Hepatocyte growth factor as indicator for subclinical atherosclerosis

Background: Hepatocyte growth factor (HGF) is a pleiotropic cytokine mainly produced by mesenchymal cells. After endothelial damage by oxidized low-density lipoprotein (LDL), HGF is produced and released into the circulation in response. Due to this mechanism HGF has been proposed as possible clinical biomarker for clinical as well as subclinical atherosclerosis. Patients and methods: The conducted study is an observational, single centre, cohort study, including 171 patients with at least one cardiovascular risk factor or already established cardiovascular disease (CVD). Each patient underwent 3D plaque volumetry of the carotid and femoral arteries as well as physical examination and record of the medical history. Additionally, plasma HGF and further laboratory parameters like high sensitivity C-reactive protein and LDL-cholesterol were determined. Results: 169 patients were available for statistical analysis. In bivariate correlation, HGF showed a highly significant correlation with total plaque volume (TPV, r=0.48; p<0.001). In receiver operating characteristic (ROC) analysis for high TPV, HGF showed an area under the curve (AUC) of 0.68 (CI 95%: 0.59-0.77, p<0.001) with a sensitivity of 78% and a specificity of 52% to predict high TPV at a cut-off of 959 ng/ml. In the ROC-analysis for the presence of CVD, HGF demonstrated an AUC of 0.65 (95% CI 0.55-0.73; p=0.01) with a sensitivity of 77% and a specificity of 52%. Conclusions: Higher plasma levels of HGF are associated with higher atherosclerotic plaque volume as measured by 3D-ultrasound.

Correlation of 99mTc-DPD bone scintigraphy with histological amyloid load in patients with ATTR cardiac amyloidosis

BACKGROUND

The significance of measuring 99mTc-labelled-3,3-diphosphono-1,2-propanodicarboxylic acid (99mTc-DPD) in transthyretin (ATTR) cardiac amyloidosis has not been adequately studied. This single-centre observational study evaluated the correlation between 99mTc-DPD scintigraphy and histological amyloid load in endomyocardial biopsy (EMB).

METHODS

Twenty-eight patients with biopsy-proven ATTR amyloidosis and concomitantly available 99mTc-DPD scintigraphy were included. Visual Perugini scoring, and (semi-)quantitative analysis of cardiac 99mTc-DPD uptake by planar whole-body imaging and single photon emission computed tomography (SPECT/CT) using regions of interest (ROI) were performed. From this, heart-to-whole-body ratio (H/WB) and heart-to-contralateral-chest ratio (H/CL) were calculated. The histological amyloid load was quantified using two different staining methods.

RESULTS

Increased cardiac tracer uptake was documented in all patients (planar: ROImean 129 ± 37 cps; SPECT/CT: ROImean 369 ± 142 cps). Histological amyloid load (19 ± 13%) significantly correlated with Perugini score (r = 0.69, p < .001) as well as with cardiac 99mTc-DPD uptake (planar: r = 0.64, p < .001; H/WB: r = 0.50, p = .014; SPECT/CT: r = 0.53, p = .008; H/CL: r = 0.43, p = .037) (results are shown for correlations with Congo Red-staining).

CONCLUSION

In ATTR, cardiac 99mTc-DPD uptake significantly correlated with histological amyloid load in EMB. Further studies are needed to implement thresholds in cardiac 99mTc-DPD uptake measurements for risk stratification and guidance of therapy.

SARS-CoV-2 activates the TLR4/MyD88 pathway in human macrophages: A possible correlation with strong pro-inflammatory responses in severe COVID-19

Background

Toll-like receptors (TLRs) play a pivotal role in the immunologic response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Exaggerated inflammatory response of innate immune cells, however, may drive morbidity and death in Coronavirus disease 19 (COVID-19).

Objective

We investigated the engagement of SARS-CoV-2 with TLR4 in order to better understand how to tackle hyperinflammation in COVID-19.

Methods

We combined RNA-sequencing data of human lung tissue and of bronchoalveolar lavage fluid cells derived from COVID-19 patients with functional studies in human macrophages using SARS-CoV-2 spike proteins and viable SARS-CoV-2. Pharmacological inhibitors as well as gene editing with CRISPR/Cas9 were used to delineate the signalling pathways involved.

Results

We found TLR4 to be the most abundantly upregulated TLR in human lung tissue irrespective of the underlying pathology. Accordingly, bronchoalveolar lavage fluid cells from patients with severe COVID-19 showed an NF-κB-pathway dominated immune response, whereas they were mostly defined by type I interferon signalling in moderate COVID-19. Mechanistically, we found the Spike ectodomain, but not receptor binding domain monomer to induce TLR4-dependent inflammation in human macrophages. By using pharmacological inhibitors as well as CRISPR/Cas9 deleted macrophages, we identify SARS-CoV-2 to engage canonical TLR4-MyD88 signalling. Importantly, we demonstrate that TLR4 blockage prevents exaggerated inflammatory responses in human macrophages infected with different SARS-CoV-2 variants, including immune escape variants B.1.1.7.-E484K and B.1.1.529 (omicron).

Conclusion

Our study critically extends the current knowledge on TLR-mediated hyperinflammatory responses to SARS-CoV-2 in human macrophages, paving the way for novel approaches to tackle severe COVID-19.

Take-home message

Our study combining human lung transcriptomics with functional studies in human macrophages clearly supports the design and development of TLR4 - directed therapeutics to mitigate hyperinflammation in severe COVID-19.

Increasing Soluble P-Selectin Levels Predict Higher Peripheral Atherosclerotic Plaque Progression

BACKGROUND AND AIMS

The adhesion molecule P-selectin is expressed by endothelial cells and platelets. It is involved in platelet activation and leukocyte adhesion, both important processes in the pathogenesis of atherosclerosis. Our study was designed to assess the predictive value of soluble P-selectin (sP-selectin) on the progression of peripheral atherosclerosis.

METHODS

This is an observational, single-center, cohort study that included 443 patients with established cardiovascular disease (CVD) or at least one cardiovascular risk factor. Over a period of 4 years, each patient underwent three-dimensional (3D) ultrasound to assess the plaque volume of the carotid and femoral arteries once per year. In addition, plasma sP-selectin levels were measured at each visit. The association between changes in sP-selectin and peripheral atherosclerotic plaque progression was assessed using growth curve models.

RESULTS

338 patients were available for statistical analysis. Each standard deviation increase in sP-selectin was significantly (p < 0.001) associated with a 46.09 mm3 higher plaque volume. In ROC-analysis, changes in sP-selectin over time showed an optimal cut-off value around Δ 0.0 µg/mL sP-selectin and significantly improved the predictive value of the ESC-SCORE (AUC for the combination of both parameters was 0.75 (95% CI 0.68-0.81, p < 0.001). Patients with increasing sP-selectin showed a significantly higher plaque progression compared to patients with decreasing or stable sP-selectin levels (202 mm3 vs. 110 mm3, p < 0.001).

CONCLUSIONS

Increasing sP-selectin levels can predict higher atherosclerotic plaque progression as measured by 3D ultrasound. We suggest serial measurements of sP-selectin as an easily measurable biomarker for peripheral atherosclerotic plaque progression.

The angiogenic neuropeptide catestatin exerts beneficial effects on human coronary vascular cells and cardiomyocytes

INTRODUCTION

Myocardial infarction (MI) induces irreversible tissue damage, eventually leading to heart failure. Exogenous induction of angiogenesis positively influences ventricular remodeling after MI. Recently, we could show that therapeutic angiogenesis by the neuropeptide catestatin (CST) restores perfusion in the mouse hind limb ischemia model by the induction of angio-, arterio- and vasculogenesis. Thus, we assumed that CST might exert beneficial effects on cardiac cells.

METHODS/RESULTS

To test the effect of CST on cardiac angiogenesis in-vitro matrigel assays with human coronary artery endothelial cells (HCAEC) were performed. CST significantly mediated capillary like tube formation comparable to vascular endothelial growth factor (VEGF), which was used as positive control. Interestingly, blockade of bFGF resulted in abrogation of observed effects. Moreover, CST induced proliferation of HCAEC and human coronary artery smooth muscle cells (HCASMC) as determined by BrdU-incorporation. Similar to the matrigel assay blockade of bFGF attenuated the effect. Consistent with these findings western blot assays revealed a bFGF-dependent phosphorylation of extracellular-signal regulated kinase (ERK) 1/2 by CST in these cell lines. Finally, CST protected human cardiomyocytes in-vitro from apoptosis.

CONCLUSION

CST might qualify as potential candidate for therapeutic angiogenesis in MI.

Inverse Correlation of Cholesterol Efflux Capacity with Peripheral Plaque Volume Measured by 3D Ultrasound

INTRODUCTION

Cardiovascular disease (CVD) is a systemic multifocal illness called atherosclerosis that causes artery constriction and blockage. By causing cholesterol to build up in the artery wall, hypercholesterolemia is a major factor in the pathophysiology of atherosclerotic plaque development. Reverse cholesterol transport is the process of transporting cholesterol from the periphery back to the liver through cholesterol efflux mediated by high-density lipoprotein (HDL). It was suggested that the cholesterol efflux capacity (CEC), which is inversely linked with cardiovascular risk, can serve as a stand-in measure for reverse cholesterol transport. In this work, we sought to investigate a potential link between the peripheral plaque volume (PV) and CEC.

METHODS

Since lipid-lowering therapy interferes with CEC, we performed a cross-sectional study of 176 patients (48.9% females) with one cardiovascular risk factor or known CVD that did not currently take lipid-lowering medication. CEC was determined using cAMP-treated ³H-cholesterol-labeled J774 cells. Cholesterol ester transfer protein (CETP)-mediated cholesterol ester transfer was measured by quantifying the transfer of cholesterol ester from radiolabeled exogenous HDL cholesterol to Apolipoprotein B-containing lipoproteins. PV in the carotid and the femoral artery, defined as the total PV, was measured using a 3D ultrasound system equipped with semi-automatic software.

RESULTS

In our patients, we discovered an inverse relationship between high total PV and CEC (p = 0.027). However, there was no connection between total PV and low-density lipoprotein cholesterol, lipoprotein (a), or CETP-mediated cholesterol ester transfer.

CONCLUSION

In patients not receiving lipid-lowering treatment, CEC inversely correlates with peripheral atherosclerosis, supporting its role in the pathophysiology of atherosclerosis.

