Toxoplasma Gondii Surface antigen-1 in Sera of HIV-infected Patients as an Indicator of Reactivated Toxoplasmosis

Eur J Clin Microbiol Infect Dis. 1995 Oct;14(10):899-903. doi: 10.1007/BF01691497.


The major surface antigen from the proliferative form of Toxoplasma gondii (P-30 of SAG-1) was chosen as a target for exploration of Toxoplasma gondii reactivation in sera from immunocompromised patients. Samples were obtained from 37 HIV-infected subjects with lymphocyte levels of CD4+ < 200/mm3. The prevalence of IgG antibodies to Toxoplasma gondii was 64.9%. Ten patients had clinical symptoms of reactivated toxoplasmosis; eight of these had Toxoplasma encephalitis. The SAG-1 epitopes were found as circulating antigen in five cases with an immunocapture enzyme immunoassay (EIA). The EIA was improved with an IgG1 monoclonal antibody to SAG-1 and a streptavidinbiotin amplification. The sensitivity, specificity and positive predictive value were 30, 92 and 60%, respectively. The SAG-1 levels were compared with different biological parameters such as HIV p24 antigen, beta 2 microglobulin, CD4+ cell count and IgG antibodies to Toxoplasma gondii. The levels of SAG-1 in these patients were significantly higher than those in the 75 healthy control persons with or without a chronic Toxoplasma gondii infection. Therefore, SAG-1 may be involved as a marker of reactivated toxoplasmosis in HIV-infected patients.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • AIDS-Related Opportunistic Infections / diagnosis*
  • Adult
  • Animals
  • Antibodies, Protozoan / blood
  • Antigens, Protozoan / blood*
  • Female
  • HIV-1*
  • Humans
  • Male
  • Protozoan Proteins / blood*
  • Toxoplasma / immunology*
  • Toxoplasmosis / diagnosis*


  • Antibodies, Protozoan
  • Antigens, Protozoan
  • Protozoan Proteins
  • SAG1 antigen, Toxoplasma