Do T cells cause HTLV-1-associated disease?: a taxing problem.
Explore the source record for details and available documents.
Carrier State↗
Biomedical subjects
S Daenke
Publications and source records attributed to S Daenke.
The transactivator gene of human T-cell leukemia virus type I is more variable within and between healthy carriers than patients with tropical spastic paraparesis.
Human T-cell leukemia virus type I (HTLV-1) causes T-cell leukemia and tropical spastic paraparesis (TSP) in a minority of infected people, whereas the majority remain healthy. No association between a particular HTLV-I sequence and disease manifestation has been found in previous studies. We studied here the sequence variability of the gene for the HTLV-I Tax protein, which is the dominant target antigen of the very strong cytotoxic T-lymphocyte response to the virus. In HTLV-I infection, the intraisolate nucleotide variability is much greater than the variability between isolates. The predicted protein sequence of Tax was significantly more variable in the healthy seropositive individuals' provirus than in those of the patients with TSP. Thus, tax sequence heterogeneity, rather than the presence of particular sequences, distinguishes healthy HTLV-I-seropositive individuals from patients with TSP.
Base Sequence↗
Activated, HTLV-1-specific cytotoxic T-lymphocytes are found in healthy seropositives as well as in patients with tropical spastic paraparesis.
In human T cell lymphoma/leukemia virus (HTLV-1)-infected people with tropical spastic paraparesis (TSP), there are activated HTLV-1-specific cytotoxic T lymphocytes (CTL) in the circulation and lymphocytic infiltrates in spinal cord lesions that are rich in CD8+ T cells. These observations suggest a role for virus-specific CTL in the pathogenesis of TSP. We have examined the anti-HTLV-1 cytotoxic activity of freshly isolated CD8+ T cells from peripheral blood lymphocytes of eight subjects seropositive for HTLV-1. Four of five subjects with TSP had circulating activated anti-Tax CTL. However, two of three seropositive subjects without TSP also had activated anti-Tax CTL. These observations show that such activated CTL are not confined to patients with TSP and raise some uncertainty about their significance in the pathogenesis of the disease. In cultures of CD8+ T cells from two TSP subjects, we detected CTL with other HTLV-1 specificities, without exogenous antigenic stimulation. A CTL epitope in the middle region of Tax and one in the C terminus of Pol have been mapped at the peptide level and the HLA Class 1 molecules restricting their recognition have been defined.
Amino Acid Sequence↗
Sequence variants of human T-cell lymphotropic virus type I from patients with tropical spastic paraparesis and adult T-cell leukemia do not distinguish neurological from leukemic isolates.
We have amplified and sequenced DNA in the envelope (env) and long terminal repeat (LTR) regions of human T-cell lymphotropic virus type I (HTLV-I) proviruses from the peripheral blood of 10 HTLV-I-seropositive patients with tropical spastic paraparesis (TSP) and two patients with adult T-cell leukemia. The aim was to examine variation in these regions and to test the hypothesis that the sequences of leukemogenic HTLV-I isolates differ from those causing the neurological disease TSP. In 5 of the 12 HTLV-I-seropositive patients, more than one HTLV-I sequence variant was identified in the same individual. No two individuals shared identical sequences in either env or LTR U3. Sequence variations were found at 73 positions in 1,416 bases amplified in env. Sequence variability was found throughout the LTR-U3 region, including the sequences of two transcriptional enhancers. Several nucleotide changes common to both Caribbean and Japanese HTLV-I isolates allowed us to identify a consensus sequence that differs from the HTLV-I prototype sequence (M. Seiki, S. Hattori, Y. Hirayama, and M. Yoshida, Proc. Natl. Acad. Sci. USA 80:3618-3622, 1983). No sequence in the env or LTR U3 region was found to be characteristic of isolates from TSP patients. Although each isolate was distinct at the nucleotide level, the predicted protein sequence of HTLV-I env is less variable than that of human immunodeficiency virus env, suggesting that these lymphotropic retroviruses use different strategies to evade host immune responses.
Adult↗
Enzymatic amplification of exogenous and endogenous retroviral sequences from DNA of patients with tropical spastic paraparesis.
Using oligonucleotide primers that hybridize to conserved sequences in the reverse transcriptase (RT) gene, we have amplified by the polymerase chain reaction three sequence variants of HTLV-I from the genomic DNA of five patients with tropical spastic paraparesis (TSP), and a fourth sequence variant from a healthy carrier of HTLV-I. These results unequivocally identify the retrovirus associated with TSP as HTLV-I and suggest that no sequence variant is uniquely responsible for the condition. The same primers served to amplify two novel single-copy endogenous retroviral RT sequences related to the exogenous mammalian leukaemia viruses: and three KpnI (LINE1) family DNA repeats. This strategy, combining the sensitivity of PCR with cross-reactive primers, may be useful in the search for known or novel retroviruses in other diseases of possible retroviral aetiology.
Amino Acid Sequence↗
B-cells purified using azide give different responses in vitro to B-cells purified without azide.
