Mucosal vaccination with an attenuated maedi-visna virus clone

Area of Science:

• Veterinary Virology
• Immunology
• Sheep Diseases

Background:

• Maedi-visna virus (MVV) causes a progressive, debilitating disease in sheep.
• Attenuated viral vaccines are explored to control MVV infections.
• Understanding immune responses to MVV superinfection is crucial for vaccine development.

Purpose of the Study:

• To evaluate the efficacy of an attenuated MVV molecular clone as a vaccine against subsequent challenge with a pathogenic MVV clone.
• To assess the level of protection conferred by the attenuated MVV vaccine in sheep.

Main Methods:

• Intratracheal inoculation of four sheep with an attenuated MVV molecular clone.
• Subsequent intratracheal challenge with a pathogenic MVV clone ten months later.
• Comparison of viral load in blood and lungs between vaccinated and unvaccinated control sheep at sacrifice.

Main Results:

• All sheep, vaccinated and unvaccinated, became infected with the challenge MVV clone.
• Vaccinated sheep exhibited significantly lower virus isolation rates from blood compared to unvaccinated controls.
• Virus was isolated ten times less frequently from the lungs of vaccinated sheep than from unvaccinated sheep at sacrifice.

Conclusions:

• The attenuated MVV vaccine did not provide complete protection against superinfection with a pathogenic MVV clone.
• Partial protection was indicated by reduced viral loads in vaccinated sheep, suggesting a potential role for this vaccine strategy.
• Further research is warranted to enhance vaccine efficacy against maedi-visna virus.