Toll-Like Receptor 3 Mediates Aortic Stenosis Through a Conserved Mechanism of Calcification

BACKGROUND

Calcific aortic valve disease (CAVD) is characterized by a phenotypic switch of valvular interstitial cells to bone-forming cells. Toll-like receptors (TLRs) are evolutionarily conserved pattern recognition receptors at the interface between innate immunity and tissue repair. Type I interferons (IFNs) are not only crucial for an adequate antiviral response but also implicated in bone formation. We hypothesized that the accumulation of endogenous TLR3 ligands in the valvular leaflets may promote the generation of osteoblast-like cells through enhanced type I IFN signaling.

METHODS

Human valvular interstitial cells isolated from aortic valves were challenged with mechanical strain or synthetic TLR3 agonists and analyzed for bone formation, gene expression profiles, and IFN signaling pathways. Different inhibitors were used to delineate the engaged signaling pathways. Moreover, we screened a variety of potential lipids and proteoglycans known to accumulate in CAVD lesions as potential TLR3 ligands. Ligand-receptor interactions were characterized by in silico modeling and verified through immunoprecipitation experiments. Biglycan (Bgn), Tlr3, and IFN-α/β receptor alpha chain (Ifnar1)-deficient mice and a specific zebrafish model were used to study the implication of the biglycan (BGN)-TLR3-IFN axis in both CAVD and bone formation in vivo. Two large-scale cohorts (GERA [Genetic Epidemiology Research on Adult Health and Aging], n=55 192 with 3469 aortic stenosis cases; UK Biobank, n=257 231 with 2213 aortic stenosis cases) were examined for genetic variation at genes implicated in BGN-TLR3-IFN signaling associating with CAVD in humans.

RESULTS

Here, we identify TLR3 as a central molecular regulator of calcification in valvular interstitial cells and unravel BGN as a new endogenous agonist of TLR3. Posttranslational BGN maturation by xylosyltransferase 1 (XYLT1) is required for TLR3 activation. Moreover, BGN induces the transdifferentiation of valvular interstitial cells into bone-forming osteoblasts through the TLR3-dependent induction of type I IFNs. It is intriguing that Bgn-/-, Tlr3-/-, and Ifnar1-/- mice are protected against CAVD and display impaired bone formation. Meta-analysis of 2 large-scale cohorts with >300 000 individuals reveals that genetic variation at loci relevant to the XYLT1-BGN-TLR3-interferon-α/β receptor alpha chain (IFNAR) 1 pathway is associated with CAVD in humans.

CONCLUSIONS

This study identifies the BGN-TLR3-IFNAR1 axis as an evolutionarily conserved pathway governing calcification of the aortic valve and reveals a potential therapeutic target to prevent CAVD.

A snapshot on HIV-1 evolution through the identification of phylogenetic-specific properties of HIV-1 integrases M/O

Transmissions of simian viruses to humans has originated the different groups of HIV-1. We recently identified a functional motif (CLA), in the C-terminal domain of the integrase, essential for integration in HIV-1 group M. Here, we found that the motif is instead dispensable in group O isolates, because of the presence, in the N-terminal domain of HIV-1 O of a specific sequence, Q7G27P41H44, that we define as the NOG motif. Alterations of reverse transcription and of 3' processing observed by mutating the CLA motif of IN M are fully rescued to wt levels by inserting the sequence of the NOG motif in the N-ter of the protein. These results indicate that the two motifs (CLA and NOG) functionally complement each other and a working model accounting for these observations is proposed. The establishment of these two alternative motifs seems to be due to the different phylogenetic origin and history of these two groups. Indeed, the NOG motif is already present in the ancestor of group O (SIVgor) while it is absent from SIVcpzPtt, the ancestor of group M. The CLA motif, instead, seems to have emerged after SIVcpzPtt has been transferred to humans, since no conservation is found at the same positions in these simian viruses. These results show the existence of two-group specific motifs in HIV-1 M and O integrases. In each group, only one of the motifs is functional, potentially leading the other motif to diverge from its original function and, in an evolutionary perspective, assist other functions of the protein, further increasing HIV genetic diversity.

The HIV-1 Integrase C-Terminal Domain Induces TAR RNA Structural Changes Promoting Tat Binding

Recent evidence indicates that the HIV-1 Integrase (IN) binds the viral genomic RNA (gRNA), playing a critical role in the morphogenesis of the viral particle and in the stability of the gRNA once in the host cell. By combining biophysical, molecular biology, and biochemical approaches, we found that the 18-residues flexible C-terminal tail of IN acts as a sensor of the peculiar apical structure of the trans-activation response element RNA (TAR), interacting with its hexaloop. We show that the binding of the whole IN C-terminal domain modifies TAR structure, exposing critical nucleotides. These modifications favour the subsequent binding of the HIV transcriptional trans-activator Tat to TAR, finally displacing IN from TAR. Based on these results, we propose that IN assists the binding of Tat to TAR RNA. This working model provides a mechanistic sketch accounting for the emerging role of IN in the early stages of proviral transcription and could help in the design of anti-HIV-1 therapeutics against this new target of the viral infectious cycle.

Histological validation of cardiac 99mTc-DPD uptake in patients with cardiac transthyretin amyloidosis

Background

Cardiac transthyretin (ATTR) amyloidosis is a progressive and fatal disease caused by the extracellular deposition of misfolded ATTR protein in the myocardium. In an era where new therapies are rapidly emerging, development of non-invasive imaging modalities to quantify amyloid burden over time is of utmost importance. Although endomyocardial biopsy (EMB) remains the gold standard in amyloid detection and typing, 99mTc-DPD scintigraphy is a widely available and accurate tool for non-invasive diagnosis of cardiac ATTR amyloidosis. However, it remains to be determined whether the degree of cardiac 99mTc-DPD uptake correlates with the histological amyloid infiltration on EMB – thus, justifying 99mTc-DPD scintigraphy as a disease monitoring tool.

Aim

This single-centre observational study aimed to compare the extent of histologic amyloid burden on EMB with the quantification of cardiac 99mTc-DPD uptake on scintigraphic planar images and SPECT/CT acquisitions in cardiac ATTR amyloidosis.

Methods

26 patients with cardiac ATTR amyloidosis were enrolled. Patients were included in case of (1) EMB-proven ATTR amyloidosis and (2) availability of 99mTc-DPD scintigraphy (reference activity: 550 MBq). Visual interpretation using the Perugini score, quantitative analysis of cardiac 99mTc-DPD uptake by planar whole-body imaging and SPECT/CT using regions of interest (ROI) were performed, and heart to whole-body ratio (H/WB) was measured. Histological amyloid load was quantified as percentage of the analysed myocardial tissue using Sulfated Alcyan Blue staining and the Fiji-ImageJ programme. Pearson's and Spearman's correlation were used for correlation analysis and assessment of agreement.

Results

ATTR patients had a median age of 77 [73–79] years and were predominantly male (85%). An abnormal Perugini score (i.e. 2 or 3) was present in 25 patients (96%), whereas 1 patient was assigned Perugini score 1 (4%). Increased cardiac tracer uptake was documented in all patients, both on 99mTc-DPD planar scintigraphy (ROImean 129±37) and SPECT/CT (ROImean 369±142). Histologic amyloid burden on EMB was 32±19% on average. It significantly correlated with Perugini score (r=0.56 p=0.003), as well as with cardiac 99mTc-DPD uptake (planar: r=0.54 p=0.006, SPECT/CT: r=0.48 p=0.018) and H/WB (r=0.41 p=0.046).

Conclusion

We have demonstrated a good correlation between histological amyloid infiltration on EMB and cardiac 99mTc-DPD uptake on scintigraphic planar images and SPECT/CT scans, illustrating the potential of 99mTc-DPD scintigraphy to yield reliable quantitative information on cardiac amyloid burden. Further investigations with a larger number of patients are needed to confirm our findings and to implement thresholds in cardiac 99mTc-DPD uptake for being used for guiding disease and therapy management.

Funding Acknowledgement

Type of funding sources: None.

Correlation between invasive and non-invasive quantification of myocardial amyloid load in cardiac transthyretin amyloidosis

Background

Cardiac transthyretin (ATTR) amyloidosis is an infiltrative disease caused by the extracellular deposition of misfolded ATTR protein in the myocardium. Early disease recognition and accurate description of cardiac involvement are fundamental, as cardiac ATTR amyloidosis is associated with poor prognosis. Although endomyocardial biopsy (EMB) remains the gold standard in amyloid detection and typing, non-invasive imaging can provide an accurate diagnostic tool. Bone scintigraphy enables early disease detection with high accuracy. However, it remains to be determined whether the degree of cardiac tracer uptake on bone scintigraphy correlates with the extent of histologic amyloid burden in EMB.

Aim

This single center observational study aimed to compare the histological amyloid load in endomyocardial biopsies with the quantification of cardiac tracer uptake on 99mTechnetium-3,3-diphosphono-1,2-propanodicarboxylic acid (99mTc-DPD) scintigraphy in cardiac ATTR amyloidosis.

Methods

23 patients with cardiac ATTR amyloidosis were enrolled. Diagnosis was obtained with a combination of invasive and non-invasive methods. Perugini score, mean left ventricular tracer uptake (LV uptake) and left ventricular to corpus sterni uptake ratio (LV/CS ratio) on 99mTc-DPD-scintigraphy were measured, while histological amyloid load was quantified as percentage of the analysed myocardial tissue using Sulfated Alcian Blue staining and the Fiji-ImageJ programme. Bivariate correlation and Pearson correlation coefficient were used to study the relationship between EMB and 99mTc-DPD-scintigraphy findings.

Results

We found a statistically significant correlation between histological amyloid load and Perugini score (r=0.47 p=0.02), as well as between Perugini score and LV/CS ratio (r=0.31 p=0.046). Mean LV tracer uptake showed a trend for correlation with histological amyloid load (r=0.37 p=0.08), without reaching statistical significance.

Conclusion

We found a correlation between the extent of histologic amyloid burden in EMB and the degree of cardiac tracer uptake on 99mTc-DPD-scintigraphy. Our results underline the reliability of 99mTc-DPD-scintigraphy as a surrogate of histological amyloid load in the diagnosis of cardiac ATTR amyloidosis. Possible implications for the assessment of prognosis are subject to future studies with a larger number of patients.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Pfizer

High baseline fetuin-A levels are associated with lower atherosclerotic plaque progression as measured by 3D ultrasound

Background and aims

The glycoprotein fetuin-A has anti-inflammatory effects, increases insulin resistance and plays an important role in calcium metabolism. The aim of our study was to assess the predictive value of fetuin-A on atherosclerotic plaque progression in comparison to the established cardiovascular biomarker high sensitivity C-reactive protein (hsCRP).

