RESUMEN

The relevance of particle-overload related lung tumors in rats for human risk assessment following chronic inhalation exposures to poorly soluble particulates (PSP) has been a controversial issue for more than three decades. In 1998, an ILSI (International Life Sciences) Working Group of health scientists was convened to address this issue of applicability of experimental study findings of lung neoplasms in rats for lifetime-exposed production workers to PSPs. A full consensus view was not reached by the Workshop participants, although it was generally acknowledged that the findings of lung tumors in rats following chronic inhalation, particle-overload PSP exposures occurred only in rats and no other tested species; and that there was an absence of lung cancers in PSP-exposed production workers. Since the publication of the ILSI Workshop report in 2000, there have been important new data published on the human relevance issue. A thorough and comprehensive review of the health effects literature on poorly soluble particles/lung overload was undertaken and published by an ECETOC (European Centre for Ecotoxicology and Toxicology of Chemicals) Task Force in 2013. One of the significant conclusions derived from that technical report was that the rat is unique amongst all species in developing lung tumors under chronic inhalation overload exposures to PSPs. Accordingly, the objective of this review is to provide important insights on the fundamental differences in pulmonary responses between experimentally-exposed rats, other experimental species and occupationally-exposed humans. Briefly, five central factors are described by the following issues. Focusing on these five interrelated/convergent factors clearly demonstrate an inappropriateness in concluding that the findings of lung tumors in rats exposed chronically to high concentrations of PSPs are accurate representations of the risks of lung cancer in PSP-exposed production workers. The most plausible conclusion that can be reached is that results from chronic particle-overload inhalation studies with PSPs in rats have no relevance for determining lung cancer risks in production workers exposed for a working lifetime to these poorly soluble particulate-types.

Asunto(s)

Contaminantes Atmosféricos/toxicidad , Neoplasias Pulmonares/patología , Material Particulado/toxicidad , Animales , Humanos , Neoplasias Pulmonares/inducido químicamente , Neoplasias Pulmonares/epidemiología , Ratas , Medición de Riesgo , Hollín/toxicidad , Especificidad de la Especie , Titanio/toxicidad

RESUMEN

The uncertainty factor concept is integrated into health risk assessments for all aspects of public health practice, including by most organizations that derive occupational exposure limits. The use of uncertainty factors is predicated on the assumption that a sufficient reduction in exposure from those at the boundary for the onset of adverse effects will yield a safe exposure level for at least the great majority of the exposed population, including vulnerable subgroups. There are differences in the application of the uncertainty factor approach among groups that conduct occupational assessments; however, there are common areas of uncertainty which are considered by all or nearly all occupational exposure limit-setting organizations. Five key uncertainties that are often examined include interspecies variability in response when extrapolating from animal studies to humans, response variability in humans, uncertainty in estimating a no-effect level from a dose where effects were observed, extrapolation from shorter duration studies to a full life-time exposure, and other insufficiencies in the overall health effects database indicating that the most sensitive adverse effect may not have been evaluated. In addition, a modifying factor is used by some organizations to account for other remaining uncertainties-typically related to exposure scenarios or accounting for the interplay among the five areas noted above. Consideration of uncertainties in occupational exposure limit derivation is a systematic process whereby the factors applied are not arbitrary, although they are mathematically imprecise. As the scientific basis for uncertainty factor application has improved, default uncertainty factors are now used only in the absence of chemical-specific data, and the trend is to replace them with chemical-specific adjustment factors whenever possible. The increased application of scientific data in the development of uncertainty factors for individual chemicals also has the benefit of increasing the transparency of occupational exposure limit derivation. Improved characterization of the scientific basis for uncertainty factors has led to increasing rigor and transparency in their application as part of the overall occupational exposure limit derivation process.

Asunto(s)

Exposición Profesional/normas , Toxicología/métodos , Animales , Humanos , Nivel sin Efectos Adversos Observados , Medición de Riesgo , Especificidad de la Especie , Incertidumbre

RESUMEN

Human biomonitoring (HBM) is a widely accepted tool to aid assessment of chemical uptake in risk assessment. However, our understanding of the biological relevance of the results of HBM can be restricted, due in some part to the limited information on background environmental exposures and biomarker concentrations in the general population. The study described here specifically addresses the question of what constitutes normal background levels in the UK population of a number of biomarkers (the chemical itself or one of its stable metabolites) for a variety of environmental chemicals that are frequently encountered because of their widespread use. The environmental chemicals selected for this study were benzene, chlorinated hydrocarbons, dithiocarbamates, cadmium, mercury, naphthalene, diethylhexyl phthalate, synthetic pyrethroids and xylene. Volunteers (n=436) were randomly sought by a postal survey based on the UK Electoral Register. Participants were asked to complete a questionnaire and provide a urine sample. The overall response rate was 7.5%, with volunteers being recruited from all areas of the UK including, England, Scotland, Wales and Northern Ireland. Study participants were adults and comprised 45% male and 55% females. We have conducted a simple, postal-based, cost-effective study and generated similar reference values to very large surveys such as NHANES. This demonstrates that large investigations may not be necessary to get a reasonable idea of environmental exposures, especially in initial 'screening-type' investigations to identify particular exposures of concern or to demonstrate that exposures are reassuring low and that no further survey data needs to be gathered.

