HTLV antibody in China

Genetic typing and intrafamilial transmission of human T-lymphotropic virus type 1 in non-endemic areas of China

The origin and intrafamilial transmission of Human T-Lymphotropic Virus Type 1 (HTLV-1) in non-endemic populations such as China is still unknown. In this study, donors from blood banks/centers in China (including 28 provinces and Shenzhen city) during 2019 and 2021 were screened for HTLV-1/2 antibody, and all the reactive samples were tested using a line immunoassay (LIA) and quantitative polymerase chain reaction (qPCR). Samples that can be detected using qPCR were amplified and sequenced for the long terminal repeat (LTR) region. The positive donors were contacted to identify their relatives. As a result, 4,451,883 blood donors were totally tested, and 50 of them were confirmed to be HTLV-1/2 positive. Viral LTR sequences genotyped from 26 HTLV-1 carriers demonstrated that all had the HTLV-1a genotype, of which Transcontinental and Japanese subgroups accounted for half each. There were 17 family members of 11 index donors detected, and the HTLV-1 infection rate in the spouses of male index donors (83.3%, 5/6) was significantly higher than that in the husbands of female index donors (0.0%, 0/4). However, 7 children of HTLV-1 positive women were tested and found negative. Therefore, our findings indicated that HTLV-1 is spreading silently from high-endemic to low-endemic areas in China. To prevent further HTLV-1/2 transmission, an efficient HTLV-1/2 screening strategy and counseling of the virus carriers are essential.

History and update of HTLV infection in China

Human T-lymphotropic virus (HTLV) infection is a high risk factor for lymphoproliferative, inflammatory, and infectious disorders. The epidemiology of HTLV-I, II in industrialized countries has been intensively investigated, and mandatory screening of blood supplies for HTLV-I/II was implemented in mid-1980s in most developed and several developing countries, yet no expanding investigation has been executed in China so far and also been considered as a non-endemic region. However, Gessain et al. reported that the current number of HTLV carriers in the highly populated China is very probably much higher. Therefore, gaining insight into the epidemiology of HTLV infections is essential for avoiding HTLV-induced risk. To introduce the history and renew the HTLV infection in China, we reviewed literatures and conducted an investigation among blood donors in 9 provinces in China. Concluded from the historical and renewed data, the HTLV screen in China can be divided into three stages.

Search for human T-lymphotropic virus type I carriers among northeastern Chinese

Human T-lymphotropic virus type I (HTLV-I) is thought to be the causative agent of adult T-cell leukemia/ lymphoma (ATL). This virus infection is endemic in southwestern Japan, parts of Africa and the Caribbean Islands. We examined sera of 1645 subjects of Liaoning province, northeastern China to detect HTLV-I carriers in an effort to reveal the migratory route taken by the early Japanese (Jomon people). As a result, all sera were found to be negative as tested by particle-agglutination (PA), immunofluorescence (IF), enzyme-linked immunoabsorbent (ELISA) and Western blotting methods. This suggests that the Jomon people, who are thought to have brought HTLV-I to the Japan archipelago tens of thousands of years ago, did not come from northeast China.

HTLV-1-associated myelopathy in China. A disease acquired overseas?

This case report documents the first patient from mainland China with an HTLV-1-associated myelopathy. The available epidemiological data suggest a low rate of HTLV1 infection in China, although the surveys are comparatively small. Possible transmission routes and the risk of encountering the disease outside endemic areas are discussed.

Prevalence of human T-cell lymphotropic virus type I infection in Singapore: a preliminary report

Human T-cell lymphotropic virus type I (HTLV-I) infection is endemic in southwestern Japan, the Caribbean basin, Colombia, Africa and in several isolated populations in Papua New Guinea, the Solomon Islands and Vanuatu. To determine the seroprevalence of HTLV-I infection in Singapore, we tested sera from 115 hospitalized patients with acute nephritis, 50 patients with suspected leptospirosis, 34 patients with non-A, non-B hepatitis, and from 28 healthy volunteers for IgG antibodies against HTLV-I using an enzyme-linked immunosorbent assay. Antibodies were detected in sera from 6 of the 199 patients and from 3 of the 28 healthy volunteers, but these positives could not be confirmed by Western immunoblotting. Our data are consistent with other reports of low seroprevalence of HTLV-I infection despite extensive Japanese contact in Korea, Taiwan, the People's Republic of China and Micronesia. Further studies on a larger sample size, however, are necessary to confirm the absence of any focus of infection in the Singapore population.

