Exacerbated inflammatory cellular immune response characteristics of HAM/TSP is observed in a large proportion of HTLV-I asymptomatic carriers.
BACKGROUND
A small fraction of Human T cell Leukemia Virus type-1 (HTLV-I) infected subjects develop a severe form of myelopathy. It has been established that patients with HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP) show an exaggerated immune response when compared with the immunological response observed in HTLV-I asymptomatic carriers. In this study the immunological responses in HAM/TSP patients and in HTLV-I asymptomatic carriers were compared using several immunological assays to identify immunological markers associated with progression from infection to disease.


METHODS
Immunoproliferation assays, cytokine levels of unstimulated cultures, and flow cytometry analysis were used to evaluate the studied groups. Nonparametric tests (Mann-Whitney U test and Wilcoxon matched-pairs signed ranks) were used to compare the difference between the groups.


RESULTS
Although both groups showed great variability, HAM/TSP patients had higher spontaneous lymphoproliferation as well as higher IFN-gamma levels in unstimulated supernatants when compared with asymptomatic carriers. Flow cytometry studies demonstrated a high frequency of inflammatory cytokine (IFN-gamma and TNF-alpha) producing lymphocytes in HAM/TSP as compared to the asymptomatic group. This difference was accounted for mainly by an increase in CD8 cell production of these cytokines. Moreover, the HAM/TSP patients also expressed an increased frequency of CD28-/CD8+ T cells. Since forty percent of the asymptomatic carriers had spontaneous lymphoproliferation and IFN-gamma production similar to HAM/TSP patients, IFN-gamma levels were measured eight months after the first evaluation in some of these patients to observe if this was a transient or a persistent situation. No significant difference was observed between the means of IFN-gamma levels in the first and second evaluation.


CONCLUSIONS
The finding that a large proportion of HTLV-I carriers present similar immunological responses to those observed in HAM/TSP, strongly argues for further studies to evaluate these parameters as markers of HAM/TSP progression.
Santos
Silvane Braga
SB
Serviço de Imunologia, Hospital Universitário Professor Edgard Santos, Universidade Federal da Bahia, Salvador, Bahia, Brasil. silvane@ufba.br
Porto
Aurélia Fonseca
AF
Muniz
André Luiz
AL
de Jesus
Amélia Ribeiro
AR
Magalhães
Elza
E
Melo
Ailton
A
Dutra
Walderez O
WO
Gollob
Kenneth J
KJ
Carvalho
Edgar M
EM
D000328:Adult; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002353:Carrier State / Q000097:blood / Q000276:immunology*; D015481:HTLV-I Antibodies / Q000097:blood; D015490:HTLV-I Infections / Q000097:blood / Q000276:immunology*; D015368:Human T-lymphotropic virus 1; D006801:Humans; D007371:Interferon-gamma / Q000097:blood*; D008875:Middle Aged; D015493:Paraparesis, Tropical Spastic / Q000097:blood / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D015481:HTLV-I Antibodies; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma