P14.12 Gyriform infiltration as imaging biomarker for adult diffuse astrocytic glioma, IDH wildtype, with molecular features of glioblastoma

BACKGROUND

Diffuse astrocytic gliomas, IDH wildtype, with molecular features of glioblastoma (molecular glioblastomas) are associated with a poor prognosis. We previously found that these tumors frequently display gyriform infiltration, defined as areas of elective cortical hypersignal on MRI FLAIR sequence. The objective of the present study was to assess the diagnostic value of gyriform infiltration as an imaging marker for these tumors.

MATERIAL AND METHODS

MRI scans from 430 patients with newly diagnosed glioma (molecular glioblastoma n = 31, IDH wildtype glioblastoma n = 298, IDH-mutant astrocytoma n = 50, IDH-mutant and 1p19q codeleted oligodendroglioma n= 51) were evaluated for the presence of a gyriform infiltration by 2 independent reviewers. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated to assess the performance of the presence of a gyriform infiltration for identifying molecular glioblastoma.

RESULTS

A gyriform infiltration was observed in 16/31 (52%) patients with a molecular glioblastoma, 40/298 (13%) patients with an IDH-wildtype glioblastoma but in none of the patients with an IDH-mutant astrocytomas or an IDH-mutant and 1p19q codeleted oligodendroglioma. Among the 56 patients with a gyriform infiltration, 54 patients had an IDH wildtype pTERT mutant glioma and 2 an IDH wildtype pTERT wildtype glioma. Interrater agreement was good (κ= 0.68, P < 0.001). Specificity, sensitivity, PPV and NPV of the presence of a gyriform infiltration for the diagnosis of molecular glioblastoma were 90%, 29%, 52% and 96% and for the diagnosis of an IDHwt pTERT mutant glioma were 97%, 15%, 96% and 20%. The presence of a gyriform infiltration was associated with a worse prognosis in the entire cohort (13.6 months vs 29.3 months, P = .001).

CONCLUSION

Gyriform infiltration is a specific imaging marker of molecular glioblastomas and IDH wildtype pTERT mutant diffuse gliomas.

OS02.4.A Molecular characterization of adult cerebellar glioblastomas identifies distinct prognosis subgroups

BACKGROUND

Adult cerebellar glioblastomas (cGBM) are very rare and recent studies have shown that they constitute a heterogeneous group of gliomas. The aim of the present study was to characterize the prevalence and prognostic significance of major driver molecular alterations in a large series of cGBM.

MATERIAL AND METHODS

Adults with histologically proven cGBM diagnosed between 2003 and 2017 were identified from the French brain tumor database and the Club de Neuro-Oncologie of the Société Française de Neurochirurgie. Tumors were reviewed and reclassified according to WHO 2016. Targeted sequencing was performed, including determination of H3F3A, TERTp, IDH1/2, FGFR1, BRAF and EGFR status.

RESULTS

A total of 83 adult patients (median age 57 years) with cGBM (hemispheric n= 47, vermian n=14 or both n=22) were identified. Median overall survival was 10 months. Main molecular alterations observed were TERT promoter, H3F3A K27M, hotspot FGFR1 (N546 and K656), BRAF mutations, EGFR amplification and ATRX loss of expression in 19.2%, 18.8%, 10.9%, 2.6%, 19.5% and 22.7% of patients, respectively. cGBM could be classified into 6 mutually exclusive subgroups associated with age at diagnosis and prognosis: pTERT and/or EGFR amplified tumors (n=22, 26.5%, median age = 62 years, median OS = 4 months), H3K27M-mutant tumors (n=15, 18.1%, median age = 48 years, median OS =8 months), tumors with MAPK pathway activating mutations (FGFR1, BRAF) or occurring in NF1 patients (n=15, 18.1%, median age = 41 years, median OS = 57 months), radiation-induced tumors (n=5, 6%, median age = 47 years, median OS = 5 months), IDH-mutant tumors (n=1) and unclassified tumors (n=25, 30.1%, median age = 63 years, median OS = 17 months). In multivariate analysis, MAPK activating mutations and ATRX loss of expression were independently associated with a better outcome and pTERT/EGFR alterations with a worse outcome.

