Attenuated replication of human immunodeficiency virus type 1 with a didanosine-selected reverse transcriptase...

Area of Science:

• Virology
• Molecular Biology
• Drug Resistance

Background:

• Didanosine (ddI) therapy can select for the Leu74Val mutation in HIV-1 reverse transcriptase (RT).
• This mutation is linked to reduced susceptibility to ddI.
• The impact of this mutation on viral replication efficiency is not fully understood.

Purpose of the Study:

• To investigate the effect of the Leu74Val mutation on HIV-1 replication.
• To determine if the Leu74Val mutation confers a replication disadvantage.
• To provide a rationale for observed clinical outcomes of ddI therapy.

Main Methods:

• Engineered a cloned HIV-1 virus with the Leu74Val mutation in RT.
• Assessed replication efficiency of wild-type, mutant, and revertant viruses.
• Compared replication of clinical isolates with and without the Leu74Val mutation.
• Quantified viral fitness through single-passage experiments.

Main Results:

• Engineered Leu74Val mutant virus showed attenuated replication.
• A revertant virus (Val-to-Leu) replicated similarly to wild-type.
• Clinical isolates with Leu74Val and Thr215Tyr mutations were less replicative than those with Thr215Tyr alone.
• Viruses with Leu74Val exhibited an 11% loss of fitness compared to wild-type.

Conclusions:

• The Leu74Val mutation confers a significant replication disadvantage to HIV-1.
• This impaired viral fitness is a key factor in the reduced viral RNA levels seen with ddI therapy.
• The findings explain why Leu74Val mutants may be difficult to detect post-therapy due to their low replication rates.