Inflammatory responses to influenza vaccination at the extremes of age

Age affects the immune response to vaccination, with individuals at the extremes of age responding poorly. The initial inflammatory response to antigenic materials shapes the subsequent adaptive response and so understanding is required about the effect of age on the profile of acute inflammatory mediators. In this study we measured the local and systemic inflammatory response after influenza vaccination or infection in neonatal, young adult and aged mice. Mice were immunized intramuscularly with inactivated influenza vaccine with and without the adjuvant MF59 and then challenged with H1N1 influenza. Age was the major factor affecting the inflammatory profile after vaccination: neonatal mice had more interleukin-1α (IL-1α), C-reactive protein (CRP) and granulocyte-macrophage colony-stimulating factor (GMCSF), young adults more tumour necrosis factor-α (TNF), and elderly mice more interleukin-1 receptor antagonist (IL-1RA), IL-2RA and interferon-γ-induced protein 10 (IP10). Notably the addition of MF59 induced IL-5, granulocyte colony-stimulating factor (G-CSF), Keratinocyte Chemotractant (KC) and monocyte chemoattractant protein 1 (MCP1) in all ages of animals and levels of these cytokines correlated with antibody responses. Age also had an impact on the efficacy of vaccination: neonatal and young adult mice were protected against challenge, but aged mice were not. There were striking differences in the localization of the cytokine response depending on the route of exposure: vaccination led to a high serum response whereas intranasal infection led to a low serum response but a high lung response. In conclusion, we demonstrate that age affects the inflammatory response to both influenza vaccination and infection. These age-induced differences need to be considered when developing vaccination strategies for different age groups.

Challenges and opportunities of using liquid chromatography and mass spectrometry methods to develop complex vaccine antigens as pharmaceutical dosage forms

Liquid chromatographic methods, combined with mass spectrometry, offer exciting and important opportunities to better characterize complex vaccine antigens including recombinant proteins, virus-like particles, inactivated viruses, polysaccharides, and protein-polysaccharide conjugates. The current abilities and limitations of these physicochemical methods to complement traditional in vitro and in vivo vaccine potency assays are explored in this review through the use of illustrative case studies. Various applications of these state-of-the art techniques are illustrated that include the analysis of influenza vaccines (inactivated whole virus and recombinant hemagglutinin), virus-like particle vaccines (human papillomavirus and hepatitis B), and polysaccharide linked to protein carrier vaccines (pneumococcal). Examples of utilizing these analytical methods to characterize vaccine antigens in the presence of adjuvants, which are often included to boost immune responses as part of the final vaccine dosage form, are also presented. Some of the challenges of using chromatographic and LC-MS as physicochemical assays to routinely test complex vaccine antigens are also discussed.

Respiratory Infections in the U.S. Military: Recent Experience and Control

This comprehensive review outlines the impact of military-relevant respiratory infections, with special attention to recruit training environments, influenza pandemics in 1918 to 1919 and 2009 to 2010, and peacetime operations and conflicts in the past 25 years. Outbreaks and epidemiologic investigations of viral and bacterial infections among high-risk groups are presented, including (i) experience by recruits at training centers, (ii) impact on advanced trainees in special settings, (iii) morbidity sustained by shipboard personnel at sea, and (iv) experience of deployed personnel. Utilizing a pathogen-by-pathogen approach, we examine (i) epidemiology, (ii) impact in terms of morbidity and operational readiness, (iii) clinical presentation and outbreak potential, (iv) diagnostic modalities, (v) treatment approaches, and (vi) vaccine and other control measures. We also outline military-specific initiatives in (i) surveillance, (ii) vaccine development and policy, (iii) novel influenza and coronavirus diagnostic test development and surveillance methods, (iv) influenza virus transmission and severity prediction modeling efforts, and (v) evaluation and implementation of nonvaccine, nonpharmacologic interventions.

