Serum and mucosal immunologic responses in children following the administration of a new inactivated intranasal anti-influenza vaccine

Cross-reactivity of immunoglobulin A secreted on the nasal mucosa in mice nasally inoculated with inactivated H1N1 influenza A viruses in the presence of D-octaarginine-linked polymers

We evaluated cross-reactivity of immunoglobulin A (IgA) secreted on the nasal mucosa in mice that were nasally inoculated 4 times with a mixture of inactivated H1N1 influenza A viruses and poly(N-vinylacetamide-co-acrylic acid) (PNVA-co-AA) bearing d-octaarginine at 7-day intervals. Three viral strains (A/Puerto Rico/8/34, A/New Caledonia/20/99 IVR116, and A/Solomon Islands/03/2006) and D-octaarginine-linked polymers with different molecular weights were used as antigens and their carriers, respectively. Secretion of intranasal IgA was barely observed when the inactivated virus alone was administered. The polymer induced the production of intranasal IgA specific to the inoculated viruses, irrespective of the viral strain and molecular weight of the polymer. The respective antibodies cross-reacted to recombinant hemagglutinin proteins of not only the viral strain used for immunization but also other H1N1 strains, including A/Puerto Rico/8/34 strain whose hemagglutinin proteins are diverse from those of other strains. Mice with high reactivity of IgA to the inoculated viruses tended to acquire clear cross-reactivity to other viral strains. Notably, IgA induced by inactivated H1N1 A/New Caledonia/20/99 IVR116 strain with the strongest immunogenicity between 3 antigens in the presence of the polymer cross-reacted to recombinant hemagglutinin proteins of the A/Brisbane/10/2007 and A/Viet Nam/1194/2004 strains, which are categorized into H3N2 and H5N1, respectively. Our polymer is a potential candidate for an efficient antigen carrier that induces mucosal IgA having cross-reactivity to antigenically drifted variants, irrespective of the subtype of viral strains.

Cell-penetrating peptide-linked polymers as carriers for mucosal vaccine delivery

We evaluated the potential of poly(N-vinylacetamide-co-acrylic acid) modified with d-octaarginine, which is a typical cell-penetrating peptide, as a carrier for mucosal vaccine delivery. Mice were nasally inoculated four times every seventh day with PBS containing ovalbumin with or without the d-octaarginine-linked polymer. The polymer enhanced the production of ovalbumin-specific immunoglobulin G (IgG) and secreted immunoglobulin A (IgA) in the serum and the nasal cavity, respectively. Ovalbumin internalized into nasal epithelial cells appeared to stimulate IgA production. Ovalbumin transferred to systemic circulation possibly enhanced IgG production. An equivalent dose of the cholera toxin B subunit (CTB), which was used as a positive control, was superior to the polymer in enhancing antibody production; however, dose escalation of the polymer overcame this disadvantage. A similar immunization profile was also observed when ovalbumin was replaced with influenza virus HA vaccines. The polymer induced a vaccine-specific immune response identical to that induced by CTB, irrespective of the antibody type, when its dose was 10 times that of CTB. Our cell-penetrating peptide-linked polymer is a potential candidate for antigen carriers that induce humoral immunity on the mucosal surface and in systemic circulation when nasally coadministered with antigens.

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.

Contrasting effects of type I interferon as a mucosal adjuvant for influenza vaccine in mice and humans

To identify an adjuvant that enhances antibody responses in respiratory secretions to inactivated influenza virus vaccine (IVV), a comparison was made of responses to intranasal vaccinations of mice with IVV containing monophosphoryl lipid A (MPL), type I interferon (IFN) or cholera toxin B (CTB). Antibody in nasal secretions and lung wash fluids from mice was increased after vaccination and lung virus was significantly reduced after challenge to a similar level in each adjuvant group. Interferon was selected for a trial in humans. Trivalent inactivated influenza vaccine was given intranasally to healthy adult volunteers alone or with 1 million units (Mu) or 10 Mu of alpha interferon. Vaccinations were well tolerated but neither serum hemagglutination-inhibiting nor neutralizing antibody responses among the vaccine groups were significantly different. Similarly, neither neutralizing nor IgA antibody responses in nasal secretions were significantly different. Thus, despite exhibiting a significant adjuvant effect in mice, interferon did not exhibit an adjuvant effect for induction of antibody in respiratory secretions of humans to inactivated influenza virus vaccine given intranasally.

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.

