STAT3-stathmin interactions control microtubule dynamics in migrating T-cells

T-cell migration is a complex highly coordinated process that involves cell adhesion to the high endothelial venules or to the extracellular matrix by surface receptor/ligand interactions, cytoskeletal rearrangements, and phosphorylation-dependent signaling cascades. The mechanism(s) that regulates T-cell migration is of considerable relevance for understanding the pathogenesis of various diseases, such as chronic inflammatory diseases and cancer metastasis. This study was designed to identify potential involvement of STAT3, a latent transcription factor, in mediating integrin-induced T-cell migration. Using our previously characterized in vitro model for lymphocyte migration, we demonstrate that STAT3 is activated and translocated to the nucleus during the process of active motility of Hut78 T-lymphoma cells triggered via LFA-1. Blocking STAT3 signaling by multiple approaches inhibited LFA-1-induced T-cell locomotion via destabilization of microtubules and post-translational modification of tubulin. Here, we show that STAT3 physically interacts with stathmin to regulate microtubule dynamics in migrating T-cells. These observations strongly indicate that STAT3 is critically important for T-cell migration and associated signaling events.

Characterization of genetic polymorphism of the bovine lymphocyte antigen DRB3.2 locus in Kankrej cattle (Bos indicus)

Bovine lymphocyte antigen DRB 3.2 (BoLA-DRB3.2) gene encodes for the beta chain of the major histocompatibility complex (MHC) class II molecule in cattle, which is a glycoprotein present on the surface of antigen-presenting cells. This locus shows extensive polymorphism in it. The objective of the present study was to genotype the BoLA-DRB3.2 locus in Kankrej cattle (n = 50) by PCR-RFLP. Bovine DNA was isolated from aliquots of whole blood. Primers specific for exon 2 of the bovine lymphocyte antigen (BoLA)-DRB3 gene were used to amplify the region. The 304-bp amplified product of the DRB3 gene was separately digested with restriction endonucleases RsaI, BstYI, and Hae III. Twenty-four BoLA-DRB 3.2 alleles were identified with frequencies ranging from 1 to 22.0%. Twenty-one alleles of the total 24 alleles were similar to those reported earlier; 3 alleles were new and had not been reported previously. The allele BoLA-DRB3.2*34 occurred at the highest frequency of 22% (approx.) in the Kankrej animals studied. Six alleles (BoLA-DRB3.2 *34, *15, *06, *20, *37, and *20) accounted for almost 71% of the total alleles observed to be present in the Kankrej animals. All the new alleles observed were present at frequencies of 1%. The results obtained in the present study demonstrated that the BoLA DRB3.2 locus is highly polymorphic in the Kankrej cattle.

Miltefosine induces apoptosis in arsenite-resistant Leishmania donovani promastigotes through mitochondrial dysfunction

The control of leishmaniasis in absence of vaccine solely depends on the choice of chemotherapy. The major hurdle in successful leishmanial chemotherapy is emergence of drug resistance. Miltefosine, the first orally administrable anti-leishmanial drug, has shown the potential against drug-resistant strains of Leishmania. However, there are discrepancies regarding the involvement of P-glycoprotein (Pgp) and sensitivity of miltefosine in multiple drug-resistant (MDR) cell lines that overexpress Pgp in Leishmania. To address this, the effect of miltefosine in arsenite-resistant Leishmania donovani (Ld-As20) promastigotes displaying an MDR phenotype and overexpressing Pgp-like protein was investigated in the current study. Results indicate that Ld-As20 is sensitive to miltefosine. Miltefosine induces process of programmed cell death in Ld-As20 in a time-dependent manner as determined by cell shrinkage, externalization of phosphatidylserine and DNA fragmentation. Miltefosine treatment leads to loss of mitochondrial membrane potential and the release of cytochrome C with consequent activation of cellular proteases. Activation of cellular proteases resulted in activation of DNase that damaged kinetoplast DNA and induced dyskinetoplasty. These data indicate that miltefosine causes apoptosis-like death in arsenite-resistant L. donovani.

