Modulation of Immune System by Kaposi’s Sarcoma-Associated Herpesvirus: Lessons from Viral Evasion Strategies

Kaposi’s sarcoma-associated herpesvirus (KSHV), a member of the herpesvirus family, has evolved to establish a long-term, latent infection of cells such that while they carry the viral genome gene expression is highly restricted. Latency is a state of cryptic viral infection associated with genomic persistence in their host and this hallmark of KSHV infection leads to several clinical–epidemiological diseases such as KS, a plasmablastic variant of multicentric Castleman’s disease, and primary effusion lymphoma upon immune suppression of infected hosts. In order to sustain efficient life-long persistency as well as their life cycle, KSHV dedicates a large portion of its genome to encode immunomodulatory proteins that antagonize its host’s immune system. In this review, we will describe our current knowledge of the immune evasion strategies employed by KSHV at distinct stages of its viral life cycle to control the host’s immune system

Biphasic euchromatin-to-heterochromatin transition on the KSHV genome following de novo infection.

The establishment of latency is an essential step for the life-long persistent infection and pathogenesis of Kaposi's sarcoma-associated herpesvirus (KSHV). While the KSHV genome is chromatin-free in the virions, the viral DNA in latently infected cells has a chromatin structure with activating and repressive histone modifications that promote latent gene expression but suppress lytic gene expression. Here, we report a comprehensive epigenetic study of the recruitment of chromatin regulatory factors onto the KSHV genome during the pre-latency phase of KSHV infection. This demonstrates that the KSHV genome undergoes a biphasic chromatinization following de novo infection. Initially, a transcriptionally active chromatin (euchromatin), characterized by high levels of the H3K4me3 and acetylated H3K27 (H3K27ac) activating histone marks, was deposited on the viral episome and accompanied by the transient induction of a limited number of lytic genes. Interestingly, temporary expression of the RTA protein facilitated the increase of H3K4me3 and H3K27ac occupancy on the KSHV episome during de novo infection. Between 24-72 hours post-infection, as the levels of these activating histone marks declined on the KSHV genome, the levels of the repressive H3K27me3 and H2AK119ub histone marks increased concomitantly with the decline of lytic gene expression. Importantly, this transition to heterochromatin was dependent on both Polycomb Repressive Complex 1 and 2. In contrast, upon infection of human gingiva-derived epithelial cells, the KSHV genome underwent a transcription-active euchromatinization, resulting in efficient lytic gene expression. Our data demonstrate that the KSHV genome undergoes a temporally-ordered biphasic euchromatin-to-heterochromatin transition in endothelial cells, leading to latent infection, whereas KSHV preferentially adopts a transcriptionally active euchromatin in oral epithelial cells, resulting in lytic gene expression. Our results suggest that the differential epigenetic modification of the KSHV genome in distinct cell types is a potential determining factor for latent infection versus lytic replication of KSHV

Deregulation of HDAC5 by Viral Interferon Regulatory Factor 3 Plays an Essential Role in Kaposi's Sarcoma-Associated Herpesvirus-Induced Lymphangiogenesis.

Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiologic agent for Kaposi's sarcoma (KS), which is one of the most common HIV-associated neoplasms. The endothelium is the thin layer of squamous cells where vascular blood endothelial cells (BECs) line the interior surface of blood vessels and lymphatic endothelial cells (LECs) are in direct contact with lymphatic vessels. The KS lesions contain a prominent compartment of neoplastic spindle morphology cells that are closely related to LECs. Furthermore, while KSHV can infect both LECs and BECs in vitro, its infection activates genetic programming related to lymphatic endothelial cell fate, suggesting that lymphangiogenic pathways are involved in KSHV infection and malignancy. Here, we report for the first time that viral interferon regulatory factor 3 (vIRF3) is readily detected in over 40% of KS lesions and that vIRF3 functions as a proangiogenic factor, inducing hypersprouting formation and abnormal growth in a LEC-specific manner. Mass spectrometry analysis revealed that vIRF3 interacted with histone deacetylase 5 (HDAC5), which is a signal-responsive regulator for vascular homeostasis. This interaction blocked the phosphorylation-dependent cytosolic translocation of HDAC5 and ultimately altered global gene expression in LECs but not in BECs. Consequently, vIRF3 robustly induced spindle morphology and hypersprouting formation of LECs but not BECs. Finally, KSHV infection led to the hypersprouting formation of LECs, whereas infection with a ΔvIRF3 mutant did not do so. Collectively, our data indicate that vIRF3 alters global gene expression and induces a hypersprouting formation in an HDAC5-binding-dependent and LEC-specific manner, ultimately contributing to KSHV-associated pathogenesis.IMPORTANCE Several lines of evidences indicate that KSHV infection of LECs induces pathological lymphangiogenesis and that the results resemble KS-like spindle morphology. However, the underlying molecular mechanism remains unclear. Here, we demonstrated that KSHV vIRF3 is readily detected in over 40% of various KS lesions and functions as a potent prolymphangiogenic factor by blocking the phosphorylation-dependent cytosolic translocation of HDAC5, which in turn modulates global gene expression in LECs. Consequently, vIRF3-HDAC5 interaction contributes to virus-induced lymphangiogenesis. The results of this study suggest that KSHV vIRF3 plays a crucial role in KSHV-induced malignancy

