Influenza: vaccination and treatment

Egg microneedles for transdermal vaccination of inactivated influenza virus

The use of dissolving microneedles (DMNs) is a drug delivery technique in which drug dissolution occurs once it is administered into the skin. The skin is a remarkable site for vaccination due to its significant immunologic properties. Compared to the traditional hypodermic intramuscular (IM) injection, vaccination via DMN does not require cold chains and allows for minimal invasive drug delivery. On account of the significance of skin vaccination, preceding studies have been conducted to elucidate the importance of the DMN technology in vaccination. Most of these studies focused on formulations that maintain the activity of the vaccine, so formulations designed to be specific to the mechanical properties of the microneedle could not be used together independently. In this study, we have developed influenza vaccine loaded egg microneedles (EMN) and characterized the specificity of layer-specific functions of EMN by distinguishing between formulations that can maintain the activity of the vaccine and have the mechanical strength. By the use of in vitro tests such as ELISA and SRID assays, we quantitively evaluated the antigen activity of the formulation candidates to be 87% and 91%, respectively. In vivo tests were also conducted as mouse groups were inoculated with the formulation constructed into egg microneedles (FLU-EMN) to determine the protective efficacy against infection. The results demonstrated that FLU-EMN with functionalized formulations successfully enabled protective immune response even with a fractional dose compared to IM injection.

Influenza virus entry and replication inhibited by 8-prenylnaringenin from Citrullus lanatus var. citroides (wild watermelon)

We previously demonstrated the anti-influenza activity of Citrullus lanatus var. citroides (wild watermelon, WWM); however, the active ingredient was unknown. Here, we performed metabolomic analysis to evaluate the ingredients of WWM associated with antiviral activity. Many low-molecular weight compounds were identified, with flavonoids accounting for 35% of all the compounds in WWM juice. Prenylated flavonoids accounted for 30% of the flavonoids. Among the measurable components of phytoestrogens in WWM juice, 8-prenylnaringenin showed the highest antiviral activity. We synthesized 8-prenylnaringenin and used liquid chromatography-mass spectrometry to quantitate the active ingredient in WWM. The antiviral activities of 8-prenylnaringenin were observed against H1N1 and H3N2 influenza A subtypes and influenza B viruses. Moreover, 8-prenylnaringenin was found to inhibit virus adsorption and late-stage virus replication, suggesting that the mechanisms of action of 8-prenylnaringenin may differ from those of amantadine and oseltamivir. We confirmed that 8-prenylnaringenin strongly inhibited the viral entry of all the influenza virus strains that were examined, including those resistant to the anti-influenza drugs oseltamivir and amantadine. This result indicates that 8-prenylnaringenin may activate the host cell's defense mechanisms, rather than directly acting on the influenza virus. Since 8-prenylnaringenin did not inhibit late-stage virus replication of oseltamivir-resistant strains, 8-prenylnaringenin may interact directly with viral neuraminidase. These results are the first report on the anti-influenza virus activity of 8-prenylnaringenin. Our results highlight the potential of WWM and phytoestrogens to develop effective prophylactic and therapeutic approaches to the influenza virus.

Eco-Epidemiological Evidence of the Transmission of Avian and Human Influenza A Viruses in Wild Pigs in Campeche, Mexico

Influenza, a zoonosis caused by various influenza A virus subtypes, affects a wide range of species, including humans. Pig cells express both sialyl-α-2,3-Gal and sialyl-α-2,6-Gal receptors, which make them susceptible to infection by avian and human viruses, respectively. To date, it is not known whether wild pigs in Mexico are affected by influenza virus subtypes, nor whether this would make them a potential risk of influenza transmission to humans. In this work, 61 hogs from two municipalities in Campeche, Mexico, were sampled. Hemagglutination inhibition assays were performed in 61 serum samples, and positive results were found for human H1N1 (11.47%), swine H1N1 (8.19%), and avian H5N2 (1.63%) virus variants. qRT-PCR assays were performed on the nasal swab, tracheal, and lung samples, and 19.67% of all hogs were positive to these assays. An avian H5N2 virus, first reported in 1994, was identified by sequencing. Our results demonstrate that wild pigs are participating in the exposure, transmission, maintenance, and possible diversification of influenza viruses in fragmented habitats, highlighting the synanthropic behavior of this species, which has been poorly studied in Mexico.

A Molecular Immunoproteomics Approach to Assess the Viral Antigenicity of Influenza

New surveillance methods employing mass spectrometry (MS) have been developed to characterize the influenza virus and, by extension, other biopathogens at the molecular level. The structure and antigenicity of protein antigens on the surface of the viral capsid are screened in a single step employing the immunoproteomics MS-based approach. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) coupled to gel electrophoresis is used both to identify viral antigens and screen their antigenicity. Evidence that antigen-antibody complexes, and protein complexes more generally, can survive on conventional MALDI targets has allowed both the primary structure and antigenicity of viral strains to be rapidly screened and protein epitopes to be identified with molecular precision. The approach should aid in future screening of the virus and assist in the development of immunogenic peptide constructs as alternative treatments to vaccination over the whole inactivated virus. The assay adds to the repertoire of mass spectrometric approaches for examining antigen-antibody interactions, in particular, and protein complexes, in general, without the need to immobilize, tag, or recover either component.

WHO guide on the economic evaluation of influenza vaccination

Influenza is responsible for substantial morbidity and mortality across the globe, with a large share of the total disease burden occurring in low- and middle-income countries (LMICs). There have been relatively few economic evaluations assessing the value of seasonal influenza vaccination in LMICs. The purpose of this guide is to outline the key theoretical concepts and best practice in methodologies and to provide guidance on the economic evaluation of influenza vaccination in LMICs. It outlines many of the influenza vaccine-specific challenges and should help to provide a framework for future evaluations in the area to build upon.

