertainty. The aim of this study was to determine the safety, immunogenicity and clinical response to a commercially available vaccine against influenza in a group of such patients.

METHODS

Thirty-four patients with CLPD and MM and 34 immunologically normal subjects were vaccinated with the same vaccine against influenza. Patients were observed during the epidemic season from October 1999 to April 2000, and monitored for side-effects of the vaccine, seroprotection and seroconversion after vaccination. The prevaccination level of immunoglobulins was also determined. Occurrence of influenza episodes was demonstrated with the positive isolation of a viral strain from a pharyngeal swab.

RESULTS

No patient had untoward reactions to the vaccine used. Seroconversion and seroprotection were up to the standard established by the European Agency for the Evaluation of Medicinal Products. Only one patient developed influenza during follow-up.

CONCLUSIONS

Influenza vaccine is effective and well tolerated in patients with CLPD and MM. No contraindications exist for its use, and it should become a routine practice, in order to prevent serious complications during the influenza epidemic season.

Influenza Virosomes in Vaccine Development

Influenza virosomes can be regarded as unilamellar liposomes carrying the spike proteins of influenza virus on their surface. Vaccination with influenza virosomes elicits high titers of influenza-specific antibodies, indicating that HA (and NA) reconstituted into a membranous environment exhibit strong immunogenicity. Moreover, virosomes can be used as presentation systems for unrelated antigens bound to the virosome surface. Because of their intrinsic adjuvant activity, virosomes support antibody formation and induction of T-helper cell responses against such surface-associated antigens. Provided that the fusogenic properties of the reconstituted HA are retained, virosomes can also be used to elicit cytotoxic T-cell responses against encapsulated antigens. Vaccines capable of activating the cellular branch of the immune response can be very important for protection against acute virus infections, especially for viruses with rapidly changing envelope glycoproteins like HIV and influenza virus. Moreover, virosomes can suit as powerful carriers in the development of prophylactic and immunotherapeutic strategies against cancer and premalignant disease. The use of virosomes as commercial influenza vaccine and as commercial adjuvant for a hepatitis A vaccine demonstrates that production of virosomes on an industrial scale is feasible, both technically and economically. The industrial production procedure currently followed has not been designed to retain the functional properties of HA. In fact, several steps in the procedure are probably incompatible with retention of fusion activity. As mentioned previously the fusogenic properties of virosomes are important for CTL activation and might also play a role in the induction of T-helper cell and antibody responses. Therefore, a number of key adaptations in the virosome production protocol will be necessary. Thus improved, virosomes are very attractive devices for the development of highly efficacious vaccines against a range of antigens.

Virosome influenza vaccine in children

The use of vaccines for the prophylaxis of influenza in children is limited. This is despite high annual rates of influenza in children and despite the complications caused by influenza in children with chronic respiratory illnesses. The disease burden of influenza on infants and young children is reviewed and the potential of recommended influenza vaccination in healthy children, to reduce the direct and indirect health and socio-economic costs, is considered. Clinical experience with a virosome-formulated subunit influenza vaccine in children is presented. These clinical trials in children have shown a virosome-formulated subunit influenza vaccine to be immunogenic and well tolerated, indicating that it might be recommended for immunising healthy infants and children against influenza virus.

New technology platforms in the development of vaccines for the future

The desire for improved quality of life in both industrialised and under-developed nations has led to the quest for greater understanding and subsequent prevention and treatment of diseases. Here we discuss some of the latest of modern medicine's approaches to vaccination and disease treatment. Our main subject of discussion being the novel antigen delivery systems termed immunopotentiating reconstituted influenza virosomes (IRIVs) and their use as vaccines. Particular attention is paid to the currently licensed Epaxal and Inflexal V, good examples of the improvements being made in vaccinology. Alternative uses of virosomes such as peptide delivery, cytosolic drug delivery and gene delivery are also considered, highlighting the flexibility of the IRIV formulation and method of action. The paper concludes with consideration of alternative novel approaches to vaccinology including bacterial carriers for DNA vaccines, recombinant MV vaccines and polysaccharide-protein conjugates.

