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Mutations to the probe of Cobas TaqMan HIV-1 ver. 1.0 assay causing undetectable viral load in a patient with acute HIV-1 infection


We encountered a human immunodeficiency virus (HIV)-1 in which the viral load was undetectable with the Cobas TaqMan HIV-1 ver. 1.0 (CTM v.1.0) in a patient with acute HIV-1 infection. The CTM v.1.0 assay showed more than 1,000-fold underestimation compared with the subsequent Cobas Amplicor Monitor v.1.5 assay. Because five mismatches to the CTM v.1.0 assay probe in the HIV-1 virus in the patient were disclosed by the manufacturer, partial gag regions of the HIV genome were directly sequenced from the patient’s plasma viral RNA. The detected single nucleotide point mutations were located near the 5′-end of the Cobas Amplicor Monitor probe. Clinicians should be very careful in making interpretations when indeterminate Western blot analysis results and a low or even undetectable HIV-1 viral load are encountered with the CTM HIV-1 ver. 1.0 assay in patients with suspected acute HIV infection. Repeating Western blot analysis is essential before considering a low HIV-1 viral load to be a false-positive result.

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We are indebted to Mr. Roderick J. Turner, Assistant Professor Edward F. Barroga, and Professor J. Patrick Barron, Chairman of the Department of International Medical Communications at Tokyo Medical University, for their review of the English manuscript.

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Correspondence to Mihoko Yotsumoto.

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Yotsumoto, M., Shinozawa, K., Yamamoto, Y. et al. Mutations to the probe of Cobas TaqMan HIV-1 ver. 1.0 assay causing undetectable viral load in a patient with acute HIV-1 infection. J Infect Chemother 17, 863–865 (2011).

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  • TaqMan HIV-1 real-time PCR assay
  • Acute HIV-1 infection
  • Mutations to the probe
  • Undetectable HIV-1 viral load