The immune response of humans to live and inactivated influenza vaccines

Comparative Safety and Efficacy Profile of a Novel Oil in Water Vaccine Adjuvant Comprising Vitamins A and E and a Catechin in Protective Anti-Influenza Immunity

Non-replicating vaccines, such as those based on recombinant proteins, require adjuvants and delivery systems, which have thus far depended on mimicking pathogen danger signals and strong pro-inflammatory responses. In search of a safer and more efficacious alternative, we tested whether vaccinations with influenza recombinant hemagglutinin (HA) mixed with a novel vegetable oil in water emulsion adjuvant (Natural Immune-enhancing Delivery System, NIDS), based on the immune-enhancing synergy of vitamins A and E and a catechin, could protect against intra-nasal challenge with live influenza virus. Vaccinations of inbred Brag Albino strain c (BALB/c) mice, with HA mixed with NIDS compared to other adjuvants, i.e., a squalene oil in water emulsion (Sq. oil), and the Toll Like Receptor 3 (TLR3) agonist Poly (I:C), induced significantly lower select innate pro-inflammatory responses in serum, but induced significantly higher adaptive antibody and splenic T Helper 1 (TH1) or TH2, but not TH17, responses. Vaccinations with NIDS protected against infection, as measured by clinical scores, lung viral loads, and serum hemagglutination inhibition titers. The NIDS exhibited a strong dose sparing effect and the adjuvant action of NIDS was intact in the outbred CD1 mice. Importantly, vaccinations with the Sq. oil, but not NIDS, induced a significantly higher Serum Amyloid P component, an acute phase reactant secreted by hepatocytes, and total serum IgE. Thus, the NIDS may be used as a clinically safer and more efficacious vaccine adjuvant against influenza, and potentially other infectious diseases.

Systemic and Mucosal Antibody Responses to Soluble and Nanoparticle-Conjugated Antigens Administered Intranasally

Nanoparticles (NPs) are increasingly being used for drug delivery, as well as antigen carriers and immunostimulants for the purpose of developing vaccines. In this work, we examined how intranasal (i.n.) priming followed by i.n. or subcutaneous (s.c.) boosting immunization affects the humoral immune response to chicken ovalbumin (Ova) and Ova conjugated to 20 nm NPs (NP-Ova). We show that i.n. priming with 20 mg of soluble Ova, a dose known to trigger oral tolerance when administered via gastric gavage, induced substantial systemic IgG1 and IgG2c, as well as mucosal antibodies. These responses were further boosted following a s.c. immunization with Ova and complete Freund’s adjuvant (Ova+CFA). In contrast, 100 µg of Ova delivered via NPs induced an IgG1-dominated systemic response, and primed the intestinal mucosa for secretion of IgA. Following a secondary s.c. or i.n. immunization with Ova+CFA or NP-Ova, systemic IgG1 titers significantly increased, and serum IgG2c and intestinal antibodies were induced in mice primed nasally with NP-Ova. Only Ova- and NP-Ova-primed mice that were s.c.-boosted exhibited substantial systemic and mucosal titers for up to 6 months after priming, whereas the antibodies of i.n.-boosted mice declined over time. Our results indicate that although the amount of Ova delivered by NPs was 1000-fold less than Ova delivered in soluble form, the antigen-specific antibody responses, both systemic and mucosal, are essentially identical by 6 months following the initial priming immunization. Additionally, both i.n.- and s.c.-boosting strategies for NP-Ova-primed mice were capable of inducing a polarized Th1/Th2 immune response, as well as intestinal antibodies; however, it is only by using a heterogeneous prime-boost strategy that long-lasting antibody responses were initiated. These results provide valuable insight for future mucosal vaccine development, as well as furthering our understanding of mucosal antibody responses.

Cross-protective immunity against multiple influenza virus subtypes by a novel modified vaccinia Ankara (MVA) vectored vaccine in mice