In vitro studies of core peptide-bearing immunopotentiating reconstituted influenza virosomes as a non-live prototype vaccine against hepatitis C virus

Evidence from both animal and human viral diseases indicate that cytotoxic T lymphocytes (CTL) are crucial in antiviral defense. However, a major problem to generate cytotoxic immunity is that in vivo exogenous antigens are usually presented via MHC class II pathway and normally fail to induce CTL. The aim of this study is to describe a novel non-live prototype vaccine based on immunopotentiating reconstituted influenza virosomes (IRIV) as vehicles to deliver HLA-A*0201-restricted hepatitis C virus (HCV) peptides (core 35-44 and 131-140) into the cytoplasm of at least three different target cell types [including T2, a transporter associated with antigen processing (TAP)-deficient cell line] resulting in MHC class I peptide presentation and lysis by peptide-specific CTL lines. Comparison of kinetics and analysis of the influence of peptide-stripping and Brefeldin A (BFA) reveal that there exists an endogenous, TAP-independent and BFA-sensitive pathway for virosomally delivered peptides. Moreover, virosomes containing influenza matrix peptide 58-66 can efficiently re-stimulate in vivo primed CTL and, importantly, IRIV containing HCV core peptides can even prime CTL from peripheral blood mononuclear cells of HCV(-) healthy blood donors in vitro. The fact that in vitro primed CTL are also able to specifically lyse target cells infected with recombinant vaccinia virus encoding the HCV core protein is of great importance for future studies based on in vivo mouse models. One of the most evident advantages of the virosomes in vivo will be their capability to protect the incorporated peptide from a large variety of degrading proteases.

Mucosal [SIgA] and serum [IgG] immunologic responses in the community after a single intra-nasal immunization with a new inactivated trivalent influenza vaccine

Influenza morbidity affects entire populations, imposing an enormous burden in economic terms from working days lost. Protection afforded by current vaccines is often unsatisfactory and many individuals remain averse to injections. To counter these drawbacks, we tested an inactive intra-nasal trivalent influenza vaccine on 182 vaccinated and 92 placebo subjects in the community. On study completion 73 and 66% of the subjects were immune to the vaccine's two A strains, 40% (> or=1:40) and 65% (> or=1:20) to its B strain; 30-40% demonstrated a 4x hemagglutination inhibition (HAI) titer increase; GMT titers increased 2.2-2.5x. About 50% of those initially non-immune became immune. A local antibody response to the three vaccine strains was recorded in 31-44% of vaccinees in which 57, 68 and 54% exhibited a mucosal and/or serum antibody response to the A/Johannesburg, A/Nanchang and B/Harbin strains, respectively. A higher dose (40mg) of A/Johannesburg in the vaccine did not influence response. The new vaccine was safe, without side-effects, and offered reasonable protection after one dose. It could thus play an important role in increasing enrollment into immunization programs.

Development of vaccines against common colds

Respiratory tract viruses are particularly significant causes of illness and death in children and in the elderly. Vaccines offer the possibility of decreasing the severity and complications of viral respiratory disease, but development has been delayed by numerous factors. First, there are more than 200 serologically distinct RNA and DNA virus species and strains which cause an essentially similar spectrum of disease. Some re-infect at high efficiency despite little antigenic variation, while others exhibit extensive coat protein variability. Vaccine candidates show variable efficacy in partially immune adults, the immunocompromised and the elderly, and may be ineffective or pathogenic in neonates or in the presence of maternal antibodies. However, effective childhood vaccines are essential to prevent severe disease due to respiratory syncytial virus (RSV) and parainfluenza and to reduce virus transmission to adults. A number of promising vaccines are in clinical trial, and it is likely that vaccines against RSV and parainfluenza will be licensed within the next 5-10 years. Mucosal delivery and the use of novel adjuvants offers the prospect of better vaccines against influenza. The ultimate goal is to develop multivalent mucosal vaccines offering protection against a spectrum of respiratory infections.