Plasmacytoid Dendritic Cells Contribute to the Protective Immunity Induced by Intranasal Treatment with Fc-fused Interleukin-7 against Lethal Influenza Virus Infection

Developing a novel vaccine that can be applied against multiple strains of influenza virus is of utmost importance to human health. Previously, we demonstrated that the intranasal introduction of Fc-fused IL-7 (IL-7-mFc), a long-acting cytokine fusion protein, confers long-lasting prophylaxis against multiple strains of influenza A virus (IAV) by inducing the development of lung-resident memory-like T cells, called T_RM-like cells. Here, we further investigated the mechanisms of IL-7-mFc-mediated protective immunity to IAVs. First, we found that IL-7-mFc treatment augments the accumulation of pulmonary T cells in 2 ways: recruiting blood circulating T cells into the lung and expanding T cells at the lung parenchyma. Second, the blockade of T cell migration from the lymph nodes (LNs) with FTY720 treatment was not required for mounting the protective immunity to IAV with IL-7-mFc, suggesting a more important role of IL-7 in T cells in the lungs. Third, IL-7-mFc treatment also recruited various innate immune cells into the lungs. Among these cells, plasmacytoid dendritic cells (pDCs) play an important role in IL-7-mFc-mediated protective immunity through reducing the immunopathology and increasing IAV-specific cytotoxic T lymphocyte (CTL) responses. In summary, our results show that intranasal treatment with IL-7-mFc modulates pulmonary immune responses to IAV, affecting both innate and adaptive immune cells.

Influenza vaccination for patients with chronic obstructive pulmonary disease: understanding immunogenicity, efficacy and effectiveness

Influenza infection is an important cause of global mortality and morbidity with the greatest impact on older people and those with chronic disease. Patients with chronic obstructive pulmonary disease (COPD) are particularly vulnerable to influenza, with evidence for increased incidence and severity of infection. In this patient group influenza is associated with exacerbations and pneumonia which result in a significant healthcare burden and premature mortality. Influenza vaccination and in particular the use of the seasonal trivalent influenza vaccine (TIV) is recommended for patients with COPD. The evidence base for its effects in this population is, however, limited. Available data suggest that immunogenicity is variable in COPD but the underlying mechanisms are not completely understood. The contribution of age, disease severity, comorbidity and treatments to vaccine responses has only been investigated in a limited manner. Existing data suggest that key immune mechanisms governing T- and B-cell responses are adversely affected by these factors. The efficacy of TIV has been studied in a number of small clinical trials which form the basis of a Cochrane review. Here evidence for effect is conflicting depending on individual trial design and inclusions. Overall, TIV offers protection against influenza infection in the trial setting but further studies are required to stratify patients and enable prediction of inadequate responses. Larger-scale clinical studies have largely been observational and have often been conducted in consort with pneumonia vaccination. Overall the mortality benefit of TIV in COPD is suggested by a number studies but the impact on exacerbation prevention is less clear. Influenza vaccination currently plays an important role in disease prevention in COPD. However, we postulate that a more in-depth understanding of mechanisms of response in the context of a highly heterogeneous disease will lead to a more informed approach to vaccination and greater benefit for the individual patient.

Investigation of the free energy profiles of amantadine and rimantadine in the AM2 binding pocket

The purpose of this work was to study the mechanism of drug resistance of M2 channel proteins by analyzing the interactions between the drugs amantadine and rimantadine and M2 channel proteins (including the wild type and the three mutants V27A, S31N, and G34A) and the drug binding pathways, by use of a computational approach. Our results showed that multiple drug-binding sites were present in the M2 channel, and the trajectory of the drugs through the M2 channel was determined. A novel method was developed to investigate of free energy profiles of the ligand-protein complexes. Our work provides a new explanation of the large amount of experimental data on drug efficacy.

Programming of Influenza Vaccine Broadness and Persistence by Mucoadhesive Polymer-Based Adjuvant Systems

The development of an anti-influenza vaccine with the potential for cross-protection against seasonal drift variants as well as occasionally emerging reassortant viruses is essential. In this study, we successfully generated a novel anti-influenza vaccine system combining conserved matrix protein 2 (sM2) and stalk domain of hemagglutinin (HA2) fusion protein (sM2HA2) and poly-γ-glutamic acid (γ-PGA)-based vaccine adjuvant systems that can act as a mucoadhesive delivery vehicle of sM2HA2 as well as a robust strategy for the incorporation of hydrophobic immunostimulatory 3-O-desacyl-4'-monophosphoryl lipid A (MPL) and QS21. Intranasal coadministration of sM2HA2 and the combination adjuvant γ-PGA/MPL/QS21 (CA-PMQ) was able to induce a high degree of protective mucosal, systemic, and cell-mediated immune responses. The sM2HA2/CA-PMQ immunization was able to prevent disease symptoms, confering complete protection against lethal infection with divergent influenza subtypes (H5N1, H1N1, H5N2, H7N3, and H9N2) that lasted for at least 6 mo. Therefore, our data suggest that mucosal administration of sM2HA2 in combination with CA-PMQ could be a potent strategy for a broad cross-protective influenza vaccine, and CA-PMQ as a mucosal adjuvant could be used for effective mucosal vaccines.

Heterosubtypic protective immunity against widely divergent influenza subtypes induced by fusion protein 4sM2 in BALB/c mice

Background

Regular reformulation of currently available vaccines is necessary due to the unpredictable variability of influenza viruses. Therefore, vaccine based on a highly conserved antigen with capability of induction of effective immune responses could be a potential solution. Influenza matrix protein-2 (M2) is highly conserved across influenza subtypes and a promising candidate for a broadly protective influenza vaccine. For the enhancement of broad protection, four tandem copies of consensus M2 gene containing extracellular (ED) and cytoplasmic (CD) without the trans-membrane domain (TM) reconstituted from H1N1, H5N1 and H9N2 influenza viruses were linked and named as 4sM2. The construct was effectively expressed in Escherichia coli, purified and proteins were used to immunize BALB/c mice. Humoral and cell-mediated immune responses were investigated following administration.

