Inhibition of antigen specific lymphocyte proliferation and cytokine stimulation by peptidomimetic opioid compound

In sequel to our preliminary observations with peptidomimetic opioid compounds, we have further investigated immunomodulatory activity of one peptidomimetic compound (Tyr-NH-CH2-CH2-O-Phe-NH2) with peripheral blood mononuclear cells (PBMCs) of healthy volunteers/tuberculosis patients. This peptidomimetic compound was evaluated for its effect on purified protein derivative (PPD) stimulated lymphocyte proliferation in vitro, production of Th1 and Th2 cytokines by ELISA and ribonuclease protection assay. Our study shows the immunosuppressive potential of above synthetic peptidomimetic compound. This compound inhibited PPD stimulated human lymphocyte proliferation and this inhibition was reversed by opioid receptor antagonist, naloxone. Its immunosuppressive effect was further demonstrated by inhibition of interleukin-9 (IL-9), IL-10 but failed to influence IL-2, IL-15 and interferon-y (IFN-gamma) in PPD stimulated human PBMCs.

Immunomodulation by biphalin, dimeric synthetic opioid peptide, and its analog

The opioid pentapeptides called enkephalins were originally described as the endogenous ligands for the opioid receptors. Although their precise physiological significance still remains elusive, the enkephalins have been reported to exhibit analgesic, antidepressant, antianxiety and anticonvulsant activities. In addition, enkephalins have also been shown to act as immunomodulator. The first generation of dimeric peptides was derived from enkephalins. Biphalin [(Tyr-D-Ala-Gly-Phe-NH)2] is a bivalent opioid analog containing two tyrosine residues. We have evaluated the immunomodulatory properties of biphalin and its analogs in various in vitro tests. We report that biphalin and one of its analogs [Tyr-D-Ala-Gly-Phe-NH.NH-Phe(p-Cl)-H] stimulate human T cell proliferation, natural killer (NK) cell cytotoxicity in vitro and interleukin-2 (IL-2) production. Biphalin and its analog also released chemokine like factor in the culture supernatant that was responsible for increased chemotaxis of monocytes. Furthermore, these peptides inhibited tumor necrosis factor (TNF-alpha) production in lipopolysaccharide (LPS) stimulated peripheral blood mononuclear cells (PBMC) and nitric oxide (NO) production in mouse macrophage cells, RAW 264.7. Our observations suggest immunomodulatory property of biphalin and its analog.

Cytokines in posterior uveitis: an update

T helper (Th) lymphocytes differentiate into two distinct subsets--Th1 and Th2--as defined by functional abilities and cytokine profiles. The functional differences between Th subsets are explained primarily through the activities of the cytokines they secrete. Interferon-gamma (IFN-gamma) is the signature cytokine of Th1 cells, which also produce interleukin-2 (IL-2) and tumor necrosis factor-beta (TNF-beta). IL-4 is the corresponding signature cytokine of Th2 cells, which also secrete IL-5, IL-6, IL-9, and IL-13. Recently, a few transcription factors have been identified that not only control the expression of cytokines of a particular type but also repress cytokines of other types. Human Th1 and Th2 cells not only produce a different set of cytokines but also exhibit distinct functional properties and the preferential expression of some activation markers. Pathophysiologically, the two subsets have been found to be mutually antagonistic. Various Th1 and Th2 cytokines appear to play an important role in the etiopathogenesis of posterior uveitis and its animal model, experimental autoimmune uveitis (EAU). The exact contribution of these mediators to uveitis remains to be defined. Recent studies suggest that a shift from Th1- to Th2-dominated response could be of therapeutic benefit. This review evaluates various studies in which uveitopathogenic and therapeutic potentials of various Th1 and Th2 cytokines have been investigated.

Molecular characterization of a chromosomal locus in Staphylococcus aureus that contributes to oxidative defence and is highly induced by the cell-wall-active antibiotic oxacillin