Asunto(s)

Contaminantes Ambientales/orina , Encuestas Epidemiológicas , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Creatinina/orina , Monitoreo del Ambiente , Femenino , Humanos , Masculino , Metales/orina , Persona de Mediana Edad , Naftalenos/orina , Plaguicidas/orina , Ácidos Ftálicos/orina , Valores de Referencia , Solventes/análisis , Reino Unido , Adulto Joven

RESUMEN

Mercury has long been recognised as toxic, principally in relation to its effects on humans following acute or prolonged high-level occupational exposures and, in the latter half of the last century, from a number of environmental incidents. Recognised target organs are the kidneys, central nervous system and thyroid glands. Recently concern has grown about the potential risks to the human population from current background environmental levels, leading bodies such as the World Health Organisation to call for the reduction or, wherever possible, elimination of the use of mercury. This review considers the strength of the epidemiological evidence on the effects of prolonged low-level exposure to the various forms of mercury. The limited research base suggests that several of the potential targets of long-term environmental exposure to mercury are similar to those occurring from occupational exposure including the renal, cardiovascular and immune systems. However, the evidence also suggests that, particularly in the case of organic mercury compounds, the most sensitive endpoint is central nervous system toxicity, especially in relation to exposure during the in utero period and childhood. It also appears that those human populations which have traditionally consumed diets high in seafoods are at greatest risk. While the extent of risk to the general population that may arise from existing environmental exposure levels appears limited, this conclusion is based on an incomplete dataset and therefore the general consensus view that exposure to mercury in its various forms should be minimised where practical, appears to be justified. A number of potential areas of further research are suggested as being pre-requisite to the development of a more rigorous risk assessment.

Asunto(s)

Exposición a Riesgos Ambientales/efectos adversos , Contaminantes Ambientales/envenenamiento , Intoxicación por Mercurio/etiología , Humanos

RESUMEN

p101, the regulatory subunit of phosphatidylinositol-3-kinase-gamma (PI3Kgamma), was recently reported as a common site of retroviral insertion in T-cell lymphomas induced in mice by MoFe2-MuLV, a unique recombinant gammaretrovirus. The common interruption of p101 by retroviral integration suggests that the locus encodes an oncogene whose altered expression is related to the induction of T-cell malignancy. To examine a possible role in the malignant process, p101 was overexpressed in human T-cell lines Molt-4 and Jurkat. Transient overexpression of p101 induced apoptosis in recipient cells; however, stable expression could be established in cells that expressed moderate levels of p101. Constitutive p101 overexpression in those cells conferred significant protection against ultraviolet-induced apoptosis. Protection against apoptotic induction was attributed to p101-mediated activation of the Akt pathway. Constitutive overexpression of p101 enhanced the activity of p110gamma and further sensitized it to activation upon stimulation of G protein-coupled receptor. These findings are the first to implicate altered expression of p101 in malignancy, specifically in T-cell lymphoma. The findings further provide insight into the regulation of p110gamma, indicating that the stoichiometry of p110gamma and p101 are important in regulating PI3Kgamma signaling.

Asunto(s)

Apoptosis/fisiología , Supervivencia Celular/fisiología , Fosfatidilinositol 3-Quinasas/metabolismo , Linfocitos T/metabolismo , Apoptosis/efectos de la radiación , Proteínas Bacterianas/genética , Supervivencia Celular/efectos de la radiación , Fosfatidilinositol 3-Quinasa Clase Ib , Citometría de Flujo , Humanos , Immunoblotting , Isoenzimas/genética , Isoenzimas/metabolismo , Células Jurkat/metabolismo , Células Jurkat/patología , Proteínas Luminiscentes/genética , Fosfatidilinositol 3-Quinasas/genética , Fosforilación , Proteínas Proto-Oncogénicas c-akt/metabolismo , Transducción de Señal , Linfocitos T/patología , Linfocitos T/efectos de la radiación , Rayos Ultravioleta

