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Biomedical subjects

R Trautman

Publications and source records attributed to R Trautman.

At least 19 recordsLinked to original sources
PubMed1980

Sedimentation coefficient of African swine fever virus.

The sedimentation coefficient of the infective unit of African swine fever in tissue culture harvest fluids was measured in a preparative ultracentrifuge. The boundary locator method used also permitted making an estimate of heterogeneity. The sedimentation coefficient ranged from 3,000 to 8,000 Svedberg units, representing many classes of infective particles. Electron microscopy on culture fluids from infected cells showed many kinds of virus-containing units. Sucrose-CsCl gradient centrifugation was used to concentrate and to purify (partly) African swine fever virus for analytical ultracentrifugation. The optical patterns of the physical particles revealed a range of coefficients from 1,800 to 3,200 Svedberg units in tris-buffered saline solution at 20 C and buoyant densities from 1.19 to 1.24 g/ml in CsCl. The disparity of these values from those obtained by preparative ultracentrifugation indicates a change in the virus structure or a selection of viral populations on purification (or both).

African Swine Fever Virus↗
PubMed1979

Resolution of block neutralization test curves into components of the foot-and-mouth disease virus system.

Classic neutralization studies by Fazekas de St. Groth and Webster (8) on mixtures of influenza viruses and mixtures of rabbit antisera are reinterpreted in terms of a percentage contaminant in the stock used for the dilution series. A very small amount of a different virus changes the shape of quantal assay curves considerably, but even a large amount of a different antiserum has negligible effect on the shape and merely shifts the curve along the serum dilution axis. These conclusions are the reverse of the authors, who only considered an absolute amount of another component in all dilution tubes. An artificial mixture of 2.7 percent O8 in O1 foot-and-mouth disease virus strains was tested against anti-O1 serum assaying in suckling mice. The small amount of O8 virus greatly altered the shape of the neutralization curve in the direction expected from the reanalysis of the influenza literature data. Results from artificial mixtures are used to explain what were hitherto anomalously broad neutralization curves for some other foot-and-mouth disease strains given by Booth et al. (1) Many of the virus stocks studied can now be postulated as a natural mixture of related virus strains. In fact, the O1 and O8 stocks used might also be of themselves mixtures. These virus strains also exhibit still a further test complication in that the virus-antibody reaction appeared to shift away from complexes on dilution immediately prior to assay.

Antigen-Antibody Reactions↗
PubMed1979

Relationship between virus neutralization and serum protection bioassays for IgG and IgM antibodies to foot-and-mouth disease virus.

The time interval between administering the serum and the virus was found to influence the results of the in vivo mouse protection test for foot-and-mouth disease antibodies. In particular, for both IgG and IgM antibodies to strain A12 virus, the mouse protection index increased from zero to a maximum at about 6 h and remained high for at least five days. Variations in the antiserum concentration, on a log scale, had a proportional effect on the mouse protection index, if between 1 and 3. The constant of proportionality was unity for IgM and 2 for IgG antibody. Comparison with in vitro neutralization tests revealed essentially parallel neutralization curves. The lower serum titre in the protection test, if computed for less than 10(3) LD50/dose, was accounted for by the simple dilution of the inoculated serum into the volume of the mouse. Consequently, in the low titre range, the same virus-antibody reaction and its effect are operable in each of the two tests. Analysis of literature data in which both the in vivo protection test and the in vitro neutralization test results were available on the same sera showed consistency with the above conclusions for both cattle and swine sera. The protection test had a highly atypical survival pattern occurring at antibody concentrations expected to neutralize more than 10(3) LD50/dose. The resulting in vivo dampening effect on virus titre is postulated to be caused by the excess antibody of the passive immunity test interfering with the spread of infection. The effect is analogous to an anomaly caused by not removing the inoculum in quantal tissue culture assays and it prevents quantification of antibody levels in strong sera.

