Monocyte derived dendritic cells from HIV-1 infected individuals partially reconstitute CD4 T-cell responses

OBJECTIVES: The study tests the hypothesis that monocyte derived dendritic cells from HIV-1 infected individuals are normal and can restore impaired CD4 T-cell antigen specific responses. DESIGN: Monocyte derived dendritic cells were isolated from individuals at three different stages of HIV-1 infection with a wide spectrum of viral load and CD4 T-cell counts, and from healthy volunteers. The cell surface phenotype and allogeneic stimulatory potential of these dendritic cells was documented. CD4 T-cell responses to HIV p24, tetanus toxoid and purified protein derivative were measured using either unfractionated peripheral blood mononuclear cells, or purified dendritic cell/T-cell cultures. RESULTS: Dendritic cells from all three HIV-1 infected groups did not differ from each other or from healthy volunteers in terms of cell surface phenotype or allogeneic stimulatory potential using T cells from healthy volunteers. Dendritic cells from immunosuppressed antiretroviral naive individuals enhanced the autologous recall proliferative responses both to HIV-1 p24, and third party antigens tetanus toxoid and purified protein derivative, both in terms of the proportion of responding individuals, and median proliferation. CONCLUSION: Antigen presentation by dendritic cells partially restores impaired antigen specific CD4 T-cell responses associated with HIV-1 infection. Immunization strategies which target dendritic cells may therefore offer significant advantages in the ability to stimulate HIV-specific protective immune responses.     

Group M-based HIV-1 Gag peptides are frequently targeted by T cells in chronically infected US and Zambian patients

BACKGROUND: The enormous sequence diversity of HIV-1 has been a major obstacle in the development of a globally useful vaccine for AIDS. The consensus and ancestral sequence-based immunogens minimize the genetic distance between contemporary isolates and vaccine strains. Hence these sequences may be promising candidates for HIV vaccines or serve as a universal reagent set for evaluating Gag-specific responses. METHODS: In this study, we measured the T-cell reactivity to consensus (subtype A, B, C and group M), ancestral (group M and subtype B) and HXB2 Gag peptides (15-mers overlapping by 11) in HIV-1-infected subjects from two reference populations. We evaluated the Gag-specific T-cell responses in 43 chronically infected US (subtype B) and 13 Zambian (subtype C) subjects using an interferon-gamma enzyme-linked immunosorbent spot assay. RESULTS: Our findings demonstrate a broad cross-reactivity of nearly 70% among all the seven Gag immunogens evaluated. Consensus M sequences elicited similar levels of responses as did the consensus B, ancestral subtype B and HXB2 peptides in subtype B-infected US patients. In subtype C-infected Zambian subjects, responses of similar breadth and magnitude were elicited by consensus C, consensus M and ancestral M peptides. CONCLUSION: Our data demonstrate that peptide pools based on consensus or ancestral M-based sequences can be used to evaluate Gag-specific responses elicited by subtype B or subtype C-based immunogens.     

T-cell homeostasis alteration in HIV-1 infected subjects with low CD4 T-cell count despite undetectable virus load during HAART

OBJECTIVE: To investigate the pathogenesis of low CD4 T-cell count in subjects who are immunological non responders (InR) to HAART. DESIGN: Thirty-five HIV-positive subjects on HAART for at least 1 year, all with undetectable HIV-1 RNA, were studied. Patients were defined as InR according to a CD4 cell increase < 20% from CD4 cell baseline or CD4 cell count < 200/microl; subjects with a CD4 T-cell increase > 20% from baseline and a CD4 cell count > 200/microl were defined as immunological responders (IR). We performed a comprehensive study to characterize the immune response of InR. METHODS: The immunological phenotype of peripheral blood mononuclear cells, thymic naive T cells, T-cell receptor Vbeta repertoire, serum concentration of interleukin (IL)-7, the expression of IL-7Ralpha on naive and memory CD4 and CD8 T cells, and regulatory T cells (Treg) were studied. RESULTS: In InR a significant reduction (P < 0.0001) of naive and thymic naive CD4 T cells was associated with a reduced expression of IL-7Ralpha in both cell subsets, with an increased serum concentration of IL-7 was observed. Furthermore, an increased immune activation with a reduced Treg frequency and increased number of expansions of Vbeta families was observed. CONCLUSIONS: The reduced expression of IL-7Ralpha associated with the persistent immune activation and the alteration of Treg frequencies in part explains the low level of CD4 T cells observed in InR.     

