Pandemic influenza vaccines - the challenges

Targeting tumour necrosis factor to ameliorate viral pneumonia

Pneumonia is a serious complication associated with inflammation of the lungs due to infection with viral pathogens. Seasonal and pandemic influenza viruses, variola virus (agent of smallpox) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2; agent of COVID-19) are some leading examples. Viral pneumonia is triggered by excessive inflammation associated with dysregulated cytokine production, termed 'cytokine storm'. Several cytokines have been implicated but tumour necrosis factor (TNF) plays a critical role in driving lung inflammation, severe lung pathology and death. Despite this, the exact role TNF plays in the aetiology and pathogenesis of virus infection-induced respiratory complications is not well understood. In this review, we discuss the pathological and immunomodulatory roles of TNF in contributing to immunopathology and resolution of lung inflammation, respectively, in mouse models of influenza- and smallpox (mousepox)-induced pneumonia. We review studies that have investigated dampening of inflammation on the outcome of severe influenza and orthopoxvirus infections. Most studies on the influenza model have evaluated the efficacy of treatment with anti-inflammatory drugs, including anti-TNF agents, in animal models on the day of viral infection. We question the merits of those studies as they are not transferable to the clinic given that individuals generally present at a hospital only after the onset of disease symptoms and not on the day of infection. We propose that research should be directed at determining whether dampening lung inflammation after the onset of disease symptoms will reduce morbidity and mortality. Such a treatment strategy will be more relevant clinically.

Microarray Gene Expression Dataset Re-analysis Reveals Variability in Influenza Infection and Vaccination

Influenza, a communicable disease, affects thousands of people worldwide. Young children, elderly, immunocompromised individuals and pregnant women are at higher risk for being infected by the influenza virus. Our study aims to highlight differentially expressed genes in influenza disease compared to influenza vaccination, including variability due to age and sex. To accomplish our goals, we conducted a meta-analysis using publicly available microarray expression data. Our inclusion criteria included subjects with influenza, subjects who received the influenza vaccine and healthy controls. We curated 18 microarray datasets for a total of 3,481 samples (1,277 controls, 297 influenza infection, 1,907 influenza vaccination). We pre-processed the raw microarray expression data in R using packages available to pre-process Affymetrix and Illumina microarray platforms. We used a Box-Cox power transformation of the data prior to our down-stream analysis to identify differentially expressed genes. Statistical analyses were based on linear mixed effects model with all study factors and successive likelihood ratio tests (LRT) to identify differentially-expressed genes. We filtered LRT results by disease (Bonferroni adjusted p < 0.05) and used a two-tailed 10% quantile cutoff to identify biologically significant genes. Furthermore, we assessed age and sex effects on the disease genes by filtering for genes with a statistically significant (Bonferroni adjusted p < 0.05) interaction between disease and age, and disease and sex. We identified 4,889 statistically significant genes when we filtered the LRT results by disease factor, and gene enrichment analysis (gene ontology and pathways) included innate immune response, viral process, defense response to virus, Hematopoietic cell lineage and NF-kappa B signaling pathway. Our quantile filtered gene lists comprised of 978 genes each associated with influenza infection and vaccination. We also identified 907 and 48 genes with statistically significant (Bonferroni adjusted p < 0.05) disease-age and disease-sex interactions, respectively. Our meta-analysis approach highlights key gene signatures and their associated pathways for both influenza infection and vaccination. We also were able to identify genes with an age and sex effect. This gives potential for improving current vaccines and exploring genes that are expressed equally across ages when considering universal vaccinations for influenza.

A systematic review and meta-analysis of cross-reactivity of antibodies induced by H7 influenza vaccine

