Carbodiimide enhancement of complement-dependent antibody-mediated tumor cell lysis in vitro and antitumor activity in vivo.

The water-soluble carbodiimide salt 1-ethyl-3-(3'-dimethylaminopropyl)carbodiimide. HCl (EDCI-HCl) has been shown to increase the complement-dependent lysis of cultured mouse neuroblastoma C1300 cells by two types of antibody: (1) natural antibodies in the sera of normal (nonimmunized) rabbits, and (b) serum antibodies from snygeneic tumor-bearing A/HeJ mice. In the latter case, both the level of serum antibodies and the extent of carbodiimide enhancement of immune lysis were demonstrated in vitro to be substantially greater with sera from mice bearing 21-day-old tumors relative to 4-day-old tumors. The carbodiimide EDCI-HCl has also been found to increase the complement-dependent lysis of cultured TA3 carcinoma cells by serum antibodies from isogeneic LAF1/J mice bearing ascites tumors in advanced stages of growth. Finally, it has been shown that EDCI-HCl exerts an antitumor activity in vivo that is significantly greater against 21-day-old than against 4-day-old neuroblastoma c1300 tumors. The increase in EDCI-HCl activity with tumor age is contrary to the response that would be expected if this drug were serving as an antimetabolite. This is evidenced by data showing that the antimetabolite 6-thioguanine is most effective against young rapidly growing neuroblastoma C1300 tumors. The correlation between carbodiimide antitumor activity and host production of cytotoxic antibodies suggests that EDCI-HCl may operate in vivo by an immunological mechanism comparalbe to that demonstrated in vitro.

Effect of streptavidin on cardiac allograft prolongation is due to host T-Cell suppression.

AIM: The aim of this study was to evaluate the effectiveness of streptavidin immunomodulation in the high-responder WF-to-Lewis combination. METHODS/RESULTS: We examined the effects of streptavidin on the proliferative response of T cells in coculture studies. Two to 200 microg/mL streptavidin significantly (P < .001) suppressed the proliferation of Lewis T cells to WF by 76%-83% compared with untreated responders. Next, we studied the survival of WF cardiac allografts in Lewis recipients pretreated with streptavidin. A 5-day course of peritransplantation recipient treatment with streptavidin doses of 8, 12, 20, 40, and 60 mg/kg combined with single dose of 0.5 mL antilymphocyte serum (ALS) significantly (P < .001) prolonged cardiac allograft survival from MST of 7 +/- 0.5 and 8 +/- 0.5 days in naive and ALS-treated controls to 15 +/- 1, 20 +/- 3, 16 +/- 3, 17 +/- 3, and 23 +/- 2 days, respectively. In contrast, posttransplantation administration of 80 mg/kg streptavidin resulted in animal death, suggesting toxicity of this dose. Additionally, 10 mg/kg or 20 mg/kg streptavidin administration for 10 consecutive days resulted in significant graft prolongation (MST of 18 +/- 1 and 21 +/- 1 days, respectively; P < .001). CONCLUSION: Although peritransplantation streptavidin treatment is effective in prolonging rat cardiac allografts in the high-responder WF-to-Lewis combination, it does not induce permanent graft survival as observed in the low-responder combination of Lewis-to-ACI. Our finding of in vitro immunomodulatory effect of streptavidin on T-cell proliferation suggests that its in vivo effect is partly due to prevention of T-cell activation following antigen exposure.

Induction of donor-specific unresponsiveness to rat cardiac allograft by donor leukocytes and cyclosporine.

