Quantitative Assessment of the Sensitivity of Various Commercial Reverse Transcriptases Based on Armored HIV RNA

Authors: J. Okello, L. Rodriguez, D. Poinar, K. Bos, A. Okwi, G. Bimenya, N. Sewankambo, K. Henry, M. Kuch, H. Poinar
Journal:PLoS One, doi:10.1371/journal.pone.0013931

The in-vitro reverse transcription of RNA to its complementary DNA, catalyzed by the enzyme reverse transcriptase, is the most fundamental step in the quantitative RNA detection in genomic studies. As such, this step should be as analytically sensitive, efficient and reproducible as possible, especially when dealing with degraded or low copy RNA samples. While there are many reverse transcriptases in the market, all claiming to be highly sensitive, there is need for a systematic independent comparison of their applicability in quantification of rare RNA transcripts or low copy RNA, such as those obtained from archival tissues.
Methodology/Principal Findings:
We performed RT-qPCR to assess the sensitivity and reproducibility of 11 commercially available reverse transcriptases in cDNA synthesis from low copy number RNA levels. As target RNA, we used a serially
known number of Armored HIV RNA molecules, and observed that 9 enzymes we tested were consistently sensitive to 1,000 copies, seven of which were sensitive to ,100 copies, while only 5 were sensitive to ,10 RNA template copies across all replicates tested. Despite their demonstrated sensitivity, these five best performing enzymes (Accuscript, HIV-RT, M-MLV, Superscript III and Thermoscript) showed considerable variation in their reproducibility as well as their overall amplification efficiency. Accuscript and Superscript III were the most sensitive and consistent within runs, with Accuscript and Superscript II ranking as the most reproducible enzymes between assays.
We therefore recommend the use of Accuscript or Superscript III when dealing with low copy number RNA levels, and suggest purification of the RT reactions prior to downstream applications (eg qPCR) to augment detection. Although the results presented in this study were based on a viral RNA surrogate, and applied to nucleic acid lysates derived from archival formalin-fixed paraffin embedded tissue, their relative performance on RNA obtained from other tissue types may vary, and needs future evaluation.

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Comparison of methods in the recovery of nucleic acids from archival formalin-fixed paraffin-embedded autopsy tissues

Authors: J. Okello, J. Zurek, A. Devault, M. Kuch, A. Okwi, N. Sewankambo, G. Bimenya, D. Poinar, H. Poinar
Journal:Analytical Biochemistry, doi:10.1016/j.ab.2010.01.014

Archival formalin-fixed paraffin-embedded (FFPE) human tissue collections are typically in poor states of
storage across the developing world. With advances in biomolecular techniques, these extraordinary and
virtually untapped resources have become an essential part of retrospective epidemiological studies. To
successfully use such tissues in genomic studies, scientists require high nucleic acid yields and purity. In
spite of the increasing number of FFPE tissue kits available, few studies have analyzed their applicability
in recovering high-quality nucleic acids from archived human autopsy samples. Here we provide a study
involving 10 major extraction methods used to isolate total nucleic acid from FFPE tissues ranging in age
from 3 to 13 years. Although all 10 methods recovered quantifiable amounts of DNA, only 6 recovered
quantifiable RNA, varying considerably and generally yielding lower DNA concentrations. Overall, we
show quantitatively that TrimGen’s WaxFree method and our in-house phenol–chloroform extraction
method recovered the highest yields of amplifiable DNA, with considerable polymerase chain reaction
(PCR) inhibition, whereas Ambion’s RecoverAll method recovered the most amplifiable RNA.

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