Cellular immune responses and viral diversity in individuals treated during acute and early HIV-1 infection

Abstract

Immune responses induced during the early stages of chronic viral infections are thought to influence disease outcome. Using HIV as a model, we examined virus-specific cytotoxic T lymphocytes (CTLs), T helper cells, and viral genetic diversity in relation to duration of infection and subsequent response to antiviral therapy. Individuals with acute HIV-1 infection treated before seroconversion had weaker CTL responses directed at fewer epitopes than persons who were treated after seroconversion. However, treatment-induced control of viremia was associated with the development of strong T helper cell responses in both groups. After 1 yr of antiviral treatment initiated in acute or early infection, all epitope-specific CTL responses persisted despite undetectable viral loads. The breadth and magnitude of CTL responses remained significantly less in treated acute infection than in treated chronic infection, but viral diversity was also significantly less with immediate therapy. We conclude that early treatment of acute HIV infection leads to a more narrowly directed CTL response, stronger T helper cell responses, and a less diverse virus population. Given the need for T helper cells to maintain effective CTL responses and the ability of virus diversification to accommodate immune escape, we hypothesize that early therapy of primary infection may be beneficial despite induction of less robust CTL responses. These data also provide rationale for therapeutic immunization aimed at broadening CTL responses in treated primary HIV infection.

Figure 1

HIV-1–specific CTL responses determined by screening PBMCs in an Elispot assay using overlapping peptides (15–20 mer) spanning HIV-1 p17 (Gag), p24 (Gag), RT, gp41 (Env), gp120 (Env), and Nef sequences (A, black bars) and reported or subsequently defined optimal epitopes (B, gray bars). CTL magnitudes are expressed as SFCs/10⁶ PBMCs. B shows all the previously reported and newly defined optimal CTL epitopes described for the HLA-type of the individual (AC05: HLA-A3/-, B14/60, Cw3/8). These epitopes are contained in the corresponding overlapping peptides in A. In C–E, the cytolytic activity of CTL clones isolated for the three epitopes recognized in this individual in p24 (Gag), gp41 (Env), and Nef is shown. Lytic activity is given as percentage of specific lysis at two different E/T ratios for autologous target cells either pulsed or not pulsed with the corresponding peptide. In F, the correlation between CTL responses to optimal HIV-1 CTL epitopes (9 to 10 mer) and corresponding overlapping peptides (15–20 mer) including the sequence of the optimal CTL epitope is shown. Each optimal epitope/overlapping peptide pair is represented by a single dot and frequencies are given as SFCs/10⁶ PBMCs.

Figure 2

(A) Longitudinal CTL frequencies in persons with acute HIV-1 infection. Mean total CTL frequencies directed against optimal CTL epitopes and standard error for the 19 subjects treated before HIV-1 seroconversion (group 1, preseroconversion acute HIV) during acute HIV-1 infection before treatment (0 mo) and after 2, 6, and 12 mo of treatment with HAART are shown as SFCs/10⁶ (Mill) PBMCs. The median number of optimal HIV-1 CTL epitopes recognized is indicated by the number within the bar. Significance of differences between mean total CTL frequencies were calculated by two-tailed paired t test and only P values < 0.05 are shown. (B) Longitudinal CTL frequencies in persons with early HIV-1 infection. Mean total CTL frequencies directed against optimal CTL epitopes and standard error for the 11 subjects treated after HIV-1 seroconversion, but within 180 d of infection (group 2, postseroconversion primary HIV) before treatment (0 mo) and after 2, 6, and 12 mo of treatment with HAART are shown as SFCs/10⁶ PBMCs. The median number of optimal HIV-1 CTL epitopes recognized is indicated by the figure within the bar. Significance of differences between mean total CTL frequencies were calculated by two-tailed paired t test and only P values < 0.05 are shown.

Figure 3

(A) Breadth of CTL responses in HIV infection: the number of optimal HIV-1–specific CTL epitopes recognized in each individual studied after 1 yr of treatment with HAART is shown as a single dot. Breadth of CTL responses was compared between the persons with treated acute HIV-1 infection (preseroconversion [pre-SC]; n = 19), the persons treated postseroconversion (post-SC), but within 180 d of infection (n = 11), and the persons first treated in the chronic phase of infection (chronic; n = 10). A horizontal line indicates median number of recognized CTL epitopes for each group, and significance of differences between the groups was calculated by two-tailed t test. (B) T helper cell responses in HIV-1 infection: HIV-1 Gag-specific T helper cell responses were assessed among persons with treated acute HIV-1 infection (preseroconversion; n = 19) after 1 yr on therapy. These were compared with HIV-1 Gag-specific T helper cell responses in persons treated postseroconversion, but within 180 d of infection (n = 11) and persons first treated in the chronic phase of infection (n = 10). A horizontal line indicates the mean SI for each group and significance of differences between the groups was calculated by two-tailed t test.

Figure 4

Viral diversification using the HMA focused on the env C2-V5 region: diversification of the HIV-1 env C2-V5 region is shown for persons with treated acute HIV-1 infection (preseroconversion [pre-SC]), persons treated postseroconversion, but within 180 d of infection (post-SC) and persons first treated in the chronic phase of infection (chronic) in A. B shows the RD measured by HMA for the seven individuals of each group, for whom sufficient amounts of proviral DNA was isolated to perform analysis (1, AC16; 2, AC01; 3, AC03, 4, AC04, 5, AC09; 6, AC13; 7, AC22; 8, AC14; 9, AC10; 10, AC25; 11, AC21; 12, AC29; 13, OP286; 14, OP314; 15, 6001; 16, 6002; 17, 6003; 18, 6006; 19, 6007; 20, 6009; and 21, 6010).

Figure 4

Viral diversification using the HMA focused on the env C2-V5 region: diversification of the HIV-1 env C2-V5 region is shown for persons with treated acute HIV-1 infection (preseroconversion [pre-SC]), persons treated postseroconversion, but within 180 d of infection (post-SC) and persons first treated in the chronic phase of infection (chronic) in A. B shows the RD measured by HMA for the seven individuals of each group, for whom sufficient amounts of proviral DNA was isolated to perform analysis (1, AC16; 2, AC01; 3, AC03, 4, AC04, 5, AC09; 6, AC13; 7, AC22; 8, AC14; 9, AC10; 10, AC25; 11, AC21; 12, AC29; 13, OP286; 14, OP314; 15, 6001; 16, 6002; 17, 6003; 18, 6006; 19, 6007; 20, 6009; and 21, 6010).

Figure 5

Correlation between baseline HIV-1 RNA load (copies per ml plasma) before the initiation of treatment and the number of optimal HIV-1 CTL epitopes recognized for persons with treated acute HIV-1 infection (A, n = 19) and persons treated postseroconversion, but within 180 d of infection (B, n = 11).

Figure 5

Correlation between baseline HIV-1 RNA load (copies per ml plasma) before the initiation of treatment and the number of optimal HIV-1 CTL epitopes recognized for persons with treated acute HIV-1 infection (A, n = 19) and persons treated postseroconversion, but within 180 d of infection (B, n = 11).