The anti-leishmanial drug miltefosine causes insulin resistance in skeletal muscle cells in vitro

AIMS/HYPOTHESIS

Miltefosine, the first oral anti-leishmanial drug, is reported to inhibit phosphatidylinositol 3-kinase (PI3K)/Akt activity in carcinoma cell lines. Inhibition of the PI3K/Akt pathway is known to result in insulin resistance. Therefore, we investigated whether miltefosine has any deleterious effect(s) on insulin sensitivity in L6E9 skeletal muscle cells.

MATERIALS AND METHODS

L6E9 myotubes were treated with miltefosine and its effect was observed on insulin-signalling proteins such as Akt, PI3K, insulin receptor-beta, IRS-1, c-Jun N-terminal kinase, p38 and glycogen synthase kinase beta, as well as on glucose uptake.

RESULTS

Miltefosine caused skeletal muscle insulin resistance in vitro by interfering with the insulin-signalling pathway and inhibiting insulin-stimulated glucose uptake.

CONCLUSIONS/INTERPRETATION

Miltefosine may contribute to the risk of type 2 diabetes and needs further clinical exploration.

Phytomitogen induced changes in levels of inositol phosphates in the bovine lymphocytes

The changes in levels of inositol phosphates and phosphoinositides were studied in the bovine lymphocytes, in response to phytomitogens (lectins)-concanavalin A (con A) and phytohaemagglutinin (PHA). Addition of con A and PHA resulted in a rapid increase in the cpm of total inositol phosphates (from 8599 +/- 100 cpm/2 x 10(6) cells to 11228 +/- 126 cpm/2 x 10(6) and 9758 +/- 100 cpm/2 x10(6) cells, respectively) at 1 min after mitogen stimulation. There was a concomitant decrease in the phosphatidylinositol levels at 1 min, which continued up to 5 min. At 1 min of stimulation, inositol diphosphate fraction exhibited maximum increase, as compared to inositol mono- and triphosphates, suggesting that it contributed the most towards the overall increase in the total inositol phosphates levels. Results suggest that bovine lymphocytes respond to phytomitogens with a rapid turnover of phosphoinositides.

PPAR-gamma expression modulates insulin sensitivity in C2C12 skeletal muscle cells

Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) expression is very low in skeletal muscle cells, which is one of the most important target tissues for insulin and plays a predominant role in glucose homeostasis. It has recently been shown that muscle-specific PPAR-gamma deletion in mouse causes insulin resistance. However, it is likely that the observed effects might be due to secondary interaction in whole animal. The aim of the study was to explore the role of muscle PPAR-gamma in insulin sensitivity. We stably transfected C2C12 skeletal muscle cells with plasmids containing sense or antisense constructs of PPAR-gamma and examined the effect of modulation of PPAR-gamma expression in terms of glucose uptake. Effect was also examined in insulin-resistant C2C12 skeletal muscle cells. In transfected C2C12 cell line, the inhibition of PPAR-gamma expression (23.0 +/-0.005%) was observed to induce insulin resistance as determined by functional assessment of 2-deoxyglucose incorporation. Overexpression of PPAR-gamma (28.5 +/- 0.008%) produced an additional effect on insulin (100 nM) and Pioglitazone (50 microM), resulting in 42.7 +/- 3.5% increase in glucose uptake as against 29.2+/-2.8% in wild-type C2C12 skeletal muscle cells differentiated under normal (2% horse serum) condition. Under similar treatment, PPAR-gamma overexpressing cells resistant to insulin exhibited enhanced glucose uptake upto 60.7 +/- 4.08%, as compared to 23.8 +/- 5.1% observed in wild-type C2C12 skeletal muscle cells. These data demonstrate a direct involvement of PPAR-gamma in insulin sensitization of TZD action on skeletal muscle cells, and suggest that pharmacological overexpression of muscle PPAR-gamma gene in skeletal muscle might be a useful strategy for the treatment of insulin resistance.

