RESUMEN
Endogenous retroviruses (ERVs) are remnants of ancestral viral infections. Feline leukemia virus (FeLV) is an exogenous and endogenous retrovirus in domestic cats. It is classified into several subgroups (A, B, C, D, E, and T) based on viral receptor interference properties or receptor usage. ERV-derived molecules benefit animals, conferring resistance to infectious diseases. However, the soluble protein encoded by the defective envelope (env) gene of endogenous FeLV (enFeLV) functions as a co-factor in FeLV subgroup T infections. Therefore, whether the gene emerged to facilitate viral infection is unclear. Based on the properties of ERV-derived molecules, we hypothesized that the defective env genes possess antiviral activity that would be advantageous to the host because FeLV subgroup B (FeLV-B), a recombinant virus derived from enFeLV env, is restricted to viral transmission among domestic cats. When soluble truncated Env proteins from enFeLV were tested for their inhibitory effects against enFeLV and FeLV-B, they inhibited viral infection. Notably, this antiviral machinery was extended to infection with the Gibbon ape leukemia virus, Koala retrovirus A, and Hervey pteropid gammaretrovirus. Although these viruses used feline phosphate transporter 1 (fePit1) and phosphate transporter 2 as receptors, the inhibitory mechanism involved competitive receptor binding in a fePit1-dependent manner. The shift in receptor usage might have occurred to avoid the inhibitory effect. Overall, these findings highlight the possible emergence of soluble truncated Env proteins from enFeLV as a restriction factor against retroviral infection and will help in developing host immunity and antiviral defense by controlling retroviral spread.IMPORTANCERetroviruses are unique in using reverse transcriptase to convert RNA genomes into DNA, infecting germ cells, and transmitting to offspring. Numerous ancient retroviral sequences are known as endogenous retroviruses (ERVs). The soluble Env protein derived from ERVs functions as a co-factor that assists in FeLV-T infection. However, herein, we show that the soluble Env protein exhibits antiviral activity and provides resistance to mammalian retrovirus infection through competitive receptor binding. In particular, this finding may explain why FeLV-B transmission is not observed among domestic cats. ERV-derived molecules can benefit animals in an evolutionary arms race, highlighting the double-edged-sword nature of ERVs.
Asunto(s)
Productos del Gen env , Virus de la Leucemia Felina , Leucemia Felina , Animales , Gatos , Retrovirus Endógenos/genética , Retrovirus Endógenos/metabolismo , Productos del Gen env/genética , Productos del Gen env/metabolismo , Virus de la Leucemia Felina/clasificación , Virus de la Leucemia Felina/genética , Virus de la Leucemia Felina/metabolismo , Virus de la Leucemia del Gibón/genética , Virus de la Leucemia del Gibón/metabolismo , Leucemia Felina/genética , Leucemia Felina/metabolismo , Leucemia Felina/virología , Proteínas de Transporte de Fosfato/genética , Proteínas de Transporte de Fosfato/metabolismo , Receptores Virales/metabolismo , Infecciones por Retroviridae/metabolismo , Infecciones por Retroviridae/virología , Solubilidad , FemeninoRESUMEN
Feline lymphomas are associated with the transduction and activation of cellular proto-oncogenes, such as c-myc, by feline leukemia virus (FeLV). We describe a polymerase chain reaction assay for detection of myc transduction usable in clinical diagnosis. The assay targets c-myc exons 2 and 3, which together result in a FeLV-specific fusion gene following c-myc transduction. When this assay was conducted on FeLV-infected feline tissues submitted for clinical diagnosis of tumors, myc transduction was detected in 14% of T-cell lymphoma/leukemias. This newly established system could become a useful diagnostic tool in veterinary medicine.
