Summary Although pathogens must infect differentiated host cells that exhibit substantial diversity, documenting the consequences of infection against this heterogeneity is challenging. Single cell mass cytometry permits deep profiling based on combinatorial expression of surface and intracellular proteins. We used this method to investigate varicella-zoster virus (VZV) infection of tonsil T cells, which mediate viral transport to skin. Our results indicate that VZV induces a continuum of changes regardless of basal phenotypic and functional T cell characteristics. Contrary to the premise that VZV selectively infects T cells with skin trafficking profiles, VZV infection altered T cell surface proteins to enhance or induce these properties. Zap70 and Akt signaling pathways that trigger such surface changes were activated in VZV-infected naïve and memory cells by a T cell receptor (TCR)-independent process. Single cell mass cytometry is likely to be broadly relevant for demonstrating how intracellular pathogens modulate differentiated cells to support pathogenesis in the natural host.

Herpesvirus entry functions of the conserved glycoproteins gB and gH-gL have been delineated, but their role in regulating cell-cell fusion is poorly understood. Varicella-zoster virus (VZV) infection provides a valuable model for investigating cell-cell fusion because of the importance of this process for pathogenesis in human skin and sensory ganglia. The present study identifies a canonical immunoreceptor tyrosine-based inhibition motif (ITIM) in the gB cytoplasmic domain (gBcyt) and demonstrates that the gBcyt is a tyrosine kinase substrate. Orbitrap mass spectrometry confirmed that Y881, central to the ITIM, is phosphorylated. To determine whether the gBcyt ITIM regulates gB/gH-gL-induced cell-cell fusion in vitro, tyrosine residues Y881 and Y920 in the gBcyt were substituted with phenylalanine separately or together. Recombinant viruses with these substitutions were generated to establish their effects on syncytia formation in replication in vitro and in the human skin xenograft model of VZV pathogenesis. The Y881F substitution caused significantly increased cell-cell fusion despite reduced cell-surface gB. Importantly, the Y881F or Y881/920F substitutions in VZV caused aggressive syncytia formation, reducing cell-cell spread. These in vitro effects of aggressive syncytia formation translated to severely impaired skin infection in vivo. In contrast, the Y920F substitution did not affect virus replication in vitro or in vivo. These observations suggest that gB modulates cell-cell fusion via an ITIM-mediated Y881 phosphorylation-dependent mechanism, supporting a unique concept that intracellular signaling through this gBcyt motif regulates VZV syncytia formation and is essential for skin pathogenesis.fusogenicity | mutagenesis | polykaryocyte | virulence T he alphaherpesvirus varicella-zoster virus (VZV) is a human pathogen that spreads from mucosal epithelial sites of initial infection to skin via a T cell-associated viremia (1), causing varicella (chicken pox). Viremia and cutaneous infection enable transfer of VZV to sensory nerve ganglia and establishment of latency in neurons (2). Zoster (shingles) is caused by VZV reactivation from latently infected neurons and can lead to the debilitating condition of postherpetic neuralgia. Live attenuated VZV vaccines are effective against varicella and zoster but are not recommended for immunocompromised patients.Enveloped viruses from several families, including the Herpesviridae, require fusion with cellular membranes for virion entry, and in some cases induce syncytia through cell-cell fusion (2-5). Little is known about the functional role of syncytia during pathogenesis. VZV is a valuable model pathogen for investigating this process because natural infection of the human host involves formation of multinucleated polykaryocytes in skin and fusion of neurons and satellite cells in sensory ganglia (2, 6). In addition, VZV produces syncytia during replication in vitro and triggers fusion between differentiated cells in human skin and dorsal root ganglion xenograf...

Varicella-zoster virus (VZV) is a human α-herpesvirus that causes varicella (chickenpox) during primary infection and zoster (shingles) upon reactivation. Like other viruses, VZV must subvert the intrinsic antiviral defenses of differentiated human cells to produce progeny virions. Accordingly, VZV inhibits the activation of the cellular transcription factors IFN regulatory factor 3 (IRF3) and signal transducers and activators of transcription 1 (STAT1), thereby downregulating antiviral factors, including IFNs. Conversely, in this study, we found that VZV triggers STAT3 phosphorylation in cells infected in vitro and in human skin xenografts in SCID mice in vivo and that STAT3 activation induces the anti-apoptotic protein survivin. Small-molecule inhibitors of STAT3 phosphorylation and survivin restrict VZV replication in vitro, and VZV infection of skin xenografts in vivo is markedly impaired by the administration of the phospho-STAT3 inhibitor S3I-201. STAT3 and survivin are required for malignant transformation caused by γ-herpesviruses, such as Kaposi's sarcoma virus. We show that STAT3 activation is also critical for VZV, a nononcogenic herpesvirus, via a survivin-dependent mechanism. Furthermore, STAT3 activation is critical for the life cycle of the virus because VZV skin infection is necessary for viral transmission and persistence in the human population. Therefore, we conclude that takeover of this major cell-signaling pathway is necessary, independent of cell transformation, for herpesvirus pathogenesis and that STAT3 activation and up-regulation of survivin is a common mechanism important for the pathogenesis of lytic as well as tumorigenic herpesviruses.T he life cycle of varicella-zoster virus (VZV) in the human host depends on its tropism for T cells, skin, and neurons within sensory ganglia (1). As shown in the SCID mouse model of VZV pathogenesis, infected human T cells transport the virus to epidermal cells in human skin xenografts and to neural cells in dorsal root ganglia xenografts (2, 3). VZV establishes latency in sensory ganglia; upon reactivation, the virus migrates to the skin via axonal transport to cause zoster.VZV modulates several signaling pathways to replicate efficiently in vitro, and these regulatory effects are especially important in differentiated skin cells infected in vivo. VZV interferes with IFN induction and signaling via inhibition of IFN regulatory factor 3 (IRF3), NFκB, and STAT1 in vitro and in skin (4, 5). However, the pathogenesis of VZV skin infection requires a mechanism to overcome the constitutive IFNα expression by epidermal cells that accounts for the 10-to 21-d interval between VZV transfer into skin and the appearance of lesions at skin surfaces (6). How VZV overcomes this cutaneous IFN barrier and produces skin vesicles is not known.The STATs are ubiquitous transcription factors with many cellular functions and are at the junction of several cytokinesignaling pathways (7,8). Of the seven STAT family proteins, STAT3 exerts widespread effects through transcri...

T and B cell immunity to mumps was detected in adults at least 10 years after immunization. Except for IFN-gamma release, responses in vaccinated adults paralleled those observed in naturally immune individuals.

Measles-specific T-cell responses were sustained at 5-10 years of age regardless of age at time of primary measles immunization. Neutralizing antibody concentrations were lower in cohorts given the first vaccine dose at 6 months of age and in the presence of PAs; however, responses could be boosted by subsequent doses. Starting measles vaccination at <12 months of age may be beneficial during measles outbreaks or in endemic areas.