Augmented HIV-specific interferon-gamma responses, but impaired lymphoproliferation during interruption of antiretroviral treatment initiated in primary HIV infection

Abstract

Background: Antiretroviral therapy (ART) introduced during primary HIV infection followed by treatment interruption (TI) is postulated to enhance virologic control through induction of HIV-specific CD4 T cells, which foster virus-specific CD8+ T cells that suppress virus replication. This hypothesis was evaluated in 21 subjects enrolled in AIDS Clinical Trials Group 709, a substudy of AIDS Clinical Trials Group 371, which prospectively evaluated subjects who received ≥1 year of ART initiated in acute or recent HIV infection followed by TI.

Methods: Lymphoproliferation was assessed by [methyl-H] thymidine incorporation and HIV-specific CD8+ T-cell interferon-gamma responses by enzyme-linked immunospot-forming assays. Virologic success was defined as sustained viral load <5000 copies per milliliter for 24 weeks after TI.

Results: HIV-specific lymphoproliferative responses were detected at least once in 5 (24%) of 21 subjects, were generally transient, and were unrelated to HIV-specific interferon-gamma responses (P > 0.4). HIV-specific CD8+ interferon-gamma responses increased after 48 weeks of ART (P = 0.03), but failed to predict virologic success (P = 0.18). Compared with seronegative subjects, lymphoproliferation to Candida, cytomegalovirus, and alloantigens was similar in HIV-infected subjects during ART, but lower during TI (P ≤ 0.04).

Conclusions: HIV-specific CD8+ T-cell interferon-gamma responses expand during ART following primary HIV infection, but are not related to HIV-specific lymphoproliferative responses nor virologic success. Impaired non-HIV antigen-specific lymphoproliferation associated with TI suggests this strategy could be deleterious.

Figures

Figure 1

Lymphoproliferative responses to microbial antigens and alloantigens in individuals with primary HIV infection before and during ART and TI. PBMC from HIV-infected and seronegative control subjects were stimulated with (A) HIV env antigen, (B) HIV p24 antigen, (C) Tetanus toxoid, (D) MAC antigen, (E) Candida antigen (F) CMV antigen, and (G) alloantigens for six days, proliferation was assessed by [methyl-3H]thymidine incorporation, and the stimulation index was determined relative to control wells. Horizontal bars indicate median values. Seronegative subjects had lymphoproliferative assays performed on 4 (range, 1 to 13) different days; each donor’s geometric mean SI is plotted. Diamonds indicate subjects with acute HIV infection, octagons indicate subjects with recent HIV infection, and triangles indicate seronegative subjects. Open symbols indicate HIV-infected subjects who achieved virologic success after one or two TI, and closed symbolss indicate HIV-infected subjects who did not achieve virologic success. Asterisks (*) indicate results in seropositive subjects that were statistically different from those in seronegative controls. Horizontal gray dotted lines indicate a SI of 3, the threshold value for a positive response.

Figure 2

Frequencies of HIV-specific interferon-gamma responses in HIV-infected subjects before and after one year of ART. HIV-specific interferon-gamma responses were determined in ELISPOT assays using overlapping peptides to HIV env, gag, nef, pol and rev. Diamonds indicate subjects with acute HIV infection, and octagons indicate subjects with recent HIV infection Open symbols indicate HIV-infected subjects who achieved virologic success after one or two TI, and closed symbolss indicate subjects who did not achieve virologic success. Horizontal lines indicate median values.

Figure 3

HIV-specific interferon-gamma responses (triangles) and plasma viral loads (circles) during the study from subjects with virologic success (A–C) and virologic failure (D–F). Periods of TI are indicated in gray. Subject A met the study definition of virologic success during the first TI, but subsequently experienced three consecutive viral loads >5,000 copies/mL requiring reinstitution of ART. He failed to maintain virologic suppression below 5,000 copies/mL during the second TI. Subjects B and C both achieved virologic success during the first TI, and maintained low-level viremia throughout the rest of the study. Subjects D–F failed virologically during both the first and the second TI. Subject F remained off ART after virologic failure during the second TI by his own choice, not in accordance with study protocol. Subjects A and B were recruited during acute HIV infection, and the other subjects were recruited during recent HIV infection.