Results

Mice were intramuscularly immunized with 4sM2 protein 2 times at 2 weeks interval. Two weeks after the last immunization, first humoral and cell mediated immune response specific to sM2 protein were evaluated and the mice were challenged with a lethal dose (10MLD₅₀) of divergent subtypes A/EM/Korea/W149/06(H5N1), A/PR/8/34(H1N1), A/Aquatic bird/Korea/W81/2005(H5N2), A/Aquatic bird/Korea/W44/2005(H7N3), and A/Chicken/Korea/116/2004(H9N2) viruses. The efficacy of 4sM2 was evaluated by determining survival rates, body weights and residual lung viral titers. Our studies demonstrate that the survival of mice immunized with 4sM2 was significantly higher (80–100% survival) than that of unimmunized mice (0% survival). We also examined the long lasting protection against heterosubtype H5N2 virus and found that mice vaccinated with 4sM2 displayed 80% of protection even after 6 months of final vaccination.

Conclusion

Taken together, these results suggest that prokaryotic expressed multimeric sM2 protein achieved cross protection against lethal infection of divergent influenza subtypes which are lasting for the long time.

Positive network assortativity of influenza vaccination at a high school: implications for outbreak risk and herd immunity

Schools are known to play a significant role in the spread of influenza. High vaccination coverage can reduce infectious disease spread within schools and the wider community through vaccine-induced immunity in vaccinated individuals and through the indirect effects afforded by herd immunity. In general, herd immunity is greatest when vaccination coverage is highest, but clusters of unvaccinated individuals can reduce herd immunity. Here, we empirically assess the extent of such clustering by measuring whether vaccinated individuals are randomly distributed or demonstrate positive assortativity across a United States high school contact network. Using computational models based on these empirical measurements, we further assess the impact of assortativity on influenza disease dynamics. We found that the contact network was positively assortative with respect to influenza vaccination: unvaccinated individuals tended to be in contact more often with other unvaccinated individuals than with vaccinated individuals, and these effects were most pronounced when we analyzed contact data collected over multiple days. Of note, unvaccinated males contributed substantially more than unvaccinated females towards the measured positive vaccination assortativity. Influenza simulation models using a positively assortative network resulted in larger average outbreak size, and outbreaks were more likely, compared to an otherwise identical network where vaccinated individuals were not clustered. These findings highlight the importance of understanding and addressing heterogeneities in seasonal influenza vaccine uptake for prevention of large, protracted school-based outbreaks of influenza, in addition to continued efforts to increase overall vaccine coverage.

Key issues for estimating the impact and cost-effectiveness of seasonal influenza vaccination strategies

Many countries have considered or are considering modifying their seasonal influenza immunization policies. Estimating the impact of such changes requires understanding the existing clinical and economic burden of influenza, as well as the potential impact of different vaccination options. Previous studies suggest that vaccinating clinical risk groups, health care workers, children and the elderly may be cost-effective. However, challenges in such estimation include: (1) potential cases are not usually virologically tested; (2) cases have non-specific symptoms and are rarely reported to surveillance systems; (3) endpoints for influenza proxies (such as influenza-like illness) need to be matched to case definitions for treatment costs, (4) disease burden estimates vary from year to year with strain transmissibility, virulence and prior immunity, (5) methods to estimate productivity losses due to influenza vary, (6) vaccine efficacy estimates from trials differ due to variation in subtype prevalence, vaccine match and case ascertainment, and (7) indirect (herd) protection from vaccination depends on setting-specific variables that are difficult to directly measure. Given the importance of knowing the impact of changes to influenza policy, such complexities need careful treatment using tools such as population-based trial designs, meta-analyses, time-series analyses and transmission dynamic models.

Similarity in Pharmacokinetics of Oseltamivir and Oseltamivir Carboxylate in Japanese and Caucasian Subjects

The pharmacokinetics of oseltamivir and oseltamivir carboxylate in healthy Japanese (n = 14) and Caucasian (n = 14) males were compared. Subjects in each ethnic group were randomized to twice-daily oral oseltamivir 75 mg, 150 mg, or placebo for 13 doses. Oseltamivir was well tolerated across doses and ethnic groups. Oseltamivir was rapidly absorbed and hydrolyzed to oseltamivir carboxylate in all subjects. The mean plasma concentration-time profiles for oseltamivir and oseltamivir carboxylate were similar in Japanese and Caucasian subjects. At steady state, there was no evidence of any ethnic difference in the individual AUC(0-12) values for oseltamivir or oseltamivir carboxylate. Despite a significant difference in group mean body weight (approximately 20 kg) between the Japanese and Caucasian subjects, there was no evidence that dose-adjusted AUC(0-12) and C(max) for oseltamivir carboxylate were affected by body weight or ethnicity. Day 7 trough concentrations (C(min)) for oseltamivir carboxylate markedly exceeded the IC(50) (50% inhibitory concentration) against influenza A and B isolates. In conclusion, the results of this study support the use of the same dose regimens of oseltamivir in both Caucasian and Japanese subjects because of similarity in pharmacokinetics.

An immunoproteomics approach to screen the antigenicity of the influenza virus

The structure and antigenicity of protein antigens of the influenza virus are screened in a single step employing an immunoproteomics approach. Matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) coupled to gel electrophoresis is used both to identify viral antigens and screen their antigenicity. Earlier evidence that antigen-antibody complexes can survive on MALDI targets has allowed both the primary structure and antigenicity of viral strains to be rapidly screened with the specific localization of protein epitopes. The approach is anticipated to have a greater role in the future surveillance of the virus and should also aid in the development of immunogenic peptide constructs as alternatives to whole virus for vaccination.

