T cell receptor γδ repertoire in HIV‐1‐infected individuals

Abstract

While Vγ9Vδ2 cells dominate among peripheral blood γδ T cells in healthy adults, the majority of γδ T cells in most HIV-1-infected individuals express Vδ1. We asked whether these elevated levels of Vδ1 T cells were due to clonal expansion. Three-color flow cytometry with monoclonal antibodies against Vγ2/Vγ3/Vγ4, Vγ4 and Vγ9 was used to investigate Vγ usage in 27 patients with elevated numbers of Vδ1 T cells. While the relative proportion of Vγ9 cells among γδ T cells was significantly reduced in HIV-1⁺ inviduals (10 ± 11% vs. 80 ± 17%, p < 0.001), the fraction of γδ T cells using Vγ5 or Vγ8 was significantly increased (54 ± 15% vs. 7 ± 11%, p < 0.001). In 1 patient, 76% of the Vδ1 cells expressed Vγ2 or Vγ3, suggesting clonality of the Vδ1 population. In line with this assumption, analysis of the Vδ1-Jδ junctional regions by reverse transcription-polymerase chain reaction (RT-PCR) resulted in products of only one junctional length, as demonstrated by electrophoresis on denaturing gels, and 12 out of 16 (75%) in-frame junctional sequences were identical in this patient. In other HIV-1⁺ patients, RT-PCR resulted in products of several distinct sizes, also indicating a highly restricted repertoire. After sequencing the Vδ1-Jδ junctional regions of 3 additional patients, we found repeated but patient-specific in-frame junctions accounting for 10–30% of the sequenced clones. However, limited Vδ1-Jδ junctional diversity was also seen in healthy donors. RT-PCR products from 10 healthy individuals resulted in distinct bands on denaturing gels. In 1 of them exhibiting a single prominent band, 10 out of 17 (58%) sequenced junctions were identical. Two other healthy donors displayed 2/14 and 5/18 identical junctional sequences, respectively. Taken together, our results reveal significant alterations of Vγ usage in HIV-1⁺ patients, while the Vδ1 junctional repertoire is similarly restricted in HIV-1⁺ and HIV-1⁻ individuals. Therefore, these data argue against an obligatory clonal expansion of Vδ1-expressing cells during HIV-1 infection.