The epidemiology of HTLV-I infection

It has been 10 years since the discovery of the human T-cell lymphotropic virus type I (HTLV-I), the first human retrovirus. During the past decade, significant progress has been made in understanding the transmission of the virus and defining its geographic distribution. It has been shown conclusively that HTLV-I is a causal factor in the induction of both adult T-cell leukemia/lymphoma and HTLV-I-associated myelopathy. However, the pathogenesis of each of these conditions is not clear, and in the light of the evidence of immune dysfunction seen among carriers of the infection, it is likely that other associated diseases will be identified. The challenge in the next decade will be to develop and implement therapeutic interventions among carriers to prevent such diseases as well as to curtail transmission within endemic populations.

Geographic distribution of HTLV-I and identification of a new high-risk population

Epidemiologic studies indicate that human T-cell lymphotropic virus type I (HTLV-I), the causative agent of most cases of adult T-cell leukemia/lymphoma (ATLL) in Southeast Japan and the Caribbean islands and the probable cause of a progressive neurological disorder often referred to as tropical spastic paraparesis, occurs with unusual geographic clustering. The current large-scale serosurvey was undertaken to improve our understanding of HTLV-I prevalence in different parts of the world. We analyzed 43,445 serum samples collected from various geographic locales worldwide; 76% of these sera came from clinically healthy donors. Samples were initially screened by an enzyme-linked immunosorbent assay (ELISA) and 4,353 were further evaluated by means of competition assays. In this study, which did not include sera from endemic areas of Japan, a high prevalence of infection was observed in several countries in the Caribbean basin. A significant age-sex difference was observed between populations in the Caribbean and non-endemic regions of Japan. The reason for the male excess in non-endemic areas of Japan will require further study, while the female excess in the Caribbean basin is compatible with the previously described pattern for other HTLV-I-endemic areas. A newly recognized area of possible endemicity was southern Florida, where evidence of infection with HTLV-I or a related virus was found in a group of native Americans whose sera were collected in 1968. In certain parts of the world, particularly sub-Saharan Africa, important problems in determining specificity of reactivity occurred, probably because of cross-reacting antibodies. No pattern was detected that could explain the cross-reactivity solely on the basis of geographic areas, specific patterns of non-viral parasitic infection, or methods of handling the specimens. It is possible that these cross-reactivities are antibodies to proteins from HTLV-I-related retroviruses yet to be discovered.

A field study of infection with human T-cell leukemia virus among African primates

African non-human primates were surveyed seroepidemiologically for natural infection of human T-cell leukemia virus type I (ATLV/HTLV-I) or its closely related virus(es). Materials from three genera (Cercopithecus, Papio, and Theropithecus), four species (grivet monkey, Anubis baboon, Hamadryas baboon, and gelada), totalling 983 animals under natural conditions, were obtained in a field study in Ethiopia. Virus infection was determined by the indirect immunofluorescence test using HTLV-I specific antigens. Animals seropositive for HTLV-I were found among grivet monkeys and Anubis baboons including the hybrid offspring between Anubis and Hamadryas baboons but not pure-Hamadryas baboons and geladas. From these results, the HTLV-I family was proved to be widespread on the African continent and was regarded as a common retrovirus among catarrhines.

Sporadic cases of carriers of human T-lymphotropic virus type 1 in Southeast Asia

Sera obtained from 3,472 persons in Malaysia, Thailand, Philippines and Indonesia were tested for the presence of antibody to adult T-cell leukemia-associated antigen by the gelatin particle agglutination test and indirect immunofluorescence. Among these, only two seropositives were identified. One was a 30-year-old male Malaysian of Indian origin. The other was a 42-year-old female Thai who resided in Bangkok. These results suggested that the infection of human T-lymphotropic virus type 1 might not be endemic in these countries.

Prevalence of a human retrovirus in native Japanese: evidence for a possible ancient origin

The origin of a human retrovirus (ATLV or HTLV-I) is, at present, unknown although carriers of the virus have been found in Japan, the Caribbean basin and Africa. By means of a sero-epidemiological study, the Ainu people of Hokkaido, located in the northernmost island of Japan, were shown to have antibody to the virus in high frequency. Since the Ainu are regarded as descendants of the pre-agriculture native population of northern Japan, this finding appears to indicate that the retrovirus was already present in the aboriginal Japanese of prehistoric times.