Dendritic cells (DC) are critical for stimulation of naive T cells. Little is known about the effect of herpes simplex virus type 2 (HSV-2) infection on DC structure or function or if the observed effects of HSV-1 on human DC are reproduced in murine DC. Here, we demonstrate that by 12 h postinfection, wild-type (wt) HSV-2 (186) abortively infected murine bone marrow-derived DC and induced early cell death compared to UV-inactivated HSV-2 or mock-infected DC. HSV-2-induced loss of DC viability was more rapid than that induced by HSV-1 and was due, in part, to apoptosis, as shown by TEM, caspase-3 activation, and terminal deoxynucleotidyl transferase-mediated dCTP biotin nick end labeling. HSV induced type-specific changes in the murine DC immunophenotype. At 12 h postinfection, wt HSV-2 upregulated DC major histocompatibility complex (MHC) class II expression, and in contrast to UV-inactivated HSV-2, downregulated expression of MHC class I, but it had no effect on surface CD40, CD80, or CD86. Wt HSV-1 (MC-1) induced only CD40 upregulation. More-profound effects on the DC immunophenotype were observed in HSV-2-infected neonatal DC. Wt HSV of either serotype impaired murine DC-induced T-cell alloproliferation and lipopolysaccharideinduced DC interleukin-12 secretion. Thus, there are marked differences in the levels of HSV-induced cytolysis in DC according to the HSV serotype, although HSV-2 displays immunomodulatory effects on the DC immunophenotype and function similar to those of HSV-1.Dendritic cells (DC) play a key role in the induction of the primary cellular immune response to intracellular pathogens like herpes simplex virus (HSV), as they are the main cell type that stimulates naive T cells in the draining lymph nodes (23). The strength and character of the antigen-specific T-cell response are determined by factors such as the level of costimulatory molecule (B-7) expression and the density of antigen expressed on the surfaces of DC (1, 33). DC are also thought to be the major source of interleukin-12 (IL-12) (31), which has been demonstrated to play a pivotal role in the differentiation of naive CD4 ϩ T cells into type 1 T helper (Th1) cells (18), although recent studies suggest that IL-12 produced by DC is required for optimal T-cell gamma interferon production rather than for CD4 ϩ -T-cell polarization (26). HSV type 1 (HSV-1) infection of adult human DC derived from peripheral blood monocytes (MoDC) has been shown by a number of groups (15,19,27) to impair costimulatory molecule upregulation of immature DC. However, the timing and degree of this impairment and the presence or absence of associated effects on major histocompatibility complex (MHC) class I (MHC-I) and MHC-II molecule expression were different, possibly due to differences in the types of HSV-1 strain used. Infection of immature MoDC with a disabled infectious single-cycle mutant (DISC-HSV-1-GFP) inhibited DC maturation (as shown by downregulation of costimulatory molecules) and induced marked downregulation of MHC-I expression, attributed...

The first weeks of life are characterized by immune tolerance and increased susceptibility to intracellular pathogens. The neonatal adaptive response to HSV is attenuated compared with adult control models in humans and mice. T Regulatory cells (Tregs) control autoimmunity and excessive immune responses to infection. We therefore compared Treg responses in the draining lymph nodes (LN) of HSV-infected neonatal and adult C57BL/6 mice with the effect of Treg depletion/inactivation by anti-CD25 (PC61) treatment before infection on Ag-specific T cell effector responses at this site. There was a small, but significant increase in the frequency of CD4+Foxp3+ Tregs at day 3 postinfection (p.i.) in the LN of neonatal and adult mice, compared with age-matched mock-infected controls. Depletion of Tregs before HSV infection significantly enhanced HSV-specific CD8+ T cell cytotoxicity in vivo, cell number, activation, and granzyme B expression 4 days p.i. only in neonatal mice, and significantly enhanced CD8+ and CD4+ T cell IFN-γ responses in both infected adults and neonates. Treg depletion also reduced the titer of infectious virus in the draining LN and nervous system of infected neonates on days 2 and 3 p.i. Treg suppression of the neonatal CTL response p.i. with HSV was associated with increased expression of TGF-β in the draining LN at day 4 p.i. compared with uninfected neonates, but IL-10 was increased in infected adults alone. These experiments support the notion that the newborn primary T cell effector responses to HSV are suppressed by Tregs.

The role individual skin dendritic cell (DC) subsets play in the immune response to HSV remains unclear. We investigated the effect of HSV on DC virus uptake, viability, and migration after cutaneous infection in vitro and in vivo. HSV increased the emigration of skin DCs from whole skin explants over 3 d postinfection (p.i.) compared with mock controls, but the kinetics of emigration was influenced by the skin DC subset. Uninfected (bystander) Langerhans cells (LCs) were the major emigrant DC subset at 24 h p.i., but thereafter, large increases in infected CD103+langerin+ dermal DC (dDC) and uninfected langerin− dDC emigration were also observed. LC infection was confirmed by the presence of HSV glycoprotein D (gD) and was associated with impaired migration from cultured skin. Langerin+ dDC also expressed HSV gD, but infection did not impede migration. We then followed the virus in live MacGreen mice in which LCs express GFP using a fluorescent HSV-1 strain by time-lapse confocal microscopy. We observed a sequential infection of epidermal cells, first in keratinocytes and epidermal γδ T cells at 6 h p.i., followed by the occurrence of HSVgD+ LCs at 24 h p.i. HSV induced CCR7 upregulation on all langerin+ DC, including infected LCs, and increased production of skin TNF-α and IL-1β. However, a large proportion of infected LCs that remained within the skin was apoptotic and failed to downregulate E-cadherin compared with bystander LCs or mock controls. Thus, HSV infection of LCs is preceded by infection of γδ T cells and delays migration.

Foxp3+ regulatory T cells (Tregs) have an essential role in immune and allograft tolerance. However, in both kidney and liver transplantation in humans, FOXP3+ Tregs have been associated with clinical rejection. Therefore, the role and function of graft infiltrating Tregs have been of great interest. In the studies outlined, we demonstrated that Foxp3+ Tregs were expanded in tolerant kidney allografts and in draining lymph nodes in the DBA/2 (H‐2d) to C57BL/6 (H‐2b) mouse spontaneous kidney allograft tolerance model. Kidney allograft tolerance was abrogated after deletion of Foxp3+ Tregs in DEpletion of REGulatory T cells (DEREG) mice. Kidney allograft infiltrating Foxp3+ Tregs (K‐Tregs) expressed elevated levels of TGF‐β, IL‐10, interferon gamma (IFN‐γ), the transcriptional repressor B lymphocyte‐induced maturation protein‐1 (Blimp‐1) and chemokine receptor 3 (Cxcr3). These K‐Tregs had the capacity to transfer dominant tolerance and demonstrate donor alloantigen‐specific tolerance to skin allografts. This study demonstrated the crucial role, potency and specificity of graft infiltrating Foxp3+ Tregs in the maintenance of spontaneously induced kidney allograft tolerance.