Previous studies employing two-dimensional gel electrophoresis and N-terminal protein sequencing have shown elevated synthesis of the enzyme methionine sulfoxide reductase (MsrA) in Staphylococcus aureus in response to cell-wall-active antibiotics. In the present study, the S. aureus msrA gene was cloned, overexpressed, purified as His-tagged MsrA and shown to have methionine sulfoxide reductase activity. The transcription of msrA was studied by assaying beta-galactosidase activity in an msrA promoter::lacZ fusion strain and by Northern blot analysis. Transcription of msrA was increased by oxacillin; but not by a variety of other stresses including H2O2. Northern blot analysis revealed that the size of the msrA transcript was 2.3 kb, considerably larger than the 531 nt msrA ORF. The msrA transcription start site was mapped 25 nt upstream of the msrA start codon. Computer analysis from database sequences indicated at least three additional ORFs downstream of msrA. The deduced amino acid sequences of two of these three ORFs showed significant sequence homologies to PilB, and enzyme IIA of the phosphotransferase system, respectively. The third ORF could not be identified by homology searches. Northern blot hybridization with probes specific to the msrA downstream region indicated that the S. aureus msrA was transcribed as part of a polycistronic message. Interestingly, purified S. aureus PilB was shown to possess approximately approximately 28-fold higher methionine sulfoxide reductase activity than the MsrA. An insertional knockout mutation in the first gene of this operon resulted in increased susceptibility of the mutant to H2O2 compared to the parent strain, but not to oxacillin.

Comparison of the mutant frequencies and mutation spectra of three non-genotoxic carcinogens, oxazepam, phenobarbital, and Wyeth 14,643, at the lambdacII locus in Big Blue transgenic mice

Oxazepam (OX), a widely used benzodiazepine anxiolytic, phenobarbital (PHE), a drug used for convulsive disorders, and Wyeth 14,643 (WY; [4-chloro-6-(2,3-xylidino)-2-pyrimidinylthio]acetic acid), a hypolipidemic agent, are all hepatocarcinogenic in B6C3F1 mice. They have been classified as "non-genotoxic" carcinogens since they are non-DNA reactive in in vitro assays and are either negative or weakly positive in Salmonella typhimurium (Ames assay). Male B6C3F1 Big Blue(R) transgenic mice were fed 2500 ppm of OX or PHE or 500 ppm of WY in their diet, while a control group of mice received diet alone for 180 days. The mutant frequency (MF) of cII in the control mice, after correction for clonality, was 6.2 +/- 2.8 x 10(-5). The MF values for mice fed OX, PHE, and WY were 10.0 +/- 3.6 x 10(-5) (P < 0.05), 7.9 +/- 1.3 x 10(-5) (P = 0.1) and 17.4 +/- 4.2 x 10(-5) (P < 0.01), respectively. The mutation spectrum (MS) at cII from the PHE-fed mice was significantly different (P < 0.05) from that of the control mice even though the MF was not, whereas the MS spectra of mice fed OX (P = 0.4) and WY (P = 0.7) were not significantly different. The PHE-derived spectrum differed from the spontaneous spectrum in the lower occurrence of G:C>C:G transversions (17 vs 1.6%) and the higher incidence of A:T>T:A transversions (3.4 vs 9.5%). Prior to correction for clonal expansion, each treated group exhibited a high incidence of frameshift mutations at the homopolymeric run of guanines at bp 179-184 (OX 21%, PHE 21%, WY 16% of the total mutations); this was not the case with the control group (6%). Even after clonal correction, more than 10% of the mutations were frameshifts in the treated mice, while 5% were frameshifts in the control mice. Despite this hypersensitive region of the gene, our findings suggest that the cII locus is less sensitive than the lacI locus to mutation induction by non-DNA reactive carcinogens.

Hyperplastic polyps of the esophagus and esophagogastric junction: histologic and clinicopathologic findings

Hyperplastic polyps of the esophagus and esophagogastric junction region (EGJ) are uncommon lesions characterized by hyperplastic epithelium (foveolar-type, squamous, or both) with variable amounts of inflamed stroma. They have been reported almost exclusively in the radiologic and clinical literature as occurring predominantly in association with gastroesophageal reflux disease (GERD). Comprehensive histologic and clinicopathologic evaluation of these polyps, their association with background mucosal pathology, and their association with Barrett's esophagus has not been previously performed. We studied 30 hyperplastic polyps from 27 patients and characterized the histologic, endoscopic, and clinical features of both the polyps and the background esophagus. Hyperplastic polyps were most common in the region of the EGJ (67%), followed by the distal esophagus (30%) and mid-esophagus (3%). Most (80%) were composed of predominantly cardiac-type mucosa, predominantly squamous mucosa (17%), or an admixture (3%). Intestinal metaplasia of the polyp was present in only 7% and low-grade dysplasia in only 3%. In the majority of cases (67%) hyperplastic polyps were associated with concurrent or recent ulcers or erosive esophagitis. In most cases (48%) esophageal injury was associated with GERD, but other potential etiologies included medications, infection, anastomotic or polypectomy sites, vomiting, and photodynamic therapy. Four patients (15%) had Barrett's esophagus, three of whom had or developed dysplastic Barrett's mucosa. These results underscore the pathogenesis of esophageal/EGJ region hyperplastic polyps as a mucosal regenerative response to surrounding mucosal injury. Careful clinical history and biopsy of the nonpolypoid mucosa are essential for determining the clinicopathologic context in which the polyps have developed.