RESUMEN

The use of biomarkers is now an accepted measure of chemical uptake (possibly exposure) in risk assessment. However, information on background exposures and biomarker concentrations of many environmental chemicals in the general UK population is limited. This study aims to determine reference ranges for eleven biomarkers of chemical exposure, measurable in urine, within the general adult UK population. The study will involve 400 volunteers throughout the UK and is currently underway. Described here is a pilot study, carried out during August and September 2005 to test the study methodology. The initial results of the postal survey and urinary concentrations for cadmium (UCd) and mercury (UHg) are reported. A total of 78 individuals were recruited by post from the UK Electoral Register, to take part in the pilot study. Participants were asked to complete a questionnaire and provide a urine sample. The overall response rate was 16%, of which 60.3% were female and 39.7% male. Those living in suburban areas accounted for 60% of respondents, current smokers 12.8% and vegetarians 1.3%. Levels of UCd were higher in females compared to males and smoking status influenced levels; smokers displayed higher levels of UCd than individuals who had previously smoked or who had never smoked. The mean, median and range of UHg was 1.12, 0.55 (

Asunto(s)

Biomarcadores/orina , Cadmio/orina , Monitoreo del Ambiente/métodos , Mercurio/orina , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Exposición a Riesgos Ambientales/análisis , Femenino , Encuestas Epidemiológicas , Humanos , Masculino , Persona de Mediana Edad , Proyectos Piloto , Servicios Postales , Valores de Referencia , Medición de Riesgo , Factores Sexuales , Fumar/orina , Reino Unido

RESUMEN

Rhesus rhadinovirus (RRV) infection was quantified in peripheral blood mononuclear cells (PBMC) from healthy and simian immunodeficiency virus (SIV)-infected rhesus macaques (Macaca mulatta) at the Tulane National Primate Research Center and in a large collection of simian acquired immunodeficiency syndrome--(SAIDS)-associated lymphomas. Quantification of RRV load was performed by real-time PCR using amplification primers specific for the RRV interleukin-6 homologue (RRV vIL-6). RRV infection was detected infrequently and at low levels in PBMC of randomly selected healthy animals. Examination of longitudinally collected PBMC from 22 SIV-infected animals throughout progression to SAIDS revealed similarly low RRV loads that sometimes increased with advancing disease. RRV infection was detected more frequently in the peripheral blood of SIV-infected animals than in healthy animals. Examination of SAIDS-associated lymphomas showed that RRV is rare within the tumor mass, likely representing infection in an occasional tumor-infiltrating cell or contaminating blood. The results indicate that RRV infection in PBMC is not predictive of, and is apparently not required for, development of lymphoma or hyperplastic lymphadenopathy in SIV-infected animals at TNPRC.

Asunto(s)

Infecciones por Herpesviridae/virología , Macaca mulatta/virología , Enfermedades de los Monos/virología , Rhadinovirus , Síndrome de Inmunodeficiencia Adquirida del Simio/virología , Infecciones Tumorales por Virus/virología , Animales , ADN Viral/metabolismo , Femenino , Estudios Longitudinales , Linfoma/virología , Masculino , Reacción en Cadena de la Polimerasa , Síndrome de Inmunodeficiencia Adquirida del Simio/complicaciones , Virus de la Inmunodeficiencia de los Simios , Carga Viral

RESUMEN

This paper is one of several prepared under the project "Food Safety In Europe: Risk Assessment of Chemicals in Food and Diet" (FOSIE), a European Commission Concerted Action Programme, organised by the International Life Sciences Institute, Europe (ILSI). The aim of the FOSIE project is to review the current state of the science of risk assessment of chemicals in food and diet, by consideration of the four stages of risk assessment, that is, hazard identification, hazard characterisation, exposure assessment and risk characterisation. The contribution of animal-based methods in toxicology to hazard identification of chemicals in food and diet is discussed. The importance of first applying existing technical and chemical knowledge to the design of safety testing programs for food chemicals is emphasised. There is consideration of the presently available and commonly used toxicity testing approaches and methodologies, including acute and repeated dose toxicity, reproductive and developmental toxicity, neurotoxicity, genotoxicity, carcinogenicity, immunotoxicity and food allergy. They are considered from the perspective of whether they are appropriate for assessing food chemicals and whether they are adequate to detect currently known or anticipated hazards from food. Gaps in knowledge and future research needs are identified; research on these could lead to improvements in the methods of hazard identification for food chemicals. The potential impact of some emerging techniques and toxicological issues on hazard identification for food chemicals, such as new measurement techniques, the use of transgenic animals, assessment of hormone balance and the possibilities for conducting studies in which common human diseases have been modelled, is also considered.

