Autoantigens produced in plants for oral tolerance therapy of autoimmune diseases

Oral administration of protein antigens can induce antigen-specific immune hyporesponsiveness and may be useful in treating autoimmune diseases or preventing transplant rejection. However, the therapeutic value of oral tolerance may be limited when candidate autoantigens cannot be produced by conventional system in quantities sufficient for clinical studies. Plants may be ideally suited for this purpose, as they can produce hugh quantities of functional mammalian proteins at extremely competitive cost. Furthermore, transgenic food plants could provide a simple and direct method of autoantigen delivery for oral tolerance. Here we show that the diabetes-associated autoantigen glutamic acid decarboxylase (GAD) is efficiently expressed in both tobacco and potato plants, and that mice, when fed with fresh transgenic potato tubers, are fully protected from diabetes.

[Study on mutation of exon 8 of Wilson's disease gene]

OBJECTIVE

To analyze the frequency of mutation in exon 8 of Wilson's disease (WD) gene in Chinese people.

METHODS

Screening for ATP7B gene mutation was conducted in 45 WD patients. Mobility shift of exon 8 was analyzed by SSCP. Nucleotide sequence of exon 8 was analyzed, and the PCR products were cut by enzyme Msp I. The authors found G2273T mutation at codon 778, and according to this mutation sequence, made an analysis of enzyme cut by Msp I in all patients. 2 WD families were analyzed.

RESULTS

No abnormality was found in 20 controls. In 45 patients, 2 were homozygous (4.4%) and 11 heterozygous (12.2 ). The positive rate of mutation was 16.67%. The Arg778Leu mutation was validated by this study.

CONCLUSION

The mutation in exon 8 of WD gene may play an important role in pathogenesis of Wilson's disease in Chinese.

Phalloplasty in female-to-male transsexuals using free radial osteocutaneous flap: a series of 22 cases

From July 1994 to December 1996, 22 cases of primary female transsexualism received phalloplasty using free radial forearm osteocutaneous flaps in The Veterans General Hospital, Taipei, Taiwan. Follow-up period ranged from 6 months to 35 months. No complete flap loss and one partial loss (10% reduction) were noted after operation. The urethrocutaneous fistula rate was 40.9%, needing fistula repair surgery. Urethral stricture was noted in three cases (13.7%). Significant donor forearm morbidity was noted in two cases (9.1%) including one who suffered from radius bone fracture. All preserved 'clitorises' had intact erotic sensation and all neophalli gained protective sensation within 9 months. No 'penile fracture' was noted. In nine cases that have regular sexual activities, the sexual performance was rated as satisfactory. We share our experience and recommend that the free radial forearm osteocutaneous tubing flap is a promising choice for phalloplasty in female-to-male transsexuals.

[Post-operative respiratory failure in lung cancer patients.]

BACKGROUND

To explore the reasons , prevention and treatment measures of post-operative respiratory failure in lung cancer patients.

METHODS

Mechanical ventilation was given to 26 lung cancer patients with post-operative respiratory failure in our hospital fromJanuary 1990 to October 1997 , and 19 out of them received tracheotomy.

RESULTS

The incidence of post-operative respiratory failure was 4. 7 %(26/558) . Twenty cases were cured and 6 died (23. 1 %) .

CONCLUSIONS

Respiratory tract infection , operative wound , incision pain , abnormal pre-operative cardio-pulmonary function , etc , are the major reasons which caused post-operative respiratory failure. Correct diagnosis , tracheotomy as early as possible and mechanical ventilation are the most efficient ways to save lifes. Strengthening management on respiratory tract in peri-operative period and avoiding post-operative complications are the keys of preventing post-operative respiratory failure.

Inhibitory effects of nitric oxide and interleukin-10 on production of tumor necrosis factor alpha, interleukin-1 beta, and interleukin-6 in mouse alveolar macrophages

AIM

To observe the effects of nitric oxide and interleukin-10 (IL-10) on inflammatory reaction in mouse alveolar macrophages (AM).

