Phosphonoformate inhibition of visna virus replication

Area of Science:

• Virology
• Antiviral Research
• Molecular Biology

Background:

• Visna virus, an ovine lentivirus, causes progressive neurological disease.
• Reverse transcriptase is a key enzyme in lentivirus replication.
• Identifying effective antiviral agents is crucial for managing viral infections.

Purpose of the Study:

• To investigate the antiviral activity of phosphonoformate (PFA) against visna virus.
• To determine the effect of PFA on visna virus replication and associated cytopathic effects.
• To assess the impact of PFA on cell-free reverse transcriptase activity.

Main Methods:

• Infection of sheep choroid plexus cells with visna virus.
• Treatment of infected cells with varying concentrations of PFA.
• Quantification of virus yield and assessment of morphological changes.
• Enzymatic assays to measure cell-free reverse transcriptase activity.

Main Results:

• PFA significantly reduced visna virus yield by 50% at concentrations of 20-80 microM.
• PFA reversibly prevented virus-induced syncytial formation and cell degeneration.
• Cell growth was unaffected at 500 microM PFA but arrested at 2 mM with prolonged exposure.
• Cell-free reverse transcriptase activity was inhibited by approximately 90% with 100 microM PFA.
• Kinetic analysis indicated reverse transcriptase is used early in the infection cycle.
• Phosphonoacetate showed no inhibitory effect on visna virus or reverse transcriptase.

Conclusions:

• Phosphonoformate demonstrates significant antiviral activity against visna virus.
• PFA effectively inhibits viral replication and protects cells from cytopathic effects.
• PFA targets reverse transcriptase activity, a critical step in the visna virus life cycle.