Methods

In this prospective, single center-, cohort study, we included 194 patients with at least one cardiovascular risk factor or established cardiovascular disease (CVD). Over a period of 4 years, each patient underwent 3D plaque volumetry of the carotid and femoral arteries on a yearly basis. To evaluate the predictive value of biomarkers in terms of plaque progression, the baseline values of fetuin-A and hsCRP were correlated with the plaque progression from baseline to the last follow up visit.

Results

171 patients were included in the final analysis. Baseline fetuin-A levels showed a significant negative correlation with plaque progression (r = -0.244; p = 0.001). In contrast, baseline hsCRP levels showed no correlation with plaque progression (r = 0.096, p = 0.20). In the ROC-analysis, fetuin-A had a significantly better predictive value than hsCRP (fetuin-A AUC 0.67; p = 0.001 vs hsCRP AUC 0.49; p = 0.88) with an optimal cut-off value at 712 μg/ml. In patients with high fetuin A levels (>712 μg/ml), a significantly lower plaque progression was observed compared to the group with low fetuin-A levels <712 μg/ml (high fetuin-A 197 mm³ vs. low fetuin-A 279 mm³; p = 0.01).

Conclusions

Higher fetuin-A levels appear to predict lower atherosclerotic plaque progression in patients with or at risk of cardiovascular disease.

Cardiopulmonary recovery after COVID-19: an observational prospective multicentre trial

BACKGROUND

After the 2002/2003 severe acute respiratory syndrome outbreak, 30% of survivors exhibited persisting structural pulmonary abnormalities. The long-term pulmonary sequelae of coronavirus disease 2019 (COVID-19) are yet unknown, and comprehensive clinical follow-up data are lacking.

METHODS

In this prospective, multicentre, observational study, we systematically evaluated the cardiopulmonary damage in subjects recovering from COVID-19 at 60 and 100 days after confirmed diagnosis. We conducted a detailed questionnaire, clinical examination, laboratory testing, lung function analysis, echocardiography and thoracic low-dose computed tomography (CT).

RESULTS

Data from 145 COVID-19 patients were evaluated, and 41% of all subjects exhibited persistent symptoms 100 days after COVID-19 onset, with dyspnoea being most frequent (36%). Accordingly, patients still displayed an impaired lung function, with a reduced diffusing capacity in 21% of the cohort being the most prominent finding. Cardiac impairment, including a reduced left ventricular function or signs of pulmonary hypertension, was only present in a minority of subjects. CT scans unveiled persisting lung pathologies in 63% of patients, mainly consisting of bilateral ground-glass opacities and/or reticulation in the lower lung lobes, without radiological signs of pulmonary fibrosis. Sequential follow-up evaluations at 60 and 100 days after COVID-19 onset demonstrated a vast improvement of symptoms and CT abnormalities over time.

CONCLUSION

A relevant percentage of post-COVID-19 patients presented with persisting symptoms and lung function impairment along with radiological pulmonary abnormalities >100 days after the diagnosis of COVID-19. However, our results indicate a significant improvement in symptoms and cardiopulmonary status over time.

HIV-1 Capsid Core: A Bullet to the Heart of the Target Cell

The first step of the intracellular phase of retroviral infection is the release of the viral capsid core in the cytoplasm. This structure contains the viral genetic material that will be reverse transcribed and integrated into the genome of infected cells. Up to recent times, the role of the capsid core was considered essentially to protect this genetic material during the earlier phases of this process. However, increasing evidence demonstrates that the permanence inside the cell of the capsid as an intact, or almost intact, structure is longer than thought. This suggests its involvement in more aspects of the infectious cycle than previously foreseen, particularly in the steps of viral genomic material translocation into the nucleus and in the phases preceding integration. During the trip across the infected cell, many host factors are brought to interact with the capsid, some possessing antiviral properties, others, serving as viral cofactors. All these interactions rely on the properties of the unique component of the capsid core, the capsid protein CA. Likely, the drawback of ensuring these multiple functions is the extreme genetic fragility that has been shown to characterize this protein. Here, we recapitulate the busy agenda of an HIV-1 capsid in the infectious process, in particular in the light of the most recent findings.

The haemochromatosis gene Hfe and Kupffer cells control LDL cholesterol homeostasis and impact on atherosclerosis development

AIMS

Imbalances of iron metabolism have been linked to the development of atherosclerosis. However, subjects with hereditary haemochromatosis have a lower prevalence of cardiovascular disease. The aim of our study was to understand the underlying mechanisms by combining data from genome-wide association study analyses in humans, CRISPR/Cas9 genome editing, and loss-of-function studies in mice.

METHODS AND RESULTS

Our analysis of the Global Lipids Genetics Consortium (GLGC) dataset revealed that single nucleotide polymorphisms (SNPs) in the haemochromatosis gene HFE associate with reduced low-density lipoprotein cholesterol (LDL-C) in human plasma. The LDL-C lowering effect could be phenocopied in dyslipidaemic ApoE-/- mice lacking Hfe, which translated into reduced atherosclerosis burden. Mechanistically, we identified HFE as a negative regulator of LDL receptor expression in hepatocytes. Moreover, we uncovered liver-resident Kupffer cells (KCs) as central players in cholesterol homeostasis as they were found to acquire and transfer LDL-derived cholesterol to hepatocytes in an Abca1-dependent fashion, which is controlled by iron availability.

CONCLUSION

Our results disentangle novel regulatory interactions between iron metabolism, KC biology and cholesterol homeostasis which are promising targets for treating dyslipidaemia but also provide a mechanistic explanation for reduced cardiovascular morbidity in subjects with haemochromatosis.

NGAL Correlates with Femoral and Carotid Plaque Volume Assessed by Sonographic 3D Plaque Volumetry

Background/Objectives: Inflammation represents a cornerstone in the development of atherosclerosis and early detection is essential to avoid cardiovascular events. Biomarkers like interleukin-1 beta, interleukin-6, or high sensitivity CRP (hs-CRP) have been investigated intensively in this field. Since they have several limitations, additional biomarkers are needed for cardiovascular risk stratification. The acute phase protein, neutrophil gelatinase-associated lipocalin (NGAL), modulates inflammation and is elevated in cardiovascular disease (CVD). Moreover, it contributes to plaque destabilization. Methods: In this prospective, single-center study, we included 323 asymptomatic patients with at least one cardiovascular risk factor or established CVD. NGAL levels were measured in plasma samples using a commercially available ELISA. Carotid, femoral, and total atherosclerotic plaque volumes (PV) were measured using a 3D ultrasound system (Philips iU22). Patients were separated into a low (n = 243) and high (n = 80) total PV group. Results: NGAL was significantly higher in patients with high total PV versus patients with low total PV. The NGAL amplitude for the prediction of high total PV was significantly higher when compared with hs-CRP. A high predictive value could also be observed for patients without established CVD. Conclusion: NGAL seems to be a promising biomarker for the identification of asymptomatic patients with atherosclerotic disease.

Early onset of menopause is associated with increased peripheral atherosclerotic plaque volume and progression

BACKGROUND AND AIMS

Cardiovascular disease (CVD) is the leading cause of death in western countries. One risk factor unique to women is the menopausal status. The aim of this study was to analyse the influence of the onset of menopause (MP) on the extent and progression of atherosclerotic plaque volume (PV).

METHODS

Postmenopausal women with at least one cardiovascular risk factor (CVRF) but without established CVD were included. Quantification of PV was performed in peripheral arteries using a three - dimensional (3D) ultrasound (US) technique. Follow-up examination to assess PV progression was performed after 19 (±8) months.

RESULTS

110 consecutive postmenopausal women (mean age 65.5) were included. Females with an earlier onset of MP (<45 years) had a significantly higher PV than those with an intermediate (45-52 years) or later onset of menopause (>52 years), irrespective of other CVRF (244 mm³ vs. 193 mm³ vs. 73 mm³, respectively, p = 0.023). In addition, women with an earlier onset of MP had a higher PV progression compared to women with an intermediate or late onset (40 mm³ vs. 35 mm³ vs. 8.5 mm³; p = 0.002, respectively). Moreover, these results were confirmed in multivariate regression, where only onset of MP (OR 0.88; 95%CI 0.81-0.96; p = 0.004) and age (OR 1.06; 95%CI 1.08-1.13; p = 0.025) were significant predictors for a higher atherosclerotic progression.

CONCLUSIONS

An earlier onset of MP was associated with an increase in atherosclerotic PV and accelerated progression, independent of other CVRF.

Shock Wave Therapy Improves Cardiac Function in a Model of Chronic Ischemic Heart Failure: Evidence for a Mechanism Involving VEGF Signaling and the Extracellular Matrix

Background

Mechanical stimulation of acute ischemic myocardium by shock wave therapy (SWT) is known to improve cardiac function by induction of angiogenesis. However, SWT in chronic heart failure is poorly understood. We aimed to study whether mechanical stimulation upon SWT improves heart function in chronic ischemic heart failure by induction of angiogenesis and postnatal vasculogenesis and to dissect underlying mechanisms.

Methods and Results

SWT was applied in a mouse model of chronic myocardial ischemia. To study effects of SWT on postnatal vasculogenesis, wild‐type mice received bone marrow transplantation from green fluorescence protein donor mice. Underlying mechanisms were elucidated in vitro in endothelial cells and murine aortic rings. Echocardiography and pressure/volume measurements revealed improved left ventricular ejection fraction, myocardial contractility, and diastolic function and decreased myocardial fibrosis after treatment. Concomitantly, numbers of capillaries and arterioles were increased. SWT resulted in enhanced expression of the chemoattractant stromal cell–derived factor 1 in ischemic myocardium and serum. Treatment induced recruitment of bone marrow–derived endothelial cells to the site of injury. In vitro, SWT resulted in endothelial cell proliferation, enhanced survival, and capillary sprouting. The effects were vascular endothelial growth factor receptor 2 and heparan sulfate proteoglycan dependent.

Conclusions

SWT positively affects heart function in chronic ischemic heart failure by induction of angiogenesis and postnatal vasculogenesis. SWT upregulated pivotal angiogenic and vasculogenic factors in the myocardium in vivo and induced proliferative and anti‐apoptotic effects on endothelial cells in vitro. Mechanistically, these effects depend on vascular endothelial growth factor signaling and heparan sulfate proteoglycans. SWT is a promising treatment option for regeneration of ischemic myocardium.

