T helper type-1 (Th1)/Th2 profiles of peripheral blood mononuclear cells (PBMC); responses to antigens of Chlamydia trachomatis in subjects with severe trachomatous scarring

Increased stimulation of Th2 cytokines may contribute to the development of persistent ocular chlamydial infection, resulting in the blinding pathological changes of trachoma. Proliferation and cytokine production profiles of PBMC in response to stimulation with antigens of Chlamydia trachomatis were compared in 30 patients with severe conjunctival scarring due to trachoma and in 30 age-, sex- and location-matched controls. Interferon-gamma (IFN-gamma) and IL-4 were detected at the single-cell level by ELISPOT assay. Transcription of the genes encoding IFN-gamma, IL-4 and IL-10 was detected in mRNA isolated from parallel cultures of PBMC using reverse transcriptase-polymerase chain reaction (RT-PCR). Incubation with the chlamydial heat shock protein (hsp)60 resulted in increased numbers of IL-4-producing cells in PBMC isolated from patients with scarring disease and increased secretion of IFN-gamma from PBMC of control subjects. Incubation with the chlamydial major outer membrane protein (MOMP) increased the number of IFN-gamma-producing cells in the control group only. Messenger RNA encoding IL-4 was only detected in PBMC of patients with scarring disease after in vitro stimulation with chlamydial antigens, but IFN-gamma mRNA and IL-10 mRNA were also more frequently detected in this group. Thirty-eight subjects were HLA-DRB1 and -DQB1 typed. Associations were observed between certain HLA class II alleles and cellular immune responses to chlamydial antigens. No HLA associations were found with clinical status, and overall we found no evidence of strong associations and the type of immune response. These data are consistent with a role for Th2 cells and cytokines in the pathogenesis of trachomatous scarring.

Opioid receptor imaging and displacement studies with [6-O-[11C] methyl]buprenorphine in baboon brain

Buprenorphine (BPN) is a mixed opiate agonist-antagonist used as an analgesic and in the treatment of opiate addiction. We have used [6-O-[11C]methyl]buprenorphine ([11C]BPN) to measure the regional distribution in baboon brain, the test-retest stability of repeated studies in the same animal, the displacement of the labeled drug by naloxone in vivo, and the tissue distribution in mice. The regional distribution of radioactivity in baboon brain determined with PET was striatum > thalamus > cingulate gyrus > frontal cortex > parietal cortex > occipital cortex > cerebellum. This distribution corresponded to opiate receptor density and to previously published data (37). The tracer uptake in adult female baboons showed no significant variation in serial scans in the same baboon with no intervention in the same scanning session. HPLC analysis of baboon plasma showed the presence of labeled metabolites with 92% +/- 2.2% and 43% +/- 14.4% of the intact tracer remaining at 5 and 30 min, respectively. Naloxone, an opiate receptor antagonist, administered 30-40 min after tracer injection at a dose of 1.0 mg/kg i.v., reduced [11C]BPN binding in thalamus, striatum, cingulate gyrus, and frontal cortex to values 0.25 to 0.60 of that with no intervention. There were minimal (< 15%) effects on cerebellum. Naloxone treatment significantly reduced the slope of the Patlak plot in receptor-containing regions. These results demonstrate that [11C]BPN can be displaced by naloxone in vivo, and they affirm the feasibility of using this tracer and displacement methodology for short-term kinetics studies with PET. Mouse tissue distribution data were used to estimate the radiation dosimetry to humans. The critical organ was the small intestine, with a radiation dose estimate to humans of 117 nrad/mCi.

Binding sites for abundant nuclear factors modulate RNA polymerase I-dependent enhancer function in Saccharomyces cerevisiae

