From lethal virus to life-saving vaccine: developing inactivated vaccines for pandemic influenza

MA, Tovar-Rosero YY, Oñate AA, O'Ryan M. Two centuries of vaccination: historical and conceptual approach and future perspectives

Over the past two centuries, vaccines have been critical for the prevention of infectious diseases and are considered milestones in the medical and public health history. The World Health Organization estimates that vaccination currently prevents approximately 3.5-5 million deaths annually, attributed to diseases such as diphtheria, tetanus, pertussis, influenza, and measles. Vaccination has been instrumental in eradicating important pathogens, including the smallpox virus and wild poliovirus types 2 and 3. This narrative review offers a detailed journey through the history and advancements in vaccinology, tailored for healthcare workers. It traces pivotal milestones, beginning with the variolation practices in the early 17th century, the development of the first smallpox vaccine, and the continuous evolution and innovation in vaccine development up to the present day. We also briefly review immunological principles underlying vaccination, as well as the main vaccine types, with a special mention of the recently introduced mRNA vaccine technology. Additionally, we discuss the broad benefits of vaccines, including their role in reducing morbidity and mortality, and in fostering socioeconomic development in communities. Finally, we address the issue of vaccine hesitancy and discuss effective strategies to promote vaccine acceptance. Research, collaboration, and the widespread acceptance and use of vaccines are imperative for the continued success of vaccination programs in controlling and ultimately eradicating infectious diseases.

A Review of Clinical Trials of Cancer and Its Treatment as a Vaccine

BACKGROUND

Cancer and infectious diseases are one of the greatest challenges of modern medicine. An unhealthy lifestyle, poor drug use, or drug misuse contribute to the rise in morbidity and mortality brought on by these illnesses. The inadequacies of the medications now being used to treat these disorders, along with the growing issue of drug resistance, have compelled researchers to look for novel compounds with therapeutic promise. The number of infections and diseases has significantly abated due to vaccine development and use over time, which is described in detail. Several novel vaccines can now be produced by manipulating Deoxyribonucleic acid (DNA), Ribonucleic acid (RNA), Messenger Ribonucleic acid (mRNA), proteins, viral vector Recombinant, and other molecules due to advances in genetic engineering and our understanding of the immune defense.

OBJECTIVE

The main topic of discussion is cancer-based vaccinations, which were developed less than a decade ago but have already been used to treat a wide range of both life-threatening and deadly diseases. It contains clinical studies for cancer vaccines against kidney, liver, prostate, cervix, and certain RNA-based cancer vaccines against breast and bladder cancer.

RESULTS

Numerous studies using various DNA and RNA-based methods have been conducted on the basis of cancer, with 9-10 diseases related to DNA and 8-9 diseases associated with RNA. Some of these studies have been completed, while others have been eliminated due to a lack of research; further studies are ongoing regarding the same.

CONCLUSION

This brief discussion of vaccines and their varieties with examples also discusses vaccine clinical trials in relation to cancer diseases in this DNA and RNA-based cancer vaccine that has had successful clinical trials like the cervical cancer drug VGX-3100, the kidney cancer drug Pembrolizumab, MGN-1601, the prostate cancer drug pTVG-HP with rhGM-CSF, the melanoma cancer drug proteasome siRNA, and the lung cancer drug FRAME-001.

Nanoparticles and Antiviral Vaccines

Viruses have threatened human lives for decades, causing both chronic and acute infections accompanied by mild to severe symptoms. During the long journey of confrontation, humans have developed intricate immune systems to combat viral infections. In parallel, vaccines are invented and administrated to induce strong protective immunity while generating few adverse effects. With advancements in biochemistry and biophysics, different kinds of vaccines in versatile forms have been utilized to prevent virus infections, although the safety and effectiveness of these vaccines are diverse from each other. In this review, we first listed and described major pathogenic viruses and their pandemics that emerged in the past two centuries. Furthermore, we summarized the distinctive characteristics of different antiviral vaccines and adjuvants. Subsequently, in the main body, we reviewed recent advances of nanoparticles in the development of next-generation vaccines against influenza viruses, coronaviruses, HIV, hepatitis viruses, and many others. Specifically, we described applications of self-assembling protein polymers, virus-like particles, nano-carriers, and nano-adjuvants in antiviral vaccines. We also discussed the therapeutic potential of nanoparticles in developing safe and effective mucosal vaccines. Nanoparticle techniques could be promising platforms for developing broad-spectrum, preventive, or therapeutic antiviral vaccines.

Meeting vaccine formulation challenges in an emergency setting: Towards the development of accessible vaccines

Vaccination is considered one of the most successful strategies to prevent infectious diseases. In the event of a pandemic or epidemic, the rapid development and distribution of the vaccine to the population is essential to reduce mortality, morbidity and transmission. As seen during the COVID-19 pandemic, the production and distribution of vaccines has been challenging, in particular for resource-constrained settings, essentially slowing down the process of achieving global coverage. Pricing, storage, transportation and delivery requirements of several vaccines developed in high-income countries resulted in limited access for low-and-middle income countries (LMICs). The capacity to manufacture vaccines locally would greatly improve global vaccine access. In particular, for the development of classical subunit vaccines, the access to vaccine adjuvants is a pre-requisite for more equitable access to vaccines. Vaccine adjuvants are agents required to augment or potentiate, and possibly target the specific immune response to such type of vaccine antigens. Openly accessible or locally produced vaccine adjuvants may allow for faster immunization of the global population. For local research and development of adjuvanted vaccines to expand, knowledge on vaccine formulation is of paramount importance. In this review, we aim to discuss the optimal characteristics of a vaccine developed in an emergency setting by focusing on the importance of vaccine formulation, appropriate use of adjuvants and how this may help overcome barriers for vaccine development and production in LMICs, achieve improved vaccine regimens, delivery and storage requirements.

Characterization of four novel H5N6 avian influenza viruses with the internal genes from H5N1 and H9N2 viruses and experimental challenge of chickens vaccinated with current commercially available H5 vaccines

Since 2014, highly pathogenic avian influenza H5N6 viruses have been responsible for outbreaks in poultry. In this study, four H5N6 virus strains were isolated from faecal samples of sick white ducks and dead chickens in Shandong in 2019. These H5N6 viruses were triple-reassortant viruses that have not been previously characterized. Their HA genes were derived from the H5 viruses and were closely related to the vaccine strain Re-11. Their NA genes all fell into the N6-like lineage and the internal gene were derived from H5N1 and H9N2 viruses. They all showed high pathogenicity in mice and caused lethal infection with high rates of transmission in chickens. Moreover, the SPF chickens inoculated with the currently used H5 (Re-11 and Re-12 strains)/H7 (H7-Re-2 strain) trivalent inactivated vaccines in China were completely protected from these four H5N6 viruses. Our study indicated the necessity of continued surveillance for H5 influenza A viruses and the importance of timely update of vaccine strains in poultry industry.

