Cost-effectiveness of HIV screening in STD clinics, emergency departments, and inpatient units: a model-based analysis

Background

Identifying and treating persons with human immunodeficiency virus (HIV) infection early in their disease stage is considered an effective means of reducing the impact of the disease. We compared the cost-effectiveness of HIV screening in three settings, sexually transmitted disease (STD) clinics serving men who have sex with men, hospital emergency departments (EDs), settings where patients are likely to be diagnosed early, and inpatient diagnosis based on clinical manifestations.

Methods and Findings

We developed the Progression and Transmission of HIV/AIDS model, a health state transition model that tracks index patients and their infected partners from HIV infection to death. We used program characteristics for each setting to compare the incremental cost per quality-adjusted life year gained from early versus late diagnosis and treatment. We ran the model for 10,000 index patients for each setting, examining alternative scenarios, excluding and including transmission to partners, and assuming HAART was initiated at a CD4 count of either 350 or 500 cells/µL. Screening in STD clinics and EDs was cost-effective compared with diagnosing inpatients, even when including only the benefits to the index patients. Screening patients in STD clinics, who have less-advanced disease, was cost-effective compared with ED screening when treatment with HAART was initiated at a CD4 count of 500 cells/µL. When the benefits of reduced transmission to partners from early diagnosis were included, screening in settings with less-advanced disease stages was cost-saving compared with screening later in the course of infection. The study was limited by a small number of observations on CD4 count at diagnosis and by including transmission only to first generation partners of the index patients.

Conclusions

HIV prevention efforts can be advanced by screening in settings where patients present with less-advanced stages of HIV infection and by initiating treatment with HAART earlier in the course of infection.     

Radiomodulatory effect of liposome encapsulated AK-2123 on tumor in mice exposed to hepatocarcinogen

An attempt was made to evaluate the whole body -radiation effect on tumor in the presence of free and liposome encapsulated AK-2123, a hypoxic cell radiosensitizer that has widely been used in combination with a number of cancer therapies such as thermotherapy, chemotherapy and radiotherapy. Entrapment efficiency of AK-2123 into liposome was determined by LASER Raman spectroscopy. Cancer induction in mice was carried out by repeated exposure of N-nitrosodiethylamine (DEN) in combination with partial hepatectomy. Parameters such as marker enzymes activities (GGT and AChE), rates of nucleic acid synthesis, viability modification factor and the histology of liver tissues monitored, supported the induction of cancer in liver. In addition, the effect of free as well as liposome encapsulated AK-2123 on haemopoietic parameters were also studied. It was observed that AK-2123 after incorporation into liposome afforded more efficient radiomodulatory effects than that of free AK-2123 as determined by the above-mentioned parameters. Neither free AK-2123 nor liposome encapsulated AK-2123 showed any detectable toxic effects on the mice. Thus, it is seen that treatment of cancer with a combination of radiation, a radiomodifier and a drug delivery system, opens a wide scope for exploitation for the improvement of existing cancer therapies. (Mol Cell Biochem 271: 139–150, 2005)     

Solution conformation of Substance P antagonists-[D-Arg1, D-Trp7,9, Leu11]-SP, [D-Arg1, D-Pro2, D-Trp7,9, Leu11]-SP and [D-Pro2, D-Trp7,9]-SP by CD, NMR and MD simulations

Substance P (SP) is an important neuropeptide involved in pain transmission and induction of inflammation. Its antagonists are being extensively investigated for their non-narcotic analgesic and anti-inflammatory activity. With a view towards better understanding the structural requirements of these analogs for efficient interaction with the SP receptor, the conformation of three SP antagonists [D-Arg1, D-Trp7,9, Leu11]-SP, [D-Arg1, D-Pro2, D-Trp7,9, Leu11]-SP and [D-Pro2, D-Trp7,9]-SP has been studied by CD, NMR and molecular dynamics (MD) simulations. All three peptides exhibit a high dependence of structure on the solvent. The molecules tend to adopt beta-turns in solvents like DMSO and H2O and form helices in a hydrophobic environment. A direct relation between the helix forming potential of these antagonists with their receptor binding potency has been observed.     