An open-label comparison of the immunogenicity and tolerability of intranasal and intramuscular formulations of virosomal influenza vaccine in healthy adults

BACKGROUND

Many intramuscular inactivated influenza vaccines achieve suboptimal results in the prevention of respiratory disease and influenza complications. This has led to the current interest in developing effective oral or intranasal preparations.

OBJECTIVE

This study compared the immunogenicity and tolerability of intranasal and intramuscular formulations of virosomal subunit influenza vaccine in healthy adults. It also assessed the immunogenicity and tolerability of 3 different production lots of the intranasal vaccine containing Escherichia coli heat-labile toxin adjuvant.

METHODS

This was a multicenter, Phase I, randomized, open-label pilot study in which the primary end point was immunogenicity (hemagglutination-inhibition [HI] antibody assay on days 1 and 29). The secondary end point was the frequency of adverse events (AEs). Subjects were assigned to 4 vaccination groups: groups AI, AII, and AIII received intranasal influenza vaccine from batches that differed in the hemagglutinin and neuraminidase strains used, and group B received intramuscular virosomal subunit vaccine. Assessments of health status, hematology, biochemistry, body temperature, heart rate, blood pressure, and incidence of AEs were made on days 1, 8, and 29, and serology was assessed on days 1 and 29.

RESULTS

The study enrolled 88 subjects. All 3 production lots of intranasal vaccine induced an immune response to most of the viral strains administered (A/Singapore, A/Texas, A/Wuhan, B/Beijing), with no notable immunogenic differences between lots. After intranasal vaccination, geometric mean titers (GMT) increased 2.7-fold against A/Singapore (group AI); 1.8- and 3.1-fold against A/Texas (groups AII and AIII, respectively); 1.9- to 2.4-fold against A/Wuhan; and 1.5- to 1.7-fold against B/Beijing. After intramuscular vaccination. GMT increased 11.3-, 6.3-, and 2.7-fold against A/Texas, A/Wuhan, and B/Beijing, respectively. Seroprotection (HI antibody titers > or = 1:40 in > 70% of those vaccinated) was achieved against all strains in the group that received intramuscular vaccination, against A/Wuhan in all groups that received intranasal vaccination, and against A/Texas in group AII. Both vaccine formulations were well tolerated. Intranasal vaccination was associated with a low incidence ( < 20%) of nasal AEs.

CONCLUSIONS

Both the intranasal and intramuscular vaccinations elicited a systemic immune response and were well tolerated. The different batches of intranasal vaccine showed a similar immunogenic profile. Intranasal administration may be preferred to intramuscular administration by some patients.

Perspectives: towards a peptide-based vaccine against hepatitis C virus

Hepatitis C virus (HCV) is a widespread infectious disease in humans with the negative implication of becoming chronic in most persons. Patients infected with HCV are at risk of liver cirrhosis or hepatocellular carcinoma at later stages. In contrast to hepatitis A and hepatitis B, there is no immunization yet available, neither prophylactic nor therapeutic. Thus, there is an urgent need to develop a safe, protective vaccine against this fatal disease. Developing countries are even more at risk for HCV. There are currently a number of scientific approaches aimed towards solving this problem. Taking both risks and costs of immunization into consideration, a peptide-based vaccine may be a reasonable prophylactic protection. Also, it might be of therapeutic use in already infected patients by increasing a specific CTL response against HCV. In our lab, we are focusing on immunopotentiating reconstituted influenza virosomes (IRIVs) as carriers for immunogenic HLA-A2-restricted core epitopes to induce peptide-specific cytotoxic T lymphocytes (CTLs). The IRIVs are similar to liposomes, but in addition contain influenza-derived hemagglutinin and neuraminidase on their outer surface which makes them fusogenic, thus, permitting antigen delivery to host cells. So far, virosomes have been successfully used for vaccine development and as a result a virosomal vaccine against both influenza virus (Inflexal) BERNA) and hepatitis A virus (HAV) (Epaxal) BERNA) already exist on the market. This paper focuses on the importance of development of a successful vaccine against HCV and, more specifically, we discuss the use, advantages and disadvantages of a peptide-based vaccine. A brief report of our latest findings will be included.

