Transient mobilization of human immunodeficiency virus (HIV)-specific CD4 T-helper cells fails to control virus rebounds during intermittent antiretroviral therapy in chronic HIV type 1 infection

Abstract

Immune control of human immunodeficiency virus (HIV) is not restored by highly active antiretroviral therapies (HAART) during chronic infection. We examined the capacity of repeated structured therapeutic interruptions (STI) to restore HIV-specific CD4 and CD8 T-cell responses that controlled virus production. Eleven STI (median duration, 7 days; ranges, 4 to 24 days) were performed in three chronically HIV-infected patients with CD4 counts above 400/mm(3) and less than 200 HIV RNA copies/ml after 18 to 21 months of HAART; treatment resumed after 1 week or when virus became detectable. HIV-specific T-cell responses were analyzed by proliferation, gamma interferon (IFN-gamma) production, and enzyme-linked immunospot assays. Seven virus rebounds were observed (median, 4,712 HIV-1 RNA copies/ml) with a median of 7 days during which CD4 and CD8 counts did not significantly change. After treatment resumed, the viral load returned below 200 copies/ml within 3 weeks. Significant CD4 T-cell proliferation and IFN-gamma production against HIV p24 appeared simultaneously with or even before the virus rebounds in all patients. These CD4 responses lasted for less than 3 weeks and disappeared before therapeutic control of the virus had occurred. Increases in the numbers of HIV-specific CD8 T cells were delayed compared to changes in HIV-specific CD4 T-cell responses. No delay or increase in virus doubling time was observed after repeated STI. Iterative reexposure to HIV during short STI in chronically infected patients only transiently mobilized HIV-specific CD4 T1-helper cells, which might be rapidly altered by virus replication. Such kinetics might explain the failure at delaying subsequent virus rebounds and raises concerns about strategies based on STI to restore durable HIV-specific T-cell responses in chronic HIV infection.

Figures

FIG. 1

Patient 1. (A) Effect of intermittent interruptions of antiretroviral therapy on viral load and CD4 or CD8 counts. The HIV-1 RNA level was measured by RT-PCR with a limit of sensitivity of 20 copies per ml. Viral loads are expressed as numbers of HIV-1 RNA copies per milliliter of plasma; CD4 and CD8 counts were analyzed by flow cytometry with fluorescent beads as an internal standard. The values (mean ± standard deviation) in healthy people are as follows: CD4+ cells, 858 ± 260 cells/μl of plasma; CD8+ cells, 482 ± 164/μl plasma. White areas at top of the figure indicate periods of treatment (nevirapine, stavudine, and lamivudine); interruptions are in grey and are also shown in panels A to D. (B) Effect of intermittent interruptions of antiretroviral therapy on Ki67 antigen expression. Ki67 antigen expression was analyzed in CD4+ and CD8+ T cells by flow cytometry after intracellular staining. The values in healthy people are 2.5% ± 0.6% for CD4+ Ki67+ cells and 2% ± 0.6% for CD8+ Ki67+ cells. (C) Effect of intermittent interruptions of antiretroviral therapy on T-helper cell responses to HIV-1 p24 protein. HIV-1 p24-stimulated IFN-γ production by CD8-depleted PBMC was measured by enzyme-linked immunosorbent assay in the 2-day culture supernatants and is expressed as 10−1 picograms per milliliter; T cell proliferative responses against HIV-1 (p24) were measured on CD8-depleted PBMC, and the results are expressed as a stimulation index. (D) Effect of intermittent interruptions of antiretroviral therapy on CD8+ cell responses to HIV-1 protein. The frequency of HIV-specific CD8+ T cells was tested by a recombinant vaccinia virus ELISPOT assay. PBMC were infected with wild-type vaccinia virus or recombinant vaccinia virus Gag, Pol, Env, or Nef, and IFN-γ-producing SFC were enumerated in an 18-h ELISPOT assay. Results are expressed as the number of IFN-γ SFC per 106 PBMC.

FIG. 2

Patient 2. (A) Effect of intermittent interruptions of antiretroviral therapy on viral load and CD4 or CD8 counts. (B) Effect of intermittent interruptions of antiretroviral therapy on Ki67 antigen expression. (C) Effect of ST1 of therapy on the T-helper cell responses to HIV-1 p24 protein. (D) Effect of ST1 of therapy on the CD8+ cell responses to HIV-1 protein. For further details for all panels, see the legend to Fig. 1.

FIG. 3

Patient 3. (A) Effect of intermittent interruptions of antiretroviral therapy on viral load and CD4 or CD8 counts. (B) Effect of intermittent interruptions of antiretroviral therapy on Ki67 antigen expression. (C) Effect of ST1 of therapy on the T-helper cell responses to HIV-1 p24 protein. (D) Effect of intermittent interruptions of antiretroviral therapy on the CD8+ cell responses to HIV-1 protein. The frequency of HIV-specific CD8+ T cells was tested by an ELISPOT assay using a panel of peptides according to the HLA of the patient. Results are expressed as the number IFN-γ SFC per 106 PBMC. For further details for all panels, see the legend to Fig. 1.