Retrospective analysis of HHV-8 viremia and cellular viral load in HIV-seropositive patients receiving interleukin 2 in combination with antiretroviral therapy

Absolute quantification of viral DNA: the quest for perfection

In spite of the impressive technical refinement of the PCR technology, new-generation real-time PCR assays still suffer from two major limitations: the impossibility to control both for PCR artifacts (with the important caveat of false-negative results) and for the efficiency of nucleic acid recovery during the preliminary extraction phase of DNA from the biological sample. The calibrator technology developed at the Unit of Human Virology overcomes both of these limitations, leading to a substantially higher degree of accuracy and reproducibility in the quantification, which is especially useful for the measurement of pathogen loads in sequential samples and for the reliable detection of low-copy pathogens.

Kaposi's Sarcoma-associated Herpesvirus Activation of Vascular Endothelial Growth Factor Receptor 3 Alters Endothelial Function and Enhances Infection

Kaposi's sarcoma-associated herpesvirus (KSHV; also known as human herpesvirus 8) is the etiologic agent of Kaposi's sarcoma, an endothelial neoplasm. This gamma-herpesvirus encodes for several unique proteins that alter target cell function, including the virion envelope-associated glycoprotein B (gB). Glycoprotein B has an RGD (Arg-Gly-Asp) motif at the extracellular amino terminus region and binds to the alpha3beta1 surface integrin, which enhances virus entry. We now report that gB can activate the vascular endothelial growth factor receptor 3 (VEGFR-3) on the surface of microvascular endothelial cells and trigger receptor signaling, which can modulate endothelial migration and proliferation. Furthermore, we observed that VEGFR-3 expression and activation enhance KSHV infection and participate in KSHV-mediated transformation. These functional changes in the endothelium may contribute to the pathogenesis of Kaposi's sarcoma and suggest that interventions that inhibit gB activation of VEGFR-3 could be useful in the treatment of this neoplasm.

Antitumour effects of antiretroviral therapy

Infection by human immunodeficiency virus (HIV) is associated with an increased risk of certain tumours, particularly Kaposi's sarcoma, non-Hodgkin's lymphomas and cervical cancer. However, the incidence of these tumours in HIV-infected patients has decreased significantly since the widespread use of highly active antiretroviral therapy (HAART). This effect cannot be solely explained by the ability of these drugs to suppress HIV replication and thereby reconstitute the immune system. Recent studies have shown that inhibitors of the HIV aspartyl protease, which are widely used in HAART, have direct anti-angiogenic and antitumour effects that are unrelated to their antiviral activity. So these drugs might be used to treat cancer in patients who are not infected with HIV.

Epidemiology of HHV-8 infection in HIV-positive patients with and without Kaposi sarcoma: diagnostic relevance of serology and PCR

BACKGROUND

Kaposi's sarcoma (KS) remains the most common neoplasm in HIV-infected patients. Human herpesvirus 8 (HHV-8) infection is etiologically associated with KS. Diagnostic procedures with regard to HHV-8 infection are not routinely performed in HIV-infected patients; diagnostic and prognostic value of HHV-8 serology or PCR are unknown in this setting. Epidemiological data concerning HHV-8 infection of HIV-infected patients in Germany are rare.

OBJECTIVES

To assess prevalence of HHV-8 infection in a cohort of HIV-infected patients with and without KS in Germany and to correlate this to manifestations and clinical course of KS.

STUDY DESIGN

HHV-8 serology was performed in 483 patients in routine care for HIV-infection in northern Germany. HHV-8 DNA was analyzed by PCR in peripheral blood mononuclear cells (PBMC) of 293 patients; in a subgroup multiple samples were analyzed. History and manifestations of KS were recorded.

RESULTS

HHV-8 antibodies were detected using IFT in 91% of 33 patients with KS and 52% of 398 patients without KS. In 36 of 293 (12.3%) patients HHV-8 DNA was detected in PBMC. In general, HHV-8 DNA was not continuously detected when multiple samples from the same patient were analyzed. Patients with KS history were more likely to be PCR positive than those without (45.5% versus 7.8%). In patients with active KS HHV-8 DNA was detected more frequently than in patients with disease remission. HHV-8 DNA was not detected in serologically negative patients. However, three patients with KS history in full remission for several years were seronegative.

CONCLUSIONS

HIV-infected patients were frequently found to be positive for HHV-8 antibodies. The number of patients positive for viral DNA in PBMC was much smaller. Single PCR-examinations were of little value for prognosis, but repeated detection of HHV-8 DNA represents an increased risk of disease activity.

Pathogenesis of Kaposi's sarcoma

Kaposi's sarcoma (KS) is a disease characterized by proliferative vascular lesions, which almost invariably contain the KS-associated herpesvirus (KSHV), also called human herpesvirus 8. KSHV is a lymphotrophic and angiotrophic herpesvirus, whose genome encodes several proteins involved in proliferation, antiapoptotic functions, and inflammation. Most KS spindle cells express latent KSHV genes, but a few express lytic genes, which might be involved in angiogenic and paracrine mechanisms that contribute to KS pathogenesis. A number of tissue culture and mouse models have been established, but a comprehensive system that accurately portrays KS pathogenesis still does not exist.

Calibrated real-time PCR assay for quantitation of human herpesvirus 8 DNA in biological fluids

Accurate laboratory tests for the diagnosis of active human herpesvirus 8 (HHV-8) infection are becoming essential to study the pathogenesis of HHV-8-associated tumors and for the clinical management of HHV-8-infected individuals. We have developed a highly sensitive, calibrated quantitative real-time PCR assay for the measurement of cell-free HHV-8 DNA in body fluids, based on the addition of a synthetic DNA calibrator prior to DNA extraction. The calibrator controls each sample for the presence of PCR inhibitors, determines a cutoff value of sensitivity for negative samples, and normalizes positive samples for the efficiency of DNA recovery. The assay shows a wide dynamic range of detection (between 1 and 10(6) viral genome equivalents/reaction) and a high degree of accuracy even in the presence of high amounts (up to 1 micro g) of human genomic DNA. Moreover, the assay has a very high sensitivity (lower detection limit, 10 genome equivalents/ml) and a high degree of reproducibility and repeatability with a coefficient of variation (CV) of <15 and 23%, respectively. Furthermore, the use of the calibrator improves the accuracy of quantitation and decreases the intersample variability (CV, 9 and 6%, respectively). The sensitivity and specificity of the assay were tested with a series of clinical specimens obtained from patients affected by various HHV-8-related diseases, as well as from a wide number of controls. In conclusion, our calibrated real-time PCR assay provides a reliable high-throughput method for quantitation of HHV-8 DNA in clinical and laboratory specimens.