Review of intranasal influenza vaccine

Influenza viruses cause costly recurrent annual epidemics. Current efforts to control the morbidity and mortality associated with influenza outbreaks are based on the use of annual intramuscularly administered inactivated vaccines which are not only painful to administer, but are suboptimal in efficacy. This paper reviews the composition, safety analysis, rates of adverse events, immune response and protective efficacy of a new inactivated intranasal influenza vaccine.

Influenza: vaccination and treatment

Few conditions exert such an enormous toll of absenteeism, suffering, medical consultations, hospitalization, death and economic loss as influenza. Patients at high risk of complications and mortality include the elderly and those with pre-existing cardiopulmonary disease. The outbreak in 1997 in Hong Kong, of avian H5N1 influenza in man, which resulted in six deaths among 18 hospitalized cases, and the recent isolation of H9N2 viruses from two children in Hong Kong, are reminders that preparation must be made for the next pandemic. Since the 1970s, efforts to control influenza have mostly focussed on the split product and surface antigen vaccines. These vaccines are of proven efficacy in healthy adults and are effective in elderly people with and without medical conditions putting them at high risk of complications and death following influenza infection. However, vaccine coverage is patchy and often low, and outbreaks of influenza are not uncommon in well-immunized residents of nursing homes. New vaccines and methods of vaccine delivery are being developed in attempts to overcome the limitations of existing vaccines. The antiviral drugs amantadine and rimantadine were developed in the 1960s, but have not been used widely due to their spectrum of activity, rapid emergence of resistance, and adverse effects associated with amantadine. The site of enzyme activity of the influenza neuraminidase is highly conserved between types, subtypes and strains of influenza and has emerged as the target of an exciting new class of antiviral agents that are effective both prophylactically and as therapy.

Comparison of three different influenza vaccines in institutionalised elderly

The reactogenicity and the humoral immune response to three influenza vaccines were evaluated in a randomised, double-blind trial at nursing homes in north-east Italy in winter 1998-1999. Of the 285 subjects, who completed the follow-up, 93 were administered virosomal vaccine, 99 received MF59-adjuvanted vaccine and 93 had split vaccine. Ten subjects (0.3%) reported local and/or systemic reactions in the first week after immunisation. After 4 weeks, protection rates (> or = 40) were near 100% for the H1N1 and B strain and 76.0% against H3N2. The MF59-adjuvanted vaccine group had higher geometric mean titres than the other two. However, the true clinical benefit of the new adjuvanted vaccine should be further substantiated by comparative protective studies. Our results suggest that immune response to influenza vaccination in institutionalised elderly is satisfactory.

Ensuring vaccine safety in immunization programmes--a WHO perspective

Ever since vaccines were firstly used against smallpox, adverse events following immunization have been reported. As immunization programmes expand to reach even the most remote communities in the poorest countries, it is likely that many more events will be temporally linked with vaccine administration. Furthermore, the profound shift in the general public and media interest in adverse events may lead to undue concerns and allegations which may ultimately jeopardize immunization programmes world-wide. While the health professional has understood this issue for some time, the public and the media have now also become all too aware of the significance of vaccine-related adverse events. The familiar vaccines, well-tested over decades, have not changed--but the perception regarding their safety has shifted. Claims outrageous or reasonable are being made against both the old and the newly-introduced vaccines. At the same time, the immunological and genetic revolution of the last decade may well bring to our notice some hypothetical risks that need to be addressed at pre-clinical level. WHO has been at the leading edge to guarantee vaccine safety for the last 30 years and will continue to do so. The Organization's plans for the next decade and beyond include the Safe Injection Global Network (SIGN), the development and introduction of safer technologies, and the prevention, early detection and management of AEFIs. The new technologies include needle-containing injection devices such as the autodisable syringe, as well as mucosal and transcutaneous immunization. Training will continue to be at the centre of WHO's efforts, limiting human error to a minimum. Mechanisms have been set in place to detect and respond to new and unforeseen events occurring. Above all, there is a willingness to respond to new climates and new technologies so that the Organization is in the best position to ensure safe immunization for all the world's children.

