A New Derivative of Retro-2 Displays Antiviral Activity against Respiratory Syncytial Virus

Human respiratory syncytial virus (hRSV) is the most common cause of bronchiolitis and pneumonia in newborns, with all children being infected before the age of two. Reinfections are very common throughout life and can cause severe respiratory infections in the elderly and immunocompromised adults. Although vaccines and preventive antibodies have recently been licensed for use in specific subpopulations of patients, there is still no therapeutic treatment commonly available for these infections. Here, we investigated the potential antiviral activity of Retro-2.2, a derivative of the cellular retrograde transport inhibitor Retro-2, against hRSV. We show that Retro-2.2 inhibits hRSV replication in cell culture and impairs the ability of hRSV to form syncytia. Our results suggest that Retro-2.2 treatment affects virus spread by disrupting the trafficking of the viral de novo synthetized F and G glycoproteins to the plasma membrane, leading to a defect in virion morphogenesis. Taken together, our data show that targeting intracellular transport may be an effective strategy against hRSV infection.

Structure of the N-RNA/P interface indicates mode of L/P recruitment to the nucleocapsid of human metapneumovirus

Human metapneumovirus (HMPV) is a major cause of respiratory illness in young children. The HMPV polymerase (L) binds an obligate cofactor, the phosphoprotein (P). During replication and transcription, the L/P complex traverses the viral RNA genome, which is encapsidated within nucleoproteins (N). An essential interaction between N and a C-terminal region of P tethers the L/P polymerase to the template. This N-P interaction is also involved in the formation of cytoplasmic viral factories in infected cells, called inclusion bodies. To define how the polymerase component P recognizes N-encapsidated RNA (N-RNA) we employed cryogenic electron microscopy (cryo-EM) and molecular dynamics simulations, coupled to activity assays and imaging of inclusion bodies in cells. We report a 2.9 Å resolution structure of a triple-complex between multimeric N, bound to both RNA and the C-terminal region of P. Furthermore, we also present cryo-EM structures of assembled N in different oligomeric states, highlighting the plasticity of N. Combined with our functional assays, these structural data delineate in molecular detail how P attaches to N-RNA whilst retaining substantial conformational dynamics. Moreover, the N-RNA-P triple complex structure provides a molecular blueprint for the design of therapeutics to potentially disrupt the attachment of L/P to its template.

Hardening of Respiratory Syncytial Virus Inclusion Bodies by Cyclopamine Proceeds through Perturbation of the Interactions of the M2-1 Protein with RNA and the P Protein

Respiratory syncytial virus (RSV) RNA synthesis takes place in cytoplasmic viral factories also called inclusion bodies (IBs), which are membrane-less organelles concentrating the viral RNA polymerase complex. The assembly of IBs is driven by liquid-liquid phase separation promoted by interactions between the viral nucleoprotein N and the phosphoprotein P. We recently demonstrated that cyclopamine (CPM) inhibits RSV multiplication by disorganizing and hardening IBs. Although a single mutation in the viral transcription factor M2-1 induced resistance to CPM, the mechanism of action of CPM still remains to be characterized. Here, using FRAP experiments on reconstituted pseudo-IBs both in cellula and in vitro, we first demonstrated that CPM activity depends on the presence of M2-1 together with N and P. We showed that CPM impairs the competition between P and RNA binding to M2-1. As mutations on both P and M2-1 induced resistance against CPM activity, we suggest that CPM may affect the dynamics of the M2-1-P interaction, thereby affecting the relative mobility of the proteins contained in RSV IBs. Overall, our results reveal that stabilizing viral protein-protein interactions is an attractive new antiviral approach. They pave the way for the rational chemical optimization of new specific anti-RSV molecules.

