[Bcl-2/JH gene re-arrangement determined by PCR as a means to detect minimal residual disease in malignant lymphomas]

OBJECTIVE

To develop a sensitive method to detect minimal residual disease and to elucidate the significance of bcl-2 gene rearrangement in diagnosis and therapy of malignant lymphoma.

METHODS

Using polymerase chain reaction(PCR) to detect bcl-2 gene rearrangement and using serial dilution method to define the sensitivity of PCR.

RESULTS

In 9 different malignant lymphoma cell lines, Su-DHL-4 and Su-DHL-6 were shown bcl-2(MBR)/JH rearrangement, the sensitivity of PCR was 1:10(5). In 16 patients with follicular lymphoma, the peripheral blood and bone marrow were PCR positive in 4 both at initial diagnosis and after complete remission.

CONCLUSION

Detection of bcl-2 gene rearrangement by PCR provides a sensitive and specific assay of minimal residual disease. It helps improve staging of disease, stratification and evaluation of treatment.

[Analysis of the density of insulin-like growth factor-1 receptor on tendon cell]

For the purpose of understanding the distribution of insulin-like growth factor-1 (IGF-1) receptor on the tendon cell, the continuous cultured tendon cell line was studied by following experiments. With the methods of immunohistochemical study and flow cytometric study, the density of IGF-1 receptor of the primary, 6th and 13th generation of tendon cell was analyzed. The results showed that there was no difference of the receptor density among those generations. However, in the cell cycle, the numbers of IGF-1 receptor in G2M phase tendon cells were more than that in G1 phase cells (P < 0.01). These works provided sufficient evident which suggested there were stable density of IGF-1 receptor on the tendon cell though out the life span of tendon cell. This may build some foundation in growth control of tendon cell by growth factor in the research of tendon tissue engineering.

Complex synaptic current waveforms evoked in hippocampal pyramidal neurons by extracellular stimulation of dentate gyrus

Excitatory postsynaptic currents (EPSCs) evoked in hippocampal CA3 pyramidal neurons by extracellular stimulation of the dentate gyrus typically exhibit complex waveforms. They commonly have inflections or notches on the rising phase; the decay phase may exhibit notches or other obvious departures from a simple monoexponential decline; they often display considerable variability in the latency from stimulation to the peak current; and the rise times tend to be long. One hypothesis is that these complex EPSC waveforms might result from excitation via other CA3 pyramidal cells that were recruited antidromically or trans-synaptically by the stimulus due to the complex anatomy of this region. An alternative hypothesis is that EPSC complexity does not emerge from the functional anatomy but rather reflects an unusual physiological property, intrinsic to excitation-secretion coupling in mossy-fiber (mf) synaptic terminals, that causes asynchronous quantal release. We evaluated certain predictions of our anatomic hypothesis by adding a pharmacological agent to the normal bathing medium that should suppress di- or polysynaptic responses. For this purpose we used baclofen (3 microM), a selective agonist for the gamma-aminobutyric acid B receptor. The idea was that baclophen should discriminate against polysynaptic versus monosynaptic inputs by hyperpolarizing the cells, bringing them further from spike threshold and possibly also through inhibitory presynaptic actions. Whole cell recordings were done from visually preselected CA3 pyramidal neurons and EPSCs were evoked by fine bipolar electrodes positioned into the granule cell layer of the dentate. To the extent that the EPSC complexity reflects di- or polysynaptic responses, we predicted baclofen to reduce the number of notches on the rising and decay phases, reduce the variance in latency to peak of the EPSCs, decrease the amplitudes and rise times of the individual and averaged EPSCs, and increase the apparent failures in evoked EPSCs. All of these predictions were confirmed, in support of the hypothesis that these complex EPSC waveforms commonly reflect di- or polysynaptic responses. We also documented a distinctly different, intermittent, form of EPSC complexity, which also is predicted and easily explained by our anatomic hypothesis. In particular, the results were in accord with the suggestion that stimulation of the dentate gyrus might antidromically stimulate axon collaterals of CA3 neurons that make recurrent synapses onto the recorded cell. We conclude that the overall pattern of results is consistent with expectations based on the functional anatomy. The explanation does not demand a special type of intrinsic asynchronous mechanism for excitation-secretion coupling in the mf synapses.

Effect of passive immunization or maternally transferred immunity on the antibody response to a genetic vaccine to rabies virus

A plasmid vector, termed pSG5rab.gp, expressing the glycoprotein of rabies virus was tested in young adult or neonatal mice in the presence of maternally transferred immunity or passively administered antibodies to rabies virus for induction of an antibody response. Mice born to rabies virus-immune dams developed an impaired antibody response to genetic immunization at 6 weeks of age, as had been previously observed upon vaccination with an inactivated viral vaccine. Similarly, mice passively immunized with hyperimmune serum showed an inhibited B-cell response upon vaccination with the pSG5rab.gp vector, resulting in both cases in vaccine failures upon challenge with a virulent strain of rabies virus. In contrast, the immune responses of mice vaccinated as neonates in the presence of maternal immunity or upon passive immunization to rabies virus with the pSG5rab.gp construct were only marginally affected.

GABAA receptor-mediated currents in interneurons and pyramidal cells of rat visual cortex

1. We compared gamma-aminobutyric acid (GABA)-mediated responses of identified pyramidal cells and fast spiking interneurons in layer V of visual cortical slices from young rats (P11-14). 2. The frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) was similar in pyramidal cells and interneurons (1.7 vs. 1.9 Hz). For events with 10-90% rise times less than 0.9 ms, no significant differences were found in mean amplitude (61 vs. 65 pA), mean rise time (0.58 vs. 0.61 ms), or the first time constant of decay (tau 1, 6.4 vs. 6.5 ms) between pyramidal cells and interneurons. The second decay time constant (tau 2) was significantly longer in interneurons than in pyramidal cells (49 vs. 22 ms). The difference in sIPSC decay kinetics between two cell types also existed in adult rats (P36-42), suggesting the kinetic difference in not due to differential development of GABAA receptors in these cell types. 3. The decay kinetics of monosynaptic evoked IPSCs were also longer in interneurons. As in the case of sIPSCs, the difference was accounted for by the second decay time constant. tau 1 and tau 2 were, respectively, 13 and 64 ms for interneurons and 12 and 47 ms for pyramidal cells. 4. Cell-attached patch recordings revealed that the mean open time for single Cl- channels in response to 2 microM GABA was significantly longer in interneurons than pyramidal cells (5.0 vs. 2.8 ms). The chord conductance of these channels in interneurons (12 pS) was significantly smaller than in pyramidal cells (15 pS). Single channel currents reversed polarity when the pipette potential was approximately -10 mV for both cell types. 5. These results show that there is a functional diversity of GABAA receptors in electrophysiologically and morphologically identified cortical pyramidal cells and interneurons. This diversity might derive from the different molecular composition of the receptors in these two cell types.

[The effect of blocking insulin-like growth factor-1 (IGF-1)-receptor system on tendon cell proliferation]

The purpose of this study was to find some solutions to the problem of tendon cell proliferation control. Under the condition of in vitro culture, several materials including IGF-1 receptor antibody and mRNA antisense oligonucleotide were added to the culture medium to block the IGF-1-Receptor system. The effect of the material on the tendon cell proliferation was judged by cell count after incubation of 48 hours. The results showed that both IGF-1 Receptor antibody (IGF-1R alpha) and IGF-1 Receptor mRNA antisense oligonucleotide had negative effect on tendon cell proliferation (P < 0.01 and P < 0.05). These findings lead us to think that the above two materials could be used in the experiment of tendon adhesion preventing and living ready-made tendon producing.

Study on the relationship between the Bcl-2/Bax ratio and the growth types of leukemic cells and drug resistance in acute myelogenous leukemia

The ratio of Bcl-2 to Bax (Bcl-2/Bax) in 40 patients with acute myelogenous leukemia (AML) were determined. At the same time, the CFU-L of AML patients and drug resistance were detected by cell culture and MTT assay. The results showed that Bcl-2/Bax in AML was significantly higher than that in normal control (P < 0.001). Bcl-2/Bax ratio in colony growth group was higher than that in no-growth group (P < 0.05). Between drug resistance group and drug sensitivity group there was a significant difference in Bcl-2/Bax ratio (P < 0.05). There were more cases of drug resistance in high ratio group (H) than in low ratio group (L) (P < 0.05). Meanwhile, Complete Remission(CR) rate in group H was obviously lower than that in group L (P < 0.05) and patients in group H tended to have poor response. The above results indicated that the alteration of Bcl-2 and Bax is an important mechanism in the pathogenesis, progress and the development of drug resistance in AML. The determination of Bcl-2/Bax ratio has far-reaching implication in the treatment, choice of chemotherapeutic agents, and prediction of prognosis.

[The expression of IGF-1 and its receptor in cultured tendon cell]

In order to study the expression change of insulin-like growth factor-1 (IGF-1) and its receptor genes in different generations of tendon cell in culture, Dig-labeled synthesized oligonucleotide probes were used to detect the mRNA expression in primary, 6th and 13th generation of tendon cell. The results showed that IGF-1 receptor mRNA was expressed in all of the 3 above generation tendon cells. IGF-1 mRNA was expressed only in primary and 6th generation cells. Tendon cell of 13th generation did not express IGF-1 mRNA. It might suggest that the absence of IGF-1 mRNA expression be one of the causes which led to the decrease of reproductive ability of 13th generation tendon cell.

[The effect of insulin-like growth factor-1 on cyclic change of tendon cell]

In order to investigate the effect of insulin-like growth factor-1 (IGF-1 on the cyclic change of tendon cell, the 6th generation of cultured tendon cell were selected, and 20 ng/ml IGF-1 was added to the medium. After 48 hours, the cells were determined by flow cytometer, as well as the control cells. The results showed that the time of G1 phase, DNA synthesis phase and G2M phase in IGF-1 group were 11.8 hours, 21.4 hours and 6.8 hours respectively, while those were 25.6 hours 22.6 hours and 21.8 hours respectively in the control group. It was showed that the time needed for G1 phase and G2M phase was shortened by IGF-1.

Human mast cells express functional TrkA and are a source of nerve growth factor

Mast cells are the principal effector cells in IgE-dependent hypersensitivity reactions. Despite reports that rodent mast cells proliferate in the presence of nerve growth factor (NGF), human mast cells reportedly do not respond to this factor. To determine if human mast cells express the NGF receptors, TrkA tyrosine receptor and the low affinity NGF receptor (LNGFR), we first analyzed the mRNA expression by RT-PCR of TrkA and LNGFR in a human mast cell line (HMC-1) and in human mast cells cultured in the presence of stem cell factor. Both HMC-1 and cultured human mast cells were found to express TrkA but not LNGFR. TrkA protein was demonstrated by Western blot analysis of HMC-1 lysates. Using flow cytometric analysis and mast cell tryptase as a mast cell marker, both HMC-1 cells and cultured human mast cells were shown to coexpress tryptase and TrkA. Treatment of mast cells with NGF resulted in phosphorylation of TrkA on tyrosine residues as detected by immunoblotting with an antiphosphotyrosine antibody. Furthermore, NGF induced the immediate early gene c-fos in HMC-1 cells. HMC-1 cells and cultured human mast cells were also found to express NGF mRNA, and conditioned medium from HMC-1 cells stimulated neurite outgrowth from chicken embryonic sensory ganglia in culture. This effect was blocked by anti-NGF. Thus, mast cells express functional TrkA and synthesize NGF, suggesting a mechanism by which NGF may act as an autocrine factor for human mast cells, and by which mast cells and nerves may interact.

Cytokines and costimulatory molecules as genetic adjuvants

DNA vectors expressing an antigen derived from a pathogen or a cancerous cell have been shown, after inoculation into experimental animals, to trigger de novo synthesis of foreign proteins, which induce an immune response. This immune response can be modulated by coinoculation of vectors encoding either cytokines or costimulatory molecules. A variety of cytokines such as granulocyte/macrophage colony-stimulating factor (GM-CSF), IL-2, IL-4, IL-12 and IFN-gamma, as well as the costimulatory molecule B7.1, have been tested to date for their ability to amplify the immune response to genetic vaccines. Although the results obtained thus far clearly show that coadministration of vectors expressing immunomodulatory molecules, such as cytokines, may increase the efficacy of genetic vaccines, this approach is currently considered unsuitable for use in human patients due to the potential side effects of persistent cytokine expression.

The use of an E1-deleted, replication-defective adenovirus recombinant expressing the rabies virus glycoprotein for early vaccination of mice against rabies virus

An E1-deleted, replication-defective adenovirus recombinant of the human strain 5 expressing the rabies virus glycoprotein, termed Adrab.gp, was tested in young mice. Mice immunized at birth with the Adrab.gp construct developed antibodies to rabies virus and cytokine-secreting lymphocytes and were protected against subsequent challenge. Maternal immunity to rabies virus strongly interferes with vaccination of the offspring with a traditional inactivated rabies virus vaccine. The immune response to the rabies virus glycoprotein, as presented by the Adrab.gp vaccine, on the other hand, was not impaired by maternal immunity. Even neonatal immunization of mice born to rabies virus-immune dams with Adrab.gp construct resulted in a long-lasting protective immune response to rabies virus, suggesting that this type of vaccine could be useful for immunization shortly after birth. Nevertheless, pups born to Adrab.gp virus-immune dams showed an impaired immune response to the rabies virus glycoprotein upon vaccination with the Adrab.gp virus, indicating that maternal immunity to the vaccine carrier affected the offspring's immune response to rabies virus.

HIV type 2 pathogenicity is not related to subtype in rural Guinea Bissau

Data from an MRC case-control study in rural Guinea Bissau suggest older HIV-2 carriers (aged 55 to 80 years) appear, over a period of 2 years, to have a mortality similar to that of uninfected controls, whereas in HIV-2 carriers under the age of 55 there is a significantly higher mortality, compared with uninfected controls. Genotyping of viruses from both groups revealed only subtype a to be circulating. Thus, although putative nonpathogenic HIV-2 subtypes have been described in patients from West Africa, these do not appear to be contributing significantly to the nonpathogenic clinical phenotype in this population.

Immune response to neonatal genetic immunization

The effect of genetic immunization of neonatal mice was tested with a plasmid vector expressing the rabies virus glycoprotein. Mice inoculated within 24 hr after birth with the plasmid DNA developed antibodies as well as T helper cells to the rabies virus glycoprotein. The response could not be distinguished from that seen upon vaccination of adult mice. Taken together, these data clearly show that the immune system, known to be prone to induction of immunological tolerance to some antigens applied during the early neonatal period, can readily respond to rabies virus glycoprotein induced by a plasmid vector.

cag, a pathogenicity island of Helicobacter pylori, encodes type I-specific and disease-associated virulence factors

cagA, a gene that codes for an immunodominant antigen, is present only in Helicobacter pylori strains that are associated with severe forms of gastroduodenal disease (type I strains). We found that the genetic locus that contains cagA (cag) is part of a 40-kb DNA insertion that likely was acquired horizontally and integrated into the chromosomal glutamate racemase gene. This pathogenicity island is flanked by direct repeats of 31 bp. In some strains, cag is split into a right segment (cagI) and a left segment (cagII) by a novel insertion sequence (IS605). In a minority of H. pylori strains, cagI and cagII are separated by an intervening chromosomal sequence. Nucleotide sequencing of the 23,508 base pairs that form the cagI region and the extreme 3' end of the cagII region reveals the presence of 19 ORFs that code for proteins predicted to be mostly membrane associated with one gene (cagE), which is similar to the toxin-secretion gene of Bordetella pertussis, ptlC, and the transport systems required for plasmid transfer, including the virB4 gene of Agrobacterium tumefaciens. Transposon inactivation of several of the cagI genes abolishes induction of IL-8 expression in gastric epithelial cell lines. Thus, we believe the cag region may encode a novel H. pylori secretion system for the export of virulence determinants.

Novel vaccine approaches

Recent advances in immunology, molecular biology, and peptide biochemistry have allowed the construction of subunit vaccines based on viral or bacterial recombinants, peptides or plasmid vectors. Although none of these approaches is currently being used for mass vaccination (with the exception or vaccinia-rabies G protein recombinant virus for wildlife immunization); several of them are undergoing clinical trials. None of these different vaccine constructs is likely to be totally effective in either the prevention of infectious diseases or immunotherapy of cancer. Recombinant viral vaccines such as those based on vaccinia or adenovirus as a rule induce potent immune responses. Vaccinia viruses have the added advantage of being heat stable and immunogenic after oral application, making them good candidates for wildlife immunization. Recombinants based on replication-defective adenoviruses are safer compared with vaccinia virus recombinants and, as far as our data indicate, have superior efficacy. In addition, they induce excellent immunity upon application to mucosal membranes, suggesting their usefulness as vaccines for infectious agents that enter through the airways or the genital tract. Peptides are of limited benefit in infectious disease prevention but might provide custom-made vaccines for cancer therapy. Genetic vaccines that were first described less than 5 years ago have already progressed to phase I clinical trials in healthy human adults. Provided that their safety can be confirmed, they might be suited to induce immunity to numerous agents.

Novel vaccine approaches

Recent advances in immunology, molecular biology, and peptide biochemistry have allowed the construction of subunit vaccines based on viral or bacterial recombinants, peptides or plasmid vectors. Although none of these approaches is currently being used for mass vaccination (with the exception or vaccinia-rabies G protein recombinant virus for wildlife immunization); several of them are undergoing clinical trials. None of these different vaccine constructs is likely to be totally effective in either the prevention of infectious diseases or immunotherapy of cancer. Recombinant viral vaccines such as those based on vaccinia or adenovirus as a rule induce potent immune responses. Vaccinia viruses have the added advantage of being heat stable and immunogenic after oral application, making them good candidates for wildlife immunization. Recombinants based on replication-defective adenoviruses are safer compared with vaccinia virus recombinants and, as far as our data indicate, have superior efficacy. In addition, they induce excellent immunity upon application to mucosal membranes, suggesting their usefulness as vaccines for infectious agents that enter through the airways or the genital tract. Peptides are of limited benefit in infectious disease prevention but might provide custom-made vaccines for cancer therapy. Genetic vaccines that were first described less than 5 years ago have already progressed to phase I clinical trials in healthy human adults. Provided that their safety can be confirmed, they might be suited to induce immunity to numerous agents.

Atrophic nonunion can be predicted with dual energy x-ray absorptiometry in a canine ostectomy model

This study demonstrated that dual energy x-ray absorptiometry can be used to distinguish between normal union and atrophic nonunion, with high sensitivity and high negative predictive value, by 8 weeks after surgery in a canine model. Eighteen adult mixed-breed dogs were divided into two equal groups: normal union and atrophic nonunion. In the normal union group, a 5 mm mid-diaphyseal transverse ostectomy was performed in the right tibia, and the bone was stabilized with a unilateral external fixator. In the atrophic nonunion group, a 5 mm mid-diaphyseal ostectomy was performed; the distal 1.5 cm of the bone ends, including the periosteum, were frozen twice to -20 degrees C using liquid nitrogen and thawed slowly twice; and the bone was stabilized with a unilateral external fixator. The members of the research team were blinded to the group assignments until after all dogs were killed and all data were acquired. Radiography and dual energy x-ray absorptiometry of both tibiae were performed at weeks 1, 2, 3, 4, 6, 8, 10, 12, 14, and 16 after surgery. All dogs were killed at 16 weeks, and the torsional stiffness and maximum torque of both tibiae of five dogs in each group were determined. Mechanically, the tibiae in the normal union group had significantly higher maximum torque (43-fold higher) and torsional stiffness (86-fold higher) than the tibiae in the atrophic nonunion group. The sensitivity and negative predictive value of dual energy x-ray absorptiometry for predicting nonunion were 100% by 8 weeks after surgery. The specificity and positive predictive value reached 78 and 82%, respectively, by 16 weeks. Radiographic scores were significantly higher for the union group than for the nonunion group beginning at 2 weeks after surgery. The earliest time after surgery that radiography classified an ostectomy as a nonunion was significantly later (4.6 +/- 1.2 weeks) than for dual energy x-ray absorptiometry (2.6 +/- 1.4 weeks). Before these results can be extrapolated to human applications, further animal studies must be performed to evaluate clinically or experimentally induced fractures, or both, rather than the well defined ostectomies that were performed in this study.

Induction of interleukin-8 secretion from gastric epithelial cells by a cagA negative isogenic mutant of Helicobacter pylori

The ability of Helicobacter pylori strains to induce interleukin-8 (IL-8) gene expression and protein secretion from gastric epithelial cell lines in vitro is variable. This cellular response is associated with bacterial expression of the CagA protein present in type I H pylori strains. To determine the role of CagA in this host cell response, an isogenic cagA negative mutant, N6.XA3, was constructed. The cagA negative isogenic mutant and the wild-type parental cagA positive strain, N6, were cocultured with AGS, ST-42 and KATO-3 gastric epithelial cell lines and secreted interleukin-8 assayed by enzyme linked immunosorbent assay. In all three cell lines there was no significant difference in the IL-8 secretion induced by the cagA negative isogenic mutant, N6.XA3, and the wild-type parent strain, N6. These studies show that CagA is not the inducer of IL-8 secretion from gastric epithelial cells. As all wild-type CagA positive strains studied to date induce IL-8, the bacterial factor(s) inducing this inflammatory response is closely associated with the expression of CagA.

Upregulation of class I major histocompatibility complex antigens by interferon gamma is necessary for T-cell-mediated elimination of recombinant adenovirus-infected hepatocytes in vivo

Recombinant adenoviruses are attractive vehicles for liver-directed gene therapy because of the high efficiency with which they transfer genes to hepatocytes in vivo. First generation recombinant adenoviruses deleted of E1 sequences also express recombinant and early and late viral genes, which lead to development of destructive cellular immune responses. Previous studies indicated that class I major histocompatibility complex (MHC)-restricted cytotoxic T lymphocytes (CTLs) play a major role in eliminating virus-infected cells. The present studies utilize mouse models to evaluate the role of T-helper cells in the primary response to adenovirus-mediated gene transfer to the liver. In vivo ablation of CD4+ cells or interferon gamma (IFN-gamma) was sufficient to prevent the elimination of adenovirus-transduced hepatocytes, despite the induction of a measurable CTL response. Mobilization of an effective TH1 response as measured by in vitro proliferation assays was associated with substantial upregulation of MHC class I expression, an effect that was prevented in IFN-gamma-deficient animals. These results suggest that elimination of virus-infected hepatocytes in a primary exposure to recombinant adenovirus requires both induction of antigen-specific CTLs as well as sensitization of the target cell by TH1-mediated activation of MHC class I expression.

Bromodeoxyuridine immunohistochemistry of epon-embedded undecalcified bone in a canine fracture healing model

We evaluated bromodeoxyuridine (BrdU) immunohistochemistry of paraffin-, methyl methacrylate (MMA)-, and epon-araldite (epon)-embedded canine bone specimens to establish an optimal technique for studying cell kinetics of fracture healing in a canine tibial gap model. Dogs were sacrificed 4 months after tibial ostectomy and 1 hr after i.v. injection of BrdU (100 mg/kg). BrdU immunohistochemical staining with a peroxidase-labeled streptavidin-biotin (LAB-SA) method was performed on thin sections of tibia fixed in 70% ethanol and embedded in paraffin, MMA, or epon. Thin section of small intestines fixed in 70% ethanol and 10% neutral buffered formalin and embedded in paraffin, MMA, or epon were BrdU-stained and served as a model for proliferating tissue. Good and consistent BrdU immunostaining without detachment of bone sections was obtained for epon-embedded undecalcified bone sections. BrdU-positive cells were easily identifiable, in contrast to negligible background staining. BrdU-labeled osteoprogenitor cells and osteoblasts were observed around and on the surface of woven bone in external and internal callus of the ostectomy gap. Nuclei of osteocytes were not labeled. In contrast to the epon-embedded specimens, BrdU immunostaining of paraffin-embedded decalcified and MMA-embedded undecalcified bone specimens was unsatisfactory. The results of this study suggest that BrdU immunohistochemistry of ethanol-fixed, epon-embedded, undecalcified canine bone sections is a technique suitable for study of fracture healing with the described methodology.

Helicobacter pylori-specific CD4+ T-cell clones from peripheral blood and gastric biopsies

Colonization of human gastric mucosa with cytotoxic strains of the bacterium Helicobacter pylori is associated with peptic ulcer and with chronic gastritis. Since little is known about the T-cell response to H. pylori, we investigated the CD4+ T-cell response both in peripheral blood mononuclear cells (PBMCs) and at the site of infection. First, we compared the bulk PBMC proliferative response to the bacterium in individuals with and without symptoms of gastroduodenal disease. We found that the PBMCs from virtually all individuals proliferate in response to heat-inactivated bacteria. Second, we cloned H. pylori-specific CD4+ T lymphocytes from the PBMCs of three patients and from both the gastric mucosa and PBMCs of a fourth patient. We have found that CD4+ T-cell clones specific for H. pylori from peripheral blood samples and gastric mucosae of infected patients are major histocompatibility complex class II restricted and discriminate between several cytotoxic and noncytotoxic bacterial strains. Moreover, they are polyclonal in terms of T-cell receptor usage and major histocompatibility complex restriction. Our results demonstrate that the T-cell response to the whole bacterium in PBMCs does not correlate with antibody response, infection, or disease. However, H. pylori-specific CD4+ T cells are detectable, at the clonal level, in both the periphery and gastric mucosa of infected patients. Localization of these cells at the site of disease suggests they are effectors of the immune response to the bacteria.

Analysis of expression of CagA and VacA virulence factors in 43 strains of Helicobacter pylori reveals that clinical isolates can be divided into two major types and that CagA is not necessary for expression of the vacuolating cytotoxin

Colonization of the mucosa of the stomach and the duodenum by Helicobacter pylori is the major cause of acute and chronic gastroduodenal pathologies in humans. Duodenal ulcer formation strongly correlates with the expression of an antigen (CagA) that is usually coeexpressed with the vacuolating cytotoxin (VacA), a protein that causes ulceration in the stomach of mice. However, the relationship between these two virulence factors is unknown. To define whether CagA and VacA are coexpressed in all clinical isolates and their relationships, we collected 43 clinical isolates of H. pylori and studied their genetic and phenotypic properties. Based on this analysis, most of the strains could be classified into two major types. Type I bacteria had the gene coding for CagA and expressed the CagA protein and the vacuolating cytotoxin. Type II bacteria did not have the gene coding for CagA and did not express either the CagA protein or the vacuolating cytotoxin. Type I and type II bacteria represented 56 and 16%, respectively, of the 43 clinical isolates, while the remaining 28% had an intermediate phenotype, expressing CagA independently of VacA or vice versa. This finding shows that although it is present in most cytotoxic strains, CagA is not necessary for the expression of the vacuolating cytotoxin.

Manipulation of the immune response to a plasmid-encoded viral antigen by coinoculation with plasmids expressing cytokines

Inoculation of plasmid vectors encoding a viral protein into muscle tissue was shown to result in expression of the transantigen and, consequently, an antiviral immune response. Here, we show that coinoculation of a plasmid expressing the glycoprotein of rabies virus with plasmids encoding mouse cytokines modulated the immune response to the viral protein. Coinoculation with a vector expressing mouse granulocyte-macrophage colony-stimulating factor (GM-CSF) enhanced the B and T helper cell activity to rabies virus, while coinoculation with a plasmid expressing interferon-gamma (IFN gamma) resulted in a decrease of the immune response to the viral antigen.