METHODS

AM from mice were stimulated by lipopolysaccharides (LPS) 10 mg.L-1 and nitric-oxide synthase inhibitor, S-methylisothiorea sulfate (SMT) or nitric-oxide donor, S-nitroso-N-acetyl-D, L-penicillamine (SNAP). The production of tumor necrosis factor alpha (TNF alpha), IL-1 beta, IL-6, and IL-10 by AM were measured by ELISA.

RESULTS

After LPS-stimulation, TNF alpha, IL-1 beta, and IL-6 peaked at 6, 12, and 24 h, respectively by AM. SMT inhibited LPS-induced nitric oxide release and increased IL-1 beta and IL-6 secretions in AM, but the TNF alpha levels remained unchanged. SNAP had inhibitory effects on IL-1 beta and IL-6 secretions in a concentration-dependent manner, but exerted no effect on TNF alpha release. TNF alpha, IL-1 beta, and IL-6 secretions were inhibited by recombinant IL-10, but the cytokines release was upregulated by anti-IL-10 monoclonal antibody.

CONCLUSION

Both endogenous and exogenous nitric oxide and IL-10 had inhibitory effects on the LPS-induced TNF alpha, IL-1 beta, and IL-6 secretions in mouse AM.

Secretion of 92 kDa gelatinase (MMP-9) by bovine neutrophils

To understand the process of neutrophil migration into mammary glands during mastitis, secretion of MMP-9 by bovine neutrophils was investigated. The methods of zymograms and RT-PCR were used to measure the secretory MMP-9 activity and its gene transcription, respectively. Both MMP-9 protein and mRNA were found to be expressed constitutively and greatly enhanced by PMA. However, the significant increase in the enzyme activity was found after 1 ng/ml PMA treatment for 1 h, while increasing MMP-9 mRNA transcription was only obvious after 1 ng/ml PMA treatment for 3 h. Moreover, secretion of MMP-9 protein was not inhibited by actinomycin D and cycloheximide. These results suggest that quick MMP-9 protein release from bovine neutrophils by the stimulation of PMA was due to the degranulation. As MMP-9 is an important proteinase in breakdown of the extracellular matrix and can be rapidly secreted by neutrophils through degranulation, it should play a critical role in the recruitment of neutrophils into mammary glands in bovine mastitis.

Differential regulation of in vitro cytokine production by human blood cells in response to methylmethacrylate

The effect of methylmethacrylate (MMA) on human whole blood cultures (WBC) obtained from healthy donors was investigated. Lymphocyte transformation and cytokine production, that is, interleukin 6 (IL-6), interferon-gamma (IFN-gamma), and tumor necrosis factor-alpha (TNF-alpha), were used to evaluate the immunological activities of MMA. Primary cytotoxicity testing of MMA in Jurkat cells showed that this compound decreased the cell proliferation to 50% at a concentration of >60 mmol/L. Similarly, MMA significantly decreased lymphocyte transformation in either phytohemagglutinin (PHA) or Staphylococcus aureus protein A (SpA) activated WBC at 100 mmol/L. In contrast to activated WBC, MMA had no observed effect on resting blood cells. Cytokine expression in WBC seemed differentially modulated by MMA. There was a tendency for IL-6 production in both resting and PHA-stimulated WBC to be upregulated, while IL-6 induced in SpA stimulated cultures was downregulated. TNF-alpha was slightly increased by MMA in resting WBC at early incubation periods, and it was slightly downregulated in response to PHA or SpA activation. Suppression of IFN-gamma secretion was observed in WBC with or without PHA or SpA stimulation. The overall results demonstrated that MMA at physiological levels could influence the cytokine production in normal human blood cells in vitro. Alterations of cytokine production patterns by MMA indicate that this compound has multiple regulatory effects on immune reactions in normal human blood.