RNA-mediated gene silencing: mechanisms and its therapeutic applications

RNA interference, part of a complicated network of interconnected pathways for cellular defence, RNA surveillance and development, has become a powerful tool for the experimental manipulation of gene expression. It is the process by which double-stranded (dsRNA) silences specific gene expression through homology-dependent degradation of cognate mRNA. The dsRNA is converted into 21nt small interfering RNAs (siRNAs), which directs a complex ribonuclease system to substrate mRNA targets. The degradation of the target mRNA is initiated with the cleavage at a position corresponding to the centre of the siRNA. Dissecting individual cellular pathways to reveal the function of numerous proteins is an approach to drug discovery. Interfering RNA (RNAi) serves as a rapid and convenient tool, which works in various organisms. RNAi technology has the potential to facilitate our understanding of biological processes and potentially lead to exciting new drugs. Here we review various experimental approaches adopted with RNAi and possible therapeutic applications.

Possible mechanism of miltefosine-mediated death of Leishmania donovani

Miltefosine causes leishmanial death, but the possible mechanism(s) of action is not known. The mode of action of miltefosine was investigated in vitro in Leishmania donovani promastigotes as well as in extra- and intracellular amastigotes. Here, we demonstrate that miltefosine induces apoptosis-like death in L. donovani based on observed phenomena such as nuclear DNA condensation, DNA fragmentation with accompanying ladder formation, and in situ labeling of DNA fragments by the terminal deoxyribonucleotidyltransferase-mediated dUTP-biotin nick end labeling method. Understanding of miltefosine-mediated death will facilitate the design of new therapeutic strategies against Leishmania parasites.

A study of drug utilisation and cost of treatment in patients hospitalised with unstable angina

OBJECTIVE

The current study was designed to investigate drug utilisation in the management of unstable angina in India and to calculate the costs incurred by patients in the treatment of a single episode of unstable angina.

METHODS

We conducted a prescription survey to examine the use of antianginal drugs in patients with unstable angina in a tertiary care Indian hospital. The use of concurrent medications such as antidiabetic, antihypertensive and lipid-lowering agents was also examined. Data on the cost of treatment, investigations, income, and family size were collected from the case histories or direct interviews with the patients/relatives.

RESULTS

A total of 336 consecutive prescriptions were evaluated. Aspirin was the most frequently prescribed drug (98%) followed by nitroglycerin infusion (90%) and enoxaparin (52%). One of the heparins was used by 89% of all patients and beta-blockers by up to 62% of the patients. Besides antianginals, antihypertensive (49%) and antidiabetic (16%) drugs were commonly coadministered. The mean (+/- SD) cost of treatment of a single episode of unstable angina in the hospital was US $494 (+/- 271) against an annual per capita income of US $245. The mean (+/- SD) cost incurred by the patients due to drugs alone during the hospital stay was US $70 (+/- 18) and enoxaparin accounted for 60% of the expenditure due to drugs.

CONCLUSIONS

The results of our study show that low-molecular-weight heparin, enoxaparin, is replacing unfractionated heparin in the treatment of unstable angina. In view of the use of costly new drugs, there is an urgent need for carrying out pharmacoeconomic analysis in developing countries as the treatment of a single episode of unstable angina imparts a considerable economic burden on the patient.