Gag-specific CD4+ T-cell responses are associated with virological control of paediatric HIV-1 infection

HIV-specific Elispot responses were investigated in 57 antiretroviral therapy-naive children, of median age 9.9 years. CD8(+) T-cell responses were detected in 96% children; Nef was the immunodominant protein. Responses broadened over time, but there was no association between magnitude, breadth or specificity of response and viraemia. Gag-specific CD4(+) T-cell responses, detectable in 26% children, correlated inversely with viraemia (R = -0.43, P < 0.001), suggesting that preservation of this cell population may be an important goal of therapeutic/vaccine strategies.     

Identification of Neospora antigens recognized by CD4+ T cells and immune sera from experimentally infected cattle

Neospora caninum is recognized as a major cause of infectious abortion in cattle. Very little is known about immunity to Neospora . Cell mediated responses have previously been shown to be important in the development of protective immunity to the closely related parasite Toxoplasma gondii , and may therefore be an important component in the immune response to Neospora . In this paper we report that a group of low molecular weight NC1 strain tachyzoite antigens (≤ 30 kDa) separated by SDS PAGE and bound to nitrocellulose membrane stimulated proliferation in vitro of CD4+ T cells from calves experimentally infected with N. caninum . Proliferation was accompanied by production of high concentrations of IFNγ. Several of these antigens were also recognized by antibody produced in these animals. As the most effective vaccines require the stimulation of both humoral and cell mediated immune responses, these antigens may be important in the development of a vaccine against neosporosis.     

Establishment of the CD4+ T-cell pool in healthy children and untreated children infected with HIV-1

Current understanding of how the T-cell pool is established in children and how this is affected by HIV infection is limited. It is widely believed that the thymus is the main source for T cells during childhood. Here we show, however, that healthy children had an age-related increase in total body numbers of naive and memory T cells, whereas absolute numbers of T-cell receptor excision circles (TRECs) did not increase. This suggests that expansion of the naive T-cell pool after birth is more dependent on T-cell proliferation than was previously recognized. Indeed, the proportion of dividing naive T cells was high, especially in younger children, which is consistent with expansion through proliferation, in addition to antigen-mediated naive T-cell activation leading to formation of the memory T-cell pool. In untreated children infected with HIV-1, total body numbers of T cells and TRECs were low and stable, whereas T-cell division levels were significantly higher than in healthy children. We postulate that in children infected with HIV, similar to adults infected with HIV, continuous activation of naive T cells leads to erosion of the naive T-cell pool and may be a major factor in lowering CD4(+) T-cell numbers.     

HIV-1感染者CD73~+CD8~+ T细胞减少与T细胞异常活化的相关性研究

目的探讨HIV-1感染者外周血CD8~+T细胞上CD73的表达特点及其与T细胞异常活化和疾病进展的关系。方法研究入选65例HIV-1感染者和27例健康对照。通过流式细胞术检测研究对象外周血CD73~+CD8~+T细胞的频率和绝对计数,并将患者CD73~+CD8~+T细胞绝对计数和频率与其CD4~+T细胞计数、HIV-1载量以及CD38~+CD8~+T细胞频率进行相关性分析。结果与健康对照相比,HIV-1感染者外周血CD73~+CD8~+T细胞绝对计数和频率均明显降低(P均0.05);HIV-1感染者外周血CD73~+CD8~+T细胞绝对计数和频率与CD4~+T细胞计数呈正相关(r=0.555,P=0.001;r=0.342,P=0.005),与CD38~+CD8~+T细胞频率呈负相关(r=-0.384,P=0.002;r=-0.387,P=0.001);HIV-1感染者CD73~+CD8~+T细胞的绝对计数与HIV-1载量呈弱负相关(r=-0.261,P=0.035)。结论 HIV-1感染者外周血CD73~+CD8~+T细胞的减少不但与患者T细胞的活化程度呈显著负相关,而且与AIDS疾病进展相关。     