Many recent reports have emphasized the importance of donor antigens in the induction of allograft tolerance. This study examines the effect of pretransplant infusion of 10(8) donor leukocytes (DL) combined with peritransplant cyclosporine (CsA) on W/F cardiac allograft survival in Lewis rats. Peritransplant recipient treatment consisted of CsA 20 mg/kg given i.m. on days 0, +1, and +2 relative to heart transplantation. Lewis recipients, 5-8 per group, were pretreated with 10(8) DL with or without peritransplant CsA. A single DL transfusion on day -3 or day -7 prior to transplantation significantly prolonged the mean survival time (MST) of W/F hearts from 7.0 +/- 0.9 days in controls to 12.2 +/- 4.5 days and 12.4 +/- 1.0 days (P less than 0.01), respectively. Two DL infusions on days -7 and -3 or on days -14 and -7 prolonged the MST to 10.6 +/- 1.3 days (P less than 0.02) and 16.4 +/- 2.8 days (P less than 0.001), respectively. The administration of peritransplant CsA alone significantly prolonged W/F heart allograft survival to 43.1 +/- 2.7 days. When pretransplant DL transfusion on day -3 was combined with CsA treatment, 4/8 animals maintained their grafts indefinitely (greater than 100 days). Similarly, DL infusion on day -7 with peritransplant CsA led to indefinite graft survival in 3/5 animals. Administration of DL on days -7 and -3 combined with CsA resulted in indefinite graft survival (greater than 100 days) in 4/6 animals. Transfusion of DL on day -3 alone or in combination with peritransplant CsA, had no effect on a third-party (ACI) heart allograft survival prolongation compared with appropriate controls. To define the underlying mechanisms responsible for donor-specific unresponsiveness in this model, pooled sera and unseparated spleen cells were passively transferred from recipients of long-term cardiac allografts to syngeneic rats receiving donor-type (W/F) or third-party (ACI) cardiac allografts. Transfer of serum (1 ml on days 0, and 1, 0.5 ml on days +2, +3, and +4) from ungrafted recipients of DL on days -14 and -7 led to significant donor graft survival of 9.8 +/- 0.4 days (P less than 0.02) in unmodified hosts. Similarly, passive transfer of serum obtained at 20 and 100 days after transplantation significantly prolonged the MST of donor-type hearts in syngeneic untreated hosts to 11.3 +/- 0.8 and 10.0 +/- 1.1 days, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Induction of donor-specific unresponsiveness to rat cardiac allografts by intrathymic injection of UV-B-irradiated donor spleen cells.

This study examined the role of intrathymic injection of allogeneic spleen cells in induction of donor-specific unresponsiveness to heart allografts in the Lewis-to-ACI rat combination. Intrathymic injection of naive Lewis SC led to rejection in naive or sublethally irradiated (200 rads TBI) ACI recipients at times equivalent to those obtained in control animals. Intrathymic injection of UV-B-irradiated Lewis SC, on the other hand, led to indefinite cardiac allograft survival (> 300 days) in sublethally irradiated ACI recipients; similar treatment failed to prevent rejection of third-party (Wistar Furth) cardiac allografts, which demonstrates the specificity of the immunologic unresponsiveness thus induced. The finding that intrathymic injection of untreated allogeneic SC does not prevent rejection of subsequently transplanted allograft suggests that modulation of major histocompatibility complex class II molecule by methods such as UVB may be critical to induction of unresponsiveness. Inoculation of UV-B donor SC in extrathymic sites (subcutaneous, intraperitoneal and intratesticular) did not significantly prolong graft survival in similarly prepared animals, thus confirming the privileged position of the thymus in the induction of tolerance. When the unresponsive recipients of cardiac allografts were made diabetic at 100 days and rechallenged with a second-set donor-type neovascularized pancreatic islet grafts, three of four animals accepted permanently (> 100 days) the islet grafts, thus indicating tolerance to donor alloantigens. To define the underlying mechanisms of specific tolerance in this model, in vitro MLR and in vivo adoptive transfer studies failed to demonstrate suppressor activity in the long-term cardiac allograft recipients. In contrast CML assays using 51Cr-release showed that T cells obtained from the unresponsive animals had no detectable cytotoxic activity to Con A-stimulated donor blast targets. The latter finding suggests clonal anergy or deletion of cytotoxic T cells to donor alloantigens. Our results confirm the role of the thymus as a privileged site for the induction and maintenance of specific immunologic unresponsiveness to organ allografts and suggest that this approach may be potentially useful in clinical transplantation of immediately vascularized allografts and neovascularized grafts.

Induction of donor-specific unresponsiveness to rat cardiac allografts by pretreatment with intrathymic donor MHC class I antigens.

