Recombinant Listeria monocytogenes as a live vaccine vehicle and a probe for studying cell-mediated immunity

The ability of Listeria monocytogenes (L. monocytogenes) to enter the cytosol of host cells allows secreted proteins to efficiently enter the endogenous antigen-processing pathway leading to presentation by MHC class I molecules. L. monocytogenes has recently been exploited as a live vaccine vehicle for the induction of immunological memory against heterologous antigens. We have established a genetic system for site-specific integration of antigen expression cassettes into the Listeria genome which allows regulated expression and secretion of heterologous proteins. The ability of recombinant strains to stimulate long-term immunological memory and CD8+ T-cell-mediated protective immunity was investigated using the lymphocytic choriomeningitis virus (LCMV) murine infection model. Vaccination of mice with recombinant Listeria strains expressing LCMV antigens induced LCMV-specific CD8+ T cells which protected mice against LCMV challenge. We have also used a cottontail rabbit papillomavirus model to test the ability of recombinant Listeria strains to stimulate protective antitumor immunity in domestic rabbits. These studies have demonstrated the protective efficacy of recombinant L. monocytogenes vaccines and have established an experimental system for systematic analysis of cytotoxic T-cell induction by an intracellular bacterium.

A case of hyperzincemia with functional zinc depletion: a new disorder?

We report the case of an 1l-y-old boy with a plasma Zn concentration greater than 200 micromol/L, but with symptoms consistent with Zn deficiency. He has had hepatosplenomegaly, rashes, stunted growth (<3rd centile), anemia, and impaired immune function since infancy. He also has vasculitis and osteoporosis. A plasma Zn-binding protein has been separated and characterized by a combination of size exclusion and ion exchange chromatography and electrophoretic studies and by immunologic methods. Antibodies to the partially purified protein have been raised in rabbits. Size exclusion chromatography shows that Zn is bound to a protein with a mass 110000-300000 kD. Electrophoretic and mass spectrometry studies suggest that the protein may be composed of several subunits. One component of the isolated protein reacts with antiserum to alpha2-macroglobulin; immunoprecipitation studies confirm that the protein is not alpha2-macroglobulin or a histidine-rich glycoprotein. Kinetic studies of zinc metabolism in the patient and his mother with stable Zn isotopes show the presence of increased exchangeable Zn, with a rapid flux from plasma to a stable pool. Liver and muscle Zn and Cu concentrations are raised, but with no abnormal liver histology. Immunoreactive metallothionein in the liver is increased. We suggest that this boy may suffer from a previously unrecognized inborn error of Zn metabolism causing symptomatic zinc deficiency.

Regression of papillomas induced by cottontail rabbit papillomavirus is associated with infiltration of CD8+ cells and persistence of viral DNA after regression

Cottontail rabbit papillomavirus (CRPV) is a highly oncogenic papillomavirus and has been successfully used as a model to develop protective vaccines against papillomaviruses. Papillomas induced by the virus may spontaneously regress, suggesting that CRPV can also serve as a model to develop therapeutic vaccines. As a first step toward this goal, we have analyzed immunologic and viral aspects associated with papilloma regression and have identified several features unique to regression. Immunohistochemical staining of biopsies from growing and regressing papillomas and from sites after complete regression showed infiltration of CD8+ cells into the basal and suprabasal layers of the epidermis only during active regression. In situ hybridizations with mRNA-specific probes were strongly positive for E6 and E7 mRNAs during regression, but no late mRNA was present. Viral DNA was detected by in situ hybridization during regression but not after regression. However, analysis by PCR revealed persistence of viral DNA for several months at the majority of regression sites. The results suggest that stimulation of a strong CD8+ response to virus-infected cells is important for an effective therapeutic vaccine and that special attention should be given to the suppression of latent infection.