Cytotoxic T-cell recognition of HIV-1 cross-clade and clade-specific epitopes in HIV-1-infected Thai and Japanese patients

OBJECTIVE: To identify and characterize cytotoxic T-cell (CTL) epitopes for HIV-1 clade E using eight known HLA-A*1101-restricted HIV-1 clade B epitopes. METHODS: Induction of clade E-specific CTL was examined by stimulating peripheral blood mononuclear cells (PBMC) from clade E-infected Thai individuals with the clade E-specific peptide corresponding to the clade B epitopes. Cross-clade and clade-specific CTL recognition for these epitopes was analysed using CTL clones and bulk CTL specific for these epitopes. To clarify the presentation of these epitopes in HIV-1-infected T cells, CTL recognition for the clade E-specific and cross-clade epitopes was investigated using CD4CXCR4 cells infected with an HIV-1 clade E clone. RESULTS: Three epitopes, which are identical among clades A-E, were recognized as cross-clade CTL epitopes in both individuals. Clade B and E sequences corresponding to three epitopes were recognized as clade-specific epitopes in clade B-infected and clade E-infected individuals, respectively. In contrast, clade E-specific peptides corresponding to two other clade B epitopes failed to elicit clade E-specific CTL. CTL specific for the three cross-clade and three clade E-specific epitopes effectively lysed target cells infected with HIV-1 clade E virus. CONCLUSIONS: These six epitopes are found to be processed naturally in HIV-1 clade E-infected cells. We show here that a strategy utilizing HIV-1 clade B epitopes is very useful for identifying clade E CTL epitopes.     

Serum HIV-1 RNA load to predict CD4+ T-cell depletion in asymptomatic patients

Summary The temporal association between the increase in viral replication and the depletion in CD4⁺ T cells in HIV-1 infection is not yet clear. To investigate this phenomenon HIV-1 RNA was quantified in several frozen sera from 20 asymptomatic HIV-1 infected patients in the 2 years preceding CD4⁺ T cell depletion of 50% or more, and compared with 20 HIV-1 infected paired patients who were stable in the same period. In each group, no statistically significant variation in the mean HIV-1 RNA titre was found between the last checkup and the one 24 months earlier. The mean HIV-1 RNA titre was 10^3.86 copies/ml in the non-progressor group and 10^5.12 copies/ml in the progressor group. These data support the view that the quantity of circulating HIV-1 RNA is an early predictor of disease progression that is relatively constant during the asymptomatic period of HIV-1 infection.

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Vorhersagewert der Serum-HIV-1 RNA-Last für die CD4⁺-T-Zell-Depletion bei asymptomatischen Patienten

Zusammenfassung Die zeitliche Beziehung zwischen der zunehmenden Virusreplikation und Depletion der CD4⁺ T-Zellen bei HIV-1 Infektion ist noch nicht geklärt. Um dieses Phänomen zu untersuchen, haben wir eine Quantifizierung der HIV-1 RNA in mehreren Seren von 20 asymptomatischen HIV-1 infizierten Patienten durchgeführt, die in den Jahren vor einer Verminderung der CD4⁺ T-Zellen um 50% und mehr eingefroren worden waren. Die Werte wurden mit denjenigen von 20 HIV-1 infizierten Patientenpaaren verglichen, die während desselben Zeitraums stabil geblieben waren. In keiner der Gruppen fanden sich statistisch signifikante Unterschiede im mittleren HIV-1 RNA-Titer zwischen der Untersuchung zum Zeitpunkt 24 Monate und der ersten Untersuchung. In der nicht progredienten Gruppe fand sich ein mittlerer HIV-1 RNA-Titer von 10^3,86/ml Kopien, in der progredienten Gruppe 10^5,12/ml. Diese Ergebnisse sprechen dafür, daß die Menge an zirkulierender HIV-1 RNA ein früher Prädiktor der Krankheitsprogression ist, der während der asymptomatischen Phase der HIV-1 Infektion relativ konstant bleibt.