Screening antivirals with a mCherry-expressing recombinant bovine respiratory syncytial virus: a proof of concept using cyclopamine

Bovine respiratory syncytial virus (BRSV) is a pathogenic pneumovirus and a major cause of acute respiratory infections in calves. Although different vaccines are available against BRSV, their efficiency remains limited, and no efficient and large-scale treatment exists. Here, we developed a new reverse genetics system for BRSV expressing the red fluorescent protein mCherry, based on a field strain isolated from a sick calf in Sweden. Although this recombinant fluorescent virus replicated slightly less efficiently compared to the wild type virus, both viruses were shown to be sensitive to the natural steroidal alkaloid cyclopamine, which was previously shown to inhibit human RSV replication. Our data thus point to the potential of this recombinant fluorescent BRSV as a powerful tool in preclinical drug discovery to enable high throughput compound screening.

Depletion of TAX1BP1 Amplifies Innate Immune Responses during Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) is the main cause of acute respiratory infections in young children and also has a major impact on the elderly and immunocompromised people. In the absence of a vaccine or efficient treatment, a better understanding of RSV interactions with the host antiviral response during infection is needed. Previous studies revealed that cytoplasmic inclusion bodies (IBs), where viral replication and transcription occur, could play a major role in the control of innate immunity during infection by recruiting cellular proteins involved in the host antiviral response. We recently showed that the morphogenesis of IBs relies on a liquid-liquid-phase separation mechanism depending on the interaction between viral nucleoprotein (N) and phosphoprotein (P). These scaffold proteins are expected to play a central role in the recruitment of cellular proteins to IBs. Here, we performed a yeast two-hybrid screen using RSV N protein as bait and identified the cellular protein TAX1BP1 as a potential partner of this viral protein. This interaction was validated by pulldown and immunoprecipitation assays. We showed that TAX1BP1 suppression has only a limited impact on RSV infection in cell cultures. However, RSV replication is decreased in TAX1BP1-deficient (TAX1BP1 knockout [TAX1BP1KO]) mice, whereas the production of inflammatory and antiviral cytokines is enhanced. In vitro infection of wild-type or TAX1BP1KO alveolar macrophages confirmed that the innate immune response to RSV infection is enhanced in the absence of TAX1BP1. Altogether, our results suggest that RSV could hijack TAX1BP1 to restrain the host immune response during infection. IMPORTANCE Respiratory syncytial virus (RSV), which is the leading cause of lower respiratory tract illness in infants, remains a medical problem in the absence of a vaccine or efficient treatment. This virus is also recognized as a main pathogen in the elderly and immunocompromised people, and the occurrence of coinfections (with other respiratory viruses and bacteria) amplifies the risks of developing respiratory distress. In this context, a better understanding of the pathogenesis associated with viral respiratory infections, which depends on both viral replication and the host immune response, is needed. The present study reveals that the cellular protein TAX1BP1, which interacts with the RSV nucleoprotein N, participates in the control of the innate immune response during RSV infection, suggesting that the N-TAX1BP1 interaction represents a new target for the development of antivirals.

Biochemical characterization of the respiratory syncytial virus N0-P complex in solution

As all the viruses belonging to the Mononegavirales order, the nonsegmented negative-strand RNA genome of respiratory syncytial virus (RSV) is encapsidated by the viral nucleoprotein N. N protein polymerizes along the genomic and anti-genomic RNAs during replication. This requires the maintenance of the neosynthesized N protein in a monomeric and RNA-free form by the viral phosphoprotein P that plays the role of a chaperone protein, forming a soluble N0-P complex. We have previously demonstrated that residues 1-30 of P specifically bind to N0 Here, to isolate a stable N0-P complex suitable for structural studies, we used the N-terminal peptide of P (P40) to purify truncated forms of the N protein. We show that to purify a stable N0-P-like complex, a deletion of the first 30 N-terminal residues of N (NΔ30) is required to impair N oligomerization, whereas the presence of a full-length C-arm of N is required to inhibit RNA binding. We generated structural models of the RSV N0-P with biophysical approaches, including hydrodynamic measurements and small-angle X-ray scattering (SAXS), coupled with biochemical and functional analyses of human RSV (hRSV) NΔ30 mutants. These models suggest a strong structural homology between the hRSV and the human metapneumovirus (hMPV) N0-P complexes. In both complexes, the P40-binding sites on N0 appear to be similar, and the C-arm of N provides a high flexibility and a propensity to interact with the N RNA groove. These findings reveal two potential sites to target on N0-P for the development of RSV antivirals.

