Influence of Human and Viral IL-6 on KSHV Infection in Human Tonsil Lymphocytes

Background: Infection of B cells by lymphotropic gamma-herpesvirus Kaposi sarcoma-associated herpesvirus (KSHV) causes Multicentric Castleman Disease, Primary Effusion Lymphoma, and the newly-identified inflammatory syndrome designated KICS.1 Despite proven connections to lymphoproliferative disorders, little is known about how KSHV invades the human immune system or the early events governing infection in B lymphocytes. IL-6 signaling plays a critical role in KSHV-mediated disease, where elevated hIL-6 levels are positively associated with KSHV viral load and disease progression.2 This dynamic is even more complex due to the co-existence of human IL-6 (hIL6) and KSHV-encoded viral IL-6 (vIL6) in these diseases. Although the impact of IL-6 signaling is well-established in the context of KSHV disease, its role in the early stages of infection in B cells remains undefined.

Hypothesis: We hypothesize that hIL6 and vIL6 play critical roles in the early stages of KSHV infection in B cells and the establishment of KSHV-infected plasma cells.

Method: In this study, we use ex vivo infection of tonsil lymphocytes with recombinant KSHV as a model to investigate early infection events. Our main objective is to utilize multiple approaches, including molecular knockout of vIL6 from the KSHV genome, knockout of human IL6 through CRISPR-Cas9 gene editing as well as recombinant proteins and neutralizing antibodies to manipulate signaling from hIL6 and vIL6. We will examine how these manipulations affect the viability, differentiation, and proliferation of tonsil lymphocyte cultures as well as the magnitude and distribution of KSHV infection via flow cytometry analysis.

Results: In our investigations, successful knockdown of hIL-6 in non-B cells resulted in reduced B cell viability, with IL6 knockdown correlating with decreased B cell survival in the cultures as well as decreased KSHV infection, particularly in plasma cells. Neutralization of hIL6 reduced proliferation in B cell cultures and this effect was more profound when hIL6 was neutralized in the context of infection with the vIL6 mutant virus. Moreover, hIL-6 neutralization had little effect on total infection in the context of WT KSHV, but vIL6 mutant virus had a reduced ability to establish infection when hIL6 was neutralized. We will also present results showing the effects of vIL6 and hIL6 on B cell differentiation in response to KSHV infection. Overall, our findings suggest that hIL6 and vIL6 have complementary but separable roles in the early stages of KSHV infection in B cells.

References:

1. Thakker S, Verma SC. Co-infections and Pathogenesis of KSHV-Associated Malignancies. Front Microbiol. 2016;7. Accessed July 20, 2023. https://www.frontiersin.org/articles/10.3389/fmicb.2016.00151

2. N, Totonchy J. Cytokine-Targeted Therapeutics for KSHV-Associated Disease. Viruses. 2020;12(10):1097. doi:10.3390/v12101097