Vírus da leucemia felina: análise da classificação da infecção, das técnicas de diagnóstico e da eficácia da vacinação com o emprego de técnicas sensíveis de detecção viral

O Vírus da leucemia felina (FeLV) pertence à família Retroviridae, gênero Gammaretrovirus. Diferentemente de outras retroviroses, uma parcela dos gatos jovens e adultos exposta ao FeLV não apresenta antigenemia/viremia, de acordo com as técnicas convencionais de detecção viral, como isolamento em cultivo celular, imunofluorescência direta e ELISA. O emprego de técnicas de maior sensibilidade para detecção e quantificação viral, como o PCR quantitativo, permitiu a identificação de animais positivos para a presença de DNA proviral e RNA na ausência de antigenemia/viremia e, com isso, um refinamento da análise das diferentes evoluções da infecção. Assim, reclassificou-se a patogenia do FeLV em 4 categorias: infecção abortiva, regressiva, latente e progressiva. Foi possível também detectar DNA proviral e RNA em animais considerados imunes ao FeLV após vacinação. Diante disso, os objetivos desta revisão de literatura foram demonstrar as implicações da utilização de técnicas sensíveis de detecção viral na interpretação e classificação da infecção do FeLV e rever as técnicas de detecção do vírus para fins de diagnóstico. Além disso, apresentar os resultados referentes à eficácia da vacinação contra o FeLV com a utilização dessas técnicas.

Cloning of glucocorticoid-regulated genes in C6/ST1 rat glioma phenotypic reversion

The C6 rat glioma cell line is responsive to glucocorticoid hormones. C6 variants that are hyper-responsive (ST1) and resistant (P7) to hormone treatment have been derived previously. Glucocorticoid treatment of ST1 cells leads to complete reversion of the transformed phenotype and loss of tumorigenic potential. Production of C type retrovirus particles is also induced by glucocorticoids in ST1 cells. Cloning of the genes regulated by glucocorticoids in this cell system was used here as a strategy to uncover the gene products involved in the transformed-to-normal phenotypic change. Construction of a cDNA library from glucocorticoid-treated ST1 cells and screening by differential hybridization resulted in the isolation of three cellular sequences that code for rat metallothioneins (C27 and C41) and α1-acid glycoprotein (C36). Northern blot analysis revealed that expression of these genes was dramatically induced by hydrocortisone in ST1 but not in P7 cells. Viral genomic RNA was used to isolate and characterize retrovirus-related sequences that could also be responsible for the phenotypic reversion phenomenon.

Métodos diagnósticos para detecção da Leucemia viral felina

The feline leukemia virus (FeLV) was described in 1964 by William Jarrett and collaborators wen find viral particles attached to the membrane of lymphoblasts in cat with lymphoma. The virus belongs to the family Retroviridae, subfamily oncornavirus. With worldwide distribution, the occurrence of FeLV has 1.6% in healthy cats and 10.8% in sick cats in Brazil. The mortality of persistently viremic animals in catteries is about 50% in two years and 80% in three years. In catteries that have endemic feline Coronavirus (FCoV), FeLV and / or Feline Immunodeficiency Virus (FIV), the FeLV infection has greater contribution to mortality. The test for infection and FeLV positive cats segregation is the main way to prevent the spread of infection. The diagnostic methods are based on clinical signs and changes compatible with FeLV infection observed by physical examination, complete blood count, X-ray, bone marrow aspirate and biochemical. The viral p27 protein is produced in infected cells in high amounts and is found in abundance in the cytoplasm and in body fluids enabling diagnosed methods such as enzyme-linked immunosorbent assay - ELISA and direct immunofluorescence, detection of viral genome (Chain Reaction Polymerase - PCR) and detection of the virus by virus isolation. Although diagnostic tests are highly sensitive, it should be made more than a confirmatory test, especially serological due to variable characteristic of the progress of infection