Uncovering subdominant cytotoxic T-lymphocyte responses in lymphocytic choriomeningitis virus-infected BALB/c mice

The cytotoxic T-lymphocyte response against lymphocytic choriomeningitis virus (LCMV) in BALB/c mice is predominantly directed against a single, Ld-restricted epitope in the viral nucleoprotein (residues 118 to 126). To investigate whether any Kd/Dd-restricted responses were activated but did not expand during the primary response, we used a BALB/c mutant, BALB/c-H-2dm2, which does not express the Ld molecule. Splenocytes from LCMV-infected BALB/c mice were transferred into irradiated BALB/c-H-2dm2 mice and rechallenged with LCMV. Thus, they were exposed to an antigenic stimulus without the involvement of the immunodominant Ld-restricted epitope. In this adoptive transfer model, the donor splenocytes protected the recipient mice against chronic LCMV infection by mounting a potent Kd- and/or Dd-restricted secondary antiviral response. Analysis of a panel of Kd binding LCMV peptides revealed that residues 283 to 291 from the viral glycoprotein (GP(283-291)) comprise a major new epitope in the adoptive transfer model. Because the donor splenocytes were first activated during the primary infection in BALB/c mice, the GP(283-291) epitope is a subdominant epitope in BALB/c mice that becomes dominant after rechallenge in BALB/c-H-2dm2 mice. This study makes two points. First, it shows that subdominant CTL responses can be protective, and second, it provides a general experimental approach for uncovering subdominant CTL responses in vivo. This strategy can be used to identify subdominant T-cell responses in other systems.

Imaging of Moya Moya disease

Moya Moya disease is a rare disease causing occlusion of the supraclinoid portions of the internal carotid arteries. The CT, MRI and Angiography findings of four patients of Moya Moya disease are presented. CT revealed presence of infarction in the bilateral cerebral hemispheres and atrophy in all patients who had CT. CT was also able to detect abnormal vessels at basal ganglia in one patient. MRI was more informative and besides showing the infarctions and atrophy it also revealed abnormal Moya Moya vessels in all patients. Cerebral angiography is the most definitive method of diagnosis. It showed occlusion of supra clinoid portion of internal carotid arteries on both sides in three patients and on one side in one patient. It also showed pressure of Moya Moya vessels in all cases. It also showed collaterals from meningeal and ophthalmic arteries in all cases. Imaging findings of Moya Moya disease are very specific and provide early diagnosis.

Experimental measles. I. Pathogenesis in the normal and the immunized host

An animal model to study measles pathogenesis and the correlates of protective immunity was established using rhesus monkeys. A measles isolate, obtained during an epidemic of measles in the primate colony at the University of California, Davis, was passaged through rhesus monkeys and amplified in rhesus mononuclear cells to create a pathogenic virus stock. Sequence analysis of the nucleoprotein and hemagglutinin genes of this isolate revealed strong homology with the Chicago 89 strain of measles virus. Conjunctival/intranasal inoculation of juvenile rhesus monkeys with this virus resulted in skin rash, pneumonia, and systemic infection with dissemination to other mucosal sites and to the lymphoid tissues. Inflammation and necrosis occurred in the lungs and lymphoid tissues and many cell types were infected with measles virus on Day 7 postinoculation (p.i.). The most commonly infected cell type was the B lymphocyte in lymphoid follicles. Measles antigen was found in follicular dendritic cells on Day 14 p.i. In contrast to naive monkeys infected with measles virus, animals vaccinated with the attenuated Moraten strain did not develop clinical or pathologic signs of measles after challenge. However, moderate to marked hyperplasia occurred in the lymph nodes and spleen of a vaccinated animal on Day 7 after pathogenic virus challenge, suggesting that an effective measles vaccine limits but does not prevent infection with wild-type measles virus.

Direct somatic embryogenesis and plantlet regeneration from seedling leaves of winged bean,Psophocarpus tetragonolobus (L.) DC

Excised seedling leaf segments of winged bean [Psophocarpus tetragonolobus (L.) DC.] underwent direct somatic embryogenesis under appropriate incubation conditions. Initiation and development of the somatic embryos occurred using a two-step culture method. The culture procedure involved incubation for 28 days on MS basal medium supplemented with 0.1-0.5 mg/l NAA and 1.0-2.0 mg/l BA (induction medium) before transfer to MS medium supplemented with 0.1 mg/l IAA and 2.0 mg/l BA (embryo development medium). The initial exposure to low levels of NAA coincident with high levels of BA in the induction medium was essential for embryogenic induction. Maximum embryogenesis (43.3%) was obtained with 0.2 mg/l NAA and 2.0 mg/l BA, and at least 14 days on induction medium were required prior to transfer to the embryo development medium. The conversion frequency of cotyledonary embryos was 53.3% upon culture on MS medium containing 0.1 mg/l ABA for 7 days followed by transfer to MS medium supplemented with 0.1 mg/l IBA and 0.2 mg/l BA. Following conversion, the regenerated plantlets were transferred to soil and showed normal morphological characteristics.