Asunto(s)

Exposición a Riesgos Ambientales/efectos adversos , Análisis de los Alimentos , Contaminación de Alimentos/prevención & control , Sustancias Peligrosas/toxicidad , Modelos Animales , Toxicología/métodos , Animales , Alimentos , Contaminación de Alimentos/análisis , Enfermedades Transmitidas por los Alimentos/prevención & control , Humanos , Nivel sin Efectos Adversos Observados , Medición de Riesgo , Gestión de Riesgos , Seguridad

RESUMEN

BACKGROUND: Prior educational interventions to increase seeking evidence by medical students have been unsuccessful. METHODS: We report two quasirandomized controlled trials to increase seeking of medical evidence by third-year medical students. In the first trial (1997-1998), we placed computers in clinical locations and taught their use in a 6-hour course. Based on negative results, we created SUMSearch, an Internet site that automates searching for medical evidence by simultaneous meta-searching of MEDLINE and other sites. In the second trial (1999-2000), we taught SUMSearch's use in a 5(1/2)-hour course. Both courses were taught during the medicine clerkship. For each trial, we surveyed the entire third-year class at 6 months, after half of the students had taken the course (intervention group). The students who had not received the intervention were the control group. We measured self-report of search frequency and satisfaction with search quality and speed. RESULTS: The proportion of all students who reported searching at least weekly for medical evidence significantly increased from 19% (1997-1998) to 42% (1999-2000). The proportion of all students who were satisfied with their search results increased significantly between study years. However, in neither study year did the interventions increase searching or satisfaction with results. Satisfaction with the speed of searching was 27% in 1999-2000. This did not increase between studies years and was not changed by the interventions. CONCLUSION: None of our interventions affected searching habits. Even with automated searching, students report low satisfaction with search speed. We are concerned that students using current strategies for seeking medical evidence will be less likely to seek and appraise original studies when they enter medical practice and have less time.

Asunto(s)

Capacitación de Usuario de Computador , Bases de Datos Bibliográficas/estadística & datos numéricos , Educación de Pregrado en Medicina , Almacenamiento y Recuperación de la Información/estadística & datos numéricos , Informática Médica/educación , Medicina Basada en la Evidencia , Medicina Familiar y Comunitaria/educación , Humanos , Almacenamiento y Recuperación de la Información/métodos , Medicina Interna/educación , Internet , Estudiantes de Medicina , Enseñanza , Texas

Asunto(s)

Infecciones Oportunistas Relacionadas con el SIDA/veterinaria , Neoplasias del Sistema Nervioso Central/patología , Neoplasias del Sistema Nervioso Central/veterinaria , VIH , Linfoma Relacionado con SIDA/patología , Linfoma Relacionado con SIDA/veterinaria , Macaca fascicularis , Macaca mulatta , Enfermedades de los Monos/patología , Virus de la Inmunodeficiencia de los Simios , Infecciones Tumorales por Virus/veterinaria , Animales , Linfocitos B/patología , Linfocitos B/virología , Linfoma de Burkitt/patología , Linfoma de Burkitt/veterinaria , Neoplasias del Sistema Nervioso Central/etiología , Modelos Animales de Enfermedad , Herpesvirus Humano 8 , Humanos , Lymphocryptovirus , Linfoma Relacionado con SIDA/etiología , Linfoma Folicular/patología , Linfoma Folicular/veterinaria , Linfoma de Células B Grandes Difuso/patología , Linfoma de Células B Grandes Difuso/veterinaria , Linfoma Inmunoblástico de Células Grandes/patología , Linfoma Inmunoblástico de Células Grandes/veterinaria , Enfermedades de los Monos/etiología , Enfermedades de los Monos/virología , Rhadinovirus , Síndrome de Inmunodeficiencia Adquirida del Simio/complicaciones , Síndrome de Inmunodeficiencia Adquirida del Simio/patología , Síndrome de Inmunodeficiencia Adquirida del Simio/virología , Coloración y Etiquetado

RESUMEN

Genetic variation of SIV env during the course of infection provides a large population pool that is continually shaped by selective forces in vivo and may influence the development of clinical disease. SAIDS-associated lymphoma (SAL) in the SIV-infected macaque is typically a clonal or oligoclonal mass of B cell origin, extranodal in anatomic distribution, in which SIV is restricted largely to infiltrating macrophages. To explore the degree of genetic variation in SIV env represented in SAL, a 480-bp DNA fragment containing the V1 region was PCR amplified from seven cases of SAL and from a nonneoplastic lymph node of an SIV-infected macaque. The nucleotide sequence of the V1 region was determined from at least 10 clones from multiple independent amplification reactions of each tissue. Overall, the degree of V1 variability within lymphomas was found not to be restricted but to resemble the heterogeneity reported in SIV-infected lymphoid and other tissues. V1 variation in the nonneoplastic lymph node was unexpectedly limited, perhaps related to the unusual disease condition associated with SAIDS in that animal. Unlike observations from SIV-infected tissues of animals without neoplastic disease, no increase was detected in the number of O- or N-linked glycosylation sites in the V1 regions isolated from lymphomas as compared with the original inoculum. These findings suggest that, within the microenvironment of the lymphoma, the immune evasion conferred by increased glycosylation may offer little selective advantage.