Gene therapy with the angiogenic neuropeptide secretoneurin ameliorates experimental diabetic neuropathy

The pathogenesis of diabetic neuropathy remains enigmatic. Damage to the vasa nervorum may be responsible for this disorder. Recently, we showed that secretoneurin (SN) induces angiogenesis in hindlimb and myocardial ischemia. Moreover, beneficial effects were observed in wound healing. We therefore hypothesized that SN therapy may ameliorate diabetic neuropathy. We used db/db mice as animal model for neuropathy. Gene therapy was accomplished by intramuscular injection of SN plasmid along the sciatic nerve. Sciatic nerve motor and sensory conduction velocities were then measured for 9 wk. Nerve conduction velocities showed normal values in heterozygous mice for the observational period, but were severely reduced in homozygous mice in which velocities were significantly improved by SN, but not by control plasmid gene therapy. The reaction time in the tail-flick test improved significantly in SN-treated animals. The induction of growth of vasa nervorum seems to be part of the underlying mechanism. In addition, SN positively affected Schwann cell function in vitro and induced activation of important signaling pathways. Our observations suggest that SN exerts beneficial effects on nerve function in vivo and on Schwann cells in vitro. It therefore may be a promising treatment option for diabetic neuropathy.-Theurl, M., Lener, D., Albrecht-Schgoer, K., Beer, A., Schgoer, W., Liu, Y., Stanzl, U., Fischer-Colbrie, R., Kirchmair, R. Gene therapy with the angiogenic neuropeptide secretoneurin ameliorates experimental diabetic neuropathy.

Sitagliptin Accelerates Endothelial Regeneration after Vascular Injury Independent from GLP1 Receptor Signaling

INTRODUCTION

DPP4 inhibitors (gliptins) are commonly used antidiabetic drugs for the treatment of type 2 diabetes. Gliptins also act in a glucose-independent manner and show vasoregenerative effects. We have shown that gliptins can remarkably accelerate vascular healing after vascular injury. However, the underlying mechanisms remain unclear. Here, we examined potential signaling pathways linking gliptins to enhanced endothelial regeneration.

METHODS AND RESULTS

We used wild-type and GLP1 receptor knockout (Glp1r-/-) mice to investigate the underlying mechanisms of gliptin-induced reendothelialization. The prototype DPP4 inhibitor sitagliptin accelerated endothelial healing in both animal models. Improved endothelial growth was associated with gliptin-mediated progenitor cell recruitment into the diseased vascular wall via the SDF1-CXCR4 axis independent of GLP1R-dependent signaling pathways. Furthermore, SDF1 showed direct proproliferative effects on endothelial cells. Excessive neointimal formation was not observed in gliptin- or placebo-treated Glp1r-/- mice.

CONCLUSION

We identified the SDF1-CXCR4 axis as a crucial signaling pathway for endothelial regeneration after acute vascular injury. Furthermore, SDF1 can directly increase endothelial cell proliferation. Gliptin-mediated potentiation of endothelial regeneration was preserved in Glp1r-/- animals. Thus, gliptin-mediated endothelial regeneration proceeds through SDF-1/CXCR4 in a GLP1R-independent manner after acute vascular injury.

Proceedings of the Frontiers of Retrovirology Conference 2016

Oral presentations

Session 1: Entry & uncoating

O1 Host cell polo-like kinases (PLKs) promote early prototype foamy virus (PFV) replication

Irena Zurnic, Sylvia Hütter, Ute Lehmann, Nicole Stanke, Juliane Reh, Tobias Kern, Fabian Lindel, Gesche Gerresheim, Martin Hamann, Erik Müllers, Paul Lesbats, Peter Cherepanov, Erik Serrao, Alan Engelman, Dirk Lindemann

O2 A novel entry/uncoating assay reveals the presence of at least two species of viral capsids during synchronized HIV-1 infection

Claire Da Silva Santos, Kevin Tartour, Andrea Cimarelli

O3 Dynamics of nuclear envelope association and nuclear import of HIV-1 complexes

Rya Burdick, Jianbo Chen, Jaya Sastri, Wei-Shau Hu, Vinay Pathak

O4 Human papillomavirus protein E4 potently enhances the susceptibility to HIV infection

Oliver T. Keppler

Session 2: Reverse transcription & integration

O5 Structure and function of HIV-1 integrase post translational modifications

Karine Pradeau, Sylvia Eiler, Nicolas Levy, Sarah Lennon, Sarah Cianferani, Stéphane Emiliani, Marc Ruff

O6 Regulation of retroviral integration by RNA polymerase II associated factors and chromatin structure

Vincent Parissi

Session 3: Transcription and latency

O7 A novel single-cell analysis pipeline to identify specific biomarkers of HIV permissiveness

Sylvie Rato, Antonio Rausell, Miguel Munoz, Amalio Telenti, Angela Ciuffi

O8 A capsid-dependent integration program linking T cell activation to HIV-1 gene expression

Alexander Zhyvoloup, Anat Melamed, Ian Anderson, Delphine Planas, Janos Kriston-Vizi, Robin Ketteler, Chen-Hsuin Lee, Andy Merritt, Petronela Ancuta, Charles Bangham, Ariberto Fassati

O9 Characterisation of new RNA polymerase III and RNA polymerase II transcriptional promoters in the Bovine Leukemia Virus genome

Anthony Rodari, Benoit Van Driessche, Mathilde Galais, Nadége Delacourt, Sylvain Fauquenoy, Caroline Vanhulle, Anna Kula, Arsène Burny, Olivier Rohr, Carine Van Lint

O10 Tissue-specific dendritic cells differentially modulate latent HIV-1 reservoirs

Thijs van Montfort, Renee van der Sluis, Dave Speijer, Ben Berkhout

Session 4: RNA trafficking & packaging

O11 A novel cis-acting element affecting HIV replication

Bo Meng, Andrzej Rutkowski, Neil Berry, Lars Dölken, Andrew Lever

O12 Tolerance of HIV’s late gene expression towards stepwise codon adaptation

Thomas Schuster, Benedikt Asbach, Ralf Wagner

Session 5: Assembly & release

O13 Importance of the tax-inducible actin-bundling protein fascin for transmission of human T cell leukemia virus Type 1 (HTLV-1)

Christine Gross, Veit Wiesmann, Martina Kalmer, Thomas Wittenberg, Jan Gettemans, Andrea K. Thoma-Kress

O14 Lentiviral nef proteins antagonize TIM-mediated inhibition of viral release

Minghua Li, Eric O. Freed, Shan-Lu Liu

Session 6: Pathogenesis & evolution

O15 SEVI and semen prolong the half-life of HIV-1

Janis Müller, Jan Münch

O16 CD169⁺ macrophages mediate retrovirus trans-infection of permissive lymphocytes to establish infection in vivo

Xaver Sewald, Pradeep Uchil, Mark Ladinsky, Jagadish Beloor, Ruoxi Pi, Christin Herrmann, Nasim Motamedi, Thomas Murooka, Michael Brehm, Dale Greiner, Thorsten Mempel, Pamela Bjorkman, Priti Kumar, Walther Mothes

O17 Efficient replication of a vpu containing SIVagm construct in African Green Monkeys requires an HIV-1 nef gene

Simone Joas, Erica Parrish, Clement Wesley Gnanadurai, Edina Lump, Christina M. Stürzel, Nicholas F. Parrish, Ulrike Sauermann, Katharina Töpfer, Tina Schultheiss, Steven Bosinger, Guido Silvestri, Cristian Apetrei, Nicholas Huot, Michaela Müller-Trutwin, Daniel Sauter, Beatrice H. Hahn, Christiane Stahl-Hennig, Frank Kirchhoff

O18 Reprogramming initiates mobilization of endogenous mutagenic LINE-1, Alu and SVA retrotransposons in human induced pluripotent stem cells with consequences for host gene expression

Gerald Schumann, Sabine Jung-Klawitter, Nina V. Fuchs, Kyle R. Upton, Martin Muñoz-Lopez, Ruchi Shukla, Jichang Wang, Marta Garcia-Canadas, Cesar Lopez-Ruiz, Daniel J. Gerhardt, Attila Sebe, Ivana Grabundzija, Patricia Gerdes, Sylvia Merkert, Andres Pulgarin, Anja Bock, Ulrike Held, Anett Witthuhn, Alexandra Haase, Ernst J. Wolvetang, Ulrich Martin, Zoltán Ivics, Zsuzsanna Izsvák, J. Garcia-Perez, Geoffrey J. Faulkner

O19 NF-κB activation induces expression of human endogenous retrovirus and particle production

Tara Hurst, Aris Katzourakis, Gkikas Magiorkinis

Session 7a and b: Innate sensing & intrinsic immunity

O20 Identification of the phosphatase acting on T592 in SAMHD1 during M/G₁ transition

Kerstin Schott, Rita Derua, Janna Seifried, Andreas Reuter, Heike Schmitz, Christiane Tondera, Alberto Brandariz-Nuñez, Felipe Diaz-Griffero, Veerle Janssens, Renate König

O21 Vpx overcomes a SAMHD1-independent block to HIV reverse transcription that is specific to resting CD4 T cells

Hanna-Mari Baldauf, Lena Stegmann, Sarah-Marie Schwarz, Maud Trotard, Margarethe Martin, Gina Lenzi, Manja Burggraf, Xiaoyu Pan, Oliver I. Fregoso, Efrem S. Lim, Libin Abraham, Elina Erikson, Laura Nguyen, Ina Ambiel, Frank Rutsch, Renate König, Baek Kim, Michael Emerman, Oliver T. Fackler, Oliver T. Keppler

O22 The role of SAMHD1 in antiviral restriction and immune sensing in the mouse

Sabine Wittmann, Rayk Behrendt, Bianca Volkmann, Kristin Eissmann, Thomas Gramberg

O23 T cells expressing reduced restriction factors are preferentially infected in therapy naïve HIV-1 patients

Sebastian Bolduan, Herwig Koppensteiner, Stefanie Regensburg, Ruth Brack-Werner, Rika Draenert, Michael Schindler

O24 cGAS-mediated innate immunity spreads through HIV-1 env-induced membrane fusion sites from infected to uninfected primary HIV-1 target cells

Aurélie Ducroux, Shuting Xu, Aparna Ponnurangam, Sergej Franz, Angelina Malassa, Ellen Ewald, Christine Goffinet

O25 Perturbation of innate RNA and DNA sensing by human T cell leukemia virus type 1 oncoproteins

Sin-Yee Fung, Ching-Ping Chan, Chun-Kit Yuen, Kin-Hang Kok, Chin-Ping Chan, Dong-Yan Jin

O26 Induction and anti-viral activity of Interferon α subtypes in HIV-1 infection

Ulf Dittmer

O27 Vpu-mediated counteraction of tetherin is a major determinant of HIV-1 interferon resistance

Dorota Kmiec, Shilpa Iyer, Christina Stürzel, Daniel Sauter, Beatrice Hahn, Frank Kirchhoff

