Limited Durability of Viral Control following Treated Acute HIV Infection

BACKGROUND: Early treatment of acute HIV infection with highly active antiretroviral therapy, followed by supervised treatment interruption (STI), has been associated with at least transient control of viremia. However, the durability of such control remains unclear. Here we present longitudinal follow-up of a single-arm, open-label study assessing the impact of STI in the setting of acute HIV-1 infection. METHODS AND FINDINGS: Fourteen patients were treated during acute HIV-1 infection and subsequently subjected to an STI protocol that required retreatment if viral load exceeded 50,000 RNA copies/ml plasma or remained above 5,000 copies/ml for more than three consecutive weeks. Eleven of 14 (79%) patients were able to achieve viral loads of less than 5,000 RNA copies/ml for at least 90 d following one, two, or three interruptions of treatment. However, a gradual increase in viremia and decline in CD4+ T cell counts was observed in most individuals. By an intention-to-treat analysis, eight (57%), six (43%), and three (21%) of 14 patients achieved a maximal period of control of 180, 360, and 720 d, respectively, despite augmentation of HIV-specific CD4+ and CD8+ T cell responses. The magnitude of HIV-1-specific cellular immune responses before treatment interruption did not predict duration of viremia control. The small sample size and lack of concurrent untreated controls preclude assessment of possible clinical benefit despite failure to control viremia by study criteria. CONCLUSIONS: These data indicate that despite initial control of viremia, durable viral control to less than 5,000 RNA copies/ml plasma in patients following treated acute HIV-1 infection occurs infrequently. Determination of whether early treatment leads to overall clinical benefit will require a larger and randomized clinical trial. These data may be relevant to current efforts to develop an HIV-1 vaccine designed to retard disease progression rather than prevent infection since they indicate that durable maintenance of low-level viremia may be difficult to achieve

Consistent Patterns in the Development and Immunodominance of Human Immunodeficiency Virus Type 1 (HIV-1)-Specific CD8(+) T-Cell Responses following Acute HIV-1 Infection

Human immunodeficiency virus type 1 (HIV-1)-specific CD8(+) T-cell responses generated during acute infection play a critical role in the initial control of viremia. However, little is known about the viral T-cell epitopes targeted during acute infection or about their hierarchy in appearance and relative immunodominance over time. In this study, HIV-1-specific CD8(+) T-cell responses in 18 acutely infected individuals expressing HLA-A3 and/or -B7 were characterized. Detailed analysis of CD8 responses in one such person who underwent treatment of acute infection followed by reexposure to HIV-1 through supervised treatment interruptions (STI) revealed recognition of only two cytotoxic T-lymphocyte (CTL) epitopes during symptomatic acute infection. HIV-1-specific CD8(+) T-cell responses broadened significantly during subsequent exposure to the virus, ultimately targeting 27 distinct CTL epitopes, including 15 different CTL epitopes restricted by a single HLA class I allele (HLA-A3). The same few peptides were consistently targeted in an additional 17 persons expressing HLA-A3 and/or -B7 during acute infection. These studies demonstrate a consistent pattern in the development of epitope-specific responses restricted by a single HLA allele during acute HIV-1 infection, as well as persistence of the initial pattern of immunodominance during subsequent STI. In addition, they demonstrate that HIV-1-specific CD8(+) T-cell responses can ultimately target a previously unexpected and unprecedented number of epitopes in a single infected individual, even though these are not detectable during the initial exposure to virus. These studies have important implications for vaccine design and evaluation