     

A ubiquitous protein is the source of naturally occurring peptides that are recognized by a CD8+ T-cell clone.

We previously isolated from mouse spleen an octapeptide (LSPFPFDL) that in association with the class I major histocompatibility complex protein Ld is recognized by the antigen-specific receptor of an alloreactive CD8+ T-cell clone (2C). Guided by an assay dependent upon the same 2C T-cell receptor, we have now isolated from the same source another naturally occurring peptide. The second peptide (VAITRIEQLSPFPFDL) includes the entire octapeptide sequence and preliminary evidence suggests that it may be a natural precursor of the octapeptide. On finding extensive sequence homology between the 16-mer and part of human 2-oxoglutarate dehydrogenase, we determined the cDNA sequence of mouse 2-oxoglutarate dehydrogenase and found that the deduced amino acid sequence matches precisely the two naturally occurring peptides, indicating their origin by cellular processing of this ubiquitous self protein.     

The HIV-1 regulatory proteins Tat and Rev are frequently targeted by cytotoxic T lymphocytes derived from HIV-1-infected individuals

The HIV-1 regulatory proteins Rev and Tat are expressed early in the virus life cycle and thus may be important targets for the immune control of HIV-1-infection and for effective vaccines. However, the extent to which these proteins are targeted in natural HIV-1 infection as well as precise epitopes targeted by human cytotoxic T lymphocytes (CTL) remain to be defined. In the present study, 57 HIV-1-infected individuals were screened for responses against Tat and Rev by using overlapping peptides spanning the entire Tat and Rev proteins. CD8+ T cell responses against Tat and Rev were found in up to 19 and 37% of HIV-1-infected individuals, respectively, indicating that these regulatory proteins are important targets for HIV-1-specific CTL. Despite the small size of these proteins, multiple CTL epitopes were identified in each. These data indicate that Tat and Rev are frequently targeted by CTL in natural HIV-1 infection and may be important targets for HIV vaccines.     

Functional patterns of HIV-1-specific CD4 T-cell responses in children are influenced by the extent of virus suppression and exposure

BACKGROUND: Virus-specific CD4 T cells play a critical role in antiviral immunity. HIV-1-specific CD4 T cells in chronically infected adults are mostly composed of IFN-gamma-secreting cells, whereas a selective defect in IL-2-secreting CD4 T cells has been demonstrated. HIV-1-specific IL-2-secreting CD4 T cells are key components of effective immunity. OBJECTIVE: To determine the function of HIV-1-specific CD4 T cells in HIV-1 vertically infected children after antiretroviral treatment (ART). DESIGN: Twenty-three vertically HIV-infected children treated with ART for an extended period (mean 7 years) were retrospectively studied. METHODS: The function of HIV-1-specific CD4 T cells was determined by their ability to secrete IL-2 and IFN-gamma after stimulation with HIV-1 p55 gag protein using polychromatic flow cytometry. RESULTS:: Substantial differences in the patterns of CD4 T-cell responses were associated with different conditions of response to ART. Interestingly, children with suppression of viraemia below 50 HIV-1-RNA copies/ml of plasma for at least 2 years showed dominant IL-2 CD4 T-cell responses; children with viraemia below 50 copies but experiencing transient blips of viraemia showed polyfunctional (IL-2 plus IFN-gamma) CD4 T-cell responses; children with uncontrolled high viraemia levels had dominant IFN-gamma CD4 T-cell responses. Furthermore, the total frequency of HIV-1-specific CD4 T cells including IL-2 and IFN-gamma-secreting cells was significantly higher compared with HIV-infected adults with chronic infection. CONCLUSION: The higher frequency of HIV-1-specific CD4 T cells in children compared with adults and the recovery of IL-2-secreting CD4 T cells after successful ART-mediated suppression of virus replication indicate a greater capacity of immune restoration in children than adults.     

