HCMV pUL135 remodels the actin cytoskeleton to impair immune recognition of infected cells.
Bottom Line: Without immune pressure, laboratory-adapted HCMV strains have undergone genetic alterations.Among these, the deletion of the UL/b' domain is associated with loss of virulence.An independent interaction between pUL135 and talin disrupted cell contacts with the extracellular matrix.
Affiliation: Institute of Infection & Immunity, Cardiff University School of Medicine, Heath Park, Cardiff CF14 4XN, UK. Electronic address: email@example.com.Show MeSH
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Mentions: The levels of protection elicited by pUL135 rivalled those achieved with gpUL141. In a representative chromium release assay, pUL135 reduced specific lysis by 64% at an E:T ratio of 40:1 with the immortalized NKL cell line (Figure 1A). In cytolysis assays, pUL135 also elicited protection against a heterogeneous primary NK cell population, irrespective of whether assays were performed in an allogeneic (Figure 1B) or an autologous setting (Figure 1C). In the autologous assay, pUL135 elicited 49.5% inhibition of NK-cell-mediated cytolysis at an E:T ratio of 100:1. Moreover, using a CD107-mobilization assay, protection was elicited against IFN-α-activated NK cells from 13 different donors. In allogeneic assays, NK cell degranulation of ten bulk cultures was significantly inhibited by pUL135 expression with a mean difference of 36.8% inhibition (Figure 1D). Efficient pUL135-mediated inhibition was also observed in autologous NK degranulation assays with peripheral blood mononuclear cell (PBMC) bulk cultures from three other donors with an average inhibition of 42.2% (Figure 1E). A panel of 57 NK cell clones from two donors were expanded following single-cell sorting (Table 1). In autologous assays, 25 of 57 clones were either unable to kill target cells or not substantially affected by the expression of pUL135. The remaining NK cell clones (56.1%) were all inhibited by pUL135. Although 33% of clones were inhibited by gpUL141, 12.3% were still activated. In contrast, pUL135 was exclusively associated with an inhibitory response in this series of experiments. In addition to direct killing of target cells by cell-mediated cytotoxicity, inflammatory cytokines released by NK cells play a crucial role in suppressing virus replication; IFN-γ expression was suppressed when NK cells were cocultured with targets expressing either pUL135 or gpUL141 in comparison to vector control (Figure 1F). NK activation requires the establishment of cell:cell contact culminating in formation of an IS, and UL135 reduced the efficiency of NK cells adhesion to fibroblast targets (Figure 1G).
Affiliation: Institute of Infection & Immunity, Cardiff University School of Medicine, Heath Park, Cardiff CF14 4XN, UK. Electronic address: firstname.lastname@example.org.