Since intrathymic injection of UV-B-irradiated spleen cells induces donor-specific unresponsiveness in the sublethally irradiated (200 rads TBI) recipients, while intrathymic injection of naive SC leads to acute graft rejection, we hypothesized that presentation of MHC class I rather than MHC class II antigens to immature T cells in the thymus may convey a tolerogenic signal to the recipient. The present study was designed to examine if intrathymic injection of naive MHC class I-positive resting T lymphocytes can induce antigen-specific unresponsiveness to cardiac allografts in the Lewis-to-ACI rat combination. The results showed that intrathymic injection of resting Lewis T cells consistently induced indefinite graft survival (> 300 days) in sublethally irradiated (200 rads TBI) ACI recipients while similar treatment failed to prevent the rejection of third-party (Wistar-Furth) cardiac allografts, thus demonstrating the specificity of the immunologic unresponsiveness to donor alloantigens. Examination of the timing of intrathymic antigen presentation relative to cardiac transplantation that would achieve 100% permanent graft survival in the Lewis-to-ACI rat combination showed that the optimal time was 7 days before allografting, while peritransplant and immediate post-transplant intrathymic inoculation of donor T cells was relatively ineffective in the induction of unresponsiveness to donor grafts. We also showed that removal of the antigen-containing thymus in the sublethally irradiated recipients with functioning cardiac allografts consistently caused graft rejection if performed earlier than 21 days after heart transplantation; thymectomy after 21 days of organ transplantation did not affect indefinite survival of the grafts. Thus, it appears that the maintenance of peripheral tolerance to the grafts after 21 days of transplantation may be dependent on the presence of a new clone of antigen-specific tolerant host T cells. These results confirm the immunologic privileged position of the thymus in the induction of central and peripheral tolerance, and suggest that pretreatment with intrathymic MHC class I alloantigens is potentially useful in the induction of unresponsiveness to donor vascularized allografts in adult animals and in man.

Induction of specific unresponsiveness to rat islet allografts by intrathymic UVB donor spleen cells.

Recently, we showed that intrathymic (i.t.) injection of UVB-irradiated (600 J/m2) spleen cells induces donor-specific unresponsiveness to cardiac allografts in the sublethally irradiated (200 rads, TBI) recipients in the Lewis-to-ACI rat combination. This study examined if i.t. injection of UVB donor SC could induce specific unresponsiveness to neovascularized (islet) allografts in the same rat combination of Lewis-to-ACI. Streptozotocin-induced diabetic ACI rats pretreated with sublethal TBI (200 rads) 7 days prior to intraportal transplantation of freshly isolated Lewis islets reject their grafts in 10.2 +/- 2.9 days compared with rejection of islets in 8.5 +/- 2.6 days in unmodified controls. Recipient pretreatment with i.t. injection of UVB donor SC combined with sublethal TBI (200 rads) 7 days prior to islet transplantation induced indefinite graft survival (> 200 days) in 3 of 7 animals. Similar treatment failed to prevent acute rejection of third-party (WF) islets, thus demonstrating donor-specificity. Treatment with sublethal TBI (200 rads) on the day of islet transplantation led to permanent graft survival in 2 of 5 animals that received i.t. inoculation of UVB donor SC 7 days prior to islet transplantation. Conditioning of the recipients with a sublethal TBI dose of 300 rads on the day of islet transplantation, which alone delayed graft rejection for only 19 days, led to indefinite graft survival (> 150 days) in all animals pretreated with i.t. injection of UVB donor SC. Extrathymic inoculation of donor UVB SC via subcutaneous, intraperitoneal, intratesticular, and intravenous routes, respectively in similarly prepared animals failed to prolong islet survival, thus confirming the privileged position of the thymus in the induction of tolerance. Our findings suggest that this new strategy of immunomodulation with donor UVB SC is potentially useful for induction of donor-specific unresponsiveness.

Localization of gallium-67 in the normally functioning Allografted kidney: concise communication.

Radiogallium localization in the normally functioning renal allograft is a normal finding in the immediate postoperative period. The intensity of tracer accumulation decreases with time and is no longer demonstrable by the end of the second postoperative month.

Reduced hepatic accumulation of radiolabeled monoclonal antibodies with indium-111-thioether-poly-L-lysine-DTPA-monoclonal antibody-TP41.2F(ab')2.

