Resistance to novel drug classes

Understanding the mechanisms that underlie resistance development to novel drugs is essential to a better clinical management of resistant viruses and to prevent further resistance development and spread. RECENT FINDINGS: Integrase inhibitors and CCR5 antagonists are the more recent antiretroviral classes developed. The HIV-1 integrase, responsible for the chromosomal integration of the newly synthesized double-stranded viral DNA into the host genomic DNA, represents a new and important target; and two integrase inhibitors (INIs), raltegravir and elvitegravir, have been shown promising results in clinical trials. Viral entry is also an attractive step for the development of new drugs against HIV variants resistant to current antiretroviral drugs, and two CCR5 antagonists have been designed to inhibit HIV-1 binding to R5 co-receptor and are under clinical investigation. SUMMARY: Drug resistance to INIs occurs through the selection of mutations within HIV integrase. The kinetic of selection seems rapid and one mutation alone is able to confer resistance to integrase inhibitor, suggesting that this class of drug has a low genetic barrier. Two ways could explain the failure of the CCR5 antagonist class: a rapid outgrowth of pre-existing archived X4 virus or the selection of a resistance to CCR5 antagonists through amino acid changes in V

Hypothermia for perinatal asphyxial encephalopathy. A Swiss survey of opinion, practice and cerebral investigations

BACKGROUND: Perinatal asphyxial encephalopathy occurs in 1-per 1000 live births and is associated with high mortality and morbidity. Therapeutic hypothermia increases intact survival and improves neurodevelopmental outcome in survivors.AIMS: To evaluate (i) the opinion and practice of therapeutic hypothermia as a therapy for moderate to severe perinatal asphyxial encephalopathy amongst Swiss neonatologists and paediatric intensive care specialists, (ii) the current clinical management of infants with perinatal asphyxial encephalopathy and (iii) the need for a national perinatal asphyxia and therapeutic hypothermia registry.METHODS: Two web-based questionnaires were sent to 18 senior staff physicians within the Swiss Neonatal Network.RESULTS: Therapeutic hypothermia was considered effective by all responders, however only 11 of 18 units provided therapeutic hypothermia. Cooling was initiated during transfer and performed passively in 82% of centres with a target rectal temperature of 33-34 degrees C. Most units ventilated infants with perinatal asphyxial encephalopathy if clinically indicated and 73% of responders gave analgesia routinely to cooled infants. Neuromonitoring included continuous amplitude integrated EEG (aEEG) and EEG. Neuroimaging included cranial ultrasound (cUS), magnetic resonance imaging (MRI) and computed tomography (CT). Sixty-seven percent of units treating infants with perinatal asphyxial encephalopathy performed MRI routinely. All heads of departments questioned indicated that a "Swiss National Asphyxia and Cooling Registry" is needed.CONCLUSIONS: In Switzerland, access to therapeutic hypothermia is widespread and Swiss neonatologists believe that therapeutic hypothermia for perinatal asphyxia is effective. National cooling protocols are needed for the management of infants with perinatal asphyxial encephalopathy in order to ensure safe cooling, appropriate monitoring, imaging and follow-up assessment. A national registry is needed to collect data on diagnosis, treatment, adverse events and outcome

The Formation of the First Low-Mass Stars From Gas With Low Carbon and Oxygen Abundances

The first stars in the Universe are predicted to have been much more massive than the Sun. Gravitational condensation accompanied by cooling of the primordial gas due to molecular hydrogen, yields a minimum fragmentation scale of a few hundred solar masses. Numerical simulations indicate that once a gas clump acquires this mass, it undergoes a slow, quasi-hydrostatic contraction without further fragmentation. Here we show that as soon as the primordial gas - left over from the Big Bang - is enriched by supernovae to a carbon or oxygen abundance as small as ~0.01-0.1% of that found in the Sun, cooling by singly-ionized carbon or neutral oxygen can lead to the formation of low-mass stars. This mechanism naturally accommodates the discovery of solar mass stars with unusually low (10^{-5.3} of the solar value) iron abundance but with a high (10^{-1.3} solar) carbon abundance. The minimum stellar mass at early epochs is partially regulated by the temperature of the cosmic microwave background. The derived critical abundances can be used to identify those metal-poor stars in our Milky Way galaxy with elemental patterns imprinted by the first supernovae.Comment: 14 pages, 2 figures (appeared today in Nature

