Immunological and inflammatory features of Kaposi's sarcoma and other Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8-associated neoplasias.

During the last 15 years, virologic and immunologic studies have provided a series of valuable clues on the modalities of gamma-herpesvirus-induced oncogenesis, which do not only consist of the direct subversion of intracellular signaling pathways, leading to a frank neoplastic molecular network in the infected cell, but also rely on viral manipulations of the cellular and cytokine microenvironment, especially in conditions of immunodeficiency in the host. At the virus-host interface, something iniquitous, strikingly favoring the aggressive expansion of human herpesvirus 8-infected lympho-endothelial clones, known as Kaposi's sarcoma, often occurs in different types of immunocompromised patients, able to establish a deleterious "pro-Kaposi's sarcoma" neo-angiogenic inflammatory network. However, these patients may control - or even resolve - the neoplastic burden as soon as an immunologic reassessment restores functional anti-Kaposi's sarcoma immune responses and reconstitutes a proper inflammatory environment. Indeed, the occurrence of iatrogenic Kaposi's sarcoma remissions, after the reduction or switch of immunosuppressive regimens, strongly suggests that the reset of immunologic constraints characterizing the Kaposi's sarcoma onco-pathogenic system may be sufficient to inhibit human herpesvirus 8-positive lympho-endothelial proliferations. Accordingly, immunologic reports all underline the pivotal protective role of anti-human herpesvirus 8 memory T-cells (harmonically, both CD8+ and CD4+ subsets), thus definitely implying a general requirement for an effective, antiviral immuno-inflammatory environment, based on correct and productive interactions between different compartments of dendritic, myeloid, and specific T-cells, in order to achieve and maintain optimal control on human herpesvirus 8-associated antigenic stimulations and Kaposi's sarcoma disease. In this review, we recapitulate some remarkable features about the outstanding immunologic issue raised by human herpesvirus 8-driven neoplastic outgrowths in immunodeficient patients, and in particular, we discuss the emerging view of Kaposi's sarcoma as an atypical neoplastic process, tightly dependent on immune system dynamics. It is conceivable that functional dissection of the specific immune responses, capable to cope with human herpesvirus 8, and further definitions of a global inflammatory profile with protective activity against Kaposi's sarcoma outbreaks, will eventually foster immunologic monitoring protocols during the follow-up of AIDS and posttransplant patients, either preventing or treating human herpesvirus 8-related tumors by multifunctional immunomodulation or prompt development of adoptive immunotherapeutic approaches.