Development of an influenza vaccine that provides cross-protective immunity remains a challenge. Candidate vaccines based on a recombinant modified vaccinia Ankara (MVA) viral vector expressing antigens from influenza (MVA/Flu) viruses were constructed. A vaccine candidate, designated MVA/HA1/C13L/NP, that expresses the hemagglutinin from pandemic H1N1 (A/California/04/09) and the nucleoprotein (NP) from highly pathogenic H5N1 (A/Vietnam/1203/04) fused to a secretory signal sequence from vaccinia virus was highly protective. The vaccine elicited strong antibody titers to homologous H1N1 viruses while cross-reactive antibodies to heterologous viruses were not detectable. In mice, this MVA/HA1/C13L/NP vaccine conferred complete protection against lethal challenge with A/Vietnam/1203/04 (H5N1), A/Norway/3487-2/09 (pandemic H1N1) or A/Influenza/Puerto Rico/8/34 (seasonal H1N1) and partial protection (57.1%) against challenge with seasonal H3N2 virus (A/Aichi/68). The protective efficacy of the vaccine was not affected by pre-existing immunity to vaccinia. Our findings highlight MVA as suitable vector to express multiple influenza antigens that could afford broad cross-protective immunity against multiple subtypes of influenza virus.

Nanoemulsion W805EC improves immune responses upon intranasal delivery of an inactivated pandemic H1N1 influenza vaccine

Currently available influenza vaccines provide suboptimal protection. In order to improve the quality of protective immune responses elicited following vaccination, we developed an oil-in-water nanoemulsion (NE)-based adjuvant for an intranasally-delivered inactivated influenza vaccine. Using a prime-boost vaccination regimen, we show that intranasal vaccines containing the W(80)5EC NE elicited higher titers of serum hemagglutination inhibiting (HAI) antibody and influenza-specific IgG and IgA titers compared to vaccines that did not contain the NE. Similarly, vaccines containing the W(80)5EC NE resulted in higher influenza-specific IgA levels in the bronchoalveolar lavage (BAL) fluid and nasal wash when compared to vaccines formulated without NE. The higher antibody titers in mice immunized with the NE-containing vaccines correlated with reduced viral loads in the lungs and nasal turbinates following a high dose viral challenge. Mice immunized with vaccines containing the W(80)5EC NE also showed a reduction in body weight loss following challenge compared to mice immunized with equivalent vaccines produced without NE. Taken together, our results show that the W(80)5EC NE substantially improves the magnitude of protective influenza-specific antibody responses and is a promising mucosal adjuvant for influenza vaccines and vaccines against other mucosal pathogens.

Prolonged protection against Intranasal challenge with influenza virus following systemic immunization or combinations of mucosal and systemic immunizations with a heat-labile toxin mutant

Seasonal influenza virus infections cause considerable morbidity and mortality in the world, and there is a serious threat of a pandemic influenza with the potential to cause millions of deaths. Therefore, practical influenza vaccines and vaccination strategies that can confer protection against intranasal infection with influenza viruses are needed. In this study, we demonstrate that using LTK63, a nontoxic mutant of the heat-labile toxin from Escherichia coli, as an adjuvant for both mucosal and systemic immunizations, systemic (intramuscular) immunization or combinations of mucosal (intranasal) and intramuscular immunizations protected mice against intranasal challenge with a lethal dose of live influenza virus at 3.5 months after the second immunization.

A vaccination strategy to enhance mucosal and systemic antibody and T cell responses against influenza

Influenza infections are a major cause of mortality and morbidity worldwide. Therefore, there is a need to establish vaccines and immunization protocols that can prevent influenza infections. Herein, we show that one intranasal (IN) followed by one intramuscular (IM) immunizations with a combination of cell culture produced hemagglutinin (HA) antigens derived from 3 different influenza strains induced significantly higher serum hemagglutination inhibition (HI) and serum IgG antibody titers as well as T cell responses, compared to 2 IM, 2 IN or 1 M followed by 1 IN immunizations. Moreover, while 2 IM immunizations did not induce any antibody responses in nasal secretions or cervical lymph nodes, which drain the nasal mucosa, IN immunizations alone or in combination with IM immunization induced mucosal and local responses. These data show that the IN followed by IM immunization strategy holds promise to significantly raise serum and local antibody and T cell responses against seasonal influenza strains, and possibly pandemic influenza strains, for which no pre-existing immunity exists.

