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International audience; The selective downregulation of activated intracellular proteins is a key challenge in cell biology. RHO small GTPases switch between a guanosine diphosphate (GDP)-bound and a guanosine triphosphate (GTP)-bound state that drives downstream signaling. At present, no tool is available to study endogenous RHO-GTPinduced conformational changes in live cells. Here, we established a cell-based screen to selectively degrade RHOB-GTP using F-box-intracellular single-domain antibody fusion. We identified one intracellular antibody (intrabody) that shows selective targeting of endogenous RHOB-GTP mediated by interactions between the CDR3 loop of the domain antibody and the GTP-binding pocket of RHOB. Our results suggest that, while RHOB is highly regulated at the expression level, only the GTPbound pool, but not its global expression, mediates RHOB functions in genomic instability and in cell invasion. The F-box/intrabody-targeted protein degradation represents a unique approach to knock down the active form of small GTPases or other proteins with multiple cellular activities.

The selective down-regulation of activated intracellular proteins is a key challenge in cell biology. RHO small GTPases switch between a GDPbound and a GTP-bound state that drives downstream signaling. To date, no tool is available to study endogenous RHO induced conformational changes in live cells. Here, we set up an original cell-based screen to selectively degrade the RHOB-GTP fraction using nanobodies functionalized with a F-box domain. We identified one intrabody that shows selective targeting of endogenous RHOB-GTP mediated by interactions between the intrabody CDR3 loop and the GTP-binding pocket of RHOB. Our results indicate that, while RHOB is highly regulated at the expression level, only the minor GTP-bound fraction but not its global expression mediates RHOB functions in genomic instability and in cell invasion. The F-box/intrabody-mediated protein degradation represents a unique approach to selectively target the active form of small GTPases or other proteins with multiple cellular activities.

The rat is an important biomedical experimental model that benefited from the recent development of new transgenic and knockout techniques. With the goal to optimize rat mAb production and to analyze the impact of Bcl-2 on B-cell development, we generated bcl-2 transgenic rats. Transgenic rats showed Bcl-2 over-expression in B cells, increased B cell numbers in lymphoid organs, elevated production of immunoglobulins (Igs) and prolonged B-cell survival in vitro. Transgenic rats remained healthy, reproduced normally and did not develop autoimmunity. Fusions with bcl-2 transgenic splenocytes did not result in increased hybridoma generation. A comparison of on- and off-rates of 39 mAbs generated with bcl-2 transgenic and wild-type animals revealed no significant differences. Over-expression of Bcl-2 in hybridomas did not change cell proliferation but resulted in increased Ig production. Bcl-2 transgenic rats will be a useful tool for the generation of rat mAbs, the analysis of B cells in different pathophysiological models, such as autoimmunity, cancer or organ transplantation, and the study of rat B-cell biology.

International audience; Human hepatocellular carcinoma (HCC) is the most common type of liver cancer, the second most common cause of death from cancer worldwide. A very poor prognosis and a lack of effective treatments make liver cancer a major public health problem, notably in less developed regions, particularly in eastern Asia. This fully justifies the search of new molecules and therapeutic strategies against HCC. Ent‐kaurane diterpenoids are natural compounds displaying a broad spectrum of potential therapeutic effects including anticancer activity. In this study, we analyzed the pharmacological properties of a family of ent‐kaurane diterpenoids from Croton tonkinensis Gagnep in human HepG2 and Hep3b cell lines, used as cellular reference models for in vitro evaluation of new molecules active on HCC. A structure‐related cytotoxicity was observed against both HCC cell lines, enlighting the role of the 16‐en‐15‐one skeleton of ent‐kaurane diterpenoids. Cytotoxicity was closely correlated to apoptosis, evidenced by concentration‐dependent subG1 cell accumulation, and increased annexin V expression. In addition, subtoxic concentration of ent‐kaurane diterpenoid dramatically enhanced the sensitivity of HCC cells to doxorubicin. All together, our data bring strong support to the potential interest of ent‐kaurane diterpenoids, alone or in combination with a cytotoxic agent, in cancer and more precisely against HCC.