Microneedle and mucosal delivery of influenza vaccines

In recent years with the threat of pandemic influenza and other public health needs, alternative vaccination methods other than intramuscular immunization have received great attention. The skin and mucosal surfaces are attractive sites probably because of both noninvasive access to the vaccine delivery and unique immunological responses. Intradermal vaccines using a microinjection system (BD Soluvia(TM)) and intranasal vaccines (FluMist®) are licensed. As a new vaccination method, solid microneedles have been developed using a simple device that may be suitable for self-administration. Because coated microneedle influenza vaccines are administered in the solid state, developing formulations maintaining the stability of influenza vaccines is an important issue to be considered. Marketable microneedle devices and clinical trials remain to be developed. Other alternative mucosal routes such as oral and intranasal delivery systems are also attractive for inducing cross-protective mucosal immunity, but effective non-live mucosal vaccines remain to be developed.

Economic evaluations of childhood influenza vaccination: a critical review

The potential benefits of influenza vaccination programmes targeted at children have gained increasing attention in recent years. We conducted a literature search of economic evaluations of influenza vaccination in those aged ≤18 years. The search revealed 20 relevant articles, which were reviewed. The studies differed widely in terms of the costs and benefits that were included. The conclusions were generally favourable for vaccination, but often applied a wider perspective (i.e. including productivity losses) than the reference case for economic evaluations used in many countries. Several evaluations estimated outcomes from a single-year epidemiological study, which may limit their validity given the year-to-year variation in influenza transmissibility, virulence, vaccine match and prior immunity. Only one study used a dynamic transmission model able to fully incorporate the indirect herd protection to the wider community. The use of dynamic models offers great scope to capture the population-wide implications of seasonal vaccination efforts, particularly those targeted at children.

Under-explored assumptions in influenza vaccination models: implications for the universal vaccination of children

The aim of this study was to explore several important (but uncertain) assumptions in influenza models which affect the estimated benefits of vaccination programs. We combined consideration of these factors with the seasonal variability of influenza transmissibility to gain a better understanding of how they may influence influenza control efforts. As our case study, we considered the potential impact of universal seasonal childhood vaccination in Australia using a simplified age-stratified Susceptible Exposed Infectious Recovered (SEIR) model to simulate influenza epidemics and the impact of vaccination. We found that the choice of vaccine efficacy model was influential in determining the impact of vaccination. This choice interacted with other model assumption such as those around the infectiousness of asymptomatic cases and the match of the vaccine to the circulating strains. The methodological approach used to estimate influenza hospitalisations was also highly influential. Our study highlights the role that key modelling assumptions play when estimating the impact of vaccination against influenza.

Vaccine design of hemagglutinin glycoprotein against influenza

Influenza viruses continue to cause annual epidemics and pose the threat of a deadly global pandemic. Vaccination has remained the best approach for prevention and control of influenza infection. However, current influenza vaccines are only effective against closely-matched circulating strains, and therefore must be updated and administered every year. In this review, we discuss recent developments in the search for better influenza vaccines, especially using the major virus surface glycoprotein hemagglutinins (HAs). Understanding how glycans on HAs affect the immune response and knowledge of how broadly neutralizing antibodies are induced will pave the way for a cross-protective influenza vaccine that does not require frequent updates or annual immunizations.

Virus aggregating peptide enhances the cell-mediated response to influenza virus vaccine

Given the poor immunogenicity of current H5N1 influenza vaccines, additives and adjuvants remain a viable solution for increasing efficacy. Here, we demonstrate that a 20-amino acid peptide (EB) possessing influenza antiviral activity also enhances the immune response to H5N1 vaccination in mice. The addition of EB to formalin-inactivated whole-virus vaccine induced virion aggregation and these aggregates were readily engulfed by phagocytic cells in vitro. In vivo, mice vaccinated with a suboptimal dose of inactivated vaccine containing EB peptide had reduced morbidity, improved viral clearance, and faster recovery than mice receiving vaccine alone. This phenomenon was not accompanied by an increase in virus-specific antibodies. Instead, cell-mediated immunity was enhanced as demonstrated by increased interferon-γ production from splenocytes. This data demonstrates that the EB peptide may a useful adjuvant for boosting the efficacy of poorly immunogenic influenza vaccines.

Identification of the minimal active sequence of an anti-influenza virus peptide

The antiviral peptide, entry blocker (EB), inhibits influenza virus replication by preventing attachment to cells. Here, we identified the minimal and optimal EB sequence that retained antiviral activity with a 50% inhibitory concentration (IC(50)) and 50% effective concentration (EC(50)) similar to those of the full-length EB peptide and several truncated variants that possessed up to 10-fold lower IC(50)s. These data have implications for improving the antiviral efficacy of EB-derived peptides while decreasing production costs and easing synthesis.

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.

Inactivated split-virion seasonal influenza vaccine (Fluarix): a review of its use in the prevention of seasonal influenza in adults and the elderly

