Preparation of stable target cells for anti-herpes simplex virus cytotoxic T lymphocytes

Using an avirulent strain of herpes simplex virus (HSV), SKa, and a methylcholanthrene induced sarcoma cell line, Meth A cells, we have developed a reliable target cell system for detection of cell-mediated cytotoxicity directed against HSV-infected cells. SKa-infection in Meth A produced no progeny virus but induced HSV-specific surface antigens as revealed by radioimmunoassay using 125I-labeled HSV antibody. Spontaneous release of 51Cr from the SKa-infected Meth A cells was no more than that from uninfected control cells but a strong spontaneous 51Cr release was produced in Meth A cells infected with KOS, a virulent strain which produced a progeny virus in Meth A and was lytic for the cells. When used as a target, SKa-infected Meth A cells could detect HSV-specific cytotoxicity by spleen and lymph node lymphocytes of mice immunized with SKa and KOS. This system also detected effector cytotoxic lymphocytes stimulated in vitro by mixed cultures of immune spleen cells and KOS-infected Meth A cells. Thus, the system should be valuable in studies of cell-mediated cytotoxicity directed against HSV-infected cells.     

Induction of cytotoxic T lymphocytes against herpes simplex virus type i: role of accessory cells and amplifying factor

Spleen cells from mice primed with herpes simplex virus type 1 (HSV-1) could be induced to differentiate into cytotoxic T lymphocytes (CTL) by in vitro culture with infectious HSV-1 but not by heat-inactivated virus. Induction of CTL failed to occur if the spleen cells were depleted of adherent cells by passage over columns of nylon wool before culture with virus. The CTL response could be restored by adding normal syngeneic peritoneal cells (PC) or L cell fibroblasts but not by allogeneic PC or BALB/c 3T3 fibroblasts. Thus, the induction of HSV-1-specific CTL was H-2 restricted. The response of HSV-1-stimulated nylon wool-depleted spleen cells could also be restored by adding amplifying factor (AF) produced in 24 hr mixed lymphocyte cultures. The addition of AF to nondepleted spleen cells also permitted the generation of CTL with heat-inactivated HSV-1 as a viral stimulant. Our results indicated that induction of a HSV-1 CTL response requires two signals, one provided by virus and a second, presumably nonspecific, by helper T cells. It was suggested that only the helper cells require H-2 restriction and need to be presented virus in the context of a macrophage.     

Induction of I region-restricted hapten-specific cytotoxic T lymphocytes.

Murine cytotoxic T lymphocytes (CTL) reactive to TNP-conjugated syngeneic target cells do lyse to a moderate but significant extent TNP-conjugated, I region compatible but H-2K or H-2D region incompatible target cells. Antibody inhibition experiments and "cold inhibition" experiments indicate that some CTL clones recognize TNP-conjugated targets in association with syngeneic I region determinants independently of H-2K or H-2D gene products. The data suggest that besides TNP-conjugated H-2K or H-2D gene products, in principle, also TNP-conjugated I region determinants do stimulate TNP-specific CTL precursor cells and act as target antigens of TNP-specific CTL.     

Heteroconjugate antibodies enhance cell-mediated anti-herpes simplex virus immunity

Impaired cell-mediated immunity predisposes individuals to severe systemic HSV infections. A potential approach for enhancing antiviral immunity is to alter the specificity of T cells and NK cells so that they become cytotoxic against HSV. We describe here the use of heteroconjugate antibodies to augment the killing of HSV-infected cells. Two different types of heteroconjugate antibodies were used: 1) CD3-specific mAb, covalently linked to HSV-specific mAb (e.g., anti-CD3 x anti-HSV-1 glycoprotein C); 2) FcR-specific mAb linked to HSV-specific mAb (e.g., anti-Fc gamma RIII x anti-HSV-1 glycoprotein D). Whereas freshly isolated, PBL were not cytotoxic against HSV-infected target cells in a 5-h 51Cr-release assay, co-incubation with either heteroconjugate resulted in significant cytotoxicity. In vitro activated PBL (anti-CD3 + IL-2) also became more potent killers of HSV-infected cells in the presence of each heteroconjugate. The specificity of anti-CD3 x anti-HSV-1 and anti-Fc gamma RIII x anti-HSV-1 gD for enhancing T cell and NK cell immunity, respectively, was confirmed by using cloned, homogeneous human T cell and NK cell lines as effectors. Kinetic analysis demonstrated that as soon as the infected cells began to express HSV glycoproteins on their surface they became susceptible to this enhanced killing. Prolonged culture of HSV-infected cells with heteroconjugate antibodies and effector cells also decreased the amount of viral replication that occurred, as measured in a plaque inhibition assay. These results suggest that heteroconjugate antibodies are potent immunotherapeutic tools that enhance anti-HSV immunity.     