Enhanced immune responses by skin vaccination with influenza subunit vaccine in young hosts

Skin has gained substantial attention as a vaccine target organ due to its immunological properties, which include a high density of professional antigen presenting cells (APCs). Previous studies have demonstrated the effectiveness of this vaccination route not only in animal models but also in adults. Young children represent a population group that is at high risk from influenza infection. As a result, this group could benefit significantly from influenza vaccine delivery approaches through the skin and the improved immune response it can induce. In this study, we compared the immune responses in young BALB/c mice upon skin delivery of influenza vaccine with vaccination by the conventional intramuscular route. Young mice that received 5 μg of H1N1 A/Ca/07/09 influenza subunit vaccine using MN demonstrated an improved serum antibody response (IgG1 and IgG2a) when compared to the young IM group, accompanied by higher numbers of influenza-specific antibody secreting cells (ASCs) in the bone marrow. In addition, we observed increased activation of follicular helper T cells and formation of germinal centers in the regional lymph nodes in the MN immunized group, rapid clearance of the virus from their lungs as well as complete survival, compared with partial protection observed in the IM-vaccinated group. Our results support the hypothesis that influenza vaccine delivery through the skin would be beneficial for protecting the high-risk young population from influenza infection.

Modifications of cysteine residues in the transmembrane and cytoplasmic domains of a recombinant hemagglutinin protein prevent cross-linked multimer formation and potency loss

Background

Recombinant hemagglutinin (rHA) is the active component in Flublok®; a trivalent influenza vaccine produced using the baculovirus expression vector system (BEVS). HA is a membrane bound homotrimer in the influenza virus envelope, and the purified rHA protein assembles into higher order rosette structures in the final formulation of the vaccine. During purification and storage of the rHA, disulfide mediated cross-linking of the trimers within the rosette occurs and results in reduced potency. Potency is measured by the Single Radial Immuno-diffusion (SRID) assay to determine the amount of HA that has the correct antigenic form.

Results

The five cysteine residues in the transmembrane (TM) and cytoplasmic (CT) domains of the rHA protein from the H3 A/Perth/16/2009 human influenza strain have been substituted to alanine and/or serine residues to produce three different site directed variants (SDVs). These SDVs have been evaluated to determine the impact of the TM and CT cysteines on potency, cross-linking, and the biochemical and biophysical properties of the rHA. Modification of these cysteine residues prevents disulfide bond cross-linking in the TM and CT, and the resulting rHA maintains potency for at least 12 months at 25°C. The strategy of substituting TM and CT cysteines to prevent potency loss has been successfully applied to another H3 rHA protein (from the A/Texas/50/2012 influenza strain) further demonstrating the utility of the approach.

Conclusion

rHA potency can be maintained by preventing non-specific disulfide bonding and cross-linked multimer formation. Substitution of carboxy terminal cysteines is an alternative to using reducing agents, and permits room temperature storage of the vaccine.

Fast vaccine design and development based on correlates of protection (COPs)

New and reemerging infectious diseases call for innovative and efficient control strategies of which fast vaccine design and development represent an important element. In emergency situations, when time is limited, identification and use of correlates of protection (COPs) may play a key role as a strategic tool for accelerated vaccine design, testing, and licensure. We propose that general rules for COP-based vaccine design can be extracted from the existing knowledge of protective immune responses against a large spectrum of relevant viral and bacterial pathogens. Herein, we focus on the applicability of this approach by reviewing the established and up-coming COPs for influenza in the context of traditional and a wide array of new vaccine concepts. The lessons learnt from this field may be applied more generally to COP-based accelerated vaccine design for emerging infections.

Pandemic influenza vaccine: characterization of A/California/07/2009 (H1N1) recombinant hemagglutinin protein and insights into H1N1 antigen stability

Background

The recent H1N1 influenza pandemic illustrated the shortcomings of the vaccine manufacturing process. The A/California/07/2009 H1N1 pandemic influenza vaccine or A(H1N1)pdm09 was available late and in short supply as a result of delays in production caused by low yields and poor antigen stability. Recombinant technology offers the opportunity to shorten manufacturing time. A trivalent recombinant hemagglutinin (rHA) vaccine candidate for seasonal influenza produced using the baculovirus expression vector system (BEVS) was shown to be as effective and safe as egg-derived trivalent inactivated vaccine (TIV) in human clinical studies. In this study, we describe the characterization of the A/California/07/2009 rHA protein and compare the H1N1 pandemic rHA to other seasonal rHA proteins.

