Bluetongue virus: virology, pathogenesis and immunity

Area of Science:

• Veterinary Virology
• Immunology
• Epidemiology

Background:

• Bluetongue virus (BTV), an orbivirus, is transmitted by biting midges and causes significant disease in ruminants, particularly sheep.
• Recent emergence of novel BTV serotypes in Europe has led to devastating outbreaks in naive livestock populations.
• BTV infection involves specific viral proteins (VP2, VP7, VP5, NS1) and targets mononuclear phagocytes and endothelial cells, inducing inflammation and apoptosis.

Purpose of the Study:

• To review the epidemiology, pathogenesis, and immune responses related to Bluetongue virus.
• To discuss current vaccine strategies and highlight the need for improved approaches against BTV.

Main Methods:

• Review of scientific literature on Bluetongue virus transmission, replication, and host-pathogen interactions.
• Analysis of immune responses, including homologous and heterologous protection mechanisms.
• Evaluation of existing inactivated vaccines and emerging recombinant vaccine strategies.

Main Results:

• BTV entry mechanisms differ between insect and mammalian cells, with VP2 being crucial for serotype determination and neutralization.
• The virus can persist in erythrocytes for extended periods, complicating disease control.
• Homologous immunity relies on antibodies and T cells targeting external proteins, while heterologous protection involves T cells targeting internal proteins.

Conclusions:

• Classical inactivated vaccines offer serotype-specific protection but are insufficient for current epidemic control.
• Urgent development of recombinant vaccines is required for differentiating infected from vaccinated animals (DIVA) and achieving cross-protective immunity.
• Effective control of the worldwide Bluetongue virus threat necessitates advanced vaccine technologies.