The effect of the virus-serum incubation period upon vaccinia virus serum neutralization titers

Rabbit and human vaccinia virus immune sera were titrated by the plaque reduction serum neutralization (SN) method. Titers determined following a 2-h, 37 degree C virus-serum incubation period were not significantly different from those determined following an 18-h incubation period (2-h, 37 degree C incubation followed by a 16-h, 4 degree C period). However, control virus plaque counts decreased significantly after the longer incubation period. Numerous factors affecting SN titer estimation are reviewed. Standardization of SN test conditions may be useful in comparative potency evaluation of vaccinia-vectored recombinant DNA viral vaccines.     

Reduction of dimensionality in Bayesian nonlinear regression with a pharmacokinetic application

Application of Bayes's theorem to the analysis of nonlinear regression models is limited by numerical problems associated with calculation of integrals of functions of several variables. For k-parameter models that are linear in l of the parameters, a dimension-reduction procedure is described for factoring the posterior distribution into the product of a multivariate normal density and a function of k-l nonlinear parameters. Integrals can then be calculated with (k-l)-dimensional numerical integration. A four-parameter, two-compartment pharmacokinetic model of lidocaine disposition is analyzed using a change of variables in order to obtain a model that is linear in two parameters. It is shown that a Bayesian analysis, with reduction of dimensionality, applied to this model produces appropriate results with reasonable CPU-time requirements.     

Comparison of the Levels of Infectious Virus in Respirable Aerosols Exhaled by Ferrets Infected with Influenza Viruses Exhibiting Diverse Transmissibility Phenotypes

Influenza viruses pose a major public health burden to communities around the world by causing respiratory infections that can be highly contagious and spread rapidly through the population. Despite extensive research on influenza viruses, the modes of transmission occurring most often among humans are not entirely clear. Contributing to this knowledge gap is the lack of an understanding of the levels of infectious virus present in respirable aerosols exhaled from infected hosts. Here, we used the ferret model to evaluate aerosol shedding patterns and measure the amount of infectious virus present in exhaled respirable aerosols. By comparing these parameters among a panel of human and avian influenza viruses exhibiting diverse respiratory droplet transmission efficiencies, we are able to report that ferrets infected by highly transmissible influenza viruses exhale a greater number of aerosol particles and more infectious virus within respirable aerosols than ferrets infected by influenza viruses that do not readily transmit. Our findings improve our understanding of the ferret transmission model and provide support for the potential for influenza virus aerosol transmission.     

Methylated lysine in storage body protein of sheep with hereditary ceroid-lipofuscinosis.

Juvenile ceroid-lipofuscinosis (Batten disease) is a hereditary storage disease with an autosomal-recessive mode of transmission. This disorder has been identified in humans, dogs and sheep. It is characterized by massive accumulations of autofluorescent storage bodies in many tissues. This storage body accumulation is accompanied by functional decline and degeneration of the affected tissues, and ultimately results in premature death. The primary defect responsible for juvenile ceroid-lipofuscinosis has not been identified. Previous studies have indicated that the storage material is primarily protein. Why this protein accumulates in storage bodies remains to he determined. In affected humans, the storage body protein appears to be abnormally rich in a methylated derivative of lysine (epsilon-N-trimethyllysine). Studies were undertaken to determine whether the storage bodies from sheep with hereditary ceroid-lipofuscinosis were also characterized by the presence of this modified amino acid. Chromatographic and mass spectral analyses of hydrolysates of the storage body protein indicated a significant fraction of the lysine residues in this protein were present as the epsilon-N-trimethyl derivative. This modified amino acid was not detected in hydrolysates of protein from normal sheep tissues or from tissues of sheep with GM1 gangliosidosis, nor did it appear to be present in the storage body protein from a human subject with the late infantile form of ceroid-lipofuscinosis. Thus, it is apparently specific to the storage body protein that accumulates in the juvenile type of this disease. The abnormal presence of epsilon-N-trimethyllysine in proteins could interfere with their sorting or degradation within cells and thus cause them to accumulate in the storage bodies characteristic of the human juvenile and ovine ceroid-lipofuscinoses.     

Antiinflammatory effects of polypeptide growth factors. Platelet-derived growth factor, epidermal growth factor, and fibroblast growth factor inhibit the cytokine-induced expression of the alternative complement pathway activator factor B in human fibroblasts.

The synthesis of complement components in human fibroblasts is modulated by mediators of inflammation such as cytokines. In particular, interleukin-1 (IL-1) and tumor necrosis factor (TNF) induce time- and dose-dependent increases in the synthesis of complement proteins factor B (FB), C3, and factor H (FH). Polypeptide growth factors are also soluble mediators released during inflammation and able to modulate many fibroblast functions. We have studied the effects of polypeptide growth factors platelet-derived growth factor (PDGF), epidermal growth factor (EGF), and fibroblast growth factor (FGF) on the synthesis of complement proteins in cultured human fibroblasts. PDGF, EGF, and FGF alone did not affect the level of synthesis of any of the complement proteins analyzed, but simultaneous incubation of PDGF, EGF, or FGF with IL-1 and TNF resulted in a dose-dependent inhibition of the cytokine-enhanced expression of FB. Inhibition of FB synthesis was observed between 4 and 8 h of exposure to PDGF and persisted for 4 h after the removal of the growth factor. Analysis of steady-state levels of specific FB mRNA suggested that PDGF-induced inhibition of FB synthesis is mediated at a pretranslational level and that it requires new protein synthesis. The effect of the growth factors was limited to FB, with marginal or no inhibition on the cytokine-enhanced synthesis of C3 and FH, excluding the possibility that the inhibitory effects of PDGF, EGF, and FGF on FB synthesis were due to a negative modulation of the growth factors on cytokine cell membrane receptors. Specific inhibition of cytokine-induced increases in FB synthesis by the growth factors may represent down regulation of the acute inflammatory process, further permitting progression to processes of tissue repair and remodeling. Study of the interactions between cytokines and growth factors in the regulation of synthesis of complement proteins may also provide a system for investigating mechanisms of signal transduction of both polypeptide growth factors and cytokines.