Reverse transcriptase viral load correlates with RNA in SIV/SHIV-infected macaques.

Area of Science:

• Virology
• Immunology
• Biotechnology

Background:

• Traditional viral load monitoring in macaques relies on in-house PCR methods.
• A novel kit measuring lentivirus reverse transcriptase (RT) activity presents an alternative to plasma viral RNA measurement.
• RT activity is a conserved lentiviral characteristic, theoretically enabling detection of all lentiviruses.

Purpose of the Study:

• To compare viral load (VL) measured by a commercial RT activity kit with an in-house quantitative RT-PCR (qRT-PCR) in macaques infected with SIV and SHIV.
• To assess the sensitivity and robustness of the RT assay for monitoring lentiviral replication in a macaque model.

Main Methods:

• Comparison of viral load (VL) using a commercial RT activity kit and an in-house qRT-PCR in SIV- and SHIV-infected macaques.
• Measurement of both RT activity and viral RNA levels over time.
• Validation using standardized control plasma samples from NIBSC.

Main Results:

• Strong correlation between RT activity and RNA levels for both SIV and SHIV (r = 0.95 and r = 0.92, p < 0.0001).
• VL trends from both assays mirrored each other, indicating measurement of viral replication.
• RT assay yielded higher levels (3-5x) than qRT-PCR, suggesting calibration differences.
• RT assay results closely matched designated VLs using standardized controls.

Conclusions:

• The commercial RT activity assay is sensitive and robust for monitoring SIV/SHIV viral load in macaques.
• This assay provides a valuable alternative, especially when molecular assays are unavailable.
• The commercial kit may reduce inter-laboratory variability associated with in-house PCR methods.