Nitrate/nitrite reductase activity of sulfido/selenido bridged dinuclear ruthenium(III) complexes

Series of dinuclear species [Ru(2)(L)(2)(LH)(2)-mu-S(2)Cl(2)], [Ru(2)(L)(2)(LH)(4)-mu-Se(2)Cl(2)] (L=L(1)H and L(3)H) and [Ru(2)(L(2))(2)(L(2)H)-mu-Se(2)Cl(2)].2H(2)O, where L(1)H, L(2)H and L(3)H represent for 2-mercapto-5-phenyl-1,3,4-oxadiazole, 2-mercapto-benzimidazole and 2-mercapto-benzothiazole, respectively, have been prepared and characterized by their elemental analyses and spectral (IR, UV-visible, 1H NMR and FAB mass) data. The diamagnetism of these complexes are indicative of an exchange coupled dinuclear ruthenium(III) species containing S(2)(2-) and Se(2)(2-) bridges. The complexes along with free heterocycles (L(1)H-L(3)H) as well as RuCl(3) x 3H(2)0 were tested for their nitrate and nitrite reductase activities. The electrochemical behaviour of the complexes showed irreversible oxidation peaks at +(1.04-1.40) V quite comparable to those reported for sulphido bridged complexes.

Cell wall-active antibiotic induced proteins of Staphylococcus aureus identified using a proteomic approach

Proteins produced in elevated amounts in response to oxacillin challenge of Staphylococcus aureus strain RN450, were studied by comparing Coomassie blue stained two-dimensional gels of cellular proteins. At least nine proteins were produced in elevated amounts following exposure to growth inhibitory concentrations of oxacillin. N-terminal sequences were obtained for five of the proteins and the databases were searched to tentatively identify them. The proteins were identified as homologs of (i) methionine sulfoxide reductase (MsrA); (ii) a signal transduction protein (TRAP) involved in regulating RNAIII production encoded by the agr locus; (iii) transcription elongation factor GreA; (iv) the heat shock protein GroES; and (v) the enzyme IIA component of the phosphoenolpyruvate:sugar phosphotransferase system. A similar induction response was observed with the other cell wall-active antibiotics, but not with antibiotics that affect other cellular targets. Increased transcription of the msrA and groEL genes in response to cell wall-active antibiotics was also demonstrated. Although net protein synthesis is inhibited subsequent to inhibition of peptidoglycan biosynthesis by cell wall-active antibiotics, some proteins are induced in S. aureus, presumably in an attempt by the cell to counter the inhibitory effects of these agents.

Gluconobacter oxydans: its biotechnological applications

Gluconobacter oxydans is a gram-negative bacterium belonging to the family Acetobacteraceae. G. oxydans is an obligate aerobe, having a respiratory type of metabolism using oxygen as the terminal electron acceptor. Gluconobacter strains flourish in sugary niches e.g. ripe grapes, apples, dates, garden soil, baker's soil, honeybees, fruit, cider, beer, wine. Gluconobacter strains are non-pathogenic towards man and other animals but are capable of causing bacterial rot of apples and pears accompanied by various shades of browning. Several soluble and particulate polyol dehydrogenases have been described. The organism brings about the incomplete oxidation of sugars, alcohols and acids. Incomplete oxidation leads to nearly quantitative yields of the oxidation products making G. oxydans important for industrial use. Gluconobacter strains can be used industrially to produce L-sorbose from D-sorbitol; D-gluconic acid, 5-keto- and 2-ketogluconic acids from D-glucose; and dihydroxyacetone from glycerol. It is primarily known as a ketogenic bacterium due to 2,5-diketogluconic acid formation from D-glucose. Extensive fermentation studies have been performed to characterize its direct glucose oxidation, sorbitol oxidation, and glycerol oxidation. The enzymes involved have been purified and characterized, and molecular studies have been performed to understand these processes at the molecular level. Its possible application in biosensor technology has also been worked out. Several workers have explained its basic and applied aspects. In the present paper, its different biotechnological applications, basic biochemistry and molecular biology studies are reviewed.

