ANTAGONISTIC EFFECTS OF HUMORAL ISOANTIBODIES ON THE IN VITRO CYTOTOXICITY OF IMMUNE LYMPHOID CELLS

Road testing new CAR design strategies in multiple myeloma

A deeper understanding of basic immunology principles and advances in bioengineering have accelerated the mass production of genetically-reprogrammed T-cells as living drugs to treat human diseases. Autologous and allogeneic cytotoxic T-cells have been weaponized to brandish MHC-independent chimeric antigen receptors (CAR) that specifically engage antigenic regions on tumor cells. Two distinct CAR-based therapeutics designed to target BCMA are now FDA-approved based upon robust, sustained responses in heavily-pretreated multiple myeloma (MM) patients enrolled on the KarMMa and CARTITUDE-1 studies. While promising, CAR T-cells present unique challenges such as antigen escape and T-cell exhaustion. Here, we review novel strategies to design CARs that overcome current limitations. Co-stimulatory signaling regions were added to second-generation CARs to promote IL-2 synthesis, activate T-cells and preclude apoptosis. Third-generation CARs are composed of multiple co-stimulatory signaling units, e.g., CD28, OX40, 4-1BB, to reduce exhaustion. Typically, CAR T-cells incorporate a potent constitutive promoter that maximizes long-term CAR expression but extended CAR activation may also promote T-cell exhaustion. Hypoxia-inducible elements can be incorporated to conditionally drive CAR expression and selectively target MM cells within bone marrow. CAR T-cell survival and activity is further realized by blocking intrinsic regulators of T-cell inactivation. T-Cells Redirected for Universal Cytokine Killing (TRUCKs) bind a specific tumor antigen and produce cytokines to recruit endogenous immune cells. Suicide genes have been engineered into CAR T-cells given the potential for long-term on-target, off-tumor effects. Universal allo-CAR T-cells represent an off-the-shelf source, while logic-gated CAR T-cells are designed to recognize tumor-specific features coupled with Boolean-generated binary gates that then dictate cell-fate decisions. Future generations of CARs should further revitalize immune responses, enhance tumor specificity and reimagine strategies to treat myeloma and other cancers.

Immune response to polyvalent melanoma cell vaccine in AJCC stage III melanoma: an immunologic survival model

BACKGROUND

Our polyvalent, allogeneic melanoma cell vaccine (MCV) induces immunoglobulin M (IgM) and immunoglobulin G (IgG) class antibodies to a 90-kDa glycoprotein melanoma-associated antigen (MAA). Additionally, MCV induces delayed-type hypersensitivity (DTH) responses that we previously correlated with survival. We hypothesized that early DTH responses to MCV and early humoral responses to the 90-kDa MAA expressed on MCV cells may be predictive of overall survival. We tested this hypothesis by monitoring immunologic profiles in 59 patients with melanoma who were receiving MCV after surgical resection of regional lymph node or soft-tissue metastases.

METHODS

Blood was drawn before vaccine administration, biweekly for 6 weeks, and then monthly. DTH to MCV was recorded at 0, 2, 4, and 8 weeks of MCV therapy. Mean antibody titers during the first 6-week interval were calculated. Changes in DTH were calculated as the difference between peak and prevaccine values (delta DTH).

RESULTS

At a median follow-up of 75.6 months (range 5-138), univariate analysis assigned prognostic significance to gender (p = 0.046), lymph node involvement (p = 0.024), delta DTH (p = 0.044), mean anti-90-kDa MAA IgG (p = 0.0009), and mean anti-90-kDa MAA IgM (p = 0.0014). In multifactorial analysis, only the three immunologic variables significantly impacted survival (p = 0.046, 0.0005, and 0.0053, respectively). A mathematical model based on delta DTH and mean anti-90-kDa MAA IgG and IgM titers closely approximated the observed individual and overall survival rates.

CONCLUSIONS

The correlation between overall survival and initial humoral/cellular immune responses to MCV immunotherapy may be useful in selecting patients most likely to benefit from prolonged adjuvant immunotherapy.

Restriction fine specificity of long-term, hapten-specific cytotoxic T cell clones: analysis with H-2Kbm-mutant mice and H-2Kb-specific monoclonal antibodies

