Proviral loads and clonal expansion of HTLV-1-infected cells following vertical transmission: a 10-year follow-up of children in Jamaica

Abstract

Objective: Few studies have specifically examined proviral load (PVL) and clonal evolution of human T-lymphotropic virus type 1 (HTLV-1)-infected cells in vertically infected children.

Methods: Sequential samples (from ages 1 to 16 years) from 3 HTLV-1-infected children (cases A, B and C) in the Jamaica Mother Infant Cohort Study were analyzed for their PVL and clonal expansion of HTLV-1-infected cells in peripheral blood mononuclear cells (PBMCs) by inverse-long PCR.

Results: The baseline PVL (per 100,000 PBMCs) of case A was 260 (at 1 year of age) and of case B it was 1,867 (at 3 years of age), and they remained constant for more than 10 years. Stochastic patterns of clonal expansion of HTLV-1-infected cells were predominately detected. In contrast, case C, who had lymphadenopathy, seborrheic dermatitis and hyperreflexia, showed an increase in PVL from 2,819 at 1.9 years to 13,358 at 13 years of age, and expansion of 2 dominant clones.

Conclusion: The clonal expansion of HTLV-1-infected cells is induced in early childhood after infection acquired from their mothers. Youths with high PVL and any signs and symptoms associated with HTLV-1 infection should be closely monitored.

Fig. 1

Sequential change of the HTLV-1 proviral loads in the genomic DNA derived from 100,000 PBMCs of 3 carrier children.

Fig. 2

Inverse long PCR analysis of HTLV- 1-infected cells from carrier children. Triplicate analysis of PBMCs was performed in each experiment. MWM 1 = Low-molecular-weight DNA marker; MWM 2 = high-molecular-weight DNA marker; N = PBMCs from HTLV-1-negative subject as negative control; P = HTLV- 1-infected cell line, HUT102, as positive control. a Analysis of case A at ages 1, 4.5 and 12.8 years. b Analysis of case B at ages 3, 5.6 and 13.1 years. Arrows indicate the bands detected in all triplicate analyses. c Analysis of case C at ages 1.9, 5, 13 and 16 years. Arrows indicate 2 distinct bands (clone S and L) detected in all triplicate analyses. Arrowheads indicate the week but consistently detected bands in all triplicate analyses.

Fig. 2

Inverse long PCR analysis of HTLV- 1-infected cells from carrier children. Triplicate analysis of PBMCs was performed in each experiment. MWM 1 = Low-molecular-weight DNA marker; MWM 2 = high-molecular-weight DNA marker; N = PBMCs from HTLV-1-negative subject as negative control; P = HTLV- 1-infected cell line, HUT102, as positive control. a Analysis of case A at ages 1, 4.5 and 12.8 years. b Analysis of case B at ages 3, 5.6 and 13.1 years. Arrows indicate the bands detected in all triplicate analyses. c Analysis of case C at ages 1.9, 5, 13 and 16 years. Arrows indicate 2 distinct bands (clone S and L) detected in all triplicate analyses. Arrowheads indicate the week but consistently detected bands in all triplicate analyses.

Fig. 2

Inverse long PCR analysis of HTLV- 1-infected cells from carrier children. Triplicate analysis of PBMCs was performed in each experiment. MWM 1 = Low-molecular-weight DNA marker; MWM 2 = high-molecular-weight DNA marker; N = PBMCs from HTLV-1-negative subject as negative control; P = HTLV- 1-infected cell line, HUT102, as positive control. a Analysis of case A at ages 1, 4.5 and 12.8 years. b Analysis of case B at ages 3, 5.6 and 13.1 years. Arrows indicate the bands detected in all triplicate analyses. c Analysis of case C at ages 1.9, 5, 13 and 16 years. Arrows indicate 2 distinct bands (clone S and L) detected in all triplicate analyses. Arrowheads indicate the week but consistently detected bands in all triplicate analyses.

Fig. 3

Sequential change of the copy numbers of clones S and L in case C in 100,000 PBMCs at ages 1.9, 5, 13 and 16 years. Clonespecific quantitative real-time PCR was performed.

Fig. 4

Polymerase chain reaction analysis of the rearrangements of TCR γ gene in case C at age 16 years. N = PBMCs from a healthy volunteer not infected with HTLV-1 and who is not involved in this cohort, as a negative control; HC = PBMCs from an HTLV-1 carrier, who is not involved in this cohort, as an HTLV-1-positive control; P = a patient with adult T cell leukemia, who is not involved in this cohort, showing a sharp and dominant band, as positive control; case C = PBMCs from case C at age 16 years old, who showed a weak, but evident band in a smear background (arrow).

Fig. 5

Distribution of 128 subclones of the polymerase chain reaction (PCR) products of TCR γ gene in case C at age 16 years based on their variation in lengths. Each open circle indicates a unique PCR product, showing the diversity in the length and the DNA sequence. The 5 groups of PCR products indicated by the closed square, triangle, circle, diamond, and double circle indicate the clones detected repeatedly and showed identical DNA sequences.