Hierarchy of SPEA presentation to T cells by mouse MHC haplotypes

The ability of splenic antigen-presenting cells (APC) from nine independent mouse major histocompatibility complex (MHC) haplotypes to present recombinant streptococcal exotoxin A (rSPEA) to heterogeneous T cells and mouse T cell clones were compared using proliferation assays. We report that there is marked variation between MHC haplotypes, which can be ranked as follows: H2z > H2s = H2f = H2p = H2r = H2k > H2d > H2b = H2q. In some haplotypes both A and E molecules bind rSPEA with low affinity. In addition, we show that presentation is preferentially by E molecules in haplotypes where A and E are coexpressed, but that A alleles also bind and present rSPEA, based on inhibition of responses by anti-E and anti-A mAbs. Furthermore, using strains of mice which fail to express E, we demonstrate that A(s) and Af present rSPEA with high efficiency, whereas Aq and Ab are the least efficient of all haplotypes. The results suggest that there is significant variation in the ability of different alleles of both E and A molecules to bind and present rSPEA.

T-Cell epitope mapping the PorB protein of serogroup B Neisseria meningitidis in B10 congenic strains of mice

T-cell epitope mapping the meningococcal serotype 15 PorB protein performed in this study in three congenic strains of mice with B10 genetic background revealed at least three murine T-cell epitopes (55-72, 163-180, and 226-261), located in the highly conserved putative transmembrane regions of Neisserial porins. Proliferation assays with popliteal lymph node cells derived from mice immunized with the PorB protein or with synthetic 18-mer peptides showed that epitope 163-180 immunized only in the H-2d haplotype, epitope 55-72 could be presented by both H-2f and H-2s molecules, while the 226-261 region covered by three overlapping peptides could be efficiently recognized in context of all three MHC class II haplotypes studied. Inhibition experiments with blocking I-Aalpha- and I-Ealpha-specific mAb showed that peptide 163-180 was presented by I-Ad and peptide 244-261 was presented by both I-Af and I-As. In addition, evidence was obtained that peptide 226-243 was presented in context of H-2d or I-As haplotypes and peptide 55-72 was presented in context of I-Af and I-As loci. Finally, the Norwegian outer membrane vesicle vaccine, but not the purified PorB protein, could recall responses in mice immunized with synthetic peptides corresponding to the 226-261 region. Altogether, these results suggest that T-cell epitopes identified on the serotype 15 PorB protein, particularly those presented by several MHC class II molecules (e.g., 226-261), could have important implications for the development of meningococcal vaccines.

Streptococcus pyogenes type 5 M protein is an antigen, not a superantigen, for human T cells

M proteins are coiled-coil dimers expressed on group A streptococcal cell surfaces. They have an important role in host antistreptococcal immunity and in poststreptococcal autoimmune sequelae. Controversy has arisen regarding whether type 5 M proteins are superantigenic for human T cells. To investigate this, we have produced and tested M5 in the form of two novel recombinant proteins. We found no evidence of superantigenicity using either recombinant whole M5 protein (rM5) or recombinant pep M5 protein (rpepM5) to activate peripheral blood mononuclear cells (PBMC) from healthy adult volunteers. Short-term, rM5-specific T-cell lines from different subjects were uniformly self-APC restricted and showed no consistent pattern of TCR V beta usage. A synthetic peptide of M5 residues 217-237 was found to contain epitope(s) recognized by some rM5-specific human T cells. PBMC responses to rM5 and rpepM5 in 3- and 7-day proliferation assays were characteristic of antigenic rather than superantigenic stimulation. We conclude that type 5 M protein activates human T cells as a conventional antigen.

Effects of cigarette smoking on EEG spectral-band power, dimensional complexity, and nonlinearity during reaction-time task performance

Electroencephalogram (EEG) and heart rate (HR) were recorded while individuals performed visual and auditory go/no-go reaction time (RT) tasks. Overnight-abstaining smokers smoked two types of cigarettes in a single morning session. The first type was smoked once and had a nicotine yield of 0.05 mg. Two cigarettes of the second type (1.1 mg) were smoked. Four recordings were made: presmoking, postsmoking 0.05 mg, and postsmoking each 1.1 mg. HR was increased only by the first 1.1-mg cigarette. Smoking both the 1.1-mg cigarettes decreased RT. Smoking the first 1.1-mg cigarette increased EEG power in the beta2 band. A flexible effect of smoking the first 1.1-mg cigarette on EEG dimensional complexity (DCx) was obtained at locus Cz. Specifically, DCx was (a) raised when the presmoking level was low, (b) not affected when the presmoking level was intermediate, and (c) lowered when the presmoking level was high. Surrogate-data testing indicated the presence of nonlinearity in the EEG data that was not affected by smoking. Decreased RT was associated with increased DCx in the visual task only.