The 190-base pair (bp) rDNA enhancer within the intergenic spacer sequences of Saccharomyces cerevisiae rRNA cistrons activates synthesis of the 35S-rRNA precursor about 20-fold in vivo (Mestel,, R., Yip, M., Holland, J. P., Wang, E., Kang, J., and Holland, M. J. (1989) Mol. Cell. Biol. 9, 1243-1254). We now report identification and analysis of transcriptional activities mediated by three cis-acting sites within a 90-bp portion of the rDNA enhancer designated the modulator region. In vivo, these sequences mediated termination of transcription by RNA polymerase I and potentiated the activity of the rDNA enhancer element. Two trans-acting factors, REB1 and REB2, bind independently to sites within the modulator region (Morrow, B. E., Johnson, S. P., and Warner, J. R. (1989) J. Biol. Chem. 264, 9061-9068). We show that REB2 is identical to the ABF1 protien. Site-directed mutagenesis of REB1 and ABF1 binding sites demonstrated uncoupling of RNA polymerase I-dependent termination from transcriptional activation in vivo. We conclude that REB1 and ABF1 are required for RNA polymerase I-dependent termination and enhancer function, respectively, Since REB1 and ABF1 proteins also regulate expression of class II genes and other nuclear functions, our results suggest further similarities between RNA polymerase I and II regulatory mechanisms. Two rDNA enhancers flanking a rDNA minigene stimulated RNA polymerase I transcription in a "multiplicative" fashion. Deletion mapping analysis showed that similar cis-acting sequences were required for enhancer function when positioned upstream or downstream from a rDNA minigene.

Transcriptional regulation by an upstream repression sequence from the yeast enolase gene ENO1

The activity of an upstream repression sequence (URS element) that mediates a 20-fold repression of ENO1 expression in cells grown in a medium containing glucose was characterized. Sequences that are sufficient for orientation-dependent ENO1 URS element activity were mapped between positions -241 and -126 relative to the ENO1 transcriptional initiation site. The ENO1 URS element repressed transcription of the yeast CYC1 gene when positioned between the CYC1 upstream activation sequences (UAS elements) and TATAAA boxes. The ENO1 URS element failed to repress transcription of the wild-type yeast enolase gene ENO2; however, expression of an ENO2 gene lacking one of the ENO2 UAS elements was efficiently repressed by the ENO1 URS element, suggesting that the URS element interferes with the transcriptional activation by some, but not all, UAS elements. In contrast to the ENO1 gene, the ENO1 URS element repressed CYC1 and ENO2 expression in cells grown on glucose or glycerol plus lactate. Evidence is presented that the ENO1 URS element also functions during stationary growth phase.

Preparation by site-directed mutagenesis and characterization of the E211Q mutant of yeast enolase 1

The published 'charge shuttle' mechanism of enolase (Lebioda, L. and Stec, B. (1991) Biochemistry 30, 2817-2822) assigns Glu-211 the task of orienting a water molecule that serves as the catalytic base which removes the proton from carbon-2 of the substrate. We prepared the E211Q mutant of yeast enolase 1 by site-directed mutagenesis. It appears to be folded correctly and to respond similarly to many of the normal ligands of enolase: it is stabilized against thermal denaturation by conformational Mg2+ and by Mg2+ and substrate and binds the chromophoric substrate analogue D-tartronate semialdehyde-2-phosphate (TSP) with affinity comparable to that of the native enzyme. However, it has only 0.01% (10(-4)) of the activity of native enolase under standard assay conditions and does not exhibit significantly more activity at various pH values or higher concentrations of substrate and Mg2+. Its ability to produce the form of enzyme-bound and reacted TSP that absorbs at shorter wavelengths is greatly slowed, while the longer wavelength absorbing form is produced rapidly. Overall, these observations are consistent with the hypothetical mechanism.

The GCR1 requirement for yeast glycolytic gene expression is suppressed by dominant mutations in the SGC1 gene, which encodes a novel basic-helix-loop-helix protein

The GCR1 gene product is required for maximal transcription of yeast glycolytic genes and for growth of yeast strains in media containing glucose as a carbon source. Dominant mutations in two genes, SGC1 and SGC2, as well as recessive mutations in the SGC5 gene were identified as suppressors of the growth and transcriptional defects caused by a gcr1 null mutation. The wild-type and mutant alleles of SGC1 were cloned and sequenced. The predicted amino acid sequence of the SGC1 gene product includes a region with substantial similarity to the basic-helix-loop-helix domain of the Myc family of DNA-binding proteins. The SGC1-1 dominant mutant allele contained a substitution of glutamine for a highly conserved glutamic acid residue within the putative basic DNA binding domain. A second dominant mutant, SGC1-2, contained a valine-for-isoleucine substitution within the putative loop region. The SGC1-1 dominant mutant suppressed the GCR1 requirement for enolase, glyceraldehyde-3-phosphate dehydrogenase, phosphoglycerate kinase, phosphoglycerate mutase, and pyruvate kinase gene expression. Expression of the yeast enolase genes was reduced three- to fivefold in strains carrying an sgc1 null mutation, demonstrating that SGC1 is required for maximal enolase gene expression. Expression of the enolase genes in strains carrying gcr1 and sgc1 double null mutations was substantially less than observed for strains carrying either null mutation alone, suggesting that GCR1 and SGC1 function on parallel pathways to activate yeast glycolytic gene expression.