CONCLUSION

About 18% of tumors diagnosed as cGBM harbor actionable MAPK activating genetic alterations. Targeted sequencing enables to classify these tumors into clinically relevant subgroups.

Miniaturized percutaneous nephrolithotomy versus retrograde intrarenal surgery in the treatment of lower pole renal stones

OBJECTIVES

Miniaturization of percutaneous nephrolithotomy techniques have led to their increased consideration for lower pole renal stones that can prove more challenging to reach using retrograde intrarenal surgery. The objectives of the present study were to evaluate and compare the outcomes of miniaturized percutaneous nephrolithotomy (miniPCNL) and retrograde intrarenal surgery (RIRS) for the treatment of lower pole renal stones.

MATERIALS AND METHODS

A retrospective study was performed in two academic urology departments between January 2016 and June 2019. Patients presenting with one or multiple stones of the lower calyx and/or renal pelvis, between 10 and 40mm based on CT-scan treated by miniPCNL or RIRS were included.

RESULTS

In all, 115 miniPCNL and 118 RIRS procedures were included. The rate of patients with no significant residual fragment (stone free rate) after the first procedure was higher in the miniPCNL group (69% vs. 52% P=0.01), especially for stones>20mm (63% vs. 24% respectively, P<0.001) and stones with a density≥1000HU (69% vs. 42% respectively, P=0.009). The higher stone free rate of miniPCNL was confirmed in multivariate analysis, adjusting for stone size and number of stones, OR 4.02 (95% CI 2.08-8.11, P<0.0001). The overall postoperative complication rate was higher in the miniPCNL group than in the RIRS group (23% vs. 11%, P=0.01). A second intervention for the treatment of residual fragments was necessary for 9.6% of patients in the miniPCNL group versus 30.5% of patients in the RIRS group (P<0.001). Pre-stenting rate and duration of ureteral drainage (2 [1-8] vs. 25 days [7-37], P<0.001) were lower in the miniPCNL group.

CONCLUSIONS

The stone free rate was higher after miniPCNL, especially for stones>20mm and with a density>1000 HU, but was associated with a higher risk of postoperative complications and a longer hospital stay. RIRS resulted in fewer complications at the cost of a higher retreatment rate and longer ureteral stenting.

LEVEL OF EVIDENCE

3.

Evaluation of the immunogenicity and protective efficacy of a recombinant CS6-based ETEC vaccine in an Aotus nancymaae CS6 + ETEC challenge model

Colonization factors or Coli surface antigens (CFs or CS) are important virulence factors of Enterotoxigenic E. coli (ETEC) that mediate intestinal colonization and accordingly are targets of vaccine development efforts. CS6 is a highly prevalent CF associated with symptomatic ETEC infection both in endemic populations and amongst travelers. In this study, we used an Aotus nancymaae non-human primate ETEC challenge model with a CS6 + ETEC strain, B7A, to test the immunogenicity and protective efficacy (PE) of a recombinant CS6-based subunit vaccine. Specifically, we determined the ability of dscCssBA, the donor strand complemented recombinant stabilized fusion of the two subunits of the CS6 fimbriae, CssA and CssB, to elicit protection against CS6 + ETEC mediated diarrhea when given intradermally (ID) with the genetically attenuated double mutant heat-labile enterotoxin LT(R192G/L211A) (dmLT). ID vaccination with dscCssBA + dmLT induced strong serum antibody responses against CS6 and LT. Importantly, vaccination with dscCssBA + dmLT resulted in no observed diarrheal disease (PE = 100%, p = 0.03) following B7A challenge as compared to PBS immunized animals, with an attack rate of 62.5%. These data demonstrate the potential role that CS6 may play in ETEC infection and that recombinant dscCssBA antigen can provide protection against challenge with the homologous CS6 + ETEC strain, B7A, in the Aotus nancymaae diarrheal challenge model. Combined, these data indicate that CS6, and more specifically, a recombinant engineered derivative should be considered for further clinical development.

