Complementation of diverse HIV-1 Env defects through cooperative subunit interactions: a general property of the functional trimer

<p>Abstract</p> <p>Background</p> <p>The HIV-1 Env glycoprotein mediates virus entry by catalyzing direct fusion between the virion membrane and the target cell plasma membrane. Env is composed of two subunits: gp120, which binds to CD4 and the coreceptor, and gp41, which is triggered upon coreceptor binding to promote the membrane fusion reaction. Env on the surface of infected cells is a trimer consisting of three gp120/gp41 homo-dimeric protomers. An emerging question concerns cooperative interactions between the protomers in the trimer, and possible implications for Env function.</p> <p>Results</p> <p>We extended studies on cooperative subunit interactions within the HIV-1 Env trimer, using analysis of functional complementation between coexpressed inactive variants harboring different functional deficiencies. In assays of Env-mediated cell fusion, complementation was observed between variants with a wide range of defects in both the gp120 and gp41 subunits. The former included gp120 subunits mutated in the CD4 binding site or incapable of coreceptor interaction due either to mismatched specificity or V3 loop mutation. Defective gp41 variants included point mutations at different residues within the fusion peptide or heptad repeat regions, as well as constructs with modifications or deletions of the membrane proximal tryptophan-rich region or the transmembrane domain. Complementation required the defective variants to be coexpressed in the same cell. The observed complementation activities were highly dependent on the assay system. The most robust activities were obtained with a vaccinia virus-based expression and reporter gene activation assay for cell fusion. In an alternative system involving Env expression from integrated provirus, complementation was detected in cell fusion assays, but not in virus particle entry assays.</p> <p>Conclusion</p> <p>Our results indicate that Env function does not require every subunit in the trimer to be competent for all essential activities. Through cross-talk between subunits, the functional determinants on one defective protomer can cooperatively interact to trigger the functional determinants on an adjacent protomer(s) harboring a different defect, leading to fusion. Cooperative subunit interaction is a general feature of the Env trimer, based on complementation activities observed for a highly diverse range of functional defects.</p

Quantitative assessment of renal perfusion and oxygenation by invasive probes: basic concepts

Renal tissue hypoperfusion and hypoxia are early key elements in the pathophysiology of acute kidney injury of various origins, and may also promote progression from acute injury to chronic kidney disease. Here we describe basic principles of methodology to quantify renal hemodynamics and tissue oxygenation by means of invasive probes in experimental animals. Advantages and disadvantages of the various methods are discussed in the context of the heterogeneity of renal tissue perfusion and oxygenation.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This introduction chapter is complemented by a separate chapter describing the experimental procedure and data analysis

Adjuvant platinum-based chemotherapy for early stage cervical cancer

BACKGROUND: This is an updated version of the original Cochrane review published in The Cochrane Library 2009, Issue 3. Most women with early cervical cancer (stages I to IIA) are cured with surgery or radiotherapy, or both. We performed this review originally because it was unclear whether cisplatin-based chemotherapy after surgery, radiotherapy or both, in women with early stage disease with risk factors for recurrence, was associated with additional survival benefits or risks. OBJECTIVES: To evaluate the effectiveness and safety of platinum-based chemotherapy after radical hysterectomy, radiotherapy, or both in the treatment of early stage cervical cancer. SEARCH METHODS: For the original 2009 review, we searched the Cochrane Gynaecological Cancer Group Trials Register, The Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library 2009, Issue 1), MEDLINE, EMBASE, LILACS, BIOLOGICAL ABSTRACTS and CancerLit, the National Research Register and Clinical Trials register, with no language restriction. We handsearched abstracts of scientific meetings and other relevant publications. We extended the database searches to November 2011 for this update. SELECTION CRITERIA: Randomised controlled trials (RCTs) comparing adjuvant cisplatin-based chemotherapy (after radical surgery, radiotherapy or both) with no adjuvant chemotherapy, in women with early stage cervical cancer (stage IA2-IIA) with at least one risk factor for recurrence. DATA COLLECTION AND ANALYSIS: Two review authors extracted data independently. Meta-analysis was performed using a random-effects model, with death and disease progression as outcomes. MAIN RESULTS: For this updated version, we identified three additional ongoing trials but no new studies for inclusion. Three trials including 368 evaluable women with early cervical cancer were included in the meta-analyses. The median follow-up period in these trials ranged from 29 to 42 months. All women had undergone surgery first. Two trials compared chemotherapy combined with radiotherapy to radiotherapy alone; and one trial compared chemotherapy followed by radiotherapy to radiotherapy alone. It was not possible to perform subgroup analyses by stage or tumour size. Compared with adjuvant radiotherapy, chemotherapy combined with radiotherapy significantly reduced the risk of death (two trials, 297 women; hazard ratio (HR) = 0.56, 95% confidence interval (CI): 0.36 to 0.87) and disease progression (two trials, 297 women; HR = 0.47, 95% CI 0.30 to 0.74), with no heterogeneity between trials (I(2) = 0% for both meta-analyses). Acute grade 4 toxicity occurred significantly more frequently in the chemotherapy plus radiotherapy group than in the radiotherapy group (risk ratio (RR) 5.66, 95% CI 2.14 to 14.98). We considered this evidence to be of a moderate quality due to small numbers and limited follow-up in the included studies. In addition, it was not possible to separate data for bulky early stage disease. In the one small trial that compared adjuvant chemotherapy followed by radiotherapy with adjuvant radiotherapy alone there was no significant difference in disease recurrence between the groups (HR = 1.34; 95% CI 0.24 to 7.66) and OS was not reported. We considered this evidence to be of a low quality. No trials compared adjuvant platinum-based chemotherapy with no adjuvant chemotherapy after surgery for early cervical cancer with risk factors for recurrence. AUTHORS’ CONCLUSIONS: The addition of platinum-based chemotherapy to adjuvant radiotherapy (chemoradiation) may improve survival in women with early stage cervical cancer (IA2-IIA) and risk factors for recurrence. Adjuvant chemoradiation is associated with an increased risk of severe acute toxicity, although it is not clear whether this toxicity is significant in the long-term due to a lack of long-term data. This evidence is limited by the small numbers and poor methodological quality of included studies. We await the results of three ongoing trials, that are likely to have an important impact on our confidence in this evidence