Assessment of markers of the cell-mediated immune response after influenza virus infection in frail older adults

Hydrogen peroxide inactivation of influenza virus preserves antigenic structure and immunogenicity

The use of live virus in the laboratory requires additional precautions, such as personnel training and special equipment, in order to limit the transmission risk. This is a requirement which not all laboratories can fulfill. In this study, a viral inactivation method is introduced using hydrogen peroxide (H2O2), which maintains antigenicity. Three strains of influenza viruses were inactivated and the ex vivo cellular and humoral immune responses were further analyzed, by comparing them to live viruses, in ELISpot, Multiplex and ELISA assays. In all assays, the H2O2 inactivated viruses displayed comparable responses to the live viruses, suggesting that the inactivated viruses still elicited immunogenic responses even though inactivation was confirmed by lack of viral replication in MDCK cells. Taken together, this study demonstrates that influenza viruses inactivated with H2O2 retain immunogenicity and are able to both detect humoral and elicit cellular immune responses in vitro, which could reduce the need to handle live viruses in the laboratory.

Vaccinomics and a new paradigm for the development of preventive vaccines against viral infections

In this article we define vaccinomics as the integration of immunogenetics and immunogenomics with systems biology and immune profiling. Vaccinomics is based on the use of cutting edge, high-dimensional (so called "omics") assays and novel bioinformatics approaches to the development of next-generation vaccines and the expansion of our capabilities in individualized medicine. Vaccinomics will allow us to move beyond the empiric "isolate, inactivate, and inject" approach characterizing past vaccine development efforts, and toward a more detailed molecular and systemic understanding of the carefully choreographed series of biological processes involved in developing viral vaccine-induced "immunity." This enhanced understanding will then be applied to overcome the obstacles to the creation of effective vaccines to protect against pathogens, particularly hypervariable viruses, with the greatest current impact on public health. Here we provide an overview of how vaccinomics will inform vaccine science, the development of new vaccines and/or clinically relevant biomarkers or surrogates of protection, vaccine response heterogeneity, and our understanding of immunosenescence.

Clinical and immunologic predictors of influenza illness among vaccinated older adults

The diagnosis of influenza is often missed in older adults and illness presentation may be modified by prior vaccination. We evaluated the symptoms and immunologic markers predicting laboratory-confirmed influenza (LCI) among vaccinated older adults. In subjects with influenza-like illness (ILI), fever distinguished subjects with laboratory-confirmed influenza (LCI) from those with other ILI (39% vs. 12.5%, p=0.009). In LCI subjects who did not seroconvert to influenza infection, pre-infection levels of the cytolytic mediator, granzyme B, correlated with fever (r=1.000; p=0.01) and the IFN-gamma:IL-10 ratio (r=0.999; p=0.03), and increased following influenza infection in LCI vs. ILI subjects (p=0.03). The cell-mediated immune response to influenza distinguishes A/H3N2 LCI from other ILI in older adults, and suggests a link between cell-mediated immunity and influenza illness severity in vaccinated older adults.

Prospects for an influenza vaccine that induces cross-protective cytotoxic T lymphocytes

Our approach to vaccination against influenza is unique. For no other pathogen do we construct and produce a new vaccine every year in the face of uncertainty about the strains that will be circulating when it is used. The huge global cooperative effort that underpins this process reflects our awareness of the need to control this major pathogen. Moreover, the threat of devastation by a pandemic due to a newly emerging viral subtype has triggered an intense effort to improve and accelerate the production of vaccines for use if a pandemic arises. However, type A influenza viruses responsible for seasonal epidemics and those with the potential to cause a pandemic share amino acid sequences that form the targets of cytotoxic T lymphocytes (CTL). CTL activated by currently circulating viruses, therefore, offer a possible means to limit the impact of infection with future variant seasonal strains and even new subtypes. This review examines how cross-protective CTL can be exploited to improve influenza vaccination and issues that need to be considered when attempting to induce this type of immunity. We discuss the role of CTL responses in viral control and review the current knowledge relating to specificity and longevity of memory CD8(+) T cells, how vaccine antigen can be loaded into antigen-presenting cells to prime these responses and factors influencing the class of response induced. Application of these principles to the next generation of influenza vaccines should lead to much greater control of infection.

Immunosenescence Modulation by Vaccination

A decline in immune function is a hallmark of aging that leads to complicated illness from a variety of infectious diseases, cancer and other immune-mediated disorders, and may limit the ability to appropriately respond to vaccination. How vaccines might alter the senescent immune response and what are the immune correlates of protection will be addressed from the perspective of 1) stimulating a previously primed response as in the case of vaccines for seasonal influenza and herpes zoster, 2) priming the response to novel antigens such as pandemic influenza or other viruses, 3) vaccination against bacterial pathogens such as pneumococcus, and 4) altering the immune response to an endogenous protein as in the case of a vaccine against Alzheimer’s disease. In spite of the often limited efficacy of vaccines for older adults, influenza vaccination remains the only cost-saving medical intervention in this population. Thus, considerable opportunity exists to improve current vaccines and develop new vaccines as a preventive approach to a variety of diseases in older adults. Strategies for selecting appropriate immunologic targets for new vaccine development and evaluating how vaccines may alter the senescent immune response in terms of potential benefits and risks in the preclinical and clinical trial phases of vaccine development will be discussed.