Fluarix is a trivalent, inactivated, split-virion influenza vaccine containing 15 microg haemagglutinin from each of the three influenza virus strains (including an H1N1 influenza A virus subtype, an H3N2 influenza A virus subtype and an influenza B virus) that are expected to be circulating in the up-coming influenza season. Fluarix is highly immunogenic in healthy adults and elderly, and exceeds the criteria that make it acceptable for licensure in various regions (including the US and Europe). In a large, phase III, placebo-controlled, double-blind trial conducted in the US (2004/2005) in subjects aged 18-64 years, postvaccination seroconversion rates against the H1N1, H3N2 and B antigens were 60-78% and respective postvaccination seroprotection rates were 97-99% in Fluarix recipients. Another phase III trial conducted in the US (2005/2006) established the noninferiority of Fluarix versus another trivalent inactivated influenza virus vaccine in subjects aged >or=18 years, including a subgroup of elderly subjects. In annual European registration trials, Fluarix has consistently exceeded the immunogenicity criteria set by the EU Committee for Medicinal Products for Human Use for adults and the elderly. Fluarix demonstrated immunogenicity in small, open-label studies in at-risk subjects. During a year when the vaccine was well matched to the circulating strain, Fluarix demonstrated efficacy against culture-confirmed influenza A and/or B in a placebo-controlled trial in adults aged 18-64 years. In addition, Fluarix vaccination of pregnant women demonstrated efficacy in reducing the rate of laboratory-confirmed influenza in the infants and reducing febrile respiratory illnesses in the mothers and their new-born infants in a randomized trial. Fluarix was generally well tolerated in adults and the elderly in well designed clinical trials and in the annual European registration trials, with most local and general adverse events being transient and mild to moderate in intensity. The most common adverse reactions in recipients of Fluarix were pain, redness or swelling at the injection site, muscle aches, fatigue, headache and arthralgia. In conclusion, Fluarix is an important means of decreasing the impact of seasonal influenza viruses on adults and the elderly.

Intanza 15 microg intradermal seasonal influenza vaccine: in older adults (aged >or=60 years)

Intradermal seasonal influenza vaccine delivered by a microneedle injection system (Intanza) contains inactivated split virion antigens from influenza type A (H1N1 and H3N2) and B strains as recommended annually by the WHO and the EU for the prevention of seasonal influenza. In randomized, comparator-controlled, phase III trials in elderly volunteers, Intanza 15 microg elicited a strong immune response against influenza virus. In a pivotal trial, seroprotection rates with Intanza 15 microg were significantly greater than with the intramuscular comparator vaccine Vaxigrip (primary endpoint). A strong immune response was also observed with Intanza 15 microg following second and third annual vaccinations in consecutive seasons in terms of seroprotective antibody titres for all three strains (H1N1, H3N2 and B). In another phase III trial, Intanza 15 microg was as immunogenic as the intramuscular, adjuvanted vaccine Fluad, with noninferiority established in terms of ratios of geometric mean titres against H1N1 and B strains using the haemagglutinin inhibition method and against all three strains using the single radial haemolysis method. Intanza 15 microg was generally well tolerated in clinical trials in the elderly, with the most common adverse events observed being solicited injection-site reactions. The majority of solicited injection-site reactions were mild and spontaneously resolved within 1-3 days of onset; transient, visible injection-site reactions with the intradermal route of injection are not surprising as the vaccine is injected close to the skin surface.

Combination chemotherapy for influenza

The emergence of pandemic H1N1 influenza viruses in April 2009 and the continuous evolution of highly pathogenic H5N1 influenza viruses underscore the urgency of novel approaches to chemotherapy for human influenza infection. Anti-influenza drugs are currently limited to the neuraminidase inhibitors (oseltamivir and zanamivir) and to M2 ion channel blockers (amantadine and rimantadine), although resistance to the latter class develops rapidly. Potential targets for the development of new anti-influenza agents include the viral polymerase (and endonuclease), the hemagglutinin, and the non-structural protein NS1. The limitations of monotherapy and the emergence of drug-resistant variants make combination chemotherapy the logical therapeutic option. Here we review the experimental data on combination chemotherapy with currently available agents and the development of new agents and therapy targets.

Influenza vaccines: the good, the bad, and the eggs

Outbreaks of influenza A viruses continue to cause morbidity and mortality worldwide. The global disease burden of influenza is substantial. While antiviral therapies are available, influenza vaccines are the mainstay of efforts to reduce the substantial health burden from seasonal influenza. Inactivated influenza vaccines have been available since the 1940s, with live attenuated, cold-adapted vaccines becoming available in the United States in 2003. In spite of the successes, more research is needed to develop more effective seasonal influenza vaccines that provide long-lasting immunity and broad protection against strains that differ antigenically from vaccine viruses. This review introduces the virus and its disease, the current state of seasonal and pandemic influenza vaccines, and the challenges we face in the future.

Tissue and host tropism of influenza viruses: importance of quantitative analysis

It is generally accepted that human influenza viruses preferentially bind to cell-surface glycoproteins/glycolipids containing sialic acids in alpha2,6-linkage; while avian and equine influenza viruses preferentially bind to those containing sialic acids in alpha2,3-linkage. Even though this generalized view is accurate for H3 subtype isolates, it may not be accurate and absolute for all subtypes of influenza A viruses and, therefore, needs to be reevaluated carefully and realistically. Some of the studies published in major scientific journals on the subject of tissue tropism of influenza viruses are inconsistent and caused confusion in the scientific community. One of the reasons for the inconsistency is that most studies were quantitative descriptions of sialic acid receptor distributions based on lectin or influenza virus immunohistochemistry results with limited numbers of stained cells. In addition, recent studies indicate that alpha2,3- and alpha2,6-linked sialic acids are not the sole receptors determining tissue and host tropism of influenza viruses. In fact, determinants for tissue and host tropism of human, avian and animal influenza viruses are more complex than what has been generally accepted. Other factors, such as glycan topology, concentration of invading viruses, local density of receptors, lipid raft microdomains, coreceptors or sialic acid-independent receptors, may also be important. To more efficiently control the global spread of pandemic influenza such as the current circulating influenza A H1N1, it is crucial to clarify the determinants for tissue and host tropism of influenza viruses through quantitative analysis of experimental results. In this review, I will comment on some conflicting issues related to tissue and host tropism of influenza viruses, discuss the importance of quantitative analysis of lectin and influenza virus immunohistochemistry results and point out directions for future studies in this area, which should lead to a better understanding of tissue and host tropism of influenza viruses.

Immunological effect of subunit influenza vaccine entrapped by liposomes

OBJECTIVE

To elevate the immunological effect of subunit influenza vaccine in infants and aged people (over 60) using liposomal adjuvant in the context of its relatively low immunity and to investigate the relation between vaccine antigens and liposomal characteristics.

