Relationship of HHV-8 Peripheral Blood Mononuclear Cell Burden to Immunodeficiency, Opportunistic Infections, Response to Therapy, and Stage of Kaposi's Sarcoma

Abstract

Background: Human herpesvirus type 8 (HHV-8) is closely associated with Kaposi's sarcoma (KS). The objectives of these studies were: [1] to determine if HHV-8 burden correlates with degree of underlying immunodeficiency as assessed by lymphocyte subsets, plasma HIV-1 RNA PCR, and evidence of opportunistic infection, [2] to determine if PBMC HHV-8 burden correlates with stage of KS disease, and [3] to determine if PBMC HHV-8 burden might be a useful index of treatment response in Kaposi's sarcoma. Methods: Samples from two retrospective patient groups were analyzed, including PBMC from a cross-section of KS patients treated with modalities ranging from aINF and AZT, to cytotoxic chemotherapeutic agents to radiation therapy, and samples from a cohort of patients with limited cutaneous disease treated with AZT and aINF in a phase I trial. A quantitative competitive DNA PCR assay was developed to quantitate HHV-8 burden, using HHV-8 orf24 target sequences. Using PAGE and Syber-green visualization, this assay detected single copies of the HHV-8 genome, and reproducibly and accurately quantitated as few as 5 copies of HHV-8 per 106 PBMC. Results: HHV-8 burden was not related to CD4 count, total lymphocyte count, or HIV-1 plasma RNA copy number. In contrast HIV-1 RNA was inversely related to CD4 lymphocyte count (p<0.02, Fisher's exact test). No relationship to opportunistic infection overall was seen; however, detectable HHV-8 was found more frequently and at higher copy numbers in patients with evidence of other herpesvirus infections (CMV, HSV, VZV). Therapy with ganciclovir or foscavir was fond to have no effect on PBMC HHV-8 copy number. Patients with only cutaneous disease and without mucosal or visceral involvement (Category I) were found to have low to undetectable(≤2-5×102 copies/106 PBMC) HHV-8 PBMC burden while patients with mucosal disease (Category II) or visceral disease (Category III - including lymph node, lung, gut, and bone marrow) had significantly higher HHV-8 average PBMC burdens (2×103-104 copies/106 PBMC). Treatment with aIFN and AZT or cytotoxic chemotherapy, but not local radiation therapy, reduced HHV-8 burden by up to 80%. Conclusions: HHV-8 PBMC burden is not a reflection of overall immunodeficiency or activity of HIV disease. The differences between patients with mucosal and visceral disease and patients with cutaneous disease may reflect a biological event in the evolution of KS, and PBMC HHV-8 by QC-PCR may be a useful index to follow in treated KS patients.