A novel influenza subunit vaccine composed of liposome-encapsulated haemagglutinin/neuraminidase and IL-2 or GM-CSF. II. Induction of TH1 and TH2 responses in mice

AMDV Vaccine: Challenges and Perspectives

Aleutian mink disease virus (AMDV) is known to cause the most significant disease in the mink industry. It is globally widespread and manifested as a deadly plasmacytosis and hyperglobulinemia. So far, measures to control the viral spread have been limited to manual serological testing for AMDV-positive mink. Further, due to the persistent nature of this virus, attempts to eradicate Aleutian disease (AD) have largely failed. Therefore, effective strategies to control the viral spread are of crucial importance for wildlife protection. One potentially key tool in the fight against this disease is by the immunization of mink against AMDV. Throughout many years, several researchers have tried to develop AMDV vaccines and demonstrated varying degrees of protection in mink by those vaccines. Despite these attempts, there are currently no vaccines available against AMDV, allowing the continuation of the spread of Aleutian disease. Herein, we summarize previous AMDV immunization attempts in mink as well as other preventative measures with the purpose to shed light on future studies designing such a potentially crucial preventative tool against Aleutian disease.

Mucosal Immunity and Protective Efficacy of Intranasal Inactivated Influenza Vaccine Is Improved by Chitosan Nanoparticle Delivery in Pigs

Annually, swine influenza A virus (SwIAV) causes severe economic loss to swine industry. Currently used inactivated SwIAV vaccines administered by intramuscular injection provide homologous protection, but limited heterologous protection against constantly evolving field viruses, attributable to the induction of inadequate levels of mucosal IgA and cellular immune responses in the respiratory tract. A novel vaccine delivery platform using mucoadhesive chitosan nanoparticles (CNPs) administered through intranasal (IN) route has the potential to elicit strong mucosal and systemic immune responses in pigs. In this study, we evaluated the immune responses and cross-protective efficacy of IN chitosan encapsulated inactivated SwIAV vaccine in pigs. Killed SwIAV H1N2 (δ-lineage) antigens (KAg) were encapsulated in chitosan polymer-based nanoparticles (CNPs-KAg). The candidate vaccine was administered twice IN as mist to nursery pigs. Vaccinates and controls were then challenged with a zoonotic and virulent heterologous SwIAV H1N1 (γ-lineage). Pigs vaccinated with CNPs-KAg exhibited an enhanced IgG serum antibody and mucosal secretory IgA antibody responses in nasal swabs, bronchoalveolar lavage (BAL) fluids, and lung lysates that were reactive against homologous (H1N2), heterologous (H1N1), and heterosubtypic (H3N2) influenza A virus strains. Prior to challenge, an increased frequency of cytotoxic T lymphocytes, antigen-specific lymphocyte proliferation, and recall IFN-γ secretion by restimulated peripheral blood mononuclear cells in CNPs-KAg compared to control KAg vaccinates were observed. In CNPs-KAg vaccinated pigs challenged with heterologous virus reduced severity of macroscopic and microscopic influenza-associated pulmonary lesions were observed. Importantly, the infectious SwIAV titers in nasal swabs [days post-challenge (DPC) 4] and BAL fluid (DPC 6) were significantly (p < 0.05) reduced in CNPs-KAg vaccinates but not in KAg vaccinates when compared to the unvaccinated challenge controls. As well, an increased frequency of T helper memory cells and increased levels of recall IFNγ secretion by tracheobronchial lymph nodes cells were observed. In summary, chitosan SwIAV nanovaccine delivered by IN route elicited strong cross-reactive mucosal IgA and cellular immune responses in the respiratory tract that resulted in a reduced nasal viral shedding and lung virus titers in pigs. Thus, chitosan-based influenza nanovaccine may be an ideal candidate vaccine for use in pigs, and pig is a useful animal model for preclinical testing of particulate IN human influenza vaccines.

