Screening for CD8 cytotoxic T lymphocytes specific for Gag of human immunodeficiency virus type 1 subtype B′ Henan isolate from China and identification of novel epitopes restricted by the HLA-A2 and HLA-A11 alleles

Functional Profile of CD8+ T-Cells in Response to HLA-A*02:01-Restricted Mutated Epitopes Derived from the Gag Protein of Circulating HIV-1 Strains from Medellín, Colombia

CD8⁺ T-cells play a crucial role in the control of HIV replication. HIV-specific CD8⁺ T-cell responses rapidly expand since the acute phase of the infection, and it has been observed that HIV controllers harbor CD8⁺ T-cells with potent anti-HIV capacity. The development of CD8⁺ T-cell-based vaccine against HIV-1 has focused on searching for immunodominant epitopes. However, the strong immune pressure of CD8⁺ T-cells causes the selection of viral variants with mutations in immunodominant epitopes. Since HIV-1 mutations are selected under the context of a specific HLA-I, the circulation of viral variants with these mutations is highly predictable based on the most prevalent HLA-I within a population. We previously demonstrated the adaptation of circulating strains of HIV-1 to the HLA-A*02 molecule by identifying mutations under positive selection located in GC9 and SL9 epitopes derived from the Gag protein. Also, we used an in silico prediction approach and evaluated whether the mutations found had a higher or lower affinity to the HLA-A*02. Although this strategy allowed predicting the interaction between mutated peptides and HLA-I, the functional response of CD8⁺ T-cells that these peptides induce is unknown. In the present work, peripheral blood mononuclear cells from 12 HIV-1⁺ HLA-A*02:01⁺ individuals were stimulated with the mutated and wild-type peptides derived from the GC9 and SL9 epitopes. The functional profile of CD8⁺ T-cells was evaluated using flow cytometry, and the frequency of subpopulations was determined according to their number of functions and the polyfunctionality index. The results suggest that the quality of the response (polyfunctionality) could be associated with the binding affinity of the peptide to the HLA molecule, and the functional profile of specific CD8⁺ T-cells to mutated epitopes in individuals under cART is maintained.

Immunization of BLT Humanized Mice Redirects T Cell Responses to Gag and Reduces Acute HIV-1 Viremia

BLT (bone marrow-liver-thymus) humanized mice, which reconstitute a functional human immune system, develop prototypic human virus-specific CD8⁺ T cell responses following infection with human immunodeficiency virus type 1 (HIV-1). We explored the utility of the BLT model for HIV-1 vaccine development by immunizing BLT mice against the conserved viral Gag protein, utilizing a rapid prime-boost protocol of poly(lactic-co-glycolic) acid microparticles and a replication-defective herpes simplex virus (HSV) recombinant vector. After HIV-1 challenge, the mice developed broad, proteome-wide gamma interferon-positive (IFN-γ⁺) T cell responses against HIV-1 that reached magnitudes equivalent to what is observed in HIV-1-infected individuals. The functionality of these responses was underscored by the consistent emergence of escape mutations in multiple CD8⁺ T cell epitopes during the course of infection. Although prechallenge vaccine-induced responses were largely undetectable, the Gag immunization increased both the magnitude and the kinetics of anamnestic Gag-specific T cell responses following HIV-1 infection, and the magnitude of these postchallenge Gag-specific responses was inversely correlated with acute HIV-1 viremia. Indeed, Gag immunization was associated with a modest but significant 0.5-log reduction in HIV-1 viral load when analyzed across four experimental groups of BLT mice. Notably, the HSV vector induced elevated plasma concentrations of polarizing cytokines and chemotactic factors, including interleukin-12p70 (IL-12p70) and MIP-1α, which were positively correlated with the magnitude of Gag-specific responses. Overall, these results support the ability of BLT mice to recapitulate human pathogen-specific T cell responses and to respond to immunization; however, additional improvements to the model are required to develop a robust system for testing HIV-1 vaccine efficacy.IMPORTANCE Advances in the development of humanized mice have raised the possibility of a small-animal model for preclinical testing of an HIV-1 vaccine. Here, we describe the capacity of BLT humanized mice to mount broadly directed HIV-1-specific human T cell responses that are functionally active, as indicated by the rapid emergence of viral escape mutations. Although immunization of BLT mice with the conserved viral Gag protein did not result in detectable prechallenge responses, it did increase the magnitude and kinetics of postchallenge Gag-specific T cell responses, which was associated with a modest but significant reduction in acute HIV-1 viremia. Additionally, the BLT model revealed immunization-associated increases in the plasma concentrations of immunomodulatory cytokines and chemokines that correlated with more robust T cell responses. These data support the potential utility of the BLT humanized mouse for HIV-1 vaccine development but suggest that additional improvements to the model are warranted.