In an attempt to improve bifunctional chelate labelling of Mab, we investigated the use of a polyamino acid backbone for multiple DTPA substitutions. Poly-L-lysine (PL) (3.8 Kd, n = 25) was partially acetylated with MADTPA to yield 11 moles of DPTA per mole of PL. The average numbers of DTPA on PL were directly quantified with MADTPA-C-14. The remaining epsilon amino groups on PL-DTPA (I) were measured with TNBS reagent. A selective maleimide derivatization of (I) with S-SMPB yielded (II), which contains 2.3 moles of maleimide groups per mole of (I). The sulfhydryl activation of Mab-TP41.2F(ab')2 with 2-Iminothiolane hydrochloride produced (III), containing 1.3 moles of sulfhydryl groups per mole of Mab. Compounds (II) and (III) were combined to form a single thioether-spaced chain linkage of Mab-PL-DTPA (IV), which was subsequently chelated with 111In to yield (V), which was the compound of interest. Indium-111-PL-DTPA (VI) and 111In-DTPA-MabTP41.2F(ab')2 (VII) also were prepared for control studies. Direct cell binding assay revealed the mean immunoreactivity of (V) to be 79.4% and that of (VII) to be 39.5%. In a biodistribution study on melanoma tumor-bearing athymic mice at 4, 24, and 48 hr postinjection, the tumor/blood and tumor/liver ratios at 48 hr were 11.6 and 1.2 for (V), compared to 3.7 and 0.13, respectively, with (VII). Thus, the PL configuration for radiolabeled antibodies seems to result in decreased hepatic accumulation and retained tumor activity. The findings suggest that further studies of this new compound are warranted.

Bone-seeking properties of Tc-99m carbonyl diphosphonic acid, dihydroxy-methylene diphosphonic acid and monohydroxy-methylene phosphoinic acid: concise communication.

Carbonyl diphosphonic acid, dihydroxy-methylene diphosphonic acid and monohydroxy-methylene diphosphonic acid were synthesized and labeled with Tc-99m. Their chemical structures were confirmed and their bone-seeking relationships were compared with those of Tc-99m MDP in experimental animals. MKonohydroxy-methylene diphosphonic acid was found to have higher bone affinity and faster blood clearance than MDP, whereas carabonyl diphosphonic acid and dihydroxy-methylene diphosphonic acid demonstrated lower bone affinity and slower blood clearance than MDP.

Altered body distribution of [99mTc] pertechnetate in iatrogenic hyperaluminemia.

Failure of intravenously administered [99mTc] pertechnetate to leave the vascular space was observed in a patient with hyperaluminemia due to treatment with an antacid drug containing aluminum hydroxide. A repeat study 3 mo after discontinuing medication, when the plasma aluminum level had fallen, revealed normal in vivo distribution of pertechnetate. It was found that instant thin-layer chromatography, using pertechnetate and an 85% methanol system, can detect plasma aluminum levels as low as 50 microgram/l.

A study of the relationship between chemical structure and bone localization of Tc-99m diphosphonic acids: concise communication.

The study was undertaker to evaluate the effect on bone localization of substitutions at the bridge carbon atom of methylenediphosphonic acid. Two monosubstituted compounds (ethylidenediphosphonic acid and benzylmethylenediphosphonic acid), and one disubstituted compound (isopropylidenediphosphonic acid), were synthesized. The biological behavior was compared with that of MDP and dichloro-MDP in the rat, using Tc-99m as a label. Ethylidenediphosphonic acid showed the highest femur-to-liver and femur-to-muscle ratios. MDP exhibited a slightly faster blood clearance than ethylidenediphosphonic acid.

Potential of palladium-109-labeled antimelanoma monoclonal antibody for tumor therapy.

Palladium-109, a beta-emitting radionuclide, was chelated to the monoclonal antibody 225.28S to the high molecular weight antigen associated with human melanoma. The radiolabeled antibody maintained its specific in vitro reactivity with cultured human melanoma cells. Injection of the radiolabeled monoclonal antibody into nude mice bearing human melanoma resulted in significant accumulation of the radiolabel in the tumors: 19% injected dose/g; 38:1 and 61:1 tumor-to-blood ratios at 24 and 48 hr, respectively. The localization of the radiolabeled antibody in liver and kidney also was high, but appreciably lower than that achieved in tumor. These results suggest that Pd-109-labeled monoclonal antibody to tumor-associated antigens may have potential applications in tumor immunotherapy.

