Different animal models have been proposed to investigate the mechanisms of Human T-lymphotropic Virus (HTLV)-induced pathogenesis: rats, transgenic and NOD-SCID/γcnull (NOG) mice, rabbits, squirrel monkeys, baboons and macaques. These systems indeed provide useful information but have intrinsic limitations such as lack of disease relevance, species specificity or inadequate immune response. Another strategy based on a comparative virology approach is to characterize a related pathogen and to speculate on possible shared mechanisms. In this perspective, bovine leukemia virus (BLV), another member of the deltaretrovirus genus, is evolutionary related to HTLV-1. BLV induces lymphoproliferative disorders in ruminants providing useful information on the mechanisms of viral persistence, genetic determinants of pathogenesis and potential novel therapies.

Viruses have coevolved with their host to ensure efficient replication and transmission without inducing excessive pathogenicity that would indirectly impair their persistence. This is exemplified by the bovine leukemia virus (BLV) system in which lymphoproliferative disorders develop in ruminants after latency periods of several years. In principle, the equilibrium reached between the virus and its host could be disrupted by emergence of more pathogenic strains. Intriguingly but fortunately, such a hyperpathogenic BLV strain was never observed in the field or designed in vitro. In this study, we sought to understand the role of envelope N-linked glycosylation with the hypothesis that this posttranslational modification could either favor BLV infection by allowing viral entry or allow immune escape by using glycans as a shield. Using reverse genetics of an infectious molecular provirus, we identified a N-linked envelope glycosylation site (N230) that limits viral replication and pathogenicity. Indeed, mutation N230E unexpectedly leads to enhanced fusogenicity and protein stability. There is no satisfactory treatment for HAM/TSP, and the prognosis for ATLL is still poor despite improved therapies (2). BLV is responsible for major economic losses in cattle due to export limitations, carcass condemnations, and reduction in milk production. BLV infection also correlates with a significant morbidity resulting from opportunistic infections and a decrease in longevity due to tumor development (3). In a proportion (i.e., about one third) of infected cattle, BLV induces a lymphoproliferative disease called persistent lymphocytosis. After a latency period of several years, BLV infection also leads to leukemia and/or lymphoma in a minority (5%) of the infected animals. However, the majority of BLV carriers remain clinically healthy and acts as asymptomatic carriers for viral spread (4). Besides its natural hosts (i.e., cattle, zebu, and water buffalo), BLV can be experimentally transmitted to sheep and goats, where leukemia/lymphoma develops after shorter latency periods (5-7).Retroviral envelope glycoproteins play an important role in the viral life cycle: they contain the recognition site required for entry and mediate cell fusion (8). The BLV envelope is composed of two glycoproteins: a surface (SU) protein, Gp51, and a transmembrane (TM) protein, Gp30, derived from the proteolytic cleavage of a common precursor (gpr72) encoded by the env gene (9-11). The SU protein is N-glycosylated in the rough endoplasmic reticulum by covalent attachment of oligosaccharide chains (12). Although the role of BLV SU-linked glycans is currently unknown, it is expected that N-glycosylation is required for protein folding, stability, or solubility (13). Furthermore, N-glycans are also likely involved in transport of BLV envelope proteins to the cell membrane, binding to cellular receptors and cell-to-cell fusion (14-18) similarly to glycans of the human immunodeficiency virus (HIV) envelope glycoprotein that modulate fusogenicity ...

Viruses have developed different strategies to escape from immune response. Among these, viral non-coding RNAs are invisible to the immune system and may affect the fate of the host cell. Bovine leukemia virus (BLV) encodes both short (miRNAs) and long (antisense AS1 and AS2) non-coding RNAs. To elucidate the mechanisms associated with BLV noncoding RNAs, we performed phenotypic and transcriptomic analyzes in a reverse genetics system. RNA sequencing of B-lymphocytes revealed that cell proliferation is the most significant mechanism associated with ablation of the viral non-coding RNAs. To assess the biological relevance of this observation, we determined the cell kinetic parameters in vivo using intravenous injection of BrdU and CFSE. Fitting the data to a mathematical model provided the rates of cell proliferation and death. Our data show that deletion of miRNAs correlates with reduced proliferation of the infected cell and lack of pathogenesis.