A genetically adjuvanted influenza B virus vector increases immunogenicity and protective efficacy in mice

The existence of multiple antigenically distinct types and subtypes of influenza viruses allows the construction of a multivalent vector system for the mucosal delivery of foreign sequences. Influenza A viruses have been exploited successfully for the expression of extraneous antigens as well as immunostimulatory molecules. In this study, we describe the development of an influenza B virus vector whose functional part of the interferon antagonist NS1 was replaced by human interleukin 2 (IL2) as a genetic adjuvant. We demonstrate that IL2 expressed by this viral vector displays immune adjuvant activity in immunized mice. Animals vaccinated with the IL2 viral vector showed an increased hemagglutination inhibition antibody response and higher protective efficacy after challenge with a wild-type influenza B virus when compared to mice vaccinated with a control virus. Our results demonstrate that it is feasible to construct influenza B vaccine strains expressing immune-potentiating foreign sequences from the NS genomic segment. Based on these data, it is now hypothetically possible to create a trivalent (or quadrivalent) live attenuated influenza vaccine in which each component expresses a selected genetic adjuvant with tailored expression levels.

A novel subunit vaccine co-expressing GM-CSF and PCV2b Cap protein enhances protective immunity against porcine circovirus type 2 in piglets

Porcine circovirus type 2 (PCV2) causes porcine circovirus-associated disease. Capsid (Cap) protein of PCV2 is the principal immunogenic protein that induces neutralizing antibodies and protective immunity. GM-CSF is an immune adjuvant that enhances responses to vaccines. In this study, recombinant baculoviruses Ac-Cap and Ac-Cap-GM-CSF expressing the Cap protein alone and co-expressing the Cap protein and porcine GM-CSF, respectively, were constructed successfully. The target proteins were analyzed by western blotting and IFA. Further, these proteins were confirmed by electron microscopy, which showed that Cap proteins could self-assemble into virus-like particles having diameters of 17-25nm. Animal experiments showed that pigs immunized with Cap-GM-CSF subunit vaccine showed significantly higher levels of PCV2-specific antibodies and neutralizing antibodies than pigs immunized with the Cap subunit vaccine and a commercial vaccine (Ingelvac CircoFLEX; P<0.05). After PCV2 wild strain challenged, Pigs receiving the Cap-GM-CSF subunit vaccine showed significantly higher average daily weight gain after wild-type PCV2 challenge than pigs receiving the other three vaccines (P<0.05). None of PCV2 DNA was detected in all immunized animals, except control animals immunized with phosphate-buffered saline. These results indicated that GM-CSF was a powerful immunoadjuvant for PCV2 subunit vaccines because it enhanced humoral immune response and improved immune protection against PCV2 infection in pigs. Thus, the novel Cap-GM-CSF subunit vaccine has the potential to be used as an effective and safe vaccine candidate against PCV2 infection.

Design of alternative live attenuated influenza virus vaccines

Each year due to the ever-evolving nature of influenza, new influenza vaccines must be produced to provide protection against the influenza viruses in circulation. Currently, there are two mainstream strategies to generate seasonal influenza vaccines: inactivated and live-attenuated. Inactivated vaccines are non-replicating forms of whole influenza virus, while live-attenuated vaccines are viruses modified to be replication impaired. Although it is widely believed that by inducing both mucosal and humoral immune responses the live-attenuated vaccine provides better protection than that of the inactivated vaccine, there are large populations of individuals who cannot safely receive the LAIV vaccine. Thus, safer LAIV vaccines are needed to provide adequate protection to these populations. Improvement is also needed in the area of vaccine production. Current strategies relying on traditional tissue culture-based and egg-based methods are slow and delay production time. This chapter describes experimental vaccine generation and production strategies that address the deficiencies in current methods for potential human and agricultural use.

Future directions for the development of Chlamydomonas-based vaccines

Besides serving as a valuable model in biological sciences, Chamydomonas reinhardtii has been used during the last decade in the biotechnology arena to establish models for the low cost production of vaccines. Antigens from various pathogens including Plasmodium falciparum, foot and mouth disease virus, Staphylococcus aureus, classical swine fever virus (CSFV) as well as some auto-antigens, have been produced in C. reinhardtii. Although some of them have been functionally characterized with promising results, this review identifies future directions for the advancement in the exploitation of this robust and safe vaccine production platform. The present analysis reflects that important immunological implications exist for this system and remain unexplored, including the possible adjuvant effects of algae biomolecules, the effect of bioencapsulation on immunogenicity and the possible development of whole-cell vaccines as an approach to trigger cytotoxic immune responses. Recently described molecular strategies that aim to optimize the expression of nuclear-encoded target antigens are also discussed.