Chronic invasive aspergillosis in apparently immunocompetent hosts

Seventeen cases of invasive aspergillosis occurring since 1987 in apparently immunologically normal hosts have been reviewed: 9 of invasive sinus aspergillosis, 2 of isolated brain abscesses, 3 of pneumonia (1 in a patient who developed mediastinitis), 2 of lymph node aspergillosis, and 1 of osteomyelitis of the foot. Two of the 9 patients with sinus aspergillosis died; the rest were stable up to March 1993. They responded initially to combined surgical and medical therapy. Both patients with brain abscesses survived following surgery, but one had neurological sequelae. Both patients with pneumonia were well following therapy with amphotericin B; one also received itraconazole. The patient with mediastinitis died, but this disease was diagnosed late. The patients with lymph node involvement were lost to follow-up, as was the patient with osteomyelitis. Invasive aspergillosis may be common in Pakistan. Greater awareness would allow earlier diagnosis and therapy, thereby improving the outcome.

Is carcinoma breast a different disease in Pakistani population?

Carcinoma of the breast tends to be different in coloured and white races. Is this pattern also expressed in Pakistani population? To answer this query we carried out a retrospectively study of breast cancer on 193 cases who were divided into 2 groups i.e. less than and more than 50 years age groups. In the former group, 93% tumours were of grades II or III and approximately 51% were estrogen receptors negative. In more than 50 years age group, 75% tumors were in grade II and III, with almost 37% being estrogen negative tumors. Majority (75%) of the patients had over 6 cms lump with equal number having positive lymph node status. All these factors point to the fact that besides presenting late, our population has additional unfavourable prognostic factors.

Analysis of cytotoxic T cell responses to dominant and subdominant epitopes during acute and chronic lymphocytic choriomeningitis virus infection

The cytotoxic T cell response against lymphocytic choriomeningitis virus (LCMV) in BALB/c (H-2d) mice is predominantly directed against a single immunodominant Ld-restricted epitope in the viral nucleoprotein (NP118-126). Here we report that the immunodominance of this peptide can be in part attributed to its very high affinity for Ld class I molecules. By employing motif searches and sensitive MHC class I binding assays, we also identified 5 Kd-binding peptides in the viral nucleoprotein and glycoprotein among 16 Kd motif-fitting peptides. The nucleoprotein and glycoprotein sequences also contained 18 Dd motif-fitting peptides, three of which bound Dd with weak affinity. Two of the Kd-binding peptides, residues 99-108 and residues 283-291 from the viral glycoprotein, are subdominant epitopes. Although these peptides did not sensitize target cells for direct ex vivo killing by primary antiviral CTL, secondary responses against these peptides were readily detected in BALB/c mice after acute LCMV infection. BALB/c mice that had cleared a long-term LCMV infection showed more sustained CTL responses against these subdominant epitopes, suggesting that subdominant responses might play a role in clearance of chronic infections. One of the subdominant epitopes, GP283-291, conferred partial protection against persistent viral infection after peptide vaccination.

Analysis of cytotoxic T cell responses to dominant and subdominant epitopes during acute and chronic lymphocytic choriomeningitis virus infection

The cytotoxic T cell response against lymphocytic choriomeningitis virus (LCMV) in BALB/c (H-2d) mice is predominantly directed against a single immunodominant Ld-restricted epitope in the viral nucleoprotein (NP118-126). Here we report that the immunodominance of this peptide can be in part attributed to its very high affinity for Ld class I molecules. By employing motif searches and sensitive MHC class I binding assays, we also identified 5 Kd-binding peptides in the viral nucleoprotein and glycoprotein among 16 Kd motif-fitting peptides. The nucleoprotein and glycoprotein sequences also contained 18 Dd motif-fitting peptides, three of which bound Dd with weak affinity. Two of the Kd-binding peptides, residues 99-108 and residues 283-291 from the viral glycoprotein, are subdominant epitopes. Although these peptides did not sensitize target cells for direct ex vivo killing by primary antiviral CTL, secondary responses against these peptides were readily detected in BALB/c mice after acute LCMV infection. BALB/c mice that had cleared a long-term LCMV infection showed more sustained CTL responses against these subdominant epitopes, suggesting that subdominant responses might play a role in clearance of chronic infections. One of the subdominant epitopes, GP283-291, conferred partial protection against persistent viral infection after peptide vaccination.