Vaccination against retroviruses is a challenge because of their ability to stably integrate into the host genome, undergo long-term latency in a proportion of infected cells and thereby escape immune response. Since clearance of the virus is almost impossible once infection is established, the primary goal is to achieve sterilizing immunity. Besides efficacy, safety is the major issue since vaccination has been associated with increased infection or reversion to pathogenicity. In this review, we discuss the different issues that we faced during the development of an efficient vaccine against bovine leukemia virus (BLV). We summarize the historical failures of inactivated vaccines, the efficacy and safety of a live-attenuated vaccine and the economical constraints of further industrial development.

Previous attempts to develop a vaccine against bovine leukemia virus (BLV) have not been successful because of inadequate or short-lived stimulation of all immunity components. In this study, we designed an approach based on an attenuated BLV provirus by deleting genes dispensable for infectivity but required for efficient replication. The ability of the vaccine to protect from natural BLV infection was investigated in the context of dairy productive conditions in an endemic region. The attenuated vaccine was tested in a farm in which the prevalence rose from 16.7% in young cattle at the beginning of the study to more than 90% in adult individuals. Sterilizing immunity was obtained in 28 out of 29 vaccinated heifers over a period of 48 months, demonstrating the effectiveness of the vaccine. As indicated by the antiviral antibody titers, the humoral response was slightly reduced compared to wild-type infection. After initial post-vaccination bursts, the proviral loads of the attenuated vaccine remained most frequently undetectable. During the first dairy cycle, proviral DNA was not detected by nested-PCR in milk samples from vaccinated cows. During the second dairy cycle, provirus was sporadically detected in milk of two vaccinated cows. Forty-two calves born from vaccinated cows were negative for proviral DNA but had antiviral antibodies in their peripheral blood. The attenuated strain was not transmitted to sentinels, further supporting the safety of the vaccine. Altogether, these data thus demonstrate that the vaccine against BLV is safe and effective in herd conditions characterized by a very high incidence. This cost-effective approach will thus decrease the prevalence of BLV without modification of production practices. After facing a series of challenges pertaining to effectiveness and biosafety, the vaccine is now available for further large-scale delivery. The different challenges and hurdles that were bypassed may be informative for the development of a vaccine against HTLV-1.

The composition of the tumor microenvironment (TME) mediates the outcome of chemo- and immunotherapies in malignant pleural mesothelioma (MPM). Tumor-associated macrophages (TAMs) and monocyte myeloid-derived immunosuppressive cells (M-MDSCs) constitute a major fraction of the TME. As central cells of the innate immune system, monocytes exert well-characterized functions of phagocytosis, cytokine production, and antibody-dependent cell-mediated cytotoxicity (ADCC). The objective of this study was to evaluate the ability of monocytes to exert a direct cytotoxicity by cell-to-cell contact with MPM cells. The experimental model is based on cocultures between human blood-derived monocytes sorted by negative selection and mesothelioma cell lines. Data show (i) that blood-derived human monocytes induce tumor cell death by direct cell-to-cell contact, (ii) that VPA is a pharmacological enhancer of this cytotoxic activity, (iii) that VPA increases monocyte migration and their aggregation with MPM cells, and (iv) that the molecular mechanisms behind VPA modulation of monocytes involve a downregulation of the membrane receptors associated with the M2 phenotype, i.e., CD163, CD206, and CD209. These conclusions, thus, broaden our understanding about the molecular mechanisms involved in immunosurveillance of the tumor microenvironment and open new prospects for further improvement of still unsatisfactory MPM therapies

Background The patient’s needs and expectations can be assessed through satisfaction surveys, adverse event declarations and records of complaints. However, by crossing individual complaints, satisfaction surveys in combination with adverse events received we could get valuable information. The objective is to identify common elements of work between these different sources to improve care. Methods A retrospective analysis of patient’s complaints, surveys and adverse events was carried out in order to highlight common improvement items between these 3 sources of information. Results A satisfaction survey was given to the patients at the end of their treatment, who filled it out and left it in the “ad hoc” letterbox. At the end of December 2019, 4695 questionnaires had been collected (response rate 37%). In addition, since 2014, 1369 patients (approximately 20 patients per month) have been interviewed “face to face” by the research nurse who assesses their satisfaction using open questions. At the same time, a collection of complaints and adverse events was carried out. All this data has been analysed and cross-checked in order to highlight areas for improvement, in order to strengthen the safety and quality of care in our department. Conclusions Collecting and analysing satisfactions surveys, unexpected events and complaints constitute in our opinion, an effective tool to achieve patient empowerment. We aim for the patients to become a real player in their safety, involved in the overall effort to improve quality of their radiotherapy treatment by reporting what does not meet their expectations.

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