Nucleotide sequence analysis of HTLV-I isolate from a Korean patient with HAM/TSP

Epidemiological Aspects and World Distribution of HTLV-1 Infection

The human T-cell leukemia virus type 1 (HTLV-1), identified as the first human oncogenic retrovirus 30 years ago, is not an ubiquitous virus. HTLV-1 is present throughout the world, with clusters of high endemicity located often nearby areas where the virus is nearly absent. The main HTLV-1 highly endemic regions are the Southwestern part of Japan, sub-Saharan Africa and South America, the Caribbean area, and foci in Middle East and Australo-Melanesia. The origin of this puzzling geographical or rather ethnic repartition is probably linked to a founder effect in some groups with the persistence of a high viral transmission rate. Despite different socio-economic and cultural environments, the HTLV-1 prevalence increases gradually with age, especially among women in all highly endemic areas. The three modes of HTLV-1 transmission are mother to child, sexual transmission, and transmission with contaminated blood products. Twenty years ago, de Thé and Bomford estimated the total number of HTLV-1 carriers to be 10-20 millions people. At that time, large regions had not been investigated, few population-based studies were available and the assays used for HTLV-1 serology were not enough specific. Despite the fact that there is still a lot of data lacking in large areas of the world and that most of the HTLV-1 studies concern only blood donors, pregnant women, or different selected patients or high-risk groups, we shall try based on the most recent data, to revisit the world distribution and the estimates of the number of HTLV-1 infected persons. Our best estimates range from 5-10 millions HTLV-1 infected individuals. However, these results were based on only approximately 1.5 billion of individuals originating from known HTLV-1 endemic areas with reliable available epidemiological data. Correct estimates in other highly populated regions, such as China, India, the Maghreb, and East Africa, is currently not possible, thus, the current number of HTLV-1 carriers is very probably much higher.

Seroprevalence of human T-lymphotropic virus type 1 and 2 in Korean blood donors

The seroprevalence rate of human T-lymphotropic virus (HTLV) among the Korean blood donor population was studied to determine whether screening for HTLV should be implemented. A total of 15,173 serum samples collected from June to July 2006 at five Blood Centers which are located closely to Japan geographically, where the prevalence of HTLV is known to be high, were tested. Serological screening was done by a chemiluminescence method. Samples reactive repeatedly on serological screening were confirmed further by Western blot, line immunoassay, nested polymerase chain reaction and sequencing of proviral DNA. Six samples tested reactive with the serological assay showing a reactive rate of 0.004%. Among the six samples, one sample was confirmed as HTLV-1 positive, giving a confirmed reactive rate of 0.007%. Based on the results of this study, an extended study will be conducted to evaluate whether introduction of HTLV screening is necessary in Korea.

Genotyping of the JC virus in urine samples of healthy Korean individuals

A human polyomavirus, JC virus (JCV) is ubiquitous in humans and infects children asymptomatically. It persists in renal tissue and is excreted progeny in urine. DNAs from urine samples of 100 healthy Korean individuals were screened for the presence of JCV by polymerase chain reaction (PCR). Twenty of the samples were positive for JCV. JCV DNA was found in one individual (4%) in the 1-19-year group, two individuals (9%) in the 20-39-year group, ten individuals (38%) in the 40-59-year group, seven individuals (28%) in the over 60-year group. The prevalence of JC viral DNA was the highest in the 40-59-year-old Korean population. To investigate genotypes of JCV in Korea, the genotypes were determined by DNA sequence analysis of the regulatory region (333 bp) and the VT-intergenic region (656 bp) of DNA from the 20 JCV isolates. We have identified three distinctive JCV strains in the regulatory region and ten distinctive JCV strains in the VT-intergenic region of DNA from the 20 isolates. Based on restriction fragment length polymorphism (RFLP) analysis and phylogenetic analysis of the VT-intergenic region of JCV, two distinct subtypes, CY and type 2A (MY), were found to be prevalent in this Korean population. CY and type 2A of JCV were identified in 13 individuals (65%) and four individuals (20%), respectively. Interestingly, type 1, which was distributed mostly in Europe, was found in 3 (15%) isolates from healthy Korean individuals.