Long-term follow-up of HTLV-1 proviral load in asymptomatic carriers and in incident cases of HAM/TSP: what is its relevance as a prognostic marker for neurologic disease?
HTLV-1 proviral load (pvl) is an important risk marker for HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), but its value as prognostic marker is not well defined. Long-term prospective cohort studies are necessary to clarify this question. Here, we analyzed HTLV-1 pvl in the peripheral blood of 82 asymptomatic carriers (AC; 351 samples), 12 HAM/TSP patients (HAM; 46 samples), and six incident cases of HAM/TSP (iHAM), with serial samples collected before (n = 10) and after (n = 20) the disease onset. The mean interval of follow-up was 10 years in the AC group and 8 years in HAM and iHAM groups. pvl was not significantly different between the first and last measurements in the three groups, but there was a trend to decrease over time. Coefficient of variation of pvl was significantly lower in the AC group than in HAM (p = 0.015) and iHAM (p = 0.022) patients. AC and HAM individuals showed a significant and strong positive correlation between the first and last measurements of pvl, but not iHAM subjects. All individuals who developed HAM/TSP during the follow-up had high pvl level (>1 %) before the onset of disease, but a typical increase in pvl was not observed in that period. The data suggest that there is a trend to reach an equilibrium plateau of pvl over time, characteristic of each individual. A significant rate of AC keeps high pvl levels for a long time without developing clinical symptoms associated to HTLV-1 infection. Thus, serial quantification of pvl in the peripheral blood does not seem to be a good prognostic marker for HAM/TSP.
Research Department, Minas Gerais State Blood Center (Fundação Hemominas), Belo Horizonte, Brazil. marina.martins@hemominas.mg.gov.br.|Interdisciplinary HTLV Research Group (GIPH), Belo Horizonte, Brazil. marina.martins@hemominas.mg.gov.br.|Serviço de Pesquisa, Fundação Centro de Hematologia e Hemoterapia de Minas Gerais, Fundação HEMOMINAS, Alameda Ezequiel Dias, 321, Bairro Santa Efigênia, Belo Horizonte, Minas Gerais, 30130-110, Brazil. marina.martins@hemominas.mg.gov.br.
Marina Lobato
ML
Martins
Institute of Biological Sciences, Federal University of Minas Gerais (UFMG), Belo Horizonte, Brazil.
Jacqueline Cronemberger
JC
Guimarães
Interdisciplinary HTLV Research Group (GIPH), Belo Horizonte, Brazil.
João Gabriel
JG
Ribas
Research Department, Minas Gerais State Blood Center (Fundação Hemominas), Belo Horizonte, Brazil.|Interdisciplinary HTLV Research Group (GIPH), Belo Horizonte, Brazil.
Luiz Cláudio Ferreira
LC
Romanelli
Research Department, Minas Gerais State Blood Center (Fundação Hemominas), Belo Horizonte, Brazil.|Interdisciplinary HTLV Research Group (GIPH), Belo Horizonte, Brazil.
Anna Bárbara
AB
de Freitas Carneiro-Proietti
D000328:Adult; D000368:Aged; D058070:Asymptomatic Diseases; D015415:Biomarkers / Q000032:analysis; D002353:Carrier State; D004279:DNA, Viral / Q000097:blood / Q000235:genetics*; D005260:Female; D006790:Host-Parasite Interactions; D015368:Human T-lymphotropic virus 1 / Q000235:genetics / Q000254:growth & development*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015493:Paraparesis, Tropical Spastic / Q000097:blood / Q000175:diagnosis* / Q000473:pathology / Q000821:virology; D011379:Prognosis; D011446:Prospective Studies; D011533:Proviruses / Q000235:genetics / Q000254:growth & development*; D019562:Viral Load / Q000235:genetics*
D015415:Biomarkers; D004279:DNA, Viral
HAM/TSP; HTLV-1; Marker; Prognosis; Progression; Proviral load
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