Short-cycle structured intermittent treatment of chronic HIV infection with highly active antiretroviral therapy: effects on virologic, immunologic, and toxicity parameters

Abstract

Although continuous highly active antiretroviral therapy (HAART) is effective for many HIV-infected patients, it can be toxic and prohibitive in cost. By decreasing the total amount of time patients receive medications, intermittent HAART could reduce toxicity and cost. Therefore, we initiated a pilot study in which 10 HIV-infected individuals receiving effective therapy that resulted in levels of HIV RNA <50 copies per ml of plasma and CD4(+) T cell counts >300 cells per mm(3) of whole blood received repeated cycles of 7 days on HAART followed by 7 days off of HAART. Patients maintained suppression of plasma viremia for 32-68 weeks. There was no significant increase in HIV proviral DNA or replication-competent HIV in peripheral CD4(+) T cells or HIV RNA in peripheral blood or lymph node mononuclear cells. There was no significant change in CD4(+) T cell counts, no significant increase in CD4(+) or CD8(+) T cells expressing activation markers or producing IFN-gamma in response to HIV, no increase in CD4(+) T cell proliferation to p24 antigen, and no evidence for the development of resistance to HAART medications. There was a significant decrease in serum cholesterol and triglyceride levels. Thus, in this proof-of-concept study, short-cycle intermittent HAART maintained suppression of plasma viremia as well as HIV replication in reservoir sites while preserving CD4(+) T cell counts. In addition, there was a decrease in serum cholesterol and triglyceride levels. Intermittent therapy may be an important strategy to reduce cost and toxicity for HIV-infected individuals.

Figure 1

Effect of short-cycle intermittent therapy on plasma HIV RNA. Ten patients receiving cycles of 7 days on HAART followed by 7 days off of HAART had measurements of plasma HIV RNA after every other off-HAART period. The results are shown as HIV RNA copies per ml of plasma as determined by branched-chain DNA assays (bDNA); all values >50 copies per ml of plasma are indicated at the designated time points. Patient 301 was removed from the study (arrow) after a 21-day interruption. Patient 309 had a 10-day interruption during the second off-drug cycle (week 4). Patient 305 withdrew from the study at week 12 for personal reasons.

Figure 2

Effect of short-cycle intermittent therapy on proviral HIV DNA and cell-associated HIV RNA in the peripheral blood. Cell-associated RNA (A) was determined by reverse transcriptase–PCR in 1 million peripheral blood mononuclear cells (PBMC) at enrollment (0 weeks) and after the off-HAART intervals at 12, 24, and 52 weeks of intermittent therapy. Proviral DNA (B) was determined by real-time PCR in 1 million peripheral blood CD4⁺ T cells at the same time points. The means for weeks 0 and 24 are provided as indicated.

Figure 3

Effect of short-cycle intermittent therapy on the frequency of replication-competent HIV in peripheral blood CD4⁺ T cells. Patients who remained on the study regimen were assessed by activation of purified peripheral blood CD4⁺ T cells and determination of infectious units per million cells before enrollment (week 0) and at 12, 24, and 52 weeks of intermittent therapy. The medians for weeks 0 and 24 are provided as indicated.

Figure 4

Effect of short-cycle intermittent therapy on lymph node HIV burden. As evaluated by in situ hybridization, a lymph node section from an untreated control (A, dark field, original magnification ×125) revealed large amounts of HIV RNA seen as silver grains in germinal centers (GC). Lymph node sections from patient 302 after 25 (B) and 52 (C) weeks of intermittent therapy did not demonstrate HIV RNA in the germinal centers (dark fields, original magnification ×125). The biopsies were performed after the on-HAART and off-HAART periods, respectively. Lymph node biopsy specimens obtained at 24–25 weeks of intermittent HAART after either the on-HAART (patient 307, D) or off-HAART period (patients 308 and 310, E and F, respectively) also showed no evidence of HIV RNA in the germinal centers (dark fields, original magnification ×125).

Figure 5

Effect of short-cycle intermittent therapy on CD4⁺ HIV-specific immune responses. Proliferation in response to HIV p24 antigen (A) was determined before enrollment (week 0) and at 12, 24, and 52 weeks of intermittent therapy by [³H]thymidine incorporation, and the results are reported with the background proliferation subtracted. Production of intracellular IFN-γ in response to HIV p24 antigen by CD4⁺ T cells (B) was evaluated at the same time points as determined by flow cytometric analysis and reported as the percentage of CD4⁺ T lymphocytes that were CD69- and IFN-γ-positive. The medians are shown as indicated.

Figure 6

Effect of short-cycle intermittent therapy on CD8⁺ HIV-specific T cell immune responses. The CD8⁺ T cell response to transformed autologous B cells expressing HIV gag, pol, nef, and env was evaluated. The percentage of CD3⁺ CD8⁺ CD69⁺ T cells producing intracellular IFN-γ was determined by flow cytometric analysis before enrollment (week 0) and at 12, 24, and 52 weeks of intermittent therapy. The percentages shown are cumulative for the four gene products with the background β-galactosidase activity subtracted. The medians are shown as indicated.

Figure 7

Effect of short-cycle intermittent therapy on CD4⁺ T cell counts. The absolute CD4⁺ T cells counts (A) and the percentage of CD4⁺ T cells (B) were determined at the end of every other off-HAART period. The mean values before enrollment (week 0) and at 24 weeks of intermittent therapy are shown as indicated.

Figure 8

Effect of short-cycle intermittent therapy on serum cholesterol and triglyceride levels. Serum total cholesterol (A), low density lipoprotein cholesterol (B), and serum triglyceride levels (C) were determined before enrollment (week 0) and at 24 and 52 weeks of intermittent therapy. The mean levels are shown as indicated.