| Background: Human immunodeficiency virus type 1 (HIV-1) infection significantly increases the risk of Kaposi's sarcoma (KS) occurrence in individuals infected with Kaposi's sarcoma-associated herpesvirus (KSHV). KSHV infection appeared to be necessary but some cofactors also played important roles in KS pathogenesis. We and others identified that HIV-1 particles, soluble regulatory proteins Tat, and inflammatory cytokines released by infected cells could modulate the lytic cycle replication of KSHV.Objective: The objective of the current study was to determine whether overexpression of HIV-1 viral infectivity factor (Vif) mediated by recombinant lentivirus or adenovirus could influence the lytic cycle replication of KSHV in primary effusion lymphoma (PEL) cell lines.Methods: The recombinant lentivirus or adenovirus containing HIV-1 Vif gene was first packaged, respectively, and the viral titer was checked by observing the expression of green fluorescent protein (GFP). The infection efficiency of recombinant virus at different MOIs in target cell (BCBL-1 cells) was tested according to the expression of GFP and Vif protein. After infection with recombinant virus at an appropriate MOI, the mRNA transcription and protein expression of KSHV in BCBL-1 cells were detected by RT-PCR and Western blot, respectively. To examine the effect of Vif expression on KSHV virion release, KSHV DNA in BCBL-1 cells culture supernatant was detected by PCR, the infection efficiency of Vero cells by KSHV virion from the supernatant was also checked. Furthermore, to explore the potential molecular mechanism underlying the effect of Vif on KSHV replication, we tested both ORF50 and ORF73 promoter activity and detected the intracellular signaling pathways, respectively.Results: The recombinant lentivirus and adenovirus with high titer were constructed successfully. BCBL-1 cells could be efficiently infected by the recombinant virus at the MOI of 1, and Vif protein was readily expressed in these cells. The mRNA transcription levels of both T1.1 (lytic gene of KSHV) and ORF26 (encoding KSHV minor capsid protein) in Vif-overexpressed BCBL-1 cells were significantly decreased compared with the corresponding control. Moreover, the protein expression of replication and transcription activator (Rta) and viral interleukin 6 (vIL-6) were down-regulated also. Besides, overexpression of Vif could inhibit the release of the infectious KSHV virion. Mechanistic studies showed that overexpression of Vif resulted in decreased ORF50 promoter activity, interestingly, the ORF73 promoter activity was also attenuated in some degree. The phosphorylation of ERK and GSK-3βwere down-regulated in Vif-overexpressed BCBL-1 cells.Conclusions: Overexpression of Vif in BCBL-1 cells not only inhibited the lytic cycle replication of KSHV, but also repressed the release of the infectious KSHV virion. The inhibition was associated with the regulation of KSHV promoter activity by Vif. ERK MAPK and PI3K/Akt/GSK-3βpathways may play a partial role in modulation of Vif-induced inhibition of KSHV replication. These findings suggest that Vif may participate in the immune escape by inhibiting KSHV lytic replication and play a potential role in KSHV latency infection and KS pathogenesis.Keywords: Vif, KSHV, lytic cycle replication, lentivirus, adenovirus... |
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