An enzyme immunoassay membrane test (Directigen RSV) for the detection of respiratory syncytial virus in clinical specimens was compared prospectively with isolation in cell culture and direct immunofluorescence (IF). A total of 315 nasopharyngeal wash specimens from pediatric patients were examined. Directigen RSV was 86.1% sensitive and 91.3% specific for specimens positive by isolation in cell culture and/or IF, with 88.6% agreement. The false-positive rate was 16%; 2 of 20 specimens giving false-positive reactions by Directigen RSV were true-positives by blocking assay. Twenty-seven specimens (8.5%) whose results were initially uninterpretable by Directigen RSV due to filtration difficulties were diluted and upon retesting produced acceptable results. Sixty-three viral isolates and/or IF identifications of virus antigens representing seven virus groups other than respiratory syncytial virus were also found; cross-reactions between Directigen RSV and other viruses were not observed. Directigen RSV will be useful as an immediate procedure and in facilities lacking a comprehensive virology laboratory.
Maturation of infectious human immunodeficiency virus type 1 (HIV-1) particles requires proteolytic cleavage of structural polyproteins by viral protease. Inhibition of protease is a powerful tool for the treatment of HIV infection. Using a well-established phenotypic drug susceptibility assay, we found that sequences outside of the protease gene can modulate the susceptibility to protease inhibitors (PIs). Chimeric viruses carrying p1-p6/p6* sequences from patient isolates in the context of an NL4-3 molecular clone exhibited increased PI susceptibility. Furthermore, this phenotype was associated with a delay in protease autoprocessing in virions and a reduction in replication capacity. We propose that the interplay between protease and the C terminus of Gag is critical for proper protease activity and mismatches between these regions can reduce viral replication and increase drug susceptibility.
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