Structural insight into the DNA polymerase beta deoxyribose phosphate lyase mechanism

A large number of biochemical and genetic studies have demonstrated the involvement of DNA polymerase beta (Pol beta) in mammalian base excision repair (BER). Pol beta participates in BER sub-pathways by contributing gap filling DNA synthesis and lyase removal of the 5'-deoxyribose phosphate (dRP) group from the cleaved abasic site. To better understand the mechanism of the dRP lyase reaction at an atomic level, we determined a crystal structure of Pol beta complexed with 5'-phosphorylated abasic sugar analogs in nicked DNA. This DNA ligand represents a potential BER intermediate. The crystal structure reveals that the dRP group is bound in a non-catalytic binding site. The catalytic nucleophile in the dRP lyase reaction, Lys72, and all other potential secondary nucleophiles, are too far away to participate in nucleophilic attack on the C1' of the sugar. An approximate model of the dRP group in the expected catalytic binding site suggests that a rotation of 120 degrees about the dRP 3'-phosphate is required to position the epsilon-amino Lys72 close to the dRP C1'. This model also suggests that several other side chains are in position to facilitate the beta-elimination reaction. From results of mutational analysis of key residues in the dRP lyase active site, it appears that the substrate dRP can be stabilized in the observed non-catalytic binding conformation, hindering dRP lyase activity.     

The Solution Structure of a Cyclic Analog of Neuropeptide Y with High Y<Subscript>1</Subscript> Receptor Affinity by NMR,CD and MD Simulations

The conformation of a cyclic analog of neuropeptide Y [Tyr¹--Lys--Gly--Arg--cyclo^5/8-(Glu⁵--Tyr--Ile--Lys⁸)--Leu--Ile¹⁰--Thr--Arg--Pro--Arg--Tyr¹⁵--NH₂; cEK-NPY] with high Y₁ receptor affinity was studied using ¹H, ¹³C and ¹⁵N 2D-NMR and CD in three diverse media-viz. DMSO-d₆, water (pH 4.0) and 50% hexafluoroacetone (HFA). The conformation of cEK-NPY was interpreted based on chemical shift (¹H, ¹³C and ¹⁵N), temperature coefficients of the NH chemical shifts, ³J_NHα coupling constants and the pattern of intra and inter-residue NOE’s and the CD spectrum. In both DMSO and water, there is a preponderance of a β-strand structure, while HFA promotes an α-helical structure, which is discontinuous in the mid-region of the peptide, due to the constraints of the lactam ring. The solution structures were generated using Restrained Molecular Dynamics simulations and further refined by Mardigras to R factors between 0.55 and 0.65. The role of its conformations in its biological activity is discussed.     

Guanidinium chloride- and urea-induced unfolding of FprA, a mycobacterium NADPH-ferredoxin reductase: stabilization of an apo-protein by GdmCl

The guanidinium chloride- and urea-induced unfolding of FprA, a mycobacterium NADPH-ferredoxin reductase, was examined in detail using multiple spectroscopic techniques, enzyme activity measurements and size exclusion chromatography. The equilibrium unfolding of FprA by urea is a cooperative process where no stabilization of any partially folded intermediate of protein is observed. In comparison, the unfolding of FprA by guanidinium chloride proceeds through intermediates that are stabilized by interaction of protein with guanidinium chloride. In the presence of low concentrations of guanidinium chloride the protein undergoes compaction of the native conformation; this is due to optimization of charge in the native protein caused by electrostatic shielding by the guanidinium cation of charges on the polar groups located on the protein side chains. At a guanidinium chloride concentration of about 0.8 m, stabilization of apo-protein was observed. The stabilization of apo-FprA by guanidinium chloride is probably the result of direct binding of the Gdm+ cation to protein. The results presented here suggest that the difference between the urea- and guanidinium chloride-induced unfolding of FprA could be due to electrostatic interactions stabilizating the native conformation of this protein.     