METHODS

Several formulations of liposomal subunit influenza vaccine were prepared. Their relevant characteristics were investigated to optimize the preparation method. Antisera obtained from immunizinged mice were used to evaluate the antibody titers of various samples by HI and ELISA.

RESULTS

Liposomal trivalent influenza vaccine prepared by film evaporation in combinedation with freeze-drying significantly increased its immunological effect in SPF Balb/c mice. Liposomal vaccine stimulated the antibody titer of H3N2, H1N1, and B much stronger than conventional influenza vaccine. As a result, liposomal vaccine (mean size: 4.5-5.5 microm, entrapment efficiency: 30%-40%) significantly increased the immunological effect of subunit influenza vaccine.

CONCLUSION

The immune effect of liposomal vaccine depends on different antigens, and enhanced immunity is not positively correlated with the mean size of liposome or its entrapped efficiency.

Antivirals for the treatment and prevention of epidemic and pandemic influenza

Influenza is a highly contagious and debilitating disease that imposes an excess burden of complications and mortality. Antiviral therapy is the primary intervention for treatment and post‐exposure prophylaxis (PEP) of influenza. Amantadine and rimantadine are members of the M2 class of antiviral agents and are moderately effective in influenza management. However, their utility is compromised by high levels of resistance, tolerability concerns and a lack of efficacy against influenza B. An alternative class of agents, the neuraminidase inhibitors (NIs), represent the most advanced form of antiviral therapy available, and act by specifically inhibiting the neuraminidase enzymes that are present on all influenza subtypes. Two NIs, oseltamivir and zanamivir, are currently available for clinical use. Oseltamivir, the most widely used NI, is administered orally as a prodrug (oseltamivir carboxylate) and systemically distributed to all potential infection sites. Zanamivir, a second NI, is administered by inhalation via a disk inhaler and deposited primarily in the respiratory tract. When administered within 48 hours of symptom onset, both agents significantly reduce illness duration and symptom severity, and decrease the rate of influenza‐associated complications. With oseltamivir, greater benefits are detected with earlier treatment initiation (<12 hours). In PEP, both NIs effectively protect the close contacts of index cases from symptomatic influenza. Oseltamivir and zanamivir are generally well tolerated and associated with a low level of resistance. Emerging evidence supports the activity of both NIs against the H5N1avian influenza infection, which is a pandemic candidate. However, the WHO currently recommends the use of oseltamivir for the management of suspected cases, given the systemic nature of the H5N1 challenge. Ongoing studies are exploring the effectiveness of oseltamivir, zanamivir and other NIs for pandemic management.

Mass spectrometry analysis of the influenza virus

The role of mass spectrometry to probe characteristics of the influenza virus, and vaccine and antiviral drugs that target the virus, are reviewed. Genetic and proteomic approaches have been applied which incorporate high resolution mass spectrometry and mass mapping to genotype the virus and establish its evolution in terms of the primary structure of the surface protein antigens. A mass spectrometric immunoassay has been developed and applied to assess the structure and antigenicity of the virus in terms of the hemagglutinin antigen. The quantitation of the hemagglutinin antigen in vaccine preparations has also been conducted that is of importance to their efficacy. Finally, the characterization and quantitation of antiviral drugs against the virus, and their metabolites, have been monitored in blood, serum, and urine. The combined approaches demonstrate the strengths of modern mass spectrometric methods for the characterization of this killer virus. [This article was published online 10 September 2008. An error was subsequently identified. This notice is included in the online and print versions to indicate that both have been corrected 7 November 2008.]

Development of stable influenza vaccine powder formulations: challenges and possibilities

Influenza vaccination represents the cornerstone of influenza prevention. However, today all influenza vaccines are formulated as liquids that are unstable at ambient temperatures and have to be stored and distributed under refrigeration. In order to stabilize influenza vaccines, they can be brought into the dry state using suitable excipients, stabilizers and drying processes. The resulting stable influenza vaccine powder is independent of cold-chain facilities. This can be attractive for the integration of the vaccine logistics with general drug distribution in Western as well as developing countries. In addition, a stockpile of stable vaccine formulations of potential vaccines against pandemic viruses can provide an immediate availability and simple distribution of vaccine in a pandemic outbreak. Finally, in the development of new needle-free dosage forms, dry and stable influenza vaccine powder formulations can facilitate new or improved targeting strategies for the vaccine compound. This review represents the current status of dry stable inactivated influenza vaccine development. Attention is given to the different influenza vaccine types (i.e. whole inactivated virus, split, subunit or virosomal vaccine), the rationale and need for stabilized influenza vaccines, drying methods by which influenza vaccines can be stabilized (i.e. lyophilization, spray drying, spray-freeze drying, vacuum drying or supercritical fluid drying), the current status of dry influenza vaccine development and the challenges for ultimate market introduction of a stable and effective dry-powder influenza vaccine.

Manipulation of the bluetongue virus tubules for immunogen delivery

A multidisplay vaccine delivery system has been developed that is nonreplicating and has a protein-based particulate structure. The structure is composed of helical tubules comprising multiple copies of a single nonstructural (NS) protein 1 of bluetongue virus. The helical assemblies present the C terminus of the protein on the surface of the tubules, thereby displaying appended residues in regular and repeating arrays. The NS1 protein has been manipulated to carry chosen immunogens at this C terminus, such that many thousands of copies of the foreign immunogen are displayed on the surface of the tubules. The display system can accommodate more than 500 amino acid residues in length without perturbing the basic tubular structure. Many immunogens have been displayed and tested for immunogenicity and have been shown to stimulate both humoral and cellular responses. NS1 tubules represent a safe vaccine-delivery system with great potential in the vaccine arena.

