CD4+ T-lymphocyte lines developed from HIV-1-seropositive patients recognize different epitopes within the V3 loop

Identification of immunodominant CD4-restricted epitopes co-located with antibody binding sites in individuals vaccinated with ALVAC-HIV and AIDSVAX B/E

We performed fine epitope mapping of the CD4+ responses in the ALVAC-HIV-AIDSVAX B/E prime-boost regimen in the Thai Phase III trial (RV144). Non-transformed Env-specific T cell lines established from RV144 vaccinees were used to determine the fine epitope mapping of the V2 and C1 responses and the HLA class II restriction. Data showed that there are two CD4+ epitopes contained within the V2 loop: one encompassing the α4β7 integrin binding site (AA179-181) and the other nested between two previously described genetic sieve signatures (AA169, AA181). There was no correlation between the frequencies of CD4+ fine epitope responses and binding antibody.

Fine specificity and cross-clade reactivity of HIV type 1 Gag-specific CD4+ T cells

Despite growing evidence that HIV-1-specific CD4(+) T helper (Th) cells may play a role in the control of viremia, discrete Th cell epitopes remain poorly defined. Furthermore, it is not known whether Th cell responses generated using vaccines based on clade B virus sequences will elicit immune responses that are effective in regions of the world where non-clade B viruses predominate. To address these issues we isolated CD4(+) T cell clones from individuals with vigorous HIV-1-specific Th cell responses and identified the minimum epitopes recognized. The minimum peptide length required for induction of CD4(+) T cell proliferation, IFN-gamma secretion, and cytolytic activity ranged from 9 to 16 amino acids in the five epitopes studied. Cross-clade recognition of the defined epitopes was examined for variant peptides from clades A, B, C, D, and AE. Over half the variant epitopes (17 of 32) exhibited impaired recognition, defined as less than 50% of the IFN-gamma secretion elicited by B clade consensus sequence. There was no evidence for antagonistic activity mediated by the variant peptides, and despite strong responses there was no escape of autologous virus from Th responses in the epitopes we studied. Abrogated recognition of variant CD4(+) T cell epitopes presents a potential obstacle to vaccine development.

Comparison between env-specific T-cell epitopic responses in HIV-1-uninfected adults immunized with combination of ALVAC-HIV(vCP205) plus or minus rgp160MN/LAI-2 and HIV-1-infected adults

In this study, we investigated the CD4 T-helper response induced by ALVAC-HIV(vCP205) +/- rgp160MN/LAI-2 using a series of 15 overlapping amino acid peptides spanning the entire gp160MN/LAI-2 antigen. CD4 Env-specific T-cell lines were established from three groups of HIV-1-negative HIV vaccine recipients: vCP205 + gp160MN/LAI-2, vCP205 only, and gp160MN/LAI-2 only. CD4 Env-specific T-cell lines established from individuals who received the prime-boost vCP205 + rgp160MN/LAI-2 generated strong and broad T-helper responses scattered across the Env sequence, whereas Env-specific T-cell lines from individuals receiving the vCP205 vaccine alone generated reactivity to only a few peptides. CD4 -specific T-cell lines were also established from HIV-1-infected individuals and demonstrated poor reactogenicity to Env peptides in both breadth and amplitude of response. These results highlight the complexity of major histocompatibility complex class II presentation and CD4 antigen-specific reactivity, emphasizing the need to better understand these crucial T-helper cell responses in the setting of HIV infection and HIV vaccine development.

Substitutions in a major histocompatibility complex class II-restricted human immunodeficiency virus type 1 gp120 epitope can affect CD4+ T-helper-cell function

It has been suggested that the inability of the immune response to control human immunodeficiency virus type 1 (HIV-1) replication may be due, at least in part, to the capacity of this virus to escape from immune recognition through mutation. While there is increasing evidence for the importance of HIV-1-specific CD4+ T cells in containing HIV-1 spread in the infected individual, little is known about the consequences of HIV-1 mutation on virus-specific CD() T-cell function. The impact of HIV-1 sequence variation on CD4+ T-helper (Th)- cell function was assessed with a rhesus monkey model for immune recognition of the HIV-1 envelope (Env) glycoprotein. A series of HIV-1 Env(484-496) variant peptides were shown to retain the ability to bind to the appropriate rhesus monkey major histocompatibility complex class II DR molecule. Peptides bearing substitutions at position 490, however, failed to drive the proliferation or cytokine secretion of two well-characterized HXBc2 Env-specific rhesus monkey CD4+ Th-cell lines. Exogenous costimulation was ineffective in complementing the ability of the nonstimulatory peptides to induce [3H]thymidine incorporation by these cells. Finally, HIV-1 Env(484-496) variant peptides with substitutions at position 490 antagonized the HXBc2 Env peptide-induced proliferative response of the CD4+ Th-cell lines. Thus, HIV-1 variants appear to have the capacity to neutralize the function of virus-specific CD4+ T lymphocytes.

CD4+ T-cell recognition of diverse clade B HIV-1 isolates

OBJECTIVES

To evaluate the effect of sequence variation within the gp120 V3 loop on CD4 T-cell recognition.

DESIGN

CD4 T-cell clones were generated using synthetic peptides to circumvent the difficulties of using polyclonal T-cell responses. Peptides based on other HIV isolates were then used to determined the influence of single and multiple sequence differences.

RESULTS

Three of the panels of T-lymphocyte clones (TLC), which were all specific to diverse HIV-1 clade B gp120 V3-loop peptides differing in a limited number of residues, had heterogeneous patterns of response to peptides differing in length and sequence indicating that they recognized distinct but overlapping epitopes. The panels of TLC also differed in the extent to which they tolerated sequence differences between cell-culture-adapted or primary HIV-1 isolates. One panel responded to peptides based on several clade B and one clade D isolate. In contrast, two panels, generated from two different donors using the same peptide, only responded to a limited number of clade B isolates, whereas another only recognized HIV-1BRU. Two of the panels were also stimulated by peptides based on clinical isolates from one patient with some sequence changes enhancing T-cell recognition.

CONCLUSIONS

These data are consistent with highly diverse CD4 T-cell recognition of the HIV-1 gp120 V3 loop, which is influenced by the sequence differences within the T-cell epitopic region and has implications for the pathogenesis and design of vaccines against HIV-1.