The family of cold shock proteins of Bacillus subtilis. Stability and dynamics in vitro and in vivo

Bacillus subtilis possesses three homologous small cold shock proteins (CSPs; CspB, CspC, CspD, sequence identity >72%). They share a similar beta-sheet structure, as shown by circular dichroism, and have a very low conformational stability, with CspC being the least stable. Similar to CspB, CspC and CspD unfold and refold extremely fast in a N <==> U two-state reaction with average lifetimes of only 100-150 ms for the native state and 1-6 ms for the unfolded states at 25 degreesC. As a consequence of their low stability and low kinetic protection against unfolding, all three cold shock proteins are rapidly degraded by proteases in vitro. Analysis of the CSP stabilities in vivo by pulse-chase experiments revealed that CspB and CspD are stable during logarithmic growth at 37 degreesC as well as after cold shock. The cellular half-life of CspC is shortened at 37 degreesC, but under cold shock conditions CspC becomes stable. The proteolytic susceptibility of the CSPs in vitro was strongly reduced in the presence of a nucleic acid ligand, suggesting that the observed stabilization of CSPs in vivo is mediated by binding to their substrate mRNA at 37 degreesC and, in particular, under cold shock conditions.

Lymphotactin gene-modified bone marrow dendritic cells act as more potent adjuvants for peptide delivery to induce specific antitumor immunity

Dendritic cells (DC) are regarded as attractive candidates for cancer immunotherapy. Our aim is to improve the therapeutic efficacy of DC-based tumor vaccine by augmenting DC preferential chemotaxis on T cells. Mouse bone marrow-derived DC were transduced with lymphotactin (Lptn) gene by adenovirus vector. The supernatants from Lptn gene-modified DC (Lptn-DC) were capable of attracting CD4+ and CD8+ T cells in a chemotaxis assay, whereas their mock control could not. Lptn expression of Lptn-DC was further confirmed by RT-PCR. Lptn-DC were pulsed with Mut1 peptide and used for vaccination. Immunization with the low dose (1 x 10(4)) of Mut1 peptide-pulsed DC induced weak CTL activity, whereas the same amounts of Mut1 peptide-pulsed Lptn-DC markedly induced specific CTL against 3LL tumor cells. A single immunization with 1 x 10(4) Mut1 peptide-pulsed Lptn-DC could render mice resistant to a 5 x 10(5) 3LL tumor cell challenge completely, but their counterpart could not. The protective immunity induced by Mut1 peptide-pulsed Lptn-DC depends on both CD4+ T cells and CD8+ T cells rather than NK cells in the induction phase and depends on CD8+ T cells rather than CD4+ T cells and NK cells in the effector phase. Moreover, the involvement of CD28/CTLA4 costimulation pathway and IFN-gamma are also necessary. When 3LL tumor-bearing mice were treated with 1 x 10(4) Mut1 peptide-pulsed Lptn-DC, their pulmonary metastases were significantly reduced, whereas the same low dose of Mut1 peptide-pulsed DC had no obvious therapeutic effects. Our data suggest that Lptn-DC are more potent adjuvants for peptide delivery to induce protective and therapeutic antitumor immunity.

[The exchange and significance of the glucocorticoid receptor of circum-circulative blood lymphocyte of cases with allergic rhinitis]

It is found that the exceptional unity of blood Gr (Glucocorticoid Receptor) and F (Hydrocortisone) decreased obviously (P < 0.01) after the determination on them of circum-circulative blood lymphocyte of cases with allergic rhinitis. They showed positive interrelation, which means that the decrease of F and GR inhibited the anti-allergic action so that allergic rhinitis may occur.

Capillary zone electrophoresis at subzero temperatures. III. Operating conditions and separation efficiency

The advantages of carrying out capillary zone electrophoresis at subambient rather than ambient temperatures are examined. They include the possibility of using higher electric field strength and/or buffer concentration as well as wider capillary lumen without untoward effects of Joule heating on the separation. Furthermore, the separation efficiency is enhanced as molecular diffusivity decreases with temperature. A Beckman P/ACE unit with an auxiliary cooling system was used at temperatures down to -20 degrees C and, based on the dependence of axial temperature gradient on the capillary length and the temperature of the coolant, an average capillary temperature was defined. The day-to-day migration times of proteins were reproducible with an R.S.D. better than 2.3%. The improvements in the separation efficiency upon lowering the temperature from 40 to 1 degree C are illustrated by the electropherograms of four closely related peptides. Generally, the plate efficiency is enhanced at low temperatures and the analysis time is prolonged due to the increased viscosity. However, the current at a fixed electric field also decreases with temperature and the capillary can be shortened to speed up the analysis. With benzenesulfonic acids, the rate of the generation of theoretical plates was two- to three-times higher using a 27 cm long capillary at -15 degrees C than a 47 cm long capillary at 40 degrees C. By using a 180 microns instead of a 50 microns I.D. capillary for the separation of the four peptides, the sample loading could be increased about 15 times without loss of resolution. In the capillary zone electrophoresis of proteins, it was found that protein interactions with the capillary wall can be significantly reduced by increasing buffer concentration at low temperatures where salt mediated hydrophobic interactions are attenuated. This is illustrated by the separation of beta-lactoglobulins A and B in a raw fused-silica capillary using 400 mM sodium borate buffer, pH 8.4. The results suggest that at subambient or even subzero temperatures, the scope of CZE can be extended by several ways so that the benefits are great enough to justify the use of a cooling system and temperature control appropriate for psychroelectrophoresis with fused-silica capillaries.

Retinoblastoma protein expression and prognosis in laryngeal cancer

Expression of retinoblastoma (Rb) protein was immunohistochemically examined in laryngeal squamous cell neoplasias from 72 patients. Staining patterns were considered with reference to such prognostic factors as patient's age, histologic grade, tumour size and lymph node status, and 5-year survival rate. Rb protein negativity, either partial or complete, was noted in 28.8% of cases and was associated with a significantly lower 5-year survival rate, as well as with a higher likelihood of lymph node metastasis. This suggests that Rb alteration may be a prognostic indicator in patients with laryngeal carcinoma.

Glans sculpting in phalloplasty--experiences in female-to-male transsexuals

An aesthetically appealing neophallus with an urethral meatus at its tip is one of the goals of phalloplasty in female-to-male transsexuals. From July 1993 to December 1996, 20 cases of female-to-male transsexuals who had received sculpting of glans in four different ways were enrolled. Their photographs were collected and were scored by independent surgical and non-surgical assessors. The Norfolk procedure creates a more normal neoglans assessed by patients themselves and by the assessors. Split-thickness skin graft (SSG) produces a more normal-looking coronal sulcus than full-thickness skin graft (FTSG) in the Norfolk procedure.

[Preserving remnant liver function after major hepatic vein occlusion]

OBJECTIVE

To observe the pathological changes of the remained hepatic lobe after major hepatic vein (MHV) occlusion.

METHOD

Seventy-eight rats were randomly divided into the control group, the ligation group of segmental hepatic vein, the stricture group of left MHV, and the ligation group of left MHV. The pathology, hepatic microcirculation and hemodynamic changes of the involved hepatic lobe of MHV occlusion were dynamically determined.

RESULT

Necrosis occurred in the hepatocytes at the first postoperative day in the ligation group of MHV. Extensive collaterals between the hepatic veins and the portal veins appeared in the periphery of involved liver lobe in the stricture group of MHV. The levels of endotoxin and TXB(2)/6-Keto-PGF1alpha in the blood of portal vein obviously increased in the ligation group of MHV and also increased in the stricture group of MHV. The levels of endotoxin and TXB(2)/6-Keto-PGF1alpha in the blood of portal vein in the ligation and stricture group of MHV were apparently higher than those in the ligation group of segmental hepatic vein and in the control group.

CONCLUSION

The involved liver tissue can not tolerate complete MHV occlusion. The hepatic tissue lacking of MHV drain not only loss its function, but also cause endotoxemia and disorder of hepatic microcirculation. The involved hepatic lobe after the MHV ligation should have been resected at the same time.

[The significance of point-inflection at static pressure-volume curve in optimal PEEP at early stage of ARDS in sheep]

OBJECTIVE

To study the optimal level of PEEP at early stage of ARDS.

METHOD

The parameters of hemodynamics, lung mechanics, and gas exchange were compared at different levels of PEEP, including maximal static compliance PEEP, point-inflection PEEP, 3 cmH2O higher or lower than point-inflection PEEP, and zero end-expiratory pressure.

RESULTS

Point-inflection PEEP (6.8 +/- 1.4 cmH2O) was significantly lower than maximal static compliance PEEP (9.3 +/- 1.4 cmH2O), P < 0.01. The hemodynamic parameters were not significantly different in point-inflection PEEP compared with 0cmH2O-PEEP (P > 0.05), but oxygenation index (PaO2/FiO2) and lung mechanics (static compliance and airway resistance) were improved significantly at point-inflection PEEP (P < 0.01). At maximal static compliance PEEP or 3 cmH2O higher than point-inflection PEEP, the hemodynamic parameters and PaO2/FiO2 were not different from those at point-inflection PEEP (P > 0.05). The pulmonary vascular resistance index (PVRI) was significantly higher (P < 0.05) and the mean airway pressure and peak inspiratory pressure increased significantly (P < 0.01).

CONCLUSION

In the treatment of early ARDS, the PEEP needed may be lower than the "optimal PEEP" determined by obtaining the maximal static compliance. The application of point-inflection PEEP determined at inspiratory static pressure-volume curve was appropriate as the best PEEP.

[Detection of SMN gene deletions in spinal muscular atrophy]

OBJECTIVE

Survival motor neuron gene(SMN) and neuronal apoptosis inhibitory protein gene (NAIP) have been identified as the candidates of progressive spinal muscular atrophy (SMA)-determining genes. The aims of this study were to investigate the absence of SMN gene exon 7 in Chinese SMA patients, to confirm the relationship between the deletion of the SMN and SMA further, and to establish methods for gene diagnosis and prenatal diagnosis of SMA.

METHODS

PCR-SSCP with silver staining method was used to detect the genomic DNA of 37 SMA patients and 30 normal individuals for deletions of SMN exon 7.

RESULTS

Homozygous deletion of the SMN exon 7 was identified in 86.7%(13/15) of type I SMA patients and 86.4%(19/22) of type II patients. In the 88 controls (including parents of patients and normal individuals), homozygous absence of SMA exon 7 was only found in a mother of a patient.

CONCLUSION

The data support that homozygous absence of SMN exon 7 is strongly associated with SMA. The percentage of homozygous deletions in this study is almost as high as that reported by other researchers. This method is useful, reliable and effective for gene diagnosis and prenatal diagnosis of SMA.

Local interaction fields and adaptive regularizers for surface reconstruction and image relaxation

A set of novel local interaction fields associated with input point data and adaptive regularizers are introduced for some problems in image processing and early-middle vision. The local interaction field is used to take the place of the delta-error term in conventional approaches. It consists of two parts; one is the usual error term, the other is a window function whose shape, size and orientation can be adapted to local structures in specific applications. Unlike the usual delta-error term, local interaction fields favour local flatness and thus impose smoothing implicitly. Several adaptive regularizers are introduced to keep discontinuities while smoothing. In finding solutions, even the simplest gradient descent algorithm is efficient in many examples. The results are stable under varying parameters and quite robust against noise.

[Clinical study of physiologic work of breathing as a weaning parameter in mechanically ventilated patients]

OBJECTIVE

To evaluate the physiologic work of breathing (WOBphy) as a predicting Parameter of weaning and extubation.

METHODS

WOBphy was obtained by the patient's work of breathing (WOBt), minuting the imposed work of breathing (WOBimp). In weaning trial, if the patients could not meet predefined extubation criteria, but WOBphy < 0.70 J/L, the patients were also extubated immediately.

RESULTS

In a group of 28 patients who met the predefined criteria (group 1), 27 patients were successfully extubated. In another group of 13 patients who could not meet the criteria, but WOBphy < 0.70 J/L (group 2), extubation was successful in 12 patients. WOBt and WOBimp were significantly higher in group 2 (1.37 +/- 0.50 and 0.82 +/- 0.37 J/L) than group 1 (0.96 +/- 0.38 and 0.55 +/- 0.27 J/L, P < 0.05), while WOBphy was higher in group 2, but did not reach statistical significance.

CONCLUSIONS

WOBphy < 0.70 J/L may be safe as the weaning and extubation criterion and enables earlier extubation.

Phosphorylation-independent activity of the response regulators AlgB and AlgR in promoting alginate biosynthesis in mucoid Pseudomonas aeruginosa

Overproduction of the capsular polysaccharide alginate appears to confer a selective advantage for Pseudomonas aeruginosa in the lungs of cystic fibrosis patients. The regulators AlgB and AlgR, which are both required as positive activators in alginate overproduction, have homology with the regulator class of two-component environmental responsive proteins which coordinate gene expression through signal transduction mechanisms. Signal transduction in this class of proteins generally occurs via autophosphorylation of the sensor kinase protein and phosphotransfer from the sensor to a conserved aspartate residue, which is present in the amino terminus of the response regulator. Recently, kinB was identified downstream of algB and was shown to encode the cognate histidine protein kinase that efficiently phosphorylates AlgB. However, we show here that a null mutation in kinB in a mucoid cystic fibrosis isolate, P. aeruginosa FRD1, did not block alginate production. The role of the conserved aspartate residue in the phosphorylation of AlgB was examined. The predicted phosphorylation site of AlgB (D59) was mutated to asparagine (N), and a derivative of an AlgB lacking the entire amino-terminal phosphorylation domain (AlgB delta1-145) was constructed. A hexahistidine tag was included at the amino terminus of the wild-type (H-AlgB), H-AlgB delta1-145, and mutant (H-AlgB.59N) AlgB proteins. These derivatives were purified by Ni2+ affinity chromatography and examined for in vitro phosphorylation by the purified sensor kinase protein, KinB. The results indicated that while KinB efficiently phosphorylated H-AlgB, no phosphorylation of H-AlgB delta1-145 or H-AlgB.D59N was apparent. An allelic exchange system was developed to transfer mutant algB alleles onto the chromosome of a P. aeruginosa algB mutant to examine the effect on alginate production. Despite the defect in AlgB phosphorylation, P. aeruginosa strains expressing AlgB.D59N or H-AlgB delta1-145 remained mucoid. The roles of the conserved aspartate residues in the phosphorylation of AlgR were also examined. As seen with AlgB, mutations in the predicted phosphorylation site of AlgR (AlgR.D54N and AlgR.D85N) did not affect alginate production. These results indicate that in vivo phosphorylation of AlgB and AlgR are not required for their roles in alginate production. Thus, the mechanism by which these response regulators activate alginate genes in mucoid P. aeruginosa appears not to be mediated by conventional phosphorylation-dependent signal transduction.

Research on the schizont cell culture vaccine against Theileria annulata infection in Xinjiang, China