Adjuvanted influenza vaccines

Influenza is one of the most common causes of human morbidity and mortality that is preventable by vaccination. Immunization with available vaccines provides incomplete protection against illness caused by influenza virus, especially in high-risk groups such as the elderly and young children. Thus, more efficacious vaccines are needed for the entire population, and all the more so for high-risk groups. One way to improve immune responses and protection is to formulate the vaccine with antigen carriers and/or adjuvants, which can play an important role in improving immune responses and delivery to antigen-presenting cells, especially for a vaccine like influenza that is based on protein antigens usually administered without a carrier or adjuvant. In this review, the authors present an overview of available vaccines, focusing on research and development of new adjuvants used in influenza vaccines, as well as adjuvanted influenza vaccines aimed to improve immune responses, protection and breadth of coverage for influenza.

Adjuvant effect of cationic liposomes for subunit influenza vaccine: influence of antigen loading method, cholesterol and immune modulators

Cationic liposomes are potential adjuvants for influenza vaccines. In a previous study we reported that among a panel of cationic liposomes loaded with influenza hemagglutinin (HA), DC-Chol:DPPC (1:1 molar ratio) liposomes induced the strongest immune response. However, it is not clear whether the cholesterol (Chol) backbone or the tertiary amine head group of DC-Chol was responsible for this. Therefore, in the present work we studied the influence of Chol in the lipid bilayer of cationic liposomes. Moreover, we investigated the effect of the HA loading method (adsorption versus encapsulation) and the encapsulation of immune modulators in DC-Chol liposomes on the immunogenicity of HA. Liposomes consisting of a neutral lipid (DPPC or Chol) and a cationic compound (DC-Chol, DDA, or eDPPC) were produced by film hydration-extrusion with/without an encapsulated immune modulator (CpG or imiquimod). The liposomes generally showed comparable size distribution, zeta potential and HA loading. In vitro studies with monocyte-derived human dendritic cells and immunization studies in C57Bl/6 mice showed that: (1) liposome-adsorbed HA is more immunogenic than encapsulated HA; (2) the incorporation of Chol in the bilayer of cationic liposomes enhances their adjuvant effect; and (3) CpG loaded liposomes are more efficient at enhancing HA-specific humoral responses than plain liposomes or Alhydrogel.

Mucosal Immune System and M Cell-targeting Strategies for Oral Mucosal Vaccination

Vaccination is one of the most effective methods available to prevent infectious diseases. Mucosa, which are exposed to heavy loads of commensal and pathogenic microorganisms, are one of the first areas where infections are established, and therefore have frontline status in immunity, making mucosa ideal sites for vaccine application. Moreover, vaccination through the mucosal immune system could induce effective systemic immune responses together with mucosal immunity in contrast to parenteral vaccination, which is a poor inducer of effective immunity at mucosal surfaces. Among mucosal vaccines, oral mucosal vaccines have the advantages of ease and low cost of vaccine administration. The oral mucosal immune system, however, is generally recognized as poorly immunogenic due to the frequent induction of tolerance against orally-introduced antigens. Consequently, a prerequisite for successful mucosal vaccination is that the orally introduced antigen should be transported across the mucosal surface into the mucosa-associated lymphoid tissue (MALT). In particular, M cells are responsible for antigen uptake into MALT, and the rapid and effective transcytotic activity of M cells makes them an attractive target for mucosal vaccine delivery, although simple transport of the antigen into M cells does not guarantee the induction of specific immune responses. Consequently, development of mucosal vaccine adjuvants based on an understanding of the biology of M cells has attracted much research interest. Here, we review the characteristics of the oral mucosal immune system and delineate strategies to design effective oral mucosal vaccines with an emphasis on mucosal vaccine adjuvants.