Subjects recovering from human ocular chlamydial infection have enhanced lymphoproliferative responses to chlamydial antigens compared with those of persistently diseased controls

Cell-mediated immune responses to chlamydial and common recall antigens were measured in 26 subjects whose clinical signs of trachoma persisted over 6 months of follow-up and in 21 subjects whose clinical signs resolved spontaneously over the same period. Seven-day lymphocyte proliferative responses to chlamydial but not common recall antigens were significantly greater in subjects whose disease resolved spontaneously. There was, however, no detectable difference between the two groups in gamma interferon levels in supernatants from lymphocyte cultures stimulated with these antigens. These results are consistent with the hypothesis that cell-mediated immune responses play an important role in the clearance of ocular chlamydial infection in humans.

The upstream repression sequence from the yeast enolase gene ENO1 is a complex regulatory element that binds multiple trans-acting factors including REB1

Cis-acting sequences that modulate ENO1 URS (upstream repression site) element activity were identified by base pair substitution mutagenesis. Base substitution mutations within three distinct regions of the 125-base pair URS element caused partial loss of URS activity in vivo. A URS element containing all three mutations was inactive. A binding site for the yeast REB1 protein was identified near the 5' terminus of the ENO1 URS element. Base substitution mutations that disrupted REB1 binding in vitro caused a 30% loss of URS activity in vivo. A second DNA binding activity was identified which also bound near the 5' terminus of the URS element. This latter binding activity was not antigenically related to REB1 nor was binding of this activity affected by base substitution mutations that abolished REB1 binding. Base substitution mutations within a second region of the ENO1 URS element caused a 38% loss of URS activity in vivo. The nucleotide sequence of this latter region is very similar to essential sequences within the URS elements from the yeast CAR1 and SSA1 genes, respectively. Base substitution mutations within a third region near the 3' terminus of the ENO1 URS element caused a 70% loss of URS activity in vivo. These latter sequences bound a partially purified factor that was distinct from REB1. These results showed that ENO1 URS element activity was modulated by multiple cis-acting sequences that bound distinct trans-acting factors.

Conjunctival scarring in trachoma is associated with depressed cell-mediated immune responses to chlamydial antigens

In vitro responses of peripheral blood mononuclear cells (PBMC) were measured to antigens of Chlamydia trachomatis in 29 subjects with severe conjunctival scarring and compared with responses from 29 age-, sex-, and location-matched controls from a trachoma-endemic area in The Gambia. Proliferative and interferon-gamma responses were measured against chlamydial elementary bodies, recombinant major outer membrane protein, and affinity-purified recombinant chlamydial heat shock protein 60. Serum antibody levels in response to these antigens were also compared between the two groups, and the presence of ocular chlamydial antigen and DNA was assessed. PBMC from donors with conjunctival scarring had reduced proliferative responses to chlamydial antigens but not control antigens or mitogens compared with matched controls. By contrast, subjects with scarring had significantly higher levels of anti-chlamydial IgG antibody compared with matched controls and were more likely to be harboring ocular chlamydial antigen or DNA (or both).