CD40 ligand-deficient mice generate a normal primary cytotoxic T-lymphocyte response but a defective humoral response to a viral infection

CD40 ligand is expressed on activated T cells and interacts with CD40 on B cells and monocytes. It is not known what role CD40 ligand plays in the generation of immune responses to viral infection. To address this issue, we examined virus-specific T- and B-cell responses in CD40 ligand-deficient (CD40L-/-) mice following infection with lymphocytic choriomeningitis virus (LCMV). We found that primary anti-LCMV specific antibody responses were severely impaired in CD40L-/- mice, with the defect being most striking for antibody of the immunoglobulin G1 (IgG1) isotype. Interestingly, low levels of LCMV-specific antibodies of the IgG2a, IgG2b, and IgG3 isotypes were made in the CD40L-/- mice, showing that IgG1 responses are totally dependent on CD40L but that at least some IgG2a, IgG2b, and IgG3 responses can be CD40L independent. However, unlike CD40L+/+ mice, CD40L-/- mice were unable to sustain virus-specific antibody responses and showed a gradual decline in serum antibody levels over time. The CD40L-/- mice were also deficient in the generation of memory B cells. In contrast to the severely impaired humoral responses, CD40L-/- mice generated potent virus-specific CD8+ cytotoxic T-lymphocyte responses after LCMV infection and were able to clear the virus. These results show that CD40L does not play a role in generating primary virus-specific CD8+ cytotoxic T-lymphocyte responses but does affect the primary antibody response and the generation of memory B cells.

Limiting dilution analysis of virus-specific memory B cells by an ELISPOT assay

Many acute viral infections induce long-term, sometimes even life-long humoral immunity. To characterize this immune response, accurate quantitation of memory B cells and plasma cells is essential. Plasma cells can be quantitated directly ex vivo by virtue of their ability to spontaneously secrete antibody. Memory B cells on the other hand, do not spontaneously secrete antibody but require antigenic stimulation in order to proliferate and differentiate into antibody secreting cells (ASC). In this study, an ELISPOT-based limiting dilution assay (LDA) was developed for quantitating virus-specific B cell memory following acute lymphocytic choriomeningitis virus (LCMV) infection of adult mice. Antiviral memory B cell precursor (MBCp) frequencies were calculated from in vitro stimulated cultures using either a conventional ELISA-based LDA to measure accumulated virus-specific antibody in the culture medium or a new ELISPOT-based LDA that identifies the antibody-secreting daughter cells directly. In terms of sensitivity, the ELISPOT-based LDA and the ELISA-based LDA both calculated LCMV-specific MBCp frequencies to be approximately 1/2 x 10(4) spleen cells. However, compared to the 12 days of in vitro stimulation required to estimate MBCp frequencies by the ELISA-based LDA, the ELISPOT-based LDA required only 3-6 days of stimulation to quantitate MBCp frequencies. If cell division was blocked by gamma-irradiation or treatment with mitomycin C, the MBCp frequency dropped below detection (< 1 MBCp/10(6) cells), indicating that virus-specific B cells quantitated by this assay must both proliferate and differentiate into antibody secreting cells in order to be detected. Naive, uninfected mice did not have LCMV-specific memory B cells, demonstrating that only in vivo-generated antiviral B cells from LCMV-immune mice were detected by this assay. chi 2 analysis of the ELISPOT-based LDA showed that the MBCp frequency data fit a linear regression model (p = 0.0137), indicating single-hit kinetics in which only one cell type was limiting. These results indicate that the ELISPOT-based LDA provides a rapid and statistically accurate method to quantitate virus-specific B cells.