Role of cytokines in experimental and clinical uveitis

Uveitis is a major cause of visual impairment. Experimental autoimmune uveitis mimics the clinical conditions of posterior uveitis in many ways. T-cells (particularly CD4+ helper-T-cells) have been shown to play an important role in pathogenesis of experimental and clinical uveitis. Based on the pattern of cytokine they secrete, CD4+ helper cells have been divided into Th1 and Th2 subsets. Various Th1 and Th2 cytokines appear to be involved in the pathogenesis and/or recovery from uveitis. This article discusses in detail the uveitopathogenic and therapeutic potential of Th1 and Th2 cytokines in experimental and clinical uveitis.

Simultaneous amplification of DNA and RNA virus using multiplex PCR system

A large number of disease-causing bacteria and viruses are being sequenced and PCR is increasingly used for the diagnosis of the diseases. We have designed a multiplex PCR system for hepatitis B virus (HBV), a DNA virus, and hepatitis E virus (HEV), an RNA virus. A modified technique has been standardized for simultaneous extraction of DNA and RNA, followed by a one-step RT-PCR/PCR.

Human retinal S-antigen: T cell epitope mapping in posterior uveitis patients

Uveitis, an intraocular inflammatory disease which affects the uveal tract and the retina of the eye in humans, is one of the major causes of visual impairment. Posterior uveitis is often associated with inflammation of the retina and vitreous. Unfortunately, etiological diagnosis of the disease is not possible in the majority of patients. It is generally felt that an autoimmune mechanism may be involved in so-called idiopathic cases. The role of retinal S-antigen, its 20 linear peptides spanning the entire sequence, and 2 additional peptides, known to be uveitopathogenic in experimental animals, was studied in 26 patients with uveitis. Lymphocyte proliferative response was tested in vitro to identify the epitopes of S-antigen involved and to establish their role in the pathogenesis of uveitis. Of 26 uveitis patients tested, 11 showed a significant T cell proliferative response in vitro to at least 1 antigen used. None among the controls showed any response to the peptides or native S-antigen used in this study. We have found that uveitis patients respond most frequently to peptide 4 (61--80), peptide 5 (81--100), peptide 8 (141--160), peptide 9 (161--180), peptide 12 (221--240), and peptide 13 (241--260) of the human S-antigen. These results further confirm that autoimmunity to retinal S-antigen may play a role in the etiopathogenesis of a subset of patients with idiopathic uveitis.

Hyperplastic polyps of the stomach: associations with histologic patterns of gastritis and gastric atrophy

Hyperplastic polyps are common gastric lesions characterized by hyperplastic foveolae with variable amounts of inflamed stroma. Their pathogenesis is unknown, but they have been reported to occur in association with various forms of chronic gastritis, particularly autoimmune gastritis and Helicobacter pylori gastritis. Comprehensive histologic evaluation of the background mucosal pathology in patients with hyperplastic polyps has not been previously performed. We studied 160 patients with gastric hyperplastic polyps and characterized endoscopic and histologic features of the polyps (i.e., location, multiplicity, and presence of dysplasia and adenocarcinoma) and the background gastric mucosa (i.e., intestinal metaplasia, dysplasia, carcinoma, and presence and classification of gastritis). Hyperplastic polyps were most common in the antrum (60%) and were multiple in 20% of patients. Focal intestinal metaplasia of the polyp was present in 16% and dysplasia in 4% of patients. Only one patient (0.6%) had adenocarcinoma within the polyp. Evaluation of the surrounding gastric mucosa showed at least focal intestinal metaplasia in 37% of patients, adenoma or low-grade flat epithelial dysplasia in 2%, and synchronous or metachronous adenocarcinoma in 6%. Eighty-five percent of patients had inflammatory mucosal pathology, most commonly active chronic H. pylori gastritis (25%), reactive or chemical gastropathy (21%), and metaplastic atrophic gastritis of the autoimmune (12%) or environmental (8%) type. These results indicate a strong association between various forms of gastritis and the development of hyperplastic polyps and further emphasize the importance of biopsy of the nonpolypoid gastric mucosa during endoscopic examination.

Detection of antibodies to Taenia solium in sera of patient with epilepsy using ELISA

Enzyme linked immunosorbent assay (ELISA) was used for detection of antibodies to cysticerci of Taenia solium in patients suffering from suspected neurocysticercosis. Serum antibodies to cysticercosis were detected in 10.4% of the patients. Antibodies were absent in healthy controls. No cross-reactivity was observed in sera from patients with other parasitic diseases viz. toxoplasmosis, filariasis and kala-azar. However sera from patients with hydatid disease showed cross reactions in 20%. Age group distribution showed gradual non-significant increase in seropositivity rates with advancing age. No significant gender difference, was observed. Analysis of dietary habits of patients showed statistically significant difference in seropositivity rates in non-vegetarians (15.4%) as compared to vegetarians (6.9%) (P value < .001).