Is exercise protective against influenza-associated mortality?

BACKGROUND

Little is known about the effect of physical exercise on influenza-associated mortality.

METHODS AND FINDINGS

We collected information about exercise habits and other lifestyles, and socioeconomic and demographic status, the underlying cause of death of 24,656 adults (21% aged 30-64, 79% aged 65 or above) who died in 1998 in Hong Kong, and the weekly proportion of specimens positive for influenza A (H3N1 and H1N1) and B isolations during the same period. We assessed the excess risks (ER) of influenza-associated mortality due to all-natural causes, cardiovascular diseases, or respiratory disease among different levels of exercise: never/seldom (less than once per month), low/moderate (once per month to three times per week), and frequent (four times or more per week) by Poisson regression. We also assessed the differences in ER between exercise groups by case-only logistic regression. For all the mortality outcomes under study in relation to each 10% increase in weekly proportion of specimens positive for influenza A+B, never/seldom exercise (as reference) was associated with 5.8% to 8.5% excess risks (ER) of mortality (P<0.0001), while low/moderate exercise was associated with ER which were 4.2% to 6.4% lower than those of the reference (P<0.001 for all-natural causes; P = 0.001 for cardiovascular; and P = 0.07 for respiratory mortality). Frequent exercise was not different from the reference (change in ER -0.8% to 1.7%, P = 0.30 to 0.73).

CONCLUSION

When compared with never or seldom exercise, exercising at low to moderate frequency is beneficial with lower influenza-associated mortality.

[Bird flu: what the intensivist must know]

In the last century, humankind has faced 3 major pandemics of influenza virus infections. The first one occurred in 1918 and caused a significant amount of deaths. It was also capable of crossing over species barrier and affecting mammals, and most worrisome, humans. Since then several outbreaks have been reported in the Southeast of Asia. Many patients with the flu-like illness have a severe course and the patient develops pneumonia and in some cases multiorgan failure involving liver, kidneys, brain and lungs. Since the virus lacks regulatory control of genetic division it undergoes constant mutations leading to new subtypes and, sometimes, new strains. The only drugs that have shown some protection are oseltamivir and zanamivir. It is crucial to develop effective and non-expensive vaccines to prevent the virus spread and infection not only in humans but in birds too.

The role of oseltamivir in the treatment and prevention of influenza in children

The burden of seasonal influenza in children is poorly recognized, in spite of the potential for severe and even life-threatening illness and common secondary complications. Children are a primary reservoir for the spread of influenza to both family members and the community, which imposes a sizeable social and economic strain. Although vaccination is the primary intervention against childhood influenza, the antiviral neuraminidase inhibitors, oseltamivir and zanamivir, provide treatment options. Oseltamivir is administered orally to children aged > 1 year and has been shown to cost-effectively reduce the influenza disease burden and duration of viral shedding. Additionally, oseltamivir postexposure prophylaxis provides protective efficacy for children and families. Oseltamivir has shown excellent tolerability and a low potential for viral resistance in pediatric studies. In the event of an influenza pandemic, oseltamivir is expected to be at the forefront of containment strategies. This article reviews the pharmacology, efficacy and tolerability of oseltamivir as treatment and prophylaxis in children.

Preclinical in vitro activity of QR-435 against influenza A virus as a virucide and in paper masks for prevention of viral transmission

Prophylaxis against influenza is difficult, and current approaches against pandemics may be ineffective because of shortages of the two proven classes of antivirals in the face of a large-scale infection. Herbal/natural products may represent an effective alternative to conventional attempts to protect against infection by avian influenza virus. QR-435, an all-natural compound of green tea extract and other agents, has been developed to provide protection against a wide range of viral infections. The antiviral activities of several QR-435 preparations as well as QR-435 (1) green tea extract were tested against A/Sydney/5/97 and A/Panama-Resvir 17 strains of avian influenza virus H3N2 by means of an assay based on Madin-Darby canine kidney cells. Toxic effects of QR-435 formulations on these cells were also evaluated as were the virucidal properties of a commercially available mask impregnated with QR-435. The efficacy of a QR-435/mask combination was compared with that of the QR control/mask combination, an untreated mask, and no mask. QR-435 had significant in vitro activity against H3N2 at concentrations that were not associated with significant cellular toxic effects. The antiviral activity of QR-435 (1) was similar to that of QR-435. Masks impregnated with QR-435 were highly effective in blocking the passage of live H3N2 virus. These preclinical results warrant further evaluation of the prophylactic use of QR-435 against viral infection in humans.

In vivo prophylactic activity of QR-435 against H3N2 influenza virus infection

BACKGROUND

Prophylaxis against influenza infection can take several forms, none of which is totally effective at preventing the spread of the disease. QR-435, an all-natural compound of green-tea extract and other agents, has been developed to protect against a range of viral infections, including the influenza subtype H3N2.

METHODS

Several different QR-435 formulations were tested against the two influenza A H3N2 viruses (A/Sydney/5/97 and A/Panama/2007/99) in the ferret model. Most experiments included negative (phosphate-buffered saline) and positive (oseltamivir 5 mg/kg, twice daily) controls. QR-435 and the control were administered 5 minutes after intranasal delivery of the virus as prophylaxis against infection resulting from exposure to infected but untreated ferrets and for prevention of transmission from infected and treated ferrets to untreated animals. Effects of QR-435 on seroconversion, virus shedding, and systemic sequelae of infection (weight loss, fever, reduced activity) were evaluated.

RESULTS

QR-435 prevented transmission and provided prophylaxis against influenza virus H3N2. Prophylaxis with QR-435 was significantly more than with oseltamivir in these experiments. Optimal in vivo efficacy of QR-435 requires a horseradish concentration of at least 50% of that in the original formulation, and the benefits of this preparation appear to be dose dependent.