Assessing the sensory role of nicotine in cigarette smoking

Thirty-two subjects were tested in five double-blind sessions (16 subjects in the morning following overnight smoking abstention, and 16 in the afternoon following ad-lib smoking). In each session, subjects smoked one of five experimental (EX) cigarettes having the following FTC nicotine/"tar' yields in mg: 0.08/8.5, 0.17/9.1, 0.37/9.8, 0.48/9.8, and 0.74/10.4. In a sixth session, subjects smoked a 0.71/8.6 commercial "light' (CL) cigarette that was their usual brand. Before and after smoking, subjects subjectively rated their desire to smoke a cigarette of their usual brand and had blood samples drawn. Following smoking, subjects rated the cigarette on a variety of sensory dimensions; they also rated smoking satisfaction. Analysis of variance indicated that nicotine played an important sensory role for a variety of dimensions related to cigarette taste and sensory impact but not perceived draw. Principal-components analyses indicated that sensory factors were at least as important as nicotine pharmacology (indirectly indexed by the pre-to post-smoking rise in blood nicotine concentration) when considering smoking's overall effects on satisfaction, product acceptance, and reduction in desire to smoke.

Examining the relation between usual-brand nicotine yield, blood cotinine concentration and the nicotine- "compensation" hypothesis

Eight data sets relating usual-brand nicotine yield (FTC method or equivalent) to blood cotinine concentration are reviewed with respect to the so-called nicotine-"compensation" hypothesis, i.e., that all smokers achieve a specific level of nicotine in their blood, regardless of the FTC nicotine yield of the cigarette smoked. The data from the studies reviewed here indicate wide variability in blood cotinine concentrations over the range of FTC nicotine yields and that the nicotine-compensation hypothesis is not supported. On average, blood cotinine concentrations are found to be roughly midway between complete compensation (all smokers absorb equal amounts of nicotine regardless of FTC nicotine yield) and the value expected if there was no compensation (i.e., smokers absorb an amount of nicotine exactly equal to the FTC yield). As a result of individual smoking-behavior differences (number of cigarettes smoked, puff volume, puff frequency inhalation volume and depth, etc.), the data indicate that, on average, smokers achieve roughly 50% lower blood cotinine concentrations than predicted by the nicotine-compensation hypothesis.

Faster P300 latency after smoking in visual but not auditory oddball tasks

In two separate experiments, P300 was recorded from overnight-abstaining smokers before and after smoking. In the first experiment, 32 subjects counted forward by ones and counted backwards by threes upon presentation of a rare tone burst (20%) in a stream of standard tones. There were no changes in P300 amplitude or latency pre- to post-smoking (1.1-mg FTC nicotine-yield cigarette). In the second experiment, 29 subjects completed auditory and visual oddball tasks before smoking, after smoking a low nicotine-yield cigarette (0.05 mg), after smoking a higher nicotine-yield cigarette (1.1-mg), and after smoking a second 1.1-mg cigarette. In the visual oddball task, P300 latency decreased after smoking the first higher-yield cigarette relative to both pre-smoking and post smoking the lower-yield cigarette. This effect was maintained after smoking the second higher-yield cigarette. In the visual task, P300 amplitude increased after smoking the first higher-yield cigarette (from a lower baseline level) in a group of subjects with larger changes in tidal-breath CO but not in a group with smaller changes in CO. There were no effects of smoking on P300 amplitude or latency in the auditory tasks of either the first or second experiment.

Psychophysiological and subjective effects of cigarettes having varying nicotine yields but relatively constant "tar' yields

Thirty-two subjects were tested in five double-blind sessions-16 subjects in the morning (a.m.) following overnight smoking abstention, and 16 in the afternoon (p.m.) following ad lib smoking. In each session, subjects smoked 1 of 5 cigarettes having the following FTC nicotine/'tar' yields in mg: 0.08/8.5, 0.17/9.1, 0.37/9.8, 0.48/9.8, and 0.74/10.4. On a pre- to postsmoking basis, blood nicotine and heart rate increased with nicotine yield. The effect of nicotine yield on changes in self-rated anxiety was an inverted-U function, but this effect was possibly confounded by baseline differences. The following effects on EEG spectral-band magnitude were also obtained: (1) nicotine yields > or = 0.17 mg decreased delta; (2) nicotine yields of 0.37 and 0.48 mg decreased theta in a.m. subjects; (3) nicotine yields > or = 0.37 mg decreased alpha, the effect being greater in a.m. subjects; (4) no effect of yield on beta 1 was obtained; (5) nicotine yields of 0.48 and 0.74 mg increased the Cz-minus-T5 differential in beta 2. Pre- to postsmoking changes in this measure of beta 2 were not correlated with either blood nicotine or anxiety.

