A dose-effect relationship for deltaretrovirus-dependent leukemogenesis in sheep

<p>Abstract</p> <p>Background</p> <p>Retrovirus-induced tumors develop in a broad range of frequencies and after extremely variable periods of time, from only a few days to several decades, depending mainly on virus type. For hitherto unexplained reasons, deltaretroviruses cause hematological malignancies only in a minority of naturally infected organisms and after a very prolonged period of clinical latency.</p> <p>Results</p> <p>Here we demonstrate that the development of malignancies in sheep experimentally infected with the deltaretrovirus bovine leukemia virus (BLV) depends only on the level of BLV replication. Animals were experimentally infected with leukemogenic or attenuated, but infectious, BLV molecular clones and monitored prospectively through 8 months for viral replication. As early as 2 weeks after infection and subsequently at any time during follow-up, leukemogenic viruses produced significantly higher absolute levels of reverse transcription (RT), clonal expansion of infected cells, and circulating proviruses with RT- and somatic-dependent mutations than attenuated viruses. These differences were only quantitative, and both kinds of viruses triggered parallel temporal fluctuations of host lymphoid cells, viral loads, infected cell clonality and proliferation.</p> <p>Conclusion</p> <p>Deltaretrovirus-associated leukemogenesis in sheep appears to be a two-hit process over time depending on the amounts of first horizontally and then vertically expanded viruses.</p

Early and transient reverse transcription during primary deltaretroviral infection of sheep

<p>Abstract</p> <p>Background</p> <p>Intraindividual genetic variability plays a central role in deltaretrovirus replication and associated leukemogenesis in animals as in humans. To date, the replication of these viruses has only been investigated during the chronic phase of the infection when they mainly spread through the clonal expansion of their host cells, vary through a somatic mutation process without evidence for reverse transcriptase (RT)-associated substitution. Primary infection of a new organism necessary involves allogenic cell infection and thus reverse transcription.</p> <p>Results</p> <p>Here we demonstrate that the primary experimental bovine leukemia virus (BLV) infection of sheep displays an early and intense burst of horizontal replicative dissemination of the virus generating frequent RT-associated substitutions that account for 69% of the in vivo BLV genetic variability during the first 8 months of the infection. During this period, evidence has been found of a cell-to-cell passage of a mutated sequence and of a sequence having undergone both RT-associated and somatic mutations. The detection of RT-dependent proviral substitution was restricted to a narrow window encompassing the first 250 days following seroconversion.</p> <p>Conclusion</p> <p>In contrast to lentiviruses, deltaretroviruses display two time-dependent mechanisms of genetic variation that parallel their two-step nature of replication <it>in vivo</it>. We propose that the early and transient RT-based horizontal replication helps the virus escape the first wave of host immune response whereas somatic-dependent genetic variability during persistent clonal expansion helps infected clones escape the persistent and intense immune pressure that characterizes the chronic phase of deltaretrovirus infection.</p

Noninvasive Assessment of Atrial Fibrillation Complexity in Relation to Ablation Characteristics and Outcome

