Permanent, lowered HLA class I expression using lentivirus vectors with shRNA constructs: Averting cytotoxicity by alloreactive T lymphocytes

Transplantation of many tissues requires histocompatibility matching of human leukocyte antigens (HLA) to prevent graft rejection, to reduce the level of immunosuppression needed to maintain graft survival, and to minimize the risk of graft-versus-host disease, particularly in the case of bone marrow transplantation. However, recent advances in fields of gene delivery and genetic regulation technologies have opened the possibility of engineering grafts that display reduced levels of HLA expression. Suppression of HLA expression could help to overcome the limitations imposed by extensive HLA polymorphisms that restrict the availability of suitable donors, necessitate the maintenance of large donor registries, and complicate the logistics of procuring and delivering matched tissues and organs to the recipient. Accordingly, we investigated whether knockdown of HLA by RNA interference (RNAi), a ubiquitous regulatory system that can efficiently and selectively inhibit the expression of specific gene products, would enable allogeneic cells to evade immune recognition. For efficient and stable delivery of short hairpin-type RNAi constructs (shRNA), we employed lentivirus-based gene transfer vectors, which provide a delivery system that can achieve integration into genomic DNA, thereby permanently modifying transduced graft cells. Our results show that lentivirus-mediated delivery of shRNA targeting pan-Class I and allele-specific HLA can achieve efficient and dose-dependent reduction in surface expression of HLA in human cells, associated with enhanced resistance to alloreactive T lymphocyte-mediated cytotoxicity, while avoiding MHC-non-restricted killing. We hypothesize that RNAi-induced silencing of HLA expression has the potential to create histocompatibility-enhanced, and, eventually, perhaps "universally" compatible cellular grafts.

Chemo-immunotherapy and chemo-adoptive immunotherapy of cancer

The chemo-immunotherapy (CIT) and chemo-adoptive immunotherapy (CAIT) regimens tested in the past decade are summarized. From them we have learned a great deal about the interactions between various chemotherapeutic agents, immune modulating agents and effector cells. The most commonly reported result in multi-modality experiments with CAIT has been a synergistic enhancement in antitumor activity. Clinical trials usually demonstrated improvement in patient quality of life, an extension of survival time, and occasional complete regression of tumor. In many animal models, this enhancement often meant the complete regression and apparent cure of tumor in the animal. One mechanism by which this synergistic enhancement takes place appears to be a suppression of tumor-associated suppressor T cell activity by the chemotherapeutic agents, thereby inducing enhanced cytolytic activity against tumor by the adoptively transferred, activated effector cells. In CAIT the most commonly used drug has been cyclophosphamide. In CIT a wide variety of chemotherapy agents have been used but none of the clinical trials made use of cyclophosphamide. Thus, direct comparisons are not possible. Suggestive of the intricate regulatory processes involved, many CIT studies indicate a synergy only when specific doses of chemotherapy and immunotherapy agents are given, and in a specific sequence. CIT has become less toxic, is being handled on a cost-effective outpatient basis, while maintaining similar objective response rates to earlier inpatient treatments. In the future, CAIT and CIT will probably have an increasing role in the management of patients with specific cancers.

The human leukemic T-cell line, TALL-104, is cytotoxic to human malignant brain tumors and traffics through brain tissue: implications for local adoptive immunotherapy

Preclinical studies with the human MHC nonrestricted cytotoxic T-cell leukemic line, TALL-104, were performed in anticipation of its use in cellular immunotherapy trials for primary malignant brain tumors. In this study, we have: (a) quantitated the in vitro brain tumor cell lysis; (b) measured the cytokine secretion upon coincubation of TALL-104 cells with brain tumor cells; (c) investigated the effect of dexamethasone on brain tumor cell cytolysis by TALL-104 cells; (d) explored the effects of lethal irradiation and cryopreservation on TALL-104 cell viability and lytic efficacy; and (e) estimated the damage TALL-104 cells induce to murine normal and tumor brain cells and their trafficking patterns in both normal and tumor-bearing rat brain upon intracranial infusion. In vitro coincubation of TALL-104 cells with human brain tumor cells, explants, and cell lines resulted in significant lysis of them, but normal brain cells were spared. Lysis of tumor at 4 h was unaffected by dexamethasone or lethal irradiation. Secretion of tumor necrosis factor-alpha, tumor necrosis factor-beta, IFN-gamma, or granulocyte/macrophage-colony stimulating factor upon TALL-104 cell coincubation with brain tumor cells variably occurred without always correlating with lysis. In vivo experiments using irradiated TALL-104 cells, placed at multiple times into normal cannulated rat brain, produced focal sterile abscesses at the instillation site but no widespread allergic encephalitic reaction. Cells morphologically consistent with TALL-104 cells specifically trafficked from the site of instillation through the neuropil, occasionally into the contralateral brain, and egressed at perivascular and leptomeningeal spaces. In vivo experiments with cannulated rats bearing 9L gliosarcoma showed a preferential localization of the TALL-104 cells in tumor compared with normal brain. Taken together, these data support the concept that TALL-104 cells can be used as a novel nontoxic and efficacious paradigm for cellular immunotherapy trials in human primary malignant brain tumors.