Asunto(s)
ADN Viral/genética , Virus de la Leucemia Felina/genética , Leucemia Felina/diagnóstico , Linfoma de Células T/diagnóstico , Reacción en Cadena de la Polimerasa/métodos , Proteínas Proto-Oncogénicas c-myc/genética , Animales , Linfocitos B/metabolismo , Linfocitos B/patología , Gatos , Femenino , Expresión Génica , Virus de la Leucemia Felina/aislamiento & purificación , Leucemia Felina/genética , Leucemia Felina/metabolismo , Leucemia Felina/patología , Linfoma de Células T/genética , Linfoma de Células T/metabolismo , Linfoma de Células T/patología , Masculino , Proteínas de Fusión Oncogénica/genética , Proteínas de Fusión Oncogénica/metabolismo , Proteínas Proto-Oncogénicas c-myc/metabolismo , Linfocitos T/metabolismo , Linfocitos T/patología , Transducción GenéticaRESUMEN
Gammaretrovirus receptors have been suggested to contain the necessary determinants to mediate virus binding and entry. Here, we show that murine NIH 3T3 and baby hamster kidney (BHK) cells overexpressing receptors for subgroup A, B, and C feline leukemia viruses (FeLVs) are weakly susceptible (10(1) to 10(2) CFU/ml) to FeLV pseudotype viruses containing murine leukemia virus (MLV) core (Gag-Pol) proteins, whereas FeLV receptor-expressing murine Mus dunni tail fibroblast (MDTF) cells are highly susceptible (10(4) to 10(6) CFU/ml). However, NIH 3T3 cells expressing the FeLV subgroup B receptor PiT1 are highly susceptible to gibbon ape leukemia virus pseudotype virus, which differs from the FeLV pseudotype viruses only in the envelope protein. FeLV resistance is not caused by a defect in envelope binding, low receptor expression levels, or N-linked glycosylation. Resistance is not alleviated by substitution of the MLV core in the FeLV pseudotype virus with FeLV core proteins. Interestingly, FeLV resistance is alleviated by fusion of receptor-expressing NIH 3T3 and BHK cells with MDTF or human TE671 cells, suggesting the absence of an additional cellular component in NIH 3T3 and BHK cells that is required for FeLV infection. The putative FeLV-specific cellular component is not a secreted factor, as MDTF conditioned medium does not alleviate the block to FeLV infection. Together, our findings suggest that FeLV infection requires an additional envelope-dependent cellular component that is absent in NIH 3T3 and BHK cells but that is present in MDTF and TE671 cells.
Asunto(s)
Virus de la Leucemia Felina/patogenicidad , Leucemia Felina/metabolismo , Leucemia Felina/virología , Receptores Virales/metabolismo , Proteínas del Núcleo Viral/metabolismo , Proteínas del Envoltorio Viral/metabolismo , Animales , Gatos , Células Cultivadas , Cricetinae , Citometría de Flujo , Glicosilación/efectos de los fármacos , Humanos , Riñón/citología , Riñón/metabolismo , Riñón/virología , Leucemia Felina/patología , Proteínas de la Membrana/metabolismo , Proteínas de Transporte de Membrana/metabolismo , Ratones , Células 3T3 NIH , Unión Proteica , Factor de Transcripción Pit-1/metabolismo , Virión/fisiología , Acoplamiento ViralRESUMEN
Laboratory diagnosis of feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) usually involves both viruses, as the clinical signs are similar and coinfection may occur. Serological methods may not represent an accurate diagnosis: maternal antibodies or cross-reactions may give false positive results to FIV, and false negative results may occur in latent FeLV status, or in certain FIV infection stages. A nested polymerase chain reaction (PCR) technique was designed to detect FeLV, FIV and feline endogenous retrovirus simultaneously. The detection of endogenous sequences was considered indicative of successful DNA extraction. The technique was used to diagnose FIV and FeLV in the blood cells of 179 cats. The kappa value with the serological data was 0.69 for FeLV and 0.87 for FIV. The joint detection of FeLV and FIV by this novel nested PCR is sensitive, specific, fast and convenient, and its applicability for clinical diagnosis is promising, as the direct evidence of the presence of the virus is more realistic than the indirect data provided by the serological detection.
Asunto(s)
Síndrome de Inmunodeficiencia Adquirida del Felino/diagnóstico , Virus de la Inmunodeficiencia Felina , Virus de la Leucemia Felina , Leucemia Felina/diagnóstico , Reacción en Cadena de la Polimerasa/veterinaria , Animales , Gatos , Ensayo de Inmunoadsorción Enzimática/veterinaria , Síndrome de Inmunodeficiencia Adquirida del Felino/inmunología , Síndrome de Inmunodeficiencia Adquirida del Felino/metabolismo , Leucemia Felina/inmunología , Leucemia Felina/metabolismo , Sensibilidad y Especificidad , Especificidad de la EspecieRESUMEN
alpha1-Acid glycoprotein (AGP) is considered one of the major acute phase proteins in cats. In humans, AGP is a heavily glycosylated protein that undergoes several modifications of its glycan moiety during acute and chronic inflammatory pathologies. In this paper we present the feline AGPs (fAGP) glycan moiety modifications in the course of two prevalent feline diseases, the FIV (feline immunodeficiency virus) dependent feline acquired viral immunodeficiency and the feline leukemia virus (FeLV) associated lymphoma. The glycan moiety of fAGP was investigated by means of the binding of its oligosaccharides residues with specific lectins. Four lectins were used: Sambucus nigra agglutinin I and Maackia amurensis agglutinin lectins were used to detect sialic acid residues, Aleuria aurantia lectin was used to detect L-fucose residues and Concanavalin A was used to evaluate the degree of branching. It was found that fAGP undergoes several post-translational modifications of its glycan pattern: in particular the degree of sialylation is increased in FeLV-positive cats diagnosed with lymphoma, while FeLV-positive that did not presented any specific clinical signs cats do not present any increase of expression of sialic acid on the surface. Furthermore, FIV induced a modification of the glycan moiety of fAGP, which however varied widely among individuals. In order to determine the number and the position of oligosaccharide chains, the cDNA sequence of fAGP was also determined. The translation of the mature fAGP coding sequence gave rise to a sequence of 183 residues, with five potential N-glycosylation sites, but also with seven potential phosphorylation sites.