P14.88 Comparison of SNaPshot PCR and digital droplet PCR for the identification of TERT promoter in non-diagnostic biopsies from glioma patients

BACKGROUND

We previously showed that TERT promotor (pTERT) mutations can be detected in a high proportion of non-diagnostic biopsies from glioma patients using SNaPshot PCR. The aim of the present study was to assess the diagnostic value of digital droplet PCR (ddPCR) in this setting.

MATERIAL AND METHODS

pTERT mutations were retrospectively assessed using SNaPshot PCR and ddPCR in the non-diagnostic biopsies of 14 adult patients who underwent an initial non-diagnostic needle biopsy that led to perform another biopsy that finally demonstrated a pTERT-mutant glioma.

RESULTS

Median age at diagnosis was 69 years and the median interval between the initial and final biopsy was 22 days. The initial biopsy consisted of unspecific infiltrating glial cells (n=10), hemorrhage, necrosis and/or fibrosis (n=4). Using SNaPshot PCR, the final biopsy found an IDH-WT pTERT-mutant glioma in 12 cases (glioblastoma n=12), an IDH-mutant pTERT-mutant oligodendroglioma in one case and an IDH-WT pTERT-WT glioblastoma in one case. Retrospectively, a pTERT mutation was identified by both ddPCR and SNaPshot in the non-diagnostic biopsies in 85% (11 /13) of pTERT mutant-gliomas. No mutation was detected in the non-diagnostic biopsies of IDH-WT pTERT-WT gliomas using either technique. Overall, a pTERT mutation were detected in 79% (11/14) of non-diagnostic biopsies.

CONCLUSION

Digital Droplet PCR, as SNaPshot PCR, enables the identification of pTERT mutations in a high rate of non-diagnostic biopsies from glioma patients. The sensitivity of both techniques seems similar in this setting.

OS5.5 Characteristics of high-grade gliomas with H3 G34 mutation in adults

BACKGROUND

H3 G34-mutant high-grade gliomas occur primarily in children but can also be encountered in adults. The aim of the present study was to describe the characteristics of H3 G34-mutant high-grade gliomas in adults.

MATERIAL AND METHODS

We analysed the characteristics of 17 adult H3 G34-mutant high-grade gliomas and compared them with those of adult grade IV gliomas with H3 K27M mutation (n=21), IDH mutation (n=42) and TERT promoter (pTERT) mutation (n=88).

RESULTS

Median age at diagnosis in H3 G34-mutant gliomas was 25 years (range: 19–33 y). All tumors had a hemispheric location. The radiological presentation was suggestive of a high-grade glioma in 6 patients but in 10 patients it initially suggested another diagnosis due to absent or faint contrast enhancement (n=9) or the presence of an initial intratumoral haemorrhage (n=1). In non- or faint contrast-enhancing cases, diffusion-weighted imaging (DWI) was more helpful to suspect an aggressive tumor than MR spectroscopy and perfusion MRI. All H3 G34-mutant gliomas were classified as IDH wildtype glioblastomas. PNET-like foci were observed in 8 cases and most cases were immunonegative for ATRX (92%) and Olig2 (81%) and demonstrated MGMT promoter methylation (82%). The clinical, radiological and histological presentation of H3 G34-mutant gliomas was different from that of midline H3 K27M-mutant diffuse gliomas and from that of IDH-mutant and IDH-wildtype pTERT-mutant glioblastomas. Median overall survival of G34-mutant gliomas was 23.9 months compared to 19.6 months (p=0.16), 13.7 months (p=0.45) and 58 months (p=2.3x10-10) in H3 K27M-mutant diffuse gliomas, IDHwt pTERT-mutant and IDH-mutant glioblastomas, respectively.

CONCLUSION

Adults H3 G34-mutant high-grade gliomas are associated with distinct characteristics and a poor prognosis. DWI seems helpful to identify cases that present as non-contrast enhancing lesions and can wrongly suggest another diagnosis in these young patients.