RSV hijacks cellular protein phosphatase 1 to regulate M2-1 phosphorylation and viral transcription

Respiratory syncytial virus (RSV) RNA synthesis occurs in cytoplasmic inclusion bodies (IBs) in which all the components of the viral RNA polymerase are concentrated. In this work, we show that RSV P protein recruits the essential RSV transcription factor M2-1 to IBs independently of the phosphorylation state of M2-1. We also show that M2-1 dephosphorylation is achieved by a complex formed between P and the cellular phosphatase PP1. We identified the PP1 binding site of P, which is an RVxF-like motif located nearby and upstream of the M2-1 binding region. NMR confirmed both P-M2-1 and P-PP1 interaction regions in P. When the P–PP1 interaction was disrupted, M2-1 remained phosphorylated and viral transcription was impaired, showing that M2-1 dephosphorylation is required, in a cyclic manner, for efficient viral transcription. IBs contain substructures called inclusion bodies associated granules (IBAGs), where M2-1 and neo-synthesized viral mRNAs concentrate. Disruption of the P–PP1 interaction was correlated with M2-1 exclusion from IBAGs, indicating that only dephosphorylated M2-1 is competent for viral mRNA binding and hence for a previously proposed post-transcriptional function.

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract illness in infants. Since no vaccine and no potent antivirals are available against RSV, it is essential to better understand the mechanisms of viral replication to develop new antiviral strategies. Here we have investigated the mechanisms by which two essential components of the viral RNA polymerase machinery, the phosphoprotein P and the M2-1 transcription factor, interact and function. We identified the amino acid residues of P critical for this interaction and showed that they are required for P recruiting M2-1 to cytoplasmic inclusions, where viral polymerase complex proteins concentrate and viral RNA synthesis occurs. We also showed that M2-1 dephosphorylation, required for viral transcription, is achieved by a complex formed between P and the cellular phosphatase PP1. The region of P binding to PP1 is located nearby and upstream of the M2-1 binding domain. This is the first report showing that the phosphoprotein of a negative strand RNA virus can hijack a cellular phosphatase to modulate the phosphorylation state of its partners. These two P regions interacting with M2-1 and PP1 are also potential targets for future antiviral therapy.

Respiratory Syncytial Virus Infects Regulatory B Cells in Human Neonates via Chemokine Receptor CX3CR1 and Promotes Lung Disease Severity

Respiratory syncytial virus (RSV) is the major cause of lower respiratory tract infections in infants and is characterized by pulmonary infiltration of B cells in fatal cases. We analyzed the B cell compartment in human newborns and identified a population of neonatal regulatory B lymphocytes (nBreg cells) that produced interleukin 10 (IL-10) in response to RSV infection. The polyreactive B cell receptor of nBreg cells interacted with RSV protein F and induced upregulation of chemokine receptor CX3CR1. CX3CR1 interacted with RSV glycoprotein G, leading to nBreg cell infection and IL-10 production that dampened T helper 1 (Th1) cytokine production. In the respiratory tract of neonates with severe RSV-induced acute bronchiolitis, RSV-infected nBreg cell frequencies correlated with increased viral load and decreased blood memory Th1 cell frequencies. Thus, the frequency of nBreg cells is predictive of the severity of acute bronchiolitis disease and nBreg cell activity may constitute an early-life host response that favors microbial pathogenesis.