Antigen-specific systemic and reproductive tract antibodies in foxes immunized with Salmonella typhimurium expressing bacterial and sperm proteins

Attenuated Salmonella typhimurium strains are potential 'safe' delivery vectors of an oral immunocontraceptive vaccine for the European red fox (Vulpes vulpes). In the present study, model bacterial (Escherichia coli heat-labile enterotoxin B subunit, LTB) and fox sperm (fSP10) antigens were expressed in S. typhimurium SL3261 (delta aroA) under the control of the trc promoter. Adult female foxes were given three oral immunizations with SL3261 containing either LTB (SL3261/pLTB), fSP10 (SL3261/pFSP10) or a control plasmid (pKK233-2 or pTrc99A). All foxes raised serum (IgG) and vaginal (IgG and IgA) antibodies against S. typhimurium lipopolysaccharide (LPS). Each fox that received SL3261/pLTB raised high titre LTB-specific serum and vaginal IgG antibodies. However, only one of four foxes immunized with SL3261/pFSP10 raised an anti-fSP10 immune response, in the form of low titre serum and vaginal IgG antibodies. No vaginal IgA antibodies were raised against either LTB or fSP10 in these experiments. The immune responses against recombinant LTB and fSP10 resulted chiefly from the initial dose of antigen in the inocula and were minimally influenced by continued in vivo antigen expression. This study demonstrates for the first time in the female red fox that oral Salmonella can elicit specific systemic and reproductive tract antibodies against heterologous, recombinant proteins.

Serotype-converting bacteriophages and O-antigen modification in Shigella flexneri

O-antigen modification (serotype conversion) in Shigella flexneri, which is an important virulence determinant, is conferred by temperate bacteriophages. Several serotype-converting phages have been isolated and preliminary characterization has identified the genes involved in O-antigen modification, and has also provided insight into the molecular biology of these phages.

Immune response to rotavirus VP4 expressed in an attenuated strain of Shigella flexneri

An attenuated strain of Shigella flexneri was utilised to express viral protein (VP) 4 of rotavirus and the immunogenicity of the recombinant constructs was studied in BALB/c mice. VP4 was expressed as a fusion with maltose binding protein (MBP) in both the cytoplasm and periplasm, with a much higher level of expression occurring in the former. While all constructs induced a Shigella-specific response in mice, only the construct expressing MBP-VP4 in the cytoplasm of Shigella stimulated an immune response specific to rotavirus. This study demonstrates that Shigella can be used to deliver rotavirus antigens and induces an immune response directed towards both rotavirus and Shigella.

Serotype 1a O-antigen modification: molecular characterization of the genes involved and their novel organization in the Shigella flexneri chromosome

The factors responsible for serotype 1a O-antigen modification in Shigella flexneri were localized to a 5.8-kb chromosomal HindIII fragment of serotype 1a strain Y53. The entire 5.8-kb fragment and regions up- and downstream of it (10.6-kb total) were sequenced. A putative three-gene operon, which showed homology with other serotype conversion genes, was identified and shown to confer serotype 1a O-antigen modification. The serotype conversion genes were flanked on either side by phage DNA. Multiple insertion sequence (IS) elements were located within and upstream of the phage DNA in a composite transposon-like structure. Host DNA homologous to the dsdC and the thrW proA genes was located upstream of the IS elements and downstream of the phage DNA, respectively. The sequence analysis indicates that the organization of the 10.6-kb region of the Y53 chromosome is unique and suggests that the serotype conversion genes were originally brought into the host by a bacteriophage. Several features of this region are also characteristic of pathogenicity islands.

Serotype conversion of a Shigella flexneri candidate vaccine strain via a novel site-specific chromosome-integration system

Shigella flexneri SFL124 (serotype Y) is a promising live oral vaccine candidate, which has been shown to be safe and immunogenic in human volunteers. To change the serotype of this vaccine strain, we inserted a serotype conversion gene cluster into the chromosome of SFL124 by using a bacteriophage-based site-specific integration system. By cloning an integrase gene (int), an attachment site (attP) and a glucosyl transfer gene cluster from bacteriophage SfX into a suicide vector, and subsequently introducing this construct into S. flexneri SFL124, we obtained a S. flexneri strain (designated SFL1213) expressing the serotype X somatic antigen specificity. The strain retained other characteristics of the parent strain, such as colony shape, growth rate, and Congo red binding property. Stability test showed that the serotype X O-antigen specificity in SFL1213 was 100% stable after being cultured approximately 72 successive hours under non-selective condition. In a mouse pulmonary model, the recombinant strain elicited a significant level of humoral antibodies which recognized the lipopolysaccharide (LPS) of a wild-type S. flexneri serotype X strain. The site-specific insertion system will be useful when stable expression of a cloned single copy gene is desired in the chromosome of S. flexneri vaccine candidate, SFL124.