Sterilizing Immunity against COVID-19: Developing Helper T cells I and II activating vaccines is imperative

Six months after the publication of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) sequence, a record number of vaccine candidates were listed, and quite a number of them have since been approved for emergency use against the novel coronavirus disease 2019 (COVID-19). This unprecedented pharmaceutical feat did not only show commitment, creativity and collaboration of the scientific community, but also provided a swift solution that prevented global healthcare system breakdown. Notwithstanding, the available data show that most of the approved COVID-19 vaccines protect only a proportion of recipients against severe disease but do not prevent clinical manifestation of COVID-19. There is therefore the need to probe further to establish whether these vaccines can induce sterilizing immunity, otherwise, COVID-19 vaccination would have to become a regular phenomenon. The emergence of SARS-CoV-2 variants could further affect the capability of the available COVID-19 vaccines to prevent infection and protect recipients from a severe form of the disease. These notwithstanding, data about which vaccine(s), if any, can confer sterilizing immunity are unavailable. Here, we discuss the immune responses to viral infection with emphasis on COVID-19, and the specific adaptive immune response to SARS-CoV-2 and how it can be harnessed to develop COVID-19 vaccines capable of conferring sterilizing immunity. We further propose factors that could be considered in the development of COVID-19 vaccines capable of stimulating sterilizing immunity. Also, an old, but effective vaccine development technology that can be applied in the development of COVID-19 vaccines with sterilizing immunity potential is reviewed.

The characteristics of COVID-19 vaccine-related headache: Clues gathered from the healthcare personnel in the pandemic

Introduction

Headache is a frequent adverse event after viral vaccines. We aimed to investigate the frequency and clinical associations of COVID-19 vaccine-related headache.

Methods

The characteristics, associations of this headache, main comorbidities, headache history following the influenza vaccine and during COVID-19 were investigated using a web-based questionnaire.

Results

A total of 1819 healthcare personnel (mean age: 44.4 ± 13.4 years, 1222 females), vaccinated with inactivated virus, contributed to the survey; 209 (11.4%) had been infected with COVID-19. A total of 556 participants (30.6%) reported headache with significant female dominance (36.1% vs. 19.3%), 1.8 ± 3.5 (median: 1; IQR: 0–2) days following vaccination. One hundred and forty-four participants (25.9%) experienced headache lasting ≥3 days. Headache was mostly bilateral without accompanying phenomena, less severe, and shorter than COVID-19-related headache. The presence of primary headaches and migraine were significantly associated with COVID-19 vaccine-related headache (ORs = 2.16 [95% CI 1.74–2.68] and 1.65 [1.24–2.19], respectively). Headache during COVID-19 or following influenza vaccine also showed significant association with headache following COVID-19 vaccine (OR = 4.3 [95% CI 1.82–10.2] and OR = 4.84 [95% CI 2.84–8.23], respectively). Only thyroid diseases showed a significant association (OR = 1.54 [95% CI 1.15–2.08]) with vaccine-related headache among the common comorbidities.

Conclusion

Headache is observed in 30.6% of the healthcare workers following COVID-19 vaccine and mostly experienced by females with pre-existing primary headaches, thyroid disorders, headache during COVID-19, or headache related to the influenza vaccine.

Neurological Manifestation of SARS-CoV-2 Induced Inflammation and Possible Therapeutic Strategies Against COVID-19

There are regular reports of extrapulmonary infections and manifestations related to the ongoing COVID-19 pandemic. Coronaviruses are potentially neurotropic, which renders neuronal tissue vulnerable to infection, especially in elderly individuals or in those with neuro-comorbid conditions. Complaints of ageusia, anosmia, myalgia, and headache; reports of diseases such as stroke, encephalopathy, seizure, and encephalitis; and loss of consciousness in patients with COVID-19 confirm the neuropathophysiological aspect of this disease. The brain is linked to pulmonary organs, physiologically through blood circulation, and functionally through the nervous system. The interdependence of these vital organs may further aggravate the pathophysiological aspects of COVID-19. The induction of a cytokine storm in systemic circulation can trigger a neuroinflammatory cascade, which can subsequently compromise the blood-brain barrier and activate microglia- and astrocyte-borne Toll-like receptors, thereby leading to neuronal tissue damage. Hence, a holistic approach should be adopted by healthcare professionals while treating COVID-19 patients with a history of neurodegenerative disorders, neuropsychological complications, or any other neuro-compromised conditions. Imperatively, vaccines are being developed at top priority to contain the spread of the severe acute respiratory syndrome coronavirus 2, and different vaccines are at different stages of development globally. This review discusses the concerns regarding the neuronal complications of COVID-19 and the possible mechanisms of amelioration.

Essential considerations during vaccine design against COVID-19 and review of pioneering vaccine candidate platforms

The calamity of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV2), COVID-19, is still a global human tragedy. To date, no specific antiviral drug or therapy has been able to break the widespread of SARS-CoV2. It has been generally believed that stimulating protective immunity via universal vaccination is the individual strategy to manage this pandemic. Achieving an effective COVID-19 vaccine requires attention to the immunological and non-immunological standpoints mentioned in this article. Here, we try to introduce the considerable immunological aspects, potential antigen targets, appropriate adjuvants as well as key points in the various stages of COVID-19 vaccine development. Also, the principal features of the preclinical and clinical studies of pioneering COVID-19 vaccine candidates were pointed out by reviewing the available information. Finally, we discuss the key challenges in the successful design of the COVID-19 vaccine and address the most fundamental strengths and weaknesses of common vaccine platforms.

COVID-19 immunity and vaccines: what a pharmacist needs to know

COVID-19 vaccines are being produced using different platforms by different companies, some of which are entering Phase 3 and 4 trials. Due to the pandemic, this production has been accelerated, which leaves a window for speculation on the method of production and safety. Pharmacists are familiar with vaccination; however, COVID-19 vaccines are still new and further work is needed to clarify many aspects, including side effects, methods of storage, and number of doses. Prioritization of vaccination has been implemented to a certain extent, but no clear strategy is available. A comprehensive overview on immunity and immunological principles for the design of COVID-19 vaccine strategies is provided in this narrative review and the current COVID-19 vaccine landscape is discussed, in addition to exploring the principles for prioritization of vaccination using data from articles available in PubMed and from health organizations. Pharmacists should have a better understanding of COVID-19 vaccines and their manufacture. This would also allow better counseling of the public on COVID 19, immunization, and explaining prioritization basis and vaccination programs.

A Replication-Defective Influenza Virus Harboring H5 and H7 Hemagglutinins Provides Protection against H5N1 and H7N9 Infection in Mice

The recent highly pathogenic avian influenza (HPAI) H5N1 and H7N9 viruses have caused hundreds of human infections with high mortality rates. Although H5N1 and H7N9 viruses have been limited mainly to avian species, there is high potential for these viruses to acquire human-to-human transmission and initiate a pandemic. A highly safe and effective vaccine is needed to protect against a potential H5N1 or H7N9 influenza pandemic. Here, we report the generation and evaluation of two reassortant influenza viruses, PR8-H5-H7_NA and PR8-H7-H5_NA These viruses contain six internal segments from A/Puerto Rico/8/1934 (PR8), the HA segment from either A/Alberta/01/2014 (H5N1) [AB14 (H5N1)] or A/British Columbia/01/2015 (H7N9) [BC15 (H7N9)], and a chimeric NA segment with either the BC15 (H7N9) HA gene or the AB14 (H5N1) HA gene flanked by the NA packaging signals of PR8. These viruses expressed both H5 and H7 HAs in infected cells, replicated to high titers when exogenous NA was added to the culture medium in vitro, and were replication defective and nonvirulent when administered intranasally in mice. Moreover, intranasal vaccination with PR8-H5-H7_NA elicited robust immune responses to both H5 and H7 viruses, conferring complete protection against both AB14 (H5N1) and BC15 (H7N9) challenges in mice. Conversely, vaccination with PR8-H7-H5_NA only elicited robust immune responses toward the H7 virus, which conferred complete protection against BC15 (H7N9) but not against AB14 (H5N1) in mice. Therefore, PR8-H5-H7_NA has strong potential to serve as a vaccine candidate against both H5 and H7 subtypes of influenza viruses.IMPORTANCE Avian influenza H5N1 and H7N9 viruses infected humans with high mortality rates. A highly safe and effective vaccine is needed to protect against a potential pandemic. We generated and evaluated two reassortant influenza viruses, PR8-H5-H7_NA and PR8-H7-H5_NA, as vaccine candidates. Each virus contains one type of HA in segment 4 and the other subtype of HA in segment 6, thereby expressing both H5 and H7 subtypes of the HA molecule. The replication of viruses is dependent on the addition of exogenous NA in cell culture and is replication defective in vivo Vaccination of PR8-H5-H7_NA virus confers protection to both H5N1 and H7N9 virus challenge; conversely, vaccination of PR8-H7-H5_NA provides protection only to H7N9 virus challenge. Our data revealed that when engineering such a virus, the H5 or H7 HA in segment 6 affects the immunogenicity. PR8-H5-H7_NA has strong potential to serve as a vaccine candidate against both H5 and H7 subtypes of influenza viruses.