Inoculation with vaccine is the major intervention currently used to prevent influenza infections. However, it will be a challenge to produce and implement a new vaccine when a novel highly pathogenic influenza virus emerges in humans as significant infections. H7 subtype influenza viruses have similar epitopes on hemagglutinin, which can induce cross-reactive antibodies. In this study, a meta-analysis of the cross-reactivity of antibodies induced by one H7 subtype influenza vaccine against other H7 subtypes was performed. Database search was conducted in PubMed, Cochrane Library, EMBASE, MEDLINE, Chinese Biological Medicine Database (CBM), and Wanfang. A total of 9 articles comprising 811 human subjects were included in this meta-analysis. All assessed H7 influenza vaccines induced vaccine strain-specific protective antibodies [seroconversion rate (SCR) = 0.74, 95% CI (0.65, 0.82); seroprotection rate (SPR) = 0.81, 95% CI (0.78, 0.83)]. All H7 influenza virus monovalent vaccines exhibited cross-reactivity tested by hemagglutinin inhibition test (HI), microneutralization test (MN) and immunosorbent assay (ELISA) to other H7 subtype viruses. H7N1, H7N3, H7N7, and H7N9 vaccines elicited cross-reactive antibodies against other H7 subtype influenza viruses [SCR = 0.66, 95% CI (0.50, 0.82); SPR = 0.79, 95% CI (0.67, 0.91)]. The pooled SCR (95%CI) of cross-reactivity of H7N1 and H7N3 vaccines were 0.88 (0.85, 0.91) and 0.40 (0.26, 0.54), respectively. The consolidated SPR (95%CI) of H7N1 and H7N7 vaccines were 0.89 (0.86, 0.92) and 0.93 (0.81, 1.06). All H7 vaccines induced cross-reactive antibodies against H7N9 viruses [SCR = 0.69, 95% CI (0.52, 0.86); SPR = 0.85, 95% CI (0.76, 0.94)]. H7 vaccines can be used to limit influenza infection when a new highly pathogenic H7 virus appears.

Comparative effectiveness of H7N9 vaccines in healthy individuals

BACKGROUND

Avian H7N9 influenza viruses possess a potential pandemic threat to public health worldwide, and have caused severe infection and high mortality in humans. A series of clinical trials of H7N9 vaccines have been completed. Meta-analyses need to be performed to assess the immunogenicity and safety of H7N9 vaccines.

METHODS

Database research with defined selection criteria was conducted in PubMed, Cochrane Central Register of Controlled Trials, the World Health Organization's International Clinical Trials Registry Platform, ClinicalTrials.gov, etc. Data from randomized clinical trials regarding the immunogenicity and safety of H7N9 vaccines were collected and meta-analyzed.

RESULTS

For non-adjuvanted H7N9 vaccines, high dose formulations induced limited immunogenicity and increased the risk of local and systemic adverse events, simultaneously. For adjuvanted H7N9 vaccines, on the one hand, ISCOMATRIX, MF59, AS03 and aluminium adjuvants applied in H7N9 vaccines could improve immune responses effectively, and non-aluminium adjuvants had superior performance in saving vaccine dose; on the other hand, aluminium adjuvant had the advantages of safety amongst these adjuvants applied in H7N9 vaccines.

CONCLUSION

H7N9 influenza vaccines with adjuvant might represent the optimal available option in an influenza pandemic, at present.

Controlling epidemics with transmissible vaccines

As the density of human and domestic animal populations increases, the threat of localized epidemics and global pandemics grows. Although effective vaccines have been developed for a number of threatening pathogens, manufacturing and disseminating vaccines in the face of a rapidly spreading epidemic or pandemic remains a formidable challenge. One potentially powerful solution to this problem is the use of transmissible vaccines. Transmissible vaccines are capable of spreading from one individual to another and are currently being developed for a range of infectious diseases. Here we develop and analyze mathematical models that allow us to quantify the benefits of vaccine transmission in the face of an imminent or ongoing epidemic. Our results demonstrate that even a small amount of vaccine transmission can greatly increase the rate at which a naïve host population can be protected against an anticipated epidemic and substantially reduce the size of unanticipated epidemics if vaccination is initiated shortly after pathogen detection. In addition, our results identify key biological properties and implementation practices that maximize the impact of vaccine transmission on infectious disease.

