Suppression of DC-SIGN and gH Reveals Complex, Subset-Specific Mechanisms for KSHV Entry in Primary B Lymphocytes

Kaposi sarcoma-associated herpesvirus (KSHV) is the causative agent of multiple cancers in immunocompromised patients including two lymphoproliferative disorders associated with KSHV infection of B lymphocytes. Despite many years of research into the pathogenesis of KSHV associated diseases, basic questions related to KSHV molecular virology remain unresolved. One such unresolved question is the cellular receptors and viral glycoproteins needed for KSHV entry into primary B lymphocytes. In this study, we assess the contributions of KSHV glycoprotein H (gH) and the cellular receptor DC-SIGN to KSHV infection in tonsil-derived B lymphocytes. Our results show that (1) neither KSHV-gH nor DC-SIGN are essential for entry into any B cell subset, (2) DC-SIGN does play a role in KSHV entry into tonsil-derived B cells, but in all B cell subtypes alternative entry mechanisms exist, (3) KSHV-gH can participate in KSHV entry into centrocytes via a DC-SIGN independent entry mechanism, and (4) in the absence of KSHV-gH, DC-SIGN is required for KSHV entry into centrocytes. Our results provide a first glimpse into the complexity of KSHV entry in the lymphocyte compartment and highlight that multiple subset-dependent entry mechanisms are employed by KSHV which depend upon multiple cellular receptors and multiple KSHV glycoproteins

Establishing the Role of DC-SIGN and Glycoprotein H for KSHV Entry in B Lymphocytes

Kaposi sarcoma-associated herpesvirus, also known as KSHV or HHV-8, is an emerging pathogen and the causative agent of multiple cancers in immunocompromised patients. KSHV is known to cause four types of malignancies: endothelial-based Kaposi Sarcoma (KS), two rare B cell- based lymphomas; Primary effusion lymphoma, Multicentric Castleman’s disease and a recently characterized inflammatory disorder called KSHV-associated inflammatory cytokine syndrome(KICS). Unfortunately, all of the diseases associated with KSHV infection are fatal, and to this day there is no known cure. The purpose of this study is to understand the viral entry process of KSHV in tonsil-derived B lymphocytes. This study will particularly explore the role of KSHV glycoprotein gH and cell surface receptor DC-SIGN. The first aim of this project will investigate whether the cell surface receptor, DC-SIGN, is required for viral entry of KSHV on tonsillar B lymphocytes. Various approaches will be performed. First, characterization of tonsillar B lymphocytes subsets that express DC-SIGN will take place via flow cytometry followed by analysis on whether KSHV can infect DC-SIGN+ or DC-SIGN- B cells. Second, manipulation of DC-SIGN will be performed utilizing a Neutralizing antibody (anti- DC-SIGN), to observe the change in KSHV infection on tonsillar B lymphocytes. Lastly, a DC- SIGN depletion strategy will be performed to vigorously answer the question of whether DC- SIGN is required for KSHV entry. The second aim that will be addressed is whether the KSHV glycoprotein H (gH) is required for entry into tonsil derived B lymphocytes. In vitro infection of tonsil derived B lymphocytes with a mutant KSHV virus that lacks gH, but retains all the other essential KSHV glycoproteins (KSHV-∆gH) will be performed and analyzed via flow cytometry. We will also combine these approaches with the KSHV-∆gH mutant virus in order to determine whether manipulation of DC-SIGN affects entry of this mutant into B lymphocytes. This study will help understand the initial modes of KSHV transmission in tonsillar B lymphocytes which is relatively understudied in the field and pave the way for the development of future therapeutics to prevent KSHV transmission