Long-term antibody production is sustained by antibody-secreting cells in the bone marrow following acute viral infection

Acute viral infection of humans induces virus-specific serum antibody production that often persists for decades. To better understand the nature of this long-term antiviral antibody response, we studied antiviral antibody production of mice acutely infected with lymphocytic choriomeningitis virus (LCMV). Although this viral infection is resolved within 2 weeks, virus-specific serum antibody levels were maintained for > 300 days postinfection. The anatomic site of long-term antibody production was identified using an ELISPOT assay to quantitate LCMV-specific antibody-secreting cells (ASC). The initial antiviral ASC response in the spleen peaked at 8 days postinfection and then declined sharply, with less than 10% of the day 8 ASC population remaining after 60 days. Although no LCMV specific ASC were detected in the bone marrow at day 8, virus-specific ASC began accumulating in the bone marrow by 15 days postinfection. By day 60, approximately 10-fold more antiviral ASC were present in the bone marrow than in the spleen, and the bone marrow remained the major site of antibody production for > 10 months postinfection. To further characterize the LCMV-specific antibody response, the relative percentage of each IgG subclass (IgG1, IgG2a, IgG2b, and IgG3) was determined. IgG2a was the predominant IgG subclass produced during LCMV infection, and the IgG subclass profile of virus-specific ASC in the spleen and bone marrow matched the IgG subclass profile of virus-specific IgG in the serum. Following a secondary infection with LCMV, splenic ASC numbers increased rapidly with a peak at 5 days after secondary infection. This was followed by a sharp decline in ASC numbers by day 15. In contrast, virus-specific ASC numbers in bone marrow remained essentially unchanged during the acute phase of the secondary infection but increased approximately twofold at day 15, corresponding to a twofold increase in virus-specific serum antibody levels. These results indicate that following a primary viral infection or upon reexposure to a virus, the initial antibody response occurs in the spleen, but long-term antiviral antibody production is maintained in the bone marrow.

A common major histocompatibility complex class II allele HLA-DQB1* 0301 is present in clinical variants of pemphigoid

Bullous pemphigoid (BP) is an autoimmune subepidermal blistering disease seen primarily in elderly persons. It is characterized clinically by the development of tense bullae and by the presence of an antibasement membrane antibody. In BP, the antigens involved in the autoimmunity are epidermal basement membrane peptides BPAg1 and BPAg2. We have compared high resolution typing of major histocompatibility complex class II loci (HLA-DRB1, DQB1) in 21 patients with BP, 17 with ocular cicatricial pemphigoid (OCP), and 22 with oral pemphigoid (OP) to a panel of 218 haplotypes of normal individuals. We found that the three diseases (BP, OCP, and OP) have significant association with DQB1*0301 (P = 0.005, P < 0.0001, and P = 0.001, respectively). The frequencies of alleles DQB1*0302, 0303, and 06, which share a specific amino acid sequence from position 71 to 77 (Thr-Arg-Ala-Glu-Leu-Val-Thr) were also increased (P = 0.01). We suggest that an identical major histocompatibility complex class II allele (DQB1*0301) is a common marker for enhanced susceptibility and that the same amino acid residues in positions 71-77 (DQB1*0301, -0302, -0305, -0602, -0603 alleles) are found in patients with BP, OCP and OP. Our findings propose that the autoimmune response in the three different clinical variants of pemphigoid, involves the recognition by T cells of a class II region of DQB1, bound to a peptide from the basement membrane of conjunctiva, oral mucosa, and skin.

Antiviral cytotoxic T-cell memory by vaccination with recombinant Listeria monocytogenes

Listeria monocytogenes is a facultative intracellular bacterium that is able to escape phagocytic vesicles and replicate in the cytoplasm of infected cells. As with viral vectors, this intracytoplasmic life cycle provides a means for introducing foreign proteins into the major histocompatibility complex class I pathway of antigen presentation. Using recombinant L. monocytogenes (rLM) strains expressing the full-length nucleoprotein (NP) or a single cytotoxic T-lymphocyte (CTL) epitope from lymphocytic choriomeningitis virus (LCMV), we analyzed antiviral CTL responses induced by rLM vaccination. After vaccination, rLM was cleared from the host within 7 days while inducing an LCMV-specific ex vivo CD8+ effector CTL response. Virus-specific CTL memory was maintained for 6 months postvaccination, as demonstrated by vigorous secondary CTL responses after in vitro stimulation. A single immunization with rLM that expressed either the full-length NP gene or the CTL epitope alone resulted in LCMV NP-specific CTL precursor frequencies of approximately 1/10(4) CD8+ T cells. A second rLM vaccination resulted in enhanced virus-specific CTL activity and in vitro proliferation. rLM-vaccinated mice were protected against chronic viral infection by an accelerated virus-specific memory CTL response. These mice cleared infectious virus as well as viral antigen, suggesting that sterilizing immunity was achieved. In contrast to mice that received wild-type LM, rLM-vaccinated mice were protected from virally induced immunosuppression and splenic atrophy associated with chronic LCMV infection. The ability to elicit long-term cell-mediated immunity is fundamental in designing vaccines against intracellular pathogens, and these results demonstrate the efficacy of recombinant LM vaccination for inducing protective antiviral CTL memory.