[Renal transplantation using a Maastricht category III non-heartbeating donor: First French experience and review of the literature]

In 2015, Annecy Hospital was the first French hospital to perform non-heartbeating organ donation from a Maastricht category III donor (patient awaiting cardiac arrest after withdrawal of treatment). Non-heartbeating organ donation (NHBD), performed in France since 2006, had initially excluded this category, due to ethical questions concerning end of life and treatment withdrawal, as well as technical specificities linked to this procedure. Grenoble University Hospital and Edouard-Herriot Hospital in Lyon then performed the first kidney transplants, with satisfactory outcomes in both recipients. This article presents the details and results of this new experience, challenging both on a deontological and organizational level. Functional outcomes of kidney grafts from NHBD are now well known in the literature and confirm their benefit for patients, with similar results to those from heartbeating donors (HBD). International experiences concerning specifically Maastricht category III NHBD are encouraging and promising.

Cellular and molecular portrait of eleven human glioblastoma cell lines under photon and carbon ion irradiation

This study aimed to examine the cellular and molecular long-term responses of glioblastomas to radiotherapy and hadrontherapy in order to better understand the biological effects of carbon beams in cancer treatment. Eleven human glioblastoma cell lines, displaying gradual radiosensitivity, were irradiated with photons or carbon ions. Independently of p53 or O(6)-methylguanine-DNA methyltransferase(1) status, all cell lines responded to irradiation by a G2/M phase arrest followed by the appearance of mitotic catastrophe, which was concluded by a ceramide-dependent-apoptotic cell death. Statistical analysis demonstrated that: (i) the SF2(2) and the D10(3) values for photon are correlated with that obtained in response to carbon ions; (ii) regardless of the p53, MGMT status, and radiosensitivity, the release of ceramide is associated with the induction of late apoptosis; and (iii) the appearance of polyploid cells after photon irradiation could predict the Relative Biological Efficiency(4) to carbon ions. This large collection of data should increase our knowledge in glioblastoma radiobiology in order to better understand, and to later individualize, appropriate radiotherapy treatment for patients who are good candidates.

Comparison of the efficacy of rotavirus VLP vaccines to a live homologous rotavirus vaccine in a pig model of rotavirus disease

Rotavirus-like particles (VLPs) have shown promise as rotavirus vaccine candidates in mice, rabbits and pigs. In pigs, VLP vaccines reduced rotavirus shedding and disease but only when used in conjunction with live attenuated human rotavirus. Using a porcine rotavirus pig model, rotavirus antigen shedding was reduced by up to 40% after vaccination with VLPs including the neutralizing antigens VP7 and VP8* when used in combination with the adjuvant polyphosphazene poly[di(carbozylatophenoxy)phoshazene] (PCPP). In contrast, complete protection from rotavirus antigen shedding and disease was induced by vaccination with the virulent porcine rotavirus PRV 4F. This is the first study to demonstrate some post-challenge reductions in rotavirus antigen shedding in a pig model of rotavirus disease after vaccination with VLPs without combining with infectious rotavirus.

Endoplasmic reticulum stress induces calcium-dependent permeability transition, mitochondrial outer membrane permeabilization and apoptosis

The accumulation of Ca2+ in the mitochondrial matrix can stimulate oxidative phosphorylation, but can also, at high Ca2+ concentrations, transmit and amplify an apoptotic signal. Here, we characterized the capacity of physiological stimuli (for example, histamine and inositol-1,4,5-triphosphate) and inducers of endoplasmic reticulum (ER) stress (for example, A23187, thapsigargin and tunicamycin) to release Ca2+ from ER stores, induce mitochondrial Ca2+ accumulation, and trigger cell death in human cervix and colon carcinoma cell lines. Sustained Ca2+ accumulation in the mitochondrial matrix induced by ER stress triggered signs of proapoptotic mitochondrial alteration, namely permeability transition, dissipation of the electrochemical potential, matrix swelling, relocalization of Bax to mitochondria and the release of cytochrome c and apoptosis-inducing factor from mitochondria. In contrast, rapid and transient accumulation of Ca2+ induced by physiological stimuli failed to promote mitochondrial permeability transition and to affect cell viability. The specificity of this apoptosis pathway was validated in cells using a panel of pharmacological agents that chelate Ca2+ (BAPTA-AM) or inhibit inositol-1,4,5-trisphosphate receptor (IP(3)R; 2-aminoethoxydiphenyl borate), voltage-dependent anion channel (VDAC) (4,4'-diisothiocyanatostilbene-2,2'-disulfonate, NADH), the permeability transition pore (cyclosporin A and bongkrekic acid), caspases (z-VAD-fmk) and protein synthesis (cycloheximide). Finally, we designed an original cell-free system in which we confronted purified mitochondria and ER vesicles, and identified IP(3)R, VDAC and the permeability transition pore as key proteins in the ER-triggered proapoptotic mitochondrial membrane permeabilization process.