Results

Our data show that, like other rHA proteins, purified A/California/07/2009 rHA forms multimeric rosette-like particles of 20–40 nm that are biologically active and immunogenic in mice as assayed by hemagglutination inhibition (HAI) antibody titers. However, proteolytic digest analysis revealed that A/California/07/2009 rHA is more susceptible to proteolytic degradation than rHA proteins derived from other seasonal influenza viruses. We identified a specific proteolytic site conserved across multiple hemagglutinin (HA) proteins that is likely more accessible in A/California/07/2009 HA, possibly as a result of differences in its protein structure, and may contribute to lower antigen stability.

Conclusion

We conclude that, similar to the recombinant seasonal influenza vaccine, recombinant A(H1N1)pdm09 vaccine is likely to perform comparably to licensed A(H1N1)pdm09 vaccines and could offer manufacturing advantages.

Heterosubtypic antibody response elicited with seasonal influenza vaccine correlates partial protection against highly pathogenic H5N1 virus

Background

The spread of highly pathogenic avian influenza (HPAI) H5N1 virus in human remains a global health concern. Heterosubtypic antibody response between seasonal influenza vaccine and potential pandemic influenza virus has important implications for public health. Previous studies by Corti et al. and by Gioia et al. demonstrate that heterosubtypic neutralizing antibodies against the highly pathogenic H5N1 virus can be elicited with a seasonal influenza vaccine in humans. However, whether such response offers immune protection against highly pathogenic H5N1 virus remained to be determined.

Methodology/Principal Findings

In this study, using a sensitive influenza HA (hemagglutinin) and NA (neuraminidase) pseudotype-based neutralization (PN) assay we first confirmed that low levels of heterosubtypic neutralizing antibody response against H5N1 virus were indeed elicited with seasonal influenza vaccine in humans. We then immunized mice with the seasonal influenza vaccine and challenged them with lethal doses of highly pathogenic H5N1 virus. As controls, we immunized mice with homosubtypic H5N1 virus like particles (VLP) or PBS and challenged them with the same H5N1 virus. Here we show that low levels of heterosubtypic neutralizing antibody response were elicited with seasonal influenza vaccine in mice, which were significantly higher than those in PBS control. Among them 2 out of 27 whose immune sera exhibited similar levels of neutralizing antibody response as VLP controls actually survived from highly pathogenic H5N1 virus challenge.

Conclusions/Significance

Therefore, we conclude that low levels of heterosubtypic neutralizing antibody response are indeed elicited with seasonal influenza vaccine in humans and mice and at certain levels such response offers immune protection against severity of H5N1 virus infection.

Computational docking of antibody-antigen complexes, opportunities and pitfalls illustrated by influenza hemagglutinin

Antibodies play an increasingly important role in both basic research and the pharmaceutical industry. Since their efficiency depends, in ultimate analysis, on their atomic interactions with an antigen, studying such interactions is important to understand how they function and, in the long run, to design new molecules with desired properties. Computational docking, the process of predicting the conformation of a complex from its separated components, is emerging as a fast and affordable technique for the structural characterization of antibody-antigen complexes. In this manuscript, we first describe the different computational strategies for the modeling of antibodies and docking of their complexes, and then predict the binding of two antibodies to the stalk region of influenza hemagglutinin, an important pharmaceutical target. The purpose is two-fold: on a general note, we want to illustrate the advantages and pitfalls of computational docking with a practical example, using different approaches and comparing the results to known experimental structures. On a more specific note, we want to assess if docking can be successful in characterizing the binding to the same influenza epitope of other antibodies with unknown structure, which has practical relevance for pharmaceutical and biological research. The paper clearly shows that some of the computational docking predictions can be very accurate, but the algorithm often fails to discriminate them from inaccurate solutions. It is of paramount importance, therefore, to use rapidly obtained experimental data to validate the computational results.

Influenza pathogenesis: lessons learned from animal studies with H5N1, H1N1 Spanish, and pandemic H1N1 2009 influenza

Because cases of highly pathogenic influenza are rare, no systematic clinical studies have evaluated different therapeutic approaches. Instead, treatment recommendations are aimed at the alleviation of clinical signs and symptoms, especially the restoration of respiratory function, and at the inhibition of virus replication, assuming viral load is responsible for disease phenotype. Studies of highly pathogenic influenza in different animal models, especially nonhuman primates and ferrets, reproduce many of the key observations from clinical cases. Host-response kinetics reveal a delayed but broad activation of genes involved in the innate and acquired immune responses (innate responses produce inflammatory responses), which continue after the virus has been cleared and may contribute importantly to the clinical signs observed. Experimental animal models point to an important role for immune dysregulation in the pathogenesis of highly pathogenic influenza. The use of these models to develop and validate therapeutic approaches is just beginning, but published studies reveal the importance of early treatment with antivirals and show the potential and limitations of approaches aimed at the host response.

