Influenza research

The Influenza Resource Centre carries out research into various aspects of influenza virus biology, mainly related to influenza vaccines.

Improving candidate vaccine viruses (CVVs)

CVVs are viruses used to produce influenza vaccines on a manufacturing scale. They are crucial components of all influenza vaccine production campaigns.

Ideal CVVs should have these properties:

• antigenically appropriate
• efficient growth in the substrate for vaccine production – mostly embryonated chicken eggs but also cultured cells
• high yield of influenza virus antigens – mainly haemagglutinin (HA) protein and also neuraminidase (NA) protein
• safe to work with in the manufacturing environment

A major concern with current CVVs is the variability in virus and antigen yield between strains. Yield affects the number of doses that can be produced in a given time, and is particularly important in an influenza pandemic when a large number of vaccine doses need to be produced in as short a time as possible.

We have been exploring strategies to improve the yield of CVVs. Our main approach has been using chimaeric HA gene constructs. We have replaced domains of the wild-type (wt) HA with corresponding domains of the HA of the high-yielding donor virus A/Puerto Rico/8/34 (PR8). We showed yield improvement for an A(H5N1) and an A(H1N1)pdm09 virus.

We are currently expanding this work to other viral subtypes, having received funding from the Biomedical Advanced Research and Development Authority (BARDA)/US Department of Health and Human Services (HHS).

We have also been interested in amino acid changes in the HA that viruses, including CVVs, acquire upon growth in eggs – egg-adaptive mutations. It has long been known that such changes improve the growth characteristics of influenza viruses in eggs – but some of these changes alter the antigenic properties of viruses, making them unsuitable for vaccine production.

Recently we identified amino acid changes that improved the yield of an A(H1N1)pdm09 CVV. However we also found that these adaptive changes are not generically enhancing the yield of CVVs, as they failed to improve the yield of a closely related virus.

We are also interested in the effects of changes in the non-coding regions (NCRs) of viral genomic RNAs. Recently we developed a prototype of a live attenuated influenza virus. This virus contains changes in the NCR of the HA RNA segment that led to enhanced expression of the HA protein but attenuated virus replication in vitro and in vivo.

In a collaboration with the Roslin Institute, we are looking to find improved viral ‘backbones’. The aim of this work – also funded by BARDA/HHS – is to develop an improved high-yield donor virus that can be used to generate consistently good CVVs.

New potency assays for influenza vaccines

The current gold standard method for measuring the potency of inactivated influenza vaccines is the single radial immune diffusion test (SRD). The influenza vaccine community wants to develop alternative potency assays for influenza vaccines. Our influenza group has external funding from BARDA/HHS to work in this area.

We are making use of single-domain antibodies identified and produced at NIBSC to develop a new potency assay. These single-domain antibodies are selected for broad cross-reactivity with HAs of divergent influenza viruses, including viruses of different subtypes. They will be used to establish an ELISA-based potency assay.

Antigenic characterisation of viruses of pandemic potential

We are part of a consortium of laboratories led by Dr Yoshihiro Kawaoka of the University of Wisconsin and funded by the Bill and Melinda Gates Foundation that works on identifying traits affecting the pandemic potential of avian influenza viruses. NIBSC is involved in the antigenic characterisation of A(H5N1) viruses.

Standardising influenza serology

The human immune response to influenza virus infection or vaccination is assessed with the haemagglutination inhibition (HI) and virus neutralisation (VN) assays. Both assays are highly variable between laboratories, making comparisons between studies difficult.

We are working with the Consortium for the Standardisation of Influenza Seroepidemiology (CONSISE)  on this.

NIBSC has proved that using antibody standards can improve comparability between laboratories. Current and future work with international partners explores the further use of standards and how much we can improve this by harmonising and standardising assay methods.

Broadly reactive influenza vaccines

We are part of two European projects – funded under the FP7 programme of the European Commission – investigating approaches towards influenza vaccines that provide better protection against a broader range of diverse influenza viruses. These types of vaccines are sometimes called universal influenza vaccines.

We use our experience in influenza animal models and influenza serology to support the overall goals of these projects.

One of the projects, EDUcate inFLUenza vACcine (EDUFLUVAC), uses virus-like particles (VLPs) and a combinatorial immunisation strategy to educate the immune system towards cross-recognition and coverage against antigenic drift in seasonal influenza virus exposure.

The other project – Universal Influenza Vaccines Secured (UNISEC) – brings together a number of vaccine concepts into a single study to identify, develop and clinically test the most promising leads for a universal influenza vaccine.