Modified Pulmonary Surfactant Is a Potent Adjuvant That Stimulates the Mucosal IgA Production in Response to the Influenza Virus Antigen

The intranasal administration of influenza hemagglutinin (HA) vaccine with Surfacten, a modified pulmonary surfactant free of antigenic c-type lectins, as a mucosal adjuvant induced the highest protective mucosal immunity in the airway. The intranasal immunization of mice with HA vaccine (0.2 microg)-Surfacten (0.2 microg) selectively induced the neutralizing anti-HA IgA, but not IgG, and conferred nearly maximal protection in the airway, without inducing a systemic response. In contrast, intranasal inoculation of vaccine with 0.2 microg of the potent mucosal adjuvant cholera toxin B* (CT-B*), prepared by adding 0.2% native CT to the B subunit of CT, induced both anti-HA IgA and IgG in the airway and in the serum. The intranasal administration of HA vaccine alone induced a limited amount of mucosal IgA against influenza virus. Although the s.c. administration of HA vaccine prominently induced serum IgG and IgA, Surfacten and CT-B* did not enhance their induction, and the concentrations of Abs leaking into the airways were insufficient to prevent viral multiplication. The intranasal administration of HA-Surfacten stimulated the expression of MHC class II, CD40, and CD86 molecules in the CD11c-positive cells isolated from the nasal mucosa, but not the expression of cells from the lungs or spleens. Lymphocytes isolated from the airway mucosa after intranasal HA-Surfacten immunization prominently induced TGF-beta1 which, compared with inoculation without Surfacten, promoted an Ag-specific mucosal IgA response. Surfacten alone, however, did not induce TGF-beta1. Our observations suggest that Surfacten, by mimicking the natural surfactant, is an effective mucosal adjuvant in the process of airway immunization.

Immune response after adjuvant mucosal immunization of mice with inactivated influenza virus

Satisfactory mucosal immunity in the respiratory tract is very important for protection against influenza. It can be achieved only by mucosal immunization. Mucosal vaccination with inactivated influenza virus may not be sufficiently effective and suitable adjuvants are therefore sought. We tested intratracheal immunization of mice with inactivate B type influenza virus in a mixture with formolized G+ bacterium Bacillus firmus, whose adjuvant effects have previously been documented in another system. The treatment resulted in a marked increase of both systemic and mucosal antibody response in IgG and IgA classes. Stimulation of T lymphocytes after adjuvant immunization was very mild, no proliferation taking place after specific stimulation with antigen in vitro. However, slightly increased systemic (spleen) and local (lungs) production of cytokines without perceptible Th1/Th2 polarization was determined. B. firmus is an efficient adjuvant in respiratory tract immunization while with subcutaneous immunization it lowers the antibody response.

Mucosal (SIgA) and serum (IgG) immunologic responses in young adults following intranasal administration of one or two doses of inactivated, trivalent anti-influenza vaccine

Influenza morbidity affects the entire population and has an enormous impact upon the economic burden and the health care systems. Available vaccines are often unsatisfactory and many individuals are reluctant to receive injections. Intranasal immunization is painless, side effect free and may encourage a large number of individuals to participate in the vaccination programs. Ninety-two students were immunized intranasally once or twice, 21 days apart, with a trivalent inactivated whole influenza vaccine during three separate seasons (1996/1997, 1997/1998 and 1998/1999) with the recommended seasonal strains. The vaccine was well tolerated, without adverse effect and morbidity in the vaccinees during the winter season was low. Serum antibody response was determined by the hemagglutination inhibition (HI) test and nasal response by the enzyme-linked immunoadsorbant assay (ELISA). Following the second dose, mucosal antibody response was detected in 48.1-73.3% of immunized subjects. Serum and mucosal antibody levels (GMT) increased significantly to all the strains, with the exception of A/H3N2 in the mucosal response in 1997/1998. At the end of the trial, the percentage of immune subjects was over 93% to A/H1N1 strains, 60-71% to A/H3N2 and 64-66% to B/Harbin in 1996/1997 and 1997/1998, and 75-91% following one dose in 1998/1999. When serum and mucosal responses were combined, a higher percentage of responders was found (60-86%). Repeated vaccination does not seem to interfere with serum or mucosal response. The double barrier of mucosal and serum antibody may inhibit infection and decrease morbidity when infection occurs, thus limiting the spread of influenza in the community.

Effectiveness of influenza vaccination of children with recurrent respiratory tract infections in reducing respiratory-related morbidity within the households

To evaluate the effectiveness of influenza vaccination in reducing respiratory-related morbidity among children with recurrent respiratory tract infections (RRTIs) and their household contacts, 127 children aged 6 months-9 years (78 males; median age, 3.7 years) with a history of RRTIs (>/=6 episodes per year if aged >/=3 years; >/=8 episodes per year if aged <3 years) were randomized to receive the intranasal virosomal influenza vaccine (n=64 with 176 household contacts) or a control placebo (n=63 with 173 household contacts). During influenza season, the vaccinated children had fewer respiratory infections, febrile respiratory illnesses, prescribed antibiotics and antipyretics, and missed school days than the controls, and similar benefits and a reduction in the loss of parental work were observed among their household contacts. This study shows that the benefits of influenza vaccination extend to children with RRTIs and their family members and encourages to recommend its use in such children.