Stability kinetics of influenza vaccine coated onto microneedles during drying and storage

PURPOSE

This study sought to determine the effects of microneedle coating formulation, drying time and storage time on antigen stability and in vivo immunogenicity of influenza microneedle vaccines.

METHODS

The stability of inactivated influenza virus vaccine was monitored by hemagglutination (HA) activity and virus particle aggregation as a function of storage time and temperature with or without trehalose. In vivo immunogenicity of inactivated influenza vaccines coated onto microneedles was determined in mice by virus-specific antibody titers and survival rates.

RESULTS

In the absence of trehalose, HA activity decreased below 10% and to almost zero after 1 h and 1 month of drying, respectively. Addition of trehalose maintained HA activity above 60% after drying and above 20% after 1 month storage at 25°C. Loss of HA activity generally correlated with increased virus particle aggregation. Administration of microneedles coated with trehalose-stabilized influenza vaccine yielded high serum IgG antibody titers even after 1 month storage, and all animals survived with minimal weight loss after lethal challenge infection.

CONCLUSIONS

Inactivated influenza virus vaccine coated on microneedles with trehalose significantly improved the HA activity as well as in vivo immunogenicity of the vaccine after an extended time of storage.

Influenza immunization with trehalose-stabilized virus-like particle vaccine using microneedles

Morbidity and mortality due to seasonal and pandemic influenza could be reduced by simpler vaccination methods that enable improved vaccination coverage. In this study, solid metal microneedles coated with influenza virus-like particle (VLP) vaccine were inserted into skin for intradermal immunization. Microneedles were applied to the skin by hand and designed for simple administration with little or no training. Inclusion of trehalose in the coating formulation significantly increased vaccine stability during coating by maintaining hemagglutination activity. Mice vaccinated with stabilized microneedles developed strong antibody responses comparable to conventional intramuscular vaccination and were fully protected against subsequent viral challenge. Whereas, coating microneedles with a coating solution lacking trehalose led to only partial protection against lethal viral challenge. Therefore, our results show that microneedles coated with trehalose-stabilized VLP vaccine can be a promising tool for improving influenza vaccination.

Combination strategies for pandemic influenza response - a systematic review of mathematical modeling studies

BACKGROUND

Individual strategies in pandemic preparedness plans may not reduce the impact of an influenza pandemic.

METHODS

We searched modeling publications through PubMed and associated references from 1990 to 30 September 2009. Inclusion criteria were modeling papers quantifying the effectiveness of combination strategies, both pharmaceutical and non-pharmaceutical.

RESULTS

Nineteen modeling papers on combination strategies were selected. Four studies examined combination strategies on a global scale, 14 on single countries, and one on a small community. Stochastic individual-based modeling was used in nine studies, stochastic meta-population modeling in five, and deterministic compartmental modeling in another five. As part of combination strategies, vaccination was explored in eight studies, antiviral prophylaxis and/or treatment in 16, area or household quarantine in eight, case isolation in six, social distancing measures in 10 and air travel restriction in six studies. Two studies suggested a high probability of successful influenza epicenter containment with combination strategies under favorable conditions. During a pandemic, combination strategies delayed spread, reduced overall number of cases, and delayed and reduced peak attack rate more than individual strategies. Combination strategies remained effective at high reproductive numbers compared with single strategy. Global cooperative strategies, including redistribution of antiviral drugs, were effective in reducing the global impact and attack rates of pandemic influenza.

CONCLUSION

Combination strategies increase the effectiveness of individual strategies. They include pharmaceutical (antiviral agents, antibiotics and vaccines) and non-pharmaceutical interventions (case isolation, quarantine, personal hygiene measures, social distancing and travel restriction). Local epidemiological and modeling studies are needed to validate efficacy and feasibility.