A new alternative in vitro method for quantification of Toxoplasma gondii infectivity

J Parasitol. 2011 Oct 19. [Epub ahead of print]

A new alternative in vitro method for quantification of Toxoplasma gondii infectivity.

Useo R, Husson F, De Coninck J, Khaldi S, Gervais P.

Sourcea AgroSup Dijon, Université de Bourgogne, AgroSup Dijon, Université de Bourgogne.

Abstract
Abstract An in vitro method to determine the infectious potency of an unknown suspension of the protozoan parasite Toxoplasma gondii based on kinetics of host cells lysis was developed. Mic1-3KO a mutant strain of Toxoplasma gondii RH tachyzoïtes were inoculated in 25-cm² flasks containing a 90% confluent monolayer of Human Foreskin fibroblast. Lysis kinetics was monitored for infection ratios ranging from 1:10⁶ to 1:10¹ and the threshold value for parasite egress was defined at 10⁶ tachyzoites.ml-¹. Results allowed to build a calibration curve relating the initial infection ratios to the time needed to reach 10⁶ tachyzoites.ml-¹. Finally, the method was validated using of a known mixture of dead and live parasites. This method was found to estimate with accuracy the initial ratio of infection of an unknown parasites suspension. This easy-to-use method is reproducible and application to any Toxoplasma gondii tachyzoïtes RH strain, genetically modified or not. This method is suitable for testing promising candidates for an effective live vaccine.

PMID:22010815[PubMed - as supplied by publisher]