CD8 T cell memory in B cell-deficient mice

Antigen presentation by B cells and persistence of antigen-antibody complexes on follicular dendritic cells (FDC) have been implicated in sustaining T cell memory. In this study we have examined the role of B cells and antibody in the generation and maintenance of CD8+ cytotoxic T lymphocyte (CTL) memory. To address this issue we compared CTL responses to lymphocytic choriomeningitis virus (LCMV) in normal (+/+) versus B cell-deficient mice. The CTL response to acute LCMV infection can be broken down into three distinct phases: (a) the initial phase (days 3-8 after infection) of antigen-driven expansion of virus-specific CD8+ T cells and the development of effector CTL (i.e., direct ex vivo killers); (b) a phase of death (between days 10 and 30 after infection) during which >95% of the virus-specific CTL die and the direct effector activity subsides; and (c) the phase of long-term memory (after day 30) that is characterized by a stable pool of memory CTL that persist for the life span of the animal. The role of B cells in each of these three phases of the CTL response was analyzed. We found that B cells were not required for the expansion and activation of virus-specific CTL. The kinetics and magnitude of the effector CTL response, as measured by direct killing of infected targets by ex vivo isolated splenocytes, was identical in B cell-deficient and +/+ mice. Also, the expansion of CD8+ T cells was not affected by the absence of B cells and/or antibody; in both groups of mice there was an approximately 10,000-fold increase in the number of LCMV-specific CTL and a greater than 10-fold increase in the total number of activated (CD44hi) CD8+ T cells during the first week after virus infection. Although no differences were seen during the "expansion" phase, we found that the "death" phase was more pronounced in B cell-deficient mice. However, this increased cell death was not selective for LCMV-specific CTL, and during this period the total number of CD8+ T cells also dropped substantially more in B cell-deficient mice. As a result of this, the absolute numbers of LCMV-specific CTL were lower in B cell-deficient mice but the frequencies were comparable in both groups of mice. More significantly, the memory phase of the CTL response was not affected by the absence of B cells and a stable number of LCMV-specific CTL persisted in B cell-deficient mice for up to 6 mo. Upon reinfection, B cell-deficient mice that had resolved an acute LCMV infection were able to make accelerated CTL responses in vivo and eliminated virus more efficiently than naive B cell-deficient mice. Thus, CTL memory, as assessed by frequency of virus-specific CTL or protective immunity, does not decline in the absence of B cells. Taken together, these results show that neither B cells nor antigen-antibody complexes are essential for the maintenance of CD8+ CTL memory.

Immunological memory and protective immunity: understanding their relation

The immune system can remember, sometimes for a lifetime, the identity of a pathogen. Understanding how this is accomplished has fascinated immunologists and microbiologists for many years, but there is still considerable debate regarding the mechanisms by which long-term immunity is maintained. Some of the controversy stems from a failure to distinguish between effector and memory cells and to define their roles in conferring protection against disease. Here the current understanding of the cellular basis of immune memory is reviewed and the relative contributions made to protective immunity by memory and effector T and B cells are examined.

Orthotopic liver transplantation at king faisal specialist hospital and research center: 1994-1995

Over the last decade, orthotopic liver transplantation (OLT) has become an established therapy for end-stage liver disease of various etiologies. The early experience with orthotopic liver transplantation in the Kingdom was in 1990 in the Military Hospital when a man with sclerosing cholangitis received a new liver successfully. Intensive effort was done at King Faisal Specialist Hospital and Research Center (KFSH & RC) to start liver transplantation and that was achieved in March 1994 when a man with an end-stage liver failure secondary to hepatitis C was transplanted successfully. Since then, forty four (44) more liver transplantations were done at KFSH & RC. The age of the patients transplanted ranged from 9-65 years old; there were more males than females, (26 males, 15 females). The waiting time until transplantation was up to one year. All patients received a combination of cyclosporin and prednisolone as an induction therapy +/- Azathioprime. The majority of patients developed minor complications like wound infection and acute mild cellular rejection. In the second year, 3 out of 18 patients also developed primary non-function. Also in the first year, the majority of the patients developed primary dysfunction; however, this decreased significantly in the second year. The majority of the patients who were transplanted for hepatitis C had mild recurrence. None of them lost their livers because of recurrence of hepatitis C. Several patients developed biliary complications including bile leak and stricture at duct-to-duct anastomosis.

