Demonstration of de novo HIV type 1 production by detection of multiply spliced and unspliced HIV type 1 RNA in paraffin-embedded tonsils

HIV-1 infection of tonsils takes place when virus spreads systemically, and may occur when tonsillar tissue serves as the initial portal of HIV-1 entry. The HIV replication cycle includes the production of regulatory and accessory gene mRNAs, produced by splicing of genomic mRNA, that are hallmarks of de novo virus production. We sought to demonstrate, for the first time, the presence of multiply spliced viral RNA transcripts in archival tissue as a marker for active virus replication. Further, amplified cDNA sequences from unspliced pol gene mRNA were used to define the genetic subtype of HIV-1 within these tissues. RNA was extracted from surgical pathological, formalin-fixed, paraffin-embedded specimens, and RT-PCR was performed with primers for unspliced and multiply spliced HIV-1 transcripts. Amplification products were analyzed by agarose gel electrophoresis and their specificity was confirmed by sequencing and Southern blot hybridization. Unspliced HIV-1 pol transcripts yielded cDNA amplicons of 184 base pairs (bp) that were cloned and sequenced. Phylogenetic analysis revealed these sequences to be of HIV-1 subtype B. Multiply spliced transcripts specific for the tat/rev (173 bp), tat (268 bp), and tat/rev/nef (146 bp) regulatory gene mRNAs could be demonstrated in all cases. These results support the demonstration of active replication of HIV-1 in archival tonsillar tissues previously shown by p24 antigen staining. They also show the feasibility of performing molecular epidemiologic studies on HIV-1 cDNA sequences from archived pathologic specimens.