Particle-mediated delivery of cytokines for immunotherapy

The ability of cytokines to direct the immune response to vaccination, infection and tumors has motivated their use in therapy to augment or shape immunity. To avoid toxic side effects associated with systemic cytokine administration, several approaches have been developed using particle-encapsulated cytokines to deliver this cargo to specific cell types and tissues. Initial work used cytokine-loaded particles to deliver proinflammatory cytokines to phagocytes to enhance antimicrobial and antitumor responses. These particles have also been used to create a cytokine depot at a local site to supplement prophylactic or antitumor vaccines or injected directly into solid tumors to activate immune cells to eliminate established tumors. Finally, recent advances have revealed that paracrine delivery of cytokines directly to T cells has the potential to enhance T-cell mediated therapies. The studies reviewed here highlight the progress in the last 30 years that has established the potential of particle-mediated cytokine immunotherapy.

Formulation and evaluation of oral microparticulate ovarian cancer vaccines

Ovarian cancer is the fifth most leading cause of cancer related deaths in women in the US. Customized immunotherapeutic strategies may serve as an alternative method to control the recurrence or progression of ovarian cancer and to avoid severe adverse effects of chemotherapy. In this study, a microparticulate vaccine using whole cell lysate of a murine ovarian cancer cell line, ID8 was prepared with the use of a spray dryer. These particles were designed for oral delivery using enteric polymers such as methacrylic copolymer, Eudragit(®) FS30D and hydroxyl propyl methyl cellulose acetate succinate. These particles were targeted for uptake via microfold cell (M-cell) in Peyer's patches of small intestine using M-cell targeting ligand, Aleuria aurantia lectin. The interleukins (ILs) such as IL-2 and IL-12 were added to the vaccine formulation to further enhance the immune response. The particles obtained were of 1.58±0.62 μm size with a charge of 12.48±2.32 mV. The vaccine efficacy was evaluated by administering the particles via oral route to C57BL/6 female mice. At the end of vaccination, mice were challenged with live tumor cells. Vaccinated mice showed significant (around six-fold) retardation of tumor volume in comparison to non-vaccinated animals for 3 weeks after the tumor challenge (p<0.001). The serum IgG antibody levels were found to be elevated in case of vaccinated animals in comparison to non-vaccinated group (p<0.05). Analysis of IgG1 titers (indicative of Th2 response) and IgG2a titers (indicative of Th1 response) showed a mixed Th1 and Th2 immune response in case vaccine alone and Th2 response in case of vaccine with interleukins group. Moreover, CD8+ T-cell, CD4+ T-cell and B-cell populations in different lymphatic organs were elevated in case of vaccinated mice. Thus, whole cell lysate vaccine microparticles formulated by spray drying could trigger humoral as well as cellular immune response when administered orally. Such vaccine could potentially be an effective treatment for patients with residual tumor or high tumor-relapse probability.

Human influenza vaccines and assessment of immunogenicity

Influenza is responsible for the infection of approximately 20% of the population every season and for an annual death toll of approximately half a million people. The most effective means for controlling infection and thereby reducing morbidity and mortality is vaccination by injection with an inactivated vaccine, or by intranasal administration of a live-attenuated vaccine. Protection is not always optimal and there is a need for the development of new vaccines with improved efficacy and for the expansion of enrollment into vaccination programs. An overview of old and new vaccines is presented. Methods of monitoring immune responses such as hemagglutination-inhibition, ELISA and neutralization tests are evaluated for their accuracy in the assessment of current and new-generation vaccines.