Immunogenicity and safety of three commercial influenza vaccines in institutionalized elderly

Influenza is a leading cause of morbidity and mortality in elderly people. This prospective, observed-blind, randomized, multicenter trial compares the immunogenicity and safety of three influenza vaccines in a sample of 635 elderly residents of four nursing homes in Milano (Italy). All vaccines were well tolerated: no serious adverse events were recorded, and a small number (9 subjects) of local and systemic reactions were observed. Twenty-nine oropharyngeal swabs were taken during the season from ILI (influenza-like illness) patients, none of whom was positive for influenza and other respiratory viruses. Immunogenicity was evaluated in a subgroup of 111 subjects with blood samples obtained just before vaccination and after 4 and 12 weeks. The adjuvanted vaccines, subunit vaccine with MF59 (a-SUV) and virosome subunit vaccine (v-SUV), induced a higher antibody response than whole virus vaccine (WVV). There was no significant difference between groups that received a-SUV and v-SUV, but the a-SUV group had higher values of geometric mean titres than the v-SUV group for H1N1 and B influenza strains. These findings suggest that influenza vaccination is effective, and they underscore the importance of vaccination programs for institutionalized elderly. Further studies are needed to compare other adjuvanted vaccines in order to define their different properties.

Technologies to improve immunisation safety

Ever since a vaccine was first used against smallpox, adverse events following immunisation have been reported. Adverse reactions may be caused by a fault in vaccine production, idiosyncratic responses or unsafe handling and vaccine administration practices. Technological advances that promise to bypass many of the dangers currently associated with vaccine administration are described. Plans for the next decade and beyond include developing injection-free systems for vaccine delivery that overcome the limitations of current immunisation programmes and help prevent programmatic mistakes. Also under development are new parenteral administration devices such as the auto-disable syringe and the mono-dose pre-filled device, and mucosal and transcutaneous immunisation systems. Training needs to be at the forefront of efforts to limit human error. Above all, there must be a willingness to respond to new climates and new technologies in order to ensure safe immunisation of children globally.

Immunopotentiating of mucosal and systemic antibody responses in mice by intranasal immunization with HLT-combined influenza virosomal vaccine

The mucosal vaccination strategy against influenza has been investigated by using influenza virosomal vaccine (IRIV) combined with two different adjuvants: the procholeragenoid (PCG) and the Escherichia coli heat labile toxin (HLT). A comparative study has been carried out on mice administered intranasally with these different formulations of influenza vaccine. PCG appears less effective than HLT in inducing an IgG response, but both the adjuvants elicit mucosal adjuvant activity inducing s-IgA in the upper respiratory tract. On the contrary, only HLT when administered intranasally to mice with influenza virosomes stimulates the production of s-IgA in the lower respiratory tract thereby providing a better protection against primary infection of the respiratory system. Both HLT and PCG enhance the production of IFN-gamma in the respiratory tract, nevertheless HLT appears more efficacious as a mucosal adjuvant.

Comparison of immunogenicity and safety of a virosome influenza vaccine with those of a subunit influenza vaccine in pediatric patients with cystic fibrosis