Background: The use of surface recordings to assess atrial fibrillation (AF) complexity is still limited in clinical practice. We propose a noninvasive tool to quantify AF complexity from body surface potential maps (BSPMs) that could be used to choose patients who are eligible for AF ablation and assess therapy impact.Methods: BSPMs (mean duration: 7 ± 4 s) were recorded with a 252-lead vest in 97 persistent AF patients (80 male, 64 ± 11 years, duration 9.6 ± 10.4 months) before undergoing catheter ablation. Baseline cycle length (CL) was measured in the left atrial appendage. The procedural endpoint was AF termination. The ablation strategy impact was defined in terms of number of regions ablated, radiofrequency delivery time to achieve AF termination, and acute outcome. The atrial fibrillatory wave signal extracted from BSPMs was divided in 0.5-s consecutive segments, each projected on a 3D subspace determined through principal component analysis (PCA) in the current frame. We introduced the nondipolar component index (NDI) that quantifies the fraction of energy retained after subtracting an equivalent PCA dipolar approximation of heart electrical activity. AF complexity was assessed by the NDI averaged over the entire recording and compared to ablation strategy.Results: AF terminated in 77 patients (79%), whose baseline AF CL was 177 ± 40 ms, whereas it was 157 ± 26 ms in patients with unsuccessful ablation outcome (p = 0.0586). Mean radiofrequency emission duration was 35 ± 21 min; 4 ± 2 regions were targeted. Long-lasting AF patients (≥12 months) exhibited higher complexity, with higher NDI values (≥12 months: 0.12 ± 0.04 vs. &lt;12 months: 0.09 ± 0.03, p &lt; 0.01) and short CLs (&lt;160 ms: 0.12 ± 0.03 vs. between 160 and 180 ms: 0.10 ± 0.03 vs. &gt;180 ms: 0.09 ± 0.03, p &lt; 0.01). More organized AF as measured by lower NDI was associated with successful ablation outcome (termination: 0.10 ± 0.03 vs. no termination: 0.12 ± 0.04, p &lt; 0.01), shorter procedures (&lt;30 min: 0.09 ± 0.04 vs. ≥30 min: 0.11 ± 0.03, p &lt; 0.001) and fewer ablation targets (&lt;4: 0.09 ± 0.03 vs. ≥4: 0.11 ± 0.04, p &lt; 0.01).Conclusions: AF complexity can be noninvasively quantified by PCA in BSPMs and correlates with ablation outcome and AF pathophysiology

Aspects moléculaires du stade précoce de l'infection expérimentale du mouton par le virus de la leucémie bovine et implications sur la leucémogenèse associée au deltarétrovirus

La réplication des deltarétrovirus oncogènes au stade chronique de l infection s opère essentiellement via l expansion clonale des cellules infectées dans un contexte d instabilité génétique générée par l oncoprotéine virale Tax. Dans le modèle du mouton expérimentalement infecté par le BLV, les cellules à l origine de la tumeur peuvent être distinguées au stade précoce de l'infection par leur degré de prolifération et d instabilité génétique. La phase aigue de l infection a été caractérisée par une lymphocytose B qui participait à l augmentation de la charge provirale. Elle s accompagnait d une variabilité génétique importante du virus issue des étapes de transcription inverse et de processus somatiques. La première apparaissait restreinte au premiers mois qui suivent l inoculation alors que la seconde persistait au cours de l infection. L oncogénicité du deltarétrovirus dépendait du nombre total de clones infectés circulants et de réarrangements des provirus détectés à la primoinfectionThe replication of oncogenic deltaretroviruses at the chronic stage of infection is achieved mainly through clonal expansion of infected cells on a background of genetic instability induced by the viral oncoprotein Tax. In the sheep model experimentally infected with BLV, the cells from which the tumor arises, can be distinguished at early infection stages on the basis of their degree of proliferation and genetic instability. The acute stage of infection has been characterized by a B lymphocytosis, partly responsible for the increased proviral load. It was associated with a high level of viral genetic variability induced by steps of reverse transcription and by somatic processes. The first phase appeared to be restricted to the first months post-inoculation whereas the second phase prevailed throughout the infection. The oncogenicity of the deltaretrovirus was related to the overall number of circulating infected clones and of provirus rearrangements detected at the stage of primary infectionLYON1-BU.Sciences (692662101) / SudocSudocFranceF

Functional characterization of Negri Bodies (NBs) in Rabies Virus-Infected cells : evidence that NBs are sites of viral transcription and replication

International audienceRabies virus infection induces the formation of cytoplasmic inclusion bodies that resemble Negri bodies found in the cytoplasm of some infected nerve cells. We have studied the morphogenesis and the role of these Negri body-like structures (NBLs) during viral infection. The results indicate that these spherical structures (one or two per cell in the initial stage of infection), composed of the viral N and P proteins, grow during the virus cycle before appearing as smaller structures at late stages of infection. We have shown that the microtubule network is not necessary for the formation of these inclusion bodies but is involved in their dynamics. In contrast, the actin network does not play any detectable role in these processes. These inclusion bodies contain Hsp70 and ubiquitinylated proteins, but they are not misfolded protein aggregates. NBLs, in fact, appear to be functional structures involved in the viral life cycle. Specifically, using in situ fluorescent hybridization techniques, we show that all viral RNAs (genome, antigenome, and every mRNA) are located inside the inclusion bodies. Significantly, short-term RNA labeling in the presence of BrUTP strongly suggests that the NBLs are the sites where viral transcription and replication take place