Differential immunogenicity of HIV-1 clade C proteins in eliciting CD8+ and CD4+ cell responses

BACKGROUND: The relative immunogenicity of human immunodeficiency virus type 1 (HIV-1) proteins for CD8+ and CD4+ cell responses has not been defined. METHODS: HIV-1-specific T cell responses were evaluated in 65 chronically HIV-1-infected untreated subjects by interferon- gamma flow cytometry with peptides spanning the clade C consensus sequence. RESULTS: The magnitude of HIV-1-specific CD8+ T cell responses correlated significantly with CD4+ cell responses, but the percentage of CD8+ T cells directed against HIV-1 (median, 2.76%) was always greater than that of CD4+ cells (median, 0.24%). Although CD8+ T cell responses were equally distributed among Gag, Pol, and the regulatory and accessory proteins, Gag was the dominant target for CD4+ cell responses. There was no consistent relationship between virus-specific CD8+ or CD4+ cell response and viral load. However, the median viral load in subjects in whom Gag was the dominant CD8+ T cell target was significantly lower than that in subjects in whom non-Gag proteins were the main target (P=.007). CONCLUSIONS: Gag-specific responses dominate the CD4+ T cell response to HIV, whereas CD8+ T cell responses are broadly distributed, which indicates differential immunogenicity of these cells against HIV-1. The preferential targeting of Gag by CD8+ T cells is associated with enhanced control of viral load.     

Kinetics of the T-cell receptor CD4 and CD8 V beta repertoire in HIV-1 vertically infected infants early treated with HAART.

OBJECTIVES: To determine the kinetics and the relationship between the T-cell receptor V beta (TCRBV) complementary determining region 3 length, the CD4 T-cell count and HIV viral load changes in HIV-1 infected infants treated early with highly active antiretroviral therapy (HAART) during 1 year of follow-up. DESIGN: Two HIV-1 vertically infected infants, two HIV-1 vertically exposed uninfected and two healthy controls were analysed by spectratyping. Evaluation of viral load, CD4 naive and memory cell counts and a proliferation test were also carried out. METHODS: Twenty-six families and subfamilies of the TCR on CD4 and CD8 T cells were analyzed by spectratyping. Flow cytometric analysis on peripheral blood mononuclear cells for CD4CD45Ra, CD4CD45Ro, CD8CD38, proliferation tests and plasma viral load measurements were performed at baseline, 1, 6 and after 12 months of therapy. RESULTS: HAART induced a marked reduction of viral load in both HIV-1 infected infants and an increase to normal CD4 T-cell count in the symptomatic infant. At baseline the TCRBV family distribution in the majority of CD8 and a few of the CD4 T cells was highly perturbed, with several TCRBV families showing a monoclonal/oligoclonal distribution. During HAART a normalization of the TCR repertoire in both CD8 and CD4 subsets occurred. TCR repertoire normalization was associated with a good virological and immunological response. CONCLUSION: These results suggest that complete and early virus replication control as a result of early HAART leads to a marked reduction of T-cell oligoclonality and is an essential prerequisite to the development of a polyclonal immune response in HIV-1 infected infants.     

Trophoblasts are productively infected by CD4-independent isolate of HIV type 1.

Evidence for HIV-1 infection of trophoblasts is discordant. Utilizing highly purified full-term trophoblasts, we demonstrate that full-term trophoblasts express CXCR4 but are negative for CCR5 and CD4 cell surface proteins. Full-term trophoblasts were refractory to infection by HIV-1 IIIB and primary isolates of HIV-1. However, full-term trophoblasts could be infected by a CD4-independent, CXCR4-utilizing HIV-1 strain, as demonstrated by substantial p24 (5.5 ng/ml) levels and HIV-1 gag/pol DNA content (3050 copies/microg) 7 days postinfection. These data illustrate that trophoblasts express the essential host factors for productive HIV-1 infection and that the block to HIV-1 infection may be at the level of entry. In additional, our data suggest that CD4-independent mechanisms of infection may play a role in promoting in utero HIV-1 transmission.