Antiretroviral treatment for injecting drug users in developing and transitional countries 1 year before the end of the "Treating 3 million by 2005. Making it happen. The WHO strategy" ("3 by 5")

OBJECTIVE: To describe and estimate the availability of antiretroviral treatment (ART) to injecting drug users (IDUs) in developing and transitional countries. METHODS: Literature review of grey and published literature and key informants' communications on the estimated number of current/former injecting drug users (IDUs) receiving ART and the proportion of human immunodeficiency virus (HIV) attributed to injecting drug use (IDU), the number of people in ART and in need of ART, the number of people living with HIV/acquired immunodeficiency syndrome (AIDS) (PLWHA) and the main source of ART. RESULTS: Data on former/current IDUs on ART were available from 50 countries (in 19 countries: nil IDUs in treatment) suggesting that approximately 34 000 IDUs were receiving ART by the end of 2004, of whom 30 000 were in Brazil. In these 50 countries IDUs represent approximately 15% of the people in ART. In Eastern European and Central Asia IDU are associated with > 80% of HIV cases but only approximately 2000 (14%) of the people in ART. In South and South-East Asia there were approximately 1700 former/current IDUs receiving ART ( approximately 1.8% of the people in ART), whereas the proportion of HIV cases associated to IDU is > 20% in five countries (and regionally ranges from 4% to 75%). DISCUSSION: There is evidence that the coverage of ART among current/former IDUs is proportionally substantially less than other exposure categories. Ongoing monitoring of ART by exposure and population subgroups is critical to ensuring that scale-up is equitable, and that the distribution of ART is, at the very least, transparent.     

Unraveling the molecular basis of subunit specificity in P pilus assembly by mass spectrometry

P pili are multisubunit fibers essential for the attachment of uropathogenic Escherichia coli to the kidney. These fibers are formed by the noncovalent assembly of six different homologous subunit types in an array that is strictly defined in terms of both the number and order of each subunit type. Assembly occurs through a mechanism termed “donor-strand exchange (DSE)” in which an N-terminal extension (Nte) of one subunit donates a β-strand to an adjacent subunit, completing its Ig fold. Despite structural determination of the different subunits, the mechanism determining specificity of subunit ordering in pilus assembly remained unclear. Here, we have used noncovalent mass spectrometry to monitor DSE between all 30 possible pairs of P pilus subunits and their Ntes. We demonstrate a striking correlation between the natural order of subunits in pili and their ability to undergo DSE in vitro. The results reveal insights into the molecular mechanism by which subunit ordering during the assembly of this complex is achieved.     

Focus on Kir6.2: a key component of the ATP-sensitive potassium channel

ATP-sensitive potassium (K(ATP)) channels are found in a wide variety of cell types where they couple cell metabolism to electrical activity. In glucose-sensing tissues, these channels respond to fluctuating changes in blood glucose concentration, but in other tissues they are activated only under ischemic conditions or in response to hormonal stimulation. Although K(ATP) channels in different tissues have different regulatory subunits, in almost all cases (except vascular smooth muscle) the pore-forming subunit is the inwardly rectifying K(+) channel Kir6.2. This article reviews recent studies of Kir6.2, focussing on the relation between channel structure and function, and on naturally occurring mutations in Kir6.2 that lead to human disease. New insights into the location of the ATP-binding site, the permeation pathway for K(+), and the gating of the pore provided by homology modelling are discussed in relation to functional studies. Gain-of-function mutations in Kir6.2 cause permanent neonatal diabetes mellitus (PNDM) by reducing the ATP sensitivity of the K(ATP) channel and increasing the K(ATP) current, which is predicted to inhibit beta-cell electrical activity and insulin secretion. Mutations at specific residues, that cause a greater decrease in ATP sensitivity, are associated with additional neurological symptoms. The molecular mechanism underlying the differences in ATP sensitivity produced by these two classes of mutations is discussed. We speculate on how some mutations lead to neurological disease and why no obvious cardiac symptoms are observed. We also consider the implications of these studies for type-2 diabetes.     