Mechanisms underlying activity of antiretroviral drugs in HIV-1-infected macrophages: New therapeutic strategies

Monocyte-derived macrophages (M/M) are considered the second cellular target of HIV-1 and a crucial virus reservoir. M/M are widely distributed in all tissues and organs, including the CNS, where they represent the most common HIV-infected cells. Differently from activated CD4+ T lymphocytes, M/M are resistant to the cytopathic effect of HIV and survive HIV infection for a long lime. Moreover, HIV-1 replication in M/M is a key pathogenetic event during the course of HIV-1 infection. Overall findings strongly support the clinical relevance of anti-HIV drugs in M/M. Nucleoside RT inhibitors (NRTIs) are more active against HIV in M/M than in CD4+ T lymphocytes. Their activity is further boosted by the presence of an additional monophosphate group (i.e., a phosphonate group, as in the case of Tenofovir), thus overcoming the bottleneck of the low phosphorylation ability of M/M. In contrast, the antiviral activity of non-NRTIs (not affecting the DNA chain elongation) in M/M is similar to that in CD4+ T lymphocytes. Protease inhibitors are the only clinically approved drugs acting at a late stage of the HIV lifecycle. They are able to interfere with HIV replication in HIV-1 chronically infected M/M, even if at concentrations greater than those observed in HIV-1 chronically infected CD4+ T lymphocytes. Finally, several new drugs have been shown to interfere efficiently with HIV replication in M/M, including entry inhibitors. A better understanding of the activity of the anti-HIV drugs in M/M may represent a key element for the design of effective anti-HIV chemotherapy. © Society for Leukocyte Biology

Molecular analysis of hepatitis C virus infection in Bulgarian injecting drug users

Intravenous drug users constitute a group at risk for hepatitis C virus (HCV) infection. Today, no data are available on the molecular epidemiology of HCV in Bulgaria despite the fact that in recent years the incidence of acute hepatitis C infection among Bulgarian intravenous drug users increased sixfold and about 2/3 of them developed a chronic infection. The aim of this study was to determine the circulation of hepatitis C genotypes among drug users and to study the evolution and transmission history of the virus by molecular clock and Bayesian methods, respectively. Sequencing of NS5B gene showed that the genotype 3a was the most prevalent type among intravenous drug users. In the Bayesian tree, the 3a subtypes grouped in one main clade with one small cluster well statistically supported. The root of the tree was dated back to the year 1836, and the main clade from Bulgaria was dated 1960. The effective number of infections remained constant until about years 1950s, growing exponentially from the 1960s to the 1990s, reaching a plateau in the years 2000. The not significant intermixing with isolates from other countries may suggest a segregated circulation of the epidemic between 1940s and 1980s. The plateau reached by the epidemic in the early 2000s may indicate the partial success of the new preventive policies adopted in Bulgaria. J. Med. Virol. 83:1565-1570, 2011. © 2011 Wiley-Liss, Inc

Computational analysis of Human Immunodeficiency Virus (HIV) Type-1 reverse transcriptase crystallographic models based on significant conserved residues found in Highly Active Antiretroviral Therapy (HAART)-treated patients.

Reverse transcription of the viral single-stranded (+) RNA genome into double-stranded DNA is an essential step in the human immunodeficiency virus' (HIV) life-cycle. Although several viral proteins are involved in the regulation and/or efficiency of reverse transcription, the process of retroviral DNA synthesis is entirely dependent on the enzymatic activities of the retroviral reverse transcriptase enzyme (RT). Due to its crucial role in the HIV life-cycle, RT is a primary target for anti-HIV drug development. Nonetheless, drug resistance is the major problem affecting the clinical efficacy of antiretroviral agents. Incomplete pharmacological pressure represents the logical cause and not the consequence of different mutation pathways in RT associated with approved inhibitors resistance. In this review we have analyzed RT Protein Data Bank (PDB) models using our innovative computational approach “GRID Based Pharmacophore Model” (GBPM). This method was applied to clinically relevant RT conserved residues found in a large cohort of HAART treated patients. The PDB entries have been selected among the unbound and the complexed models with DNA and/or inhibitors. Such an approach has revealed itself useful to highlight the mutation effects in the drug-RT recognition as well as in the heterodimer stabilization of the enzyme. Most of the clinical and biochemical evidences already reported in the literature have been rationalized at molecular level via the GBPM computational approach. A definite future application of this method will be the identification of conserved regions of critical macromolecules, such as the HIV-1 RT, to be targeted for the development of innovative therapeutic agents