Transjugular intrahepatic portosystemic shunt before abdominal surgery in cirrhotic patients: A retrospective, comparative study

Surgery in cirrhotic patients is associated with high morbidity and mortality related to portal hypertension and liver insufficiency. Therefore, preoperative portal decompression is a logical approach to facilitate abdominal surgery and hopefully to improve postoperative survival. The present study evaluated the clinical outcomes of 18 patients (mean age 58 years) with cirrhosis (seven alcoholics and 11 nonalcoholics) who underwent transjugular intrahepatic portosystemic shunt (TIPS) placement before antrectomy (n=5), colectomy (n=10), small-bowel resection (n=1), pancreatectomy (n=1) and nephrectomy (n=1). TIPS was performed a mean (± SD) of 72±21 days before surgery and induced a marked mean decrease in portohepatic gradient from 21.4±3.9 mmHg to 8.4±3.4 mmHg. Cirrhotic patients (n=17) who underwent elective abdominal surgery without preoperative TIPS placement were used as the control group. Both groups were matched for age, etiology of cirrhosis, indications for surgery, type of surgery and coagulation parameters. The mean Pugh score was significantly higher in the TIPS group (7.7 versus 6.2). No significant differences were observed for operative blood loss, postoperative complications, duration of hospitalization and one-month (83% versus 88%) or one-year (54% versus 63%) cumulative survival rate. Analysis using the Cox proportional hazards model showed that neither TIPS placement nor preoperative Pugh score were independent predictors for survival. The present study suggests that preoperative TIPS placement does not improve postoperative evolution after abdominal surgery in cirrhotic patients with good or moderately impaired liver function

Fate of premalignant clones during the asymptomatic phase preceding lymphoid malignancy.

peer reviewedAlmost all cancers are preceded by a prolonged period of clinical latency during which a combination of cellular events helps move carcinogen-exposed cells towards a malignant phenotype. Hitherto, investigating the fate of premalignant cells in vivo remained strongly hampered by the fact that these cells are usually indistinguishable from their normal counterparts. Here, for the first time, we have designed a strategy able to reconstitute the replicative history of the bona fide premalignant clone in an animal model, the sheep experimentally infected with the lymphotropic bovine leukemia virus. We have shown that premalignant clones are early and clearly distinguished from other virus-exposed cells on the basis of their degree of clonal expansion and genetic instability. Detectable as early as 0.5 month after the beginning of virus exposure, premalignant cells displayed a two-step pattern of extensive clonal expansion together with a mutation load approximately 6 times higher than that of other virus-exposed cells that remained untransformed during the life span of investigated animals. There was no fixation of somatic mutations over time, suggesting that they regularly lead to cellular death, partly contributing to maintain a normal lymphocyte count during the prolonged premalignant stage. This equilibrium was finally broken after a period of 18.5 to 60 months of clinical latency, when a dramatic decrease in the genetic instability of premalignant cells coincided with a rapid increase in lymphocyte count and lymphoma onset

Antiretroviral therapy promotes an inflammatory-like pattern of human T-cell lymphotropic virus type 1 (HTLV-1) replication in human immunodeficiency virus type 1/HTLV-1 co-infected individuals.

Upon antiretroviral therapy (ART) human immunodeficiency virus (HIV)/human T-cell lymphotropic virus type 1 (HTLV-1) co-infected individuals frequently develop neurological disorders through hitherto unknown mechanisms. Here, we show that effective anti-HIV ART increases HTLV-1 proviral load through a polyclonal integration pattern of HTLV-1 in both CD4(+) and CD8(+) T-cell subsets that is reminiscent of that typically associated with HTLV-1-related inflammatory conditions. These data indicate that preventing ART-triggered clonal expansion of HTLV-1-infected cells in co-infected individuals deserves investigation