Development of immune response that protects mice from viral pneumonitis after a single intranasal immunization with influenza A virus and nanoemulsion

Nanoemulsion, a water-in-oil formulation stabilized by small amounts of surfactant, is non-toxic to mucous membranes and produces biocidal activity against enveloped viruses. We evaluated nanoemulsion as an adjuvant for mucosal influenza vaccines. Mice (C3H/HeNHsd strain) were vaccinated intranasally with 5 x 10(5) plaque forming units (pfu) of influenza A virus (Ann Arbor/6/60 strain) and a nanoemulsion mixture. The mice were challenged on day 21 after immunization with an intranasal lethal dose of 2 x 10(5) pfu of virus. Animals vaccinated with the influenza A/nanoemulsion mixture were completely protected against infection, while animals vaccinated with either formaldehyde-killed virus or nanoemulsion alone developed viral pneumonitis and died by day 6 after the challenge. Mice vaccinated with virus/nanoemulsion mixture had rapid cytokine responses followed by high levels of specific anti-influenza immunoglobulin G (IgG) and immunoglobulin A (IgA) antibodies. Specificity of the immune response was confirmed by assessment of the proliferation and cytokine production in splenocytes. This paper demonstrates that nanoemulsion can be employed as a non-toxic mucosal adjuvant for influenza virus vaccine.

Role of systemic and mucosal immune responses in reciprocal protection against Bordetella pertussis and Bordetella parapertussis in a murine model of respiratory infection

The roles of systemic humoral immunity, cell-mediated immunity, and mucosal immunity in reciprocal protective immunity against Bordetella pertussis and Bordetella parapertussis were examined by using a murine model of respiratory infection. Passive immunization with serum from mice infected with B. pertussis established protective immunity against B. pertussis but not against B. parapertussis. Protection against B. parapertussis was induced in mice that had been injected with serum from mice infected with B. parapertussis but not from mice infected with B. pertussis. Adoptive transfer of spleen cells from mice infected with B. pertussis or B. parapertussis also failed to confer reciprocal protection. To examine the role of mucosal immunity in reciprocal protection, mice were infected with preparations of either B. pertussis or B. parapertussis, each of which had been incubated with the bronchoalveolar wash of mice that were convalescing after infection with B. pertussis or B. parapertussis. Such incubation conferred reciprocal protection against B. pertussis and B. parapertussis on infected mice. The data suggest that mucosal immunity including secreted immunoglobulin A in the lungs might play an important role in reciprocal protective immunity in this murine model of respiratory infection.

Immune responses and protection in different strains of aged mice immunized intranasally with an adjuvant-combined influenza vaccine

Immune responses and protection against influenza virus infection were compared between young (2 months) and aged (18 months) BALB/c, C3H and C57BL/6 (B6) mice after intranasal vaccination. The mice were immunized with 2.5 microg protein of A/PR/8/34 (PR8) (H1N1) virus vaccine containing a cholera toxin adjuvant. In both the young and aged BALB/c mice, high levels of PR8-specific antibody-forming cell (AFC) responses were induced in the nasal-associated lymphoid tissue (NALT) 7 days after immunization. Nasal wash IgA and serum IgG antibody (Ab) responses to the PR8 haemagglutinin (HA) 4 weeks after immunization were slightly higher in the young mice than in the aged mice. The young mice showed complete protection against challenge infection, while the aged mice showed only a partial protection. In the C3H mice, NALT-AFC, and IgA and IgG Ab responses were higher in the young mice than those in the aged mice in parallel with the more efficient protection in the young mice than in the aged mice. Both the young and aged B6 mice showed no NALT-AFC responses, scarce IgA and IgG Ab responses and no protection. In the BALB/c mice, IgG1 and IgG2a levels were significantly lower in the aged mice. On the other hand, in the C3H mice, only IgG2a level was significantly lower in the aged mice. Similar results were obtained in terms of immune responses and protection between the young and aged mice of three different strains of mice after intra-nasal immunization with 0.1 microg of PR8 vaccine containing the adjuvant, two-times at 4-week intervals. In the B6 mice, the immune response was improved by immunization with a higher dose of the adjuvant-combined vaccine. These results suggest that local Ab responses, as well as systemic Ab responses, are downregulated in aged mice, although the degree of the downregulation of immune responses differs from strain to strain.

Oral administration of influenza vaccine in combination with the adjuvants LT-K63 and LT-R72 induces potent immune responses comparable to or stronger than traditional intramuscular immunization

Mucosal immunization strategies are actively being pursued in the hopes of improving the efficacy of vaccines against the influenza virus. Our group investigated the oral immunization of mice via intragastric gavage with influenza hemagglutinin (HA) combined with mutant Escherichia coli heat-labile enterotoxins K63 (LT-K63) and R72 (LT-R72). These oral immunizations resulted in potent serum antibody and HA inhibition titers, in some cases stronger than those obtained with traditional intramuscular administration, in addition to HA-specific immunoglobulin A in the saliva and nasal secretions. This study demonstrates that it may be possible to develop effective oral influenza vaccines.