Asunto(s)

Genes env , Linfoma/virología , Síndrome de Inmunodeficiencia Adquirida del Simio/virología , Virus de la Inmunodeficiencia de los Simios/genética , Algoritmos , Animales , Variación Genética , Macaca fascicularis , Macaca mulatta , Datos de Secuencia Molecular , Alineación de Secuencia , Análisis de Secuencia de Proteína , Síndrome de Inmunodeficiencia Adquirida del Simio/patología

RESUMEN

A time course analysis was performed to identify the sites of formation and timing of appearance of polytropic recombinant viruses following infection of NIH/Swiss mice with the murine retrovirus SL3-3 murine leukemia virus (SL3) or with a weakly pathogenic mutant termed SL3DeltaMyb5. The results indicated that (i) polytropic recombinant viruses occur initially in the thymus of SL3-infected animals, (ii) the timing of appearance of polytropic recombinants in bone marrow is not consistent with their participation in the previously reported formation of transplantable tumor-forming cells at 3 to 4 week postinoculation, and (iii) the efficient generation of recombinant virus is correlated with efficient tumor induction.

Asunto(s)

Virus de la Leucemia Murina/aislamiento & purificación , Leucemia Experimental/virología , Infecciones por Retroviridae/virología , Infecciones Tumorales por Virus/virología , Animales , Médula Ósea/virología , ADN Viral/análisis , Ratones , Recombinación Genética , Bazo/virología , Factores de Tiempo

RESUMEN

Conditions associated with abnormal B-cell proliferation have an increased incidence in the HIV-infected population. A longitudinal study conducted at the Tulane Regional Primate Research Center has followed more than 1,000 rhesus macaques infected with simian-immunodeficiency virus (SIV) since 1984. While spontaneous B-cell malignancy in SIV-negative macaques has not been reported, 42 cases of SIV-associated-lymphoma (SAL) have been documented in this cohort. Recently we identified a single case of B-cell leukemia, first suggested by clinical abnormalities and confirmed and further characterized by molecular analysis. The case is important because it models the occurrence of B-cell leukemia in the human AIDS patient and because it extends our understanding of the B-cell lymphoproliferative diseases associated with AIDS.

Asunto(s)

Leucemia de Células B/veterinaria , Macaca mulatta/virología , Síndrome de Inmunodeficiencia Adquirida del Simio/complicaciones , Virus de la Inmunodeficiencia de los Simios/patogenicidad , Animales , Células Clonales/patología , ADN Viral/análisis , Femenino , Reordenamiento Génico de Cadena Pesada de Linfocito B , Infecciones por Herpesviridae/complicaciones , Infecciones por Herpesviridae/veterinaria , Leucemia de Células B/etiología , Estudios Longitudinales , Lymphocryptovirus/aislamiento & purificación , Linfoma de Células B/etiología , Linfoma de Células B/veterinaria , Infección por Mycobacterium avium-intracellulare/complicaciones , Reacción en Cadena de la Polimerasa , Infecciones Tumorales por Virus/complicaciones , Infecciones Tumorales por Virus/veterinaria