Whole-Cell Vaccine Preparation: Options and Perspectives

Vaccines are biological preparations to elicit a specific immune response in individuals against the targetted microorganisms. The use of vaccines has caused the near eradication of many critical diseases and has had an everlasting impact on public health at a relatively low cost. Most of the vaccines developed today are based on techniques which were developed a long time ago. In the beginning, vaccines were prepared from tissue fluids obtained from infected animals or people, but at present, the scenario has changed with the development of vaccines from live or killed whole microorganisms and toxins or using genetic engineering approaches. Considerable efforts have been made in vaccine development, but there are still many diseases that need attention, and new technologies are being developed in vaccinology to combat them. In this chapter, we discuss different approaches for vaccine development, including the properties and preparation of whole-cell vaccines.

Polymeric paint coated common-touch surfaces that can kill bacteria, fungi and influenza virus

In the current situation of COVID-19 pandemic, the role of surfaces in transmitting pathogens is clearer than ever. Herein, we report an organo-soluble, quaternary antimicrobial paint (QAP) based on polyethyleneimine (PEI) which was coated on a wide range of surfaces such as polyvinylchloride (PVC), nylon, rubber, aluminum. The coating completely killed drug-resistant bacteria. It showed rapid bactericidal properties with complete killing in 45 min of exposure and lowered bacterial adherence, asserting self-sterilizing nature. The coating exhibited complete killing of stationary phase cells of bacteria. The coating killed drug-resistant C. albicans strains. Importantly, QAP coating showed complete killing of influenza virus (H1N1).

Considerations for setting occupational exposure limits for novel pharmaceutical modalities

In order to develop new and effective medicines, pharmaceutical companies must be modality agnostic. As science reveals an enhanced understanding of biological processes, new therapeutic modalities are becoming important in developing breakthrough therapies to treat both rare and common diseases. As these new modalities progress, concern and uncertainty arise regarding their safe handling by the researchers developing them, employees manufacturing them and nurses administering them. This manuscript reviews the available literature for emerging modalities (including oligonucleotides, monoclonal antibodies, fusion proteins and bispecific antibodies, antibody-drug conjugates, peptides, vaccines, genetically modified organisms, and several others) and provides considerations for occupational health and safety-oriented hazard identification and risk assessments to enable timely, consistent and well-informed hazard identification, hazard communication and risk-management decisions. This manuscript also points out instances where historical exposure control banding systems may not be applicable (e.g. oncolytic viruses, biologics) and where other occupational exposure limit systems are more applicable (e.g. Biosafety Levels, Biologic Control Categories).

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Review of toxicology and pharmacology information for novel therapeutic modalities.

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Identification of occupational hazards associated with novel therapeutic modalities.

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Occupational hazards and exposure risks differ across pharmaceutical modalities.

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Occupational exposure control banding systems are not one size fits all.

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Banding system variations offer benefits while enabling proper exposure controls.

Immunological considerations for COVID-19 vaccine strategies

The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the most formidable challenge to humanity in a century. It is widely believed that prepandemic normalcy will never return until a safe and effective vaccine strategy becomes available and a global vaccination programme is implemented successfully. Here, we discuss the immunological principles that need to be taken into consideration in the development of COVID-19 vaccine strategies. On the basis of these principles, we examine the current COVID-19 vaccine candidates, their strengths and potential shortfalls, and make inferences about their chances of success. Finally, we discuss the scientific and practical challenges that will be faced in the process of developing a successful vaccine and the ways in which COVID-19 vaccine strategies may evolve over the next few years.

Cell-Based Influenza A/H1N1pdm09 Vaccine Viruses Containing Chimeric Hemagglutinin with Improved Membrane Fusion Ability

The H1N1 influenza pandemic vaccine has been developed from the A/California/07/09 (Cal) virus and the well-known high-yield A/Puerto Rico/8/34 (PR8) virus by classical reassortment and reverse genetics (RG) in eggs. Previous studies have suggested that Cal-derived chimeric hemagglutinin (HA) and neuraminidase (NA) improve virus yields. However, the cell-based vaccine of the H1N1 pandemic virus has been less investigated. RG viruses that contained Cal-derived chimeric HA and NA could be rescued in Madin-Darby canine kidney cells that expressed α2,6-sialyltransferase (MDCK-SIAT1). The viral growth kinetics and chimeric HA and NA properties were analyzed. We attempted to generate various RG viruses that contained Cal-derived chimeric HA and NA, but half of them could not be rescued in MDCK-SIAT1 cells. When both the 3'- and 5'-terminal regions of Cal HA viral RNA were replaced with the corresponding regions of PR8 HA, the RG viruses were rescued. Our results were largely consistent with those of previous studies, in which the N- and C-terminal chimeric HA slightly improved virus yield. Importantly, the chimeric HA, compared to Cal HA, showed cell fusion ability at a broader pH range, likely due to amino acid substitutions in the transmembrane region of HA. The rescued RG virus with high virus yield harbored the chimeric HA capable of cell fusion at a broader range of pH.

A ligation and restriction enzyme independent cloning technique: an alternative to conventional methods for cloning hard-to-clone gene segments in the influenza reverse genetics system

BACKGROUND

Reverse genetics is used in many laboratories around the world and enables the creation of tailor-made influenza viruses with a desired genotype or phenotype. However, the process is not flawless, and difficulties remain during cloning of influenza gene segments into reverse genetics vectors (pHW2000, pHH21, pCAGGS). Reverse genetics begins with making cDNA copies of influenza gene segments and cloning them into bi-directional (pHW2000) or uni-directional plasmids (pHH21, pCAGGS) followed by transfection of the recombinant plasmid(s) to HEK-293 T or any other suitable cells which are permissive to transfection. However, the presence of internal restriction sites in the gene segments of many field isolates of avian influenza viruses makes the cloning process difficult, if employing conventional methods. Further, the genetic instability of influenza gene-containing plasmids in bacteria (especially Polymerase Basic 2 and Polymerase Basic 1 genes; PB2 and PB1) also leads to erroneous incorporation of bacterial genomic sequences into the influenza gene of interest.

METHODS

Herein, we report an easy and efficient ligation and restriction enzyme independent (LREI) cloning method for cloning influenza gene segments into pHW2000 vector. The method involves amplification of megaprimers followed by PCR amplification of megaprimers using a bait plasmid, DpnI digestion and transformation.

