Live attenuated influenza vaccine tetravalent: a clinical review

The Screening and Mechanism of Influenza-Virus Sensitive MDCK Cell Lines for Influenza Vaccine Production

Influenza is a potentially fatal acute respiratory viral disease caused by the influenza virus. Influenza viruses vary in antigenicity and spread rapidly, resulting in seasonal epidemics. Vaccination is the most effective strategy for lowering the incidence and fatality rates of influenza-related disorders, and it is also an important method for reducing seasonal influenza infections. Mammalian Madin-Darby canine kidney (MDCK) cell lines are recommended for influenza virus growth, and such cell lines have been utilized in several commercial influenza vaccine productions. The limit dilution approach was used to screen ATCC-MDCK cell line subcellular strains that are especially sensitive to H1N1, H3N2, BV, and BY influenza viruses to increase virus production, and research on influenza virus culture media was performed to support influenza virus vaccine development. We also used RNA sequencing to identify differentially expressed genes and a GSEA analysis to determine the biological mechanisms underlying the various levels of susceptibility of cells to influenza viruses. MDCK cell subline 2B6 can be cultured to increase titer and the production of the H1N1, H3N2, BV, and BY influenza viruses. MDCK-2B6 has a significantly enriched and activated in ECM receptor interaction, JAK-STAT signaling, and cytokine receptor interaction signaling pathways, which may result in increased cellular susceptibility and cell proliferation activity to influenza viruses, promote viral adsorption and replication, and elevate viral production, ultimately. The study revealed that MDCK-2B6 can increase the influenza virus titer and yield in vaccine production by increasing cell sensitivity and enhancing proliferative activity.

MiRNA Targeted NP Genome of Live Attenuated Influenza Vaccines Provide Cross-Protection against a Lethal Influenza Virus Infection

The miRNA-based strategy has been used to develop live attenuated influenza vaccines. In this study, the nucleoprotein (NP) genome segment of the influenza virus was inserted by different perfect miRNA-192-5p target sites, and the virus was rescued by standard reverse genetics method, so as to verify the virulence and protective efficacy of live attenuated vaccine in cells and mice. The results showed there was no significant attenuation in 192t virus with one perfect miRNA-192-5p target site, and 192t-3 virus with three perfect miRNA target sites. However, 192t-6 virus with 6 perfect miRNA target sites and 192t-9 virus with 9 perfect miRNA target sites were both significantly attenuated after infection, and their virulence were similar to that of temperature-sensitive (TS) influenza A virus (IAV) which is a temperature-sensitive live attenuated influenza vaccine. Mice were immunized with different doses of 192t-6, 192t-9, and TS IAV. Four weeks after immunization, the IgG in serum and IgA in lung homogenate were increased in the 192t-6, 192t-9, and TS IAV groups, and the numbers of IFN-γ secreting splenocytes were also increased in a dose-dependent manner. Finally, 192t-6, and 192t-9 can protect the mice against the challenge of homologous PR8 H1N1 virus and heterosubtypic H3N2 influenza virus. MiRNA targeted viruses 192t-6 and 192t-9 were significantly attenuated and showed the same virulence as TS IAV and played a role in the cross-protection.

Development of a Stable Liquid Formulation for Live Attenuated Influenza Vaccine

Live attenuated influenza vaccine (LAIV) is considered one of the most effective vaccines and can be manufactured quickly and inexpensively to counter seasonal or pandemic influenza. Lyophilization is widely used in vaccine production. However, it requires a longer production cycle and large-scale equipment, thus posing a considerable financial burden for developing countries. A potential solution is the development of liquid LAIV, which can increase the yield and reduce the cost of production. In this study, influential factors of LAIV, such as potential stabilizing excipients and pH, were optimized by an orthogonal design. We found that pH is the most critical factor for the stability of LAIV; salt concentration and initial virus titer are also important for LAIV stability. With these data, we developed a liquid formulation consisting of 2.5% sucrose, 0.1% monosodium glutamate, 1% arginine, and 0.5% human serum albumin, with pH ranging from 6.2 to 6.9 (optimum pH 6.5-6.7), for optimal production of monovalent or trivalent LAIVs. This liquid formulation has the potential to considerably improve vaccine production capacity to compensate for the immense shortfall in influenza vaccines globally.

Rationale for vaccination with trivalent or quadrivalent live attenuated influenza vaccines: Protective vaccine efficacy in the ferret model

BACKGROUND AND AIM

The majority of seasonal influenza vaccines are trivalent, containing two A virus strains (H1N1 and H3N2) and one B virus strain. The co-circulation of two distinct lineages of B viruses can lead to mismatch between the influenza B virus strain recommended for the trivalent seasonal vaccine and the circulating B virus. This has led some manufacturers to produce quadrivalent influenza vaccines containing one strain from each B lineage in addition to H1N1 and H3N2 strains. However, it is also important to know whether vaccines containing a single influenza B strain can provide cross-protectivity against viruses of the antigenically distinct lineage. The aim of this study was to assess in naïve ferrets the potential cross-protective activity of trivalent live attenuated influenza vaccine (T-LAIV) against challenge with a heterologous wild-type influenza B virus belonging to the genetically different lineage and to compare this activity with effectiveness of quadrivalent LAIV (Q-LAIV) in the ferret model.