RESUMEN

Chromium in the hexavalent form, Cr(VI), has long been recognized as a carcinogen and there is concern as to the effects of continuous low-level exposure to chromium both occupationally and environmentally. This review summarizes the available exposure data and known health effects and evaluates the potential risk to human health in the United Kingdom. Chromium emissions to the environment in the United Kingdom are predominantly derived from fuel combustion, waste incineration, and industrial processes. The less toxic trivalent form of chromium [Cr(III)] is dominant in most environmental compartments, and any Cr(VI), the more toxic form, that is emitted to the environment can be reduced to Cr(III). Food is a major source of exposure to chromium, and estimated daily oral intakes for infants (1 yr), children (11 yr), and adults are 33-45, 123-171, and 246-343 micrograms/person/d, respectively. Soil ingestion, particularly common in young children, can contribute to oral intake. Inhalation is a minor route of exposure for the general population. Average daily inhalation intakes in infants can range from 0.004 microgram/d for rural infants to 0.14 microgram/d for urban infants who are passively exposed to tobacco smoke, whereas adults who live in industrialized areas and smoke may take up between 2 and 12 micrograms/d. The most serious health effect associated with Cr(VI) is lung cancer, which has been associated with some occupational exposure scenarios, whereas Cr(III) is an essential nutrient with a broad safety range and low toxicity. The human body has effective detoxification mechanisms that can reduce ingested or inhaled Cr(VI) to Cr(III). In conclusion, there is no clear evidence to relate exposure to environmental levels of chromium with adverse health effects in either the general UK population or subgroups exposed to chromium around industrialized or contaminated sites. It can be expected that an improved understanding of the relevance of possible long-term accumulation of Cr(III) in the body may facilitate a more complete assessment, in the future, of the health risks in the general population associated with environmental exposure to chromium.

Asunto(s)

Compuestos de Cromo/efectos adversos , Exposición a Riesgos Ambientales/efectos adversos , Contaminantes Ambientales/efectos adversos , Animales , Compuestos de Cromo/análisis , Exposición a Riesgos Ambientales/estadística & datos numéricos , Abastecimiento de Alimentos/estadística & datos numéricos , Humanos , Pruebas de Toxicidad , Reino Unido , Abastecimiento de Agua/análisis , Abastecimiento de Agua/estadística & datos numéricos

RESUMEN

A new mouse Polycomb (Pc) gene, MPc3, has been identified. The MPc3 protein contains the highly conserved chromodomain and carboxy-terminal COOH box of other known Pc proteins from diverse species. Like other Pc proteins, MPc3 physically interacts with the RING finger proteins RING1A and dinG/RING1B. MPc3 maps to the distal arm of mouse chromosome 11 (11E2), a region that contains other known Pc genes in addition to several disease loci that may be linked to abnormal Pc gene function.

Asunto(s)

Proteínas Represoras/genética , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Mapeo Cromosómico , ADN/química , ADN/genética , ADN Complementario/química , ADN Complementario/genética , Proteínas de Unión al ADN/metabolismo , Embrión de Mamíferos/metabolismo , Exones , Regulación del Desarrollo de la Expresión Génica , Hibridación Fluorescente in Situ , Intrones , Ratones , Ratones Endogámicos , Proteínas de Transporte de Membrana Mitocondrial , Datos de Secuencia Molecular , Complejo Represivo Polycomb 1 , Proteínas del Grupo Polycomb , Unión Proteica , ARN Mensajero/genética , ARN Mensajero/metabolismo , Proteínas Represoras/metabolismo , Saccharomyces cerevisiae/genética , Análisis de Secuencia de ADN , Homología de Secuencia de Aminoácido , Técnicas del Sistema de Dos Híbridos

RESUMEN

SAIDS-associated lymphoma (SAL) represents a monoclonal expansion of B-cell origin in which simian immunodeficiency virus (SIV) infection is not detected. However, tumor cells are frequently infected with rhesus lymphocryptovirus (RhLCV), a rhesus homologue of Epstein-Barr virus (EBV). In previous studies, the incidence of RhLCV infection in SAL was determined to be 89% as measured by polymerase chain reaction (PCR) and/or in situ hybridization. The main objective of the present study was to ascertain whether the level of RhLCV infection in the SIV-infected macaque is influenced as a function of SAIDS progression, and/or whether increased levels of RhLCV infection may correlate with the development of SAL. To this end, RhLCV infection was evaluated in three independent groups: (1) in lymphomas from SIV-infected rhesus macaques, (2) in peripheral blood mononuclear cells (PBMC) from a cohort of 69 randomly selected healthy animals, and (3) in PBMC collected from 22 SIV-infected animals at various times during progression to SAIDS or SAL. The relative levels of RhLCV infection were evaluated by PCR/Southern blot analysis, visual comparison to a standard dilution series, and assignment of relative signal intensity to a uniform classification scheme. The data show that SIV-infected monkeys have a generally higher RhLCV load in PBMC than do healthy animals, but that the virus load varies widely among animals during disease progression. Increased RhLCV load does not occur uniformly during the progression of SAIDS, although evidence indicates an increased RhLCV viral load in the development of SAL.

