Detection of squirrel monkey retroviral sequences in interferon samples

Area of Science:

• Virology
• Molecular Biology
• Immunology

Background:

• Interferons are used for viral infections and cancer immunotherapy.
• Human lymphoid cell lines, like Namalwa, used for interferon production may contain integrated squirrel monkey retrovirus (SMRV) DNA.
• SMRV is related to simian type D retroviruses.

Purpose of the Study:

• To determine the presence of SMRV sequences in commercial interferon preparations.
• To assess the sensitivity of detection methods for retroviral sequences.

Main Methods:

• DNA extraction from 75 commercial interferon preparations.
• Polymerase chain reaction (PCR) and DNA sequencing to detect SMRV sequences.
• Nested PCR developed for enhanced sensitivity; beta-actin amplification confirmed human DNA presence.
• Southern blot hybridization and direct DNA sequencing validated SMRV sequence authenticity.

Main Results:

• Squirrel monkey retrovirus-pol sequences were detected in 39 of 75 interferon samples.
• A nested PCR assay detected SMRV sequences more sensitively than single PCR.
• 29 samples showed weak or very weak positivity by single PCR, highlighting the nested assay's importance.

Conclusions:

• The study confirms the presence of SMRV sequences in commercial interferon preparations.
• A sensitive nested PCR assay is crucial for detecting low-level retroviral sequences.
• The biological significance of the detected residual DNA sequences requires further investigation.