Evaluation of novel aerosol formulations designed for mucosal vaccination against influenza virus

Influenza viruses are among the most significant human pathogens, responsible for increased seasonal morbidity and mortality particularly in immunodepressed and chronically ill. Conventional vaccination with non-replicative vaccine is currently performed by injection. In the present study, we explore simple spray-dried lipid formulations containing whole inactivated virus or split-subunit vaccine that allow aerosolization and thus, mucosal vaccination of the pulmonary tract. We show that by using biocompatible excipients already approved for human use, one could engineer microparticles that induce substantial local and systemic immunity subsequent to pulmonary administration. Exposure of the bronchial-associated lymphoid tissue (BALT) to vaccine was more effective than parenteral or nasal administration in triggering specific immunity. Co-formulation of a biocompatible surfactant detergent greatly ameliorated the immune profile of microparticles containing a whole inactivated virus vaccine. In addition, mere formulation of a licensed split-subunit vaccine significantly enhanced its immunogenicity. Together, our data underline a simple strategy to convert conventional parenteral vaccination of currently available non-replicative vaccines against influenza virus, into one that is more effective and practical upon respiratory administration.

Immunostimulant patch containing heat-labile enterotoxin from Escherichia coli enhances immune responses to injected influenza virus vaccine through activation of skin dendritic cells

Vaccine strategies, such as influenza virus vaccination of the elderly, are highly effective at preventing disease but provide protection for only the responding portion of the vaccinees. Adjuvants improve the magnitude and rates of responses, but their potency must be attenuated to minimize side effects. Topical delivery of strong adjuvants such as heat-labile enterotoxin from Escherichia coli (LT) induces potent immune responses. We hypothesized that LT delivered alone in an immunostimulating (LT-IS) patch placed on the skin at the site of injection could augment the immune response to injected vaccines. This was based on the observation that topically applied LT induces migration of activated antigen-presenting cells (APCs) from the skin to the proximal draining lymph node (DLN), and that APCs loaded with antigen by injection in the same anatomical region also migrate to the same DLN. We observed that when influenza virus vaccine is injected and an LT-IS patch is placed to target the same DLN, the influenza virus antibody response is enhanced. Similarly, influenza virus-specific T cells isolated from the lungs show increased levels of gamma interferon and interleukin-4 production. An LT-IS patch placed near an injected vaccine also leads to increased levels of hemagglutination inhibition titers, enhanced mucosal immunoglobulin A responses, and enhanced antigen presentation. Although the mechanisms by which an LT-IS patch exerts its enhancing effects need further study, the enhanced immune responses, ability to safely use potent adjuvants, and simplicity of LT-IS patch application address an important unmet need and provide a new immune enhancement strategy.

Local and systemic immune response in nursing-home elderly following intranasal or intramuscular immunization with inactivated influenza vaccine

Intramuscular (IM) influenza vaccines are only 30-40% effective in preventing clinical illness among the elderly, and their effectiveness in eliciting mucosal response may be even lower. The aim of the present study was to evaluate the immunological effect of a novel inactivated intranasal (IN) trivalent whole influenza virus vaccine among nursing-home elderly. Twenty-one institutionalized elderly subjects were vaccinated IN with an inactivated novel vaccine, twice, 21 days apart, and with no adverse effects. Twenty-two subjects were vaccinated once with a commercial IM vaccine. Viral strains used in the 1998/9 vaccine (20 microg of each per dose) were A/Beijing/262/95, A/Sydney/5/97 and B/Harbin/7/94. Serum antibodies (IgG and IgM) and nasal IgA were determined by the hemagglutination inhibition (HI) test and enzyme-linked immunosorbent assay (ELISA), respectively. Mucosal antibody response to the three vaccine strains was detected in 47.6-71.4% and 18.1-31.8% of IN and IM immunized subjects, respectively. Serum antibody response to the three antigens tested was detected in 20.0-61.9% and 18.2-72.7% of IN and IM immunized subjects, respectively. Seroconversion was not significantly different after IN or IM vaccination for both A/Sydney and B/Harbin, but higher for A/Beijing following IM vaccination. On study completion, 57.1, 65.0 and 50.0% of IN vaccinees were seroprotected to A/Beijing, A/Sydney and B/Harbin, respectively. Similarly, 68.1, 77.2 and 54.5% were immune after IM vaccination. The IN vaccine tested was significantly more effective than the IM vaccine in inducing mucosal IgA response. This may prevent influenza at its early stages and thus contribute to the reduction of morbidity and complications in nursing-home elderly.

Influenza update: vaccine development and clinical trials

Although influenza activity throughout the world has been relatively low during the past year, epidemics of influenza A, in particular, which are caused by new virus variants, continue to be a major public health problem. Widespread vaccination is the only rational measure that can be used for the prevention of illness in key risk groups. Although current inactivated split/subunit vaccines are reasonably effective, significant improvements have been shown to be possible in the boosting of responses by the use of particular adjuvants and/or the direct administration of vaccines to the respiratory tract. Live attenuated vaccines, also administered directly to the respiratory tract, have continued to be shown to be safe and effective, and, in the longer term, probably will have a major role in influenza prophylaxis, especially in children and 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.