The HTLV-1 proviral load was measured in the peripheral blood of HTLV-1-infected patients with RA or connective tissue disease and in matched asymptomatic and HAM/TSP controls (Figure ). The number of copies of HTLV-1 proviral DNA per 106 PBMCs ranged from 14,600 to 373,000 in the patients with RA (Table ) and from 1,500 to 411,200 in patients with connective tissue disease (Table ), the corresponding ranges in the HTLV-1 asymptomatic carriers and in patients with HAM/TSP being 50 to 97,700 and 2,100 to 392,000, respectively. The mean ± SD and median proviral loads were 133,800 ± 134,600 and 75,800 in the HTLV-1-infected patients with RA or connective tissue disease combined, the values for the RA subgroup being 114,400 ± 112,200 and 67,400 and those for the connective tissue disease subgroup 172,500 ± 176,700 and 120,800, while the corresponding values in the asymptomatic carriers were 18,800 ± 26,400 and 10,100 and those in patients with HAM/TSP 86,800 ± 90,600 and 62,400. The HTLV-1 proviral load was significantly higher in the HTLV-1-infected group with RA or connective tissue disease than in the matched asymptomatic HTLV-1 carriers (P = 0.0012 in Wilcoxon's test, P = 0.0002 in the paired t-test after log-transformation), and the difference remained significant when the analysis focused on the RA subgroup (P = 0.0022 in Wilcoxon's test, P = 0.0002 in the paired t-test). No differences were observed between the HTLV-1-infected group with RA or connective tissue disease and the matched HAM/TSP controls (P > 0.05 in both Wilcoxon's test and the paired t-test). As expected, the difference between the asymptomatic carriers and the HAM/TSP group was significant (P = 0.0001 in Wilcoxon's test, P < 0.0001 in the paired t-test).
| Table 1Clinical and biological features of HTLV-1-infected patients with RA |
| Table 2Clinical and biological features of HTLV-1-infected patients with connective tissue disease |
Of the 12 HTLV-1-infected patients with RA, 4 (patients 2, 9, 10, and 12) had HAM/TSP (Table ); their respective HTLV-1 proviral loads were 39,800, 247,400, 106,500, and 14,600 copies per 106 PBMCs. Two patients with connective tissue disease (Table , patients 16 and 18) had HAM/TSP, which was associated with alveolitis in patient 18, with proviral loads of 71,600 and 362,300. These samples did not account for the higher proviral load in the arthritic group compared to the asymptomatic carrier group. Indeed, after excluding the patients with co-existing HAM/TSP, the difference between the asymptomatic controls and the group with RA or connective tissue disease remained significant (P = 0.0121, Wilcoxon's test; P = 0.0027, paired t-test), even when the analysis was restricted to the subgroup with RA alone (P = 0.0117, Wilcoxon's test; P = 0.0003, paired t-test). The patient with connective tissue disease and uveitis (patient 13) had 18,420 copies per 106 PBMCs. For one of the patients with RA and HAM/TSP (patient 10), 4 consecutive frozen dry pellets of PBMCs from 1996 to 2002 were available; in these, the proviral load was relatively stable at 92,100, 73,600, 143,300, and 106,500 copies per 106 cells, respectively.
No correlation was found between HTLV-1 proviral load and the age of the patient, the duration of illness, or the Ritchie's index score (P > 0.05, Spearman test). HTLV-1 proviral load did not correlate with erythrocyte sedimentation rate or C-reactive protein level (P > 0.05, Spearman test). No significant difference in HTLV-1 proviral load was seen in patients positive or negative for rheumatoid factor or antinuclear antibody (P > 0.05, Mann-Whitney test) or receiving or not receiving either specific treatments for RA or corticotherapy (P > 0.05, Mann-Whitney test).
The proviral load was measured in two sets of PBMCs and synovial fluid or synovial tissue cells obtained from one HTLV-1-infected patient with RA at an interval of one year (Table , patient 5). In the first set of samples, the HTLV-1 proviral load in the synovial fluid cells and paired PBMCs was 845,200 and 125,300 copies per 106 cells, respectively, while, in the second set of samples from a year later, the proviral load in the synovial tissue cells and paired PBMCs was 666,700 and 38,500 per 106 cells, respectively.
Lymphocytes subsets and activation status were examined in the peripheral blood of HTLV-1-infected patients with RA or connective tissue disease. When correlations were examined between HTLV-1 proviral load and the percentage of T lymphocytes expressing CD45RO, CD45RA, or HLA-DR in the HTLV-1 infected patients with RA or connective tissue disease (Figure ), HTLV-1 proviral load correlated positively with the percentage of CD4+ T cells expressing CD45RO and negatively with that of CD4+ T cells expressing CD45RA (P = 0.039 and P = 0.021, Spearman test). A positive correlation was found between HTLV-1 proviral load and the percentage of CD4+ T cells expressing HLA-DR (P = 0.008), while the correlation did not reach significance for CD8+ HLA-DR T cells.
Lymphocyte distribution and activation were compared in the peripheral blood and synovial fluid of one HTLV-1-infected patient with RA (patient 5). The percentage of CD4+ T cells expressing CD45RO was dramatically increased in the synovial fluid (98%) compared to the peripheral blood (48%), as was the percentage of CD4+ T lymphocytes expressing HLA-DR (94% compared to 18%).