Monodromy--like Relations for Finite Loop Amplitudes

We investigate the existence of relations for finite one-loop amplitudes in Yang-Mills theory. Using a diagrammatic formalism and a remarkable connection between tree and loop level, we deduce sequences of amplitude relations for any number of external legs.Comment: 24 pages, 6 figures, v2 typos corrected, reference adde

Comparative replication capacity of raltegravir-resistant strains and antiviral activity of the new-generation integrase inhibitor dolutegravir in human primary macrophages and lymphocytes

To evaluate the replication capacity and phenotypic susceptibility to dolutegravir and raltegravir of wild-type and raltegravir-resistant HIV-1 strains in several cellular systems

Hydrostatic pressure does not cause detectable changes to survival of human retinal ganglion

Purpose: Elevated intraocular pressure (IOP) is a major risk factor for glaucoma. One consequence of raised IOP is that ocular tissues are subjected to increased hydrostatic pressure (HP). The effect of raised HP on stress pathway signaling and retinal ganglion cell (RGC) survival in the human retina was investigated. Methods: A chamber was designed to expose cells to increased HP (constant and fluctuating). Accurate pressure control (10-100mmHg) was achieved using mass flow controllers. Human organotypic retinal cultures (HORCs) from donor eyes (<24h post mortem) were cultured in serum-free DMEM/HamF12. Increased HP was compared to simulated ischemia (oxygen glucose deprivation, OGD). Cell death and apoptosis were measured by LDH and TUNEL assays, RGC marker expression by qRT-PCR (THY-1) and RGC number by immunohistochemistry (NeuN). Activated p38 and JNK were detected by Western blot. Results: Exposure of HORCs to constant (60mmHg) or fluctuating (10-100mmHg; 1 cycle/min) pressure for 24 or 48h caused no loss of structural integrity, LDH release, decrease in RGC marker expression (THY-1) or loss of RGCs compared with controls. In addition, there was no increase in TUNEL-positive NeuN-labelled cells at either time-point indicating no increase in apoptosis of RGCs. OGD increased apoptosis, reduced RGC marker expression and RGC number and caused elevated LDH release at 24h. p38 and JNK phosphorylation remained unchanged in HORCs exposed to fluctuating pressure (10-100mmHg; 1 cycle/min) for 15, 30, 60 and 90min durations, whereas OGD (3h) increased activation of p38 and JNK, remaining elevated for 90min post-OGD. Conclusions: Directly applied HP had no detectable impact on RGC survival and stress-signalling in HORCs. Simulated ischemia, however, activated stress pathways and caused RGC death. These results show that direct HP does not cause degeneration of RGCs in the ex vivo human retina

Instantaneous Shape Sampling - a model for the γ\gamma-absorption cross section of transitional nuclei

The influence of the quadrupole shape fluctuations on the dipole vibrations in transitional nuclei is investigated in the framework of the Instantaneous Shape Sampling Model, which combines the Interacting Boson Model for the slow collective quadrupole motion with the Random Phase Approximation for the rapid dipole vibrations. Coupling to the complex background configurations is taken into account by folding the results with a Lorentzian with an energy dependent width. The low-energy energy portion of the $\gamma$- absorption cross section, which is important for photo-nuclear processes, is studied for the isotopic series of Kr, Xe, Ba, and Sm. The experimental cross sections are well reproduced. The low-energy cross section is determined by the Landau fragmentation of the dipole strength and its redistribution caused by the shape fluctuations. Collisional damping only wipes out fluctuations of the absorption cross section, generating the smooth energy dependence observed in experiment. In the case of semi-magic nuclei, shallow pygmy resonances are found in agreement with experiment