Immunogenicity of a single dose of trivalent influenza vaccine including A/Philippines (H3N2): results of a field trial

Enhancement of the safety of live influenza vaccine by attenuating mutations from cold-adapted hemagglutinin

In our previous study, X-31ca-based H5N1 LAIVs, in particular, became more virulent in mice than the X-31ca MDV, possibly by the introduction of the surface antigens of highly pathogenic H5N1 influenza virus, implying that additional attenuation is needed in this cases to increase the safety level of the vaccine. In this report we suggest an approach to further increase the safety of LAIV through additional cold-adapted mutations in the hemagglutinin. The cold-adaptation of X-31 virus resulted in four amino acid mutations in the HA. We generated a panel of 7:1 reassortant viruses each carrying the hemagglutinins with individual single amino acid mutations. We examined their phenotypes and found a major attenuating mutation, N81K. This attenuation marker conferred additional temperature-sensitive and attenuation phenotype to the LAIV. Our data indicate that the cold-adapted mutation in the HA confers additional attenuation to the LAIV strain, without compromising its productivity and immune response.

BCG Vaccination Enhances the Immunogenicity of Subsequent Influenza Vaccination in Healthy Volunteers: A Randomized, Placebo-Controlled Pilot Study

BACKGROUND

Influenza-related morbidity and mortality remain high. Seasonal vaccination is the backbone of influenza management but does not always result in protective antibody titers. Nonspecific effects of BCG vaccination related to enhanced function of myeloid antigen-presenting cells have been reported. We hypothesized that BCG vaccination could also enhance immune responses to influenza vaccination.

METHODS

Healthy volunteers received either live attenuated BCG vaccine (n = 20) or placebo (n = 20) in a randomized fashion, followed by intramuscular injection of trivalent influenza vaccine 14 days later. Hemagglutination-inhibiting (HI) antibodies and cellular immunity measured by ex vivo leukocyte responses were assessed.

RESULTS

In BCG-vaccinated subjects, HI antibody responses against the 2009 pandemic influenza A(H1N1) vaccine strain were significantly enhanced, compared with the placebo group, and there was a trend toward more-rapid seroconversion. Additionally, apart from enhanced proinflammatory leukocyte responses following BCG vaccination, nonspecific effects of influenza vaccination were also observed, with modulation of cytokine responses against unrelated pathogens.

CONCLUSIONS

BCG vaccination prior to influenza vaccination results in a more pronounced increase and accelerated induction of functional antibody responses against the 2009 pandemic influenza A(H1N1) vaccine strain. These results may have implications for the design of vaccination strategies and could lead to improvement of vaccination efficacy.

Natural killer (NK) cell response after vaccination of volunteers with killed influenza vaccine

Many experiments have shown convincingly that natural killer (NK) cell activity against viral infections is an important early defence mechanism in mice. Since the NK response occurs soon after infection, often long before clinical signs of disease become manifest, it has been difficult to design studies to monitor accurately NK cell kinetics following infection, without actually administering pathogens to volunteers. There is therefore little data pertaining to the role of NK cells in humans. Nevertheless, a number of studies have shown elevated NK activity in response to herpes simplex and influenza virus infections in humans. Our study was designed to show that NK activity could be provoked in humans by exposure to viral particles without actual live viral infection. The development of NK cell response in the peripheral blood of volunteers shortly after vaccination with killed influenza trivalent vaccine was studied. The results demonstrate that killed virus vaccine induces and augments NK cell activity for relatively long periods. Such data may prove valuable for designing possible modes of augmenting NK activity as a therapeutic tool.