Oral immunization of a non-recombinant Lactococcus lactis surface displaying influenza hemagglutinin 1 (HA1) induces mucosal immunity in mice

Mucosal immunization of influenza vaccine is potentially an effective approach for the prevention and control of influenza. The objective of the present study was to evaluate the ability of oral immunization with a non-recombinant Lactococcus lactis displaying HA1/L/AcmA recombinant protein, LL-HA1/L/AcmA, to induce mucosal immune responses and to accord protection against influenza virus infection in mice. The LL-HA1/L/AcmA was orally administered into mice and the immune response was evaluated. Mice immunized with LL-HA1/L/AcmA developed detectable specific sIgA in faecal extract, small intestine wash, BAL fluid and nasal fluid. The results obtained demonstrated that oral immunization of mice with LL-HA1/L/AcmA elicited mucosal immunity in both the gastrointestinal tract and the respiratory tract. The protective efficacy of LL-HA1/L/AcmA in immunized mice against a lethal dose challenge with influenza virus was also assessed. Upon challenge, the non-immunized group of mice showed high susceptibility to influenza virus infection. In contrast, 7/8 of mice orally immunized with LL-HA1/L/AcmA survived. In conclusion, oral administration of LL-HA1/L/AcmA in mice induced mucosal immunity and most importantly, provided protection against lethal influenza virus challenge. These results highlight the potential application of L. lactis as a platform for delivery of influenza virus vaccine.

Equalizing access to pandemic influenza vaccines through optimal allocation to public health distribution points

Vaccines are arguably the most important means of pandemic influenza mitigation. However, as during the 2009 H1N1 pandemic, mass immunization with an effective vaccine may not begin until a pandemic is well underway. In the U.S., state-level public health agencies are responsible for quickly and fairly allocating vaccines as they become available to populations prioritized to receive vaccines. Allocation decisions can be ethically and logistically complex, given several vaccine types in limited and uncertain supply and given competing priority groups with distinct risk profiles and vaccine acceptabilities. We introduce a model for optimizing statewide allocation of multiple vaccine types to multiple priority groups, maximizing equal access. We assume a large fraction of available vaccines are distributed to healthcare providers based on their requests, and then optimize county-level allocation of the remaining doses to achieve equity. We have applied the model to the state of Texas, and incorporated it in a Web-based decision-support tool for the Texas Department of State Health Services (DSHS). Based on vaccine quantities delivered to registered healthcare providers in response to their requests during the 2009 H1N1 pandemic, we find that a relatively small cache of discretionary doses (DSHS reserved 6.8% in 2009) suffices to achieve equity across all counties in Texas.

Available influenza vaccines: immunization strategies, history and new tools for fighting the disease

The main public health strategy for containing influenza-related disease is annual vaccination, which is recommended for the elderly and others belonging to risk-factor categories, who present the highest morbidity and mortality, as reported by the World Health Organization (WHO) Recommendations. The availability of different influenza vaccine formulations makes the choice of the best immunization strategy a challenge for stakeholders and public health experts. Heterogeneity in at-risk categories included in national influenza vaccine recommendations still exists, in particular among European countries. Broader consensus is expected, which should positively impact on influenza vaccination coverage. The availability of quadrivalent vaccines, containing both influenza B lineages, offers the potential to improve protection by overcoming the drawbacks of wrongly predicting which B lineage will predominate in a given year.

Pretreatment of mice with oligonucleotide prop5 protects them from influenza virus infections

Influenza A virus is a successful parasite and requires host factors to complete its life cycle. Prop5 is an antisense oligonucleotide, targeting programmed cell death protein 5 (PDCD5). In this study, we tested the antiviral activity of prop5 against mouse-adapted A/FM/1/47 strain of influenza A virus in a mouse model. Prop5 intranasally administered the mice at dosages of 10 and 20 mg/kg/d at 24 h and 30 min before infection, provided 80% and 100% survival rates and prolonged mean survival days in comparison with influenza virus-infected mice (both p < 0.01). Moreover, viral titres in mice pretreated with prop5, at dose of 10 and 20 mg/kg/d, had declined significantly on day two, four, and six post-infection compared with the yields in infected mice (p < 0.05 or p < 0.01); lung index in mice pretreated with prop5 (20 mg/kg/d) had been inhibited on day six post-infection (p < 0.05). Western blotting and immunohistochemistry showed that prop5 could down-regulate the PDCD5 protein expression levels in lung tissues of infected mice. These data indicate that antisense oligonucleotide prop5 is a promising drug for prophylaxis and control influenza virus infections and provides an insight into the host-pathogen interaction.