RESULTS

Hard-to-clone genes: PB2 of A/chicken/Bangladesh/23527/2014 (H9N2) and PB1 of A/chicken/Bangladesh/23527/2014 (H9N2), A/chicken/Jiangxi/02.05YGYXG023-P/2015 (H5N6) and A/Chicken/Vietnam/H7F-14-BN4-315/2014 (H9N2) were cloned into pHW2000 using our LREI method and recombinant viruses were subsequently rescued.

CONCLUSION

The LREI cloning procedure represents an alternative strategy for cloning influenza gene segments which have internal restriction sites for the enzymes used in reverse genetics. Further, the problem of genetic instability in bacteria can be alleviated by growing recombinant bacterial cultures at a lower temperature. This technique can be applied to clone any influenza gene segment using universal primers, which would help in rapid generation of influenza viruses and facilitate influenza research and vaccine development.

Biosafety risk assessment for production of candidate vaccine viruses to protect humans from zoonotic highly pathogenic avian influenza viruses

A major lesson learned from the public health response to the 2009 H1N1 pandemic was the need to shorten the vaccine delivery timeline to achieve the best pandemic mitigation results. A gap analysis of previous pre-pandemic vaccine development activities identified possible changes in the Select Agent exclusion process that would maintain safety and shorten the timeline to develop candidate vaccine viruses (CVVs) for use in pandemic vaccine manufacture. Here, we review the biosafety characteristics of CVVs developed in the past 15 years to support a shortened preparedness timeline for A(H5) and A(H7) subtype highly pathogenic avian influenza (HPAI) CVVs. Extensive biosafety experimental evidence supported recent changes in the implementation of Select Agent regulations that eliminated the mandatory chicken pathotype testing requirements and expedited distribution of CVVs to shorten pre-pandemic and pandemic vaccine manufacturing by up to 3 weeks.

Subunit vaccines based on recombinant yeast protect against influenza A virus in a one-shot vaccination scheme

Here we report on new subunit vaccines based on recombinant yeast of the type Kluyveromyces lactis (K. lactis), which protect mice from a lethal influenza A virus infection. Applying a genetic system that enables the rapid generation of transgenic yeast, we have developed K. lactis strains that express the influenza A virus hemagglutinin, HA, either individually or in combination with the viral M1 matrix protein. Subcutaneous application of the inactivated, but otherwise non-processed yeast material shows a complete protection of BALB/c mice in prime/boost and even one-shot/single dose vaccination schemes against a subsequent, lethal challenge with the cognate influenza virus. The yeast vaccines induce titers of neutralizing antibodies that are readily comparable to those induced by an inactivated virus vaccine. These data suggest that HA and M1 are produced with a high antigenicity in the yeast cells. Based on these findings, multivalent, DIVA-capable, yeast-based subunit vaccines may be developed as promising alternatives to conventional virus-based anti-flu vaccines for veterinary applications.

Generation of highly productive and mammalian nonpathogenic recombinant H9N2 avian influenza viruses by optimization of 3'end promoter and NS genome

We developed A/PR/8/34 (PR8) virus-based reverse genetics system in which six internal genes of PR8 and attenuated hemagglutinin and intact neuraminidase genes of field avian influenza viruses (AIVs) have been used for the generation of highly productive recombinant vaccine strains. The 6 + 2 recombinant vaccine strains can induce protective humoral immunity against intended field AIVs; however, the epitopes of B and T cells encoded by internal genes may be important for heterosubtypic protection. Therefore, it is advantageous to use homologous internal genes of field AIVs for recombinant vaccine strains. However, the rescue of recombinant viruses having whole internal genes of field AIVs by the PR8-based reverse genetics system was unsuccessful in some cases. Although partial replacement of an internal gene has been successful for generation of highly productive and mammalian nonpathogenic recombinant viruses, complete replacement of internal genes may be more favorable. In this study, we successfully generated complete recombinant H9N2 AIVs possessing 8 genomes of H9N2 AIVs by optimal combinations of 3' end promoter sequences of polymerase genomes, and a NS genome. All the generated recombinant viruses showed highly productive and mammalian nonpathogenic traits but some of them showed much higher virus titers in embryonated chicken eggs. Additionally, we found the same mutations of NS1 gene determined pathogenicity of AIVs in chicken embryos as well as mammals. Thus, the 3' end promoter optimization, and highly productive and mammalian nonpathogenic internal genes may be useful to develop vaccines against AIVs.

Galectin-3 Enhances Avian H5N1 Influenza A Virus-Induced Pulmonary Inflammation by Promoting NLRP3 Inflammasome Activation

Highly pathogenic avian influenza A H5N1 virus causes pneumonia and acute respiratory distress syndrome in humans. Virus-induced excessive inflammatory response contributes to severe disease and high mortality rates. Galectin-3, a β-galactoside-binding protein widely distributed in immune and epithelial cells, regulates various immune functions and modulates microbial infections. Here, we describe galectin-3 up-regulation in mouse lung tissue after challenges with the H5N1 influenza virus. We investigated the effects of endogenous galectin-3 on H5N1 infection and found that survival of galectin-3 knockout (Gal-3KO) mice was comparable with wild-type (WT) mice after infections. Compared with infected WT mice, infected Gal-3KO mice exhibited less inflammation in the lungs and reduced IL-1β levels in bronchoalveolar lavage fluid. In addition, the bone marrow-derived macrophages (BMMs) from Gal-3KO mice exhibited reduced oligomerization of apoptosis-associated speck-like proteins containing caspase-associated recruitment domains and secreted less IL-1β compared with BMMs from WT mice. However, similar levels of the inflammasome component of nucleotide oligomerization domain-like receptor protein 3 (NLRP3) were observed in two genotypes of BMMs. Co-immunoprecipitation data indicated galectin-3 and NLRP3 interaction in BMMs infected with H5N1. An association was also observed between galectin-3 and NLRP3/apoptosis-associated speck-like proteins containing caspase-associated recruitment domain complex. Combined, our results suggest that endogenous galectin-3 enhances the effects of H5N1 infection by promoting host inflammatory responses and regulating IL-1β production by macrophages via interaction with NLRP3.

Evaluation of marker gene expression as a potential predictive marker of leukopenic toxicity for inactivated influenza vaccines

The leukopenic toxicity test (LTT) is used to evaluate the safety and lot-to-lot consistency of influenza hemagglutinin split vaccine (HAv) and is included in the Japanese Minimum Requirements for Biological Products. LTT assesses the reduced leukocyte levels in murine peripheral blood after HAv administration. However, they require large numbers of animals, and therefore it would be beneficial to develop a more accurate and sensitive alternative method. In this study, we selected biomarkers of leukocyte reduction from 18 previously identified marker genes that were associated with an abnormal toxicity test (ATT). Among these 18 genes, the expressions of 15 marker genes were strongly associated with leukocyte reduction levels. A stepwise single addition multiple regression analysis was used to further extract the genes responsible for leukocyte reduction, with significant (p < 0.25) regression coefficients. The expression of 7 genes significantly predicted the leukocyte reduction. The prediction accuracy of this approach was approximately >90% (mean) for the direct measurement of leukocyte numbers. These results indicate that the expression of these 18 previously identified genes can provide information for both ATT and LTT.