Multistrain influenza protection induced by a nanoparticulate mucosal immunotherapeutic

All commercial influenza vaccines elicit antibody responses that protect against seasonal infection, but this approach is limited by the need for annual vaccine reformulation that precludes efficient responses against epidemic and pandemic disease. In this study we describe a novel vaccination approach in which a nanoparticulate, liposome-based agent containing short, highly conserved influenza-derived peptides is delivered to the respiratory tract to elicit potent innate and selective T cell-based adaptive immune responses. Prepared without virus-specific peptides, mucosal immunostimulatory therapeutic (MIT) provided robust, but short-lived, protection against multiple, highly lethal strains of influenza in mice of diverse genetic backgrounds. MIT prepared with three highly conserved epitopes that elicited virus-specific memory T-cell responses but not neutralizing antibodies, termed MITpep, provided equivalent, but more durable, protection relative to MIT. Alveolar macrophages were more important than dendritic cells in determining the protective efficacy of MIT, which induced both canonical and non-canonical antiviral immune pathways. Through activation of airway mucosal innate and highly specific T-cell responses, MIT and MITpep represent novel approaches to antiviral protection that offer the possibility of universal protection against epidemic and pandemic influenza.

Incorporation of membrane-bound, mammalian-derived immunomodulatory proteins into influenza whole virus vaccines boosts immunogenicity and protection against lethal challenge

Background

Influenza epidemics continue to cause morbidity and mortality within the human population despite widespread vaccination efforts. This, along with the ominous threat of an avian influenza pandemic (H5N1), demonstrates the need for a much improved, more sophisticated influenza vaccine. We have developed an in vitro model system for producing a membrane-bound Cytokine-bearing Influenza Vaccine (CYT-IVAC). Numerous cytokines are involved in directing both innate and adaptive immunity and it is our goal to utilize the properties of individual cytokines and other immunomodulatory proteins to create a more immunogenic vaccine.

Results

We have evaluated the immunogenicity of inactivated cytokine-bearing influenza vaccines using a mouse model of lethal influenza virus challenge. CYT-IVACs were produced by stably transfecting MDCK cell lines with mouse-derived cytokines (GM-CSF, IL-2 and IL-4) fused to the membrane-anchoring domain of the viral hemagglutinin. Influenza virus replication in these cell lines resulted in the uptake of the bioactive membrane-bound cytokines during virus budding and release. In vivo efficacy studies revealed that a single low dose of IL-2 or IL-4-bearing CYT-IVAC is superior at providing protection against lethal influenza challenge in a mouse model and provides a more balanced Th₁/Th₂ humoral immune response, similar to live virus infections.

Conclusion

We have validated the protective efficacy of CYT-IVACs in a mammalian model of influenza virus infection. This technology has broad applications in current influenza virus vaccine development and may prove particularly useful in boosting immune responses in the elderly, where current vaccines are minimally effective.

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.

Generation of an influenza A virus vector expressing biologically active human interleukin-2 from the NS gene segment

Engineering of the influenza A virus NS1 protein became an attractive approach to the development of influenza vaccine vectors since it can tolerate large inserts of foreign proteins. However, influenza virus vectors expressing long foreign sequences from the NS1 open reading frame (ORF) are usually replication deficient in animals due to the abrogation of their NS1 protein function. In this study, we describe a bicistronic expression strategy based on the insertion of an overlapping UAAUG stop-start codon cassette into the NS gene, allowing the reinitiation of translation of a foreign sequence. Although the expression level of green fluorescent protein (GFP) from the newly created reading frame was significantly lower than that obtained previously from an influenza virus vector expressing GFP from the NS1 ORF, the bicistronic vector appeared to be replication competent in mice and showed outstanding genetic stability. All viral isolates derived from mouse lungs at 10 days postinfection were still capable of expressing GFP in infected cells. Utilizing this bicistronic approach, we constructed another recombinant influenza virus, allowing the secretion of biologically active human interleukin-2 (IL-2). Although this virus also replicated to high titers in mouse lungs, it did not display any mortality rate in infected animals, in contrast to control viruses. Moreover, the IL-2-expressing virus showed an enhanced CD8+ response to viral antigens in mice after a single intranasal immunization. These results indicate that influenza viruses could be engineered for the expression of biologically active molecules such as cytokines for immune modulation purposes.