Identification of novel HIV-1-derived HLA-E-binding peptides

Non-classical class Ib MHC-E molecule is becoming an increasingly interesting component of the immune response. It is involved in both the adaptive and innate immune responses to several chronic infections including HIV-1 and, under very specific circumstances, likely mediated a unique vaccine protection of rhesus macaques against pathogenic SIV challenge. Despite being recently in the spotlight for HIV-1 vaccine development, to date there is only one reported human leukocyte antigen (HLA)-E-binding peptide derived from HIV-1. In an effort to help start understanding the possible functions of HLA-E in HIV-1 infection, we determined novel HLA-E binding peptides derived from HIV-1 Gag, Pol and Vif proteins. These peptides were identified in three independent assays, all quantifying cell-surface stabilization of HLA-E*01:01 or HLA-E*01:03 molecules upon peptide binding, which was detected by HLA-E-specific monoclonal antibody and flow cytometry. Thus, following initial screen of over 400 HIV-1-derived 15-mer peptides, 4 novel 9-mer peptides PM9, RL9, RV9 and TP9 derived from 15-mer binders specifically stabilized surface expression of HLA-E*01:03 on the cell surface in two separate assays and 5 other binding candidates EI9, MD9, NR9, QF9 and YG9 gave a binding signal in only one of the two assays, but not both. Overall, we have expanded the current knowledge of HIV-1-derived target peptides stabilizing HLA-E cell-surface expression from 1 to 5, thus broadening inroads for future studies. This is a small, but significant contribution towards studying the fine mechanisms behind HLA-E actions and their possible use in development of a new kind of vaccines.

Conservation of HIV-1 T cell epitopes across time and clades: validation of immunogenic HLA-A2 epitopes selected for the GAIA HIV vaccine

HIV genomic sequence variability has complicated efforts to generate an effective globally relevant vaccine. Regions of the viral genome conserved in sequence and across time may represent the "Achilles' heel" of HIV. In this study, highly conserved T-cell epitopes were selected using immunoinformatics tools combining HLA-A2 supertype binding predictions with relative global conservation. Analysis performed in 2002 on 10,803 HIV-1 sequences, and again in 2009, on 43,822 sequences, yielded 38 HLA-A2 epitopes. These epitopes were experimentally validated for HLA binding and immunogenicity with PBMCs from HIV-infected patients in Providence, Rhode Island, and/or Bamako, Mali. Thirty-five (92%) stimulated an IFNγ response in PBMCs from at least one subject. Eleven of fourteen peptides (79%) were confirmed as HLA-A2 epitopes in both locations. Validation of these HLA-A2 epitopes conserved across time, clades, and geography supports the hypothesis that such epitopes could provide effective coverage of virus diversity and would be appropriate for inclusion in a globally relevant HIV vaccine.

Further progress on defining highly conserved immunogenic epitopes for a global HIV vaccine: HLA-A3-restricted GAIA vaccine epitopes

Two major obstacles confronting HIV vaccine design have been the extensive viral diversity of HIV-1 globally and viral evolution driven by escape from CD8(+) cytotoxic T-cell lymphocyte (CTL)-mediated immune pressure. Regions of the viral genome that are not able to escape immune response and that are conserved in sequence and across time may represent the "Achilles' heel" of HIV and would be excellent candidates for vaccine development. In this study, T-cell epitopes were selected using immunoinformatics tools, combining HLA-A3 binding predictions with relative sequence conservation in the context of global HIV evolution. Twenty-seven HLA-A3 epitopes were chosen from an analysis performed in 2003 on 10,803 HIV-1 sequences, and additional sequences were selected in 2009 based on an expanded set of 43,822 sequences. These epitopes were tested in vitro for HLA binding and for immunogenicity with PBMCs of HIV-infected donors from Providence, Rhode Island. Validation of these HLA-A3 epitopes conserved across time, clades, and geography supports the hypothesis that epitopes such as these would be candidates for inclusion in our globally relevant GAIA HIV vaccine constructs.

Clinical features and major histocompatibility complex genes as potential susceptibility factors in pediatric immune thrombocytopenia

BACKGROUND/PURPOSE

Immune thrombocytopenia (ITP) is a heterogeneous autoimmune disorder with diverse response rates to treatments that include corticosteroids, intravenous immunoglobulins (IVIG), and splenectomy. The predisposing causes of this autoimmune disorder, one of which is immunogenetic susceptibility, have not been fully determined. We investigated whether clinical features and human leukocyte antigen (HLA) genotypes influence the occurrence, treatment response, and disease duration of childhood ITP in Taiwan.

METHODS

We performed HLA genotyping of 70 Taiwanese children with ITP and of 70 healthy controls and compared the data. Demographic data were also collected and evaluated.

RESULTS

The frequencies of heterozygous HLA-A11 and the HLA-Cw1 allele were both significantly decreased in the ITP group (p = 0.0160 and p = 0.0089, respectively), whereas the frequency of heterozygous HLA-DQ5 was significantly increased in the ITP group (p = 0.0057). Patients with HLA-DRB1*11 or -DRB1*15 were more likely to respond poorly to corticosteroids than IVIG (p = 0.0446 and p = 0.0008, respectively). In addition, we observed a positive association between HLA-A11 homozygosity and the development of persistent or chronic ITP [odds ratio (OR) = 6.3165, p = 0.0479]. The presence of HLA-DRB1*08 was, however, negatively correlated with the development of persistent or chronic ITP (OR = 0.1729, p = 0.0657). Children with antecedent of preceding illness (API) and with a younger age of onset were more likely to experience a better treatment response and shorter course of ITP.

CONCLUSION

We suggest that API, age of onset, and particular HLA class I and class II alleles, may be involved in and influence the occurrence and disease duration of childhood ITP, as well as responses to different therapeutic approaches.

Genetic analysis of HIV type 1 env gene in cerebrospinal fluid and plasma of infected Chinese paid blood donors

HIV infection in the central nervous system (CNS) can progress to AIDS dementia complex (ADC). Currently, the HIV-1 env gene in the CNS of infected Chinese paid blood donors (PBDs) has not been well characterized. In the study, the C2-V5 regions of the HIV env gene were cloned and sequenced from both cerebrospinal fluid (CSF) and plasma samples of six HIV-infected Chinese PBDs. Sequence analysis revealed that the sequences from Henan province clustered closely with subtypes B' and B, and the levels of diversity from the CNS were significantly lower than those from blood (p<0.0001). In addition, all viral quasispecies from CNS use CCR5 as the coreceptor. These data provide valuable information on HIV pathogenesis in the CSF and plasma of infected Chinese PBDs, and our findings could enhance insights into HIV-associated neurological disease.