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Identified a neonatal-specific subset of regulatory B (nBreg) cells in the blood

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Neonatal nBreg cells are infected by RSV via the BCR and CX3CR1

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RSV-infected nBreg cells produce anti-inflammatory IL-10 that dowregulates Th1 cell responses

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Blood nBreg cells are a biomarker of lung disease severity in RSV⁺ patients

New Insights into Structural Disorder in Human Respiratory Syncytial Virus Phosphoprotein and Implications for Binding of Protein Partners

Phosphoprotein is the main cofactor of the viral RNA polymerase of Mononegavirales It is involved in multiple interactions that are essential for the polymerase function. Most prominently it positions the polymerase complex onto the nucleocapsid, but also acts as a chaperone for the nucleoprotein. Mononegavirales phosphoproteins lack sequence conservation, but contain all large disordered regions. We show here that N- and C-terminal intrinsically disordered regions account for 80% of the phosphoprotein of the respiratory syncytial virus. But these regions display marked dynamic heterogeneity. Whereas almost stable helices are formed C terminally to the oligomerization domain, extremely transient helices are present in the N-terminal region. They all mediate internal long-range contacts in this non-globular protein. Transient secondary elements together with fully disordered regions also provide protein binding sites recognized by the respiratory syncytial virus nucleoprotein and compatible with weak interactions required for the processivity of the polymerase.

RSV N-nanorings fused to palivizumab-targeted neutralizing epitope as a nanoparticle RSV vaccine

Respiratory syncytial virus (RSV) is the leading cause of acute respiratory infections in children, yet no vaccine is available. The sole licensed preventive treatment against RSV is composed of a monoclonal neutralizing antibody (palivizumab), which targets a conformational epitope located on the fusion protein (F). Palivizumab reduces the burden of bronchiolitis but does not prevent infection. Thus, the development of RSV vaccines remains a priority. We previously evaluated nanorings formed by RSV nucleoprotein (N) as an RSV vaccine, as well as an immunostimulatory carrier for heterologous antigens. Here, we linked the palivizumab-targeted epitope (called FsII) to N, to generate N-FsII-nanorings. Intranasal N-FsII immunization elicited anti-F antibodies in mice that were non-neutralizing in vitro. Nevertheless, RSV-challenged animals were better protected against virus replication than mice immunized with N-nanorings, especially in the upper airways. In conclusion, an N-FsII-focused vaccine is an attractive candidate combining N-specific cellular immunity and F-specific antibodies for protection.

A Druggable Pocket at the Nucleocapsid/Phosphoprotein Interaction Site of Human Respiratory Syncytial Virus

Presently, respiratory syncytial virus (RSV), the main cause of severe respiratory infections in infants, cannot be treated efficiently with antivirals. However, its RNA-dependent polymerase complex offers potential targets for RSV-specific drugs. This includes the recognition of its template, the ribonucleoprotein complex (RNP), consisting of genomic RNA encapsidated by the RSV nucleoprotein, N. This recognition proceeds via interaction between the phosphoprotein P, which is the main polymerase cofactor, and N. The determinant role of the C terminus of P, and more particularly of the last residue, F241, in RNP binding and viral RNA synthesis has been assessed previously. Here, we provide detailed structural insight into this crucial interaction for RSV polymerase activity. We solved the crystallographic structures of complexes between the N-terminal domain of N (N-NTD) and C-terminal peptides of P and characterized binding by biophysical approaches. Our results provide a rationale for the pivotal role of F241, which inserts into a well-defined N-NTD pocket. This primary binding site is completed by transient contacts with upstream P residues outside the pocket. Based on the structural information of the N-NTD:P complex, we identified inhibitors of this interaction, selected by in silico screening of small compounds, that efficiently bind to N and compete with P in vitro. One of the compounds displayed inhibitory activity on RSV replication, thereby strengthening the relevance of N-NTD for structure-based design of RSV-specific antivirals.

IMPORTANCE

Respiratory syncytial virus (RSV) is a widespread pathogen that is a leading cause of acute lower respiratory infections in infants worldwide. RSV cannot be treated efficiently with antivirals, and no vaccine is presently available, with the development of pediatric vaccines being particularly challenging. Therefore, there is a need for new therapeutic strategies that specifically target RSV. The interaction between the RSV phosphoprotein P and the ribonucleoprotein complex is critical for viral replication. In this study, we identified the main structural determinants of this interaction, and we used them to screen potential inhibitors in silico. We found a family of molecules that were efficient competitors of P in vitro and showed inhibitory activity on RSV replication in cellular assays. These compounds provide a basis for a pharmacophore model that must be improved but that holds promises for the design of new RSV-specific antivirals.