Asunto(s)

Infecciones por Herpesviridae/complicaciones , Lymphocryptovirus , Linfoma de Células B/virología , Síndrome de Inmunodeficiencia Adquirida del Simio/complicaciones , Infecciones Tumorales por Virus/complicaciones , Animales , Southern Blotting , Progresión de la Enfermedad , Infecciones por Herpesviridae/virología , Macaca mulatta , Reacción en Cadena de la Polimerasa , Distribución Aleatoria , Síndrome de Inmunodeficiencia Adquirida del Simio/virología , Infecciones Tumorales por Virus/virología , Carga Viral

RESUMEN

Feline leukemia virus (FeLV), like other naturally occurring retroviruses, is characterized by a high degree of genetic diversity. FeLV-945 is a natural isolate derived from non-B-cell non-T-cell lymphomas classified anatomically as multicentric. FeLV-945 exhibits a unique structural motif in the LTR composed of a 21-bp tandem triplication downstream of a single copy of enhancer. The unique FeLV-945 LTR is precisely conserved among eight independent multicentric lymphomas collected in a geographic cluster. Previous studies using reporter gene constructs predict that the FeLV-945 LTR would confer a replicative advantage on the virus that contains it, particularly in primitive hematopoietic cells. Such an advantage may account for the precise conservation of the unique LTR sequence. To test that prediction, a set of recombinant, infectious FeLVs was developed that are isogenic other than the presence of the FeLV-945 LTR or mutations of it. Replication assays show that the FeLV-945 LTR confers a distinct growth advantage in K-562, FEA, and 3201 cells and implicate the 21-bp triplication in that function. Replacement of two copies of the triplicated element with random sequence greatly diminished the replicative capacity, thus implicating the triplicated sequence itself in LTR function. The 21-bp triplication was shown to contain specific nuclear protein binding sites, which may account for the selective pressure to conserve the sequence.

Asunto(s)

Virus de la Leucemia Felina/crecimiento & desarrollo , Virus de la Leucemia Felina/genética , Secuencias Repetidas en Tándem/genética , Secuencias Repetidas Terminales/genética , Replicación Viral/genética , Animales , Secuencia de Bases , Gatos , Línea Celular , Secuencia Conservada/genética , ADN/genética , ADN/metabolismo , Proteínas de Unión al ADN/metabolismo , Elementos de Facilitación Genéticos/genética , Humanos , Células K562 , Cinética , Virus de la Leucemia Felina/enzimología , Mutación , Provirus/genética , ARN Mensajero/análisis , ARN Mensajero/genética , ARN Viral/análisis , ARN Viral/genética , ADN Polimerasa Dirigida por ARN/metabolismo , Linfocitos T/virología

RESUMEN

Non-Hodgkin's lymphomas occur with increased frequency (3-6%) in HIV-infected individuals. These AIDS-associated lymphomas (AALs) exhibit characteristics that distinguish them from lymphomas in the general population. A proposed model for the pathogenesis of AAL includes the following: (1) Tumorigenesis is multistep; (2) tumors occur in long-term survivors; (3) tumors are of clonal B cell origin; (4) HIV acts early and is an indirect effector; (5) tumor cells are infected with EBV; and (6) specific genetic lesions occur in tumor cells. Many aspects of this process remain to be tested in an animal model system. Since 1984, necropsy examinations have been performed on more than 1000 SIV-infected rhesus and cynomolgus monkeys at the Tulane Regional Primate Research Center. Lymphoid malignancies were detected in a proportion of SIV-infected animals. These SAIDS-associated lymphomas (SALs) have been studied to determine the extent to which their pathological features recapitulate a working model for the pathogenesis of AAL. The results show that lymphomas occur in SIV-infected rhesus macaques at 4% incidence, similar to that of AAL, and that the incidence of SAL in cynomolgus macaques is eightfold higher. Analysis of SAL from both species of macaques demonstrated significant similarity to the hallmark pathobiological features of AAL. These findings indicate that the HIV-infected human and the SIV-infected macaque share a common pathobiology and mechanism of lymphomagenesis.

Asunto(s)

Linfoma Relacionado con SIDA/veterinaria , Linfoma no Hodgkin/patología , Enfermedades de los Monos/patología , Síndrome de Inmunodeficiencia Adquirida del Simio/patología , Virus de la Inmunodeficiencia de los Simios , Animales , Secuencia de Bases , Southern Blotting , ADN Viral/análisis , ADN Viral/aislamiento & purificación , Humanos , Inmunohistoquímica , Hibridación in Situ , Linfoma Relacionado con SIDA/patología , Linfoma Relacionado con SIDA/virología , Linfoma no Hodgkin/virología , Macaca fascicularis , Macaca mulatta , Datos de Secuencia Molecular , Reacción en Cadena de la Polimerasa , Síndrome de Inmunodeficiencia Adquirida del Simio/virología , Virus de la Inmunodeficiencia de los Simios/genética

