HUMAN-HERPESVIRUS-8 VARIANTS IN SARCOID TISSUES

Background The cause of sarcoidosis is unknown, although mycobacteria have been implicated. We examined sarcoid tissues for human herpesviru s 8 (HHV-8) in addition to mycobacterial genomic sequences. Methods Bi opsy samples from 17 patients with sarcoidosis were studied (eight tra nsbronchial, 27 lymph node, two skin, and two oral mucosa). We used ti ssues (n=137) from 96 patients without sarcoidosis as negative control s. A nested PCR was applied to amplify a segment of open reading frame (ORF) 26 of the HHV-8 genome, and a heminested PCR was used to amplif y a segment of ORF 25 of HHV-8 and of the 16 S rRNA gene of mycobacter ia. Differences in base sequences of the amplified fragments were reso lved with single-strand conformation polymorphism and dideoxy sequenci ng. Findings HHV-8 ORF 26 DNA was detected in significantly higher pro portions of sarcoid than of non-sarcoid tissue samples from lung (8/8 vs 0/54; p<0.0001), lymph nodes (26/27 vs 6/29; p<0.0001), skin (2/2 v s 0/17; p=0.006), and oral tissues (2/2 vs 1/13; p=0.029). 31 (82%) of the 38 ORF 26 DNA-positive sarcoid specimens were also positive for O RF 25 DNA. For mycobacteria-like. 16 S rRNA DNA, the proportion positi ve was significantly higher in sarcoid than non-sarcoid tissues for ly mph node samples (11/27 vs 2/29; p=0.003) but not for other tissues (l ung 3/8 vs 22/54; skin 2/2 vs 15/17; and oral tissues 1/2 vs 0/13). Ov erall, the prevalence of HHV-8 ORF 26 sequences was higher in sarcoid tissues than in non-sarcoid tissues (p<0.0001). When patients whose ti ssues were included in a masked phase of the study were treated as uni ts of analysis, eight of eight sarcoidosis patients were positive for HHV-8 ORF 26 DNA, compared with three of 56 control patients (p<0.0001 ); for mycobacteria-like sequences, three of eight sarcoidosis patient s were positive, compared with four of 56 controls (p=0.0464). The HHV -8 ORF 26 sequences, ten of which were unique, could be segregated int o four groups according to peptide motifs. In seven of nine patients f rom whom biopsy samples were taken from various sites, different seque nces were recovered. The mycobacterial sequences amplified from sarcoi d tissues were also varied, but none was homologous to those of known species. Interpretation Variant HHV-8 DNA sequences are found in a wid e range of sarcoid but not non-sarcoid tissues. Mycobacteria-like 16 S rRNA sequences are more frequently present in sarcoid lymph nodes and not in other tissue types, but do not indicate infection by a particu lar mycobacterial species.