Acute effects of fatty acids on insulin secretion from rat and human islets of Langerhans

Fatty acids have both stimulatory and inhibitory effects on insulin secretion. Long-term exposure to fatty acids results in impaired insulin secretion whilst acute exposure has generally been found to enhance insulin release. However, there are conflicting data in the literature as to the relative efficacy of various fatty acids and on the glucose dependency of the stimulatory effect. Moreover, there is little information on the responses of human islets in vitro to fatty acids. We have therefore studied the acute effects of a range of fatty acids on insulin secretion from rat and human islets of Langerhans at different glucose concentrations. Fatty acids (0.5 mM) acutely stimulated insulin release from rat islets of Langerhans in static incubations in a glucose-dependent manner. The greatest effect was seen at high glucose concentration (16.7 mM) and little or no response was elicited at 3.3 or 8.7 mM glucose. Long-chain fatty acids (palmitate and stearate) were more effective than medium-chain (octanoate). Saturated fatty acids (palmitate, stearate) were more effective than unsaturated (palmitoleate, linoleate, elaidate). Stimulation of insulin secretion by fatty acids was also studied in perifused rat islets. No effects were observed at 3.3 mM glucose but fatty acids markedly potentiated the effect of 16.7 mM glucose. The combination of fatty acid plus glucose was less effective when islets had been first challenged with glucose alone. The insulin secretory responses to fatty acids of human islets in static incubations were similar to those of rat islets. In order to examine whether the responses to glucose and to fatty acids could be varied independently we used an animal model in which lactating rats are fed a low-protein diet during early lactation. Islets from rats whose mothers had been malnourished during lactation were still able to respond effectively to fatty acids despite a lowered secretory response to glucose. These data emphasise the complex interrelationships between nutrients in the control of insulin release and support the view that fatty acids play an important role in glucose homeostasis during undernutrition.     

Tissue-specific effects of sulfonylureas: lessons from studies of cloned K(ATP) channels

Sulfonylureas stimulate insulin secretion in type-2 diabetic patients by blocking ATP-sensitive (K(ATP)) potassium channels in the pancreatic beta-cell membrane. This effect is mediated by the binding of the drug to the sulfonylurea receptor (SUR) subunit of the channel. K(ATP) channels are also present in other tissues, but often contain different types of SUR subunits (e.g., SUR1 in beta-cells, SUR2A in heart, SUR2B in smooth muscle). The sensitivity of these different types of K(ATP) channels to sulfonylureas is variable: gliclazide and tolbutamide block the beta-cell, but not the cardiac or smooth muscle, types of K(ATP) channel. In contrast, glibenclamide blocks all three types of channel with similar affinity. The reversibility of the drugs also varies, with tolbutamide and gliclazide being reversible on all three types of K(ATP) channel, while glibenclamide is reversible on cardiac, but not beta-cell, K(ATP) channels. This review summarizes current knowledge of how sulfonylureas act on the different types of K(ATP) channel found in beta-cells and in extrapancreatic tissues, and discusses the implications of these findings for their use as therapeutic agents.     

Flow cytometric disease monitoring in multiple myeloma: the relationship between normal and neoplastic plasma cells predicts outcome after transplantation

Conventional monitoring strategies for myeloma are not sufficiently sensitive to identify patients likely to benefit from further therapy immediately after transplantation. We have used a sensitive flow cytometry assay that quantitates normal and neoplastic plasma cells to monitor the bone marrow of 45 patients undergoing high-dose chemotherapy. Neoplastic plasma cells were detectable at 3 months after transplantation in 42% of patients. Once detected, neoplastic cell levels increased steadily until clinical progression: these patients had a significantly shorter progression-free survival (PFS) (median, 20 months) than those with no detectable disease (median, longer than 35 months; P =.003). Neoplastic plasma cells were detectable in 27% (9 of 33) of immunofixation-negative complete-remission patients. These patients had a significantly shorter PFS than immunofixation-negative patients with no detectable neoplastic plasma cells (P =.04). Normal plasma cells were present in 89% of patients immediately after transplantation, but were not sustained in most cases. Patients with only normal phenotype plasma cells present at 3 months after transplantation and also at second assessment had a low risk of disease progression. Patients with neoplastic plasma cells present at 3 months after transplantation, or with only normal plasma cells present at first assessment and only neoplastic plasma cells at second assessment, had a significantly higher risk of early disease progression (P <.0001) with a 5-year survival of 54% for the high-risk group, compared with 100% in the low-risk group (P =.036). Analysis of normal and neoplastic plasma cell levels is more sensitive than immunofixation and can identify which patients may benefit from additional treatment strategies at an early stage after transplantation.     