A late sternal wound infection caused by hematogenous spread of bacteria

A 56-year-old man presented with a sternotomy wound infection 6 months after coronary artery bypass grafting. The organism responsible was group B beta-hemolytic Streptococcus. This organism was simultaneously cultured from an infected diabetic ulcer on the patient's foot as well as from a total knee prosthesis. The Streptococcus apparently spread hematogenously to the sternum, an extremely rare cause of sternotomy wound infection.

Comparison of measured and FTC-predicted nicotine uptake in smokers

Cigarette smokers have a wide variety of "tar" and nicotine yields to choose from in the current market, ranging from 0.5 mg "tar" and less than 0.05 mg nicotine to 27 mg "tar" and 1.8 mg nicotine by the Federal Trade Commission (FTC) method. To understand better the relationship between FTC nicotine yields and actual nicotine uptake in smokers, we have studied nicotine uptake in 33 smokers of self-selected products representing four "tar" groupings: 1 mg "tar" (1MG), ultra-low "tar" (ULT), full-flavor low "tar" (FFLT), and full flavor (FF) cigarettes. These cigarette categories had mean FTC nicotine yields of 0.14, 0.49, 0.67, and 1.13 mg/cigarette, respectively. The subjects smoked their usual brand of cigarette ad libitum and provided a 24-h urine sample for total nicotine uptake analysis over a period during which the number of cigarettes smoked was recorded. Nicotine uptake was determined by monitoring urinary nicotine and its metabolites, including the glucuronide conjugates. Daily nicotine uptake was 9.1 +/- 7.3 mg (range 1-21 mg) for 1MG, 19.2 +/- 10.0 mg (range 4-42 mg) for ULT, 21.8 +/- 9.4 mg (range 13-38 mg) for FFLT, and 37.1 +/- 14.4 mg (range 21-60 mg) for FF smokers. On a per cigarette basis, yields were 0.23 +/- 0.11, 0.56 +/- 0.23, 0.60 +/- 0.18, and 1.19 +/- 0.43 mg nicotine, respectively. Although individual variability was fairly large (CVs of 0.39-0.80), means for the different groups showed that lower FTC yield smokers not only absorb less nicotine per 24-h period, but also per cigarette smoked. These data suggest that nicotine uptake is a function of individual smoking behavior within product design limits. We conclude from these data that, while FTC yield cannot precisely predict nicotine uptake for an individual smoker, it is useful in predicting and comparing actual nicotine uptake by smokers who select cigarettes with a particular FTC yield.

Grief responses, coping processes, and social support of widows: research with Roy's model

This ex post facto descriptive correlational design study of widows during their second year of bereavement utilizes Roy's adaptation model as a guiding framework. Contextual stimuli (social support, social network, income/education, spiritual beliefs) were related to the cognator function (coping process), which was related to adaptation outcome (grief response). Significant moderate positive relationships were found between social support and coping process, and between social network and coping process. A significant relationship was also found between coping process and grief response. The path model accounted for 18% explained variance.

Flow cytometric determination of intracellular calcium changes in human peripheral blood mononuclear cells during conjugation to tumour cell lines

Using a flow cytometric assay, conjugate formation between human peripheral blood mononuclear cells (PBMC) and three different human tumour cell lines has been analysed. Changes in the intracellular calcium levels of PBMC were monitored using the calcium sensitive dye Fluo-3. Target cell populations were distinguished by forward scatter or following loading with the fluorescent dye, SNARF-1. Intracellular calcium was expressed as a ratio of fluorescence of conjugated to unconjugated PBMC and followed for ten minutes after initiation of conjugation. The results demonstrate an apparent increase in intracellular calcium in PBMC conjugated to the NK-sensitive cell line K562, and that the kinetics and magnitude of this response varied considerably between individuals. Tumour cells which were resistant to lysis (as determined in a 4 h chromium release assay) were also capable of eliciting a calcium response from PBMC. Although the induction of a rise in intracellular calcium was therefore not correlated with cytotoxicity, it was greater in IL-2-activated PBMC upon exposure to the same target cell lines as PBMC.

