Masanori Hayami

Molecular phylogeny of human T-cell leukemia virus type I and II of amerindians in Colombia and Chile

Six human T-cell leukemia virus type I (HTLV-I) and eight human T-cell leukemia virus type II (HTLV-II) cases newly isolated from the South American countries of Colombia and Chile were analyzed together with the two Amerindian HTLV-I isolates previously reported. All of the HTLV-I isolates belonged to the transcontinental subgroup of the “cosmopolitan” group, and Colombian isolates, including those from native Amerindians and Negroes, formed a single tight cluster within this subgroup. The transcontinental subgroup consisted of isolates from various regions such as the Caribbean basin, India, Iran, South Africa, Sakhalin, and Japan, and included isolates from the “Ainu” and “Okinawa” people, regarded as relatively pure Japanese descended from the prehistoric “Jomon” period which began more than 10,000 years ago. This implied a dissemination of the subgroup associated with the movement of human beings in ancient times. On the other hand, all of the HTLV-II isolates from native Amerindians in Colombia and Chile belonged to the HTLV-IIb subtype which has previously been reported to be mainly endemic in certain populations of native Amerindians. The southernmost isolate from Chile, showing wide distribution of the llb subtype in native South Amerindians and largest heterogeneity of the subtype in Colombian isolates, supported the idea that the HTLV-IIb subtype has been endemic for a long time in native Indians of South America.

Molecular epidemiology of HTLV-I in the world.

The geographic distribution of human T-cell lymphotropic/leukemia virus type I (HTLV-I) was initially believed to be limited to southwestern Japan, the Caribbean basin, and Africa. However, extensive searches in recent years have discovered its existence in other areas of the world as well as in isolated, ethnic populations such as South Amerindians, Australo-Melanesian aborigines, religiously segregated Jews, and Pygmies. Previous genetic analyses indicated that HTLV-I can be phylogenetically classified into three major lineages: Melanesian, Central African, and Cosmopolitan groups. Recently, more detailed characterization using long terminal repeat sequences (the most variable genomic region) has revealed that the Cosmopolitan group consists of four subtypes: (A) Transcontinental, (B) Japanese, (C) West African, and (D) North African. Most HTLV-I isolates of the same ethnic group from distant locations and those from different groups inhabiting the same area showed phylogenetic similarities. These observations indicate the present distribution of this virus should be interpreted from the anthropological backgrounds of the virus-possessing populations as well as spatial contact among them. Thus, the molecular epidemiology of HTLV-I and its simian counterpart, STLV-I, provides us with important clues for understanding not only the origin and dissemination of this retrovirus but past human movements over the globe.

Prevalence and Phylogenetic Analysis of HTLV–I Isolates in Cameroon, Including Those of the Baka Pygmy

Our previous analysis of an HTLV–I isolate (CMR229) from a Cameroonian Pygmy demonstrated that the isolate is distinct from typical HTLV–ls of the “Central African group,” which has a close similarity to HTLV–I–related simian viruses (STLV–I) in Africa. In this study, we analyzed six new HTLV–ls from Cameroon consisting of three isolates from the Pygmy and three from the Bantu to examine further the genetic features of HTLV–I in Cameroon, especially in the Pygmy. A phylogenetic tree based on the long terminal repeats (LTR) region showed that all the new HTLV–ls belong to the Central African group. On the other hand, an env–based analysis of CMR229 confirmed the previous finding derived from LTR–based analysis that CMR229 has a similarity to African STLV–Is, but is distinct from the typical Central African group of HTLV–I. This suggests that multiple interspecies transmissions from non–human primates to humans have occurred in Central Africa, resulting in the presence of two distinct HTLV–I strains in this area. In addition, it seems likely that the Pygmy harbors the heterogeneous HTLV–I strains from which the main HTLV–I population spread into the Bantu.

Isolation of STLV-I from orangutan, a great ape species in Southeast Asia, and its relation to other HTLV-Is/STLV-Is

To study the evolutionary origin of human T–lymphotropic virus type I/simian T–lymphotropic virus type I (HTLV–I/STLV–I), we isolated and characterized STLV–I from orangutans (Pongo pygmaeus). Plasma samples from 3 out of 41 animals examined were reactive by particle agglutination and immunofluorescence, and one of these three was confirmed to be anti–HTLV–I antibody–positive by western blotting (WB). Cultured peripheral blood mononuclear cells from the WB–positive orangutan were reactive to anti–STLV–I–positive rhesus monkey plasma. The proviral long terminal repeat region was amplified by polymerase chain reaction and sequenced. A phylogenetic analysis indicated that orangutan STLV–I is related to the Melanesian group of HTLV–Is and other Asian STLV–Is, but the degree of divergence is considerable.