Substance use and other correlates of HIV infection among transwomen and men who have sex with men in Perú: Implications for targeted HIV prevention strategies for transwomen.

Characterization of HIV risk factors among transwomen and men who have sex with men (MSM) should be assessed separately and independently. However, due to several constraints, these populations continue to be conflated in clinical research and data. There are limited datasets globally powered to make such comparisons. The study aimed to use one of the largest surveys of transwomen and MSM in Latin America to determine differences in HIV risk and related correlates between the two populations. Secondary data analysis was completed using a cross-sectional biobehavioral survey of 4413 MSM and 714 transwomen living in Perú. Chi Square analysis of selected HIV correlates was conducted to examine differences between transwomen and MSM. Additionally, stratified binary logistic regression was used to split data for further comparative analyses of correlates associated with transwomen and MSM separately. HIV prevalence among transwomen was two-fold greater than among MSM (14.9% vs. 7.0%, p<0.001). Transwomen had a higher prevalence of most HIV risk factors assessed, including presence of alcohol dependence (16.4% vs. 19.0%; p < .001) and drug use in the past 3 months (17.0% vs. 14.9%). MSM were more likely to use marijuana (68.0% vs. 50.0%, p < .001), and transwomen were more likely to engage in inhaled cocaine use (70.0% vs. 51.1%, p < .001). The regression exposed differences in correlates driving sub-epidemics in transwomen vs. MSM, with a trend of substance use increasing HIV risk for transwomen only. Transwomen were more likely to be HIV-infected and had different risk factors from MSM. Targeted prevention strategies are needed for transwomen that are at highest risk. Additionally, further research is needed to determine if these observations in Perú regarding substance use patterns and the role of substance use in HIV risk relate to other trans populations globally.

The filamentous type III secretion translocon of enteropathogenic Escherichia coli.

Enteropathogenic Escherichia coli (EPEC) uses a type III secretion system (TTSS) to inject effector proteins into the plasma membrane and cytosol of infected cells. To translocate proteins, EPEC, like Salmonella and Shigella, is believed to assemble a macromolecular complex (type III secreton) that spans both bacterial membranes and has a short needle-like projection. However, there is a special interest in studying the EPEC TTSS owing to the fact that one of the secreted proteins, EspA, is assembled into a unique filamentous structure also required for protein translocation. In this report we present electron micrographs of EspA filaments which reveal a regular segmented substructure. Recently we have shown that deletion of the putative structural needle protein, EscF, abolished protein secretion and formation of EspA filaments. Moreover, we demonstrated that EspA can bind directly to EscF, suggesting that EspA filaments are physically linked to the EPEC needle complex. In this paper we provide direct evidence for the association between an EPEC bacterial membrane needle complex and EspA filaments, defining a new class of filamentous TTSS.

Role of EscF, a putative needle complex protein, in the type III protein translocation system of enteropathogenic Escherichia coli.

Type III secretion systems, designed to deliver effector proteins across the bacterial cell envelope and the plasma membrane of the target eukaryotic cell, are involved in subversion of eukaryotic cell functions in a variety of human, animal and plant pathogens. In enteropathogenic Escherichia coli (EPEC), several protein substrates for the secretion apparatus were identified, including EspA, EspB and EspD. EspA is a structural protein and the major component of a large transiently expressed filamentous surface organelle that forms a direct link between the bacterium and the host cell, whereas EspD and EspB seem to form the mature translocation pore. Recent studies of the type III secretion systems of Shigella and Salmonella pathogenicity island (SPI)-1 revealed the existence of a macromolecular complex that spans both bacterial membranes and consists of a basal structure with two upper and two lower rings and a needle-like projection that extends outwards from the bacterial surface. MxiH (Shigella) and PrgI (Salmonella) are the main components of the needle of the type III secretion complex. A needle-like complex has not yet been reported in EPEC. In this study, we investigated EscF, a protein sharing sequence similarity with MxiH and PrgI. We report that EscF is required for type III protein secretion and EspA filament assembly. Moreover, we show that EscF binds EspA, suggesting that EspA filaments are an extension of the type III secretion needle complexes in EPEC.

Intimin-specific immune responses prevent bacterial colonization by the attaching-effacing pathogen Citrobacter rodentium.