Asunto(s)
Síndrome de Inmunodeficiencia Adquirida del Felino/metabolismo , Virus de la Inmunodeficiencia Felina , Virus de la Leucemia Felina , Leucemia Felina/metabolismo , Orosomucoide/química , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Gatos , Clonación Molecular , ADN Complementario/genética , Síndrome de Inmunodeficiencia Adquirida del Felino/genética , Glicosilación , Lectinas/metabolismo , Leucemia Felina/genética , Datos de Secuencia Molecular , Orosomucoide/genética , Orosomucoide/metabolismo , Polisacáridos/química , Procesamiento Proteico-Postraduccional , Homología de Secuencia de AminoácidoRESUMEN
To identify potential roles of cytokines in retroviral pathogenesis, we used reverse transcription-quantitative competitive polymerase chain reaction (RT-qcPCR) assays to characterize mRNA levels of 19 different lymphokines, chemokines, monokines and hematopoietic growth factors in three feline cell lines productively infected with subgroup A feline leukemia virus (FeLV-A) or various feline immunodeficiency virus (FIV) strains. Infection of a CD8+, CD5- large granular lymphocyte (LGL) cell line with FeLV-A activated expression of interleukin-7 (IL-7), induced modest (4-fold) increases in granulocyte/macrophage colony-stimulating factor (GM-CSF) and leukemia inhibitory factor (LIF) transcripts, and decreased transforming growth factor-beta (TGF-beta) mRNA (4-fold). The LGL cells were not susceptible to infection by FIV. Infection of MYA-1 cells, a CD4+ T-lymphoblastoid cell line, with FeLV-A activated expression of macrophage inflammatory protein-1alpha (MIP-1alpha), increased transcript levels of GM-CSF (8-fold), macrophage CSF (M-CSF) (16-fold) and stem cell factor (SCF) (250-fold), and decreased (4-fold) expression of IL-10 and tumor necrosis factor-alpha (TNF-alpha). Productive infection with four different FIV molecular clones caused progressive MYA-1 cell death; however, the mRNA expression profiles were unchanged except for 2- to 4-fold increases in M-CSF and 16- to 500-fold increases in SCF. Thus, FIV-induced MYA-1 cytopathicity was not associated with dysregulation of pro-apoptotic or survival factor transcript levels. Lastly, productive infection of PNI cells, a marrow-derived fibroendothelial cell line, with FeLV-A or any of three FIV strains induced 4-fold higher levels of IL-12p40 transcripts and variably higher levels (4- to 64-fold) of GM-CSF. Two viral strains, the FIV-14 molecular clone and the clinical isolate FIV-5122, caused syncytia formation and unique activation of IL-1beta and stromal cell-derived factor-1 (SDF-1) expression, suggesting a potential role for those factors in viral spread and/or cytopathicity. In addition, infection with FIV-5122, but not the other FIV strains or FeLV-A, induced significant increases in mRNA levels of the hematopoietic inhibitors TNF-alpha and MIP-1alpha, along with increased concentrations of soluble proteins in culture supernatants. Consistent with this, supernatant from FIV-5122 infected PNI cells suppressed hematopoietic progenitor growth in colony assays, compared to supportive activities in supernatants from other infected or uninfected PNI cell cultures. Together, these data demonstrate that feline retroviruses alter cytokine mRNA levels in general and strain-specific patterns. These changes may result in specific alterations in cell function and contribute to retroviral pathogenesis. Our observations provide a basis for directed studies of candidate factors within the hematopoietic, thymic and lymphoid microenvironments.