Correlation of cellular immune responses with protection against culture-confirmed influenza virus in young children

The highly sensitive gamma interferon (IFN-gamma) enzyme-linked immunosorbent spot (ELISPOT) assay permits the investigation of the role of cell-mediated immunity (CMI) in the protection of young children against influenza. Preliminary studies of young children confirmed that the IFN-gamma ELISPOT assay was a more sensitive measure of influenza memory immune responses than serum antibody and that among seronegative children aged 6 to <36 months, an intranasal dose of 10(7) fluorescent focus units (FFU) of a live attenuated influenza virus vaccine (CAIV-T) elicited substantial CMI responses. A commercial inactivated influenza virus vaccine elicited CMI responses only in children with some previous exposure to related influenza viruses as determined by detectable antibody levels prevaccination. The role of CMI in actual protection against community-acquired, culture-confirmed clinical influenza by CAIV-T was investigated in a large randomized, double-blind, placebo-controlled dose-ranging efficacy trial with 2,172 children aged 6 to <36 months in the Philippines and Thailand. The estimated protection curve indicated that the majority of infants and young children with >or=100 spot-forming cells/10(6) peripheral blood mononuclear cells were protected against clinical influenza, establishing a possible target level of CMI for future influenza vaccine development. The ELISPOT assay for IFN-gamma is a sensitive and reproducible measure of CMI and memory immune responses and contributes to establishing requirements for the future development of vaccines against influenza, especially those used for children.

The unmet need in the elderly: Designing new influenza vaccines for older adults

Influenza is a serious illness and probably the single most important cause of excess disability and mortality during the winter months. In spite of limited efficacy in older adults, influenza vaccination is nevertheless a cost-saving medical intervention since it does reduce hospitalisation and death rates due to pneumonia, exacerbations of heart failure and, surprisingly, heart attacks and strokes. Yet hospitalisation and death rates for acute respiratory illnesses continue to rise in spite of widespread vaccination programs. As a person ages, the immune response to antigenic stimulation with the influenza virus shifts toward T helper type 2 cytokine production. This is associated with a relative reduction in cytotoxic T-cell activity and a reduced capacity to destroy infected host cells and clear the virus from infected lung tissue. Breakthrough strategies to improve the current influenza vaccines are required to avoid a crisis in health care. A targeted approach will develop vaccines that can reverse these age-related changes in T-cell responses, particularly the functions of cytotoxic T lymphocytes.

Isolation and characterization of novel single-chain Fv specific for human granzyme B

Granzyme B, a neutral serine protease, has been demonstrated to be a pivotal molecule for protective immunity against viral infection and cellular malignant transformation. To facilitate monitoring of granzyme B levels, we have recently applied phage display technology to produce single-chain Fv antibodies specific for granzyme B, as versatile alternatives and complementary reagents to currently available monoclonal antibodies. Through four rounds of panning on purified human granzyme B-coated on solid phase, three unique clones were isolated. Expressed soluble scFv antibodies demonstrated specific immunological applications including ELISA, Western blotting, immunoprecipitation and intracellular staining. Based on sequence analyses and structural modeling, one scFv, Fv17, may have overlapping antigen binding specificity with monoclonal antibodies 2C5/F5 and GB11. Owing to the availability of its DNA sequence and large scale production capability, Fv17 should be a superior reagent for monitoring granzyme B expression in natural killer cells and antigen specific CD8+ T cell immunity.

CD40 ligand (CD154) improves the durability of respiratory syncytial virus DNA vaccination in BALB/c mice

Respiratory syncytial virus (RSV) infection is the single most important cause of serious acute respiratory illness in children <1 year of age worldwide, and is associated with life-threatening pneumonia or bronchiolitis in the elderly. Current vaccine strategies include live, attenuated virus, subunit and DNA vaccines, however, none have been sufficiently safe, or shown to induce satisfactory long-term immunity, thus immune modulators are being considered to enhance the effectiveness of RSV vaccines. In this study, we examine CD40 ligand (CD40L) as an immune modulator to enhance the durability of DNA vaccines encoding RSV F and/or G glycoproteins in BALB/c mice. The addition of CD40L to DNA vaccines encoding the F glycoprotein enhanced virus clearance and some aspects of the immune response to RSV challenge, suggesting that CD40L may enhance the durability of RSV DNA vaccines.