Generation of a Genetically Stable High-Fidelity Influenza Vaccine Strain

Vaccination is considered the most effective preventive means for influenza control. The development of a master virus with high growth and genetic stability, which may be used for the preparation of vaccine viruses by gene reassortment, is crucial for the enhancement of vaccine performance and efficiency of production. Here, we describe the generation of a high-fidelity and high-growth influenza vaccine master virus strain with a single V43I amino acid change in the PB1 polymerase of the high-growth A/Puerto Rico/8/1934 (PR8) master virus. The PB1-V43I mutation was introduced to increase replication fidelity in order to design an H1N1 vaccine strain with a low error rate. The PR8-PB1-V43I virus exhibited good replication compared with that of the parent PR8 virus. In order to compare the efficiency of egg adaptation and the occurrence of gene mutations leading to antigenic alterations, we constructed 6:2 genetic reassortant viruses between the A(H1N1)pdm09 and the PR8-PB1-V43I viruses; hemagglutinin (HA) and neuraminidase (NA) were from the A(H1N1)pdm09 virus, and the other genes were from the PR8 virus. Mutations responsible for egg adaptation mutations occurred in the HA of the PB1-V43I reassortant virus during serial egg passages; however, in contrast, antigenic mutations were introduced into the HA gene of the 6:2 reassortant virus possessing the wild-type PB1. This study shows that the mutant PR8 virus possessing the PB1 polymerase with the V43I substitution may be utilized as a master virus for the generation of high-growth vaccine viruses with high polymerase fidelity, low error rates of gene replication, and reduced antigenic diversity during virus propagation in eggs for vaccine production.IMPORTANCE Vaccination represents the most effective prophylactic option against influenza. The threat of emergence of influenza pandemics necessitates the ability to generate vaccine viruses rapidly. However, as the influenza virus exhibits a high mutation rate, vaccines must be updated to ensure a good match of the HA and NA antigens between the vaccine and the circulating strain. Here, we generated a genetically stable master virus of the A/Puerto Rico/8/1934 (H1N1) backbone encoding an engineered high-fidelity viral polymerase. Importantly, following the application of the high-fidelity PR8 backbone, no mutation resulting in antigenic change was introduced into the HA gene during propagation of the A(H1N1)pdm09 candidate vaccine virus. The low error rate of the present vaccine virus should decrease the risk of generating mutant viruses with increased virulence. Therefore, our findings are expected to be useful for the development of prepandemic vaccines and live attenuated vaccines with higher safety than that of the present candidate vaccines.

Tunable and label-free virus enrichment for ultrasensitive virus detection using carbon nanotube arrays

Viral infectious diseases can erupt unpredictably, spread rapidly, and ravage mass populations. Although established methods, such as polymerase chain reaction, virus isolation, and next-generation sequencing have been used to detect viruses, field samples with low virus count pose major challenges in virus surveillance and discovery. We report a unique carbon nanotube size-tunable enrichment microdevice (CNT-STEM) that efficiently enriches and concentrates viruses collected from field samples. The channel sidewall in the microdevice was made by growing arrays of vertically aligned nitrogen-doped multiwalled CNTs, where the intertubular distance between CNTs could be engineered in the range of 17 to 325 nm to accurately match the size of different viruses. The CNT-STEM significantly improves detection limits and virus isolation rates by at least 100 times. Using this device, we successfully identified an emerging avian influenza virus strain [A/duck/PA/02099/2012(H11N9)] and a novel virus strain (IBDV/turkey/PA/00924/14). Our unique method demonstrates the early detection of emerging viruses and the discovery of new viruses directly from field samples, thus creating a universal platform for effectively remediating viral infectious diseases.

Let microorganisms do the talking, let us talk more about microorganisms

Microorganisms are of uttermost importance, yet in the eyes of the general public they are often associated with dirt and diseases. At the same time, microbiologists have access to and comprehensive knowledge of just a tiny minority of the microbial diversity existing in nature. In this commentary, we present these issues of public misconception and scientific limitations and their possible consequences, and propose ways to overcome them. A particular interest is directed toward the secondary metabolism of filamentous fungi as well as novel outreach activities, including so-called “science slams” and interactions between the arts and the sciences, to raise awareness about the relevance of microorganisms.

Hemagglutinin amino acids related to receptor specificity could affect the protection efficacy of H5N1 and H7N9 avian influenza virus vaccines in mice

The continuous and sporadic human transmission of highly pathogenic avian H5N1 and H7N9 influenza viruses illustrates the urgent need for efficacious vaccines. However, all tested vaccines for the H5N1 and H7N9 viruses appear to be poorly immunogenic in mammals. In this study, a series of vaccines was produced using reverse genetic techniques that possess HA and NA genes from the H5N1 virus in the genetic background of the high-yield strain A/PR/8/34 (H1N1). Meanwhile, a group of H7N9 VLP vaccines that contain HA from H7N9 and NA and M1 from A/PR/8/34 (H1N1) was also produced. The HA amino acids of both the H5N1 and H7N9 vaccines differed at residues 226 and 228, both of which are critical for receptor specificity for an avian or mammalian host. Mice received two doses (3μg of HA each) of each vaccine and were challenged with lethal doses of wild type H5N1 or H7N9 viruses. The results showed that a recombinant H5N1 vaccine in which the HA amino acid G228 (avian specificity) was converted to S228 (mammalian specificity) resulted in higher HI titers, a lower viral titer in the lungs, and 100% protection in mice. However, a H7N9 VLP vaccine that contains L226 (mammalian specificity) and G228 (avian specificity) in HA showed better immunogenicity and protection efficacy in mice than VLP containing HA with either L226+S228 or Q226+S228. This observation indicated that specific HA residues could enhance a vaccine's protection efficacy and HA glycoproteins with both avian-type and human-type receptor specificities may produce better pandemic influenza vaccines for humans.

Propagation and Characterization of Influenza Virus Stocks That Lack High Levels of Defective Viral Genomes and Hemagglutinin Mutations

Influenza virus infections are responsible for more than 250,000 deaths annually. Influenza virus isolation, propagation, and characterization protocols are critical for completing reproducible basic research studies and for generating vaccine seed stocks. Detailed protocols for the isolation and identification of influenza virus have been recently reported (Eisfeld et al., 2014). However, there are few standardized protocols focused on the propagation and characterization of viral isolates, and as a result, viruses propagated in different conditions in different laboratories often have distinct in vitro and in vivo characteristics. Here, we focus on influenza A virus propagation and characterization in the laboratory taking into consideration the overall quality and composition of the virus stock to achieve consistency in virus yield, virulence, and immunostimulatory activity.

Intranasal vaccination with a plant-derived H5 HA vaccine protects mice and ferrets against highly pathogenic avian influenza virus challenge

Highly pathogenic avian influenza H5N1 infection remains a public health threat and vaccination is the best measure of limiting the impact of a potential pandemic. Mucosal vaccines have the advantage of eliciting immune responses at the site of viral entry, thereby preventing infection as well as further viral transmission. In this study, we assessed the protective efficacy of hemagglutinin (HA) from the A/Indonesia/05/05 (H5N1) strain of influenza virus that was produced by transient expression in plants. The plant-derived vaccine, in combination with the mucosal adjuvant (3′,5′)-cyclic dimeric guanylic acid (c-di-GMP) was used for intranasal immunization of mice and ferrets, before challenge with a lethal dose of the A/Indonesia/05/05 (H5N1) virus. Mice vaccinated with 15 μg or 5 μg of adjuvanted HA survived the viral challenge, while all control mice died within 10 d of challenge. Vaccinated animals elicited serum hemagglutination inhibition, IgG and IgA antibody titers. In the ferret challenge study, all animals vaccinated with the adjuvanted plant vaccine survived the lethal viral challenge, while 50% of the control animals died. In both the mouse and ferret models, the vaccinated animals were better protected from weight loss and body temperature changes associated with H5N1 infection compared with the non-vaccinated controls. Furthermore, the systemic spread of the virus was lower in the vaccinated animals compared with the controls. Results presented here suggest that the plant-produced HA-based influenza vaccine adjuvanted with c-di-GMP is a promising vaccine/adjuvant combination for the development of new mucosal influenza vaccines.