O28 DNA repair protein Rad18 restricts HIV-1 and LINE-1 life cycle

Yasuo Ariumi, Mariko Yasuda-Inoue, Koudai Kawano, Satoshi Tateishi, Priscilla Turelli

O29 Natural mutations in IFITM3 allow escape from post-translational regulation and toggle antiviral specificity

Alex Compton, Nicolas Roy, Françoise Porrot, Anne Billet, Nicoletta Casartelli, Jacob Yount, Chen Liang, Oliver Schwartz

Session 8: Adaptive immunity & immune evasion

O30 Observing evolution in HIV-1 infection: phylogenetics and mutant selection windows to infer the influence of the autologous antibody response on the viral quasispecies

Carsten Magnus, Lucia Reh, Penny Moore, Therese Uhr, Jacqueline Weber, Lynn Morris, Alexandra Trkola

O31 Dose and subtype specific analyses of the anti-HIV effects of IFN-alpha family members

Rashel V. Grindberg, Erika Schlaepfer, Gideon Schreiber, Viviana Simon, Roberto F. Speck

Session 9: Novel antiviral strategies

O32 LEDGIN-mediated inhibition of the integrase-LEDGF/p75 interaction reduces reactivation of residual latent HIV

Zeger Debyser, Lenard Vranckx, Jonas Demeulemeester, Suha Saleh, Eric Verdin, Anna Cereseto, Frauke Christ, Rik Gijsbers

O33 NKG2D-mediated clearance of reactivated viral reservoirs by natural killer cells

O34 Inhibition of HIV reactivation in brain cells by AAV-mediated delivery of CRISPR/Cas9

O35 CRISPR-Cas9 as antiviral: potent HIV-1 inhibition, but rapid virus escape and the subsequent design of escape-proof antiviral strategies

Ben Berkhout, Gang Wang, Na Zhao, Atze T. Das

Session 10: Recent advances in HIV vaccine development

O36 Priming with a potent HIV-1 DNA vaccine frames the quality of T cell and antibody responses prior to a poxvirus and protein boost

Benedikt Asbach, Josef Köstler, Beatriz Perdiguero, Mariano Esteban, Bertram L. Jacobs, David C. Montefiori, Celia C. LaBranche, Nicole L. Yates, Georgia D. Tomaras, Guido Ferrari, Kathryn E. Foulds, Mario Roederer, Gary Landucci, Donald N. Forthal, Michael S. Seaman, Natalie Hawkins, Steven G. Self, Sanjay Phogat, James Tartaglia, Susan W. Barnett, Brian Burke, Anthony D. Cristillo, Song Ding, Jonathan L. Heeney, Giuseppe Pantaleo, Ralf Wagner

O37 Passive immunisation with a neutralising antibody against HIV-1 Env prevents infection of the first cells in a mucosal challenge rhesus monkey model

Christiane Stahl-Hennig, Viktoria Stab, Armin Ensser, Ulrike Sauermann, Bettina Tippler, Dennis Burton, Matthias Tenbusch, Klaus Überla

O38 HIV antibody Fc-glycoforms drive B cell affinity maturation

Galit Alter, Giuseppe Lofano, Anne-Sophie Dugast, Viraj Kulkarni, Todd Suscovich

Poster presentations

Topic 1: Entry & uncoating

P1 Dynein light chain is required for murine leukemia virus infection

Tatiana Opazo, Felipe Barraza, Diego Herrera, Andrea Garces, Tomas Schwenke, Diego Tapia, Jorge Cancino, Gloria Arriagada

P2 Peptide paratope mimics of the broadly neutralising HIV-1 antibody b12

Christina Haußner, Dominik Damm, Anette Rohrhofer, Barbara Schmidt, Jutta Eichler

P3 Investigating cellular pathways involved in the transmission of HIV-1 between dendritic cells and T cells using RNAi screening techniques

Rebecca Midgley, James Wheeldon, Vincent Piguet

P4 Co-receptor tropism in HIV-1, HIV-2 monotypic and dual infections

Priyanka Khopkar, Megha Rohamare, Smita Kulkarni

P5 Characterisation of the role of CIB1 and CIB2 as HIV-1 helper factors

Ana Godinho-Santos, Allan Hance, Joao Goncalves, Fabrizio Mammano

P6 Buffering deleterious polymorphisms in the highly constrained C2 region of HIV-1 envelope by the flexible V3 domain

Romain Gasser, Meriem Hamoudi, Martina Pellicciotta, Zhicheng Zhou, Clara Visdeloup, Philippe Colin, Martine Braibant, Bernard Lagane, Matteo Negroni

P7 Entry inhibition of HERV-K(HML-2) by an Env-IgG fusion protein

Jula Wamara, Norbert Bannert

Topic 2: Reverse transcription & integration

P8 The R263K/H51Y resistance substitutions in HIV integrase decreases levels of integrated HIV DNA over time

Thibault Mesplede, Nathan Osman, Kaitlin Anstett, Jiaming Calvin Liang, Hanh Thi Pham, Mark Wainberg

P9 The Retrovirus Integration Database (RID)

Wei Shao, Jigui Shan, Mary Kearney, Xiaolin Wu, Frank Maldarelli, John Mellors, Brian Luke, John Coffin, Stephen Hughes

P10 The small molecule 3G11 inhibits HIV-1 reverse transcription

Thomas Fricke, Silvana Opp, Caitlin Shepard, Dmitri Ivanov, Baek Kim, Jose Valle-Casuso, Felipe Diaz-Griffero

P11 Dual and opposite regulation of HIV-1 integration by hRAD51: impact on therapeutical approaches using homologous DNA repair modulators

Vincent Parissi

P12 A flexible motif essential for integration by HIV-1 integrase

Marine Kanja, Pierre Cappy, Matteo Negroni, Daniela Lener

P13 Interaction between HIV-1 integrase and the host protein Ku70: identification of the binding site and study of the influence on integrase-proteasome interplay

Ekaterina Knyazhanskaya, Andrey Anisenko, Timofey Zatsepin, Marina Gottikh

P14 Normalisation based method for deep sequencing of somatic retroelement integrations in human genome

Alexander Komkov, Anastasia Minervina, Gaiaz Nugmanov, Vadim Nazarov, Konstantin Khodosevich, Ilgar Mamedov, Yuri Lebedev

Topic 3: Transcription and latency

P15 BCA2/RABRING7 restricts HIV-1 transcription by preventing the nuclear translocation of NF-κB

Marta Colomer-Lluch, Ruth Serra-Moreno

P16 MATR3 post-transcriptional regulation of HIV-1 transcription during latency

Ambra Sarracino, Anna Kula, Lavina Gharu, Alexander Pasternak, Carine Van Lint, Alessandro Marcello

P17 HIV-1 tat intersects the SUMO pathway to regulate HIV-1 promoter activity

Ann Marie McCartin, Anurag Kulkarni, Valentin Le Douce, Virginie Gautier

P18 Conservation in HIV-1 Vpr guides tertiary gRNA folding and alternative splicing

Ann Baeyens, Evelien Naessens, Anouk Van Nuffel, Karin Weening, Anne-Marie Reilly, Eva Claeys, Wim Trypsteen, Linos Vandekerckhove, Sven Eyckerman, Kris Gevaert, Bruno Verhasselt

P19 The majority of reactivatable latent HIV are genetically distinct

Hoi Ping Mok, Nicholas Norton, Axel Fun, Jack Hirst, Mark Wills, Andrew Lever

P20 Do mutations in the tat exonic splice enhancer contribute to HIV-1 latency?

Nicholas Norton, Hoi Ping Mok, Jack Hirst, Andrew Lever

P21 Culture-to-Ct: A fast and direct RT-qPCR HIV gene reactivation screening method using primary T cell culture

Valentin Le Douce, Ann Marie McCartin, Virginie Gautier

P22 A novel approach to define populations of early silenced proviruses

Dalibor Miklik, Filip Senigl, Jiri Hejnar

Topic 4: RNA trafficking & packaging

P23 Functional analysis of the structure and conformation of HIV-1 genome RNA DIS

Jun-ichi Sakuragi, Sayuri Sakuragi, Masaru Yokoyama, Tatsuo Shioda, Hironori Sato

P24 Regulation of foamy viral env splicing controls gag and pol expression

Jochen Bodem, Rebecca Moschall, Sarah Denk, Steffen Erkelenz, Christian Schenk, Heiner Schaal

Topic 5: Assembly & release

P25 Transfer of HTLV-1 p8 to target T cells depends on VASP: a novel interaction partner of p8

Norbert Donhauser, Ellen Socher, Sebastian Millen, Heinrich Sticht, Andrea K. Thoma-Kress

P26 COL4A1 and COL4A2 are novel HTLV-1 tax targets with a putative role in virus transmission

Christine Gross, Sebastian Millen, Melanie Mann, Klaus Überla, Andrea K. Thoma-Kress

P27 The C terminus of foamy virus gag protein is required for particle formation, and virus budding: starting assembly at the C terminus?

Guochao Wei, Matthew J. Betts, Yang Liu, Timo Kehl, Robert B. Russell, Martin Löchelt

P28 Generation of an antigen-capture ELISA and analysis of Rec and Staufen-1 effects on HERV-K(HML-2) virus particle production

Oliver Hohn, Saeed Mostafa, Kirsten Hanke, Stephen Norley, Norbert Bannert

P29 Antagonism of BST-2/tetherin is a conserved function of primary HIV-2 Env glycoproteins

Chia-Yen Chen, Masashi Shingai, Pedro Borrego, Nuno Taveira, Klaus Strebel

P30 Mutations in the packaging signal region of the HIV-1 genome cause a late domain mutant phenotype

Chris Hellmund, Bo Meng, Andrew Lever

P31 p6 regulates membrane association of HIV-1 gag

Melanie Friedrich, Friedrich Hahn, Christian Setz, Pia Rauch, Kirsten Fraedrich, Alina Matthaei, Petra Henklein, Maximilian Traxdorf, Torgils Fossen, Ulrich Schubert

Topic 6: Pathogenesis & evolution

P32 Molecular and structural basis of protein evolution during viral adaptation

Aya Khwaja, Meytal Galilee, Akram Alian

P33 HIV-1 enhancement and neutralisation by soluble gp120 and its role for the selection of the R5-tropic “best fit”

Birco Schwalbe, Heiko Hauser, Michael Schreiber

P34 An insertion of seven amino acids in the Env cytoplasmic tail of Human Immunodeficiency Virus type 2 (HIV-2) selected during disease progression enhances viral replication

François Dufrasne, Mara Lucchetti, Patrick Goubau, Jean Ruelle

P35 Cell-associated HIV-1 unspliced to multiply spliced RNA ratio at 12 weeks ART correlates with markers of immune activation and apoptosis and predicts the CD4 T-cell count at 96 weeks ART

