Objectives: Despite limiting exposure to antiretroviral drugs, structured treatment interruptions can influence multiple aspects of T-cell immunity, particularly those regarding CD4(+) T lymphocytes. We evaluated the impact of CD4-guided treatment interruption (CD4-GTI) and treatment resumption on regulatory T cells (Tregs), T-lymphocyte activation, differentiation and polyfunctional gag-specific response.
Methods: Patients were analyzed just prior to treatment interruption, at 2 and 6 months after treatment interruption, just prior to treatment resumption and at 2 and 6 months after treatment resumption. Thawed peripheral blood mononuclear cells were stained immediately for phenotype analysis or stimulated with HIV-gag peptides and analyzed by polychromatic flow cytometry.
Results: Treatment interruption resulted in a CD4(+) cell count decrease and plasma viral load (pVL) increase, but did not preclude a good immune reconstitution and a complete suppression of pVL after treatment resumption. Treatment interruption did not influence CD4(+) T-cell differentiation and Treg subsets. During treatment interruption, gag-specific CD4(+) T cells were not lost, although the frequency of HIV-specific CD8(+) cells increased. Most gag-specific CD4(+) T cells were potentially cytotoxic (CD107a(+)) and were not influenced by pVL or by HAART. Most helper (CD154(+)) gag-specific CD4(+) T lymphocytes did not produce interferon-γ or interleukin-2.
Conclusion: CD4-GTI did not cause depletion of memory cells, Tregs or HIV-specific CD4(+) cells and, on the contrary, could induce HIV-specific responses. If guided by CD4(+) T-cell count, treatment interruption does not provoke irreversible immune damages.