Herpes simplex virus type 1-specific cytotoxic T lymphocytes recognize virus nonstructural proteins.

The specificity of herpes simplex virus type 1-specific cytotoxic T cells was examined with target cells expressing either input viral structural antigens or antigens resulting from permissive infection or cells from an interrupted infection in which they expressed predominantly nonstructural immediate-early proteins. These studies indicated that only an insignificant minority of cytotoxic T cells recognized the input viral antigens, whereas a significant proportion (20 to 35%) recognized target cells that expressed the immediate-early proteins despite the absence of serologically detectable viral antigens upon the infected cell surface. The finding that a significant proportion of cytotoxic T-cell populations obtained from the draining lymph nodes of mice acutely infected with herpes simplex virus type 1 also recognized immediately-early gene-expressing target cells indicates the importance of nonstructural herpes simplex virus proteins to antiviral immunity in vivo.     

Induction of the Epstein-Barr virus latent membrane protein 2 antigen-specific cytotoxic T lymphocytes using human leukocyte antigen tetramer-based artificial antigen-presenting cells

Cytotoxic T lymphocytes (CTLs) specific for the Epstein-Barr virus (EBV) latent membraneprotein 2 (LMP2) antigen are important reagents for the treatment of some EBV-associated malignancies,such as EBV-positive Hodgkin's disease and nasopharyngeal carcinoma.However,the therapeutic amount ofCTLs is often hampered by the limited supply of antigen-presenting cells.To address this issue,an artificialantigen-presenting cell (aAPC) was made by coating a human leukocyte antigen (HLA)-pLMP2 tetramericcomplex,anti-CD28 antibody and CD54 molecule to a cell-sized latex bead,which provided the dual signalsrequired for T cell activation.By co-culture of the HLA-A2-LMP2 bearing aAPC and peripheral bloodmononuclear cells from HLA-A2 positive healthy donors,LMP2 antigen-specific CTLs were induced andexpanded in vitro.The specificity of the aAPC-induced CTLs was demonstrated by both HLA-A2-LMP2tetramer staining and cytotoxicity against HLA-A2-LMP2 bearing T2 cell,the cytotoxicity was inhibited bythe anti-HLA class Ⅰ antibody (W6/32).These results showed that LMP2 antigen-specific CTLs could beinduced and expanded in vitro by the HLA-A2-LMP2-bearing aAPC.Thus,aAPCs coated with an HLA-pLMP2 complex,anti-CD28 and CD54 might be promising tools for the enrichment of LMP2-specificCTLs for adoptive immunotherapy.     

Infection and inhibition of human cytotoxic T lymphocytes by herpes simplex virus.

The effect of herpes simplex virus type 1 (HSV-1) infection on human cytotoxic T-lymphocyte (CTL) lytic function was assessed. All HSV-infected CTL populations tested were significantly inhibited in lysing target cells. The inhibition of CTL lytic function by infection with HSV-1 was independent of T-cell receptor-mediated antigen recognition and did not involve virus-induced shutoff of host protein synthesis, the expression of the HSV-1 transactivation protein, ICP4, or replicating virus. Understanding the functional impairment of CTL following infection with HSV may have important implications for HSV-induced immunosuppression and the mechanism of HSV persistence in immunocompetent hosts.     

