The use of human monoclonal antibodies to inform and enhance influenza vaccine virus selection.

Lead Research Organisation: The Francis Crick Institute
Department Name: Research

Abstract

Influenza infections each year cause a major burden of sickness and death (greater than 250,000 deaths each year world wide). The most effective means of reducing illness caused by influenza is by vaccination. The influenza virus evolves by changing its surface proteins each year in response to selective pressure from the human antibody response. The World Health Organisation coordinates a massive effort to monitor the evolution of influenza around the world to try and identify the viruses that are most likely to cause infections in the coming years, and select the best candidates for manufacture into a vaccine. The methods used to do this are both new, by sequencing virus genes to monitor genetic changes, and old, by testing the antibodies that ferrets make to candidate vaccine viruses for cross-reactivity with circulating strains. Ferret antibodies are traditionally used because these animals are susceptible to influenza infections in a way similar to humans. Overall the effectiveness (reduction in risk of becoming ill with influenza) of the vaccines selected by these methods is quite poor at ~54%, so there is room for improvement. Recent technical developments have provided a new method to analyse the evolution of influenza that uses human monoclonal antibodies. It is these human antibodies that are thought to be driving the evolution of influenza in nature. We have shown that human antibodies isolated from vaccinated or infected individuals can detect changes in the virus that the ferret antibodies miss. In addition the changes that human antibodies detect frequently correlate with the changes that are appearing in the influenza viruses currently circulating in the human population. We propose to develop panels of human monoclonal antibodies that can help predict the future evolution of the virus, which will be distributed to the WHO Collaborating Centres around the world, for comparison to the standard ferret antibodies to see if this new technology can improve vaccine selection.

Technical Summary

The World Health Organisation coordinates a massive effort to monitor the evolution of influenza around the world to try and identify the viruses that are most likely to cause infections in the coming years, and select the best candidates for manufacture into a vaccine. The methods used to do this predominantly involve sequencing virus genes to monitor genetic drift, and testing primary ferret sera to monitor antigenic drift. Overall the effectiveness of the vaccines selected by these methods is quite poor at ~54%, so there is room for improvement. Recently it has become possible to isolate human monoclonal antibodies in large numbers from infected or vaccinated individuals. It is human antibodies that are thought to be driving the evolution of influenza in nature. We have found that some individuals focus their antibody response onto limited regions of the haemagglutinin surface to such an extent that a single amino acid substitution can greatly reduce the neutralizing power of a serum. Focusing of the antibody to influenza in humans is a logical outcome of the selection of memory B cells by repeated exposures to evolving viruses that share less and less surface identity as time passes. Multiple monoclonal antibodies isolated from such individuals select for substitutions at few sites and these correlate with the changes that have become dominant recently in circulating viruses. In effect viral evolution can be recapitulated in vitro by these methods. An example is the K163Q substitution in clade 6B pdmH1N1 viruses. We have also shown that in this example ferret antisera failed to detect the change. We plan to develop panels of human monoclonal antibodies that can help predict the future evolution of the virus, which will be distributed to the WHO Collaborating Centres around the world, for comparison to the standard ferret antisera to see if this new technology can improve vaccine selection.

Planned Impact

The proposal is for the development of new tools for vaccinology and is based on the submission that through the use of human monoclonal antibodies a better understanding of the antigenic properties of influenza viruses can come about and from this improvements to the selection of influenza viruses for vaccines can be achieved. Improvements to influenza vaccine virus selection has been a priority for WHO over the last five or more years, with WHO running international meetings focussed on informal consultations on improving influenza vaccine virus selection, the fourth of which was held in Hong Kong in November 2015.

Should the use of human monoclonal antibodies prove to benefit the process then the impact will be self-evident and benefits will be seen in manufacturing - the production of better influenza vaccines - and in public health - mitigation of the threat of influenza.

The timescale for showing improvement in the decisions on the viruses for inclusion in influenza vaccines can be very rapid indeed - certainly within the life-span of this proposal. However, as with many research projects, mechanisms for the long-term sustainability of the principles of the research findings from the will need to be developed in due course.

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