Tropical spastic paraparesis associated with HTLV-1 in Egypt

Phenotypic and genotypic comparisons of human T-cell leukemia virus type 1 reverse transcriptases from infected T-cell lines and patient samples

It is well established that cell-free infection with human T-cell leukemia virus type 1 (HTLV-1) is less efficient than that with other retroviruses, though the specific infectivities of only a limited number of HTLV-1 isolates have been quantified. Earlier work indicated that a post-entry step in the infectious cycle accounted for the poor cell-free infectivity of HTLV-1. To determine whether variations in the pol gene sequence correlated with virus infectivity, we sequenced and phenotypically tested pol genes from a variety of HTLV-1 isolates derived from primary sources, transformed cell lines, and molecular clones. The pol genes and deduced amino acid sequences from 23 proviruses were sequenced and compared with 14 previously published sequences, revealing a limited number of amino acid variations among isolates. The variations appeared to be randomly dispersed among primary isolates and proviruses from cell lines and molecular clones. In addition, there was no correlation between reverse transcriptase sequence and the disease phenotype of the original source of the virus isolate. HTLV-1 pol gene fragments encoding reverse transcriptase were amplified from a variety of isolates and were subcloned into HTLV-1 vectors for both single-cycle infection and spreading-infection assays. Vectors carrying pol genes that matched the consensus sequence had the highest titers, and those with the largest number of variations from the consensus had the lowest titers. The molecular clone from CS-1 cells had four amino acid differences from the consensus sequence and yielded infectious titers that were approximately eight times lower than those of vectors encoding a consensus reverse transcriptase.

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.

Characterization of human T-lymphotropic virus type I- and II-infected T-cell lines: antigenic, phenotypic, and genotypic analysis

Eighteen long-term T-cell lines were established from peripheral blood mononuclear cells of individuals infected with human T-lymphotropic virus type I (HTLV-I) or II (HTLV-II). These cell lines (10 HTLV-I and 8 HTLV-II), representing diverse pathologic profiles and geographic regions, have been in culture for over 6 months and have constitutively produced p24gag antigen. Antigenic characterization of the cell lines by Western blot analysis demonstrated that all but one produced gag (p24) and env (gp46 or gp52) structural proteins; one HTLV-I-infected cell line exhibited an aberrant protein profile. Phenotypic analysis of the HTLV-infected cell lines demonstrated phenotypes consistent with activated T-cells (CD5+, CD25+, HLA-DR+). The HTLV-I-infected cell lines were predominantly CD4+ (IR, FS, A212, SP, 1657, 1742, 3669, 1996, and 3614), whereas EG was CD8+. The HTLV-II-infected cell lines were either CD4+ (H2A, Y17, G12.1), CD8+ (H1H, H2E, Y03, Y06), or both (H1B). Restriction map analysis and subtyping of the viral genomes demonstrated heterogeneity among these isolates. Of the HTLV-I-infected cell lines, six were subtype II, one was subtype III and, on the basis of additional restriction sites, another subtype, tentatively classified as subtype IV, could be identified for three of the HTLV-I-infected cell lines. Of the HTLV-II-infected cell lines, six were subtype HTLV-IIa and two were subtype HTLV-IIb. While the majority of the cell lines resemble the prototypic HTLV-I-infected (MT-2) and HTLV-II-infected (MoT) cell lines, the antigenic, phenotypic, and genotypic data collectively demonstrate heterogeneity among viral isolates representing diverse geographic regions.

The epidemiology of myelopathy associated with human T-lymphotropic virus 1

A progressive spastic myelopathy is one of the principal manifestations of the human T cell lymphotropic virus type 1. Recent research is reviewed on the geography and epidemiology of this specific form of tropical spastic paraparesis. First recognized in the Caribbean, Colombia and Japan, it is now also confirmed as a major neurological problem in areas of eastern Brazil, western equatorial Africa, Natal and Seychelles, with other scattered foci world-wide. Accurate surveys call for sophisticated techniques including polymerase chain reaction amplification. The only defined modes of spread are by breast feeding, sexual contact and blood cell infusion. The onset of neurological disease is associated with high antibody titres and a high rate of spontaneous T lymphocyte proliferation. Molecular analysis has revealed no nucleotide sequence variation in cases with or without myelopathy. In non-transfusion cases the clinical attack rate is low with a very long latent period, but there are unexplained regional differences and familial cases are an important exception. Current research is focused on possible local, ethnic, or genetic co-factors.