The cell-mediated cytotoxic response against autologous cells modified with the sulfhydryl reagent I-AED [N-iodo-acetyl-N-(5-sulfonic-1-naphthyl) ethylene diamine] has been described by Levy, R. B., Shearer, G. M., Richardson, J. C. and Henkart, P. A., [J. Immunol. 1981. 127: 523.]. We have established two H-2Db- and eight H-2Kb-restricted, AED-specific long-term cytotoxic T lymphocyte (CTL) clones of C57BL/10 origin. The growth of these clones has been dependent upon presence of both antigen and interleukin 2. Cytotoxicity and proliferation analysis of AED-specific Kb-restricted CTL clones with target and stimulator cells from Kbm-mutant mice demonstrated two categories of clones (A and B) based on different reactivity patterns against hapten-modified Kbm-mutant cells. AED-modified target cells of bm5, bm6 and bm9 origin were lysed by type A clones but not by type B clones, in contrast to AED-modified bm3, bm8 and bm11 target cells which were lysed by type B but not by type A clones. None of the clones lysed AED-modified bm1 target cells, but all of them lysed AED-modified bm4 and bm10 target cells. The restriction fine specificities for both cytolytic and proliferative activities of the analyzed clones were identical. A panel of monoclonal antibodies (mAb) directed against the Kb molecule was used to inhibit lysis of AED-modified target cells by CTL clones. mAb which recognize a cluster of allodeterminants located in the second external domain (C1 domain) of the Kb molecule [Hämmerling, G. J., Rüsch, E., Tada, N., Kimura, S. and Hämmerling, U., Proc. Natl. Acad. Sci. USA 1982. 79: 4737] only inhibited type B clones, whereas inhibition of both type of clones was observed with mAb specific for allodeterminants clustered in the N-terminal region of Kb. These findings suggest that different regions on the Kb molecule serve as self determinants for H-2-restricted cytotoxicity. We also demonstrate that allodeterminants recognized by mAb and self determinants involved in H-2 restriction need not be identical. Our data also support the notion that covalent AED modification of H-2 molecules is not necessary to generate the self plus X antigen for CTL recognition.

Comparison between the specificity of primary and secondary killer cells against alloantigens and hapten-modified syngeneic lymphoid cells

Cytotoxic responses of lymphoid cells from different mouse strains against syngeneic cells modified with the haptens fluorescein isothiocyanate and trinitrophenyl were investigated. Mic of the H-2k strain demonstrated strong primary in vitro hapten-specific cytotoxicity reactions, which were H-2 restricted and involved the Kk specificity. However, cells from H-2d and H-2b mice developed hapten-specific cytotoxic reactions that showed H-2 cross-reactivity. This cross-reactivity, with regard to the restriction element, was particularly evident with cells from mice that had been immunized in vivo. No cross-reaction was observed between the two haptens, and Dd target cell antigens. Similar cross-reactions were demonstrated in vitro experiments in which secondary in vitro responses were induced by stimulation with cross-reacting H-2 antigens. This finding was also investigated in allogeneic cytotoxicity. In vitro induced responses resulting in relatively weak specific cell-mediated lympholysis reactions were H-2 specific, whereas secondary in vitro responses demonstrated cross-reactivity between Dd and Db antigens. In these test systems, cross-stimulation was also demonstrated in secondary in vitro responses. These results are discussed in terms of similarities of T cell recognition of hapten-modified self antigens and of alloantigens.

Autoregulation of immune responses via idiotype network interactions

Images

Naturally occurring lymphocyte-mediated immunity to endogenous type-C virus in the mouse. Blocking of the lymphocyte reactivity with antisera to the virus

The natural immune response in mice to their endogenous type-C viruses involves a complex interaction between cellular and humoral immune mechanisms. The virus-specific immune reactivities are a function of age and appear only subsequent to endogenous virus expression. Cellular immune activity was found to reside in a population of lymphocytes that were characterized as natural killer cells based on their absence of theta surface antigens or immunoglobulin or complement receptors. Cellular and humoral virus-specific immune responses co-occur in the same animal and pretreatment of virus-positive target cells with sera from virus-positive aging mice is capable of partially blocking the cytotoxic activity of reactive lymphocytes. The blocking activity of sera from individual mice increases as a function of age and endogenous virus expression and is highly correlated with the virus-specific complement-dependent cytotoxic activity of these sera. Mouse sera, whether naturally immune or immune as a result of hyperimmunization with type-C virus, exhibit blocking activity that can be removed by absorption with purified type-C virus or purified viral glycoprotein (gp 70) but not by absorption with noninfected syngeneic cells. High-titered and highly specific antisera directed against certain individual R-MuLV structural proteins reveal blocking activity. Monospecific antisera to gp 70 and p 12 exhibited high-titered blocking reactivities which are absorbable by the respective purified proteins. Blocking activity of antisera directed against other viral structural proteins could not be excluded with certainty. These findings raise the possibility that immunity in the mouse to endogenous type-C virus or virus-infected cells involves competition between serum-blocking activity and natural-killer cell activity and further provides a unique model system for studying the mechanism of action of blocking antisera known to have monospecific reactivity against defined and purifiable transplantation antigens.

[Limits and possibilities of neoplasm immunotherapy]

Immunological treatment of malignant human tumors has so far met with little success. Based on methods and insights obtained by investigation of corresponding animal models, this article attempts to elucidate the reasons for this failure and to suggest ways and means to improve immunotherapeutic approaches to human neoplasms.

