Transfusion-Transmitted Virus (TTV)：Positive Rates in Healthy Individuals and Cases with Hepatitis C Antibody
2001 Vol.17 NO.10
Transfusion-transmitted virus (TTV) was first detected and reported by Nishizawa in 1997. Three years later, with more reports coming from all corners of the world, TTV was found to be similar to HGV. The virus exists extensively in human body, and is transmitted primarily through body fluid, though the likelihood of transmission via mouth should not be overlooked. TTV infection is not directly associated with the pathogenic agents of hepatitis. Prevalence of TTV varies with different geographic regions and studies, ranging from 10% to 80-90%. Several studies have been reported from Taiwan. The purpose of the present study was to verify whether the positive rates in Taiwan were different from those reported elsewhere. Both polymerase chain reaction and gene sequencing methods were applied to analyze the infections of TTV-DNA in three study groups: (1) 300 healthy individuals (ALT normal, average age 25.8 years), (2) 53 anti-HCV positive, ALT normal cases (36 males and 17 females, average age 34.5 years), and (3) 300 anti-HCV positive, ALT abnormal cases (148 males and 152 females, average age 36.4 years). TTV-DNA was measured by polymerase chain reaction, and their genotypes were analyzed by gene sequencing method. TTV-DNA positive rates were 9% and 31% (p<0.05) respectively in the anti-C negative and positive groups, indicating some association between TTV-DNA infection and hepatitis C virus infection. Whether ALT was normal or not, it was not associated with the TTV-DNA positive rate. The main genotype of TTV-DNA in the cases studied was type-1 (accounting for about 73%); and the subtypes were genotype IA (53%) and genotype IB (47%). The present study had also detected four thus far not reported subtypes. The TTV-DNA positive rates in the healthy individuals and anti-HCV positive cases in the present study were somewhat different from rates reported elsewhere in the world and in Taiwan, indicating, as commonly understood, that TTV infection rates differed from place to place and in different groups. Whether the infection was associated with hepatitis C virus infection remained to be studied further. The detection of four new genotypes showed the diversity of TTV genotypes and subtypes.