We conducted a study to identify the viruses in tissue specimens of oral "hairy" leukoplakia, a lesion that is found in immunosuppressed male homosexuals and that is associated with the subsequent development of the acquired immunodeficiency syndrome. When stained for papillomavirus core antigen, 49 of 67 biopsy specimens (73 per cent) yielded positive results in epithelial-cell nuclei. Electron microscopy showed papillomavirus-like particles in all of 25 specimens, and the herpes-type virus described in a previous report was seen in 23 of the 25 specimens. Three specimens had both types of particle in the same individual epithelial cells. Immunofluorescence for herpes simplex virus, varicella-zoster virus, and cytomegalovirus gave negative results in all cases, but 19 of 20 specimens showed intense nuclear staining in epithelial cells for the viral capsid antigen of Epstein-Barr virus (EBV). DNA hybridization using EBV probes in Southern blots demonstrated EBV DNA in all of 13 specimens and found 200 or more viral DNA molecules per cellular genome in 11 of the 13. The whole EBV genome was also demonstrated in the specimens and found to be in linear virion form. We conclude that EBV replicates within the epithelial cells in hairy leukoplakia.

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Combination therapy with protease (PR) and reverse transcriptase (RT) inhibitors can efficiently suppress human immunodeficiency virus (HIV) replication, but the emergence of drug-resistant variants correlates strongly with therapeutic failure. Here we describe a new method for high-throughput analysis of clinical samples that permits the simultaneous detection of HIV type 1 (HIV-1) phenotypic resistance to both RT and PR inhibitors by means of recombinant virus assay technology. HIV-1 RNA is extracted from plasma samples, and a 2.2-kb fragment containing the entire HIV-1 PR- and RT-coding sequence is amplified by nested reverse transcription-PCR. The pool of PR-RT-coding sequences is then cotransfected into CD4+ T lymphocytes (MT4) with the pGEMT3ΔPRT plasmid from which most of the PR (codons 10 to 99) and RT (codons 1 to 482) sequences are deleted. Homologous recombination leads to the generation of chimeric viruses containing PR- and RT-coding sequences derived from HIV-1 RNA in plasma. The susceptibilities of the chimeric viruses to all currently available RT and/or PR inhibitors is determined by an MT4 cell–3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide-based cell viability assay in an automated system that allows high sample throughput. The profile of resistance to all RT and PR inhibitors is displayed graphically in a single PR-RT-Antivirogram. This assay system facilitates the rapid large-scale phenotypic resistance determinations for all RT and PR inhibitors in one standardized assay.

Antiretroviral treatment guided prospectively by PRT led to the increased use of "active" antiretroviral agents and was associated with a significantly better virological response.

. Studies of viral genotype and phenotype after virus rebound revealed that the initial active site mutation allowing for nelfinavir resistance is mediated by a unique amino acid substitution in the HIV-1 protease D30N, which does not confer in vitro phenotypic cross-resistance to the currently available protease inhibitors.