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Fusion of interleukin-2 to subunit antigens increase their antigenicity in vitro due to an interleukin-2 receptor beta-mediated antigen uptake mechanism

Subunit vaccines, based on one or more epitopes, offer advantages over whole vaccines in terms of safety but are less antigenic. We investigated whether fusion of the cytokine interleukin-2 (IL-2) to influenza-derived subunit antigens could increase their antigenicity. The fusion of IL-2 to the subunit antigens increased their antigenicity in vitro. Encapsulation of the subunit antigen in liposomes also increased its antigenicity in vitro, yet encapsulation of the subunit IL-2 fusion did not. The use of anti-IL-2 receptor beta (IL-2Rbeta) antibody to block the receptor subunit on macrophages suggested that the adjuvancy exerted by IL-2 in our in vitro system is due to, at least in part, a previously unreported IL-2Rbeta-mediated antigen uptake mechanism.

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.

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.

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.

A novel liposomal influenza vaccine (INFLUSOME-VAC) containing hemagglutinin-neuraminidase and IL-2 or GM-CSF induces protective anti-neuraminidase antibodies cross-reacting with a wide spectrum of influenza A viral strains

A liposomal influenza vaccine (INFLUSOME-VAC) was developed with the objective of overcoming the major drawbacks of the currently used influenza vaccines: their relatively low efficacy in certain high-risk groups (the elderly, infants, the immunosuppressed) and the need for annual immunization. INFLUSOME-VAC consists of liposomes containing the viral surface proteins hemagglutinin (HA) and neuraminidase (NA) derived from various influenza strains and IL-2 or GM-CSF, as an adjuvant. Vaccination of mice showed that, whereas conventional vaccines induced a low- and short-term response against HA and very low or no anti-NA response, INFLUSOME-VAC produced high titers of both anti-HA and anti-NA antibodies (Abs) in young and old mice that persisted for at least 6 months. Moreover, the anti-NA Abs efficiently cross-reacted with several N2 viral subtypes spanning 20 years, and such vaccines afforded partial protection against heterosubtypic viral infection.

Cytokine adjuvancy of BVDV DNA vaccine enhances both humoral and cellular immune responses in mice

The effect of cytokine adjuvancy on a bovine viral diarrhoea virus (BVDV) DNA vaccine expressing the major glycoprotein E2 was investigated in mice. Murine interleukin-2 (IL-2) and granulocyte-macrophage colony-stimulating factor (GM-CSF) were chosen for their potential ability to enhance the humoral and cellular immune responses involved in protection against BVDV. Both cytokines, co-administered as separate plasmid constructs, had a marked effect on ELISA and neutralising antibody titres, improving the spectrum of neutralisation induced by the E2 DNA vaccine, as demonstrated in heterologous neutralisation assays. The predominance of IgG2a isotypes, in sera from all DNA injected groups, indicated a Th1 biased immune response. Antigen specific proliferation of murine splenocytes from immunised mice was enhanced by cytokine co-administration, with the highest stimulation indexes observed in the group co-injected with the GM-CSF construct. These results obtained in the mouse (Balb/c; H2-kd) animal model demonstrate the value of the two cytokines as adjuvants for the E2 DNA vaccine. The need for an adjuvant in this system was emphasised by the MHC restriction observed when C57BL/6 mice (H2-kb) were immunised with the E2 DNA construct. Antibody levels were dramatically lower in this mouse strain.

Immunoadjuvant activity of interferon-gamma-liposomes co-administered with influenza vaccines

In an attempt to potentiate the relatively low immunogenicity of the currently used influenza vaccines, especially in high-risk groups, monovalent and divalent subunit vaccine preparations were co-administered with free or liposome-associated murine interferon gamma (mIFNgamma) as an adjuvant. Recombinant murine IFNgamma was entrapped (50-70% efficiency) in two types of large multilamellar vesicles: mIFNgamma-LIP A-'conventional' liposomes, and mIFNgamma-LIP B- 'surface-depleted' liposomes, in which 60 and 8% of the associated cytokine was located at the external liposome membrane, respectively. Subunit preparations containing the viral surface proteins hemagglutinin and neuraminidase (HN) were injected once, i.p. (0.5 microg each), into BALB/c mice, alone and combined with free or liposomal mIFNgamma (mIFNgamma-LIP, 0.5 or 3.0 microg). Sera were tested 3-16 weeks post-vaccination by hemagglutination inhibition (HI), and by ELISA for IgG1 and IgG2a antibodies (Abs). In addition, protective immunity against intranasal viral infection was assayed at 11 and 17 weeks post-vaccination. The results showed that: (a) Vaccination with HN alone produces very low HI and IgG titers and does not afford any protection. (b) Although co-administration with free mIFNgamma (particularly using 3.0 microg) markedly enhances HI titer as well as the IgG1 and IgG2a levels, protection is negligible (0-33%). (c) In most cases, mIFNgamma-LIP is significantly more potent than free mIFNgamma (2-40-fold increase in Ab titer), and the low dose (0.5 microg) is generally more efficient than the high dose. Up to 83% of the mice co-vaccinated with mIFNgamma-LIP were protected against viral challenge. (d) Both the IgG2a level and the HI titer appear to be crucial for protection. (e) Although the two liposomal preparations differ in their cytokine release profile in vivo and in their bioactivity in vitro, their adjuvant activity is comparable.

