Murine typhus toxin: studies on identification of the neutralizing factor present in normal human serum

Infect Immun. 1972 Sep;6(3):232-9. doi: 10.1128/iai.6.3.232-239.1972.


Studies were made on the isolation and identification of the Rickettsia typhi toxin-neutralizing factor (TNF) previously demonstrated in normal human serum. By means of various methods of separating serum proteins, such as filtration on Sephadex G-200, dextran precipitation, hydroxyapatite chromatography, and ultracentrifugation, TNF was found to be closely associated with purified serum beta-lipoprotein, although no serological relationship with this protein was demonstrated. Lipase as well as trypsin digestion of purified preparations of beta-lipoprotein destroyed the TN activity. No evidence was obtained for an association of TNF with the immunoglobulins or with any serum protein other than beta-lipoprotein. Further studies revealed that (i) serum specimens with TN titers of 1:1024 and others with titers of 1:8 or less contained the same concentration of beta-lipoprotein; (ii) purified preparations of beta-lipoprotein isolated from TNF positive and negative sera, and which had the same protein concentration, differed as much as 250-fold in TN titer; and (iii) the TN activity of a serum could be removed by absorption with antiserum to beta-lipoprotein from a positive donor, but not with antiserum to beta-lipoprotein from a negative donor.

MeSH terms

  • Agglutination Tests
  • Animals
  • Antitoxins / isolation & purification*
  • Chromatography
  • Chromatography, Gel
  • Complement Fixation Tests
  • Humans
  • Hydroxyapatites
  • Immune Sera
  • Immunodiffusion
  • Immunoglobulin G / analysis
  • Immunoglobulin M / analysis
  • Lipase
  • Lipoproteins / isolation & purification
  • Mice
  • Neutralization Tests
  • Rabbits / immunology
  • Rickettsia typhi / immunology
  • Trypsin
  • Typhus, Endemic Flea-Borne / immunology*
  • Ultracentrifugation


  • Antitoxins
  • Hydroxyapatites
  • Immune Sera
  • Immunoglobulin G
  • Immunoglobulin M
  • Lipoproteins
  • Lipase
  • Trypsin