Somatic embryogenesis and plant regeneration from leaf derived callus of winged bean [Psophocarpus tetragonolobus (L.) DC]

Somatic embryos were obtained from callus cultures derived from leaf explants of the winged bean, Psophocarpus tetragonolobus (L.) DC. Initiation and development of the somatic embryos occurred with a two-step culture method. Callus cultures initiated on MS medium with NAA and BAP, upon transfer to a new medium with IAA and BAP, produced somatic embryos. Maximum embryogenesis of 60% was obtained on induction medium with 0.5 mg/l NAA plus 1.0 mg/l BAP followed by transfer to a secondary medium with 0.1 mg/l IAA and 2.0 mg/l BAP. Optimal embryo germination and plantlet development was achieved on MS medium with 0.2 mg/l BAP plus 0.1 mg/l IBA. The regenerated plants were successfully transferred to glasshouse conditions.

Intestinal intraepithelial lymphocytes respond to systemic lymphocytic choriomeningitis virus infection

Intestinal intraepithelial lymphocytes (IEL) are a population of cells consisting mostly of CD8+ T lymphocytes. Although their function is unknown, because of their location within the epithelium it has been postulated that IEL may be involved in defense against infection of the gut mucosa by pathogens including viruses. To address this issue, we have examined IEL populations from BALB/c mice systemically infected with lymphocytic choriomeningitis virus (LCMV). Viral infection induced a virus-specific cytotoxic response by IEL at 8 days postinfection. This virus-specific cytotoxic T lymphocyte (CTL) response was MHC class I restricted, and as is true for splenic T cells, recognition of viral antigen occurred predominantly in the context of the Ld molecule. The effector cells could be depleted by treatment with anti-CD8 antibody plus complement. In vivo treatment of mice with anti-alpha beta T cell receptor (TCR) antibody during the course of viral infection abrogated the response, suggesting that the virus-specific CTL were cells that express the alpha beta rather than gamma delta TCR. Consistent with this, no virus-specific IEL response could be detected in athymic mice, which have TCR gamma delta+ but not TCR alpha beta+ IEL. LCMV antigen could not be detected in the epithelium of the intestine, suggesting that viral antigen may have been encountered elsewhere. These data demonstrate for the first time a specific response by IEL to virus given by a non-oral route, and they suggest that thymus-derived alpha beta T cells can migrate to the intestinal epithelium following activation, where they may play a role in the response to virus and perhaps other infections.

Phaeochromocytoma

Phaeochromocytomas are rare catecholamine-secreting tumours which can mimic a variety of common clinical conditions, such as hypertension and angina. It is a potentially curable condition if discovered early, and clinicians should be alerted as to its presence in a young individual with hypertension or atypical angina-associated hypertension. Pharmacological mismanagement can cause fatal hypertensive crisis.

Bacillus cereus and Bacillus thuringiensis isolated in a gastroenteritis outbreak investigation

During investigation of a gastroenteritis outbreak in a chronic care institution, Norwalk virus was found in stool specimens from two individuals and bacterial isolates presumptively identified as Bacillus cereus were isolated from four individuals (including one with Norwalk virus) and spice. Phage typing confirmed all Bacillus clinical isolates were phage type 2. All clinical isolates were subsequently identified as B. thuringiensis when tested as a result of a related study (L. Leroux, personal communication). Eight of 10 spice isolates were phage type 4. All B. cereus and B. thuringiensis isolates showed cytotoxic effects characteristic of enterotoxin-producing B. cereus. An additional 20 isolates each of B. cereus and B. thuringiensis from other sources were tested for cytotoxicity. With the exception of one B. cereus, all showed characteristic cytotoxic patterns.