Asunto(s)
Citocinas/biosíntesis , Virus de la Leucemia Felina/patogenicidad , Leucemia Felina/metabolismo , Animales , Gatos , Línea Celular , Clonación Molecular , Citocinas/genética , Efecto Citopatogénico Viral , Virus de la Leucemia Felina/metabolismo , Reacción en Cadena de la Polimerasa/veterinariaRESUMEN
After several years of latency, feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) cause fatal disease in the cat. The aim of this study was to determine laboratory parameters characteristic of disease progression which would allow a better description of the asymptomatic phase and a better understanding of the pathogenesis of the two infections. Therefore, experimentally infected cats (FIV and/or FeLV positive) and control animals were observed over a period of 6.5 years under identical conditions. Blood samples were analyzed for the following: complete hematology, clinical chemistry, serum protein electrophoresis, and determination of CD4+ and CD8+ lymphocyte subsets. The following hematological and clinical chemistry parameters were markedly changed in the FIV-infected animals from month 9 onwards: glucose, serum protein, gamma globulins, sodium, urea, phosphorus, lipase, cholesterol, and triglyceride. In FeLV infection, the markedly changed parameters were mean corpuscular volume, mean corpuscular hemoglobin, aspartate aminotransferase, and urea. In contrast to reports of field studies, neither FIV-positive nor FeLV-positive animals developed persistent leukopenia, lymphopenia, or neutropenia. A significant decrease was found in the CD4+/CD8+ ratio in FIV-positive and FIV-FeLV-positive animals mainly due to loss of CD4+ lymphocytes. In FeLV-positive cats, both CD4+ and, to a lesser degree, CD8+ lymphocytes were decreased in long-term infection. The changes in FIV infection may reflect subclinical kidney dysfunction, changes in energy and lipid metabolism, and transient activation of the humoral immune response as described for human immunodeficiency virus (HIV) infections. The changes in FeLV infection may also reflect subclinical kidney dysfunction and, in addition, changes in erythrocyte and immune function of the animals. No severe clinical signs were observed in the FIV-positive cats, while FeLV had a severe influence on the life expectancy of persistently positive cats. In conclusion, several parameters of clinical chemistry and hematology were changed in FIV and FeLV infection. Monitoring of these parameters may prove useful for the evaluation of candidate FIV vaccines and antiretroviral drugs in cats. The many parallels between laboratory parameters in FIV and HIV infection further support the importance of FIV as a model for HIV.
Asunto(s)
Síndrome de Inmunodeficiencia Adquirida del Felino/sangre , Síndrome de Inmunodeficiencia Adquirida del Felino/etiología , Virus de la Inmunodeficiencia Felina , Virus de la Leucemia Felina , Leucemia Felina/sangre , Leucemia Felina/etiología , Subgrupos Linfocitarios/inmunología , Animales , Recuento de Células Sanguíneas , Análisis Químico de la Sangre , Relación CD4-CD8 , Gatos , Progresión de la Enfermedad , Síndrome de Inmunodeficiencia Adquirida del Felino/inmunología , Síndrome de Inmunodeficiencia Adquirida del Felino/metabolismo , Leucemia Felina/inmunología , Leucemia Felina/metabolismoRESUMEN
Naturally occurring retroviral infections cause progressive weight loss, immune suppression, invasion by opportunistic organisms, and eventual death. Feline leukemia virus (FeLV) inhibited growth and decreased energy intake in seven experimentally infected weanling cats compared with age- and sex-matched controls. Remarkably, changes in energy intake, energy expenditure, and weight gain occurred in the acute phase of infection prior to the systemic/productive bone marrow phase of FeLV infection. In other words, growth inhibition developed before FeLV infection was clinically detectable with use of standard enzyme-linked immunosorbent assay or fixed-cell immunofluorescence assays of circulating neutrophils and platelets. Acutely infected, previremic cats consumed 25% less energy [Day 4 postinoculation to Day 16 postinoculation (p < 0.05)] and expended 20% less energy [Day 8 postinoculation to Day 18 postinoculation (p < 0.05)] compared with control cats. Growth stunting of inoculated cats began by Day 11 postinoculation (p < 0.05) and was not corrected during the remaining 4 months of the study. Thus, experimental FeLV infection causes perturbations of metabolism and energy balance resulting in permanent growth impairment. Secondly, detrimental metabolic effects begin in the acute phase of retroviral infection, prior to the clinically detectable phase of FeLV infection.