Cloning and characterisation of the aroA and aroD genes of Shigella dysenteriae type 1

The aroA and aroD genes from Shigella dysenteriae type 1, encoding 5-enolpyruvylshikimate 3-phosphate synthase and 3-dehydroquinase, respectively, were cloned by polymerase chain reaction (PCR). Their nucleotide sequences were determined and predicted to code for 46 kDa and 27.5 kDa proteins, respectively. Protein expressed from these genes using the minicell system, corresponded to the size of the predicted protein products. The cloned genes were shown to be functional by complementation of Escherichia coli aroA- and aroD- mutants. The predicted amino acid sequences of the cloned aroA (427 amino acids) and aroD (252 amino acids) genes of S. dysenteriae type 1 were found to be highly homologous to the corresponding genes in other bacterial species, indicating the high conservation of these housekeeping genes. The use of the cloned aroA and aroD genes in the development of a vaccine strain against S. dysenteriae is discussed.

Enhancement of the specific mucosal IgA response in vivo by interleukin-5 expressed by an attenuated strain of Salmonella serotype Dublin

It has been shown that cytokines have potential as therapeutic adjuvants in vaccination. Interleukin-5 (IL-5) is a cytokine that regulates antibody production, in particular enhancing IgA production by activated mucosal B cells. This study examined the expression of a cloned cytokine gene encoding murine IL-5 (mIL-5) by an attenuated aroA strain (SL5631) of Salmonella serotype Dublin. The resulting strain, SL5631(pTRXFUS-mIL-5), expressed mIL-5 as a fusion with thioredoxin as demonstrated by immunological and biological assays. When strain SL5631(pTRXFUS-mIL-5) was used as a live vaccine in BALB/c mice, it colonised and multiplied at higher levels in spleens and livers than the strain carrying the empty plasmid. A reduction in invasiveness of SL5631(pTRXFUS-mIL-5) was observed in in-vitro invasion assays. Enhanced IgA response against salmonella LPS in mucosal secretions and enhanced IgA and IgG responses were detected by ELISA and ELISPOT methods in sera of mice immunised with the strain expressing mIL-5. Results with IL-5-deficient mice showed that the enhanced IgA response was due to Salmonella-expressed mIL-5 rather than endogenous mIL-5.

Cloning and analysis of the glucosyl transferase gene encoding type I antigen in Shigella flexneri

The O-antigen of most Shigella flexneri serotypes contains an identical tetrasaccharide repeating unit. Apart from serotype Y, the O-antigen is modified by addition of a glucosyl and/or O-acetyl residue to a specific position in the O-unit. In this study the glucosyl transferase gene from a serotype 1 a has been cloned and identified. The bacteriophage SfV integrase (int) gene was used to probe a S. flexneri Y53 (serotype 1 a) cosmid library and 18 unique clones were identified. Southern hybridisation of these clones indicated two unlinked regions of the chromosome contained the int homologue. When expressed in a live candidate vaccine strain of S. flexneri serotype Y (SFL124), clones with one region produced type I antigen, whereas clones containing the other region produced mainly type Y antigen. One of the cosmid clones positive for type I antigen by agglutination and Western blotting was selected for further study. Genes involved in O-antigen glucosyl modification were mapped on a 5.8 kb fragment and subclones were produced which fully or partially expressed the type I antigen, depending on the extent of the clone. Fully and partially expressing clones may be useful vaccine candidate strains for protection against disease caused by two serotypes of S. flexneri.