RESUMEN

The expression of cytokines may influence the development of lymphoma in retrovirally infected animals in at least two ways: (1) cytokines in the tumor environment may stimulate the proliferation of tumor cells and/or (2) cytokines in the tumor environment may diminish the cell-mediated antitumor immune response. To evaluate these possibilities, a semiquantitative RT-PCR approach was utilized to permit a broad screening of cytokine mRNAs in a large number of tissue samples. Examination of MuLV-induced end-stage lymphomas revealed the absence of mRNA for cytokines known to stimulate the proliferation of T cells (i.e., IL-2, IL-9), the absence of mRNA for cytokines known to enhance cell-mediated antitumor immune responses (i.e., IL-2, IFNgamma), and the presence of mRNA for cytokines known to diminish such responses (i.e., IL-4, IL-10). Similar patterns of cytokine mRNA expression were detected in tumor-derived cell lines. Spleen and thymus from animals collected longitudinally during infection and from age-matched uninfected mice also demonstrated a similar pattern, except that IFNgamma mRNA was readily detectable. These findings do not support the hypothesis that the developing tumor depends on cytokines to provide proliferative signals. The findings suggest that cytokines in the immediate environment of the lymphoma support tumor development by acting to diminish an effective antitumor immune response.

Asunto(s)

Regulación Neoplásica de la Expresión Génica/inmunología , Virus de la Leucemia Murina/inmunología , Leucemia Experimental/inmunología , Infecciones por Retroviridae/inmunología , Infecciones Tumorales por Virus/inmunología , Animales , Regulación Viral de la Expresión Génica/inmunología , Interferón gamma/biosíntesis , Interferón gamma/genética , Interferón gamma/inmunología , Interleucina-10/biosíntesis , Interleucina-10/genética , Interleucina-10/inmunología , Interleucina-2/biosíntesis , Interleucina-2/genética , Interleucina-2/inmunología , Interleucina-4/biosíntesis , Interleucina-4/genética , Interleucina-4/inmunología , Interleucina-9/biosíntesis , Interleucina-9/genética , Interleucina-9/inmunología , Virus de la Leucemia Murina/genética , Leucemia Experimental/genética , Ratones , ARN Mensajero/análisis , ARN Mensajero/biosíntesis , Infecciones por Retroviridae/genética , Infecciones Tumorales por Virus/genética

RESUMEN

The retrovirus SL3 induces T-cell lymphomas in mice. The transcriptional enhancer in the long terminal repeat (LTR) of SL3 contains two 72-bp repeats. Each repeat contains a binding site for the transcription factor CBF (also called AML1). The CBF binding sites are called core elements. SAA is a mutant that is identical to SL3 except for the presence of a single-base-pair substitution in each of the two core elements. This mutation significantly attenuates viral lymphomagenicity. Most lymphomas that occur in SAA-infected mice contain proviruses with reversions or second-site suppressor mutations within the core element. We examined the selective pressures that might account for the predominance of the reversions and suppressor mutations in tumor proviruses by analyzing when proviruses with altered core sequences became abundant during the course of lymphomagenesis. Altered core sequences were easily detected in thymus DNAs by 4 to 6 weeks after SAA infection of mice, well before lymphomas were grossly evident. This result is consistent with the hypothesis that viruses with the core sequence alterations emerged because they replicated more effectively in mice than SAA. The number of 72-bp tandem, repeats in the viral LTR was found to vary, presumably as a consequence of reverse transcriptase slippage during polymerization. Proviruses with two repeats predominated in the thymuses of SAA- and SL3-infected mice before lymphomas developed, although LTRs with one or three repeats were also present. This suggested that two was the optimal number of 72-bp repeats for viral replication. However, in lymphomas, proviruses with three or four repeats usually predominated. This suggested that a late step in the process of lymphomagenesis led to the abundance of proviruses with additional repeats. We hypothesize that proviruses with additional 72-bp repeats endowed the cells containing them with a selective growth advantage.

Asunto(s)

Proteínas de Unión al ADN , Virus de la Leucemia Murina/genética , Leucemia Experimental/virología , Linfoma de Células T/virología , Mutación , Proteínas Proto-Oncogénicas , Infecciones por Retroviridae/virología , Factores de Transcripción/metabolismo , Infecciones Tumorales por Virus/virología , Animales , Secuencia de Bases , Sitios de Unión , Subunidad alfa 2 del Factor de Unión al Sitio Principal , ADN Viral , Elementos de Facilitación Genéticos , Ratones , Ratones Endogámicos AKR , Datos de Secuencia Molecular , Provirus/genética , Secuencias Repetitivas de Ácidos Nucleicos , Supresión Genética , Factores de Tiempo