Laboratory passage and characterization of an isolate of Toxoplasma gondii from an ocular patient in Korea

Abstract

Toxoplasma gondii tachyzoites were isolated from the blood of an ocular patient, and have been successfully passaged in the laboratory, for over a year, by peritoneal inoculation in mice. The isolated parasite was designated the Korean Isolate-1 (KI-1) and its characteristics were compared with those of the RH strain, a wellknown virulent strain originating from a child who suffered from encephalitis. The morphology, pathogenicity, infectivity and cell culture characteristics of the KI-1 were similar to those of the RH strain. Both RH and KI-1 antigens were detected by an anti-T. gondii monoclonal antibody (mAb), Tg563, against the major surface protein SAG1 (30 kDa), whereas no reaction was observed against an anti-Neospora caninum mAb, 12B4. The KI-1 was confirmed as an isolate of T. gondii. A long-term laboratory maintenance and characterization of a local T. gondii isolate is reported for the first time in the Republic of Korea.

Figs. 1-2

The Korean Isolate-1 (KI-1) tachyzoites of Toxoplasma gondii isolated from an ocular patient. Giemsa stained. Scale bar = 12 µm. Fig. 2. The KI-1 tachyzoites of T. gondii in the Sarcoma 180 cell line cultured in vitro. Giemsa stained. Scale bar = 10 µm.

Fig. 3

TEM morphology of a KI-1 tachyzoite. The nucleus has dense chromatins in the center and along the nuclear wall, and are easily differentiated from the cytoplasm. Characteristic organelles such as the nucleus (N), rhoptries (R), electron dense granules (EG), vacuoles (V) and mitochondria (M) are seen. Scale bar = 0.5 µm.

Fig. 4

Immunoblot of the RH and KI-1 of T. gondii and Neospora caninum KBA2 antigens, with the anti-Toxoplasma monoclonal antibody (mAb) Tg563 and anti-Neospora mAb 12B4. The RH, KI-1 and KBA2 antigens were reacted with the 12B4 (Lanes 1, 2 and 3), and the RH, KI-1 and KBA2 antigens were reacted with the Tg563 (Lanes 4, 5 and 6).