Immunoreactivity and biodistribution of indium-111-labeled monoclonal antibody to a human high molecular weight-melanoma associated antigen.

The anti-human, high molecular weight-melanoma associated antigen (HMW-MAA) MoAb 225.28S was chelated with 111In and then tested for its in vitro reactivity with cultured human melanoma cells and for its biodistribution in human melanoma bearing nude mice. In vitro studies showed that the radiolabeled antibody reacted specifically with cultured melanoma cells. However, binding of DTPA to the monoclonal antibody reduced its titer with cultured melanoma cells from 1:1024 to 1:512. Further labeling of the DTPA-antibody conjugate with 111In caused an additional reduction of its titer to 1:128. Injection of the radiolabeled monoclonal antibody into nude mice resulted in the accumulation of significantly (p less than 0.001) higher radioactivity in melanoma tissue than in nude mice injected with either [111In] chloride or 111In-labeled antibody to human acid phosphatase. The specificity of the distribution of the radiolabeled antibody in nude mice also was indicated by its poor localization in lesions other than melanoma (e.g., human prostate carcinoma and chronic abscess). The localization of antibody in liver and kidney was also high, although lower than that achieved in tumor. These results indicate that 111In-labeled monoclonal antibodies to human tumor associated antigens may be useful for localizing malignant lesions. However, there is a need to improve labeling and/or purification of antibody in order to decrease renal and hepatic activity.

Cerebral SPECT imaging: effect on clinical management.

This study, performed in 94 consecutive patients referred for evaluation, demonstrates the clinical utility of cerebral SPECT imaging. In a significant percentage of patients (47%), the additional information provided by SPECT resulted in an alteration in clinical management. Long-term follow-up will be necessary to determine the effect of these management decisions on patient outcome.

Rapid localization of indium-111-labeled inhibited recombinant tissue plasminogen activator in a rabbit thrombosis model.

The thrombus localizing properties of indium-111-recombinant tissue plasminogen activator (111In-rt-PA) have been investigated in an effort to achieve prompt and accurate detection of thrombi. Unlike previous studies with rt-PA, the active plasminogen catalytic site was permanently inhibited with peptides of chloromethyl ketone so that the radiotracer binds to fibrin without causing fibrinolysis. Thrombi were created in the external jugular vein of 14 male New Zealand white rabbits followed by injection of 111In-rt-PA. The agent cleared rapidly in vivo with a half-time of 4.6 min. The thrombus: blood ratio in nonheparinized rabbits (n = 7) was 6.39 +/- 0.86. The ratio in heparinized rabbits (n = 4) was 3.11 +/- 0.23. Thrombi were clearly visible in the planar images of both groups 1 hr postinjection. The combination of rapid thrombus localization and positive images, especially in the presence of anticoagulation, suggests that further work is warranted with rt-PA thrombus imaging.

Cellular basis for accumulation of In-111-labeled leukocytes and platelets in rejecting cardiac allografts: concise communication.

Biodistribution and imaging studies in rats showed that In-111-labeled leukocytes and platelets accumulate progressively with time after transplantation in cardiac allografts undergoing rejection, but do not accumulate in normal syngeneic heart grafts. Maximum heart allograft-to-blood ratios of 9:1 were obtained, and allograft-to-native heart ratios of 17:1. Microscopic studies of the rejecting cardiac allografts showed that histologic findings paralleled the cellular changes predicted by the radionuclide studies. Intravenously administered Ga-67 citrate and Tc-99m sulfur colloid failed to show significant accumulation in rejecting grafts. The findings suggest that cellular rejection, rather than nonspecific inflammatory changes, is the primary basis for accumulation of In-111 leukocytes and platelets in rejecting cardiac allografts.

Clinical utility of labeled cells for detection of allograft rejection and myocardial infarction.

The choice of a specific radiolabeled blood component for use in detection of allograft rejection depends on several factors including the immunosuppressive agents used, the type of organ allografted, and particularly the length of time the allograft resides in the host and the duration of rejection. To date, only the use of 111In-labeled platelets in renal allograft recipients immunosuppressed with azathioprine and corticosteroids has shown clinical promise in the detection of early allograft rejection. Radiolabeled blood components are unlikely to play a significant role in detection of myocardial infarction. The use of these agents for monitoring therapeutic interventions or as indicators of prognosis in patients with myocardial infarction continues to be investigated.

