KSHV induces immunoglobulin rearrangements in mature B lymphocytes

Abstract

Kaposi sarcoma herpesvirus (KSHV/HHV-8) is a B cell tropic human pathogen, which is present in vivo in monotypic immunoglobulin λ (Igλ) light chain but polyclonal B cells. In the current study, we use cell sorting to infect specific B cell lineages from human tonsil specimens in order to examine the immunophenotypic alterations associated with KSHV infection. We describe IL-6 dependent maturation of naïve B lymphocytes in response to KSHV infection and determine that the Igλ monotypic bias of KSHV infection in vivo is due to viral induction of BCR revision. Infection of immunoglobulin κ (Igκ) naïve B cells induces expression of Igλ and isotypic inclusion, with eventual loss of Igκ. We show that this phenotypic shift occurs via re-induction of Rag-mediated V(D)J recombination. These data explain the selective presence of KSHV in Igλ B cells in vivo and provide the first evidence that a human pathogen can manipulate the molecular mechanisms responsible for immunoglobulin diversity.

Analysis of KSHV B lymphocyte lineage tropism in human tonsil reveals efficient infection of CD138+ plasma cells

“…Therefore, we employed a method for normalizing infectious dose from donor-to-donor in order to obtain cross-sectional data that was directly comparable (Figure 2A). For each sample we used magnetic sorting to isolate untouched naïve B cells, which are a known susceptible cell type (Totonchy et al, 2018), and infected 1 million naïve B cells with equivalent doses of cell-free KSHV.219 virus. After infection, bound lymphocytes from the magnetic separation were added back to each sample to reconstitute the total lymphocyte environment.…”

“…For our studies, we used cell-free, iSLK-derived KSHV.219 to infect Naïve B lymphocytes followed by reconstitution of the total lymphocyte environment. We also avoided activation of lymphocytes in both the isolation and culture procedures using our previously-characterized CDw32 feeder cell system (Totonchy et al, 2018). To date, no consensus has yet emerged on how to perform tonsil lymphocyte infection studies with KSHV, and how differences in infection and culture procedure influences the resulting data remains to be established.…”

“…Despite the fact that KSHV is lymphotropic and causes pathological lymphoproliferation in vivo , study of de novo KSHV infection in B lymphocytes has historically been difficult (Kang and Myoung, 2017). Resting peripheral B cells and many established B cell-derived cell lines are refractory to KSHV infection (Rappocciolo et al, 2008), but several groups have recently been successful in infecting B lymphocytes derived from human tonsil (Hassman et al, 2011; Myoung and Ganem, 2011a; b; Bekerman et al, 2013; Totonchy et al, 2018; Nicol et al, 2016). KSHV DNA is detectable in human saliva and salivary transmission is thought to be the primary route of person-to-person transmission for KSHV (Casper et al, 2007; Pauk et al, 2000; Casper et al, 2004; Vieira et al, 1997), making the oral lymphoid tissues a likely site for the initial infection of B lymphocytes in a naïve human host.…”

“…The existing studies of KSHV infection in tonsil-derived B cells have explored a limited number of cell surface markers including IgM, immunoglobulin lambda light chains and activation markers on infected cells (Hassman et al, 2011; Nicol et al, 2016; Totonchy et al, 2018). However, no studies to date have comprehensively explored the specific B lymphocyte lineages targeted by KSHV infection in human tonsil specimens.…”

Kaposi sarcoma–associated herpesvirus/human herpesvirus 8–associated lymphoproliferative disorders

“…In vitro models of tonsillar B-cell infection may recapitulate the initial steps following contamination through saliva contact. 8,9 Infection of primary tonsillar cells reveals that KSHV/HHV-8 can initially infect various cellular subtypes with activation of an early and transient prelatent "lytic burst" transcription program. Within a few days, although KSHV/HHV-8 infects both k and l naive B cells, a phenotype shift occurs through reinduction of Rag-mediated V(D)J recombination toward B cells expressing both k and l light chains and, ultimately, only naive IgMl B cells.…”