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Journal of Clinical Microbiology, Sep 1995, 2297-2303, Vol 33, No. 9
TJ Inzana
A novel, inexpensive method for obtaining immunoglobulin G (IgG) specific
for capsular antigen is described for use in latex agglutination tests.
Hyperimmune rabbit serum against encapsulated Actinobacillus
pleuropneumoniae was thoroughly adsorbed with a nonencapsulated mutant. The
capsule titer of the absorbed serum was unaffected, whereas reactivity to
nonencapsulated cells was reduced to background levels, as determined by
enzyme immunoassay. The IgG component of the adsorbed serum was recovered
by protein A chromatography and was covalently coupled through a
water-soluble carbodiimide to carboxylate latex beads. The sensitized latex
particles (SLP) were agglutinated by 10 ng of homologous capsule or more
per ml, were not agglutinated by heterologous capsules at concentrations of
< 10 micrograms/ml, and were stable for over 1 year at 4 degrees C
without loss of sensitivity. There was no difference in the sensitivity or
specificity of latex particles coupled with IgG purified by capsule
affinity chromatography. The SLP were agglutinated by all strains of
bacteria of the homologous serotype but not by heterologous serotypes or
strains of Pasteurella multocida, Actinobacillus suis, or Haemophilus
parasuis tested at a density equivalent to a 0.5 McFarland standard. The
SLP detected homologous capsule in lung tissue, nasal swabs, and
concentrated urine samples from all pigs culture positive for A.
pleuropneumoniae but one. Precoating of carboxylate latex particles with
avidin followed by conjugation of biotin-hydrazide- labelled IgG to capsule
increased the sensitivity of the assay approximately 10-fold. Adsorption of
serum with nonencapsulated mutants may be used to prepare SLP with optimum
sensitivity and specificity without the need to purify capsule or couple
capsule to affinity columns.
Copyright © 1995 by the American Society for Microbiology. All rights reserved.
Simplified procedure for preparation of sensitized latex particles to detect capsular polysaccharides: application to typing and diagnosis of Actinobacillus pleuropneumoniae
Center for Molecular Medicine and Infectious Diseases, Virginia- Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg 24061-0342, USA.
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