Bone marrow dendritic cells internalize live RF-81 bovine rotavirus and rotavirus-like particles (RF 2/6-GFP-VLP and RF 8*2/6/7-VLP) but are only activated by live bovine rotavirus

Dendritic cells (DC) represent the link between innate and adaptive immunity. They are classified as antigen-presenting cells (APC) and can initiate and modulate the immune response. To investigate the interaction with DCs, live RF-81 bovine rotavirus strain (RFV) and rotavirus-like particles (rota-VLP), RF 2/6-GFP-VLP and rota RF 8*2/6/7-VLP, were added in vitro to murine bone marrow-derived DCs (bmDCs). Live RFV, RF 2/6-GFP-VLP and RF 8*2/6/7-VLP all bound to bmDC and were internalized but only live RFV stimulated phenotypic maturation of the bmDCs as shown by the upregulation of the co-stimulatory molecule CD86. Even though bmDCs internalized RF 2/6-GFP-VLP and RF 8*2/6/7-VLP as efficiently as live RFV, these rota-VLP were not able to activate the cells. Supernatants derived from bmDC cultures treated with live RFV, RF 2/6-GFP-VLP or RF 8*2/6/7-VLP were examined for TNF-alpha production. At 6, 18 and 24 h post-infection, TNF-alpha concentrations were significantly increased in cultures treated with live RFV and rota-VLP compared with untreated cultures. In conclusion, this study showed that live RF-81 bovine rotavirus strain was internalized and induced bmDCs activation, whereas both RF 2/6-GFP-VLP and RF 8*2/6/7-VLP were internalized by bmDCs without triggering their activation.

Structure-function analysis of the interaction between Bax and the cytomegalovirus-encoded protein vMIA

The viral mitochondrial inhibitor of apoptosis (vMIA) encoded by the human cytomegalovirus exerts cytopathic effects and neutralizes the proapoptotic endogenous Bcl-2 family member Bax by recruiting it to mitochondria, inducing its oligomerization and membrane insertion. Using a combination of computational modeling and mutational analyses, we addressed the structure-function relationship of the molecular interaction between the protein Bax and the viral antiapoptotic protein vMIA. We propose a model in which vMIA exhibits an overall fold similar to Bcl-X(L). In contrast to Bcl-X(L), however, this predicted conformation of vMIA does not bind to the BH3 domain of Bax and rather engages in electrostatic interactions that involve a stretch of amino acids between the BH3 and BH2 domains of Bax and an alpha-helical domain located within the previously defined Bax-binding domain of vMIA, between the putative BH1-like and BH2-like domains. According to this model, vMIA is likely to bind Bax preferentially in its membrane-inserted conformation. The capacity of vMIA to cause fragmentation of the mitochondrial network and disorganization of the actin cytoskeleton is independent of its Bax-binding function. We found that Delta131-147 vMIA mutant, which lacks both the Bax-binding function and cell-death suppression but has intact mitochondria-targeting capacity, is similar to vMIA in its ability to disrupt the mitochondrial network and to disorganize the actin cytoskeleton. vMIADelta131-147 is a dominant-negative inhibitor of the antiapoptotic function of wild-type vMIA. Our experiments with vMIADelta131-147 suggest that vMIA forms homo-oligomers, which may engage in cooperative and/or multivalent interactions with Bax, leading to its functional neutralization.

