Use of dense granule antigen GRA6 in Immunoglobulin G avidity test to exclude acute Toxoplasma infection during pregnancy

Clin Vaccine Immunol. 2010 Jul 14. [Epub ahead of print]

Use of dense granule antigen GRA6 in Immunoglobulin G avidity test to exclude acute Toxoplasma infection during pregnancy

Elyasi H, Babaie J, Fricker-Hidalgo H, Brenier-Pinchart MP, Zare M, Sadeghiani G, Assmar M, Pelloux H, Golkar M.

Molecular Parasitology Laboratory, Parasitology Department, Pasteur Institute of Iran, Tehran, Iran; Parasitology Department, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran; Parasitology and Mycology Laboratory, Grenoble Teaching Hospital A Michallon, BP 217, 38043 Grenoble Cedex 09, France; Laboratoire Adaptation et Pathogénie des Microorganismes, CNRS UMR 5163, Joseph Fourier University (Grenoble I), BP 170, 38042 Grenoble Cedex 09, France.

Abstract
Usefulness of a specific immunoglobulin G (IgG) avidity enzyme-linked immunosorbent assay based on recombinant GRA6 antigen was investigated for distinguishing between acute and chronic Toxoplasma infection. Two sets of sera from pregnant women with acute, chronic or no Toxoplasma infection collected in France and Iran were used. Among French subjects, 19 of 20 (95%) women experiencing seroconversion during the past 4 months before sampling displayed low avidity IgG antibodies against GRA6, while all 17 (100%) women with chronic infection had high avidity antibodies. When Euroimmun IgG avidity ELISA was used, 15 of 19 (78.9%) recently-infected women had low avidity antibodies and 20 of 22 (90.9%) women with chronic infection displayed high avidity antibodies. The results suggested better performance of GRA6 avidity than Euroimmun avidity ELISA for exclusion of a recent infection occurred less than 4 months before. Similarly, all 35 Iranian women with acute Toxoplasma infection had low avidity antibodies against GRA6, whereas all 34 women with chronic infection displayed IgG antibodies of high avidity, indicating value of GRA6 avidity testing for ruling out a recent infection. Avidity tests based on lysed whole-cell T. gondii antigen are currently used to exclude recently acquired infections; however, the use of recombinant antigen(s) might improve diagnostic performance of avidity tests and facilitate development of more standardized assays.

PMID: 20631335 [PubMed - as supplied by publisher]