Animals↗
PubMed1977

Modeling and computer stimulation approach to the mechanism of foot-and-mouth disease virus neutralization assays.

Block neutralization data since 1949 for the foot-and-mouth disease virus system have been analyzed in terms of a unified mass-action theory for computing the amounts of infectious complexes. Proof that infectious complexes contribute considerably to the assays was obtained by demonstrating a reduction in titer after an additional reaction with anti-Ig antibody before the assay. In the suckling-mice assay with intraperitoneal inoculation, both the data of others and our own on several types indicate that for IgG probably three of the unknown total number of critical sites on the virion must be available for infectivity and death. For IgM, just one of an unknown different total number of critical sites on the virion must be available. In tissue culture infectivity assays the minimum number is two or three, whereas in the bovine tongue assay it could be one or two, but probably two. The difficulties in establishing the at present unknown total numbers of neutralization sites to both IgG and IgM are considerable. However, by the simplest interpretation of the data, the number is estimated to be between 5 and 10 for IgG and perhaps just 1 for IgM. A speculation, consistent with the known virion architecture, is that just 1 of the 12 vertices is uniquely involved in infectivity and death, at least in the suckling-mice assay.

Animals↗
PubMed1976

Unified mass-action theory for virus neutralization and radioimmunology.

All ideas implicit in the papers since 1953 involved in applying mass-action thermodynamics to antibody-antigen reactions are unified by the use of: (a) the intermediary concept of extent of reaction; (b) the concept of intrinsic association constant; (c) a statistical analysis for probable complexes; and (d) identification of the complex or complexes that contribute to the bioassay. Several general theoretical examples are given that show the limitations of linear interpretations of equilibrium data. Two practical examples from the literature illustrate foot-and-mouth disease virus and influenza virus neutralization.

Antigen-Antibody Complex↗
PubMed1974

Immunofluorescence plaque assay for African swine fever virus.

Suitably diluted cell culture adapted African swine fever virus preparations were inoculated on VERO cell monolayers and grown on coverslips. Gum tragacanth was used as an overlay. After three days incubation at 37 degrees C the infected cultures were fixed with acetone and stained with fluorescent antibody conjugate. Fluorescing plaques consisted of 20-30 infected cells. THREE STATISTICAL CRITERIA FOR A QUANTITATIVELY RELIABLE ASSAY WERE MET: the Poisson distribution for plaque counts, linearity of the relationship between the concentration of virus and the plaque count and reproducibility of replicate titrations. The method is suitable for counts up to at least 70 plaques per 5 cm(2) coverslip and computed titers are reproducible within 0.16 log units with a total of 300 plaques enumerated.

African Swine Fever↗
PubMed1972

Computer simulation of radial immunodiffusion. I. Selection of an algorithm for the diffusion process.

Theories of diffusion with chemical reaction are reviewed as to their contributions toward developing an algorithm needed for computer simulation of immunodiffusion. The Spiers-Augustin moving sink and the Engelberg stationary sink theories show how the antibody-antigen reaction can be incorporated into boundary conditions of the free diffusion differential equations. For this, a stoichiometric precipitate was assumed and the location of precipitin lines could be predicted. The Hill simultaneous linear adsorption theory provides a mathematical device for including another special type of antibody-antigen reaction in antigen excess regions of the gel. It permits an explanation for the lowered antigen diffusion coefficient, observed in the Oudin arrangement of single linear diffusion, but does not enable prediction of the location of precipitin lines. The most promising mathematical approach for a general solution is implied in the Augustin alternating cycle theory. This assumes the immunodiffusion process can be evaluated by alternating computation cycles: free diffusion without chemical reaction and chemical reaction without diffusion. The algorithm for the free diffusion update cycle, extended to both linear and radial geometries, is given in detail since it was based on gross flow rather than more conventional expressions in terms of net flow. Limitations on the numerical integration process using this algorithm are illustrated for free diffusion from a cylindrical well.

Antigen-Antibody Reactions↗