Detection of HTLV-II-seropositive blood donors in South Vietnam but not in North Vietnam

Seroprevalence of HTLV-1/2 Among Voluntary Blood Donors in Vietnam

Infection with human T lymphotropic virus (HTLV), although asymptomatic in most cases, can lead to severe illnesses, such as adult T cell leukemia/lymphoma or myelopathy/tropical spastic paraparesis. HTLV can be transmitted by whole-blood (WB) transfusion. The prevalence of HTLV among blood donor populations has not been characterized in Vietnam, although the screening has been partially implemented on voluntary basis since 2016. To determine the seroprevalence of HTLV-1/2 among blood donors, a total of 14,819 healthy blood donors in northern, central, and southern Vietnam and 1,003 samples from hepatitis B surface antigen (HbsAg), anti-hepatitis C (anti-HCV), or HIV Ag/Ab reactive blood donors were screened for anti-HTLV-1/2 antibodies by a chemiluminescence immunoassay using the Abbott ARCHITECT rHTLV-I/II assay. The anti-HTLV-1/2 repeat reactive (RR) samples were further tested by immunoblot (IB) method using MP Biomedicals HTLV Blot 2.4 for confirmation and differentiation of HTLV-1/2 infection. Proviral HTLV subgenomic amplification of the gag and tax regions was performed on the available WB RR samples (N = 11) by polymerase chain reaction (PCR). Among 14,819 blood donors, 34 samples (0.23%) were RR for anti-HTLV-1/2 antibodies, but only 1 case was confirmed HTLV-2 positive (0.0067%) and 5 cases were classified as indeterminate (0.034%) by IB. The RR rate was 0.39% among HBsAg/anti-HCV/HIV reactive sample groups, but none of them was confirmed by IB. Subgenomic PCR failed to amplify proviral DNA from WB samples of 11 RR samples. HTLV-1/2 prevalence was found to be low among blood donors in the study. Continued vigilance remains essential to maintain a low transfusion-transmitted risk in Vietnam.

Nucleotide sequence variation of human T-lymphotropic virus type II in Vietnam

A high rate of human T-lymphotropic virus type II (HTLV-II) infection has been documented in intravenous drug abusers (IVDAs) in South Vietnam. We have investigated the molecular characteristics of the virus and have shown that one HTLV-II subtype is predominant in Ho Chi Minh City. This molecular subtype, HTLV-IIb, was identified in a number of South Vietnamese by nucleotide sequence analysis of the long terminal repeat (LTR) region. HTLV-IIa was not found. These findings suggest that HTLV-IIb is endemic in IVDAs in South Vietnam, although IVDAs in urban areas in North America are predominantly infected with HTLV-IIa.

No proof of HTLV-I/II in intravenous drug abusers with a high rate of HIV-1 infection in central Thailand

Serum specimens of 1,074 intravenous drug abusers (IVDA) were examined for infection with HIV-1, HTLV-I and HTLV-II in central Thailand. Three hundred and sixty-two of the specimens were seropositive for HIV-1 (33.7%). The HIV-1 seropositive IVDAs exhibited increased seropositivity with age through group 40-44 and significantly decreased seropositivity over the age of 45. In contrast, no seropositivity to either HTLV-I or -II was detected in the samples tested by a particle-agglutination assay for HTLV followed by type-specific Western blotting for HTLV. Reference to previous reports suggested that the rate of HIV infection in IVDAs has decreased with no HTLV-I or HTLV-II in Thailand when compared with that of the HIV infection in 1992.

Human T-lymphotropic virus type II in Japan

Serum specimens were assayed for human T-lymphotropic virus type II(HTLV-II) infection in 1,500 individuals known to be seropositive for HTLV-I and 30,000 blood donors in Japan. All HTLV-I-positive individuals were negative for HTLV-II. However, one of the blood donors was clearly seropositive for HTLV-II. Further, the donor was shown to be positive for HTLV-IIb. Here we report at least one case with HTLV-II in Japan and discuss the origin of the infection.