The objective of this study was to compare the immunogenicity and safety of a single-dose regimen and a two-dose regimen of a trivalent virosome influenza vaccine (Inflexal Berna V) with those of a trivalent subunit influenza vaccine (Influvac) in children and adolescents with cystic fibrosis (CF). In an open, randomized, multicenter study with parallel groups, 11 young children with CF (1 to 6 years old) and 53 older children and adolescents with CF (>6 years old) were randomly assigned to one of the following immunization regimens: virosome vaccine at 0.5 ml on study day 0 or 0.25 ml on days 0 and 28 or a standard regimen of subunit vaccine, i. e., 0.5 ml on day 0 for older children and 0.25 ml on days 0 and 28 for younger children. Safety assessments, i.e., recording of systemic and local adverse events (AEs) and vital signs, were made for a 5-day observation period after each immunization. Hemagglutination inhibition (HI) titers were determined at baseline and 4 weeks after the single-dose and the two-dose immunizations, respectively. Immunogenicity was assessed according to the criteria of the European Agency for the Evaluation of Medicinal Products (EMEA). Both vaccines induced comparable HI antibody titers. Seroconversion (> or =4-fold rise in HI antibody titers, reaching a titer of > or =1:40) was achieved in 41 to 100% of the participants. Seroprotection (HI titer, > or =1:40) and a >2.5-fold increase in geometric mean titers were achieved in 100% of the participants. Thus, all three EMEA requirements for influenza vaccine efficacy were met by all treatment groups and for both vaccines. The virosome vaccine, when administered as a single dose, seemed to induce superior immunogenicity compared with the standard pediatric two-dose regimen. Totals of 42 and 57% of vaccinees receiving virosome and subunit vaccines, respectively, reported at least one local AE (predominantly pain). Totals of 84 and 71% of subjects receiving virosome and subunit vaccines, respectively, complained in response to questions of at least one systemic AE (mainly cough, fatigue, coryza, or headache). The majority of events were mild or moderate and lasted 1 or 2 days only. No obvious relationship was found between AE reporting rate and vaccine formulation, age group, or dose regimen. The relatively high AE reporting rate seemed to be partly related to the symptomatology of the underlying CF disease. In summary, the virosome and subunit vaccines induced in both age groups and against all three influenza strains an efficient immune response and were well tolerated by the children and adolescents with CF.

Influenza A pandemics of the 20th century with special reference to 1918: virology, pathology and epidemiology

Influenza A virus initiated worldwide epidemics (pandemics) in 1918, 1957, 1968 and 1977. A revised calculation of the 1918-1919 pandemic estimates that 40 million persons died and 500 million were infected. The mortalities in 1957 and 1968 were nearly 6 million. Biological and genetic characteristics of the causative agents of the more recent pandemics, have been well studied but little is known about the causative agent of the Great Pandemic in 1918. Genetic characterisation of the 1918 virus has been achieved by sourcing virus RNA from formalin fixed lung samples or by exhuming frozen victims of the outbreak from Arctic regions. Initial analysis of the HA gene from two USA sources indicates a virus related to swine and human influenza with no base insertion at the HA1-HA2 cleavage junction which, at least in avian influenza A, characterises high virulence. Important unanswered questions are whether the 1918 virus spread pantropically perhaps to include the brain and hence cause encephalitis including the later lethargic forms, or whether infection was confined to the respiratory tract. Re-examination of reports of respiratory disease in England and France in 1916-1917 may indicate a non-Spanish origin of the pandemic and a period of 2 years for the virus to be seeded worldwide. In contrast the other two pandemic viruses in 1957 and 1968 appeared to originate in Asia. New anti-neuraminidase drugs in conjunction with amantadine and novel developments with influenza vaccines would be expected to ameliorate the disease in a future pandemic.

Respiratory viral infections in the elderly

Viral respiratory infections represent a significant challenge for those interested in improving the health of the elderly. Influenza continues to result in a large burden of excess morbidity and mortality. Two effective measures, inactivated influenza vaccine, and the antiviral drugs rimantadine and amantadine, are currently available for control of this disease. Inactivated vaccine should be given yearly to all of those over the age of 65, as well as younger individuals with high-risk medical conditions and individuals delivering care to such persons. Live, intranasally administered attenuated influenza vaccines are also in development, and may be useful in combination with inactivated vaccine in the elderly. The antiviral drugs amantadine and rimantadine are effective in the treatment and prevention of influenza A, although rimantadine is associated with fewer side-effects. Recently, the inhaled neuraminidase inhibitor zanamivir, which is active against both influenza A and B viruses, was licensed for use in uncomplicated influenza. The role of this drug in treatment and prevention of influenza in the elderly remains to be determined. Additional neuraminidase inhibitors are also being developed. In addition, to influenza, respiratory infections with respiratory syncytial virus, parainfluenza virus, rhinovirus, and coronavirus have been identified as potential problems in the elderly. With increasing attention, it is probable that the impact of these infections in this age group will be more extensively documented. Understanding of the immunology and pathogenesis of these infections in elderly adults is in its infancy, and considerable additional work will need to be performed towards development of effective control measures.