Mirte Scherpenisse, Ben Berkhout, Alexander Pasternak

P36 Faster progression in non-B subtype HIV-1-infected patients than Korean subclade of subtype B is accompanied by higher variation and no induction of gross deletion in non-B nef gene by Korean red ginseng treatment

Young-Keol Cho, Jungeun Kim, Daeun Jeong

P37 Aberrant expression of ERVWE1 endogenous retrovirus and overexpression of TET dioxygenases are characteristic features of seminoma

Katerina Trejbalova, Martina Benesova, Dana Kucerova, Zdenka Vernerova, Rachel Amouroux, Petra Hajkova, Jiri Hejnar

P38 Life history of the oldest lentivirus: characterisation of ELVgv integrations and the TRIM5 selection pattern in dermoptera

Daniel Elleder, Tomas Hron, Helena Farkasova, Abinash Padhi, Jan Paces

P39 Characterisation of a highly divergent endogenous retrovirus in the equine germ line

Henan Zhu, Robert Gifford, Pablo Murcia

P40 The emergence of pandemic retroviral infection in small ruminants

Maria Luisa Carrozza, Anna-Maria Niewiadomska, Maurizio Mazzei, Mounir Abi-Said, Joseph Hughes, Stéphane Hué, Robert Gifford

P41 Near full-length genome (NFLG) Characterisation of HIV-1 subtype B identified in South Africa

Adetayo Obasa, Graeme Jacobs, Susan Engelbrecht

P42 Acquisition of Vpu-mediated tetherin antagonism by an HIV-1 group O strain

Katharina Mack, Kathrin Starz, Daniel Sauter, Matthias Geyer, Frederic Bibollet-Ruche, Christina Stürzel, Marie Leoz, Jean Christophe Plantier, Beatrice H. Hahn, Frank Kirchhoff

P43 The human endogenous retrovirus type K is involved in cancer stem cell markers expression and in human melanoma malignancy

Ayele Argaw-Denboba, Emanuela Balestrieri, Annalucia Serafino, Ilaria Bucci, Chiara Cipriani, Corrado Spadafora, Paolo Sinibaldi-Vallebona, Claudia Matteucci

P44 Natural infection of Indian non-human primates by unique lentiviruses

S. Nandi Jayashree, Ujjwal Neogi, Anil K. Chhangani, Shravan Sing Rathore, Bajrang R. J. Mathur

P45 Free cervical cancer screening among HIV-positive women receiving antiretroviral treatment in Nigeria

Adeyemi Abati

P46 Molecular evolutionary status of feline immunodeficiency virus in Turkey

B. Taylan Koç, Tuba Çiğdem Oğuzoğlu

Topic 7: Innate sensing & intrinsic immunity

P47 Cell-to-cell contact with HTLV-1-infected T cells reduces dendritic cell immune functions and contributes to infection in trans.

Takatoshi Shimauchi, Stephan Caucheteux, Jocelyn Turpin, Katja Finsterbusch, Charles Bangham, Yoshiki Tokura, Vincent Piguet

P48 Deciphering the mechanisms of HIV-1 exacerbation induced by Mycobacterium tuberculosis in monocytes/macrophages

Shanti Souriant, Luciana Balboa, Karine Pingris, Denise Kviatcowsky, Brigitte Raynaud-Messina, Céline Cougoule, Ingrid Mercier, Marcelo Kuroda, Pablo González-Montaner, Sandra Inwentarz, Eduardo Jose Moraña, Maria del Carmen Sasiain, Olivier Neyrolles, Isabelle Maridonneau-Parini, Geanncarlo Lugo-Villarino, Christel Vérollet

P49 The SAMHD1-mediated inhibition of LINE-1 retroelements is regulated by phosphorylation

Alexandra Herrmann, Sabine Wittmann, Caitlin Shepard, Dominique Thomas, Nerea Ferreirós Bouzas, Baek Kim, Thomas Gramberg

P50 Activities of nuclear envelope protein SUN2 in HIV infection

Xavier Lahaye, Anvita Bhargava, Takeshi Satoh, Matteo Gentili, Silvia Cerboni, Aymeric Silvin, Cécile Conrad, Hakim Ahmed-Belkacem, Elisa C. Rodriguez, Jean-François Guichou, Nathalie Bosquet, Matthieu Piel, Roger Le Grand, Megan King, Jean-Michel Pawlotsky, Nicolas Manel

P51 Activation of TLR7/8 with a small molecule agonist induces a novel restriction to HIV-1 infection of monocytes

Henning Hofmann, Benedicte Vanwalscappel, Nicolin Bloch, Nathaniel Landau

P52 Steady state between the DNA polymerase and Rnase H domain activities of reverse transcriptases determines the sensitivity of retroviruses to inhibition by APOBEC3 proteins

Stanislav Indik, Benedikt Hagen

P53 HIV restriction in mature dendritic cells is related to p21 induction and p21-mediated control of the dNTP pool and SAMHD1 activity.

José Carlos Valle-Casuso, Awatef Allouch, Annie David, Françoise Barré-Sinoussi, Michaela Müller-Trutwin, Monsef Benkirane, Gianfranco Pancino, Asier Saez-Cirion

P54 IFITM protens restrict HIV-1 protein synthesis

Wing-Yiu Lee, Chen Liang, Richard Sloan

P55 Characterisation and functional analysis of the novel restriction factor Serinc5

Bianca Schulte, Silvana Opp, Felipe Diaz-Griffero

P56 piRNA sequences are common in Human Endogenous Retroviral Sequences (HERVs): An antiretroviral restriction mechanism?

Jonas Blomberg, Luana Vargiu, Patricia Rodriguez-Tomé, Enzo Tramontano, Göran Sperber

P57 Ferroportin restricts HIV-1 infection in sickle cell disease

Namita Kumari, Tatiana Ammosova, Sharmeen Diaz, Patricia Oneal, Sergei Nekhai

P58 APOBEC3G modulates the response to antiretroviral drugs in humanized mice

Audrey Fahrny, Gustavo Gers-Huber, Annette Audigé, Roberto F. Speck, Anitha Jayaprakash, Ravi Sachidanandam, Matt Hernandez, Marsha Dillon-White, Viviana Simon

P59 High-throughput epigenetic analysis of evolutionarily young endogenous retrovirus presents in the mule deer (Odocoileus hemionus) genome

Tomas Hron, Helena Farkasova, Daniel Elleder

P60 Characterisation of the expression of novel endogenous retroviruses and immune interactions in a macaque model

Neil Berry, Emmanuel Maze, Claire Ham, Neil Almond, Greg Towers, Robert Belshaw

P61 HIV-1 restriction by orthologs of SERINC3 and SERINC5

Patrícia de Sousa-Pereira, Joana Abrantes, Massimo Pizzato, Pedro J. Esteves, Oliver T. Fackler, Oliver T. Keppler, Hanna-Mari Baldauf

P62 TRIM19/PML restricts HIV infection in a cell type-dependent manner

Bianca Volkmann, Tanja Kahle, Kristin Eissmann, Alexandra Herrmann, Sven Schmitt, Sabine Wittmann, Laura Merkel, Nina Reuter, Thomas Stamminger, Thomas Gramberg

P63 Recent invasion of the mule deer genome by a retrovirus

Helena Farkasova, Tomas Hron, Daniel Elleder

P64 Does the antiviral protein SAMHD1 influence mitochondrial function?

Ilaria Dalla Rosa, Kate Bishop, Antonella Spinazzola, Harriet Groom

P65 cGAMP transfers intercellularly via HIV-1 Env-mediated cell–cell fusion sites and triggers an innate immune response in primary target cells

Shuting Xu, Aurélie Ducroux, Aparna Ponnurangam, Sergej Franz, Gabrielle Vieyres, Mathias Müsken, Thomas Zillinger, Angelina Malassa, Ellen Ewald, Veit Hornung, Winfried Barchet, Susanne Häussler, Thomas Pietschmann, Christine Goffinet

P66 Pre-infection transcript levels of FAM26F in PBMCS inform about overall plasma viral load in acute and postacute phase after SIV-infection

Ulrike Sauermann, Aneela Javed, Nicole Leuchte, Gabriela Salinas, Lennart Opitz, Christiane Stahl-Hennig, Sieghart Sopper

P67 Sequence-function analysis of three T cell receptors targeting the HIV-1 p17 epitope SLYNTVATL

Christiane Mummert, Christian Hofmann, Angela G. Hückelhoven, Silke Bergmann, Sandra M. Müller-Schmucker, Ellen G. Harrer, Jan Dörrie, Niels Schaft, Thomas Harrer

P68 An immunodominant region of the envelope glycoprotein of small ruminant lentiviruses may function as decoy antigen

Laure Cardinaux, M.-L. Zahno, H.-R. Vogt, R. Zanoni, G. Bertoni

P69 Impact of immune activation, immune exhaustion, broadly neutralising antibodies and viral reservoirs on disease progression in HIV-infected children

Maximilian Muenchhoff, Philip Goulder, Oliver Keppler

Topic 9: Novel antiviral strategies

P70 Identification of natural compounds as new antiviral products by bioassay-guided fractionation

Alexandra Herrmann, Stephanie Rebensburg, Markus Helfer, Michael Schindler, Ruth Brack-Werner

P71 The PPARG antagonism disconnects the HIV replication and effector functions in Th17 cells

Yuwei Zhang, Huicheng Chen, Delphine Planas, Annie Bernier, Annie Gosselin, Jean-Pierre Routy, Petronela Ancuta

P72 Characterisation of a multiresistant subtype AG reverse transcriptase: AZT resistance, sensitivity to RNase H inhibitors and inhibitor binding

Birgitta Wöhrl, Anna Schneider, Angela Corona, Imke Spöring, Mareike Jordan, Bernd Buchholz, Elias Maccioni, Roberto Di Santo, Jochen Bodem, Enzo Tramontano, Kristian Schweimer

P73 Insigths into the acetylation pattern of HDAC inhibitors and their potential role in HIV therapy

Christian Schölz, Brian Weinert, Sebastian Wagner, Petra Beli, Yasuyuki Miyake, Jun Qi, Lars Jensen, Werner Streicher, Anna McCarthy, Nicholas Westwood, Sonia Lain, Jürgen Cox, Patrick Matthias, Matthias Mann, James Bradner, Chunaram Choudhary

P74 HPV-derived and seminal amyloid peptides enhance HIV-1 infection and impair the efficacy of broadly neutralising antibodies and antiretroviral drugs

