Anti-Tax antibody levels in asymptomatic carriers, oligosymptomatic carriers, patients with rheumatologic disease or with HAM/TSP do not correlate with HTLV-1 proviral load.
BACKGROUND
HTLV-1 infects millions of people around the world and induces myelopathy (HAM/TSP), adult T-cell leukemia (ATL) or other inflammatory or rheumatologic diseases. The host-virus interaction causes asymptomatic carriers to develop HAM/TSP. Biomarkers are needed to predict patients who are at risk for HAM/TSP. Tax is highly immunogenic and is a major target protein recognized by cytotoxic T lymphocytes. Anti-Tax antibodies are involved in HAM/TSP pathogenesis.


OBJECTIVE
To assess anti-Tax IgG reactivity with a flow cytometry assay (FCA) using an infection/transfection system with Vaccinia virus and pLW44/Tax-expressing Tax and to correlate the anti-Tax response and the HTLV-1 proviral load.


METHODS
: We enrolled 81 individuals: 9 HTLV-1 seronegative (NP) and 72 HTLV-1 positive (23 HTLV-1 asymptomatic carriers (AC), 12 oligosymptomatic patients (OL), 7 with rheumatologic diseases (DR) and 30 with HAM/TSP (HT)). Anti-Tax reactivity was assessed by FCA, and HTLV-1 proviral load was measured with real time PCR.


RESULTS
The HT and DR groups showed greater anti-Tax IgG reactivity (p<0.001 and p<0.05 comparing HT to the OL and AC group, respectively; p<0.05 comparing DR to the OL group), and the reactivity in the DR+HT group was significantly different when compared to the AC group (p<0.05) and to the OL group (p<0.001). The proviral load was higher in the HT group compared to the OL (p<0.001) and in the HT+DR group compared to OL (p<0.001). There was no correlation between anti-Tax IgG reactivity and proviral load in any of the HTLV-1-infected groups.


CONCLUSIONS
These findings suggest that although anti-Tax IgG reactivity and the HTLV-1 proviral load are important markers of the development of HTLV-1-associated diseases, their levels are not correlated.
Laboratório de Biologia de Microrganismos Intracelulares, Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais - UFMG, Belo Horizonte, Brazil.
Jaqueline Gontijo
JG
de Souza
Flávio Guimarães
FG
da Fonseca
Marina Lobato
ML
Martins
Camila Pacheco Silveira
CP
Martins
Luciana Debortoli
LD
de Carvalho
Jordana Grazziela Alves
JG
Coelho-dos-Reis
Anna Bárbara Freitas
AB
Carneiro-Proietti
Olindo Assis
OA
Martins-Filho
Edel Figueiredo
EF
Barbosa-Stancioli
D000914:Antibodies, Viral / Q000097:blood* / Q000276:immunology; D002353:Carrier State / Q000276:immunology*; D018929:Cell Culture Techniques; D005260:Female; D016356:Gene Products, tax / Q000276:immunology*; D015490:HTLV-I Infections / Q000276:immunology* / Q000821:virology; D015368:Human T-lymphotropic virus 1 / Q000235:genetics / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology; D008297:Male; D015493:Paraparesis, Tropical Spastic / Q000276:immunology*; D011533:Proviruses / Q000276:immunology*; D019562:Viral Load
D000914:Antibodies, Viral; D016356:Gene Products, tax; D007074:Immunoglobulin G; C514970:tax protein, Human T-lymphotrophic virus 1