Caffeine and smoking: subjective, performance, and psychophysiological effects

The effects of caffeine and smoking on cognitive performance, subjective variables, heart rate, and EEG were assessed in two sessions. In one session, subjects received caffeine (2.5 mg/kg bodyweight), while in the other they received placebo. In both sessions they smoked a cigarette (8 cued puffs) having a nicotine yield of 1.2 mg. Caffeine produced an increase in self-reported muscular tension and tended to increase anxiety and delta magnitude. Smoking facilitated performance of a paper-and-pencil math task and increased heart rate. Smoking also appeared to produce cortical activation as indexed by decreased right frontal delta, decreased right centro-parietal theta, globally increased alpha, and increased centro-occipital/decreased posterior-temporal beta 1. Smoking also increased central/decreased posterior-temporal beta 2. Smoking and caffeine did not interact for any measure, suggesting that the epidemiological link between smoking and coffee drinking may have a non-pharmacological basis.

Identification of T cell autoepitopes that cross-react with the C-terminal segment of the M protein of group A streptococci

Rheumatic fever (RF) follows a throat infection with different M-serotypes of beta-hemolytic group A streptococci (GAS) and can affect different tissues, predominantly the heart. It is thought to be an autoimmune illness. Although histological examination of affected heart shows an infiltrate consisting mainly of T cells, antigens or epitopes that could be putative targets of autoimmune T cells have not been identified. We have examined the T cell response to the conserved C-terminal region of the M protein--a streptococcal surface coiled-coil protein which is the target of opsonic antibodies and antibodies which cross-react with human heart tissue. Australian Aborigine, Caucasian and Thai patients, controls and mice were studied to define regions of the protein immunogenic for T cells, and T cell lines and clones were tested for cross-reactivity to myosin as well as an extract of RF-diseased mitral heart valve. Murine (B10, B10.D2, B10.BR) M peptide-specific T cells were often cross-reactive for other M peptides but did not cross-react with human heart antigens. Patients with RF or other heart diseases, or control subjects exposed more commonly to GAS were more likely to have T cell responses to the M protein, with many regions of the C-terminus being recognized. T cell lines and a clone specific for different M peptides were generated from five donors. Cross-reactivity could be shown between different M peptides, but unlike murine M peptide-specific T cells three of the human T cell lines reacted strongly to peptides representing homologous regions of cardiac and skeletal muscle myosins, and two of these lines also responded to porcine myosin and an extract of human rheumatic mitral valve. However, these last two lines were derived from a normal donor without history of RF or other heart disease. Our data demonstrate that regions of the M protein, including regions that are being considered as subunit vaccines, have the potential to stimulate pre-existing heart cross-reactive T cells, but that the ability of such T cells to cross-react (as measured in vitro) is not in itself sufficient to lead to disease.

Expression and functional characterisation of a synthetic version of the human D4 dopamine receptor in a stable human cell line

A synthetic version of the human D4 (hD4) dopamine receptor was prepared. The G/C content of the natural gene was reduced by 14% without altering the amino acid composition of the corresponding protein sequence. HEK293 cells were transfected with the synthetic hD4 gene and stable clones resistant to G418 selected. The hD4 receptor expressed from the synthetic gene had identical pharmacological characteristics to the native hD4 receptor [(1991) Nature 350, 610-619; (1992) Nature 358, 149-152]. Functional studies with cells expressing the synthetic hD4 gene indicated negative coupling of this receptor to adenylate cyclase.

Processing of viable group A streptococci leads to major histocompatibility complex class II presentation of T cell epitopes from the major protective antigen

We have previously mapped major histocompatibility complex (MHC) class II-restricted T cell epitopes of the surface M protein of type 5 group A streptococci (M5) and show here that two out of four epitopes investigated were efficiently processed during incubation of viable streptococci with spleen cells for presentation to M5-specific murine T cell clones. Viable streptococci were processed more efficiently than heat-killed bacteria suggesting that secreted virulence factors of streptococci do not obstruct processing of streptococcal antigens in the dose range used. Epitopes from different regions of M5 could be ranked according to the efficiency with which they were processed, which may contribute to their relative immunodominance. It was further demonstrated that T cell clones specific for M5 308-319, an epitope from the M type conserved carboxy-terminal half of M5, cross-reacted between M5, M6 and M12, but not M49, streptococci. Helper T cell epitopes which are shared between streptococcal M types and are presented by MHC class II molecules on antigen-presenting cells after processing of viable streptococci could be particularly useful in the design of multivalent streptococcal vaccines.