BERNA: a century of immunobiological innovation

At the time the Swiss Serum and Vaccine Institute Berne (BERNA) was found in 1898, few vaccines or immune globulins were available. This short list included vaccines against cholera, typhoid fever, plague, smallpox and rabies and equine anti-tetanus and diphtheria immune globulins. Furthermore, their use was restricted due to limited production capacity, uncertainty regarding safety and no public health infrastructure to promote their utilization. Today, safe and effective vaccines exist for more than 30 infectious diseases while human hyperimmune globulins exist to treat or prevent rabies, tetanus, respiratory syncytial virus, cytomegalovirus, hepatitis A, hepatitis B, and herpes virus (Varicella zoster) infections. Throughout its 100 years of existence, BERNA has played a key role in the evolution of the field by introducing novel technology leading to safer, and more efficacious vaccines. It was a pioneer in the development of freeze dried smallpox vaccine free from bacterial contamination. The Salmonella typhi Ty21a typhoid fever vaccine strain demonstrated that oral immunization against enteric bacterial pathogens was not only feasible, but could be accomplished with a virtual lack of attendant adverse reactions. This finding has served as an impetus to develop other live attenuated bacterial strains not only as vaccines, but also as vectors for vaccine antigens and gene therapy. One such example is Vibrio cholerae CVD 103-HgR, the first live vaccine for human use derived through recombinant DNA technology. Subsequent studies have shown that these two vaccine strains can be combined without sacrificing safety or immunogenicity, setting the cornerstone for combined orally administered vaccines. Recently, a novel vaccine antigen delivery system, termed virosomes, has been utilized to construct hepatitis A and influenza vaccines. Such vaccines elicit fewer local adverse reactions than their classical counterparts and display enhanced immunogenicity. Virosome-formulated influenza vaccine has also been shown to be safe and immunogenic, when administered by the intranasal route.

Phase 1 evaluation of intranasal virosomal influenza vaccine with and without Escherichia coli heat-labile toxin in adult volunteers

Virosomal vaccines were prepared by extracting hemagglutinin (HA) and neuraminidase from influenza virus and incorporating it in the membranes of liposomes composed of phosphatidylcholine. Two intranasal spray vaccine series were prepared: one series comprised 7.5 micrograms of HA of each of three strains recommended by the World Health Organization and 1 microgram of Escherichia coli heat-labile toxin (HLT), and the other contained the HA without HLT. In addition, a third vaccine preparation contained 15 micrograms of HA and 2 micrograms of HLT. The parenteral virosomal vaccine contained 15 micrograms of HA without additional adjuvant. The immunogenicity of a single spray vaccination (15 micrograms of HA and 2 micrograms of HLT) was compared with that of two vaccinations (7.5 micrograms of HA with or without 1 microgram of HLT) with an interval of 1 week in 60 healthy working adults. Twenty volunteers received one parenteral virosomal vaccine. Two nasal spray vaccinations with HLT-adjuvanted virosomal influenza vaccine induced a humoral immune response which was comparable to that with a single parenteral vaccination. A significantly higher induction of influenza virus-specific immunoglobulin A was noted in the saliva after two nasal applications. The immune response after a single spray vaccination was significantly lower. It could be shown that the use of HLT as a mucosal adjuvant is necessary to obtain a humoral immune response comparable to that with parenteral vaccination. All vaccines were well tolerated.