The Pro33 isoform of integrin beta3 enhances outside-in signaling in human platelets by regulating the activation of serine/threonine phosphatases

Integrin beta(3) is polymorphic at residue 33 (Leu(33) or Pro(33)), and the Pro(33)-positive platelets display enhanced aggregation, P-selectin secretion, and shorter bleeding times. Because outside-in signaling is critical for platelet function, we hypothesized that the Pro(33) variant provides a more efficient signaling than the Leu(33) isoform. When compared with Pro(33)-negative platelets, Pro(33)-positive platelets demonstrated significantly greater serine/threonine phosphorylation of extracellular signal-regulated kinase (ERK2) and myosin light chain (MLC) but not cytoplasmic phospholipase A2 upon thrombin-induced aggregation. Tyrosine phosphorylation of integrin beta(3) and the adaptor protein Shc was no different in the fibrinogen-engaged platelets from both genotypes. The addition of Integrilin (alpha(IIb)beta(3)-fibrinogen blocker) or okadaic acid (serine/threonine phosphatase inhibitor) dramatically enhanced ERK2 and MLC phosphorylation in the Pro(33)-negative platelets when compared with Pro(33)-positive platelets, suggesting that integrin engagement during platelet aggregation activates serine/threonine phosphatases. The phosphatase activity of myosin phosphatase (MP) that dephosphorylates MLC is inactivated by phosphorylation of the myosin binding subunit of MP at Thr(696), and aggregating Pro(33)-positive platelets exhibited an increased Thr(696) phosphorylation of MP. These studies highlight a role for the dephosphorylation events via the serine/threonine phosphatases during the integrin outside-in signaling mechanism, and the Leu(33) --> Pro polymorphism regulates this process. Furthermore, these findings support a mechanism whereby the reported enhanced alpha granule secretion in the Pro(33)-positive platelets could be mediated by an increased phosphorylation of MLC, which in turn is caused by an increased phosphorylation and subsequent inactivation of myosin phosphatase.     

Rapid self-assembly of alpha-synuclein observed by in situ atomic force microscopy

Self-assembly of alpha-synuclein resulting in protein aggregates of diverse morphology has been implicated in the pathogenesis of Parkinson's disease and other neurodegenerative disorders known as synucleinopathies. Apart from its biomedical relevance, this aggregation process is representative of the interconversion of an unfolded protein into nanostructures with typical amyloid features. We have used in situ tapping mode atomic force microscopy to continuously monitor the self-assembly of wild-type alpha-synuclein, its disease-related mutants A30P and A53T, and the C-terminally truncated variant alpha-synuclein(1-108). Different aggregation modes were observed depending on experimental conditions, i.e. pH, protein concentration, polyamine concentration, temperature and the supporting substrate. At pH 7.5, in the absence of the biogenic polyamines spermidine or spermine, elongated sheets 1.1(+/-0.2)nm in height and presumably representing individual beta-sheet structures, were formed on mica substrates within a few minutes. Their orientation was directed by the crystalline substructure of the substrate. In contrast, sheet formation was not observed with hydrophobic highly oriented pyrolytic graphite substrates, suggesting that negatively charged surfaces promote alpha-synuclein self-assembly. In the presence of spermidine or spermine 5.9(+/-1.0)nm high spheroidal structures were preferentially formed, sharing characteristics with similar structures previously reported for several amyloidogenic proteins and linked to neurotoxicity. alpha-Synuclein spheroid formation depended critically on polyamine binding to the C terminus, revealing a promoting effect of the C terminus on alpha-synuclein assembly in the bound state. In rare cases, fibril growth from spheroids or preformed aggregates was observed. At pH 5.0, fibrils were formed initially and incorporated into amorphous aggregates in the course of the aggregation process, providing evidence for the potential of amyloid fibril surfaces to act as nucleation sites in amorphous aggregation. This study provides a direct insight into different modes of alpha-synuclein self-assembly and identifies key factors modulating the aggregation process.