Modulation of autoimmune diseases by nitric oxide

Nitric oxide (NO) is an intercellular messenger that performs a number of functions, including neurotransmission, vasodilatation, inhibition of platelet aggregation, and modulation of leukocyte adhesion. NO has recently been shown to act as a potent cytotoxic effector molecule as well as to play an important role in the pathogenesis of organ-specific autoimmunity. NO may also modulate the immune response by interfering with Th1/Th2 balance in autoimmune diseases. This review will discuss the role of NO and nitric oxide synthase (NOS) in pathophysiologic and therapeutic implications in various autoimmune diseases with particular reference to T helper-1 (Th1) and T helper-2 (Th2) cytokines.

Molecular characterization of the iron-hydroxamate uptake system in Staphylococcus aureus

To investigate iron uptake, a chromosomal locus containing three consecutive open reading frames, designated fhuC, fhuB, and fhuD, was identified in Staphylococcus aureus. Whereas the fhuC gene encodes an ATP-binding protein, fhuB and fhuD code for ferrichrome permeases and thus resemble an ATP-binding cassette transporter. A fhuB knockout mutant showed impaired uptake of iron bound to the siderophores but not of ferric chloride, suggesting that this operon is specific for siderophore-mediated iron uptake.

Immunomodulation by opioid peptidomimetic compound

OBJECTIVE

As a follow-up to our earlier studies on immunomodulation with opioid peptides, we synthesized and evaluated immunomodulatory activity of four peptidomimetic compounds, i.e. Tyr-NH-C(Me)(2)-CH(2)-O-Phe-NH(2 )(1), Tyr-NH-C(6)H(5)-(o)-CH(2)-CH(2)-O-Phe-NH(2) (2), Tyr-NH-CH(2)-CH(2)-O-Phe-NH(2) (3) and Tyr-NH-CH(D-Et)-CH(2)-O-Phe-NH(2) (4).

METHODS

These compounds were synthesized in solution phase and evaluated for their immunomodulatory properties in vitro by mixed lymphocyte reaction (MLR), proliferation of opioid receptor-expressing cells, production of tumor necrosis factor-alpha (TNF-alpha) and nitric oxide.

RESULTS

This study shows the immunosuppressive potential of synthetic peptidomimetic compound 3. This compound inhibited two-way MLR and suppressed the proliferation of the mu-opioid receptor expressing human embryonic kidney cells HEK 293 in vitro. Inhibition of MLR by compound 3 was reversed by naloxone (opioid receptor antagonist) and beta-funaltrexamine hydrochloride (mu-opioid receptor antagonist). The immunosuppressive effect of compound 3 was further demonstrated by inhibition of TNF-alpha and nitric oxide production in lipopolysaccharide-stimulated human PBMCs and mouse macrophage cells RAW 264.7, respectively.

CONCLUSION

These observations suggest that compound 3 inhibits MLR through mu-opioid receptor present on cells.

Evaluation of oxygen-dependent immunodefences of the polymorphonuclear cells of some tropical ruminants

Activation of polymorphonuclear cells (PMNs) leads to the formation of superoxide, which is in turn dismutated to H2O2 by superoxide dismutase (SOD) and is partly responsible for oxygen-dependent microbicidal activity. However, no comparative information is available on the effect of SOD inhibition before PMN activation to allow simulation of the SOD defects that are known to occur in some ruminants. This paper attempts to examine the degranulative and phagocytic responses in buffalo, cattle and goat PMNs exposed to diethyldithiocarbamate, a known SOD inhibitor. The activity of glutathione peroxidase and reductase was increased in the presence of SOD inhibitor. On activation, H2O2 production increased significantly (p < 0.01), while SOD inhibition before the activation of PMNs caused a significant decline in the production of H2O2 (p < 0.05) in all the species studied. There was a significant increase (p < 0.05) in the phagocytosis of Candida albicans spores by buffalo PMNs activated with opsonized zymosan. Activation of bovine PMNs after exposure to the SOD inhibitor resulted in a significant decline (p < 0.05) in phagocytic activity; in the other species, the two values only approached significance. Among the activators, opsonized zymosan caused a significant increase in phagocytic activity as compared to lipopolysaccharide, particularly in the PMNs of buffaloes (p < 0.05). Increased fungicidal activity (p < 0.05) occurred with opsonized zymosan-activated PMNs of all the species studied. The fungicidal activity was found to decline in PMNs exposed to SOD inhibitor before activation (p < 0.05). Interestingly, the phagocytic activity of caprine PMNs was found to be lower than that of PMNs from cattle (p < 0.05).