Genetic analysis of sow longevity and sow lifetime reproductive traits using censored data

Sow longevity is a key component for efficient and profitable pig farming; however, approximately 50% of sows are removed annually from a breeding herd. There is no consensus in the scientific literature regarding a definition for sow longevity; however, it has been suggested that it can be measured using several methods such as stayability and economic indicators such as lifetime piglets produced. Sow longevity can be improved by genetic selection; however, it is rarely included in genetic evaluations. One reason is elongated time intervals required to collect complete lifetime data. The effect of genetic parameter estimation software in handling incomplete data (censoring) and possible early indicator traits were evaluated analysing a 30% censored data set (12 725 pedigreed Landrace × Large White sows that included approximately 30% censored data) with DMU6, THRGIBBS1F90 and GIBBS2CEN. Heritability estimates were low for all the traits evaluated. The results show that the binary stayability traits benefited from being analysed with a threshold model compared to analysing with a linear model. Sires were ranked very similarly regardless if the program handled censoring when all available data were included. Accumulated born alive and stayability were good indicators for lifetime born alive traits. Number of piglets born alive within each parity could be used as an early indicator trait for sow longevity.

Vaccine safety and efficacy evaluation of a recombinant bovine respiratory syncytial virus (BRSV) with deletion of the SH gene and subunit vaccines based on recombinant human RSV proteins: N-nanorings, P and M2-1, in calves with maternal antibodies

The development of safe and effective vaccines against both bovine and human respiratory syncytial viruses (BRSV, HRSV) to be used in the presence of RSV-specific maternally-derived antibodies (MDA) remains a high priority in human and veterinary medicine. Herein, we present safety and efficacy results from a virulent BRSV challenge of calves with MDA, which were immunized with one of three vaccine candidates that allow serological differentiation of infected from vaccinated animals (DIVA): an SH gene-deleted recombinant BRSV (ΔSHrBRSV), and two subunit (SU) formulations based on HRSV-P, -M2-1, and -N recombinant proteins displaying BRSV-F and -G epitopes, adjuvanted by either oil emulsion (Montanide ISA71^VG, SUMont) or immunostimulating complex matrices (AbISCO-300, SUAbis). Whereas all control animals developed severe respiratory disease and shed high levels of virus following BRSV challenge, ΔSHrBRSV-immunized calves demonstrated almost complete clinical and virological protection five weeks after a single intranasal vaccination. Although mucosal vaccination with ΔSHrBRSV failed to induce a detectable immunological response, there was a rapid and strong anamnestic mucosal BRSV-specific IgA, virus neutralizing antibody and local T cell response following challenge with virulent BRSV. Calves immunized twice intramuscularly, three weeks apart with SUMont were also well protected two weeks after boost. The protection was not as pronounced as that in ΔSHrBRSV-immunized animals, but superior to those immunized twice subcutaneously three weeks apart with SUAbis. Antibody responses induced by the subunit vaccines were non-neutralizing and not directed against BRSV F or G proteins. When formulated as SUMont but not as SUAbis, the HRSV N, P and M2-1 proteins induced strong systemic cross-protective cell-mediated immune responses detectable already after priming. ΔSHrBRSV and SUMont are two promising DIVA-compatible vaccines, apparently inducing protection by different immune responses that were influenced by vaccine-composition, immunization route and regimen.

Structure and functional analysis of the RNA- and viral phosphoprotein-binding domain of respiratory syncytial virus M2-1 protein

