Open reading frame 26 of human herpesvirus 8 encodes a tetradecanoyl phorbol acetate- and butyrate-inducible 32-kilodalton protein expressed in a body cavity-based lymphoma cell line

DNA sequences corresponding to a novel herpesvirus (human herpesvirus 8 [HHV8]) are associated with Kaposi's sarcoma (KS), Castleman's disease, and body cavity-based lymphomas (BCBL). Studies of a BCBL-derived cell line suggest a direct correlation between seropositivity against antigens specifically present in such lines and the development of KS. We have generated recombinant proteins corresponding to open reading frame (ORF) 26 of HHV8 and have produced affinity-purified antibodies. Using these antibodies, we studied the expression of HHV8 ORF26 in a BCBL-derived cell line and found that it encodes a cytoplasmic protein whose expression is induced 16-fold by treatment with phorbol ester or sodium butyrate. This protein induction correlates with a significant induction of viral RNA transcripts. Interestingly, under our experimental conditions minimal increases in viral DNA were observed. No antibodies to the ORF26 protein of HHV8 were found in the sera from two human immunodeficiency virus-positive patients with KS as determined by immunoprecipitation analysis. However, antibodies in the sera from the two KS patients immunoprecipitated a 34-kDa protein found in extracts from induced BCBL1 cells that was not recognized by the control sera.