The formation of attaching and effacing (A/E) lesions on gut enterocytes is central to the pathogenesis of enterohemorrhagic (EHEC) Escherichia coli, enteropathogenic E. coli (EPEC), and the rodent pathogen Citrobacter rodentium. Genes encoding A/E lesion formation map to a chromosomal pathogenicity island termed the locus of enterocyte effacement (LEE). Here we show that the LEE-encoded proteins EspA, EspB, Tir, and intimin are the targets of long-lived humoral immune responses in C. rodentium-infected mice. Mice infected with C. rodentium developed robust acquired immunity and were resistant to reinfection with wild-type C. rodentium or a C. rodentium derivative, DBS255(pCVD438), which expressed intimin derived from EPEC strain E2348/69. The receptor-binding domain of intimin polypeptides is located within the carboxy-terminal 280 amino acids (Int280). Mucosal and systemic vaccination regimens using enterotoxin-based adjuvants were employed to elicit immune responses to recombinant Int280alpha from EPEC strain E2348/69. Mice vaccinated subcutaneously with Int280alpha, in the absence of adjuvant, were significantly more resistant to oral challenge with DBS255(pCVD438) but not with wild-type C. rodentium. This type-specific immunity could not be overcome by employing an exposed, highly conserved domain of intimin (Int388-667) as a vaccine. These results show that anti-intimin immune responses can modulate the outcome of a C. rodentium infection and support the use of intimin as a component of a type-specific EPEC or EHEC vaccine.

Coiled-coil domain of enteropathogenic Escherichia coli type III secreted protein EspD is involved in EspA filament-mediated cell attachment and hemolysis.

Many animal and plant pathogens use type III secretion systems to secrete key virulence factors, some directly into the host cell cytosol. However, the basis for such protein translocation has yet to be fully elucidated for any type III secretion system. We have previously shown that in enteropathogenic and enterohemorrhagic Escherichia coli the type III secreted protein EspA is assembled into a filamentous organelle that attaches the bacterium to the plasma membrane of the host cell. Formation of EspA filaments is dependent on expression of another type III secreted protein, EspD. The carboxy terminus of EspD, a protein involved in formation of the translocation pore in the host cell membrane, is predicted to adopt a coiled-coil conformation with 99% probability. Here, we demonstrate EspD-EspD protein interaction using the yeast two-hybrid system and column overlays. Nonconservative triple amino acid substitutions of specific EspD carboxy-terminal residues generated an enteropathogenic E. coli mutant that was attenuated in its ability to induce attaching and effacing lesions on HEp-2 cells. Although the mutation had no effect on EspA filament biosynthesis, it also resulted in reduced binding to and reduced hemolysis of red blood cells. These results segregate, for the first time, functional domains of EspD that control EspA filament length from EspD-mediated cell attachment and pore formation.

EspA filament-mediated protein translocation into red blood cells.

Type III secretion allows bacteria to inject effector proteins into host cells. In enteropathogenic Escherichia coli (EPEC), three type III secreted proteins, EspA, EspB and EspD, have been shown to be required for translocation of the Tir effector protein into host cells. EspB and EspD have been proposed to form a pore in the host cell membrane, whereas EspA, which forms a large filamentous structure bridging bacterial and host cell surfaces, is thought to provide a conduit for translocation of effector proteins between pores in the bacterial and host cell membranes. Type III secretion has been correlated with an ability to cause contact-dependent haemolysis of red blood cells (RBCs) in vitro. As EspA filaments link bacteria and the host cell, we predicted that intimate bacteria-RBC contact would not be required for EPEC-induced haemolysis and, therefore, in this study we investigated the interaction of EPEC with monolayers of RBCs attached to polylysine-coated cell culture dishes. EPEC caused total RBC haemolysis in the absence of centrifugation and osmoprotection studies were consistent with the insertion of a hydrophilic pore into the RBC membrane. Cell attachment and haemolysis involved interaction between EspA filaments and the RBC membrane and was dependent upon a functional type III secretion system and on EspD, whereas EPEC lacking EspB still caused some haemolysis. Following haemolysis, only EspD was consistently detected in the RBC membrane. This study shows that intimate bacteria-RBC membrane contact is not a requirement for EPEC-induced haemolysis; it also provides further evidence that EspA filaments are a conduit for protein translocation and that EspD may be the major component of a translocation pore in the host cell membrane.

Structural basis for recognition of the translocated intimin receptor (Tir) by intimin from enteropathogenic Escherichia coli.