Respiratory syncytial virus (RSV) protein M2-1 functions as an essential transcriptional cofactor of the viral RNA-dependent RNA polymerase (RdRp) complex by increasing polymerase processivity. M2-1 is a modular RNA binding protein that also interacts with the viral phosphoprotein P, another component of the RdRp complex. These binding properties are related to the core region of M2-1 encompassing residues S58 to K177. Here we report the NMR structure of the RSV M2-1(58-177) core domain, which is structurally homologous to the C-terminal domain of Ebola virus VP30, a transcription co-factor sharing functional similarity with M2-1. The partial overlap of RNA and P interaction surfaces on M2-1(58-177), as determined by NMR, rationalizes the previously observed competitive behavior of RNA versus P. Using site-directed mutagenesis, we identified eight residues located on these surfaces that are critical for an efficient transcription activity of the RdRp complex. Single mutations of these residues disrupted specifically either P or RNA binding to M2-1 in vitro. M2-1 recruitment to cytoplasmic inclusion bodies, which are regarded as sites of viral RNA synthesis, was impaired by mutations affecting only binding to P, but not to RNA, suggesting that M2-1 is associated to the holonucleocapsid by interacting with P. These results reveal that RNA and P binding to M2-1 can be uncoupled and that both are critical for the transcriptional antitermination function of M2-1.

Nucleoprotein nanostructures combined with adjuvants adapted to the neonatal immune context: a candidate mucosal RSV vaccine

Background

The human respiratory syncytial virus (hRSV) is the leading cause of severe bronchiolitis in infants worldwide. The most severe RSV diseases occur between 2 and 6 months-of-age, so pediatric vaccination will have to be started within the first weeks after birth, when the immune system is prone to Th2 responses that may turn deleterious upon exposure to the virus. So far, the high risk to prime for immunopathological responses in infants has hampered the development of vaccine. In the present study we investigated the safety and efficacy of ring-nanostructures formed by the recombinant nucleoprotein N of hRSV (N^SRS) as a mucosal vaccine candidate against RSV in BALB/c neonates, which are highly sensitive to immunopathological Th2 imprinting.

Methodology and Principal Findings

A single intranasal administration of N^SRS with detoxified E.coli enterotoxin LT(R192G) to 5–7 day old neonates provided a significant reduction of the viral load after an RSV challenge at five weeks of age. However, neonatal vaccination also generated an enhanced lung infiltration by neutrophils and eosinophils following the RSV challenge. Analysis of antibody subclasses and cytokines produced after an RSV challenge or a boost administration of the vaccine suggested that neonatal vaccination induced a Th2 biased local immune memory. This Th2 bias and the eosinophilic reaction could be prevented by adding CpG to the vaccine formulation, which, however did not prevent pulmonary inflammation and neutrophil infiltration upon viral challenge.

Conclusions/Significance

In conclusion, protective vaccination against RSV can be achieved in neonates but requires an appropriate combination of adjuvants to prevent harmful Th2 imprinting.

The insertion of fluorescent proteins in a variable region of respiratory syncytial virus L polymerase results in fluorescent and functional enzymes but with reduced activities

The respiratory syncytial virus (RSV) Large protein L is the catalytic subunit of the RNA-dependent RNA polymerase complex. Currently, no structural information is available for RSV L. Sequence alignments of L protein from human and bovine strains of RSV revealed the existence of two variable regions, VR1 and VR2. Following comparison with morbillivirus and rhabdovirus L genes, VR2, which is located between domains V and VI, was chosen as an insertion site for sequences encoding the epitope tag HA or the fluorescent proteins eGFP and mCherry. Recombinant tagged-L proteins co-localized with RSV N and P proteins in transfected cells. These recombinant polymerases were shown to be functional using a viral minigenome system assay, their activities being reduced by ~70% compared to the unmodified L polymerase. We have also shown by site-directed mutagenesis that the GDNQ motif (residues 810-813 for the Long strain of HRSV) is essential for L activity.

