CXCR5~+CD8~+ T细胞在HIV感染中的免疫特征及其与疾病进展关系的研究

目的探讨HIV感染者外周血CXCR5~+CD8~+T细胞的频率、功能变化及其与病情进展的相关性。方法收集40例HIV感染者和15例健康对照者,采用流式细胞分析术检测其外周血CXCR5~+CD8~+T细胞频率及IFN-γ和IL-10表达,并分析其与血浆HIV载量和外周血CD4~+T细胞计数的相关性。结果与健康对照组相比,HIV感染组外周血CXCR5~+CD8~+T细胞频率上调(P0.05),且与外周血CD4~+T细胞计数呈弱正相关(r=0.349,P=0.027),与血浆HIV载量呈弱负相关(r=-0.377,P=0.040);HIV感染者外周血CXCR5~+CD8~+T细胞IFN-γ表达与血浆HIV载量呈负相关(r=-0.514,P=0.002);而CXCR5~+CD8~+T细胞IL-10的表达在HIV感染者中明显上调(P0.05),与外周血CD4~+T细胞计数呈弱负相关(r=-0.317,P=0.046),与血浆HIV载量呈正相关(r=0.670,P=0.002)。结论 HIV感染者外周血CXCR5~+CD8~+T细胞频率功能变化与疾病进展密切相关。     

过敏性哮喘患者外周血CD4~+T细胞表达CD39和CD73水平变化及其临床意义

目的:初步探讨CD4+T细胞表达的腺苷CD39和CD73在过敏性哮喘患者外周血中的水平变化及与叉头蛋白3(FoxP3)、GATA结合蛋白3(GATA3)和维A酸相关孤儿受体(ROR)-γt mRNA相关性。方法:选择54例对屋尘螨过敏的慢性持续期哮喘患者[间歇状态和轻度持续哮喘组(间歇-轻度组)29例,中重度组25例]和45名健康志愿者,通过荧光实时定量PCR方法检测并比较研究对象外周血CD4+T细胞中CD39、CD73、FoxP3、GATA3和ROR-γt mRNA水平。结果:CD39 mRNA水平正常对照组明显高于间歇-轻度组(P=0.000),间歇-轻度组明显高于中重度组(P=0.001)。CD73 mRNA水平正常对照组明显高于间歇-轻度组(P=0.001),哮喘亚组间差异无统计学意义(P=0.126)。哮喘组CD4+T细胞表达的CD39 mRNA与FoxP3 mRNA水平呈显著正相关性(r=0.607,P=0.000),与GATA3 mRNA水平呈显著负相关性(r=-0.505,P=0.000),与ROR-γt mRNA无显著相关性(r=-0.287,P=0.054)。哮喘组CD4+T细胞表达的CD73 mRNA与FoxP3和ROR-γt mRNA水平无显著相关性(r=0.110,P=0.450;r=-0.227,P=0.138),与GATA3mRNA水平呈显著负相关性(r=-0.286,P=0.040)。结论:CD4+T细胞表达的CD39和CD73在过敏性哮喘免疫反应过程中起到重要作用。     

HIV-1感染者外周血增加的CD71~+红系细胞特点及临床意义

目的探讨HIV-1感染者外周血CD71~+红系细胞的特点及其与疾病进展的关系。方法通过流式细胞术检测HIV-1感染者外周血CD71~+红系细胞,分析其与HIV-1 RNA、CD4细胞计数、CD4/CD8细胞比值的相关性。结果入组10例健康对照(HCs)和49例HIV-1感染者,后者包括28例未接受过ART者(TNs)和21例免疫重建成功患者(CRs)。与HCs组(平均值0.69%)相比,TNs组患者CD71~+红系细胞频率明显升高(平均值2.79%)。CRs组患者经ART后,CD71~+红系细胞频率降低(平均值1.18%),但是未恢复到正常水平。TNs组患者CD71~+红系细胞频率与病毒载量呈显著正相关(r=0.503 4,P=0.006 3),与CD4/CD8细胞比值呈明显负相关(r=-0.464 0,P=0.012 9)。与HCs(平均值158 g/L)相比,TNs组患者外周血血红蛋白含量明显降低(平均值149 g/L);CRs组患者经ART后,血红蛋白含量升高(平均值154 g/L),并且恢复到正常水平;TNs组患者CD71~+红系细胞频率与血红蛋白含量呈明显负相关(r=-0.462 5,P=0.013 2)。与HCs(平均值53.84%)相比,TNs组患者CD71~+红系细胞活性氧(ROS)表达水平明显升高(平均值66.64%);CRs组患者经ART后,CD71~+红系细胞表达ROS显著降低(平均值43.82%),并且降至正常水平。结论HIV-1感染导致外周血CD71~+红系细胞频率升高,并且与疾病进展和血红蛋白的降低密切相关。     