Preparation and characterization of the E168Q site-directed mutant of yeast enolase 1

Yeast has two enolase isozymes (called 1 and 2), either of which suffices for growth. We cloned DNA encoding the enolase 1 protein coding and promoter regions flanked by BamHI termini using the PCR. The DNA, which contained no nucleotide base changes altering the protein sequence, was cloned into the multicopy shuttle vector pRS314 and transformed into a yeast strain with a deletion in its enolase 1 gene. The resulting plasmid-containing strain makes enolase 1 in quantities which depend on cell growth. A "charge shuttle" mechanism of action of enolase based on X-ray crystallographic evidence (Lebioda and Stec, Biochemistry 30:2817, 1991) involves Glu-168 accepting a proton from a water molecule that in turn accepts a proton from carbon-2 of the substrate. We prepared the E168Q mutant of enolase 1 by oligonucleotide-directed site-directed mutagenesis. Its identity was confirmed by N-terminal sequence analysis, HPLC on Superose 12, SDS-gel electrophoresis, and the sequence of the mutated DNA protein-coding region. The E168Q mutant has approximately 0.01% of the activity of native enolase. It binds substrate/product, AEP (3-aminoenolpyruvate-2-phosphate, the 3-amino analogue of the product phosphoenolpyruvate) and TSP (D-tartronate semialdehyde-2-phosphate, the aldehyde analogue of the substrate 2-phosphoglycerate), the latter two at least with affinities similar to those of the native enzyme. The E168Q enolase also produces absorbance changes in the analogues. The reaction with AEP is consistent with the "charge shuttle" mechanism; the reaction with TSP, which presumably requires proton removal from carbon-2, is complex but shows a very slow phase consistent with expectations.

A complex regulatory element from the yeast gene ENO2 modulates GCR1-dependent transcriptional activation

The GCR1 gene product is required for maximal transcription of many yeast genes including genes encoding glycolytic enzymes. Transcription of the yeast enolase gene ENO2 is reduced 50-fold in strains carrying a gcr1 null mutation. cis-acting sequences that are sufficient for GCR1-dependent regulation of ENO2 expression were identified by using an enhancerless CYC1 promoter which is not normally dependent on GCR1 for expression. A 60-bp ENO2 sequence that was sufficient to provide high-level, GCR1-dependent transcriptional activation of the CYC1 promoter was identified. This 60-bp element could be subdivided into a 30-bp sequence containing a novel RAP1-binding site and a GCR1-binding site which did not activate CYC1 transcription and a 30-bp sequence containing a novel enhancer element that conferred moderate levels of GCR1-independent transcriptional activation. The 60-bp CGCR1-dependent upstream activator sequence is located immediately downstream from previously mapped overlapping binding sites for the regulatory proteins ABFI and RAP1. Evidence is presented that the overlapping ABFI- and RAP1-binding sites function together with sequences that bind GCR1 and RAP1 to stage transcriptional activation of ENO2 expression.

Lymphocyte proliferative responses to chlamydial antigens in human chlamydial eye infections

In order to study the relationship between cell-mediated immune responses to Chlamydia trachomatis and the pathogenesis of human chlamydial eye disease, we have measured the peripheral blood lymphocyte proliferative responses to whole chlamydial elementary bodies in 40 subjects with oculogenital chlamydial infection of varying severity, 13 subjects with genital chlamydial infections and 12 healthy seronegative controls. The mean stimulation index was significantly higher in those with oculogenital infections than in controls. There was a strong correlation between the response to C. trachomatis serotypes B and L1. We studied the relationship between proliferative responses and four clinical parameters: follicular conjunctivitis, papillary hypertrophy, corneal pannus and epithelial punctate keratitis, but were unable to show a significant association with any of these. Nor was there any association between proliferative response and serum antibody titre to C. trachomatis (pooled serotypes D-K), duration of disease or quantitative isolation of chlamydia from the conjunctiva. The depletion of CD8+ cells had no consistent effect on proliferative responses to serotype L1 in 13 subjects.

