Prevalence and genotype distribution of TT virus in various specimen typesfrom thalassaemic patients

Peripheral blood mononuclear cells (PBMC), plasma, saliva and urine samples were collected from 50 thalassaemic patients for TT virus (TTV) detection by two sets of PCR. The set B nested PCR was more sensitive than the widely used NG hemi-nested PCR with TTV positive rates approximate to PBMC: 98% v s. 70%; plasma: 92% vs. 66%; saliva: 62% vs. 22%; urine: 22% vs. 6%. All 50 patients had TTV detected in one or more specimens, with 16% of patients b eing positive in all four specimen types: 40% positive in PBMC, plasma and saliva; 30% positive in PBMC and plasma. In 82 NG hemi-nested PCR-positive samples TTV genotype was identified, 68.3% had a single genotype, 25.6% had multiple genotypes and 6.1% were uncharacterized. The positive rates for g enotypes by specimen were: G1 (36/82), G2 (49/82), G3 (2/82), G4 (7/82), G5 (1/82) and G6 (3/82). Among the 42 patients for whom the genotype was exam ined, 42.9% had single-type infection, 45.2% had co-infections and 11.9% ha d uncharacterized genotypes. Sixteen of them had TTV detected both in PBMC and plasma with seven having identical genotypes in both samples. Eight pat ients had TTV detected in PBMC, plasma and saliva; two of them harboured id entical genotypes in all three samples. The results indicate that, apart fr om hepatocytes, PBMC is a major cell type for TTV infection occurs. Sheddin g of TTV in urine and saliva is common and may have a significant role in n onblood-borne transmission among the general population. TTV-infected patie nts often harbour multiple genotypes suggesting infection with one genotype does not necessarily confer protection against the others. No correlation between TTV infection and liver dysfunction was observed.