Cross-Protective Immune Responses Elicited by Live Attenuated Influenza Vaccines

The desired effect of vaccination is to elicit protective immune responses against infection with pathogenic agents. An inactivated influenza vaccine is able to induce the neutralizing antibodies directed primarily against two surface antigens, hemagglutinin and neuraminidase. These two antigens undergo frequent antigenic drift and hence necessitate the annual update of a new vaccine strain. Besides the antigenic drift, the unpredictable emergence of the pandemic influenza strain, as seen in the 2009 pandemic H1N1, underscores the development of a new influenza vaccine that elicits broadly protective immunity against the diverse influenza strains. Cold-adapted live attenuated influenza vaccines (CAIVs) are advocated as a more appropriate strategy for cross-protection than inactivated vaccines and extensive studies have been conducted to address the issues in animal models. Here, we briefly describe experimental and clinical evidence for cross-protection by the CAIVs against antigenically distant strains and discuss possible explanations for cross-protective immune responses afforded by CAIVs. Potential barriers to the achievement of a universal influenza vaccine are also discussed, which will provide useful guidelines for future research on designing an ideal influenza vaccine with broad protection without causing pathogenic effects such as autoimmunity or attrition of protective immunity against homologous infection.

Toward a universal influenza vaccine: from the perspective of protective efficacy

No abstract available.

Principles underlying rational design of live attenuated influenza vaccines

Despite recent innovative advances in molecular virology and the developments of vaccines, influenza virus remains a serious burden for human health. Vaccination has been considered a primary countermeasure for prevention of influenza infection. Live attenuated influenza vaccines (LAIVs) are particularly attracting attention as an effective strategy due to several advantages over inactivated vaccines. Cold-adaptation, as a classical means for attenuating viral virulence, has been successfully used for generating safe and effective donor strains of LAIVs against seasonal epidemics and occasional pandemics. Recently, the advent of reverse genetics technique expedited a variety of rational strategies to broaden the pool of LAIVs. Considering the breadth of antigenic diversity of influenza virus, the pool of LAIVs is likely to equip us with better options for controlling influenza pandemics. With a brief reflection on classical attenuating strategies used at the initial stage of development of LAIVs, especially on the principles underlying the development of cold-adapted LAIVs, we further discuss and outline other attenuation strategies especially with respect to the rationales for attenuation, and their practicality for mass production. Finally, we propose important considerations for a rational vaccine design, which will provide us with practical guidelines for improving the safety and effectiveness of LAIVs.

Recombinant influenza viruses as delivery vectors for hepatis B virus epitopes

PURPOSE: Neuraminidase (NA) of influenza virus contains stalk region that shows a great deal of variability in both amino acid sequence and length. In this paper, we investigated generation of recombinant influenza viruses that had hepatitis B virus (HBV) B cell epitopes in the NA stalk region as a dual vaccine candidate. MATERIALS AND METHODS: We used the WSH-HK reassortant helper virus for rescue of recombinant influenza virus containing HBV epitopes and reverse genetic protocol based on the use of micrococcal nuclease-treated virus cores for reconstitution of ribonucleoproteins. RESULTS: We successfully generated a chimeric influenza viruses which contained 22 amino acid peptides in the stalk region derived from the surface and pre-surface protein HBV. The growth kinetics of the recombinant viruses was investigated after infection of Madin-Darby canine kidney (MDCK) and Madin-Darby bovine kidney (MDBK) cells and the rIV-BVPreS virus showed higher titer than other viruses in MDCK cells. We also confirmed the presence of HBV epitopes in the chimeric viruses by enzyme-linked immunosorbent assay (ELISA) using anti-HBV polyclonal antibody. When the ratio of recombinant virus verse wild type virus was calculated by ELISA, recombinant viruses exhibited 2 fold higher values than the wild type virus. CONCLUSION: These results suggest that chimeric influenza virus which contained foreign antigens can be used as dual vaccine against both HBV and influenza viruses.

Reverse genetic platform for inactivated and live-attenuated influenza vaccine

Influenza vaccine strains have been traditionally developed by annual reassortment between vaccine donor strain and the epidemic virulent strains. The classical method requires screening and genotyping of the vaccine strain among various reassortant viruses, which are usually laborious and time-consuming. Here we developed an efficient reverse genetic system to generate the 6:2 reassortant vaccine virus from cDNAs derived from the influenza RNAs. Thus, cDNAs of the two RNAs coding for surface antigens, haemagglutinin and neuraminidase from the epidemic virus and the 6 internal genes from the donor strain were transfected into cells and the infectious viruses of 6:2 defined RNA ratio were rescued. X-31 virus (a high-growth virus in embryonated eggs) and its cold-adapted strain X-31 ca were judiciously chosen as donor strains for the generation of inactivated vaccine and live-attenuated vaccine, respectively. The growth properties of these recombinant viruses in embryonated chicken eggs and MDCK cell were indistinguishable as compared to those generated by classical reassortment process. Based on the reverse genetic system, we generated 6 + 2 reassortant avian influenza vaccine strains corresponding to the A/Chicken/Korea/MS96 (H9N2) and A/Indonesia/5/2005 (H5N1). The results would serve as technical platform for the generation of both injectable inactivated vaccine and the nasal spray live attenuated vaccine for the prevention of influenza epidemics and pandemics.

