Alphapolyomavirus

Alphapolyomavirus

Alphapolyomavirus is a genus of viruses in the family Polyomaviridae. Members of this genus are small, non-enveloped viruses with a circular double-stranded DNA genome. They are known to infect a variety of mammalian hosts, including humans, and are associated with various diseases.

Structure

Alphapolyomaviruses are characterized by their icosahedral capsid structure, which is approximately 40-45 nm in diameter. The capsid is composed of 72 pentameric capsomers made up of the major capsid protein VP1, with minor capsid proteins VP2 and VP3 located internally. The genome of alphapolyomaviruses is approximately 5,000 base pairs in length and encodes several proteins, including the large T antigen and small t antigen, which are involved in viral replication and cell transformation.

Genome

The genome of alphapolyomaviruses is circular and double-stranded, containing early and late regions. The early region encodes the large T antigen and small t antigen, which are crucial for viral replication and modulation of the host cell cycle. The late region encodes the structural proteins VP1, VP2, and VP3, which form the viral capsid.

Replication Cycle

Alphapolyomaviruses enter host cells through receptor-mediated endocytosis. Once inside the cell, the viral genome is transported to the nucleus, where it is transcribed and replicated. The large T antigen plays a key role in unwinding the viral DNA and recruiting host DNA polymerase for replication. Viral assembly occurs in the nucleus, and progeny virions are released by cell lysis.

Pathogenesis

In humans, alphapolyomaviruses are associated with various diseases, particularly in immunocompromised individuals. For example, BK virus and JC virus, both members of the Alphapolyomavirus genus, can cause nephropathy and progressive multifocal leukoencephalopathy, respectively. These viruses are typically acquired in childhood and remain latent in the host, reactivating under conditions of immunosuppression.

Diagnosis and Treatment

Diagnosis of alphapolyomavirus infections is typically achieved through PCR-based methods to detect viral DNA in clinical samples. Treatment options are limited, and management often focuses on reducing immunosuppression in affected individuals. Antiviral agents such as cidofovir have been used with varying success.

Also see

• Polyomaviridae
• BK virus
• JC virus
• Viral replication
• Virus classification