Abortive cell culture infections of nuclear polyhedrosis viruses as model systems for host specificity

Descreve-se a proliferação do vírus e o efeito citopático numa infecção abortiva que envolve o vírus de poliedrose nuclear de Autographa californica (AcMNPV) e uma linhagem de Bombyx mori. Os resultados indicam que o AcMNPV acarreta efeitos citopáticos (CPE) complexos e raros nas cálulas do B. mori. Tal fato envolve a formação de sacos e protrusões, além da hipertrofia e arredondamento do núcleo, normalmente observados em infecções produtivas. A infecção de células de B. mori com AcMNPV inativado por raios ultravioleta induz a formação somente de sacos, o que indica que a expressão gênica virial não é necessária para este efeito. Nas células de B. mori nenhum vírus infeccioso é produzido. A microscopia eletrônica mostra que somente o estroma virogênico é formado nas células de B. mori e não os vírions ou PIBs (corpos de inclusão poliédricos). Detectam-se nucleocapsídeos em 20% de células infectadas, porém estes são defectivos. Os resultados sugerem que um componente virial de vírus de poliedrose nuclear (NPV) causa efeito citopático. Este princípio tem importantes implicações na identificação de genes virais visando à produção de plantas transgênicas resistentes a insetos-praga.We describe virus growth and cytopathic effect (CPE) in an abortive infection involving Autographa californica nuclear polyhedrosis virus (AcMNPV) and a Bombyx mori line. Our results show that AcMNPV causes complex and very unusual CPE in B. mori cells. This involves the formation of sacs and protrusions in addition to the nuclear hypertrophy and rounding normally observed in productive infections. Infection of B. mori cells with UV-inactivated AcMNPV induces only sacs, indicating that viral gene expression is not required for this effect. No infectious virus is produced in B. mori cells. Electron microscopy show that virogenic stroma, but no virions or polyhedral inclusion bodies, are formed in B. mori cells. Nucleocapsids are detected in 20 percent of the infected cells, but are defective. Our results suggest that a virion component of an NPV causes cytopathic effect. This principle has important implications in the identification of viral genes for engineering transgenic crop plants resistant to pest insects

Development and Evaluation of a Novel Taqman Real-Time PCR Assay for Rapid Detection of Mycoplasma bovis: Comparison of Assay Performance with a Conventional PCR Assay and Another Taqman Real-Time PCR Assay

The objective of this study was to develop and validate a Taqman real-time PCR assay for the detection of Mycoplasma bovis (M. bovis). Unique primers targeting the highly conserved house-keeping gene (uvrC) were designed and the probe sequence was derived from a previously published microarray study. There was 100% agreement in the outcome between our assay and the other two published assays for M. bovis detection. The analytical limit of detection of our assay is 83 copies of the uvrC gene. This assay was validated on a total of 214 bovine clinical specimens that were submitted to the Texas A&M Veterinary Medical Diagnostic Laboratory (TVMDL), Texas, USA. The specificity of the assay was assessed to be 100% since no cross-reactivity occurred with 22 other bacterial and other Mycoplasma species. We conclude that the uvrC gene serves as a good and reliable diagnostic marker for the accurate and rapid detection of M. bovis from a wider variety of specimen matrices