3型天然淋巴细胞在HIV-1慢性感染中的免疫特征及其与疾病进展的关系研究

目的探讨HIV-1慢性感染过程中,外周血3型天然淋巴细胞(group 3 innate lymphoid cells,ILC3s)的频率变化及其与疾病进展的关系。方法募集48例HIV-1慢性感染者和17例健康对照,留取外周血并分离单个核细胞,进行流式细胞检测ILC3s频率,同时分析ILC3s频率与患者外周血CD4+T淋巴细胞计数和病毒载量的相关性。结果与健康对照比较,HIV-1感染者外周血总的ILC3s频率显著下降(P<0.001);其中尤以NCR-ILC3s下降更为显著(P<0.001)。进一步分析显示:HIV-1感染者外周血ILC3s频率与CD4+T淋巴细胞计数呈弱正相关(r=0.461,P=0.001),而与血浆病毒载量呈弱负相关(r=-0.399,P=0.005)。结论 HIV-1慢性感染者外周ILC3s显著减少,并与疾病进展密切相关。该研究为阐明HIV-1慢性感染致病机制提供了新的解释。     

外周血非编码微小RNA与HIV-1感染者病情进展的关系研究

目的 检测HIV-1感染者外周血微小RNA-155(miR-155)水平,并研究其与疾病进展的关系.方法 收集121例接受抗病毒治疗(HAART) HIV-1感染者和43例未接受HAART的感染者,实时荧光定量PCR法测定miR-155表达水平,流式细胞术检测CD3+CD4+和CD3+CD8+T细胞数及其活化细胞的比例(CD4+CD38+％和CD8+CD38+％). 结果 HIV-1感染者特别是治疗无效组外周血单核细胞(PBMC),CD4+和CD8+T细胞中的miR-155水平显著升高(F=11.317,P＜0.01).治疗无效者和未HAART治疗者CD38+的CD4+和CD8+T细胞比例高于正常对照和治疗有效组(F=5.813,P＜0.05),miR-155表达水平与T细胞免疫活化正相关(r=0.581,P=0.037;r=0.732,P=0.001).结论 本研究提示HIV-1感染者外周血miR-155表达水平显著升高,并与T细胞免疫活化正相关,可以作为HIV-1免疫应答的指标之一.     

HIV-1感染者血浆丙酮酸对CD8+ T细胞功能的影响及临床意义

目的?探讨HIV-1感染者血浆丙酮酸对CD8+ T细胞功能的影响与疾病进展的关系。方法?入组11例健康对照（healthy controls, HCs）与55例接受长期抗逆转录病毒治疗的HIV-1感染者。通过液相色谱质谱联用法检测HCs与HIV-1感染者血浆丙酮酸水平，比较丙酮酸不同浓度组在HIV-1病毒库数量、CD8+ T细胞亚群比例、CD8+ T细胞功能间的差异。结果?与HCs（中位数416.71 ng/ml）相比HIV-1感染者（中位数539.16 ng/ml）血浆丙酮酸水平显著升高（P=0.0189）。与血浆低丙酮酸浓度组（低浓度组）相比，高丙酮酸浓度组（高浓度组）HIV-1细胞相关未剪接核糖核酸（HIV-1 cell associated un-spliced ribonucleic acid, HIV-1 CA RNA）、HIV-1 CA RNA/HIV-1 DNA的比值均显著升高；CD8+ T中央记忆T细胞（central memory T cells, TCM）比例显著升高；CD8+ T细胞表达TNF-α、IL-2、IFN-γ、CCL5的比例均降低，而表达CCL4的比例升高。血浆丙酮酸水平与CD8+ T细胞表达TNF-α（r=-0.3584，P=0.0106）、IL-2（r=-0.4975，P=0.0002）、IFN-γ（r=-0.4101，P=0.0031）、CCL5（r=-0.5655，P＜0.0001）的比例呈负相关，与CCL4（r=0.4711，P=0.0014）的比例呈正相关。结论 长期抗病毒治疗的HIV-1感染者血浆丙酮酸水平升高，且丙酮酸水平与HIV-1病毒库的活跃程度以及CD8+ T细胞功能紊乱相关。     