Retrovirally marked CD34-enriched peripheral blood and bone marrow cells contribute to long-term engraftment after autologous transplantation

We report here on a preliminary human autologous transplantation study of retroviral gene transfer to bone marrow (BM) and peripheral blood (PB)-derived CD34-enriched cells. Eleven patients with multiple myeloma or breast cancer had cyclophosphamide and filgrastim-mobilized PB cells CD34-enriched and transduced with a retroviral marking vector containing the neomycin resistance gene, and CD34-enriched BM cells transduced with a second marking vector also containing a neomycin resistance gene. After high-dose conditioning therapy, both transduced cell populations were reinfused and patients were followed over time for the presence of the marker gene and any adverse effects related to the gene-transfer procedure. All 10 evaluable patients had the marker gene detected at the time of engraftment, and 3 of 9 patients had persistence of the marker gene for greater than 18 months posttransplantation. The marker gene was detected in multiple lineages, including granulocytes, T cells, and B cells. The source of the marking was both the transduced PB graft and the BM graft, with a suggestion of better long-term marking originating from the PB graft. The steady- state levels of marking were low, with only 1:1000 to 1:10,000 cells positive. There was no toxicity noted, and patients did not develop detectable replication-competent helper virus at any time posttransplantation. These results suggest that mobilized PB cells may be preferable to BM for gene therapy applications and that progeny of mobilized peripheral blood cells can contribute long-term to engraftment of multiple lineages.     

Reduction of serum matrix metalloproteinase 1 and matrix metalloproteinase 3 in rheumatoid arthritis patients following anti- tumour necrosis factor-alpha (cA2) therapy

Matrix metalloproteinase (MMP)-1 and MMP-3 levels were measured in serum samples from rheumatoid arthritis (RA) patients undergoing a double-blinded placebo-controlled trial with the chimaeric anti-tumour necrosis factor (TNF)-alpha antibody cA2. Both MMP-1 (P < 0.015), but to a larger extent MMP-3 (P < 0.001) levels were elevated in all RA patients prior to the commencement of the trial compared with normal control sera. Following cA2 therapy, MMP-1 and MMP-3 levels were assessed in the placebo, and 1 and 10 mg/kg cA2-treated groups at 7, 14, 21 and 28 days. In both the 1 and the 10 mg/kg cA2-treated groups, a significant decrease in serum MMP-3 levels at all time points was observed, reducing maximally to 41% of pre-infusion values at day 7. MMP-1 levels were also reduced, but less dramatically than MMP-3, to 85% of pre-infusion values after 14 days in the 10 mg/kg cA2 treated group. In a separate non-placebo-controlled study, we also evaluated the tissue inhibitor of metalloproteinase (TIMP)-1 levels in plasma following cA2 infusion. Pre-infusion TIMP-1 levels were above the normal control range, but were significantly reduced (P < 0.035) 14 days after infusion to 72% of pre-infusion values. This study confirms previous reports that MMP-3 levels are elevated and correlate with measures of inflammation in RA, and furthermore demonstrate that serum MMP-3 and MMP-1 levels are downmodulated following anti-TNF-alpha antibody therapy. Whilst serum MMP-3 levels correlated with C-reactive protein (CRP) both prior to and following anti-TNF-alpha antibody therapy, it remains to be demonstrated that serum MMP-3 and/or MMP-1 levels reflect the cartilage and bone resorptive processes which are evident in this disease.      

Phentolamine block of KATP channels is mediated by Kir6.2

The ATP-sensitive K⁺-channel (K_ATP channel) plays a key role in insulin secretion from pancreatic β cells. It is closed both by glucose metabolism and the sulfonylurea drugs that are used in the treatment of noninsulin-dependent diabetes mellitus, thereby initiating a membrane depolarization that activates voltage-dependent Ca²⁺ entry and insulin release. The β cell K_ATP channel is a complex of two proteins: Kir6.2 and SUR1. The former is an ATP-sensitive K⁺-selective pore, whereas SUR1 is a channel regulator that endows Kir6.2 with sensitivity to sulfonylureas. A number of drugs containing an imidazoline moiety, such as phentolamine, also act as potent stimulators of insulin secretion, but their mechanism of action is unknown. We have used a truncated form of Kir6.2, which expresses independently of SUR1, to show that phentolamine does not inhibit K_ATP channels by interacting with SUR1. Instead, our results argue that phentolamine may interact directly with Kir6.2 to produce a voltage-independent reduction in channel activity. The single-channel conductance is unaffected. Although the ATP molecule also contains an imidazoline group, the site at which phentolamine blocks is not identical to the ATP-inhibitory site, because phentolamine block of an ATP-insensitive mutant (K185Q) is normal. K_ATP channels also are found in the heart where they are involved in the response to cardiac ischemia: they also are blocked by phentolamine. Our results suggest that this may be because Kir6.2, which is expressed in the heart, forms the pore of the cardiac K_ATP channel.