A novel bioadhesive intranasal delivery system for inactivated influenza vaccines

The aim of the current studies was to evaluate a bioadhesive delivery system for intranasal administration of a flu vaccine, in combination with a mucosal adjuvant (LTK63). A commercially available influenza vaccine, containing hemagglutinin (HA) from influenza/A Johannesberg H1N1 1996, and LTK63 or LTR72 adjuvants, which are genetically detoxified derivatives of heat labile enterotoxin from Escherichia coli, were administered IN in a bioadhesive delivery system, which comprised esterified hyaluronic acid (HYAFF) microspheres, to mice, rabbits and micro-pigs at days 0 and 28. For comparison, additional groups of animals were immunized intranasally with the HA vaccine alone, with soluble HA+LTK63, or IM with HA. In all three species, the groups of animals receiving IN immunization with the bioadhesive microsphere formulations, including LT mutants, showed significantly enhanced serum IgG responses (P<0.05) and higher hemagglutination inhibition (HI) titers in comparison to the other groups. In addition, the bioadhesive formulation also showed a significantly enhanced nasal wash IgA response (P<0.05). Most encouragingly, in pigs, the bioadhesive microsphere vaccine delivery system induced serum immune responses following IN immunization, which were significantly more potent than those induced by traditional IM immunization at the same vaccine dose (P<0.05).

Intranasal immunization of mice with influenza vaccine in combination with the adjuvant LT-R72 induces potent mucosal and serum immunity which is stronger than that with traditional intramuscular immunization

Immunization of mice by the intranasal route with influenza virus hemagglutinin in combination with the mutant Escherichia coli heat-labile enterotoxin R72 (LT-R72) induced significantly enhanced serum and mucosal antibodies, surpassing, in most cases, responses achieved by traditional intramuscular immunization using inactivated split influenza vaccine. Furthermore, intranasal immunization with LT-R72 induced a potent serum immunoglobulin G2a response, indicating that this adjuvant has Th1 character.

Oral immunization with a replication-deficient recombinant vaccinia virus protects mice against influenza

Mice immunized with two intragastrically administered doses of a replication-deficient recombinant vaccinia virus containing the hemagglutinin and nucleoprotein genes from H1N1 influenza virus developed serum anti-H1 immunoglobulin G (IgG) antibody that completely protected the lungs from challenge with H1N1. Almost all of the mice given two intragastric doses also developed mucosal anti-H1 IgA antibody, and those with high anti-H1 IgA titers had completely protected noses. Intramuscular injection of the vaccine protected the lungs but not the noses from challenge. We also found that the vaccine enhanced recovery from infection caused by a shifted (H3N2) influenza virus, probably through the induction of nucleoprotein-specific cytotoxic T-lymphocyte activity. A replication-deficient, orally administered, enteric-coated, vaccinia virus-vectored vaccine might safely protect humans against influenza.

Developments in mucosal influenza virus vaccines

Immunogenicity and efficacy of aerosol inactivated split influenza virus vaccines, which are threefold the strength of the vaccines for parenteral use, and cold-adapted reassortant live influenza virus vaccines were evaluated. Mucosal immune responses were evaluated by quantifying specific IgA antibody of the nasal swab solution, and systemic immune responses were evaluated by determining serum haemagglutination inhibition antibody levels. Efficacy of the aerosol inactivated vaccine was evaluated by a challenge test using live vaccine virus. It was concluded that mucosally administered inactivated influenza virus vaccine stimulated systemic and mucosal immune responses more strongly than live influenza virus vaccine and manifested a much stronger booster effect than live vaccine. Mucosal administration of inactivated influenza virus vaccine was effective in preventing infection by live vaccine virus.

Local and systemic influenza haemagglutinin-specific antibody responses following aerosol and subcutaneous administration of inactivated split influenza vaccine

An easily administered and safe vaccine is required to produce the herd immunity necessary to control influenza epidemics worldwide. A commercial quadrivalent inactivated split influenza vaccine was administered intranasally in aerosol form to a group of 46 volunteers; other groups were given the same vaccine subcutaneously and saline intranasally. The results show that mucosal stimulation via intranasal vaccination resulted in a marked increase in local HA-specific IgA antibodies, and that this stimulation was necessary for serum HA-specific IgA responses. Serum HA-specific IgA antibody levels can be used as indicators of local antigenic stimulation, providing a method for evaluating potency and antigenicity in humans of intranasal influenza vaccine. This vaccination route shows much promise for the future.