Evolution of Viral Load and CD4+ T Cell Counts during STI

<div><p>(A) Survival curves of time to virologic failure during the first three supervised treatment interruptions. Virologic failure was defined as having a viral load of greater than 5,000 copies RNA/ml plasma for 3 wk or greater than 50,000 copies once. Patients still achieving viral control at the last visit and individuals restarting therapy without meeting criteria or lost in follow-up are censored at the last evaluable time point. The horizontal axis represents the time off therapy since the beginning of the treatment interruption, the vertical axis corresponds to the number of patients maintaining control of viremia. The curves for first, second, and third STIs do not differ significantly from each other (log-rank test, <i>p ></i> 0.05).</p> <p>(B) Evolution of CD4+ T cell counts during the longest treatment interruption. Slopes of CD4+ T cell counts during the first year of the longest treatment interruption are shown for patients who experienced a cessation of therapy of at least 12 mo (all except AC13, AC25, and AC45), compared to the natural decline of CD4+ T cell counts in untreated patients of the MACS cohort with early chronic HIV-1 infection (CD4+ counts of >350 cells/mm³). CD4+ T cell losses were calculated on a regression line based on least squares fit. The two groups differed significantly from each other (Mann-Whitney <i>U</i> test, <i>p =</i> 0.02).</p> <p>(C) CD4+ T cell count at intercept and CD4+ T cell slopes during the longest treatment interruption. The CD4+ T cell slopes of the same 11 patients shown in (B) and of untreated patients of the MACS cohort are represented according to the CD4+ T cell count at the intercept of the regression line based on least squares fit with the vertical axis (day 0 of treatment interruption).</p></div

HIV-1 Viral Loads and CD4+ T Cell Counts in the 14 Study Participants

<p>Time zero corresponds to first institution of highly active antiretroviral therapy (HAART). Closed squares, HIV-1 plasma viral loads; open circles, CD4+ T cell counts; shaded areas, treatment with HAART according to protocol; diagonally shaded areas, patient restarted therapy without meeting criteria of virological failure; vertical dotted lines, virological failure without reinstitution of HAART. Patients are ordered by increasing number of supervised treatment interruptions.</p

Evolution of HIV-1-Specific CD4+ and CD8+ T Cell Responses during STI

<div><p>(A–D) Magnitude and breadth of increase of HIV-specific CD8+ T cells during supervised treatment interruptions.</p> <p>(A and B) Magnitude (A) and breadth (B) of HIV-specific CD8+ responses at the first day of treatment interruption (black bars) and at the last day off therapy (white bars). Data represent the mean and standard deviation.</p> <p>(C and D) Correlation between the increase of the magnitude (C) or breadth (D) of CD8+ T cell responses and the time off therapy during the first treatment interruption.</p> <p>(E and F) Evolution of CD4+ T helper cell responses during supervised treatment interruptions.</p> <p>(E) Magnitude of CD4 T helper cell responses at baseline and at the first day of treatment interruption (closed circles) and last day off therapy (open circles). Horizontal bars correspond to median values. An stimulation index greater than five was considered significant.</p> <p>(F) Correlation between the magnitude of p24-specific lymphocyte proliferative responses at the beginning of the first treatment interruption and the time patients were able to remain off therapy during the subsequent STI.</p></div

Selection, Transmission, and Reversion of an Antigen-Processing Cytotoxic T-Lymphocyte Escape Mutation in Human Immunodeficiency Virus Type 1 Infection

Numerous studies now support that human immunodeficiency virus type 1 (HIV-1) evolution is influenced by immune selection pressure, with population studies showing an association between specific HLA alleles and mutations within defined cytotoxic T-lymphocyte epitopes. Here we combine sequence data and functional studies of CD8 T-cell responses to demonstrate that allele-specific immune pressures also select for mutations flanking CD8 epitopes that impair antigen processing. In persons expressing HLA-A3, we demonstrate consistent selection for a mutation in a C-terminal flanking residue of the normally immunodominant Gag KK9 epitope that prevents its processing and presentation, resulting in a rapid decline in the CD8 T-cell response. This single amino acid substitution also lies within a second HLA-A3-restricted epitope, with the mutation directly impairing recognition by CD8 T cells. Transmission of the mutation to subjects expressing HLA-A3 was shown to prevent the induction of normally immunodominant acute-phase responses to both epitopes. However, subsequent in vivo reversion of the mutation was coincident with delayed induction of new CD8 T-cell responses to both epitopes. These data demonstrate that mutations within the flanking region of an HIV-1 epitope can impair recognition by an established CD8 T-cell response and that transmission of these mutations alters the acute-phase CD8(+) T-cell response. Moreover, reversion of these mutations in the absence of the original immune pressure reveals the potential plasticity of immunologically selected evolutionary changes