Adenovirus-Based Vectors for the Development of Prophylactic and Therapeutic Vaccines

Emerging and reemerging infectious diseases as well as cancer pose great global health impacts on the society. Vaccines have emerged as effective treatments to prevent or reduce the burdens of already developed diseases. This is achieved by means of activating various components of the immune system to generate systemic inflammatory reactions targeting infectious agents or diseased cells for control/elimination. DNA virus-based genetic vaccines gained significant attention in the past decades owing to the development of DNA manipulation technologies, which allowed engineering of recombinant viral vectors encoding sequences for foreign antigens or their immunogenic epitopes as well as various immunomodulatory molecules. Despite tremendous progress in the past 50 years, many hurdles still remain for achieving the full clinical potential of viral-vectored vaccines. This chapter will present the evolution of vaccines from “live” or “attenuated” first-generation agents to recombinant DNA and viral-vectored vaccines. Particular emphasis will be given to human adenovirus (Ad) for the development of prophylactic and therapeutic vaccines. Ad biological properties related to vaccine development will be highlighted along with their advantages and potential hurdles to be overcome. In particular, we will discuss (1) genetic modifications in the Ad capsid protein to reduce the intrinsic viral immunogenicity, (2) antigen capsid incorporation for effective presentation of foreign antigens to the immune system, (3) modification of the hexon and fiber capsid proteins for Ad liver de-targeting and selective retargeting to cancer cells, (4) Ad-based vaccines carrying “arming” transgenes with immunostimulatory functions as immune adjuvants, and (5) oncolytic Ad vectors as a new therapeutic approach against cancer. Finally, the combination of adenoviral vectors with other non-adenoviral vector systems, the prime/boost strategy of immunization, clinical trials involving Ad-based vaccines, and the perspectives for the field development will be discussed.

Influenza Virus-like Particle Containing Two Different Subtypes of Hemagglutinin Confers Protection in Mice Against Lethal Challenge With A/PR8 (H1N1) and A/HK (H3N2) Viruses

BACKGROUND

Preventing the seasonal or pandemic outbreak of influenza can be powerful and cost-effective.

OBJECTIVES

In this study, we constructed a novel virus-like particle (VLP) platform that contains two hemagglutinin (HA) subtypes and evaluated immunogenicity of constructed VLP in mice.

MATERIALS AND METHODS

This recombinant candidate vaccine model resulted in the expression of two HAs of H1N1 and H3N2 subtypes co-localized within a VLP. Following infection of insect cells with recombinant baculovirus co-expressing H1, H3 and M1 proteins, VLPs with size of 80-120 nm were self-assembled, budding, and released into the insect culture medium. The resulting VLPs which contained two different subtypes of hemagglutinin were purified by ultracentrifugation. The immunogenicity of VLPs was evaluated in mice following immunization.

RESULTS

Our data showed that vaccination using VLPs elicited robust levels of serum IgG, and viral neutralizing antibodies against A/PR8 (H1N1) and A/HK (H3N2) viruses. Following challenge with lethal dose of A/PR8 (H1N1) and A/HK (H3N2, vaccinated mice were protected, displaying no sign of weight loss and mortality compared to non-vaccinated control mice.

CONCLUSIONS

VLPs can serve as a promising vaccination strategy to control influenza virus.

Advances and future challenges in recombinant adenoviral vectored H5N1 influenza vaccines

The emergence of a highly pathogenic avian influenza virus H5N1 has increased the potential for a new pandemic to occur. This event highlights the necessity for developing a new generation of influenza vaccines to counteract influenza disease. These vaccines must be manufactured for mass immunization of humans in a timely manner. Poultry should be included in this policy, since persistent infected flocks are the major source of avian influenza for human infections. Recombinant adenoviral vectored H5N1 vaccines are an attractive alternative to the currently licensed influenza vaccines. This class of vaccines induces a broadly protective immunity against antigenically distinct H5N1, can be manufactured rapidly, and may allow mass immunization of human and poultry. Recombinant adenoviral vectors derived from both human and non-human adenoviruses are currently being investigated and appear promising both in nonclinical and clinical studies. This review will highlight the current status of various adenoviral vectored H5N1 vaccines and will outline novel approaches for the future.