Single-cell analysis and stochastic modelling unveil large cell-to-cell variability in influenza A virus infection

Biochemical reactions are subject to stochastic fluctuations that can give rise to cell-to-cell variability. Yet, how this variability affects viral infections, which themselves involve noisy reactions, remains largely elusive. Here we present single-cell experiments and stochastic simulations that reveal a large heterogeneity between influenza A virus (IAV)-infected cells. In particular, experimental data show that progeny virus titres range from 1 to 970 plaque-forming units and intracellular viral RNA (vRNA) levels span three orders of magnitude. Moreover, the segmentation of IAV genomes seems to increase the susceptibility of their replication to noise, since the level of different genome segments can vary substantially within a cell. In addition, simulations suggest that the abortion of virus entry and random degradation of vRNAs can result in a large fraction of non-productive cells after single-hit infection. These results challenge current beliefs that cell population measurements and deterministic simulations are an accurate representation of viral infections.

The avian influenza vaccine Emerflu. Why did it fail?

Emerflu is an inactivated, split-virion pandemic preparedness vaccine, containing 30 μg of hemagglutinin (HA) and 600 μg of aluminum hydroxide adjuvant. It is administered in two doses, 3 weeks apart. Only moderate immunogenicity was evident from clinical studies with the vaccine in adults, and HA antibody responses were below the criteria established by the EMA and US FDA for licensure. With the exception of Australia, the vaccine remains unlicensed. Further clinical development appears to have been suspended, and newer adjuvants such as MF59 and AS03 have since demonstrated safety and superior immunogenicity with lower HA doses. Emerflu is symbolic of the failure of aluminum salts as an adjuvant for influenza vaccines. Reasons for this failure are unclear, and may reflect problems with the adjuvant-antigen complex or interference in the immune response by heterosubtypic immunity.

A single NS2 mutation of K86R promotes PR8 vaccine donor virus growth in Vero cells

Vaccination is the most effective way to prevent and control infection by influenza viruses, and a cell-culture-based vaccine production system is preferred as the future choice for the large-scale production of influenza vaccines. As one of the WHO-recommended cell lines for producing influenza vaccines, Vero cells do not efficiently support the growth of the current influenza A virus vaccine donor strain, the A/Puerto Rico/8/1934 (PR8) virus. In this study, a single mutation of K86R in the NS2 protein can sufficiently render the high-yielding property to the PR8 virus in Vero cells. Further analysis showed that the later steps in the virus replication cycle were accelerated by NS2(K86R) mutation, which may relate to an enhanced interaction between NS2(K86R) and the components of host factor F1Fo-ATPase, FoB and F1β. Because the NS2(K86R) mutation does not increase PR8 virulence in either mice or embryonated eggs, the PR8-NS2(K86R) virus could serve as a promising vaccine donor strain in Vero cells.

Design of alternative live attenuated influenza virus vaccines

Each year due to the ever-evolving nature of influenza, new influenza vaccines must be produced to provide protection against the influenza viruses in circulation. Currently, there are two mainstream strategies to generate seasonal influenza vaccines: inactivated and live-attenuated. Inactivated vaccines are non-replicating forms of whole influenza virus, while live-attenuated vaccines are viruses modified to be replication impaired. Although it is widely believed that by inducing both mucosal and humoral immune responses the live-attenuated vaccine provides better protection than that of the inactivated vaccine, there are large populations of individuals who cannot safely receive the LAIV vaccine. Thus, safer LAIV vaccines are needed to provide adequate protection to these populations. Improvement is also needed in the area of vaccine production. Current strategies relying on traditional tissue culture-based and egg-based methods are slow and delay production time. This chapter describes experimental vaccine generation and production strategies that address the deficiencies in current methods for potential human and agricultural use.

Evaluation of antibody response in mice against avian influenza A (H5N1) strain neuraminidase expressed in yeast Pichia pastoris

Avian influenza has raised many apprehension in the recent years because of its potential transmitability to humans. With the increasing emergence of drug-resistant avian influenza strains, development of potential vaccines are imperative to manage this disease. Two structural antigens, haemagglutinin and neuraminidase, have been the target candidates for the development of subunit vaccine against influenza. In an effort to develop a faster and economically beneficial vaccine, the neuraminidase gene of a highly pathogenic avian influenza isolate was cloned and expressed in the methylotrophic yeast Pichia pastoris. The recombinant neuraminidase (rNA) antigen was purified, and its bioactivity was analysed. The rNA was found to be functional, as determined by the neuraminidase assay. Four groups of mice were immunized with different concentrations of purified rNA antigen, which were adjuvanted with aluminium hydroxide. The immune response against rNA was analysed by enzyme-linked immunosorbent assay (ELISA) and neuraminidase inhibition assay. The mice groups immunized with 25 (mu) g and 10 (mu) g of antigen had a significant immune response against rNA. This method can be utilized for faster and cost-effective development of vaccines for a circulating and newer strain of avian influenza, and would aid in combating the disease in a pandemic situation, in which production time matters greatly.

Influenza gain-of-function experiments: their role in vaccine virus recommendation and pandemic preparedness

In recent years, controversy has arisen regarding the risks and benefits of certain types of gain-of-function (GOF) studies involving avian influenza viruses. In this article, we provide specific examples of how different types of data, including information garnered from GOF studies, have helped to shape the influenza vaccine production process-from selection of candidate vaccine viruses (CVVs) to the manufacture and stockpiling of safe, high-yield prepandemic vaccines for the global community. The article is not written to support a specific pro- or anti-GOF stance but rather to inform the scientific community about factors involved in vaccine virus selection and the preparation of prepandemic influenza vaccines and the impact that some GOF information has had on this process.

Surface modifications of influenza proteins upon virus inactivation by β-propiolactone

Inactivation of intact influenza viruses using formaldehyde or β-propiolactone (BPL) is essential for vaccine production and safety. The extent of chemical modifications of such reagents on viral proteins needs to be extensively investigated to better control the reactions and quality of vaccines. We have evaluated the effect of BPL inactivation on two candidate re-assortant vaccines (NIBRG-121xp and NYMC-X181A) derived from A/California/07/2009 pandemic influenza viruses using high-resolution FT-ICR MS-based proteomic approaches. We report here an ultra performance LC MS/MS method for determining full-length protein sequences of hemagglutinin and neuraminidase through protein delipidation, various enzymatic digestions, and subsequent mass spectrometric analyses of the proteolytic peptides. We also demonstrate the ability to reliably identify hundreds of unique sites modified by propiolactone on the surface of glycoprotein antigens. The location of these modifications correlated with changes to protein folding, conformation, and stability, but demonstrated no effect on protein disulfide linkages. In some cases, these modifications resulted in suppression of protein function, an effect that correlated with the degree of change of the modified amino acids' side chain length and polarity.

All-in-one bacmids: an efficient reverse genetics strategy for influenza A virus vaccines

Vaccination is the first line of defense against influenza virus infection, yet influenza vaccine production methods are slow, antiquated, and expensive as a means to effectively reduce the virus burden during epidemic or pandemic periods. There is a great need for alternative influenza vaccines and vaccination methods with a global scale of impact. We demonstrate here a strategy to generate influenza A virus in vivo by using bacmid DNAs. Compared to the classical reverse genetics system, the "eight-in-one" bacmids (bcmd-RGFlu) showed higher efficiency of virus rescue in various cell types. Using a transfection-based inoculation (TBI) system, intranasal delivery to DBA/2J and BALB/c mice of bcmd-RGFlu plus 293T cells led to the generation of lethal PR8 virus in vivo. A prime-boost intranasal vaccination strategy using TBI in the context of a bcmd-RGFlu carrying a temperature-sensitive H1N1 virus resulted in protection of mice against lethal challenge with the PR8 strain. Taken together, these studies provide proof of principle to highlight the potential of vaccination against influenza virus by using in vivo reverse genetics.

