Reflections on the interpretation of heterogeneity and strain differences based on very limited PCR sequence data from Kaposi's sarcoma-associated herpesvirus genomes

Abstract

Background and PurposeA human gamma class herpesvirus within the rhadinovirus family known as Kaposi's sarcomaassociated herpesvirus (KSHV) or human herpesvirus 8 (HHV8) is now fully accepted as the etiological agent of both Kaposi's sarcoma (KS) and primary effusion lymphoma (PEL), as well as of some cases of multicentric Castleman's didease (MCD). The rates of these diseases are greatly increased in certain AIDS subpopulations (epidemic form), less so in organ transplant patients (iatrogenic form), and they also occur in rare non-AIDS associated cases, usually in elderly men (classical form). KSHV DNA can be detected in virtually all KS lesions and PEL cell lines, and in many MCD biopsies, and often also in PBMC or saliva from these same patients, from asymptomatic dual HIV and KSHV seropositive AIDS patients, and in febrile children in Africa undergoing primary KSHV infections. However, except in subSaharan Africa (>50%) and parts of the Mediterranean and Middle East (15%), most human populations show only 1 to <3% seropositivity rates and KSHV DNA is rarely detectable in PBMC and saliva samples from healthy individuals.The purpose of this review is two-fold, 1) to critically evaluate controversial claims linking KSHV to novel disease conditions; and 2) to evaluate claims linking pathological significance to specific sequence variants of KSHV. Our perspective is based on extensive experience with PCR DNA sequencing of both constant and variable gene regions at multiple loci from KSHV (and human cytomegalovirus [HCMV]) in clinical samples obtained from ethnically and geographically diverse human populations. KSHV genomes display significant levels of genetic polymorphism that are both interesting and informative. Variability observed within the most commonly employed ORF26 PCR locus will be evaluated based on the results presented in the accompanying paper, which describes the detection of eight distinct clustered nucleotide polymorphism patterns in an expanded version of this locus (Zong and Hayward, 2007). The significance of KSHV subtypes and DNA sequence polymorphisms will be assessed in the context of global clustering patterns and the overall levels of variability observed Corresponding Author: Gary S. Hayward, Phone: (410) Fax: (410) 955-8685, E Mail: ghayward@jhmi.edu. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access Use of PCR DNA Data in Clinical and Epidemiological Studies of KSHV InfectionEvidence for KSHV infection is usually based upon detection of antibodies by serological assays or detection of viral DNA by PCR or both. However, ther...

Genotypic distribution of HHV-8 in AIDS individuals without and with Kaposi sarcoma

“…[25,27,45,46] Nevertheless, prevalence of detectable HHV-8 salivary shedding in the group without KS was 14.1% (as assessed herein by means of real-time PCR from ORF 73), which is close to the prevalence rates reported in previous studies, that is, ranging from 9.5 to 11%. [45,46] In the saliva samples from those non-KS individuals, our protocol using 3 sets of primers together (i.e., VR1, VR2, and K1) allowed us to genotype 32.1% of the samples, at even low viral load. In the PBMC samples from individuals with KS disease, our genotyping protocol reached 89.2% (33/37).…”

“…1B, gray area). In fact, most studies consistently demonstrate that co-infection by different HHV-8 genotypes is extremely rare, [26,46,50–52] thus supporting that the currently detected recombinant forms do not originate from new events, but they represent previous circulating recombinant forms. [2,49] …”

Strain Variation and Disease Severity in Congenital Cytomegalovirus Infection

“…Testing of serial samples collected from the patients revealed fluctuation in the genotype abundance although the sequence itself did not change, again confirming the stability of CMV genes. The authors appropriately noted that PCR amplification may result in artificial recombinants and cautioned about problems in interpretation of deep sequencing experiments (64,65). …”

Seroprevalence of Kaposi's sarcoma‐associated herpesvirus and risk factors in Xinjiang, China

“…KSHV has different subtypes [Zong et al, 2007]. These subtypes have distinct geographic distributions, and appear to migrate with the human populations.…”