Generation of H3N8 CIVs containing truncated or deleted NS1 protein

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First description of a LAIV for the prevention and control of influenza in dogs

Text by Luis Martínez-Sobrido

Canine influenza is a common and contagious respiratory disease of dogs caused by canine influenza virus (CIV). Influenza infections, including CIV, are effectively prevented through vaccination. To date, only CIV inactivated influenza vaccines (i.e. made of killed virus) are available commercially. Live attenuated influenza vaccines have been shown to provide better immune responses to protect against influenza. Here we developed a live attenuated vaccine for the prevention of CIV. To generate the vaccine we modified the viral non-structural protein 1 (NS1) using a genetic engineering technique known as reverse genetics. NS1 mutant CIVs were safe when tested in mice and also able to confer protection against CIV challenge. Moreover, a single intranasal immunization dose showed higher immunogenicity and protection than that conferred with a commercial inactivated vaccine, making our live-attenuated CIV an excellent vaccine candidate for the prevention and control of CIV in dogs.

The emergence of the H3N8 and H3N2 CIVs and their rapid spread in the dog population represent threats to canine health through animal shelters and kennels, and also create opportunities for exposure of humans and other animals. As dogs have been infected with both mammalian and avian influenza viruses, they have the potential to act like pigs, as “mixing vessel” hosts for the generation of new strains. Previous studies have shown that truncations or deletions in the NS1 protein significantly attenuate influenza viruses and such approach has been used with human, swine and equine influenza viruses to generate potential vaccines. That gave us the idea of using a similar approach for the generation of vaccine candidates for the prevention of CIV, and our initial data using the mouse model of influenza infection support the usefulness of this approach. This is the first description of live attenuated candidates for the prevention of CIV in dogs. Because our success with CIV LAIVs in mice, we are seeking to carry out clinical trials in dogs, the real target host of CIV, in order to prevent the infection and transmission of this relatively new canine respiratory pathogen.

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Non-structural protein 1 (NS1) truncated (NS1-126, NS1-99 and NS1-73) or deleted (DNS1) H3N8 canine influenza viruses (CIVs) were tested for their safety, immunogenicity and protection efficacy as live-attenuated influenza vaccines (LAIVs) against wild-type (WT) H3N8 CIV. All recombinant NS1 mutant viruses were attenuated in vivo (mice) and ex vivo (canine tracheal explants), but able to confer, upon a single intranasal immunization dose, complete protection against challenge with WT CIV H3N8. Notably, immunogenicity and protection efficacy conferred by the NS1 mutant H3N8 CIVs was better than that observed with a CIV H3N8 inactivated influenza vaccine (IIV). This is the first description of a LAIV generated by reverse genetics for the prevention and control of H3N8 CIV in dogs. Future studies aimed towards a more detailed immunogenic and protection characterization of the recombinant NS1 truncated or deleted H3N8 CIVs in dogs are planned.

 

Introducing the authors

authors

Pictured Dr. Gonzalez (left) and Dr. Martinez-Sobrido

Dr. Aitor Nogales Gonzalez, Ph.D., is a postdoctoral fellow in the laboratory of Dr. Luis Martinez-Sobrido in The Department of Microbiology and Immunology at University of Rochester, Rochester, NY. His research interest has been focused on the molecular biology, virus-host interaction and pathogenesis of positive- and negative-stranded RNA viruses. During his PhD under the supervision of Drs. Luis Enjuanes and Fernando Almazan at the National Centre of Biotecnology (Madrid, Spain), he studied the mechanism of replication and transcription of coronavirus and the role of host factors that modulate these processes. Next, he started his post-doctoral position in the laboratory of Dr. Luis Martinez-Sobrido at University of Rochester. His post-doctoral research has focused on the generation of reporter-expressing influenza A and B viruses, which have shown to be powerful tools for the evaluation of compound with antiviral activity, for identification of neutralizing antibodies or to study viral pathogenicity in vivo. He has also generated attenuated viruses as vaccine candidates, for the treatment of influenza and arenavirus infections in humans and other mammalians.

Dr. Luis Martinez-Sobrido, Ph.D., is an Associate Professor in the Department of Microbiology and Immunology at University of Rochester, Rochester, NY. His graduate research focused on the study of viral replication and transcription of Respiratory Syncytial Virus (RSV) under the guidance of Dr. Jose Antonio Melero at the Instituto de Salud Carlos III in Madrid, Spain. He next conducted post-doctoral research on the molecular biology of negative stranded RNA viruses, mainly influenza A and B viruses, under the supervision of Dr. Adolfo Garcia-Sastre in the Department of Microbiology at the Icahn School of Medicine at Mount Sinai in New York, USA. His current research interest at University of Rochester focuses on the molecular biology, pathogenesis, innate immune responses and vaccine development for RNA viruses, mainly arenaviruses and influenza.

About the research

Canine influenza viruses with modified NS1 proteins for the development of live-attenuated vaccines
Aitor Nogales, Kai Huang, Caroline Chauché, Marta L. DeDiego, Pablo R. Murcia, Colin R. Parrish, Luis Martínez-Sobrido
Virology, Volume 500, January 2017, Pages 1–10