Mice transgenic for human Ig loci are an invaluable resource for the production of human Abs. However, such mice often do not yield human mAbs as effectively as conventional mice yield mouse mAbs. Suboptimal efficacy in delivery of human Abs might reflect imperfect interaction between the human membrane IgH chains and the mouse cellular signaling machinery. To obviate this problem, in this study we generated a humanized rat strain (OmniRat) carrying a chimeric human/rat IgH locus (comprising 22 human VHs, all human D and JH segments in natural configuration linked to the rat CH locus) together with fully human IgL loci (12 Vκs linked to Jκ-Cκ and 16 Vλs linked to Jλ-Cλ). The endogenous Ig loci were silenced using designer zinc finger nucleases. Breeding to homozygosity resulted in a novel transgenic rat line exclusively producing chimeric Abs with human idiotypes. B cell recovery was indistinguishable from wild-type animals, and human V(D)J transcripts were highly diverse. Following immunization, the OmniRat strain performed as efficiently as did normal rats in yielding high-affinity serum IgG. mAbs, comprising fully human variable regions with subnanomolar Ag affinity and carrying extensive somatic mutations, are readily obtainable, similarly to conventional mAbs from normal rats.

BACKGROUND: Mother-to-child transmission (MTCT) is the main cause of HIV-1 infection in children worldwide. Given that the C-type lectin receptor, dendritic cell-specific ICAM-grabbing non-integrin-related (DC-SIGNR, also known as CD209L or liver/lymph node-specific ICAM-grabbing non-integrin (L-SIGN)), can interact with pathogens including HIV-1 and is expressed at the maternal-fetal interface, we hypothesized that it could influence MTCT of HIV-1. METHODS AND FINDINGS: To investigate the potential role of DC-SIGNR in MTCT of HIV-1, we carried out a genetic association study of DC-SIGNR in a well-characterized cohort of 197 HIV-infected mothers and their infants recruited in Harare, Zimbabwe. Infants harbouring two copies of DC-SIGNR H1 and/or H3 haplotypes (H1-H1, H1-H3, H3-H3) had a 3.6-fold increased risk of in utero (IU) (P = 0.013) HIV-1 infection and a 5.7-fold increased risk of intrapartum (IP) (P = 0.025) HIV-1 infection after adjusting for a number of maternal factors. The implicated H1 and H3 haplotypes share two single nucleotide polymorphisms (SNPs) in promoter region (p-198A) and intron 2 (int2-180A) that were associated with increased risk of both IU (P = 0.045 and P = 0.003, respectively) and IP (P = 0.025, for int2-180A) HIV-1 infection. The promoter variant reduced transcriptional activity in vitro. In homozygous H1 infants bearing both the p-198A and int2-180A mutations, we observed a 4-fold decrease in the level of placental DC-SIGNR transcripts, disproportionately affecting the expression of membrane-bound isoforms compared to infant noncarriers (P = 0.011). CONCLUSION: These results suggest that DC-SIGNR plays a crucial role in MTCT of HIV-1 and that impaired placental DC-SIGNR expression increases risk of transmission.

International audience; A new RT-PCR test has been developed to diagnose Chronic bee paralysis virus (CBPV) that is able to detect genetically variable viral isolates. In fact, up to 8.7% divergence between partial nucleotide sequences from viral isolates from French honey bees was highlighted in a preliminary variability study. The previously-described RT-PCR was unable to detect all these viral isolates and RT-PCR diagnosis needed improvement. The new RT-PCR test can detect up to 40% more CBPV isolates.

International audience; A two-step real-time RT-PCR assay, based on TaqMan technology using a fluorescent probe (FAM-TAMRA) was developed to quantify Chronic bee paralysis virus (CBPV) genome in bee samples. Standard curves obtained from a CBPV control RNA and from a plasmid containing a partial sequence of CBPV showed that this assay provided linear detection over a 7-log range (R(2)>0.99) with a limit of detection of 100 copies, and reliable inter-assay and intra-assay reproducibility. Standardisation including RNA purification and cDNAs synthesis was also validated. The CBPV TaqMan methodology was first evaluated by quantifying the CBPV genomic load in bee samples from an experimental infection obtained by topical application. Up to 1.9 x 10(10) CBPV copies per segment of insect body (head, thorax and abdomen) were revealed whereas a lower CBPV genomic load was detected in dissected organs such as mandibular and hypopharyngeal glands, brain and alimentary canal (up to 7.2 x 10(6) CBPV copies). The CBPV genomic loads in different categories of bees from a hive presenting the trembling symptoms typical of Chronic paralysis were then quantified. Significantly higher CBPV loads were found in guard, symptomatic and dead bees (up to 1.9 x 10(13) CBPV copies) than in forager, drones and house bees (up to 3.4 x 10(6) CBPV copies). The results obtained for symptomatic or dead bees support the correlation between high CBPV genomic load and pathology expression. Moreover, the high CBPV genomic load revealed in guard bees highlights the possible pivotal role played by this category of bees in CBPV infection.