IMPORTANCE

Vaccination is the first line of defense against influenza virus infections. A major drawback in the preparation of influenza vaccines is that production relies on a heavily time-consuming process of growing the viruses in eggs. We propose a radical change in the way influenza vaccination is approached, in which a recombinant bacmid, a shuttle vector that can be propagated in both Escherichia coli and insect cells, carries an influenza virus infectious clone (bcmd-RGFlu). Using a surrogate cell system, we found that intranasal delivery of bcmd-RGFlu resulted in generation of influenza virus in mice. Furthermore, mice vaccinated with this system were protected against lethal influenza virus challenge. The study serves as a proof of principle of a potentially universal vaccine platform against influenza virus and other pathogens.

Enhanced human receptor binding by H5 haemagglutinins

Mutant H5N1 influenza viruses have been isolated from humans that have increased human receptor avidity. We have compared the receptor binding properties of these mutants with those of wild-type viruses, and determined the structures of their haemagglutinins in complex with receptor analogues. Mutants from Vietnam bind tighter to human receptor by acquiring basic residues near the receptor binding site. They bind more weakly to avian receptor because they lack specific interactions between Asn-186 and Gln-226. In contrast, a double mutant, Δ133/Ile155Thr, isolated in Egypt has greater avidity for human receptor while retaining wild-type avidity for avian receptor. Despite these increases in human receptor binding, none of the mutants prefers human receptor, unlike aerosol transmissible H5N1 viruses. Nevertheless, mutants with high avidity for both human and avian receptors may be intermediates in the evolution of H5N1 viruses that could infect both humans and poultry.

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H5N1 influenza virus binding.

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Haemagglutinin receptor specificity using biolayer interferometry.

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Haemagglutinin receptor complex crystal structure determination.

Expression of avian influenza virus (H5N1) hemagglutinin and matrix protein 1 in Pichia pastoris and evaluation of their immunogenicity in mice

The conventional avian influenza vaccines rely on development of neutralizing antibodies against the HA and NA antigens. However, these antigens are highly variable, and hence there is a need for better vaccine candidates which would offer broader protection in animals. The M1 of avian influenza is another major structural protein that has conserved epitopes that are reported to induce CD8+ T cells and can contribute to protection against morbidity and mortality from influenza. Hence in an effort to study the immune response of rM1 either alone or in combination with rHA, the hemagglutinin (HA) and matrix protein (M1) of A/Hatay/2004/H5N1 strain of avian influenza were expressed in Pichia pastoris as his-tagged proteins and purified through Ni-NTA chromatography. The His-tag was removed using TEV protease cleavage site and the immunogenicity of purified rHA and rM1 either alone or in combination was determined in mice. One group of mice was immunized with 5 μg of purified rHA, the other group was immunized with rM1, and a third group of mice were immunized with 5 μg of rHA and rM1. All the animals were boosted twice, once on 28 days postimmunization (dpi) and the second on 42 dpi. The immune response was evaluated by enzyme-linked immunosorbent assay (ELISA) and hemagglutination inhibition (HI) assay. The group of mice immunized with rHA and rM1 together showed significantly higher immune response against rHA and rM1 than mice immunized with either HA or M1 antigens. The addition of rM1 with rHA resulted in increased HI titer in animals immunized with both the antigens. These results suggest that the HA and M1 expressed in P. pastoris can be utilized in combination for the development of faster and cost-effective vaccines for circulating and newer strains of avian influenza and would aid in combating the disease in a pandemic situation, in which production time matters greatly.

Avian influenza vaccines against H5N1 'bird flu'

H5N1 avian influenza viruses (AIVs) have spread widely to more than 60 countries spanning three continents. To control the disease, vaccination of poultry is implemented in many of the affected countries, especially in those where H5N1 viruses have become enzootic in poultry and wild birds. Recently, considerable progress has been made toward the development of novel avian influenza (AI) vaccines, especially recombinant virus vector vaccines and DNA vaccines. Here, we will discuss the recent advances in vaccine development and use against H5N1 AIV in poultry. Understanding the properties of the available, novel vaccines will allow for the establishment of rational vaccination protocols, which in turn will help the effective control and prevention of H5N1 AI.

Prevention and Control of Influenza Viruses

The 2003–2004 outbreaks of highly pathogenic avian influenza (HPAI) have proven to be disastrous to the regional poultry industry in Asia, and have raised serious worldwide public health apprehension regarding the steps that should be taken to urgently control HPAI. Control measures must be taken based on the principles of biosecurity and disease management and at the same time making public aware of the precautionary measures at the verge of outbreak. Creation of protection and surveillance zones, various vaccination strategies viz. routine, preventive, emergency, mass and targeted vaccination programmes using live, inactivated and recombinant vaccines are the common strategies adopted in different parts of the globe. The new generation vaccines include recombinant vaccines and recombinant fusion vaccine. The pro-poor disease control programmes, giving compensation and subsidies to the farmers along with effective and efficient Veterinary Services forms integral part of control of HPAI. Following biosecurity principles and vaccination forms integral part of control programme against swine and equine influenza as well. Use of neuraminidase (NA) inhibitors (Zanamivir and Oseltamivir) for the treatment of human influenza has been widely accepted worldwide. The threat of increasing resistance of the flu viruses to these antivirals has evoked interest in the development of novel antiviral drugs for influenza virus such as inhibitors of cellular factors and host signalling cascades, cellular miRNAs, siRNA and innate immune peptides (defensins and cathelicidins). Commercial licensed inactivated vaccines for humans against influenza A and B viruses are available consisting of three influenza viruses: influenza type A subtype H3N2, influenza type A subtype H1N1 (seasonal) virus strain and influenza type B virus strain. As per WHO, use of tetravaccine consisting of antigens of influenza virus serotypes H3N2, H1N1, B and H5 is the most promising method to control influenza pandemic. All healthy children in many countries are required to be vaccinated between 6 and 59 months of age. The seasonal vaccines currently used in humans induce strain-specific humoral immunity as the antibodies. Universal influenza virus vaccines containing the relatively conserved ectodomain of M2 (M2e), M1, HA fusion peptide and stalk domains, NA, NP alone or in combination have been developed which have been shown to induce cross-protection. The T cell-based vaccines are another recent experimental approach that has been shown to elicit broad-spectrum heterosubtypic immunity in the host. As far as HPAI is concerned, various pandemic preparedness strategies have been documented.

Changes in the hemagglutinin of H5N1 viruses during human infection--influence on receptor binding

As avian influenza A(H5N1) viruses continue to circulate in Asia and Africa, global concerns of an imminent pandemic persist. Recent experimental studies suggest that efficient transmission between humans of current H5N1 viruses only requires a few genetic changes. An essential step is alteration of the virus hemagglutinin from preferential binding to avian receptors for the recognition of human receptors present in the upper airway. We have identified receptor-binding changes which emerged during H5N1 infection of humans, due to single amino acid substitutions, Ala134Val and Ile151Phe, in the hemagglutinin. Detailed biological, receptor-binding, and structural analyses revealed reduced binding of the mutated viruses to avian-like receptors, but without commensurate increased binding to the human-like receptors investigated, possibly reflecting a receptor-binding phenotype intermediate in adaptation to more human-like characteristics. These observations emphasize that evolution in nature of avian H5N1 viruses to efficient binding of human receptors is a complex multistep process.