CONCLUSIONS

QR-435 is effective for both prevention of H3N2 viral transmission and prophylaxis. These preclinical results warrant further evaluation of its prophylactic properties against avian influenza virus infection in humans.

Limitations of current prophylaxis against influenza virus infection

Avian influenza has been a source of worldwide concern since Hong Kong authorities detected the first outbreak in 1997. Mainly as a result of poultry-to-human transmission, more than 200 cases of infection in humans have been attributed to the A/H5, A/H7, and A/H9 viral subtypes, with a case fatality rate for A/H5N1 infections exceeding 50%. A mutant or reassortant virus capable of efficient human-to-human transmission can set off a pandemic. Increased attention to prophylaxis against viral infection has identified several potentially complementary approaches: nonpharmacologic measures (eg, travel restrictions), vaccination, chemotherapeutic agents, and herbal/natural products. All have significant limitations that point out the need for additional modalities. Herbal/natural products, particularly those based on green tea extract, offer promise as adjuncts or alternatives to current interventions and warrant further evaluation in well-controlled human trials.

Amantadine-Oseltamivir Combination therapy for H5N1 Influenza Virus Infection in Mice

Background

The clinical management of H5N1 influenza virus infection in humans remains unclear. Combination chemotherapy with drugs that target different viral proteins might be more effective than monotherapy.

Methods

BALB/c mice were treated by oral gavage for 5 days with amantadine (1.5, 15 or 30 mg/kg/day) and oseltamivir (1 or 10 mg/kg/day) separately or in combination. Mice were challenged 24 h after initiation of treatment with 10 mouse 50% lethal doses of either amantadine-sensitive (having S31 in the M2 protein) or amantadine-resistant (having N31 in the M2 protein) recombinant A/Vietnam/1203/04 (H5N1) virus.

Results

Combination treatment with amantadine (15 or 30 mg/kg/day) and oseltamivir (10 mg/kg/day) provided greater protection (60% and 90%, respectively) against lethal infection with amantadine-sensitive H5N1 virus than did monotherapy. Moreover, spread of the virus to the brain was prevented by both combination regimens. The efficacy of the drug combinations against amantadine-resistant H5N1 virus was comparable to that of oseltamivir alone. Oseltamivir produced a dose-dependent effect against both recombinant H5N1 viruses ( P<0.05) but did not provide complete protection against lethal infection. Importantly, no mutations in the HA, NA and M2 proteins were detected when the two drugs were used in combination.

Conclusions

Combination chemotherapy provided a survival advantage over single-agent treatment of mice inoculated with neurotropic H5N1 influenza virus. This strategy might be an option for the control of pandemic influenza viruses that are sensitive to amantadine. Combinations that include other drugs should be explored.

Fingerprinting a killer: surveillance of the influenza virus by mass spectrometry

Influenza is a deadly virus that continues to kill and inflict illness and suffering the world over. Despite a global surveillance strategy, an annual response to vaccine preparation and the development of new anti-viral drugs to treat the virus ahead of, or after, infection, no cure exists. Future pandemics are a very real threat and countries have mobilised efforts to stockpile treatments and prepare for outbreaks. A new surveillance approach in which the structure and antigenicity of the virus can be rapidly screened by mass spectrometry is expected to have a greater role in the characterisation of emerging influenza strains, even at the site of an outbreak.

Signature patterns revealed by microarray analyses of mice infected with influenza virus A and Streptococcus pneumoniae

We used cDNA microarrays to identify differentially expressed genes in mice in response to infections with influenza virus A/PR/8/34 (H1N1) and Streptococcus pneumoniae. Expression microarray analysis showed up-regulation and down-regulation of many genes involved in the defense, inflammatory response and intracellular signaling pathways including chemokine, apoptosis, MAPK, Notch, Jak-STAT, T-cell receptor and complement and coagulation cascades. We have revealed signature patterns of gene expression in mice infected with two different classes of pathogens: influenza virus A and S. pneumoniae. Quantitative real-time RT-PCR results confirmed microarray results for most of the genes tested. These studies document clear differences in gene expression profiles between mice infected with influenza virus A and S. pneumoniae. Identification of genes that are differentially expressed after respiratory infections can provide insights into the mechanisms by which the host interacts with different pathogens, useful information about stage of diseases and selection of suitable targets for early diagnosis and treatments. The advantage of this novel approach is that the detection of pathogens is based on the differences in host gene expression profiles in response to different pathogens instead of detecting pathogens directly.

Combination chemotherapy, a potential strategy for reducing the emergence of drug-resistant influenza A variants

Rapid development of resistant influenza variants after amantadine treatment is one of the main drawbacks of M2 blockers. On the other hand, the emergence of variants with low susceptibility to the neuraminidase (NA) inhibitors is limited. In the present study we examined whether combination therapy with two classes of anti-influenza drugs can affect the emergence of resistant variants in vitro. We observed that virus yields of human A/Nanchang/1/99 (H1N1), A/Panama/2007/99 (H3N2), and A/Hong Kong/156/97 (H5N1) viruses in MDCK cells were significantly reduced (P<0.005) when the cells were treated with the combination of amantadine and low doses of oseltamivir carboxylate (< or =1microM). After five sequential passages in MDCK cells, the M2 protein of viruses cultivated with amantadine alone mutated at positions V27A and S31N/I. Viruses cultivated with oseltamivir carboxylate (> or =0.001microM) possessed mutations in the hemagglutinin (HA) protein. These variants showed reduced efficiency of binding to sialic acid receptors and decreased sensitivity to NA inhibitor in plaque reduction assay. Importantly, no mutations in the HA, NA, and M2 proteins were detected when the drugs were used in combination. Our results suggest that combination chemotherapy with M2 blocker and NA inhibitor reduced the emergence of drug-resistant influenza variants in vitro. This strategy could be an option for the control of influenza virus infection, and combinations with other novel drugs should be explored.