Serological relationships among maize rough dwarf-like viruses

A developmentally linked, dramatic, and transient loss of virus from roots of Arabidopsis thaliana plants infected by either of two RNA viruses

Possible effects of host developmental stage on the amount of virus present in systemically infected plant tissues hitherto have received little attention. In this study, the pattern of virus accumulation over the plant lifespan has been examined in systemically invaded tissues of Arabidopsis thaliana infected by either of two distinct (+)RNA viruses: Turnip mosaic virus, a member of Potyvirus, and Oilseed rape mosaic virus, a member of Tobamovirus. Quantitative analyses of virus coat protein and virus genomic RNA in roots versus aerial plant parts revealed generally sinusoidal temporal patterns of virus accumulation. In noninoculated leaves, a time period was found during which no virus accumulation was detected. This period was coincident with the approximately 7 days of inflorescence bud formation and differentiation. In roots, virion content reached high levels a few days after inoculation, dropping dramatically during the period of bud formation and quickly recovering after it. These results, together with electron microscopy observations, are consistent with loss of virions due to disassembly. Fluorescence observations of green fluorescent protein-tagged virus-infected root tissue also were consistent with a net loss of virus-specified proteins. Inoculations performed after the emergence of the inflorescence and on A. thaliana flowering-time mutants support the temporal link between observed changes in virus content and inflorescence bud formation. Different host-involving biochemical processes can be invoked to provide mechanistic clues, but no one of them alone seems sufficient to explain the complex patterns of tight temporal regulation of virus accumulation observed in these experiments.

Quantification of recombinant core-like particles of bluetongue virus using immunosorbent electron microscopy

Immunosorbent electron microscopy was used to quantify recombinant baculovirus-generated bluetongue virus (BTV) core-like particles (CLP) in either purified preparations or lysates of recombinant baculovirus-infected cells. The capture antibody was an anti-BTV VP7 monoclonal antibody. The CLP concentration in purified preparations was determined to be 6.6 x 10(15) particles/l. CLP concentration in lysates of recombinant baculovirus-infected cells was determined at various times post-infection and shown to reach a value of 3 x 10(15) particles/l of culture medium at 96 h post-infection. The results indicated that immunosorbent electron microscopy, aided by an improved particle counting method, is a simple, rapid and accurate technique for the quantification of virus and virus-like particles produced in large scale in vitro systems.

Immunosorbent electron microscopy for detection of viruses

This chapter discusses the newer modifications of immunosorbent electron microscopy (ISEM) methods in both plant and animal virology. ISEM methods presented in the chapter include all the techniques where the “solid phase principle” is essential in a way similar to other solid phase immunoassays. These methods include (1) the antibody-coated grid technique (AB-CGT); (2) the protein A-coated grid technique (PA-CGT); (3) the protein A-coated bacteria technique (PA-CBT); and (4) the antigen-coated grid technique (AG-CGT). In all ISEM methods, one of the components of the system is adsorbed to a solid phase. In AG-CGT, PA-CGT, and AB-CGT, one of the reagents is adsorbed to an electron microscopic grid, while in PA-CBT protein A is naturally present on the surface of a bacterium that serves as a solid support. In ISEM methods, the viruses can be statistically evaluated and numerically expressed as number of virions per unit of area, and can, therefore, be statistically evaluated. Thus, these methods optimize the results of a test by quantifying the effects of the quality of the supporting grid, the time of adsorption, the pH, the presence of salts, and the type of staining. The ISEM also permits a detailed study of antigenic variations in the same genus of virus, and thus would visually pinpoint the type or strain differences.

Enhancement of the immunogenicity of the maize rough dwarf virus outer shell with the cross-linking reagent dithiobis(succinimidyl)propionate

Injection into rabbits of native or glutaraldehyde (GA)-treated intact particles of the fijivirus maize rough dwarf virus (MRDV) failed to yield antibodies to the outer shell of the virus. After fixation of the particles with the cross-linking reagent dithiobis(succinimidyl)propionate (DSP), antisera were obtained reacting with the outer shell of MRDV (both DSP-fixed and unfixed) to a titre of 1/1024 in immunoelectron microscopic decoration tests, but giving no reaction with another fijivirus, oat sterile dwarf virus, whose subviral particles are known to be unrelated to those of MRDV. Further fixation of the DSP-fixed particles with GA did not appear to enhance immunogenicity. Stabilization with DSP could have further application with viruses the instability of which renders them poor immunogens.