Experimental autoimmune glomerulonephritis induced by homologous and isologous glomerular basement membrane in Brown-Norway rats

In order to study disease mechanisms and potential forms of therapy in glomerulonephritis, a model of experimental autoimmune glomerulonephritis (EAG) has been developed in the rat. We have examined the response of Brown-Norway (BN) rats to a single i.m. injection of collagenase-solubilised homologous (Sprague-Dawley, SD) or isologous (BN) glomerular basement membrane (GBM), with and without complete Freund's adjuvant (CFA). There was a dose-dependent circulating anti-GBM antibody response to all preparations of rat GBM. Animals given either antigen alone at a dose of 2 mg/kg developed circulating anti-GBM antibodies, which reached peak values by 6 weeks (63 +/- 5% following SD GBM; 53 +/- 8% following BN GBM), but did not develop glomerular deposits of IgG or nephritis. Animals given 2 mg/kg SD GBM in CFA developed greater concentrations of anti-GBM antibody by 6 weeks (122 +/- 20%) together with linear deposits of IgG on glomerular and tubular basement membranes (TBM), albuminuria (mean 7 mg/24 h), and variable focal segmental necrotising glomerulonephritis with mild interstitial nephritis. The same dose of BN GBM in CFA produced similar concentrations of circulating antibody (144 +/- 26%), with linear deposits of IgG on GBM but rarely TBM, little albuminuria, and variable mild focal glomerulonephritis. Other strains injected with SD GBM in CFA showed a variable circulating anti-GBM antibody response, which was similar to that of BN rats in PVG and DA rats but lower in LEW and WAG rats. Linear deposits of IgG on the GBM were detected in a proportion of PVG and DA rats, but not in LEW or WAG rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Aberrant DNA topoisomerase II activity, radioresistance and inherited susceptibility to cancer

Inherited susceptibility to a wide variety of neoplasias (Li-Fraumeni syndrome), has been shown in studies of one cancer-prone family, to have an intriguing association with an aberrant c-raf-1 gene and inheritance of a radioresistant phenotype in their non-cancerous skin fibroblasts. This association together with observations that DNA topoisomerases, when defective, can introduce errors into DNA and that these enzymes are perturbed in vitro by serine/threonine kinases similar to raf encoded proteins, prompted investigation of DNA topoisomerase activity of the family's fibroblasts. Since radioresistance was transferred to murine cells (NIH-3T3) when the aberrant c-raf-1 gene from this family was transfected, we also examined transformants containing this and other oncogenes. V-raf/c-myc and EJ-ras transformants were examined, the former because the family's skin fibroblasts also have 3-8-fold elevated myc expression (not apparently relevant to radioresistance) and the latter because ras, like raf, conveys radioresistance. The family members' fibroblasts and the three transfected murine lines, showed a similar perturbation of a spermidine and ATP-dependent DNA catenation activity (typical of DNA topoisomerase II). There was a significant positive correlation (r = 0.93; P = 0.0026) between the degree of activation of topoisomerase II and one measure of radioresistance (the Dq value). Relaxation of DNA supercoiling (topoisomerase I activity and other DNA nicking enzymes) was not abnormal. Cytotoxicity assays and evaluation of the influence of topoisomerase II inhibitors on DNA/protein complex formation, corroborated the existence of a qualitative topoisomerase II defect in the family's cells and transfectants. Although the contention that the qualitative topoisomerase II abnormalities observed here may be associated with malfunction is highly speculative, these findings may be relevant to the mechanism of oncogenesis, not only in this family, but with raf and ras type oncogenes.

A comparison of the brain uptake of N-(cyclopropyl[11C]methyl)norbuprenorphine ([11C]buprenorphine) and N-(cyclopropyl[11C]methyl)nordiprenorphine ([11C]diprenorphine) in baboon using PET

Buprenorphine and diprenorphine were radiolabeled with 11C and their distributions in the baboon brain were studied using positron emission tomography (PET). Specific binding was demonstrated in the striatum (but not in the cerebellum) by pretreating the baboon with (-)naloxone. The absolute striatal uptakes and time courses were similar for these two radioligands but the ratio of radioactivity in the striatum to cerebellum in the baboon was higher for [11C]diprenorphine than for [11C]buprenorphine. Analysis of baboon plasma indicated that both [11C]diprenorphine and [11C]buprenorphine are rapidly metabolized. Analysis of radioactivity in mouse brain indicated that these two radioligands are stable to metabolic transformation. At 30 min after injection, 86-90% of extracted radioactivity was due to unchanged 11C-labeled radioligands. These results suggest that both [11C]diprenorphine and [11C]buprenorphine may be useful radioligands for studying opioid receptors in humans, although [11C]diprenorphine may be a better radioligand than [11C]buprenorphine for this purpose because of its more rapid clearance from the cerebellum.