METHODS AND RESULTS

Ferrets were vaccinated with either one dose of trivalent LAIV containing B/Victoria or B/Yamagata lineage virus, or quadrivalent LAIV (containing both B lineages), or placebo. They were then challenged with B/Victoria or B/Yamagata lineage wild-type virus 28 days after vaccination. The ferrets were monitored for clinical signs and morbidity. Nasal swabs and lung tissue samples were analyzed for the presence of challenge virus. Antibody response to vaccination was assessed by routine hemagglutination inhibition assay. All LAIVs tested were found to be safe and effective against wild-type influenza B viruses based on clinical signs, and virological and histological data. The absence of interference between vaccine strains in trivalent and quadrivalent vaccine formulations was confirmed. Trivalent LAIVs were shown to have the potential to be cross-protective against infection with genetically different influenza B/Victoria and B/Yamagata lineages.

CONCLUSIONS

In this ferret model, quadrivalent vaccine provided higher protection to challenge against both B/Victoria and B/Yamagata lineage viruses. However, T-LAIV provided some cross-protection in the case of a mismatch between circulating and vaccine type B strains. Notably, B/Victoria-based T-LAIV was more protective compared to B/Yamagata-based T-LAIV.

Monoclonal antibody against N2 neuraminidase of cold adapted A/Leningrad/134/17/57 (H2N2) enables efficient generation of live attenuated influenza vaccines

Cold adapted influenza virus A/Leningrad/134/17/57 (H2N2) is a reliable master donor virus (Len/17-MDV) for preparing live attenuated influenza vaccines (LAIV). LAIVs are 6:2 reasortants that contain 6 segments of Len/17-MDV and the hemagglutinin (HA) and neuraminidase (NA) of contemporary circulating influenza A viruses. The problem with the classical reassortment procedure used to generate LAIVs is that there is limited selection pressure against NA of the Len/17-MDV resulting in 7:1 reassortants with desired HA only, which are not suitable LAIVs. The monoclonal antibodies (mAb) directed against the N2 of Len/17-MDV were generated. 10C4-8E7 mAb inhibits cell-to-cell spread of viruses containing the Len/17-MDV N2, but not viruses with the related N2 from contemporary H3N2 viruses. 10C4-8E7 antibody specifically inhibited the Len/17-MDV replication in vitro and in ovo but didn't inhibit replication of H3N2 or H1N1pdm09 reassortants. Our data demonstrate that addition of 10C4-8E7 in the classical reassortment improves efficiency of LAIV production.

Development and identification of a new Vero cell-based live attenuated influenza B vaccine by a modified classical reassortment method

BACKGROUND

It was to generate a new Vero and cold-adapted live attenuated influenza B vaccine with enough safety and immunogenicity.

METHODS

According to modified classical reassortment method, the donor strain was B/Yunnan/2/2005Vca(B), and the parental virus strain was B/Brisbane/60/2008wt. After co-infection in Vero cells, the prepared antibody serum inhibited the donor strain growth, and screening conditions inhibited the parental virus growth, which induced the growth of the new reassortant virus B/Brisbane/60/2008Vca(B) grow. Through intraperitoneal injection (i.j.) and intranasal injection (n.j.) we evaluated the safety and immunogenicity of the vaccine.

RESULTS

A high-yield of the reassortant virus was produced in Vero cells at 25°C, similar to the donor strains. After sequencing, it was found that B/Brisbane/60/2008Vca(B) Hemagglutinin (HA) and Neuraminidase (NA) gene fragments were from B/Brisbane/60/2008wt, while the other 6 gene fragments were from B/Yunnan/2/2005Vca(B). The n.j. immune pathway experiments showed no significant differences between the treatment and the PBS control group with respect to weight changes (P > 0.5). Furthermore, the new strain had a sufficient geometric mean titter (GMT) against B/Brisbane/60/2008wt.

CONCLUSION

The new reassortant live attenuated influenza B vaccine was safe and having enough immune stimulating ability.

Immunogenicity and Safety of Trivalent Split Influenza Vaccine in Healthy Korean Adults with Low Pre-Existing Antibody Levels: An Open Phase I Trial

PURPOSE

A phase I clinical trial was conducted to evaluate the immunogenicity and safety of newly developed egg-cultivated trivalent inactivated split influenza vaccine (TIV) in Korea.

MATERIALS AND METHODS

The TIV was administered to 43 healthy male adults. Subjects with high pre-existing titers were excluded in a screening step. Immune response was measured by a hemagglutination inhibition (HI) assay.

RESULTS

The seroprotection rates against A/California/7/2009 (H1N1), A/Perth/16/2009 (H3N2) and B/Brisbane/60/2009 were 74.42% [95% confidence interval (CI): 61.38-87.46], 72.09% (95% CI: 58.69-85.50), and 86.05% (95% CI: 75.69-96.40), respectively. Calculated seroconversion rates were 74.42% (95% CI: 61.38-87.46), 74.42% (95% CI: 61.38-87.46), and 79.07% (95% CI: 66.91-91.23), respectively. There were 25 episodes of solicited local adverse events in 21 subjects (47.73%), 21 episodes of solicited general adverse events in 16 subjects (36.36%) and 5 episodes of unsolicited adverse events in 5 subjects (11.36%). All adverse events were grade 1 or 2 and disappeared within three days.

CONCLUSION

The immunogenicity and safety of TIV established in this phase I trial are sufficient to plan a larger scale clinical trial.