Marcel Stern, Oliver T. Keppler

P75 D(−)lentiginosine inhibits both proliferation and virus expression in cells infected by HTLV-1 in vitro

Elena Valletta, Caterina Frezza, Claudia Matteucci, Francesca Marino-Merlo, Sandro Grelli, Anna Lucia Serafino, Antonio Mastino, Beatrice Macchi

P76 HIV-1 resistance analyses of the Cape Winelands districts, South Africa

Sello Mikasi, Graeme Jacobs, Susan Engelbrecht

Topic 10: Recent advances in HIV vaccine development

P77 Induction of complex retrovirus antigen-specific immune responses by adenovirus-based vectors depends on the order of vector administration

Meike Kaulfuß, Sonja Windmann, Wibke Bayer

P78 Direct impact of structural properties of HIV-1 Env on the regulation of the humoral immune response

Rebecca Heß, Michael Storcksdieck gen. Bonsmann, Viktoria Stab, Carsten Kirschning, Bernd Lepenies, Matthias Tenbusch, Klaus Überla

P79 Lentiviral virus-like particles mediate gerenration of T-follicular helper cells in vitro

Anne Kolenbrander, Klaus Überla, Vladimir Temchura

P80 Recruitment of HIV-1 Vpr to DNA damage sites and protection of proviral DNA from nuclease activity

Kenta Iijima, Junya Kobayashi, Yukihito Ishizaka

Secretoneurin gene therapy improves hind limb and cardiac ischaemia in Apo E⁻/⁻ mice without influencing systemic atherosclerosis

AIMS

Hypercholesterolaemia is a major risk factor for cardiovascular diseases and has been shown to influence angiogenesis in the hind limb ischaemia (HLI) model. The impaired up-regulation of angiogenic factors seems to be one of the underlying mechanisms for reduced vessel formation. Since we found that secretoneurin (SN) is up-regulated in hypoxic skeletal muscle cells and exerts beneficial effects in myocardial and HLI, we hypothesized that SN therapy might improve neovascularization in hypercholesterolaemic Apo E(-/-) (Apo E knockout) mice suffering from an impaired vascular response.

METHODS AND RESULTS

For in vitro experiments, endothelial cells (ECs) were incubated with oxidized low-density lipoprotein (oxLDL) to mimic hypercholesterolaemia. EC function was impaired by oxLDL, but SN induced EC proliferation and in vitro tube formation under these conditions. In the HLI model, injection of SN plasmid resulted in a significant better outcome regarding blood flow recovery, amputation rate, and vessel density. In the myocardial infarction (MI) model, the SN group showed improvement in cardiac parameters. Aortic plaque area was not influenced by local SN injection. Interestingly, SN-induced recruitment of angiogenic monocytic cells was abolished under hypercholesterolaemia.

CONCLUSIONS

SN gene therapy exerts beneficial effects in cardiovascular animal models in Apo E(-/-) mice without influencing atherosclerosis and might qualify as a promising therapy for cardiovascular disorders.

The arachidonic acid metabolome serves as a conserved regulator of cholesterol metabolism

Cholesterol metabolism is closely interrelated with cardiovascular disease in humans. Dietary supplementation with omega-6 polyunsaturated fatty acids including arachidonic acid (AA) was shown to favorably affect plasma LDL-C and HDL-C. However, the underlying mechanisms are poorly understood. By combining data from a GWAS screening in >100,000 individuals of European ancestry, mediator lipidomics, and functional validation studies in mice, we identify the AA metabolome as an important regulator of cholesterol homeostasis. Pharmacological modulation of AA metabolism by aspirin induced hepatic generation of leukotrienes (LTs) and lipoxins (LXs), thereby increasing hepatic expression of the bile salt export pump Abcb11. Induction of Abcb11 translated in enhanced reverse cholesterol transport, one key function of HDL. Further characterization of the bioactive AA-derivatives identified LX mimetics to lower plasma LDL-C. Our results define the AA metabolomeasconserved regulator of cholesterol metabolism, and identify AA derivatives as promising therapeutics to treat cardiovascular disease in humans.

Low energy shock wave therapy induces angiogenesis in acute hind-limb ischemia via VEGF receptor 2 phosphorylation

Objectives

Low energy shock waves have been shown to induce angiogenesis, improve left ventricular ejection fraction and decrease angina symptoms in patients suffering from chronic ischemic heart disease. Whether there is as well an effect in acute ischemia was not yet investigated.

Methods

Hind-limb ischemia was induced in 10–12 weeks old male C57/Bl6 wild-type mice by excision of the left femoral artery. Animals were randomly divided in a treatment group (SWT, 300 shock waves at 0.1 mJ/mm², 5 Hz) and untreated controls (CTR), n = 10 per group. The treatment group received shock wave therapy immediately after surgery.

Results

Higher gene expression and protein levels of angiogenic factors VEGF-A and PlGF, as well as their receptors Flt-1 and KDR have been found. This resulted in significantly more vessels per high-power field in SWT compared to controls. Improvement of blood perfusion in treatment animals was confirmed by laser Doppler perfusion imaging. Receptor tyrosine kinase profiler revealed significant phosphorylation of VEGF receptor 2 as an underlying mechanism of action. The effect of VEGF signaling was abolished upon incubation with a VEGFR2 inhibitor indicating that the effect is indeed VEGFR 2 dependent.

Conclusions

Low energy shock wave treatment induces angiogenesis in acute ischemia via VEGF receptor 2 stimulation and shows the same promising effects as known from chronic myocardial ischemia. It may therefore develop as an adjunct to the treatment armentarium of acute muscle ischemia in limbs and myocardium.

CBC-ARS2 stimulates 3'-end maturation of multiple RNA families and favors cap-proximal processing

The nuclear cap-binding complex (CBC) stimulates multiple steps in several RNA maturation pathways, but how it functions in humans is incompletely understood. For small, capped RNAs such as pre-snRNAs, the CBC recruits PHAX. Here, we identify the CBCAP complex, composed of CBC, ARS2 and PHAX, and show that both CBCAP and CBC-ARS2 complexes can be reconstituted from recombinant proteins. ARS2 stimulates PHAX binding to the CBC and snRNA 3'-end processing, thereby coupling maturation with export. In vivo, CBC and ARS2 bind similar capped noncoding and coding RNAs and stimulate their 3'-end processing. The strongest effects are for cap-proximal polyadenylation sites, and this favors premature transcription termination. ARS2 functions partly through the mRNA 3'-end cleavage factor CLP1, which binds RNA Polymerase II through PCF11. ARS2 is thus a major CBC effector that stimulates functional and cryptic 3'-end processing sites.

Topical secretoneurin gene therapy accelerates diabetic wound healing by interaction between heparan-sulfate proteoglycans and basic FGF

Diabetic foot ulcers represent a therapeutic problem of high clinical relevance. Reduced vascular supply, neuropathy and diminished expression of growth factors strongly contribute to wound healing impairment in diabetes. Secretoneurin, an angiogenic neuropeptide, has been shown to improve tissue perfusion in different animal models by increasing the amount of vessels in affected areas. Therefore, topical secretoneurin gene therapy was tested in a full thickness wound healing model in diabetic db/db mice. Secretoneurin significantly accelerated wound closure in these mice and immunohistochemistry revealed higher capillary and arteriole density in the wounded area compared to control mice. In-vitro, the mechanism of action of secretoneurin on human dermal microvascular endothelial cells was evaluated in normal and diabetic cells. Secretoneurin shows positive effects on in vitro angiogenesis, proliferation and apoptosis of these cells in a basic fibroblast growth factor dependent manner. A small molecular weight inhibitor revealed fibroblast growth factor receptor 3 as the main receptor for secretoneurin mediated effects. Additionally, we could identify heparan-sulfates as important co-factor of secretoneurin induced binding of basic fibroblast growth factor to human dermal endothelial cells. We suggest topical secretoneurin plasmid therapy as new tool for delayed wound healing in patients suffering from diabetes.

High-resolution NMR analysis of the conformations of native and base analog substituted retroviral and LTR-retrotransposon PPT primers

A purine-rich region of the plus-strand RNA genome of retroviruses and long terminal repeat (LTR)-containing retrotransposons, known as the polypurine tract (PPT), is resistant to hydrolysis by the RNase H domain of reverse transcriptase (RT) and ultimately serves as a primer for plus-strand DNA synthesis. The mechanisms underlying PPT resistance and selective processing remain largely unknown. Here, two RNA/DNA hybrids derived from the PPTs of HIV-1 and Ty3 were probed using high-resolution NMR for preexisting structural distortions in the absence of RT. The PPTs were selectively modified through base-pair changes or by incorporation of the thymine isostere, 2,4-difluoro-5-methylbenzene (dF), into the DNA strand. Although both wild-type (WT) and mutated hybrids adopted global A-form-like helical geometries, observed structural perturbations in the base-pair and dF-modified hybrids suggested that the PPT hybrids may function as structurally coupled domains.

A ribose sugar conformational switch in the LTR-retrotransposon Ty3 polypurine tract-containing RNA/DNA hybrid

To probe structural features of a polypurine tract (PPT) that mediate its specific recognition and processing, a model 20 bp RNA/DNA hybrid duplex, which includes the full PPT sequence of the Saccharomyces cerevisiae LTR-retrotransposon Ty3, has been investigated using solution NMR spectroscopy. While homonuclear NOESY and DQF-COSY analyses indicate that this PPT-containing RNA/DNA hybrid adopts an overall A-form-like helical geometry, an unexpected sugar pucker switch has been detected for the ribose at position +1, relative to the cleavage site, on the RNA strand. A model of the conformational changes induced by the A- to B-type sugar pucker switch shows a significant change in the backbone trajectory of the RNA strand, which alters the presentation of backbone phosphate and 2' hydroxyl groups 3' of this residue. This observation implies that part of the mechanism governing RNase H fidelity may be through distortion of the RNA/DNA helix one base ahead of the scissile bond.

Interaction of the Ty3 reverse transcriptase thumb subdomain with template-primer

Amino acid sequence alignment was used to identify the putative thumb subdomain of reverse transcriptase (RT) from the Saccharomyces cerevisiae long terminal repeat-containing retrotransposon Ty3. The counterpart to helix alphaH of human immunodeficiency virus type 1 (HIV-1) RT, which mediates important interactions with a duplex nucleic acid approximately 3-6 bp behind the DNA polymerase catalytic center, was identified between amino acids 290 and 298 of the Ty3 enzyme. The consequences of substituting Ty3 RT Gln290, Phe292, Gly294, Asn297, and Tyr298 (the counterparts of HIV-1 RT Gln258, Leu260, Gly262, Asn265, and Trp266, respectively) for both DNA polymerase and RNase H activities were examined. DNA-dependent DNA synthesis was evaluated on unmodified substrates and on duplexes containing targeted insertion of locked nucleic acid analogs and abasic lesions in either the template or primer. Based on this combined strategy, our data suggest an interaction of Ty3 RT Tyr298 with primer nucleotide -3, Gly294 with primer nucleotide -4, and Asn297 with template nucleotide -6. Substitution of Ala for Gln290 was well tolerated, despite the high degree of conservation at this position. Mutations in the thumb subdomain of Ty3 also affected RNase H activity, suggesting a closer spatial relationship between its N- and C-terminal catalytic centers compared with HIV-1 RT.