Identification of two binding sites in staphylococcal enterotoxin B that confer specificity for TCR V beta gene products

The enterotoxins produced by Staphylococcus aureus are potent mitogens. They stimulate T cells in an oligoclonal fashion that is dependent on the expression of particular variable region gene elements in the beta-chain of the TCR (V beta). The fourth hypervariable loop of the TCR beta-chain is generally regarded as the site of contact for both viral and microbial superantigens. Recently, residues 60 and 61 of staphylococcal enterotoxin B (SEB) have been highlighted as central to the interaction of this toxin with the TCR. We have, therefore, analysed a series of toxins with mutations at these positions to investigate how amino acid substitutions affect the ability of mutant toxins to stimulate both human and mouse T cells. Each of the variant toxins induced proliferation in a murine V beta 8.3 T cell clone, whereas a V beta 8.1 T cell clone only responded to native toxin. A panel of nine human T cell clones expressing six different V beta elements, all of which responded to native SEB, was tested for reactivity to the variant toxins. Only one V beta 19.1+ T cell clone was found to be sensitive to substitution at positions 60 and 61 in a manner analogous to the murine V beta 8.1 T cell clone. Semi-quantitative analysis of the TCR V beta expression of human T cell lines expanded with native and mutant SEB revealed that none of the variant toxins could stimulate T cells that expressed V beta 19.1. Taken together, these results suggest that the interaction of mouse V beta 8.1 and human V beta 19.1 TCRs with SEB differs from other TCRs. Sequence comparisons of the different TCR V beta chains indicated that residues in the second complementarity determining region (CDR2) interact with the 60-61 loop of SEB. Therefore, a minimum of two distinct binding modules confer specificity to the interaction of the TCR with SEB.

The use of active centre acylation to control the pharmacokinetic profile of a recombinant chimaeric plasminogen activator

Recombinant hybrid plasminogen activators consisting of the "A" chain of plasminogen linked to the "B" chain of t-PA that are inhibited rapidly by plasma protease inhibitors have recently been described (Robinson et al. Circulation 1992; 86: 548-552). We have now shown that following bolus administration of native hybrid to guinea pigs, fibrinolytic activity was cleared rapidly from the circulation. Active centre acylation appeared to protect the hybrid from inhibition and allowed material to circulate as potentially active species for prolonged periods. Clearance rates of a range of acyl derivatives of the hybrid were 7-35-fold slower than for native hybrid and 20-100-fold slower than for t-PA. Clearance rates were influenced markedly by deacylation rate, such that clearance half-life correlated well with deacylation half-life. We have thus shown that it is feasible to control the pharmacokinetic profile of a recombinant hybrid plasminogen activator over a wide range by selection of an appropriate acyl group for attachment to the active site. Such control is not possible with plasminogen activators that are cleared predominantly by mechanisms other than inhibition.

Deletion of residues K296-G302 from the slowly-cleared tissue-type plasminogen activator t-PA del (G) leads to partial loss of plasminogen activating activity

Plasmids encoding tissue-type plasminogen activators lacking residues K296-G302 were constructed and were expressed in a Hela cell transient expression system. Conditioned media from the cultures were tested in a number of systems designed to detect function or antigen. Functional assays comprised the chromogenic substrate S2288 and three plasminogen activation assays. All t-PA variants were active in all assays but to varying degrees. The results are consistent with the conclusion that deletion of residues K296-G302 from the slowly-cleared t-PA mutant t-PA del(G) adversely affects the plasminogen activating ability of the molecule without altering the integrity of the active site. This is in contrast to the situation in native t-PA where the same mutation has little overall effect on activity.

Serial study of T lymphocytes in childhood leukemia during remission

Peripheral blood T lymphocyte numbers and function were studied in 22 children on UKALL X maintenance chemotherapy over a 2-year period, and results were compared with 20 healthy children. CD4 and CD8 subsets were enumerated using indirect immunofluorescence, and specific (HSV-1) and polyclonal (Con A, PWM) activation was studied by proliferation and IL-2/IL-4 production in vitro. T lymphocytes were significantly decreased with a greater fall in CD4 than CD8 T lymphocyte numbers. Proliferation responses were slightly but significantly decreased whereas IL-2 and IL-4 production were not significantly different from control values. These findings suggest that decreased numbers of CD4 helper T cells may be the most important factor in clinical immunodeficiency during maintenance chemotherapy for cALL contributing to increased susceptibility to opportunistic infections and argue against the presence of T lymphocytes with defective function.