Some established techniques for B-cell enrichment include azide in the media. Here, B-cells were enriched using a technique which transiently exposed the cells of 15 mM sodium azide. After 3-4 days in culture, the precursor frequency of autoantibody-secreting cells in this population was 0.113%. In contrast, when B-cells were enriched using a technique which eliminated their exposure to sodium azide, the number of autoantibody-secreting precursor cells detected in cultures was increased up to 20-fold. Therefore, it is concluded that transient exposure to azide affects functional activities of B-cells in vitro.
Animals↗
T cells or their products are required for the differentiation of precursor B cells into antibody-secreting cells specific for a supposed T-independent self-antigen.
From our experiments and those of others in which cells were cultured at a density of 100,000 cells per well, it has been suggested that autoantibody production against mouse bromelain-treated erythrocytes (mouse brom-RBC) was independent of T cells, and further, was enhanced by the removal of T cells from responsive cell populations. Here it is shown in limiting dilution cultures that the autoimmune response is highly dependent on T cells or their products. B cells purified from the peritoneal cavities of untreated mice did not differentiate in vitro into autoantibody-secreting cells unless provided with signals from at least one of two types of accessory cells. These were plastic adherent cells and T cells, derived either from the peritoneal cavity or from established cell lines. Here it is shown that peritoneal T cells or T cells from the LBRM-33 cell line stimulated the differentiation of purified B cells in vitro in the absence of added mitogens. The accessory cell effect could be transferred in supernatants derived from T-cell cultures but not filler-cell cultures. Recombinant interleukin-2 (rIL-2) added to culture medium did not stimulate B cells directly, but could increase precursor frequencies when added to unfractionated peritoneal cell cultures, or B-cell cultures to which cells from a T-cell line had been added. From these results, it is concluded that the differentiation of precommitted peritoneal B cells in vitro into autoantibody secretors is at least partially dependent on T cells or lymphokines derived from them. Therefore, any proposed mechanisms for regulation of this autoimmune response should encompass the requirement for T cells or their products in the final differentiation stages to autoantibody secretion.
Animals↗
Dependency of B cells on the presence of adherent cells, or factors derived from them, for the production of autoantibodies in vitro in the absence of cell division.
Peritoneal cells from untreated mice secrete autoantibodies after 3-4 days of in vitro culture, although the cells do not divide. Here, peritoneal cells enriched for B cells to contain 95% surface Ig-bearing cells, did not secrete autoantibodies after 3 days of in vitro culture unless plastic-adherent cells derived from the peritoneal cavity were cultured with the B cells. Cell-free media, taken from peritoneal adherent cells that had been cultured for 3 days in vitro, when added a final concentration of 50% in fresh culture medium to purified B cells, substituted for the presence of accessory cells. In contrast to cultures of unfractionated peritoneal cells, little increase in precursor frequency was detected when enriched B cells were cultured in the presence of LPS/DXS. However, the addition of adherent cells, supernatants derived from adherent cells, or cytokines produced by a T-cell hybrid EL4, resulted in an increased precursor frequency when LPS/DXS was added to the culture medium. Three macrophage cell lines, P388-D1, J774, and PU-5-IR, when added to purified B cells. augmented the autoantibody precursor frequency detected in vitro. This is strong evidence that potentially autoreactive B cells require one or more types of accessory cells in order to differentiate into autoantibody secretors during culture in vitro. Further, the results provide indirect evidence that interleukin 1 may be a crucial molecule in the differentiation of B cells.
Animals↗
Peritoneal B cells differentiate without proliferation into autoantibody secretors under the influence of factors released by other cells.
After 3-5 days of in vitro culture, peritoneal cells from untreated C3H mice produce autoantibodies specific for autoantigens in the membranes of mouse erythrocytes. The autoantigens are exposed in vitro by treating mouse erythrocytes with the proteolytic enzyme bromelain. Limiting-dilution cell culture techniques were used to determine the frequency of the autoreactive B cells. Cells were cultured in Terasaki trays at 10-200 cells/well. Autoantibody production was assayed with an in situ plaque-forming cell (PFC) assay. On average, one autoantibody precursor cell was detected for every 150-200 peritoneal cells cultured. This precursor frequency was increased to 1 in 50 by the addition of lipopolysaccharide (LPS) and dextran sulphate (DS) to the culture medium. The addition of a culture supernatant from an EL4 lymphoma subline also induced a high proportion of the peritoneal cells to secrete autoantibodies. However, it was not possible to determine the frequency of PFC accurately because at limiting numbers of peritoneal cells the effects of EL4 affected more than one limiting variable. Significant cell division was observed in cultures to which LPS/DS had been added, in contrast to untreated cultures to which EL4 supernatant was added. The results show that high numbers of autoreactive B cells committed to self antigens are present in the peritoneal cavity and that these cells under the influence of appropriate cytokines can differentiate in vitro, even without proliferation, into autoantibody secretors. The cell type or types releasing the cytokines remain to be identified.
Animals↗