Maedi-visna virus persistence: Antigenic variation and latency.

Area of Science:

• Virology
• Immunology
• Animal Health

Background:

• Maedi-visna virus (MVV) is a lentivirus causing lifelong infections in sheep.
• Lentiviruses are known for their ability to establish persistent infections within their hosts.

Purpose of the Study:

• To investigate the genetic changes and transmission dynamics of Maedi-visna virus in naturally infected sheep.
• To understand the role of immune selection in the persistence and evolution of MVV.

Main Methods:

• Intravenous inoculation of five sheep with MVV.
• Co-housing infected and uninfected sheep to facilitate natural transmission.
• Sequence analysis of viral isolates from naturally infected and carrier sheep.
• Identification of mutations in the viral Env gene, particularly in neutralization domains.

Main Results:

• Naturally transmitted MVV isolates exhibited multiple mutations in the Env principal neutralization domain, indicating antigenic variation.
• Isolates from carrier sheep largely retained the sequence of the original infecting strain.
• Evidence of positive selection was observed in the Env gene, especially at neutralization epitopes and glycosylation sites.

Conclusions:

• Virus persistence in sheep is likely maintained by a reservoir of latent viruses.
• Natural transmission selects for the emergence of antigenic variants of Maedi-visna virus.
• These findings highlight the evolutionary strategies employed by lentiviruses for long-term survival.