Control of Avian Influenza: Calls for International Collaboration / 한국역학회지

The 1918 "Spanish Flu", cause of the largest causality rate ever recorded in human history with 50 million deaths, is genetically related to the current H5N1 virus, suggesting the potential emergence of H5N1 influenza as the next pandemic wave. In the process of co-infection and genetic reassortment of human and H5N1 avian influenza, the H5N1 strain could acquire human viral gene(s) to ignite the human to human spread, as occurred in 1957 and 1976 pandemics. All countries are vulnerable to infection as no effective vaccine has yet been developed for avian influenza. Once developed into a pandemic, the socio-economic impact of avian influenza would be enormous. In response to this danger, Korea recently proposed to establish an international consortium, the Pandemic Influenza Consortium, Korea (PICK), to emphasize close collaboration, especially among Pacific Rim countries. PICK proposes to support the following three areas: 1) international efforts in the implementation of national and regional preparedness plans through the development of epidemiological, microbiological and clinical tools and mechanisms for early detection of pandemic influenza epidemics, 2) the development and clinical evaluation of pandemic influenza candidate vaccine, and 3) the establishment of appropriate mechanisms to ensure the capacity to produce, the availability of supply, and the rational distribution of pandemic influenza vaccines to countries suffering from or at high risk of experiencing outbreaks. Finally, the effort is expected to serve as a basis for initiating, establishing and strengthening the international infrastructure for investigation of the infection mechanism and devising prophylactic and therapeutic responses to various infectious diseases.

Detection and Quantification of Residual Cellular DNA in the Production of Recombinant HPV-16 L1 Virus-Like Particles

A number of recombinant proteins isolated from cell sources are being produced for biopharmaceuticals. Although most biopharmaceuticals are highly purified, there is a safety concern that such recombinant products could be contaminated with impurities including adventitious virus, mycoplasma, endotoxin and oncogenic DNA. Residual DNA in recombinant biopharmaceuticals is a potential risk factor and must be evaluated and removed to meet the regulatory guidelines. Recombinant HPV type 16 L1 VLPs, recombinant protein produced in Spodoptera frugiperda (Sf) 9 insect cells, is a HPV subunit vaccine candidate which has been studied as a preventive vaccine of cervical cancers. In this study, we performed detection and quantification of residual cellular DNA in the production of recombinant HPV type 16 L1 VLPs. HPV-16 L1 VLPs were purified by processes including detergent lysis, sonication treatment, sucrose cushion centrifugation, CsCl equilibrium density centrifugation, and DNase treatment which was added to inactivate residual cellular DNA after CsCl centrifugation step. We have developed a precise assay based on a dot-blot hybridization using digoxigenin random primed labeling DNA probes for the detection and quantification of residual cellular DNA during the purification process and final products. Detection limit of residual cellular DNA was 0.1 ng in this assay and the amount of residual cellular DNA in the final product was 0.5 ng~1 ng per 100 microgram of protein. This study describes safer and more sensitive methods alternative to radioactive techniques employed for residual cellular DNA quantification of biopharmaceuticals produced by recombinant protein technology and presents method validation data demonstrating precision and reproducibility.

Control of Influenza:Development of Live Vaccine / 감염과화학요법

Although trivalent subunit vaccine has been available, the influenza vaccine has been under-utilized because of cumbersome route of vaccination and low level of protection. Therefore, there has always been a great need to develop live attenuated influenza vaccine which can be administered through nasal route and elicit better immunogenicity. Through conventional repeated passage at low temperature, a live influenza vaccine carrier could be established. By reassortant formation between the 'cold- adapted' vaccine carrier and virulent strains, a prototype of trivalent live influenza vaccine is developed. Influenza A virus was adapted to replicate at low temperature. Serial passage at progressively lower temperature (30degrees C, 27degrees C and 24degrees C)resulted in the generation of cold-adapted (ca), temperature-sensitive (ts) mutant and attenuation (att) phenotype. This strain was evaluated for their ability to protect mice from challenge with same subtype and different subtype of influenza A virus. The study showed that vaccination of mice with live attenuated influenza virus provided complete protection against homologous and heterologous virus challenge. We also evaluated therapeutic potential of ca influenza virus. The mice infected with ca virus before challenge with wild type viruses or infected with simultaneously showed reduced clinical symptoms suggesting potential therapeutic effects.

Control of Influenza:Development of Live Vaccine / 감염과화학요법

Although trivalent subunit vaccine has been available, the influenza vaccine has been under-utilized because of cumbersome route of vaccination and low level of protection. Therefore, there has always been a great need to develop live attenuated influenza vaccine which can be administered through nasal route and elicit better immunogenicity. Through conventional repeated passage at low temperature, a live influenza vaccine carrier could be established. By reassortant formation between the 'cold- adapted' vaccine carrier and virulent strains, a prototype of trivalent live influenza vaccine is developed. Influenza A virus was adapted to replicate at low temperature. Serial passage at progressively lower temperature (30degrees C, 27degrees C and 24degrees C)resulted in the generation of cold-adapted (ca), temperature-sensitive (ts) mutant and attenuation (att) phenotype. This strain was evaluated for their ability to protect mice from challenge with same subtype and different subtype of influenza A virus. The study showed that vaccination of mice with live attenuated influenza virus provided complete protection against homologous and heterologous virus challenge. We also evaluated therapeutic potential of ca influenza virus. The mice infected with ca virus before challenge with wild type viruses or infected with simultaneously showed reduced clinical symptoms suggesting potential therapeutic effects.