Two new genotypes of Plasmodium vivax circumsporozoite protein found in the Republic of Korea

Abstract

The gene encoding Plasmodium vivax circumsporozoite protein (PvCSP) exhibits polymorphism in many geographical isolates. The present study was designed to investigate polymorphism in PvCSP gene of P. vivax isolates in Korea. Thirty isolates, obtained from indigenous cases in Yonchon-gun, Kyonggi-do in 1997, were subjected for sequencing and RFLP analysis of the repeat and post-repeat regions of PvCSP gene and two genotypes (SK-A and SK-B) were identified. The genotype of 19 isolates was SK-A and that of 11 isolates was SK-B. Although the number of 12-base repeats present in SK-A was three while two were found in a Chinese strain CH-5, the repeat sequence of SK-A was identical to that of CH-5 except for one base substitution. Compared with known data there was no identical isolates with SK-B, but the sequence of SK-B was similar to that of a North Korean (NK) isolate. These results indicate that two genotypes of PvCSP coexist in the present epidemic area of Korea and the present parasite may originate from East Asia. RFLP would be useful to classify genotypes of P. vivax population instead of gene sequencing.

Fig. 1

Schematic presentation of the Plasmodium vivax CSP gene. The relative positions of primers for PCR (PVF1, PVR1, PVF2 and PVR2) and sequencing (PVF3 and PVR2) are indicated beneath the map.

Fig. 2

PCR of the PvCSP gene from Korean isolates. PCR products were resolved by electrophoresis on a 1.2% agarose gel and stained with ethidium bromide. M, 100 bp marker; lane 1, SK-A type; lane 2, SK-B type.

Fig. 3

The nucleotide sequences of the PvCSP gene of South Korean isolates compared to the NK and China groups. Repeats are numbered and the sequences read from 5' to 3', starting at the first base of the first numbered tandem repeat to the last codon in the last numbered repeat. The predicted amino acid is given above the nucleotide sequence. The sequences are compared to the NK isolate and CH-5 (Mann et al., 1994).

Fig. 4

Variation in the nucleotide sequences of end of the last 27-bp repeat, 36-bp insert and 12-bp repeat. The sequence of post-repeat region of PvCSP was compared with NK, CH2-7, PH79, VK210, SOL-83, SOL-101, Belem and NYUThai (Mann et al., 1994). The bold numbers indicate 12 bp repeat. Shaded squares reveal identical sites.

Fig. 5

RFLP patterns of the PvCSP gene from Korean isolates. RFLP was performed using PvuII (CAG/CTG) restriction enzyme. M, marker; lane 1, undigested SK-A; lane 2 and 3, digested SK-A; lane 4, undigested SK-B; lane 5 and 6, digested SK-B.