The 15-Country Collaborative Study of Cancer Risk among Radiation Workers in the Nuclear Industry: estimates of radiation-related cancer risks

A 15-Country collaborative cohort study was conducted to provide direct estimates of cancer risk following protracted low doses of ionizing radiation. Analyses included 407,391 nuclear industry workers monitored individually for external radiation and 5.2 million person-years of follow-up. A significant association was seen between radiation dose and all-cause mortality [excess relative risk (ERR) 0.42 per Sv, 90% CI 0.07, 0.79; 18,993 deaths]. This was mainly attributable to a dose-related increase in all cancer mortality (ERR/Sv 0.97, 90% CI 0.28, 1.77; 5233 deaths). Among 31 specific types of malignancies studied, a significant association was found for lung cancer (ERR/Sv 1.86, 90% CI 0.49, 3.63; 1457 deaths) and a borderline significant (P = 0.06) association for multiple myeloma (ERR/Sv 6.15, 90% CI <0, 20.6; 83 deaths) and ill-defined and secondary cancers (ERR/Sv 1.96, 90% CI -0.26, 5.90; 328 deaths). Stratification on duration of employment had a large effect on the ERR/Sv, reflecting a strong healthy worker survivor effect in these cohorts. This is the largest analytical epidemiological study of the effects of low-dose protracted exposures to ionizing radiation to date. Further studies will be important to better assess the role of tobacco and other occupational exposures in our risk estimates.

Risk of cancer after low doses of ionising radiation: retrospective cohort study in 15 countries

OBJECTIVES

To provide direct estimates of risk of cancer after protracted low doses of ionising radiation and to strengthen the scientific basis of radiation protection standards for environmental, occupational, and medical diagnostic exposures.

DESIGN

Multinational retrospective cohort study of cancer mortality.

SETTING

Cohorts of workers in the nuclear industry in 15 countries.

PARTICIPANTS

407 391 workers individually monitored for external radiation with a total follow-up of 5.2 million person years.

MAIN OUTCOME MEASUREMENTS

Estimates of excess relative risks per sievert (Sv) of radiation dose for mortality from cancers other than leukaemia and from leukaemia excluding chronic lymphocytic leukaemia, the main causes of death considered by radiation protection authorities.

RESULTS

The excess relative risk for cancers other than leukaemia was 0.97 per Sv, 95% confidence interval 0.14 to 1.97. Analyses of causes of death related or unrelated to smoking indicate that, although confounding by smoking may be present, it is unlikely to explain all of this increased risk. The excess relative risk for leukaemia excluding chronic lymphocytic leukaemia was 1.93 per Sv (< 0 to 8.47). On the basis of these estimates, 1-2% of deaths from cancer among workers in this cohort may be attributable to radiation.

CONCLUSIONS

These estimates, from the largest study of nuclear workers ever conducted, are higher than, but statistically compatible with, the risk estimates used for current radiation protection standards. The results suggest that there is a small excess risk of cancer, even at the low doses and dose rates typically received by nuclear workers in this study.

Effects of low doses and low dose rates of external ionizing radiation: cancer mortality among nuclear industry workers in three countries

Studies of the mortality among nuclear industry workforces have been carried out, and nationally combined analyses performed, in the U.S., the UK and Canada. This paper presents the results of internationally combined analyses of mortality data on 95,673 workers (85.4% men) monitored for external exposure to ionizing radiation and employed for 6 months or longer in the nuclear industry of one of the three countries. These analyses were undertaken to obtain a more precise direct assessment of the carcinogenic effects of protracted low-level exposure to external, predominantly gamma, radiation. The combination of the data from the various studies increases the power to study associations between radiation and specific cancers. The combined analyses covered a total of 2,124,526 person-years (PY) at risk and 15,825 deaths, 3,976 of which were due to cancer. There was no evidence of an association between radiation dose and mortality from all causes or from all cancers. Mortality from leukemia, excluding chronic lymphocytic leukemia (CLL)--the cause of death most strongly and consistently related to radiation dose in studies of atomic bomb survivors and other populations exposed at high dose rates--was significantly associated with cumulative external radiation dose (one-sided P value = 0.046; 119 deaths). Among the 31 other specific types of cancer studied, a significant association was observed only for multiple myeloma (one-sided P value = 0.037; 44 deaths), and this was attributable primarily to the associations reported previously between this disease and radiation dose in the Hanford (U.S.) and Sellafield (UK) cohorts. The excess relative risk (ERR) estimates for all cancers excluding leukemia, and leukemia excluding CLL, the two main groupings of causes of death for which risk estimates have been derived from studies of atomic bomb survivors, were -0.07 per Sv [90% confidence interval (CI): -0.4, 0.3] and 2.18 per Sv (90% CI: 0.1, 5.7), respectively. These values correspond to a relative risk of 0.99 for all cancers excluding leukemia and 1.22 for leukemia excluding CLL for a cumulative protracted dose of 100 mSv compared to 0 mSv. These estimates, which did not differ significantly across cohorts or between men and women, are the most comprehensive and precise direct estimates of cancer risk associated with low-dose protracted exposures obtained to date. Although they are lower than the linear estimates obtained from studies of atomic bomb survivors, they are compatible with a range of possibilities, from a reduction of risk at low doses, to risks twice those on which current radiation protection recommendations are based.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of costs of new atherectomy devices and balloon angioplasty for coronary artery disease