The chaperoning and assistance roles of the HIV-1 nucleocapsid protein in proviral DNA synthesis and maintenance

In the following three sections, we will briefly review the seminal roles of the HIV-1 nucleocapsid protein p7 (NCp7) in the fate of the HIV-1 full length RNA from genomic RNA in a dimeric form to the proviral DNA. Emphasis will be given to the mechanisms of NC-directed assistance to the genomic RNA and reverse transcriptase (RT) in the course of proviral DNA synthesis and to DNA integrity at the end of the polymerization process, and to the NC-assisted repair and recombination reactions fueling the viability and variability of the virus.

Functional roles of carboxylate residues comprising the DNA polymerase active site triad of Ty3 reverse transcriptase

Aspartic acid residues comprising the -D-(aa)_n-Y-L-D-D- DNA polymerase active site triad of reverse transcriptase from the Saccharomyces cerevisiae long terminal repeat-retrotransposon Ty3 (Asp151, Asp213 and Asp214) were evaluated via site-directed mutagenesis. An Asp151→Glu substitution showed a dramatic decrease in catalytic efficiency and a severe translocation defect following initiation of DNA synthesis. In contrast, enzymes harboring the equivalent alteration at Asp213 and Asp214 retained DNA polymerase activity. Asp151→Asn and Asp213→Asn substitutions eliminated both polymerase activities. However, while Asp214 of the triad could be replaced by either Asn or Glu, introducing Gln seriously affected processivity. Mutants of the carboxylate triad at positions 151 and 213 also failed to catalyze pyrophosphorolysis. Finally, alterations to the DNA polymerase active site affected RNase H activity, suggesting a close spatial relationship between these N- and C-terminal catalytic centers. Taken together, our data reveal a critical role for Asp151 and Asp213 in catalysis. In contrast, the second carboxylate of the Y-L-D-D motif (Asp214) is not essential for catalysis, and possibly fulfills a structural role. Although Asp214 was most insensitive to substitution with respect to activity of the recombinant enzyme, all alterations at this position were lethal for Ty3 transposition.

The chaperoning and assistance roles of the HIV-1 nucleocapsid protein in proviral DNA synthesis and maintenance

In the following three sections we will briefly review the seminal roles of the HIV-1 nucleocapsid protein NCp7 in the fate of the HIV-1 full length RNA from genomic RNA in a dimeric form to the proviral DNA. Emphasis will be given to the mechanisms of NC-directed assistance to the genomic RNA and reverse transcriptase in the course of proviral DNA synthesis and to DNA integrity at the end of the polymerization process, and to the NC-assisted repair and recombination reactions fueling the viability and variability of the virus.

Nonpolar thymine isosteres in the Ty3 polypurine tract DNA template modulate processing and provide a model for its recognition by Ty3 reverse transcriptase

Despite diverging in sequence and size, the polypurine tract (PPT) primers of retroviruses and long terminal repeat-containing retrotransposons are accurately processed from (+) U3 RNA and DNA by their cognate reverse transcriptases (RTs). In this paper, we demonstrate that misalignment of the Ty3 retrotransposon RT on the human immunodeficiency virus-1 PPT induces imprecise removal of adjacent (+)-RNA and failure to release (+)-DNA from the primer. Based on these observations, we explored the structural basis of Ty3 PPT recognition by chemically synthesizing RNA/DNA hybrids whose (-)-DNA template was substituted with the non-hydrogen-bonding thymine isostere 2,4-difluoro-5-methylbenzene (F). We observed a consistent spatial correlation between the site of T --> F substitution and enhanced ribonuclease H (RNase H) activity approximately 12-13 bp downstream. In the most pronounced case, dual T --> F substitution at PPT positions -1/-2 redirects RNase H cleavage almost exclusively to the novel site. The structural features of this unusual base suggest that its insertion into the Ty3 PPT (-)-DNA template weakens the duplex, inducing a destabilization that is recognized by a structural element of Ty3 RT approximately 12-13 bp from its RNase H catalytic center. A likely candidate for this interaction is the thumb subdomain, whose minor groove binding tract most likely contacts the duplex. The spatial relationship derived from T --> F substitution also infers that Ty3 PPT processing requires recognition of sequences in its immediate 5' vicinity, thereby locating the RNase H catalytic center over the PPT-U3 junction, a notion strengthened by additional mutagenesis studies of this paper.

Mutating conserved residues in the ribonuclease H domain of Ty3 reverse transcriptase affects specialized cleavage events

The reverse transcriptase-associated ribonuclease H (RT/RNase H) domains from the gypsy group of retrotransposons, of which Ty3 is a member, share considerable sequence homology with their retroviral counterparts. However, the gypsy elements have a conserved tyrosine (position 459 in Ty3 RT) instead of the conserved histidine in the catalytic center of retroviral RTs such as at position 539 of HIV-1. In addition, the gypsy group shows conservation of histidine adjacent to the third of the metal-chelating carboxylate residues, which is Asp-426 of Ty3 RT. The role of these and additional catalytic residues was assessed with purified recombinant enzymes and through the ability of Ty3 mutants to support transposition in Saccaromyces cerevisiae. Although all mutations had minimal impact on DNA polymerase function, amidation of Asp-358, Glu-401, and Asp-426 eliminated Mg(2+)- and Mn(2+)-dependent RNase H function. Replacing His-427 and Tyr-459 with Ala and Asp-469 with Asn resulted in reduced RNase H activity in the presence of Mg(2+), whereas in the presence of Mn(2+) these mutants displayed a lack of turnover. Despite this, mutations at all positions were lethal for transposition. To reconcile these apparently contradictory findings, the efficiency of specialized RNase H-mediated events was examined for each enzyme. Mutants retaining RNase H activity on a heteropolymeric RNA.DNA hybrid failed to support DNA strand transfer and release of the (+) strand polypurine tract primer from (+) RNA, suggesting that interrupting one or both of these events might account for the transposition defect.

Altering the RNase H primer grip of human immunodeficiency virus reverse transcriptase modifies cleavage specificity

Recent crystallographic data suggest that conserved residues in the connection subdomain and C-terminal ribonuclease H (RNase H) domain of human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT) contact the nascent DNA primer and modulate the trajectory of the template relative to the RNase H catalytic center. Within the RNase H domain, these residues include Thr473, Glu475, Lys476, Tyr501, and Ile505, while His539 and Asn474 interact with the scissile phosphate of the RNA template. Amino acid substitutions at several of these positions were evaluated in the context of hydrolysis of nonspecific RNA-DNA hybrids and substrates mimicking specific RNase H-mediated events. With the exception of mutant I505G, which exhibited a dimerization defect, substituting alanine at positions 473-476 and 501 had minimal consequences for DNA synthesis on duplex and hybrid DNA and RNA substrates. In contrast, the efficiency with which most mutants catalyzed polymerization-independent RNase H cleavage was sharply reduced. This deficiency was more pronounced when mutant enzymes were challenged to process the (+) strand polypurine tract (PPT) primer from either (+) RNA or a PPT/(+) DNA RNA/DNA chimera. Reduced polymerization-independent RNase H activity also significantly influenced the rate of DNA strand transfer, suggesting the donor template must be reduced in size below 13 nt before this event proceeds.

Involvement of HIV-I nucleocapsid protein in the recruitment of reverse transcriptase into nucleoprotein complexes formed in vitro

Retroviral reverse transcription takes place within the virion core, where nucleocapsid (NC) protein (NCp) molecules cover the dimeric RNA genome. NCp thus has structural roles in the virion core but is also extensively involved in viral DNA synthesis and virion assembly. To further characterize the role of human immunodeficiency virus type 1 NCp7 during replication of the viral genome, we investigated the relationship between NCp7 and reverse transcriptase (RT) either directly or within nucleoprotein complexes in vitro. We show that NCp7 interacts directly with RT and enhances synthesis of full-length cDNA by increasing RT processivity. Using NCp7 mutants, we show that the complete amino acid sequence of NCp7 is required for functional interactions with RT. Our results suggest that NCp7 plays a role in recruitment of RT into stable and functional nucleoprotein complexes during viral DNA synthesis.

Role of the N-terminal zinc finger of human immunodeficiency virus type 1 nucleocapsid protein in virus structure and replication

Nucleocapsid protein (NCp7) of human immunodeficiency virus type 1 is found covering the genomic RNA in the interior of the viral particle. It is a highly basic protein with two zinc fingers of the form CX2CX4HX4C which exhibit strong affinity for a zinc cation. To study the structure-function relationship of the N-terminal zinc finger of NCp7, this domain was either deleted or changed to CX2CX4CX4C. We examined virus formation and structure as well as proviral DNA synthesis. Our data show that these two NC mutations result in the formation of particles with an abnormal core morphology and impair the end of proviral DNA synthesis, leading to noninfectious viruses.

In vitro characterization of peptides interfering with the hiv-1 nucleocapsid protein (ncp7) functions

Abstract:

In HIV-I, the nucleocapsid protein (NCp7) play essential roles in several steps of HIV-I replication. Since NCp7 is required for virion formation and proviral DNA synthesis and is highly conserved, identification of compounds able to inhibit NCp7 activities and functions may lead to the discovery of new anti-HIV drugs. Here we present data showing that peptides derived from the first and second NCp7 zinc finger interfere, in vitro, with NCp7 functions during the early stage of HIV- I reverse transcription.

Use of a constrain phage displayed-peptide library for the isolation of peptides binding to HIV-1 nucleocapsid protein (NCp7)

It has been shown that peptide libraries are powerful tools for the identification of peptides showing new binding specificity. This technology was applied to the isolation of peptides binding to HIV-1 nucleocapsid protein (NCp7). Three different prolin reach peptide sequences, interacting with NCp7, were isolated, from a constrained phage displayed-peptide library of 10(8) independent clones. The three peptide sequences, isolated from the peptide library, were shown to bind NCp7 in the region 30-52. Moreover, two of them share the PP-(D/E)R consensus sequence.