The immune response to a B-cell epitope delivered by Salmonella is enhanced by prior immunological experience

Attenuated, heterologous strains of Salmonella have shown potential as live, recombinant vaccines against foreign pathogens. Studies in animal models have demonstrated that immunization with these heterologous vaccines is an effective way to induce both cellular and humoral immune responses against Salmonella and the foreign antigen. We studied the consequence of priming mice with Salmonella dublin 3-6 months before intraperitoneal administration with the same strain carrying a model B-cell epitope. Mice primed with the carrier strain demonstrated enhanced serum Ig titres against the foreign antigen. This immune enhancement was observed up to approximately 6 months after priming. These findings suggest that previous immunological experience with Salmonella does not limit the immune response to a foreign antigen carried by the same organism. In fact, prior exposure to Salmonella appears to enhance the response to the foreign antigen.

Environmental auditing programme in India

The concept of environmental auditing in industrial units in India was formally introduced in March 1992 with the overall objective minimising consumption of resources and promoting use of clean technologies in industrial production to minimise generation of wastes. A series of discussions were held among the concerned regulatory agencies before and after making environmental auditing and submission of Annual Environmental Statements, a mandatory requirement for the industries. This followed organisation of a number of workshops, seminars and training programmers all over the country by different agencies dealing with environment protection, conducting of audit studies in 125 selected polluting industries in the country by the Central Pollution Control Board (CPCB), Delhi, and a number of other activities. The present paper gives the details of the activities before and after the introduction of this requirement in the country. The aspects covered include (i) the evolution of the concept, (ii) the history of the introduction of the scheme in the country and the organisational structure, (iii) the mandatory requirement and its applicability, (iv) the implementing agencies and their responsibilities, (v) summary of the training programmes/workshops organised in the country, (vi) case studies conducted by CPCB in selected polluting industries and the major findings, (vii) development of guidelines for conducting environmental audit in different categories of polluting industries, and (viii) the current status of the scheme and plans for its effective implementation.

Molecular characterization of the genes involved in O-antigen modification, attachment, integration and excision in Shigella flexneri bacteriophage SfV

Bacteriophage SfV is a temperate phage of Shigella flexneri responsible for converting serotype Y (3,4) to serotype 5a (V; 3,4) through its glucosyl transferase gene. The glucosyl transferase (gtr) gene of SfV has been cloned and shown to partially convert S. flexneri serotype Y to serotype 5a. In this study, we found that the serotype-converting region of SfV was approximately 2.5 kb in length containing three continuous ORFs. The recombinant strain carrying the three complete ORFs expressed the type V and group antigen 3,4, both indistinguishable from that of S. flexneri 5a wild-type strain. The interruption of orf5 or orf6 gave partial conversion in the S. flexneri recombinant strain indicated by the incomplete replacement of group antigen 3,4. The region adjacent to the serotype-conversion genes was found to be identical to the attP-int-xis region of phage P22. Altogether, an approximately 2.2-kb sequence covering a portion of the serotype-conversion (approximately 500 nt)-attP-int-xis regions of SfV was remarkably similar to that of P22.

Shigella flexneri type-specific antigen V: cloning, sequencing and characterization of the glucosyl transferase gene of temperate bacteriophage SfV

With lysogeny by bacteriophage SfV, Shigella flexneri serotype Y is converted to serotype 5a. The glucosyl transferase gene (gtr) from bacteriophage SfV of S. flexneri, involved in serotype-specific conversion, was cloned and characterized. The DNA sequence of a 3.7 kb EcoRI-BamHI fragment of bacteriophage SfV which includes the gtr gene was determined. This gene, encoding a polypeptide of 417 aa with 47.67 kDa molecular mass, caused partial serotype conversion of S. flexneri from serotype Y to type V antigen as demonstrated by Western blotting and the sensitivity of the hybrid strain to phage Sf6. The deduced protein of the partially sequenced open reading frame upstream of the gtr showed similarity to various glycosyl transferases of other bacteria. Orf3, separated from the gtr by a non-coding region and transcribed convergently, codes for a 167 aa (18.8 kDa) protein found to have homology with tail fibre genes of phage lambda and P2.