Mn (III) hematoporphyrin. A potential MR contrast agent.

Manganese (III) hematoporphyrin (MnHP), a new and stable complex, was prepared, and its toxicity and magnetic resonance (MR) imaging properties were evaluated. In tests of acute and subacute toxicity, no deaths resulted from bolus intravenous injections of 13 or 19 mumols/kg of MnHP, but there was a 33% mortality when the dose was 38 mumols/kg. Laboratory results were normal in the surviving rats. Ultraviolet- visible spectroscopy of the urine and serum of two rats injected 24 hours previously with 38 mumols/kg MnHP revealed no free HP, suggesting in vivo stability of MnHP. Finally, using a standardized imaging protocol, there was a mean increase of 37% in the liver-to-muscle intensity ratios in four rats injected 24 hours previously with 25 mumols/kg MnHP when compared to paired controls (P less than .005). In addition, obvious visual increase in the signal intensity of the liver on T1-weighted images was seen in animals tested with 13 and 19 mumols/kg of MnHP. The results suggest that further evaluation of MnHP as an MR contrast agent for the liver is warranted.

Permanent rat cardiac allograft survival induced by ultraviolet B-irradiated donor lymphocytes and peritransplant cyclosporine.

This study examines the effect of pretreatment with 10(8) ultraviolet B-irradiated donor leukocytes (UV-DL) with or without peritransplant cyclosporine (CyA) treatment (20 mg/kg on days 0, +1, and +2 relative to transplantation) on rat cardiac allograft survival across major histocompatibility loci. A single UV-DL pretreatment on day -3 or -7 (before transplantation) significantly prolonged survival of heart allografts from Wistar-Furth rats (W/F) in Lewis recipients from 6.8 +/- 0.8 days to 18.4 +/- 2.1 and 17.6 +/- 1.5 days (p less than 0.001), respectively. Multiple UV-DL infusions on days -14 and -7 increased the mean survival time to 20.0 +/- 0.9 days (p less than 0.001). Similarly, UV-DL infusion on day -3 or -7 significantly prolonged the mean survival time of heart allografts from ACI rats in Lewis rats. A single or multiple UV-DL infusions combined with peritransplant CyA led specifically to permanent W/F cardiac allograft survival (more than 200 days) in all recipients. Similarly, UV-DL infusion combined with peritransplant CyA led to indefinite survival of ACI cardiac allografts in two thirds of Lewis recipients. Adoptive transfer of splenocytes from long-term recipients of cardiac allografts, which specifically prolonged donor test grafts in syngeneic hosts, suggests that unresponsiveness to cardiac allografts is, in part, dependent on suppressor cells. This study emphasizes the importance of UV irradiation of DLs in the modulation of alloreactivity and the induction of donor-specific unresponsiveness in adult animals.

Selective lymphoid irradiation. I. An approach to transplantation.

The kinetics, distribution, and radiobiologic effects of palladium (Pd)-109-hematoporphyrin were determined in the rat. In addition, we studied the effect on rat heart allograft survival of Pd-109-hematoporphyrin, with and without antilymphocyte serum (ALS). A single sublethal dose of Pd-109-hematoporphyrin (up to 36 muCi/kg) resulted in the following: predominant concentration in lymphoid tissue and proximal bone marrow, complete central and proximal bone marrow ablation with preservation of distal bone marrow, massive depletion of lymphocytes from lymph nodes and spleen, an 80% reduction in peripheral blood lymphocytes which was completed by the addition of ALS, full recovery of lymphoid tissue and blood cellularity within 60 days of administration of radionuclide, and a 100% animal survival rate. This method of selective lymphoid irradiation (SLI) prolongs indefinitely Fisher cardiac allografts in Lewis recipients and significantly prolongs cardiac allograft survival across major histocompatibility barries (ACI to Lewis or to Fisher). Specific tolerance to donor strains was demonstrated by the acceptance of Fisher skin by Lewis recipients carrying 150-day-old Fisher hearts. Third party (ACI) skin allografts were rapidly rejected by the same animals. Further studies of SLI in larger animals are required to determine the optimal safe dose of SLI in man.