Extensive HLA-driven viral diversity following a narrow-source HIV-1 outbreak in rural China

Obstacles to developing an HIV-1 vaccine include extensive viral diversity and lack of correlates of protective immunity. High mutation rates allow HIV-1 to adapt rapidly to selective forces such as antiretroviral therapy and immune pressure, including HIV-1-specific CTLs that select viral variants which escape T-cell recognition. Multiple factors contribute to HIV-1 diversity, making it difficult to disentangle the contribution of CTL selection without using complex analytical approaches. We describe an HIV-1 outbreak in 231 former plasma donors in China, where a narrow-source virus that had contaminated the donation system was apparently transmitted to many persons contemporaneously. The genetic divergence now evident in these subjects should uniquely reveal how much viral diversity at the population level is solely attributable to host factors. We found significant correlations between pair-wise divergence of viral sequences and HLA class I genotypes across epitope-length windows in HIV-1 Gag, reverse transcriptase, integrase, and Nef, corresponding to sites of 140 HLA class I allele-associated viral polymorphisms. Of all polymorphic sites across these 4 proteins, 24%-56% were sites of HLA-associated selection. These data confirm that CTL pressure has a major effect on inter-host HIV-1 viral diversity and probably represents a key element of viral control.

Glycoprotein 96-mediated presentation of human immunodeficiency virus type 1 (HIV-1)-specific human leukocyte antigen class I-restricted peptide and humoral immune responses to HIV-1 p24

Viral antigens complexed to heat shock proteins (HSPs) can enhance antiviral immunity. The present study evaluated the immunogenicity of a novel human immunodeficiency virus type 1B' (HIV-1B')-specific, human leukocyte antigen A2 (HLA-A2)-restricted peptide (FLQSRPEPTA, Gag(448-457)) and the cellular immune adjuvant effect of HSP gp96 using the HLA-A2 transgenic mouse model. It was found that gp96 could augment cytotoxic-T-lymphocyte responses specific for the 10-mer peptide of HIV-1B'. This study also evaluated the humoral immune adjuvant effect of HSP gp96 and its N-terminal fragment (N336) and found that immunization of BALB/c mice with a mixture of gp96 or its N-terminal fragment and HIV-1 p24 antigen or with an p24-N336 fusion protein resulted in a significant increase in anti-HIV p24 antibody titer. These results demonstrate the possibility of using gp96 and its N fragment as adjuvants to augment cellular and humoral immune responses against HIV-1 infection.

Molecular characterization of the HIV type 1 vpr gene in infected Chinese former blood/plasma donors at different stages of diseases

The HIV-1 vpr regions were PCR amplified and sequenced from eight long-term nonprogressors' (LTNP) and seven AIDS patients' DNA samples of a cohort of HIV-1-infected Chinese plasma/blood donors (PBDs). Sequence analysis revealed that the patients' HIV-1 vpr sequences belong to HIV-1 subtype B and there were no differences in the divergence of vpr sequences between these two groups of patients. Similarly, in the deduced amino acid sequences, no significant differences have been detected in vpr functional domains from patients at different stages of the disease. Moreover, the predicted binding motifs of HLA A2 and A11 were highly conserved among patients' vpr amino acid sequences. These results show that vpr may not play an important role in HIV-1 pathogenesis in different stages of Chinese patients and may have important implications in developing vpr-related treatments suitable for HIV-1-infected PBDs.

Lack of differences in HIV-1 nef functional domains in infected chinese blood donors at different stages of disease

HIV-1 nef regions were amplified by polymerase chain reaction and sequenced from DNA samples of five asymptomatic subjects and five AIDS patients from a cohort of HIV-1-infected Chinese plasma and blood donors. Sequence analysis revealed that regardless of the stage of disease, each patient's HIV-1 nef sequences belonged to the clade B' subtype. Although there are some differences between the sequences from different patients, no significant differences have been detected in nef nucleotide sequences or functional motifs in the deduced amino acid sequences from patients at different stages of the disease. Furthermore, the predicted binding motifs of HLA-A2 and HLA-A11 were highly conserved among patient nef sequences. These results will contribute to a better understanding of the pathogenesis of circulating HIV-1 in infected Chinese former blood donors and may have important implications in developing an epitope-based vaccine suitable for Chinese blood donors.