Intimin is a bacterial adhesion molecule involved in intimate attachment of enteropathogenic and enterohaemorrhagic Escherichia coli to mammalian host cells. Intimin targets the translocated intimin receptor (Tir), which is exported by the bacteria and integrated into the host cell plasma membrane. In this study we localized the Tir-binding region of intimin to the C-terminal 190 amino acids (Int190). We have also determined the region's high-resolution solution structure, which comprises an immunoglobulin domain that is intimately coupled to a novel C-type lectin domain. This fragment, which is necessary and sufficient for Tir interaction, defines a new super domain in intimin that exhibits striking structural similarity to the integrin-binding domain of the Yersinia invasin and C-type lectin families. The extracellular portion of intimin comprises an articulated rod of immunoglobulin domains extending from the bacterium surface, conveying a highly accessible 'adhesive tip' to the target cell. The interpretation of NMR-titration and mutagenesis data has enabled us to identify, for the first time, the binding site for Tir, which is located at the extremity of the Int190 moiety.

The type III protein translocation system of enteropathogenic Escherichia coli involves EspA-EspB protein interactions.

Enteropathogenic Escherichia coli (EPEC), like many bacterial pathogens, use a type III secretion system to deliver effector proteins across the bacterial cell wall. In EPEC, four proteins, EspA, EspB, EspD and Tir are known to be exported by a type III secretion system and to be essential for 'attaching and effacing' (A/E) lesion formation, the hallmark of EPEC pathogenicity. EspA was recently shown to be a structural protein and a major component of a large, transiently expressed, filamentous surface organelle which forms a direct link between the bacterium and the host cell. In contrast, EspB is translocated into the host cell where it is localized to both membrane and cytosolic cell fractions. EspA and EspB are required for translocation of Tir to the host cell membrane suggesting that they may both be components of the translocation apparatus. In this study, we show that EspB co-immunoprecipitates with the EspA filaments and that, during EPEC infection of HEp-2 cells, EspB localizes closely with EspA. Using a number of binding assays, we also show that EspB can bind and be copurified with EspA. Nevertheless, binding of EspA filaments to the host cell membranes occurred even in the absence of EspB. These results suggest that following initial attachment of the EspA filaments to the target cells, EspB is delivered into the host cell membrane and that the interaction between EspA and EspB may be important for protein translocation.

Structure of the cell-adhesion fragment of intimin from enteropathogenic Escherichia coli.

Enteropathogenic Escherichia coli (EPEC) induce gross cytoskeletal rearrangement within epithelial cells, immediately beneath the attached bacterium. The C-terminal 280 amino acid residues of intimin (Int280; 30.1 kDa), a bacterial cell-adhesion molecule, mediate the intimate bacterial host-cell interaction. Recently, interest in this process has been stimulated by the discovery that the bacterial intimin receptor protein (Tir) is translocated into the host cell membrane, phosphorylated, and after binding intimin triggers the intimate attachment. Using multidimensional nuclear magnetic resonance (NMR) and combining perdeuteration with site-specific protonation of methyl groups, we have determined the global fold of Int280. This represents one of the largest, non-oligomeric protein structures to be determined by NMR that has not been previously resolved by X-ray crystallography. Int280 comprises three domains; two immunoglobulin-like domains and a C-type lectin-like module, which define a new family of bacterial adhesion molecules. These findings also imply that carbohydrate recognition may be important in intimin-mediated cell adhesion.

Investigation of the role of conserved serine residues in the long form of the rat D2 dopamine receptor using site-directed mutagenesis.

Three serine residues (Ser193, Ser194, Ser197) in the fifth transmembrane-spanning region of the D2 dopamine receptor have been mutated separately to alanine and the effects of the mutations determined in ligand-binding experiments with [3H] spiperone. For many antagonists the mutations had little effect, showing that the overall conformation of the mutant receptors was similar to that of the native, although there were effects on the binding of certain antagonists. The effect of the mutations on agonist binding to the free receptor (uncoupled from G proteins) was determined in the presence of GTP (100 microM). This showed that there was no single mode of binding of catecholamine agonists to the receptor and that all three serine residues can participate in the binding of some agonists, possibly through hydrogen bonds to the catechol hydroxyl groups. Coupling of the mutant receptors to G proteins was assessed from agonist-binding curves in the absence of GTP, when higher and lower affinity agonist-binding sites were seen. Receptor/G protein coupling was generally unaffected by the Ala193 and Ala194 mutations, but the Ala197 mutation eliminated receptor/G protein coupling for some agonists. These data show that the interactions of agonists with the free and coupled forms of the receptor are different.

Structural studies on D2 dopamine receptors: mutation of a histidine residue specifically affects the binding of a subgroup of substituted benzamide drugs.