The effects of histamine on interferon gamma production are dependent on the stimulatory signals

Histamine regulates the immune response by enhancing TH2 cytokine production and by inhibiting TH1 cytokine production. We assessed the mechanisms of histamine's action on helper T cell subsets by evaluating the role of protein kinase A (PKA) in the histamine-mediated effects on IFN gamma production. The splenocytes and TH1 murine cloned cells (pGL10) were pretreated with histamine at a concentration range of 10(-8)-10(-5) M for 1 h and then were activated with anti-CD3, PHA, PMA + ionomycin, or ionomycin for 24 h. The levels of IFN gamma were measured in the supernatants by ELISA. The inhibitory effects of histamine were the most prominent in anti-CD3-stimulated splenocytes (61%). The effects of histamine on IFN gamma production from TH1 cells depended on the mode of cell activation. The activation of cells with anti-CD3 resulted in 27% inhibition of IFN gamma production whereas the activation with ionomycin produced 70% suppression. The inhibitory effects of histamine were completely reversed by cimetidine in a dose-dependent manner in both TH1 cells and in splenocytes. PKA played a role in the inhibition of IFN gamma by histamine when the cells were activated via TCR, and the PKA inhibitors Rp-cAMPS (10(-5) M) and H8 (10(-5) M) reversed the inhibitory effects of histamine on IFN gamma production. However, when the cells were stimulated with ionomycin, the PKA inhibitors did not affect histamine-mediated suppression of IFN gamma production.

Targeting early events in T cell activation to construct improved vaccines

Live, attenuated vaccines currently offer the best protection against virulent pathogens. Recent advances in Immunology and Molecular Biology provide an opportunity to design vaccines that will be more effective and safer than existing ones. Immunologists are rapidly developing the capacity to identify and construct the minimal immunogenic units from pathogens. The molecular signals required to fully activate antigen presenting cells (APCs) and responder T cells are becoming apparent. Improved vaccine delivery systems are being designed which will mimic the actions of pathogens in vivo. These vaccines will incorporate protective epitopes fused to immunoregulatory cytokines in chimeric proteins. They will be encapsulated in formulations which allow for the slow release of these chimeric proteins thereby inducing the memory T cells required for long-lived immunity. These vaccine formulations will target receptors present on the most active APCs. Here we discuss how these advances will allow us to rationally construct "virtual pathogens" which will provide improved protection against new and old microbial foes.

Uses of granulocyte-macrophage colony-stimulating factor in vaccine development

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a potent cytokine capable of inducing differentiation, proliferation, and activation of a variety of immunologically active cell populations. In addition to its effects on stimulating granulocytic hematopoiesis, it also facilitates development of both humoral and cellular mediated immunity. Accordingly, strategies involving the use of GM-CSF as a vaccine adjuvant have attracted considerable attention. These strategies include the systemic administration of soluble GM-CSF with an immunogen, and also its use as part of gene therapy approaches to immunization. Because of the potency of this cytokine as an immune adjuvant, particular interest has focused on its use to overcome poorly immunogenic antigens such as those associated with intracellular infections and cancer. This review focuses on recent advances in the use of GM-CSF as a vaccine adjuvant.