Immune response to a Murray Valley encephalitis virus epitope expressed in the flagellin of an attenuated strain of Salmonella

Recent developments in vaccine construction include the use of attenuated, avirulent strains of Salmonella as carriers of foreign antigens. These recombinant strains can elicit a heterologous immune response when injected into animals, demonstrating potential for their use in the construction of many vaccines. In the present study, a B-cell epitope of Murray Valley encephalitis virus (MVE) was identified and expressed in a Salmonella strain to evaluate its potential to induce a specific immune response to MVE. A synthetic oligonucleotide encoding the B-cell epitope (residues E201-224) of the envelope protein of MVE was inserted into the cloned flagellin gene of the Salmonella strain. The construct was sequenced to ensure correct orientation of the epitope. Expression of the epitope was demonstrated by Western blot analysis and immunogold electron microscopy with monoclonal antibody specific to the epitope. Electron microscopy analysis revealed multiple copies of the epitope along the flagella. The recombinant Salmonella carrying the hybrid flagellin gene elicited an immune response to the MVE epitope in a mouse model. The MVE-specific antibodies partially neutralised the virus in vitro. The significance of this system for engineering vaccines for other medically important flaviviruses is discussed.

Immunogenicity of the Shigella flexneri serotype Y (SFL 124) vaccine strain expressing cloned glucosyl transferase gene of converting bacteriophage SfX

The glucosyl transferase gene (gtr) from bacteriophage phage X (SfX) caused partial conversion of serotype Y (group antigen 3, 4) to X (group antigen 7, 8) when introduced into a candidate vaccine strain of Shigella flexneri serotype Y (SFL124). The gtr gene caused conversion of O-antigens but did not eliminate the adsorption of the corresponding phage SfX. The hybrid strain expressing both group antigens 7, 8 and 3, 4 showed 75% protection when immunized guinea pigs were challenged with a wild-type S. flexneri serotype X strain. No protection was observed against serotype Y challenge, although group antigen 3, 4 was detected in the LPS of the hybrid strain. This suggests the importance of O-antigen immunity in the host defense against shigellosis.

Delivery of class I and class II MHC-restricted T-cell epitopes of listeriolysin of Listeria monocytogenes by attenuated Salmonella

Using a Salmonella vaccine-Listeria infection model of intracellular infection, we studied the capacity of an attenuated strain of Salmonella carrying T-cell epitopes of listeriolysin (LLO) of L. monocytogenes to elicit epitope-specific T-cell responses. Class II (LLO 215-226) or class I (LLO 91-99) MHC-restricted T-cell epitopes of LLO were inserted within a central, hypervariable domain of the flagellin protein of an attenuated delta aroA Salmonella dublin strain. T cells from Listeria-immunized mice were activated by lysates or heat-killed preparations of Salmonella construct expressing the LLO 215-226 epitope, indicating that LLO 215-226 is processed and presented to T cells when offered to antigen-presenting cells as part of a flagellin-epitope fusion protein. The chimeric flagellin genes were integrated into the chromosome of the flagellin-negative S. dublin strain to obtain stable expression of the epitopes. Immunization with the living, chromosomally integrated Salmonella construct carrying LLO 215-226 epitope as part of the flagellin protein generated T cells reactive with the corresponding LLO peptide, indicating that this chimera can stimulate a class-specific immune response in vitro. The effect of flanking residues on the processing and presentation of MHC class I LLO 91-99 epitope was studied using Salmonella vaccine strains that express chimeric flagellins containing one of three LLO 91-99 inserts: 91-99 (normal flagellin amino acids as flanking residues); KK91-99KK (Lys-Lys flanking residues); and AAA91-99AAA (Ala-Ala-Ala flanking residues).(ABSTRACT TRUNCATED AT 250 WORDS)