Cellular immune response to retinal S-antigen and interphotoreceptor retinoid-binding protein fragments in Eales' disease patients

The role of retinal antigens in Eales' disease was studied in 24 patients and an equal number of healthy controls. Lymphocyte proliferative responses were tested in vitro against native S-antigen, its uveitopathogenic peptides (peptide M and peptide G), yeast histone H3 peptide and uveitopathogenic fragment of interphotoreceptor retinoid-binding protein (IRBP; R16) to establish their role in the pathogenesis of Eales' disease. Out of 24 Eales' disease patients, 6 showed significant proliferative response against S-antigen, its uveitogenic fragments or IRBP. None among the controls showed any response to any retinal antigen used in this study. There was no statistically significant difference in the response to purified protein derivative between patients and controls. These results suggest that retinal antigens may play a role in the etiopathogenesis of Eales' disease. An extraneous agent that could result in exposure of normally sequestered uveitopathogenic antigens of the immune system, leading to an exuberant immune response in the eye may initiate the disease.

Low molecular weight protamine: a potent but nontoxic antagonist to heparin/low molecular weight protamine

To avoid bleeding complications, protamine is routinely used after cardiovascular surgery to neutralize the anticoagulant function of heparin. However, its clinical use is associated with adverse and sometimes fatal reactions. Based on literature review of the mechanism of heparin neutralization and protamine induced immunologic toxicity, we propose the following hypothesis: If a chain shortened low molecular weight protamine (LMWP) containing the heparin neutralizing domain could be derived from native protamine, it could be a potent and yet nontoxic heparin antagonist. In this study, we present results to validate this hypothesis. LMWP fragments containing an intact arginine sequence and an average molecular weight of approximately 1,100 daltons were successfully prepared by enzymatic digestion of protamine with thermolysin. In vitro studies show that such LMWP fragments completely neutralized the anticoagulant functions of heparin and LMWH, based on the anti-Xa chromogenic and aPTT clotting time assays. In vivo results reveal that although injection of protamine to mice led to obvious production of anti-protamine antibodies, injection of LMWP did not elicit any detectable immunogenic responses. In addition, these LMWP fragments exhibited a markedly reduced antigenicity and cross-reactivity toward the mice anti-protamine antibodies.

Characterization of passage-selected vancomycin-resistant Staphylococcus aureus strains of diverse parental backgrounds

A series of 12 Staphylococcus aureus strains of various genetic backgrounds, methicillin resistance levels, and autolytic activities were subjected to selection for the glycopeptide-intermediate S. aureus (GISA) susceptibility phenotype on increasing concentrations of vancomycin. Six strains acquired the phenotype rapidly, two did so slowly, and four failed to do so. The vancomycin MICs for the GISA strains ranged from 4 to 16 microg/ml, were stable to 20 nonselective passages, and expressed resistance homogeneously. Neither ease of acquisition of the GISA phenotype nor the MIC attained correlated with methicillin resistance hetero- versus homogeneity or autolytic deficiency or sufficiency. Oxacillin MICs were generally unchanged between parent and GISA strains, although the mec members of both isogenic methicillin-susceptible and methicillin-resistant pairs acquired the GISA phenotype more rapidly and to higher MICs than did their susceptible counterparts. Transmission electron microscopy revealed that the GISA strains appeared normal in the absence of vancomycin but had thickened and diffuse cell walls when grown with vancomycin at one-half the MIC. Common features among GISAs were reduced doubling times, decreased lysostaphin susceptibilities, and reduced whole-cell and zymographic autolytic activities in the absence of vancomycin. This, with surface hydrophobicity differences, indicated that even in the absence of vancomycin the GISA cell walls differed from those of the parents. Autolytic activities were further reduced by the inclusion of vancomycin in whole-cell and zymographic studies. The six least vancomycin-susceptible GISA strains exhibited an increased capacity to remove vancomycin from the medium versus their parent lines. This study suggests that while some elements of the GISA phenotype are strain specific, many are common to the phenotype although their expression is influenced by genetic background. GISA strains with similar glycopeptide MICs may express individual components of the phenotype to different extents.