Live temperature-sensitive equine influenza virus vaccine: generation of the virus and efficacy in hamsters.

The study outlines the creation of temperature-sensitive variants of an equine influenza virus and assesses their effectiveness in hamsters. The research involves the use of genetic manipulation to develop strains that potentially could function as a vaccine against equine influenza.

Generation of Temperature-Sensitive Equine Influenza Virus

• A process of genetic reassortment was undertaken to create temperature-sensitive versions of an equine influenza virus belonging to subtype A-1.
• The virus was mated with a temperature-sensitive human influenza virus and a wild-type equine influenza virus, leading to isolating a temperature-sensitive reassortant virus that had certain surface antigens of equine origin.
• Two clones called 8B1 and 71A1 were produced, each with different in vitro shutoff temperatures for plaque formation.
• The human donor virus had temperature-sensitive mutations on certain genes like polymerase 3 (P3) and nucleoprotein, meaning that the created equine reassortants could bear one or both of these temperature-sensitive genes.

Analysis of Virus Genetics

• Analysis was made to determine where the gene mutations are on the reassortant clones. Clone 8B1 was found to have a mutation on the P3 gene, and clone 71A1 had mutations on both the nucleoprotein and P3 genes.
• The researchers performed a genetic investigation on the parental origin of the genes in each clone and discovered that the majority of genes in each clone came from the equine parent virus, with the remaining genes being derived from the human donor virus.

Assessment of Virus Behaviour in Hamsters

• The researchers studied how the virus clones grew in the lungs of hamsters. Growth was limited in the lungs but was similar to the wild-type virus in the hamster’s nasal passages.
• Additionally, the virus isolates taken from the hamsters’ lungs or nasal passages still retained the temperature-sensitive phenotype.

Implications of the Research

• The findings set the stage for further studies to assess these temperature-sensitive equine influenza viruses for their potential use as a vaccine, specifically looking at their level of attenuation (weakening) and immunogenicity (ability to provoke an immune response) in horses.