Cytofluorometric quantitation of apoptosis-driven inner mitochondrial membrane permeabilization

The mitochondrial matrix can be specifically labeled by loading cells with calcein and simultaneous quenching of the non-mitochondrial calcein fluorescence with cobalt (Co2+). Positive staining of mitochondria thus requires that the inner mitochondrial membrane functions as a barrier separating calcein (within the matrix) from Co2+ (outside of the matrix). Upon induction of apoptosis, such calcein/Co2+ -labeled cells, demonstrate a decrease in the overall calcein fluorescence resulting from inner mitochondrial membrane permeabilization. This decrease can be quantified by cytofluorometry and can be dissociated from other apoptosis-associated mitochondrial perturbations such as the loss of the mitochondrial transmembrane potential (delta phi m), the local overproduction of re-active oxygen species, and the mitochondrial release of cytochrome c. In some paradigms of apoptosis the loss of calcein/Co2+ (CC) staining can be dissociated from the delta phi m loss, both of which may occur in a caspase-dependent or caspase-independent fashion, depending on the apoptosis inducer. Importantly, inner membrane permeabilization to CC may occur without a permanent delta phi m dissipation in apoptosis, suggesting that transient permeabilization events could participate at the apoptotic cascade. Altogether, our data demonstrate that inner mitochondrial membrane permeabilization constitutes an early event in the apoptotic cascade.

Differential modulation of Bordetella pertussis virulence genes as evidenced by DNA microarray analysis

The production of most factors involved in Bordetella pertussis virulence is controlled by a two-component regulatory system termed BvgA/S. In the Bvg+ phase virulence-activated genes (vags) are expressed, and virulence-repressed genes (vrgs) are down-regulated. The expression of these genes can also be modulated by MgSO(4) or nicotinic acid. In this study we used microarrays to analyse the influence of BvgA/S or modulation on the expression of nearly 200 selected genes. With the exception of one vrg, all previously known vags and vrgs were correctly assigned as such, and the microarray analyses identified several new vags and vrgs, including genes coding for putative autotransporters, two-component systems, extracellular sigma factors, the adenylate cyclase accessory genes cyaBDE, and two genes coding for components of a type III secretion system. For most of the new vrgs and vags the results of the microarray analyses were confirmed by RT-PCR analysis and/or lacZfusions. The degree of regulation and modulation varied between genes, and showed a continuum from strongly BvgA/S-activated genes to strongly BvgA/S-repressed genes. The microarray analyses also led to the identification of a subset of vags and vrgs that are differentially regulated and modulated by MgSO(4) or nicotinic acid, indicating that these genes may be targets for multiple regulatory circuits. For example, the expression of bilA, a gene predicted to encode an intimin-like protein, was found to be activated by BvgA/S and up-modulated by nicotinic acid. Furthermore, surprisingly, in the strain analysed here, which produces only type 2 fimbriae, the fim3 gene was identified as a vrg, while fim2 was confirmed to be a vag.

Mitochondrial permeability transition as a novel principle of hepatorenal toxicity in vivo

Atractyloside (Atr) binds to the adenine nucleotide translocator (ANT) and inhibits ANT-mediated ATP/ADP exchange on the inner mitochondrial membrane. In addition, Atr can trigger opening of a non-specific ion channel, within the ANT-containing permeability transition pore complex (PTPC), which is subject to redox regulation and inhibited by cyclosporin A (CsA). Here we show that the cytotoxic effects of Atr, both in vivo and in vitro, are determined by its capacity to induce PTPC opening and consequent mitochondrial membrane permeabilization (MMP). Thus, the Atr-induced MMP and death of cultured liver cells are both inhibited by CsA as well as by glutathione (GSH) and enhanced by GSH depletion. Similarly, the hepatorenal toxicity of Atr, assessed in vivo, was reduced by treating mice with CsA or a diet rich in sulfur amino acids, a regime which enhances mitochondrial GSH levels. Atr injection induced MMP in hepatocytes and proximal renal tubular cells, and MMP was reduced by either CsA or GSH. Acetaminophen (paracetamol)-induced acute poisoning was also attenuated by CsA and GSH, both in vitro and in vivo. Altogether these data indicate that PTPC-mediated MMP may determine the hepatorenal toxicity of xenobiotics in vivo.

