Marek’s disease: new gene editing technique aids vaccine development.

New approach offers a simple and efficient method to manipulate the Turkey herpesvirus genome for rapid development of recombinant vaccines.

Scientists at The Pirbright Institute have used genetic engineering to develop a more efficient and effective vaccine for Marek’s disease, which could pave the way for a new generation of poultry disease vaccines.

Marek’s disease virus (MDV) is currently controlled by vaccination and over 20 billion vaccine doses are administered worldwide each year. Herpesvirus of turkeys (HVT) or Meleagrid herpesvirus 1 is widely used in the development of avian vaccines as a method of delivering elements of avian pathogens into birds to create the immune response that protects them against disease.

The technologies currently available for creating HVT recombinant vaccines are difficult and time consuming to use. In the case of Marek’s disease, the existing methods also hinder the level of protection the vaccines can offer, as birds are only protected against a few strains of MDV, leaving them vulnerable to the most dangerous strains.

Advances in technology have facilitated the development of a new gene editing technique called CRISPR/Cas9 (Clustered Regularly Interspaced Palindromic Repeats/ associated Cas9), which enables greater speed and accuracy in targeting, cutting and editing gene sequences.

Dr Yongxiu Yao, a senior scientist working in the Viral Oncogenesis group at the Pirbright Institute, used the CRISPR/Cas9 technology to genetically modify HVT; inserting part of MDV into it to generate a completely new genetically modified (GM) vaccine, which is capable of protecting against the most dangerous strains of the virus.

This innovative vaccine will be much quicker and easier to produce.

Dr Yao said, “This was a great opportunity to create a new generation of vaccines. HVT is widely used in the production of a variety of avian disease vaccines and genetically engineering it in this way has unlocked its potential to protect against all strains of Marek’s disease virus, as well as other dangerous avian viruses such as bird flu, which is also a danger to humans.

“More cost effective and efficient vaccines will help protect both avian and human health and potentially deliver major social and economic benefits in the UK and around the world”.

The Pirbright Institute is in discussion with international poultry vaccine manufacturing companies about the potential commercial exploitation of this approach.

The research was carried out in collaboration with the Wellcome Trust Sanger Institute.

Read article: Targeted editing of avian herpesvirus vaccine vector using CRISPR/Cas9 nuclease by Yongxiu Yao, Andrew Bassett and Venugopal Nair, published in International Journal of Vaccines and Technologies, online 15 November 2016