Evidence of 'K'-cell killing by alloactivated, Fc-receptor-bearing cytotoxic T lymphocytes

Upon in vivo alloactivation of Ig-anti-Ig column-purified splenic 'T' cells in lethally irradiated allogeneic recipients, a variable proportion of donor-derived cytotoxic T lymphocytes (CTLs) are able to bind IgG antibody-coated erythrocytes through surface Fc receptors (FcR) and form rosettes. The use of fractionation procedures based on the ability of these cells to form rosettes has enabled us to separate FcR-positive CTLs from FcR-negative CTLs and to examine the ability of these two cell populations to perform as effector cells in direct T-cell-mediated killing and in antibody-dependent cellular cytotoxicity. A series of experiments, either by direct isolation of the two cell populations or by deletion of the FcR-positive population by filtration through complexed immunoglobulin columns (Ig-anti-Ig), has shown both populations to be efficient in direct T-cell mediated cytotoxicity against the relevant target cell. The striking difference between the two populations is the exclusive ability of the FcR-positive population to function as effector cells in antibody-dependent cellular cytotoxicity (ADCC). Purification steps before in vivo alloactivation of our responding cells for the removal of 'B' cells and FcR-bearing cells with 'K'-cell activity, followed by procedures to remove phagocytic and adherent cells in the resulting immune spleen cell preparation and, finally, b y velocity sedimentation of the rosetting and nonrosetting blasts from the small lymphocyte population, has resulted in a population of FcR-positive cells 98% positive for the Thy 1.2 alloantigen. These fractionation steps and immunofluorescence criteria of purity strongly favor the contention that the ADCC activity within the FcR-positive T-cell population is indeed a property of the CTL itself.

Abnormal lymphocyte populations in pure red cell aplasia

Studies of blood lymphocytes from 4 patients with pure red cell aplasia were performed with lymphocyte surface markers, and with various in vitro tests for lymphocyte functions. Pathologically low B-lymphocyte values were found. In contrast, no marked deviation from normals were seen for T-lymphocytes and Fc-receptor-bearing lymphocytes thought largely to represent non-B, non-T-lymphocytes. In 3 patients normal lymphocyte transformation was found with unspecific and specific mitogens, while the DNA-synthesis induced by unspecific mitogens was subnormal in the fourth patients. The lymphocyte-mediated PHA-induced cytotoxicity against target cells in vitro was subnormal in 2 patients, while no depression was seen in antibody-dependent cytotoxicity mediated in vitro by lymphocytes (K-cells). It is concluded that considerable immunological abnormalities are associated with pure red cell aplasia, and the possible significance of this is discussed.

Human tumor--lymphocyte interaction in vitro: blastogenesis correlated to detectable immunoglobulin in the biopsy

Binding of radioiodinated anti-immunoglobulin (Ig) reagent assayed by acid elutable radioactivity was shown in 18 of 44 cell suspensions (41%) prepared from surgical specimens of human tumors. Aliquots of these biopsies were admixed to autologous lymphocytes and in 13 cases they induced stimulation of DNA synthesis. In only one of these 13 cases was the anti-Ig reagent bound, while among the 26 biopsies with low or no binding capacity 12 (46%) were stimulatory, indicating that immunoglobulin-containing biopsies are not stimulatory. Experiments on 32 lymphocyte preparations from different lymphoid organs suggest that the immunoglobulin detected in the tumor-cell suspension is not derived from the infiltrating lymphoid cells.

Modulation of the immune response to transplantation antigens. V. A comparison of the effects of antilymphocytic serum and enhancing alloantiserum on effector mechanisms of allograft rejection

Administration of antilymphocytic serum (ALS) or alloantiserum at the time of graft both stimulate enhanced growth of a tumour allograft, but the effect of alloantiserum is weaker and more dependent on dose. Both antisera suppress (or delay) the development of lymphocyte-mediated cytotoxicity, and partly inhibit the development of activated, cytostatic macrophages. Apart from these central or afferent effects, ALS added to an in vitro culture of immune effector cells and EL4 target cells strongly inhibits cytotoxicity, while in this model, alloantiserum is less effective in this respect. The relevance of the effects observed in vitro to in vivo facilitation of allografts is discussed.

Inhibition of specific cell-mediated cytotoxicity by anti-T-cell receptor antibody

The present study describes a method for the production of a specific anti-T-cell receptor antiserum, and characteristics of its ability to block specific cell-mediated cytotoxicity in vitro. Immunization and antiserum adsorption procedures were designed to select for idiotypic differences in the recognition units of C3H lymphocytes immune to two different strains of mouse cells, such that the reactivity of only one population of effector cells is inhibited by this antiserum. Both in vivo and in vitro sensitized effector T cells are subject to this inhibition. That the site of the antiserum blockade is clearly on the effector cell and not on the target cell is demonstrated.

Tumor development after 3-methylcholanthrene in immunologically deficient athymic-nude mice

Athymic-nude (nu/nu) mice and normal (nu/+) mice showed no differences in either latent period or incidence of local sarcomas or lung adenomas within 120 days after administration of 3-methylcholanthrene at birth. However, nu/nu mice were incapable of rejecting allogeneic skin grafts for the duration of the experiment. These results argue against an active role of thymus-dependent immunity as a surveillance mechanism preventing tumor development.

The role of hyperimmune alloantiserum in allograft survival

Nine Brown Norway (BN) rats, immunosuppressed with rabbit anti-rat thymocyte serum were allografted with Le body wall skin. Eleven days after successful allografting, 4 ml of BN anti-Le alloantiserum were given intraperitoneally. Eight allografts were rejected in an accelerated manner.