A human rotavirus with rearranged genes 7 and 11 encodes a modified NSP3 protein and suggests an additional mechanism for gene rearrangement

A human rotavirus (isolate M) with an atypical electropherotype with 14 apparent bands of double-stranded RNA was isolated from a chronically infected immunodeficient child. MA-104 cell culture adaptation showed that the M isolate was a mixture of viruses containing standard genes (M0) or rearranged genes: M1 (containing a rearranged gene 7) and M2 (containing rearranged genes 7 and 11). The rearranged gene 7 of virus M1 (gene 7R) was very unusual because it contained two complete open reading frames (ORF). Moreover, serial propagation of virus M1 in cell culture indicated that gene 7R rapidly evolved, leading to a virus with a deleted gene 7R (gene 7RDelta). Gene 7RDelta coded for a modified NSP3 protein (NSP3m) of 599 amino acids (aa) containing a repetition of aa 8 to 296. The virus M3 (containing gene 7RDelta) was not defective in cell culture and actually produced NSP3m. The rearranged gene 11 (gene 11R) had a more usual pattern, with a partial duplication leading to a normal ORF followed by a long 3' untranslated region. The rearrangement in gene 11R was almost identical to some of those previously described, suggesting that there is a hot spot for gene rearrangements at a specific location on the sequence. It has been suggested that in some cases the existence of short direct repeats could favor the occurrence of rearrangement at a specific site. The computer modeling of gene 7 and 11 mRNAs led us to propose a new mechanism for gene rearrangements in which secondary structures, besides short direct repeats, might facilitate and direct the transfer of the RNA polymerase from the 5' to the 3' end of the plus-strand RNA template during the replication step.

Cap-Poly(A) synergy in mammalian cell-free extracts. Investigation of the requirements for poly(A)-mediated stimulation of translation initiation

The 5' cap and 3' poly(A) tail of eukaryotic mRNAs cooperate to stimulate synergistically translation initiation in vivo, a phenomenon observed to date in vitro only in translation systems containing endogenous competitor mRNAs. Here we describe nuclease-treated rabbit reticulocyte lysates and HeLa cell cytoplasmic extracts that reproduce cap-poly(A) synergy in the absence of such competitor RNAs. Extracts were rendered poly(A)-dependent by ultracentrifugation to partially deplete them of ribosomes and associated initiation factors. Under optimal conditions, values for synergy in reticulocyte lysates approached 10-fold. By using this system, we investigated the molecular mechanism of poly(A) stimulation of translation. Maximal cap-poly(A) cooperativity required the integrity of the eukaryotic initiation factor 4G-poly(A)-binding protein (eIF4G-PABP) interaction, suggesting that synergy results from mRNA circularization. In addition, polyadenylation stimulated uncapped cellular mRNA translation and that driven by the encephalomyocarditis virus internal ribosome entry segment (IRES). These effects of poly(A) were also sensitive to disruption of the eIF4G-PABP interaction, suggesting that 5'-3' end cross-talk is functionally conserved between classical mRNAs and an IRES-containing mRNA. Finally, we demonstrate that a rotaviral non-structural protein that evicts PABP from eIF4G is capable of provoking the shut-off of host cell translation seen during rotavirus infection.

Allelic diversity of the two transferrin binding protein B gene isotypes among a collection of Neisseria meningitidis strains representative of serogroup B disease: implication for the composition of a recombinant TbpB-based vaccine

