Antibodies against p40^tax Gene Product of Human T‐Lymphotropic Virus Type‐I (HTLV‐I) under Various Conditions of HTLV‐I Infection

Abstract

We investigated antibodies against pX gene product, p40mx, by ELISA using recombinant p40tax protein in HTLV‐I seropositive carriers as well as patients with adult T cell leukemia (ATL) and HTLV‐I‐associated myelopathy (HAM). Seventy (49.0%) out of 143 HTLV‐I healthy carriers were found to be positive for antibody against p40tax antigen and the follow‐up samples at two‐year intervals revealed constant reactivity by ELISA in each carrier. The onset of antibody production was delayed 4 to 12 weeks as compared with anti‐HTLV‐I in primary infection cases. The anti‐p40tax‐positive rate (90%) in HAM patients was significantly higher than that of healthy carriers, acute and chronic ATL patients and their family members. Furthermore, HAM patients and a few healthy carriers showed high reactivities by ELISA. Children from mothers with anti‐p40tax showed a higher anti‐HTLV‐I‐positive rate than that of children from mothers without anti‐p40tax (54.5% versus 12.5%). Two men without anti‐p40tax and one female with low anti‐p40tax developed ATL during follow‐up studies. These results suggest that HTLV‐I carriers could be divided into 2 or 3 sub‐populations according to antibody response to p40tax. A smaller population with anti‐p40tax, especially a high antibody reactivity, could have a high risk of developing HAM and of transmission from mother to child. In addition, ATL may occur in a population with low or absent anti‐p40tax.

Intrafamilial transmission of HTLV-I and its association with anti-Tax antibody in an endemic population in Japan

“…This trend was similar to the results of studies in other HTLV-I endemic areas in Japan in younger subjects including children (Kamihira et al, 1989;Kashiwagi et al, 1990). The age range of the population in the Gotoh Islands was from 16 years (Kamihira et al, 1989), and that in the Yaeyama Districts was from 2 years (Kashiwagi et al, 1990). These results support the idea that the anti-Tax sero-status of the mothers is a risk factor for mother-to-child infection.…”

“…The presence of anti-Tax antibody is thought to be a risk factor for infectivity of HTLV-I (Kamihira et al, 1989;Kashiwagi et al, 1990;Chen et al, 1991). In terms of sexual transmission of HTLV-I, we have shown in the Miyazaki Cohort Study that spouses of HTLV-I seroconverters were significantly highly positive for anti-Tax antibody compared with those whose spouses were HTLV-I sero-negative Stuver et al, 1993).…”

“…It is unknown whether such an age-specific difference in significance of anti-Tax antibody occurs in other HTLV-I endemic areas. The effect of anti-Tax antibody of HTLV-I sero-positive wives on husbands' HTLV-I sero-prevalence also remains unclear.Concerning the significance of anti-Tax antibody in vertical transmission of HTLV-I, Kamihira et al (1989) reported a significantly higher HTLV-I sero-prevalence rate among individuals aged over 16 years old who had anti-Tax sero-positive HTLV-I carrier mothers than those who had anti-Tax sero-negative carrier mothers in the Gotoh Islands of Nagasaki, another HTLV-I endemic area in Japan. A similar tendency was seen in the study of the Yaeyama District of Okinawa among individuals aged over 2 years.…”

Sexual transmission of human T-cell leukemia virus type I associated with the presence of anti-Tax antibody.

“…Kamihira et al (38) used a recombinant Tax ELISA test in a retrospective cohort study to show that the rate of motherto-child transmission of HTLV-I was significantly higher in anti-Tax antibody-positive mothers than in anti-Tax antibody-negative mothers. This implies that HTLV-I Tax is also important for vertical transmission of viral infection.…”

Transmission of Human T-Cell Lymphotropic Virus Type 1 Tax to Rabbits bytax-Only-Positive Human Cells

“…As anticipated, the PBMCs of rabbits injected with virus-infected C91PL cells also had gag and env sequences. Neither the animals injected with HTLV-1-infected cells containing proviral sequences spanning the entire viral genome nor the ones injected with cells containing only tax sequences developed antibodies to p40 tax , an antibody whose development is known to be late (11). The observations suggest that the tax-only state can be transmitted by cells that harbor only this incomplete, theoretically replication-defective viral sequence, which may, however, have pathophysiologic implications.…”