Induction of human cytotoxic T lymphocytes by artificial antigen-presenting cells

The adoptive transfer of antigen-specific cytotoxic T lymphocytes (CTLs) is a promising therapeutic approach for a number of diseases. To overcome the difficulty in generating specific CTLs, we established stable artificial antigen-presenting cells (AAPCs) that can be used to stimulate T cells of any patient of a given human leukocyte antigen (HLA) type. Mouse fibroblasts were retrovirally transduced with a single HLA-peptide complex along with the human accessory molecules B7.1, ICAM-1, and LFA-3. These AAPCs consistently elicit strong stimulation and expansion of HLA-restricted CTLs. Owing to the high efficiency of retrovirus-mediated gene transfer, stable AAPCs can be readily engineered for any HLA molecule and any specific peptide.     

Herpes simplex virus type 1-specific cytotoxic T lymphocytes recognize immediate-early protein ICP27.

The identity of herpes simplex virus type 1 (HSV-1) antigens that serve as targets for cytotoxic T lymphocytes (CTL) and their ability to induce protective immunity remain uncertain. In this article, we report the identification of the immediate-early protein ICP27 as a CTL antigen in H-2d mice but not in H-2k or H-2b mice. Calculation of the frequencies of H-2d-restricted virus-specific CTL demonstrated that approximately one-fourth of the total HSV-1-specific response was directed against ICP27. To define the location of this CTL epitope, four truncated derivatives of the ICP27 gene which place the epitope in a 217-amino-acid region (amino acids 189 to 406) near the central portion of the protein were constructed. Mice immunized with ICP27 were able both to induce HSV-1-specific CTL and to survive a lethal intraperitoneal challenge with virulent HSV-1. However, neither appreciable antibody nor delayed-type hypersensitivity responses were induced in immunized mice, and they were also unable to clear a local epithelial virus challenge. It appears that ICP27, although capable of inducing several aspects of the immune response, is by itself unable to provide complete immunity.     

The role of cytotoxic T lymphocytes in human T-cell lymphotropic virus type 1 infection

The vast majority of individuals infected with human T-cell lymphotropic virus type 1 have a strong and persistently activated cytotoxic T lymphocyte response to the virus. Experimental work investigating the effects of human T-cell lymphotropic virus-specific cytotoxic T lymphocytes is conflicting. One significant body of work suggests that specific cytotoxic T lymphocytes are protective and help to reduce the risk of disease. However, another body of work implies that specific cytotoxic T lymphocytes play an important role in the development of disease. Here we use a theoretical model to explore the role of cytotoxic T lymphocytes in persistent infection. A way of reconciling the apparently contradictory data is proposed and experimentally testable predictions are made.     

Natural killer cells as novel helpers in anti-herpes simplex virus immune response

Innate defenses help to eliminate infection, but some of them also play a major role in shaping the magnitude and efficacy of the adaptive immune response. With regard to influencing subsequent adaptive immunity, NK cells aided by dendritic cells may be the most relevant components of the innate reaction to herpes simplex virus (HSV) infection. We confirm that mice lacking or depleted of NK cells are susceptible to HSV-induced lesions. The quantity and quality of CD8(+) cytotoxic T lymphocytes generated in the absence of NK cells were diminished, thereby contributing to susceptibility to HSV-induced encephalitis. We demonstrate a novel helper role for NK cells, in that NK cells compensate for the loss of CD4 helper T cells and NK cell supplementation enhances the function of wild type anti-HSV CD8 T cells. In addition, NK cells were able to partially rescue the dysfunctional CD8(+) T cells generated in the absence of CD4 T helper cells, thereby performing a novel rescue function. Hence, NK cells may well be exploited for enhancing and rescuing the T-cell response in situations where the CD4 helper response is affected.     

Mechanisms of antiviral immunity induced by a vaccinia virus recombinant expressing herpes simplex virus type 1 glycoprotein D: cytotoxic T cells

We used a transfected L cell and a vaccinia vector carrying the herpes simplex virus type 1 (HSV-1) gene coding for glycoprotein D (gD) to characterize HSV-specific T-cell responses. Various studies with mice revealed that the vectors could stimulate some HSV-specific T-cell responses. Although the majority of the T cells contributing to the HSV-1 gD-specific proliferative response were of the Lyt-2.1+ phenotype, cytotoxic T cells (Tc), surprisingly, were not induced by these gD vectors. Even though gD appeared to be a target for a class II major histocompatibility complex (MHC)-restricted killer cell, neither gD vector was capable of forming a target cell complex which could be recognized by class I MHC-restricted HSV-specific Tc. Further investigation of the gD-specific responses revealed the presence of potent suppressor cells and factors capable of inhibiting HSV-specific Tc induction in in vitro assays. One interpretation of these data is that class I MHC-restricted HSV- and gD-specific Tc do not develop during HSV infection because of active suppression.     

Induction of alloreactive cytotoxic T cells by acute virus infection of mice

Alloreactive cytotoxic T lymphocytes (CTL) distinct from virus-specific CTL and activated natural killer (NK) cells were generated during acute lymphocytic choriomeningitis virus (LCMV) infection of C57BL/6J mice. The alloreactive CTL shared similar antigenic markers (Thy-1.2+, Lyt-2.2+, and asialo GM1-) with the virus-specific CTL that appeared at the same time 7 days postinfection, but had different target specificities. These alloreactive CTL lysed allogeneic but not syngeneic or xenogeneic targets. These were distinct from activated NK cells, which lysed all target cell types, peaked 3 days postinfection, and had a phenotype of asialo GM1+, Thy-1 +/-, Lyt-2.2-. Cold target competition studies indicated that there were several subsets of alloreactive T cells with distinct specificities, and that these alloreactive T cells were not subsets of the virus-specific T cells. Similar types of alloreactive CTL were induced at much lower levels in C3H/St mice. This may indicate that the generation of this "aberrant" T cell activity is under genetic control. Hence, the LCMV infection of C57BL/6J mice induces several cytotoxic effector populations including alloreactive CTL, activated NK cells, and virus-specific CTL. Virus infections therefore have the ability not only to polyclonally stimulate B cells, as previously described, but also to stimulate CTL.     

The role of HLA class I antigens in recognition of melanoma cells by tumor-specific cytotoxic T lymphocytes. Evidence for shared tumor antigens

CTL lines were established in vitro by stimulating patient lymphocytes with autologous melanoma cells in the presence of IL-2. Resulting CTL lines lysed autologous melanoma and failed to lyse several allogeneic melanomas or K562. The mechanism of target cell recognition by autologous tumor-specific CTL was evaluated in this system, using several CTL lines: DT6, DT105, DT141, DT166, DT169, and DT179. Autologous melanoma lysis was inhibited by W6/32, mAb directed against HLA class I Ag, but not by L243, mAb directed against HLA class II Ag. CTL from DT6, DT141, DT166, DT169, and DT179 lysed fresh and cultured allogeneic melanomas, which shared the HLA-A2 Ag, but failed to lyse allogeneic melanomas, which shared B-region or C-region Ag, or shared no HLA class I Ag. CTL from DM141 lysed DM93, which shared A2 and Bw6, but failed to lyse DM105, which shared only Bw6. DM105 CTL failed to lyse allogeneic melanomas that shared HLA-A1, or that shared B or C region Ag, but they did lyse allogeneic melanoma DM49, which expressed an A region Ag that either was A10 or was serologically cross-reactive with A10. A T cell leukemia line, three EBV transformed B cell lines, and a pancreatic cancer line, all of which expressed HLA-A2, were not lysed by DM6 or DM179 CTL. Furthermore, HLA-matched nonmelanomas failed to inhibit autologous tumor lysis in cold target inhibition assays, whereas an HLA-A2+ allogeneic melanoma, DM93, inhibited autologous tumor lysis as effectively as the autologous tumor itself. HLA-A2, and possibly other HLA-A-region Ag, appear to function in HLA-restricted recognition of shared melanoma associated Ag by CTL.     

