Optimal cell density and multiplicity of infection for the propagation of human rotavirus in monkey kidney cells

The human rotavirus titer was optimal at an infection cell density of about 4–8 × 10⁴ cells cm^–2 in monkey kidney cell cultures. The highest viral titers (3.8 × 10⁷ TCID₅₀ ml^–1 and 3.7 × 10⁷ TCID₅₀ ml^–1) were obtained at an multiplicity of infection of 0.05 in well plate and T-flask, respectively.     

Predictive Bayesian Dose-Response Assessment for Appraising Absolute Health Risk from Available Information

Currently, no general measure of population health response to untestable doses of chemicals and microbes has been established that accounts for uncertainty quantitatively and indicates relative toxicity or virulence directly. Untestable doses include those corresponding to the 2.74 × 10^?7 illnesses per exposure expressed in goals of the U.S. Environmental Protection Agency's Surface Water Treatment Rule, and doses of human bioterror agents. For example, it is shown that relative Benchmark Dose (BMD) values depend upon the level of confidence assumed. Because of the lack of scientific basis for this level, BMDs are not comparable among health stressors for untestable doses and stressors. In this paper a new predictive Bayesian method is proposed for absolute and relative dose-response assessment based on available information. Information may include toxicological judgment, epidemiological statistics, genetic information, related data, and numeric dose-response data. Results for rotavirus indicate a “safe dose” of 6.3 × 10^?7 focus-forming units/exposure, approximately one-half log above the dose corresponding to the maximum risk for any pathogen assuming a 100% infection rate. The result further indicates the limited value of data in refining the assessment, due to the inability of data to reduce variability. The method is suggested for assessing risks of new and existing chemicals and pathogens, as a basis for prioritizing expenditures for protection against environmental and terrorist threats.     

Expression and immunoreactivity of a human group a rotavirus Vp4

Rotavirus capsid protein Vp4 plays an important role in the virus adhering and entering the cells. In this study, a Vp4 gene cloned from a rotavirus strain TB-Chen was highly expressed in E. coli BL21 (DE3). The results of the Western blot showed that the protein possesses specific immuno-reactivities and can be specifically recognized by guinea pig antibodies against rotavirus strain SA11 or Wa. Some Vp4 dimers were formed during renaturation. These data obtained from this study provide a strong basis for further study on the structure and function of the Vp4.      

Morphological Study of the Role of Calcium in the Assembly of the Rotavirus Outer Capsid Protein VP7

Maturation of rotavirus occurs in the endoplasmic reticulum (ER), a site of intracellular calcium storage. It was demonstrated previously that calcium plays an important role in the maturation of bovine rotavirus. We used protein A colloidal gold conjugated to an antibody to localize VP7, the outer capsid protein of the simian rotavius SA11, in permeabilized infected cells in the presence and absence of calcium in the culture medium. In medium containing calcium, VP7 was associated with nonenveloped double-shelled particles and membranous structures of the ER. In calcium-free medium, gold particles were not associated with the ER or with virus particles. Gold particles were distributed through the cytoplasm and were mainly associated with granular structures, but did not assemble onto virus particles. Our data suggest that in calcium-free medium, VP7 is synthesized, but does not remain incorporated, in the ER.     

Two G3 Feline Rotavirus Strains Lacking Cross-Neutralization Reactions Represent Distinct Subtypes of Serotype G3

Two feline rotavirus strains, FRV-1 and FRV64, that have been shown to lack cross-neutralization reactions despite the sharing of serotype G3 were examined by plaque-reduction neutralization assays in relation to other G3 strains originating from cats, dogs, humans and monkeys. While FRV-1 and human G3 strains constituted one subtype (G3A), FRV64, canine strains and simian strains constituted another subtype (G3B).