Theileria annulata infection (TAI) is one of the most serious diseases of cattle in Xinjiang Autonomous Region of Uigur Minority Nationality. It has been recorded in 14 prefectures, except the Tulufan Prefecture, but the enzootic areas are mainly distributed around the Zhunger Basin and Talim Basin. According to the records collected in the ten years before vaccination with the schizont cell culture vaccine was carried out, the average incidence rate of TAI in enzootic areas was 7.22% and the mortality rate was 24%. The milk production of cattle suffering from TAI was sharply decreased, and there were usually abortions in pregnant cows. The incidence rate and mortality rate were greater in high grade cattle, so TAI was a constraint to improving cattle breeds. To control this disease effectively in Xinjiang, researchers at the Xinjiang Academy of Animal Science began to study the schizont cell culture vaccine in 1972. In 1977 an immortalised cell line was achieved from a primary cell culture starting with white blood cells from cattle suffering from acute TAI caused by an artificial tick bite. The cell culture medium mainly consisted of calf serum, lactalbumin-hydrolysate, Eagles' medium DMEM and three antibiotics. As a vaccine, the above cells were mixed with preserving medium containing gelatin. This paper describes the experiments on the immunological properties of the vaccine carried out in subsequent years. Up to 1996, vaccine doses for 1,186,150 cattle have been produced and sold. This vaccine has had a critical effect on the control of TAI in Xinjiang. Owing to the sharp decrease in the incidence rate and mortality rate of TAI after cattle were vaccinated, the annual economic benefit of the vaccine is at least 1,620,000 yuan.

[Carcinoma metastatic to the cervix: a study of 19 cases]

OBJECTIVES

To report the clinical features and to evaluate the treatment results of 19 cases of cervical metastatic carcinoma.

METHODS

We analyzed retrospectively the 19 patients with carcinoma metastatic to the cervix treated during the period of 1959 to 1994 at Cancer Hospital, Chinese Academy of Medical Sciences.

RESULTS

The average age of patients was 43.7. The main symptom was irregular vaginal discharge and (or) bleeding. In most patients, the primary cancers originated from digestive tract or ovary. The treatment methods included radiotherapy alone, radiotherapy combined with chemotherapy after operation, and surgery plus radiotherapy. The 1-, 2- and 5-years survival rates (life-time table were 68.5%, 47.3% and 26.2% respectively, and the longest period for survived patient with dysgerminoma has lived was more than 22 years.

CONCLUSION

The active proper treatment of primary cancer can prolong the survival time of patients with carcinoma metastatic to the cervix. The patients whose metastatic lesions are limited to the cervix and sensitive to the radiation may be cured by radiotherapy and combination therapy.

Genetic construction and characterization of an anti-monkey CD3 single-chain immunotoxin with a truncated diphtheria toxin

We have previously developed a chemically conjugated anti-rhesus monkey CD3 immunotoxin FN18-CRM9 that can deplete in vivo T cells and induce long term tolerance of mismatched renal allograft in rhesus monkeys. This immunotoxin is a monkey analogue of anti-human CD3 immunotoxin UCHT1-CRM9. In this study, we cloned the light and heavy chain variable regions of anti-monkey CD3 monoclonal antibody FN18 and constructed a single-chain Fv (sFv) by linking variable light and variable heavy regions with a (Gly4Ser)3 linker. The single-chain immunotoxin DT390-FN18sFv was constructed by ligating the sFv to the carboxyl terminus of DT390, a truncated form of diphtheria toxin. The DT390-FN18sFv fusion protein was expressed in Escherichia coli and purified with Ni-RTA affinity and anion exchange columns. Similar to the chemically conjugated immunotoxin FN18-CRM9, DT390-FN18sFv can also specifically inhibit protein synthesis in primary monkey T cells in a dose-dependent manner. DT390-FN18sFv at 10(-7) mol/L or FN18-CRM9 at 10(-8) mol/L is sufficient to reduce protein synthesis of monkey primary T cells to less than 5% of the control. The 50% inhibition dosage (IC50) of FN18-CRM9 is 1 x 10(-10) mol/L, while the IC50 of DT390-FN18sFv is 1 x 10(-8) mol/ L, reflecting the lowered affinity of monovalent Fab' FN18 to its parental divalent antibody. The availability of functional FN18sFv will provide the basis for the construction of divalent anti-CD3 immunotoxins for preclinical studies on the induction of tolerance in organ transplantation and experimental autoimmune diseases.