Active human immunodeficiency virus protease is required for viral infectivity

Area of Science:

• Virology
• Molecular Biology
• Biochemistry

Background:

• Retroviral proteins are synthesized as polyproteins requiring proteolytic cleavage for maturation.
• The human immunodeficiency virus (HIV) protease plays a critical role in processing these viral polyproteins during replication.

Purpose of the Study:

• To investigate the essential role of the HIV protease in the viral replication cycle.
• To determine the impact of a specific mutation within the HIV protease gene on its enzymatic activity and viral infectivity.

Main Methods:

• Site-directed mutagenesis was used to alter a specific residue (Asp-25 to Asn-25) in the HIV protease gene.
• The mutant HIV protease was expressed in E. coli and its proteolytic activity against HIV gag p55 was assessed in vitro.
• A mutant HIV provirus containing the Asn-25 mutation was constructed and transfected into SW480 cells.
• Virions produced from transfected cells were analyzed for gag protein processing and infectivity against MT-4 lymphoid cells.

Main Results:

• The Asn-25 mutation eliminated the in vitro proteolytic activity of the HIV protease against HIV gag p55.
• Virions produced from cells transfected with the Asn-25 mutant provirus contained uncleaved gag p55, lacking mature gag p24 and gag p17.
• These mutant virions were unable to infect MT-4 lymphoid cells, unlike wild-type virions.

Conclusions:

• The HIV protease is an essential viral enzyme required for the production of infectious virions.
• The specific Asp-25 residue is critical for the protease's enzymatic function.
• The HIV protease represents a promising target for the development of anti-HIV therapeutic drugs.