The in-hospital cost for 126 consecutive patients undergoing 1-vessel, single-lesion coronary atherectomy (atherectomy group) beginning January 1, 1991, was reviewed (65 directional, 44 rotational, and 17 extractional atherectomies), and compared with the cost for 126 consecutive patients matched by sex and age who underwent 1-vessel, single-lesion standard balloon coronary angioplasty (angioplasty group). The in-hospital cost for each patient was determined using charges divided by a correction factor for each hospital department involved. Six different cost fields were created. The overall cost/charge ratio was 0.72. Angiographic and clinical success was 91% and 90% in the angioplasty group and 93% and 90% in the atherectomy group, respectively. Patients who underwent angioplasty required 1.3 +/- 0.6 devices/procedure, as compared with those who underwent atherectomy (2.4 +/- 1 devices/procedure) (p < 0.0001). The mean cost of angioplasty was $7,301 +/- $4,637 and of atherectomy devices $9,345 +/- $8,856 (28% increase). The difference was principally related to an increase in cost of supplies: angioplasty $2,028 +/- $1,196 versus atherectomy $3,632 +/- $1,525 (79% increase). There were no significant differences in hospitalization cost, procedure-room cost, and pharmacy and laboratory costs. Thus, higher risk morphologic lesions can be approached with new atherectomy devices with clinical and complication rates similar to coronary angioplasty. However, these results were obtained at a 28% increase in cost.

Do patients with less than 'echo-perfect' results from mitral valve repair by intraoperative echocardiography have a different outcome?

BACKGROUND

Not all valve repairs for mitral regurgitation (MR) have a perfect result, with no MR on postpump intraoperative echocardiography. Although more than 2+ MR by postpump echocardiography has led to second pump runs for further surgery in 6% to 8% of our patients, those left with 1+ or 2+ MR, traditionally an acceptable result, have not previously been evaluated for clinical outcome.

METHODS AND RESULTS

Among 530 patients undergoing mitral repair during 1987 to 1989, 76 patients with 1+ or 2+ MR by postpump intraoperative echocardiography were compared with 76 patients who had equivalent age, sex, left ventricular function, and concomitant surgery but who had no MR by postpump echo. In-hospital morbidity measured by the frequency of respiratory complications, strokes, time in intensive care unit, and duration of hospital stay was actually higher in the patients with no MR after repair. Hospital mortality was not significantly different. There were no significant differences in posthospital mortality (4-year survival estimate of 86% in both groups), thromboembolic events, hospitalizations for heart failure, or functional class, although more patients in the group with no MR after repair were using diuretics. There was a trend toward more reoperations in patients with 1+ or 2+ MR compared with those with no MR by intraoperative echocardiography after repair (4-year estimates of freedom from reoperation, 83% versus 94%; adjusted risk ratio, 3.30).

CONCLUSIONS

The presence of 1+ or 2+ MR by postpump intraoperative echocardiography does not confer increased morbidity or mortality. However, the trend toward more reoperations suggests the need for close follow-up for possible recurrence of MR. These data support our low threshold for performing further surgery during second pump runs.

Sapphire ring constriction syndrome

An uncommon case of a partially embedded ring under the skin is presented. A technique for removal is described. All previously reported cases as well as ours occurred in mentally handicapped individuals.