Effect of immunoglobulin source on survival, growth, and hematological and immunological variables in pigs

The effects of feeding different sources of immunoglobulins (sow's colostrum by nursing, SC; no colostrum, NC; bovine colostrum, BC; and porcine immunoglobulins, PI) to neonatal pigs during the first 2 d of life on their subsequent survival, growth, feed intake, feed conversion, incidence of diarrhea, and selected hematological and immunological variables were assessed throughout a 19-d experimental period. After d 2, all pigs were fed the same liquid basal diet. Crossbred neonatal pigs, 10 per treatment, were individually reared after birth (NC, BC, and PI) or 2 d of age (SC) with an automatic feeding device. All pigs of treatments SC and PI, and 80 and 30% (P < .01) of pigs of treatments BC and NC, respectively, survived to the end of the trial. Growth, feed intake, and feed conversion efficiency (gain/feed) of surviving pigs were similar (P > .05), regardless of treatment. A transient physiological scours was observed in 20 to 50% of the pigs between 5 and 7 d of age; by 10 d of age, all pigs had solid feces. Hemoglobin concentration and hematocrit in blood of pigs of treatment NC were lower (P < .05) than those of the other treatments. Concentrations of total serum proteins, trichloroacetic acid-precipitable proteins, and serum IgG of SC pigs were higher (P < .01) than those of pigs in the other treatments. These results showed that porcine immunoglobulins or bovine colostrum can be satisfactorily used as immunoglobulin sources in artificial rearing of colostrum-deprived neonatal pigs.

Can a super oral rehydration solution stimulate intestinal repair in acute viral enteritis?

This study was designed to screen several treatments for their effects on mucosal repair in an established model of piglet rotavirus enteritis. Six ingredients selected to facilitate repair were added to the oral rehydration solution (ORS) and subsequently to the diet: L-glutamine (GLN); rice solids; a soluble fiber (carboxymethylcellulose); nucleotides; polyamines; and fructooligo-saccharides. Rotavirus infection consistently induced a watery diarrhoea lasting 5 to 10 days and produced a jejunal mucosal lesion which was maximal at 3 days, post-inoculation (manifested by a reduction of villus surface area to 30% to 50% of normal). By 7 to 10 day post-inoculation, the villus surface area returned to 50% to 80% of normal. None of the supplemental ingredients added to the ORS had a significant effect in either shortening the clinical illness or in stimulating recovery of the affected mucosa. It is concluded that several types of "Super ORS" are ineffective in enhancing repair in viral enteritis in neonatal colostrum-deprived piglets. These results do not rule out beneficial effects of the additives tested in subjects with more extensive intestinal damage, in those who receive breast milk, or in those with bacterial enteritis.

High levels of inorganic sulfate cause diarrhea in neonatal piglets

Artificially reared neonatal piglets were used to study the effect of inorganic sulfate on bowel function in human infants. Two experiments were conducted to evaluate the effect of high levels of inorganic sulfate on the growth, feed intake and feces consistency of artificially reared piglets, and to determine the dose at which at least 50% of piglets develop nonpathogenic diarrhea. The effect of sulfate level on kidney weight and concentration of inorganic sulfate in urine was also assessed. In each experiment, 40 pigs with an average initial age of 5 d were individually caged and reared with an automatic feeding device. Ten pigs per dietary treatment were fed one of four diets containing the following levels of added inorganic sulfate (mg/L of diet), as anhydrous sodium sulfate (USP): 0, 1200, 1600 and 2000 for Experiment 1 (18-d study), and 0, 1800, 2000 and 2200 for Experiment 2 (16-d study). The levels of added sulfate did not affect (P > 0.05) the growth of piglets, or their feed intake. Whereas 1200 mg added sulfate/L had essentially no effect on feces consistency, levels > 1800 mg/L of diet resulted in a persistent, nonpathogenic diarrhea in neonatal piglets. Added sulfate did not affect (P > 0.05) relative kidney weight. Inorganic sulfate in urine reached maximum concentration (P < 0.05) in pigs fed diets with 1600 and 1800 mg added sulfate/L in Experiments 1 and 2, respectively, but declined at higher levels. The results suggest that the level of added dietary inorganic sulfate at which 50% of piglets develop nonpathogenic diarrhea is between 1600 and 1800 mg/L.

Asparagine stimulates piglet intestinal Cl- secretion by a mechanism requiring a submucosal glutamate receptor and nitric oxide

Amino acids are potential components of oral rehydration solutions for infants, which could combine with glucose to further stimulate intestinal Na+ and water absorption. L-Glutamine, the principal fuel of the intestine, stimulates neutral NaCl absorption and enhances enterocyte DNA synthesis, but is unstable in solution. L-Asparagine (ASN), a more stable amino acid with similar structure to L-glutamine, also stimulates enterocyte proliferation. We determined the effects of ASN on electrolyte transport across piglet jejunum in Ussing chambers. Mucosal but not serosal ASN produced electrogenic Cl- secretion (delta JClnet = -1.8 +/- 0.3 microEq/cm2.hr-1). ASN, when added at 0.1 to 30 mM, increased short-circuit current in a dose-dependent manner with a K1/2 of approximately 5 mM and maximal effect at approximately 10 mM. The stimulation of Cl- secretion by ASN was blocked by pretreatment with serosal tetrodotoxin and bumetanide and was inhibited by preincubation with capsaicin (8-methyl-N-vanillyl-6-nonenamide) or substance P. Inhibition of nitric oxide synthesis with the structural analog of L-arginine, NG-monomethyl-L-arginine, reduced ASN-stimulated secretion by > 70%. Additionally, serosal 6-cyanonitro-quinoxaline 2-3-dione, which is a nonspecific blocker of neural non-N-methyl D-aspartate (NMDA) glutamate receptors, fully inhibited the ASN response (IC50 = 10(-6) M). Inhibition was specific for neurally mediated secretion. We found no inhibition of ASN-stimulated secretion by atropine, ketanserin, indomethacin or L-2-amino-5-phosphonovalerate (specific for NMDA receptors). When compared to ASN, L-glutamate was a weaker stimulator of jejunal Cl- secretion.(ABSTRACT TRUNCATED AT 250 WORDS)