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Changes in receptor binding of HA during H5N1 human infection were identified.

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Single A134V and L151F substitutions caused reduced affinity for avian receptors.

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Glycan array analyses were used to identify changes in receptor binding specificity.

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Structural basis for altered receptor binding was examined by X-ray crystallography.

Subtyping animal influenza virus with general multiplex RT-PCR and Liquichip high throughput (GMPLex)

This study developed a multiplex RT-PCR integrated with luminex technology to rapidly subtype simultaneously multiple influenza viruses. Primers and probes were designed to amplify NS and M genes of influenza A viruses HA gene of H1, H3, H5, H7, H9 subtypes, and NA gene of the N1 and N2 subtypes. Universal super primers were introduced to establish a multiplex RT-PCR (GM RT-PCR). It included three stages of RT-PCR amplification, and then the RT-PCR products were further tested by LiquiChip probe, combined to give an influenza virus (IV) rapid high throughput subtyping test, designated as GMPLex. The IV GMPLex rapid high throughput subtyping test presents the following features: high throughput, able to determine the subtypes of 9 target genes in H1, H3, H5, H7, H9, N1, and N2 subtypes of the influenza A virus at one time; rapid, completing the influenza subtyping within 6 hours; high specificity, ensured the specificity of the different subtypes by using two nested degenerate primers and one probe, no cross reaction occurring between the subtypes, no non-specific reactions with other pathogens and high sensitivity. When used separately to detect the product of single GM RT-PCR for single H5 or N1 gene, the GMPLex test showed a sensitivity of 10⁻⁵(= 280ELD₅₀) forboth tests and the Luminex qualitative ratio results were 3.08 and 3.12, respectively. When used to detect the product of GM RT-PCR for H5N1 strain at the same time, both showed a sensitivity of 10⁻⁴(=2800 ELD₅₀). The GMPLex rapid high throughput subtyping test can satisfy the needs of influenza rapid testing.

Pre-clinical evaluation of a replication-competent recombinant adenovirus serotype 4 vaccine expressing influenza H5 hemagglutinin

BACKGROUND

Influenza virus remains a significant health and social concern in part because of newly emerging strains, such as avian H5N1 virus. We have developed a prototype H5N1 vaccine using a recombinant, replication-competent Adenovirus serotype 4 (Ad4) vector, derived from the U.S. military Ad4 vaccine strain, to express the hemagglutinin (HA) gene from A/Vietnam/1194/2004 influenza virus (Ad4-H5-Vtn). Our hypothesis is that a mucosally-delivered replicating Ad4-H5-Vtn recombinant vector will be safe and induce protective immunity against H5N1 influenza virus infection and disease pathogenesis.

METHODOLOGY/PRINCIPAL FINDINGS

The Ad4-H5-Vtn vaccine was designed with a partial deletion of the E3 region of Ad4 to accommodate the influenza HA gene. Replication and growth kinetics of the vaccine virus in multiple human cell lines indicated that the vaccine virus is attenuated relative to the wild type virus. Expression of the HA transgene in infected cells was documented by flow cytometry, western blot analysis and induction of HA-specific antibody and cellular immune responses in mice. Of particular note, mice immunized intranasally with the Ad4-H5-Vtn vaccine were protected against lethal H5N1 reassortant viral challenge even in the presence of pre-existing immunity to the Ad4 wild type virus.

CONCLUSIONS/SIGNIFICANCE

Several non-clinical attributes of this vaccine including safety, induction of HA-specific humoral and cellular immunity, and efficacy were demonstrated using an animal model to support Phase 1 clinical trial evaluation of this new vaccine.

Structural vaccinology: structure-based design of influenza A virus hemagglutinin subtype-specific subunit vaccines

There is a great need for new vaccine development against influenza A viruses due to the drawbacks of traditional vaccines that are mainly prepared using embryonated eggs. The main component of the current split influenza A virus vaccine is viral hemagglutinin (HA) which induces a strong antibody-mediated immune response. To develop a modern vaccine against influenza A viruses, the current research has been focused on the universal vaccines targeting viral M2, NP and HA proteins. Crystallographic studies have shown that HA forms a trimer embedded on the viral envelope surface, and each monomer consists of a globular head (HA1) and a "rod-like" stalk region (HA2), the latter being more conserved among different HA subtypes and being the primary target for universal vaccines. In this study, we rationally designed the HA head based on the crystal structure of the 2009-pandemic influenza A (H1N1) virus HA as a model, tested its immunogenicity in mice, solved its crystal structure and further examined its immunological characteristics. The results show that the HA globular head can be easily prepared by in vitro refolding in an E. coli expression system, which maintains its intact structure and allows for the stimulation of a strong immune response. Together with recent reports on some similar HA globular head preparations we conclude that structure-based rational design of the HA globular head can be used for subtype-specific vaccines against influenza viruses.

Enhanced growth of influenza vaccine seed viruses in vero cells mediated by broadening the optimal pH range for virus membrane fusion

Vaccination is one of the most effective preventive measures to combat influenza. Prospectively, cell culture-based influenza vaccines play an important role for robust vaccine production in both normal settings and urgent situations, such as during the 2009 pandemic. African green monkey Vero cells are recommended by the World Health Organization as a safe substrate for influenza vaccine production for human use. However, the growth of influenza vaccine seed viruses is occasionally suboptimal in Vero cells, which places limitations on their usefulness for enhanced vaccine production. Here, we present a strategy for the development of vaccine seed viruses with enhanced growth in Vero cells by changing an amino acid residue in the stem region of the HA2 subunit of the hemagglutinin (HA) molecule. This mutation optimized the pH for HA-mediated membrane fusion in Vero cells and enhanced virus growth 100 to 1,000 times in the cell line, providing a promising strategy for cell culture-based influenza vaccines.

Evaluation of the sublingual route for administration of influenza H5N1 virosomes in combination with the bacterial second messenger c-di-GMP

Avian influenza A H5N1 is a virus with pandemic potential. Mucosal vaccines are attractive as they have the potential to block viruses at the site of entry, thereby preventing both disease and further transmission. The intranasal route is safe for the administration of seasonal live-attenuated influenza vaccines, but may be less suitable for administration of pandemic vaccines. Research into novel mucosal routes is therefore needed. In this study, a murine model was used to compare sublingual administration with intranasal and intramuscular administration of influenza H5N1 virosomes (2 µg haemagglutinin; HA) in combination with the mucosal adjuvant (3′,5′)-cyclic dimeric guanylic acid (c-di-GMP). We found that sublingual immunisation effectively induced local and systemic H5N1-specific humoral and cellular immune responses but that the magnitude of response was lower than after intranasal administration. However, both the mucosal routes were superior to intramuscular immunisation for induction of local humoral and systemic cellular immune responses including high frequencies of splenic H5N1-specific multifunctional (IL-2⁺TNF-α⁺) CD4⁺ T cells. The c-di-GMP adjuvanted vaccine elicited systemic haemagglutination inhibition (HI) antibody responses (geometric mean titres ≥40) both when administered sublingually, intranasally and inramuscularly. In addition, salivary HI antibodies were elicited by mucosal, but not intramuscular vaccination. We conclude that the sublingual route is an attractive alternative for administration of pandemic influenza vaccines.