A histidine residue (His394) that is likely to be located in the ligand-binding region of the D2 dopamine receptor has been mutated to a leucine (Leu394), and the properties of the mutant receptor have been determined. For a range of antagonists the mutation has only a minor effect on the affinity of the receptor for the antagonist. The mutation does, however, elicit a structurally specific effect on the affinity with which certain members of the substituted benzamide class of antagonist bind to the receptor. Some of these drugs, e.g., sulpiride, sultopride, and tiapride, bind with reduced affinity to the mutated receptor, whereas others, e.g., clebopride and metoclopramide, bind with increased affinity. However, the Na+/H+ sensitivity of the binding of sulpiride to the receptor is not reduced by the mutation. These findings have been interpreted in terms of the productive or unfavourable interaction of the His394 residue with these compounds.

The value of percutaneous transluminal angioplasty of the profunda femoris artery in threatened limb loss and intermittent claudication.

Percutaneous transluminal angioplasty (PTA) has been performed on 29 profunda femoris artery stenoses in 26 limbs of 25 patients. Seventy per cent of the 27 atheromatous stenoses involved the origin or proximal 4 cm of the profunda. One patient had two strictures of a common femoral-profunda femoris vein graft. All had total superficial femoral or femoropopliteal occlusion (median length 29.5 cm, range 4-47 cm). The 13 patients presenting with threatened limb loss were significantly older than the remainder, who had disabling intermittent claudication (P = 0.03), and had twice the incidence of diabetes mellitus. They also had significantly fewer calf vessels patent compared with the claudicants (P = 0.008). The approaches used for profunda PTA included ipsilateral antegrade common femoral (19), ipsilateral retrograde profunda (3), cross-over technique (2), antegrade profunda (1) and brachial cutdown (1). Profunda PTA was technically successful at 26 sites (89.7%), partially successful at one, and failed at two. Concomitant PTA was successful at eight of 10 sites in eight patients. Complications requiring surgery occurred in two (7.7%). The median follow up was 17.5 months (range 1-62 months). Of the 12 limb salvage patients who underwent a technically successful profunda PTA, six required no further intervention, three subsequently underwent bypass grafting and three had an inevitable amputation, the level of amputation having been lowered in one of the patients. Nine claudicants improved symptomatically after technically successful profunda PTA; three underwent an operative procedure. Eight (61.5%) of the limb salvage group have now died, compared with two (15.4%) of the claudicants. Profunda femoris PTA is an effective alternative to profundaplasty in patients with femoropopliteal occlusive disease and may obviate the need for bypass surgery or amputation.

Computed tomography (CT) and ultrasound (US) guided core biopsy in the management of non-Hodgkin's lymphoma.

Histological examination of adequate biopsy specimens is fundamental to the management of patients with non-Hodgkin's lymphoma (NHL). A practical alternative to open biopsy, provided enough tissue can be obtained, has obvious advantages, especially if the lesion in question is deep seated, and might call for laparotomy or thoracotomy. Core biopsy with computed tomography (CT) or ultrasound (US) guidance may be such an alternative, particularly when a spring-loaded firing device is used. Thirty-four biopsies were performed in 26 patients with known or suspected NHL. A primary histological diagnosis was made in 7/7 (six NHL, one seminoma). Relapse was confirmed in 15/15 patients overall. In patients with follicular NHL, 8/15 biopsies showed progression to high grade histology. Biopsies were also performed to assess the nature of residual abnormalities after treatment and to obtain fresh tissue for immunocytochemistry. Tissue was obtained in all cases and a further procedure (two laparotomies, one second needle biopsy) was required on only three occasions. The procedure was well tolerated and there were no complications. This technique is therefore a valuable alternative to more invasive surgical procedures and may be of major benefit in the management of NHL.

Liposarcoma: a ten year experience.

A retrospective study of all patients presenting with liposarcoma at Southend General Hospital between the years 1970 and 1979 is presented. There were 13 patients in the group treated with various combinations of surgery and radiotherapy. The histology has been reviewed: 7 patients had myxoid tumours, 2 well differentiated and 4 pleomorphic. The patients were followed up for between 18-109 months with 7 patients followed for more than 5 years. Local recurrence was seen only in myxoid tumours whereas pleomorphic tumours showed a high incidence of distant metastases. The length of survival was found to correlate with the histology, pleomorphic tumours being associated with the shortest survival. The series illustrates that the histological type of liposarcoma predicts the pattern of behaviour of the tumour and is the major determinant in prognosis.