Inhibitory effect of herpes simplex virus infection to target cells on recognition of minor histocompatibility antigens by cytotoxic T lymphocytes

Target cell lysis by CTL specific for minor histocompatibility Ag (minor HA), which were generated in (C3H/He x BALB/c)F1 mice immunized with A/J mouse spleen cells, was dramatically reduced by infection of HSV to Neuro-2a (A/J mouse origin) cells as target. The reduction was apparent at 5 h after infection of HSV to target cells, when many viral proteins were produced in the cells. Conversely, MHC-restricted HSV-specific CTL-mediated cell lysis increased time dependently. Using an RNA virus, vesicular stomatitis virus, significant reduction of minor specific CTL-mediated target cell lysis was also found. During the time when this reduction of target cell lysis by HSV occurred, the surface expression of class I H-2Dd molecules was maintained, and anti-H-2a allo-MHC-specific CTL lysed HSV-infected Neuro-2a cells as strongly as uninfected Neuro-2a cells. When HSV-infected or uninfected Neuro-2a cells were treated with Brefeldin A that selectively blocks transportation of newly synthesized proteins out of endoplasmic reticulum, both HSV- and minor HA-specific CTL-mediated cell lyses were blocked. These observations demonstrated that minor HA are continuously synthesized and associated with class I molecules at pre-Golgi and transported via trans Golgi system with quick turnover, and that newly synthesized HSV Ag, which are also associated with class I molecules and transported via the same system, should take the place of intrinsic minor HA and be presented on the surface of the cells to be recognized by MHC-restricted CTL.     

Mapping of a herpes simplex virus type 2-encoded function that affects the susceptibility of herpes simplex virus-infected target cells to lysis by herpes simplex virus-specific cytotoxic T lymphocytes.

A function(s) involved in the altered susceptibility of herpes simplex virus type 2 (HSV-2)-infected cells to specific lysis by cytotoxic T lymphocytes was mapped in the S component of HSV-2 DNA by using HSV-1 X HSV-2 intertypic recombinants (RH1G44, RS1G25, R50BG10, A7D, and C4D) and HSV-1 MP. Target cells infected with R50BG10, A7D, and C4D exhibited reduced levels of cytolysis, as did HSV-2-infected cells, whereas RH1G44 and RS1G25 recombinant-infected and HSV-1 MP-infected cells showed levels of lysis equal to that of HSV-1 KOS-infected cells. The intertypic recombinants R50BG10, RS1G25, RH1G44, and HSV-1 MP induced cross-reactive cytotoxic T lymphocytes. Coinfection of cells with HSV-1 KOS and either HSV-2 186 or R50BG10 recombinant also resulted in a decrease in the level of specific lysis by anti-HSV cytotoxic T lymphocytes.     

Induction of antigen-specific regulatory T cells following overexpression of a Notch ligand by human B lymphocytes

In mice, activation of the Notch pathway in T cells by antigen-presenting cells overexpressing Notch ligands favors differentiation of regulatory T lymphocytes responsible for antigen-specific tolerance. To determine whether this mechanism operates in human T cells, we used Epstein-Barr virus-positive lymphoblastoid cell lines (EBV-LCL) as our (viral) antigen-presenting cells and overexpressed the Notch ligand Jagged-1 (EBV-LCL J1) by adenoviral transduction. The EBV-LCL J1s were cocultured with autologous T cells, and the proliferative and cytotoxic responses to EBV antigens were measured. Transduction had no effect on EBV-LCL expression of major histocompatibility complex (MHC) antigens or of costimulatory molecules CD80, CD86, and CD40. However, we observed a 35% inhibition of proliferation and a >65% reduction in cytotoxic-T-cell activity, and interleukin 10 production was increased ninefold. These EBV-LCL J1-stimulated T lymphocytes act as antigen-specific regulatory cells, since their addition to fresh autologous T cells cultured with autologous nontransduced EBV-LCL cells significantly inhibited both proliferation and cytotoxic effector function. Within the inhibitory population, CD4(+)CD25(+) and CD8(+)CD25(-) T cells had the greatest activity. This inhibition appears to be antigen-specific, since responses to Candida and cytomegalovirus antigens were unaffected. Hence, transgenic expression of Jagged-1 by antigen-presenting cells can induce antigen-specific regulatory T cells in humans and modify immune responses to viral antigens.