Adrenal ganglioneuroma with hepatic metastasis

Ganglioneuroma is the most differentiated tumor of neural crest origin and rarely arises in the adrenal gland. Ganglioneuroma is typically known to be benign, but very rarely can metastasize to distant sites. We report a case of a 31-year-old man with a huge adrenal mass with hepatic metastases

Effectiveness of a village-based intervention for depression in community-dwelling older adults: a randomised feasibility study

Although a focus on late-life depression may help preventing suicide in older adults, many older people, especially those living in rural areas, have relatively low accessibility to treatment. This study examined the feasibility and effectiveness of a village-based intervention for depression targeting older adults living in rural areas. A community-based randomised pilot trial was performed in two small rural villages in South Korea. Two villages were randomly selected and assigned to the intervention or active control group; all older adults living in the two villages (n = 451) were included in the intervention program or received standard Community Mental Health Service (CMHS) care, and the effectiveness of the program was examined using representative samples from both groups (n = 160). The 12-week intervention included case management according to individual risk level and group-based activities. Healthy residents living in the intervention village who played major roles in monitoring at-risk older individuals were supervised by CMHS staff. The score on the Korean version of the Geriatric Depression Scale-Short Form (SGDS-K) was the primary outcome, while social network, functional status, and global cognitive function were secondary outcomes. Linear mixed models including the factors of intervention group, time, and their interaction were used to examine group differences in changes in primary and secondary outcomes from baseline to follow up. Overall, there was no significant group × time interaction with respect to the SGDS-K score, but older individuals with more depressive symptoms at baseline (SGDS-K ≥ 6) tended to have a lower likelihood of progressing to severe depression at post-intervention. The social network was strengthened in the intervention group, and there was a significant group × time interaction (F[df1, df2], 5.29 [1, 153], p = 0.023). This study examined a 12-week village-based intervention for late-life depression in which the CMHS helped village-dwellers deal with late-life depression in their communities. Although the intervention improved social interactions among older adults, it did not reduce depressive symptoms. Further studies including more rural villages and long-term follow up are needed to confirm the effectiveness of this prevention program. NCT04013165 (date: 9 July 2019, retrospectively registered)

A case of isolated metastatic hepatocellular carcinoma arising from the pelvic bone

Reports of metastatic hepatocellular carcinoma (HCC) without a primary liver tumor are rare. Here we present a case of isolated HCC that had metastasized to the pelvic bone without a primary focus. A 73-year-old man presented with severe back and right-leg pain. Radiological examinations, including computed tomography (CT) and magnetic resonance imaging (MRI), revealed a huge mass on the pelvic bone (13×10 cm). He underwent an incisional biopsy, and the results of the subsequent histological examination were consistent with metastatic hepatocellular carcinoma. The tumor cells were positive for cytokeratin (AE1/AE3), hepatocyte paraffin 1, and glypican-3, and negative for CD56, chromogranin A, and synaptophysin on immunohistochemical staining. Examination of the liver by CT, MRI, positron-emission tomography scan, and angiography produced no evidence of a primary tumor. Radiotherapy and transarterial chemoembolization were performed on the pelvic bone, followed by systemic chemotherapy. These combination treatments resulted in tumor regression with necrotic changes. However, multiple lung metastases developed 1 year after the treatment, and the patient was treated with additional systemic chemotherapy

Anti-Wrinkle Effect of Magnesium Lithospermate B from Salvia miltiorrhiza BUNGE: Inhibition of MMPs via NF-kB Signaling

Skin is in direct contact with the environment and therefore undergoes aging as a consequence of environmentally induce damage. Wrinkle formation is a striking feature of intrinsic and photo-induced skin aging, which are both associated with oxidative stress and inflammatory response. The present study was undertaken to identify the mechanisms responsible for the anti-wrinkle effects of MLB, and thus, we investigated whether magnesium lithospermate B (MLB) from Salvia miltiorrhiza BUNGE associated with wrinkle formation caused by intrinsic and extrinsic skin aging using Sprague-Dawley rats aged 5 and 20 months and ultraviolet B (UVB)-irradiated human skin fibroblasts cells, respectively. The results obtained showed that the oral administration of MLB significantly upregulated the level of type I procollagen and downregulated the activities and expressions of matrix-metalloproteinases (MMPs) in rat skin. In fibroblasts, MLB suppressed the transactivation of nuclear factor-kB (NF-kB) and activator protein 1(AP-1), which are the two transcription factors responsible for MMP expression, by suppressing oxidative stress and the mitogen activated protein kinase (MAPK) pathway. Our results show that the antioxidant effect of MLB is due to the direct scavenging of reactive oxygen species (ROS) and its inhibitory effects on NF-kB-dependent inflammation genes, such as, cyclooxygenase-2 and inducible nitric oxide synthase. MLB was found to reverse both age- and UVB-related reductions in skin procollagen levels by suppressing the expressions and activities of NF-kB and AP-1-dependent MMPs by modulating ROS generation and the MAPK signaling pathway. We suggest that MLB potentially has anti-wrinkle and anti-skin aging effects