The infection of murine gammaherpesvirus-68 delays the early embryonic development of zebrafish

Zebrafish is a model animal for aquaculture as well as bio-medicine. Murine gamma-herpesvirus 68 (MHV68) is widely regarded as a model for the study of human gamma herpesviruses such as Kaposi's sarcoma-associated herpesvirus (KSHV). In this study, the infection of MHV68 on zebrafish was investigated through incubating fertilized zebrafish eggs with MHV68. The development of zebrafish delayed or stopped at early stage separately when the zebrafish eggs were incubated with MHV68 at different dose for 2 h. The lytic gene of MHV68, including ORF65, RTA and ORF57, were detected in the genome of larvae hatched from the infected eggs. The transcription of the latent gene LANA but not of these lytic genes was detected by RT-PCR. The mRNA level of growth factor TGF-β1, but not of FGF3, was obviously decreased in the larvae from the MHV68 treated eggs. The mRNA levels of cytokines, such as IFNφ3, ISG15 and TNFα, varied post MHV68 infection; however, the transcription of the cytosolic DNA sensors, including DDX41, DHX9 and cGAS, did not change significantly. Moreover, the data generated in zebrafish cell line demonstrated that MHV68 could infect ZF4 cells. All the data support the conclusion that MHV68 could infect zebrafish embryo in the egg envelope and go into latent infection, which will delay the development of the embryos through some unknown mechanism

Glycosylation of KSHV Encoded vGPCR Functions in Its Signaling and Tumorigenicity

Kaposi’s sarcoma-associated herpesvirus (KSHV) is a tumor virus and the etiologic agent of Kaposi’s Sarcoma (KS). KSHV G protein-coupled receptor (vGPCR) is an oncogene that is implicated in malignancies associated with KHSV infection. In this study, we show that vGPCR undergoes extensive N-linked glycosylation within the extracellular domains, specifically asparagines 18, 22, 31 and 202. An immunofluorescence assay demonstrates that N-linked glycosylation are necessary for vGPCR trafficking to the cellular membrane. Employing vGPCR mutants whose glycosylation sites were ablated, we show that these vGPCR mutants failed to activate downstream signaling in cultured cells and were severely impaired to induce tumor formation in the xenograph nude mouse model. These findings support the conclusion that glycosylation is critical for vGPCR tumorigenesis and imply that chemokine regulation at the plasma membrane is crucial for vGPCR mediated signaling

Identification and characterization of MAVS from black carp Mylopharyngodon piceus

MAVS (mitochondria antiviral signaling protein) plays an important role in the host cellular innate immune response against microbial pathogens. In this study, MAVS has been cloned and characterized from black carp (Mylopharyngodon piceus). The full-length cDNA of black carp MAVS (bcMAVS) consists of 2352 nucleotides and the predicted bcMAVS protein contains 579 amino acids. Structural analysis showed that bcMAVS is composed of functional domains including an N-terminal CARD, a central proline-rich domain, a putative TRAF2-binding motif and a C-terminal TM domain, which is similar to mammalian MAVS. bcMAVS is constitutively transcribed in all the selected tissues including gill, kidney, heart, intestine, liver, muscle, skin and spleen; bcMAVS mRNA level in intestine, liver, muscle increased but decreased in spleen right after GCRV or SVCV infection. Multiple bands of bcMAVS were detected in western blot when it was expressed in tissue culture, which is similar to mammalian MAVS. Immunofluorescence assay determined that bcMAVS is a mitochondria protein and luciferase reporter assay demonstrated that bcMAVS could induce zebrafish IFN and EPC IFN expression in tissue culture. Data generated in this manuscript has built a solid foundation for further elucidating the function of bcMAVS in the innate immune system of black carp. (C) 2015 Elsevier Ltd. All rights reserved