The distribution of the two isotypes of tbpB in a collection of 108 serogroup B meningococcal strains belonging to the four major clonal groups associated with epidemic and hyperendemic disease (the ET-37 complex, the ET-5 complex, lineage III, and cluster A4) was determined. Isotype I strains (with a 1.8-kb tbpB gene) was less represented than isotype II strains (19.4 versus 80.6%). Isotype I was restricted to the ET-37 complex strains, while isotype II was found in all four clonal complexes. The extent of the allelic diversity of tbpB in these two groups was studied by PCR restriction analysis and sequencing of 10 new tbpB genes. Four major tbpB gene variants were characterized: B16B6 (representative of isotype I) and M982, BZ83, and 8680 (representative of isotype II). The relevance of these variants was assessed at the antigenic level by the determination of cross-bactericidal activity of purified immunoglobulin G preparations raised to the corresponding recombinant TbpB (rTbpB) protein against a panel of 27 strains (5 of isotype I and 22 of isotype II). The results indicated that rTbpB corresponding to each variant was able to induce cross-bactericidal antibodies. However, the number of strains killed with an anti-rTbpB serum was slightly lower than that obtained with an anti-TbpA(+)B complex. None of the sera tested raised against an isotype I strain was able to kill an isotype II strain and vice versa. None of the specific antisera tested (anti-rTbpB or anti-TbpA(+)B complex) was able to kill all of the 22 isotype II strains tested. Moreover, using sera raised against the C-terminus domain of TbpB M982 (amino acids 352 to 691) or BZ83 (amino acids 329 to 669) fused to the maltose-binding protein, cross-bactericidal activity was detected against 12 and 7 isotype II strains, respectively, of the 22 tested. These results suggest surface accessibility of the C-terminal end of TbpB. Altogether, these results show that although more than one rTbpB will be required in the composition of a TbpB-based vaccine to achieve a fully cross-bactericidal activity, rTbpB and its C terminus were able by themselves to induce cross-bactericidal antibodies.

Efficient translation of rotavirus mRNA requires simultaneous interaction of NSP3 with the eukaryotic translation initiation factor eIF4G and the mRNA 3' end

In contrast to the vast majority of cellular proteins, rotavirus proteins are translated from capped but nonpolyadenylated mRNAs. The viral nonstructural protein NSP3 specifically binds the 3'-end consensus sequence of viral mRNAs and interacts with the eukaryotic translation initiation factor eIF4G. Here we show that expression of NSP3 in mammalian cells allows the efficient translation of virus-like mRNA. A synergistic effect between the cap structure and the 3' end of rotavirus mRNA was observed in NSP3-expressing cells. The enhancement of viral mRNA translation by NSP3 was also observed in a rabbit reticulocyte lysate translation system supplemented with recombinant NSP3. The use of NSP3 mutants indicates that its RNA- and eIF4G-binding domains are both required to enhance the translation of viral mRNA. The results reported here show that NSP3 forms a link between viral mRNA and the cellular translation machinery and hence is a functional analogue of cellular poly(A)-binding protein.

Cleavage of polypeptide chain initiation factor eIF4GI during apoptosis in lymphoma cells: characterisation of an internal fragment generated by caspase-3-mediated cleavage

Polypeptide chain initiation factor eIF4GI undergoes caspase-mediated degradation during apoptosis to give characteristic fragments. The most prominent of these has an estimated mass of approximately 76 kDa (Middle-Fragment of Apoptotic cleavage of eIF4G; M-FAG). Subcellular fractionation of the BJAB lymphoma cell line after induction of apoptosis indicates that M-FAG occurs in both ribosome-bound and soluble forms. Affinity chromatography on m7GTP-Sepharose shows that M-FAG retains the ability of eIF4GI to associate with both the mRNA cap-binding protein eIF4E and initiation factor eIF4A and that the ribosome-bound form of M-FAG is also present as a complex with eIF4E and eIF4A. These data suggest that the binding sites for eIF4E, eIF4A and eIF3 on eIF4GI are retained in the caspase-generated fragment. M-FAG is also a substrate for cleavage by the Foot-and-Mouth-Disease Virus-encoded L protease. These properties, together with the pattern of recognition by a panel of antibodies, define the origin of the apoptotic cleavage fragment. N-terminal sequencing of the products of caspase-3-mediated eIF4GI cleavage has identified the major cleavage sites. The pattern of eIF4GI degradation and the possible roles of the individual cleavage products in cells undergoing apoptosis are discussed.