正常T细胞分泌激活因子基因多态性与HIV-1感染者病毒载量、CD+4细胞计数和CD+4/CD+8比值的关系

目的分析正常T细胞分泌激活因子(RANTES)启动子和内含子等位基因,对艾滋病病毒1型(HIV-1)感染者外周血CD+4细胞计数、CD+4/CD+8比值和病毒载量的关系,以期探讨RANTES单核苷酸多态性(SNP)和艾滋病(AIDS)发病的关系.方法用流式细胞仪和real time法对40例汉族HIV-1感染者测定外周血CD+4、CD+8细胞计数和病毒载量,应用PCR-RFLP法进行基因分型.结果对RANTES-403、-28和In1.1三个位点等位基因与外周血CD+4T淋巴细胞计数、CD+4/CD+8+比值和病毒载量的关系的分析表明,具有RANTESIn1.1 C/C和T/C基因型的感染者,与较高的病毒载量、较低的C+4T细胞计数和C+4/CD+8比值有关.In1.1 T/T与T/C、C/C基因型的log10病毒载量的差异有非常显著的统计学意义(P＜0.01),但是不同基因型之间CD+4T淋巴细胞计数和CD+4/CD+8细胞比值则无显著性差异.log10病毒载量和CD+4T淋巴细胞计数(r=-0.447,P＜0.01)、CD+4/CD+8比值(r=-0.369,P＜0.05)有显著的负相关关系.结论所研究人群中,具有RANTES In1.1C的基因型者,与较高的病毒载量、较低的CD+4T细胞计数和CD+4/CD8+比值有关,它们是反映AIDS进程的主要指标,可能加速AIDS发病进程;而RANTES-403和-28等位基因的影响则处于相对次要的作用.     

慢性乙型肝炎患者外周血CD8~+T细胞CD95表达的研究

目的检测慢性乙型肝炎患者外周血CD8+T细胞CD95分子的表达水平,了解CD95分子表达与炎症进展的关系。方法采集37例慢性乙型肝炎患者及健康对照者外周血,分离外周血单个核细胞(PBMCs),用流式细胞术检测外周血CD8+T细胞CD95分子的表达情况。结果高病毒载量组和低病毒载量组CD8+T细胞CD95的表达均显著高于健康对照组(P0.05);CD95的表达及CD8+T细胞频率之间存在负相关关系(r=-0.3486)。结论慢性乙型肝炎患者CD95的高表达可能促进了CD8+T细胞的凋亡,使CD8+T细胞的抗病毒作用减弱,可能与HBV持续感染、慢性乙型肝炎的形成机制有关。     

抗病毒治疗HIV-1感染者外周血CD39~+ NK细胞的表达特点

目的通过分析接受长期抗病毒治疗(ART)的1型艾滋病病毒(HIV-1)感染者体内CD39~+NK细胞的频率和表型特征,探索其与主要临床指标的关系及临床意义。方法本研究入组10例健康对照(HCs)和28例长期接受ART的HIV-1感染者。利用流式细胞术检测NK细胞亚群分布以及NK细胞上CD39的表达情况,分析CD39+NK细胞亚群比例与CD4、CD8~+T淋巴细胞(简称CD4、CD8细胞)计数、以及CD4/CD8细胞比值的相关性。结果 28例长期接受ART的HIV-1感染者中,18例免疫重建成功患者(CRs)和10例免疫重建失败患者(INRs)。相较于HCs和CRs组,INRs组CD56dim亚群比例明显下降(平均值94.75%vs.82.65%,P 0.01;平均值93.20%vs.82.65%,P 0.001);INRs组CD39~+NK细胞的频率明显高于CRs组(平均值21.45%vs.7.79%,P 0.05)和HCs组(平均值21.45%vs.4.115%,P 0.001);长期接受ART的HIV-1感染者CD39+NK细胞占比与其CD4/CD8细胞比值呈负相关(r=-0.392 4,P=0.038 9)。结论免疫重建失败患者外周血中CD39+NK细胞表达频率明显高于免疫重建成功患者,HIV-1慢性感染者外周血CD39~+NK细胞表达增加伴随着CD4/CD8细胞比值的降低。     

HIV-1急性期感染者肠道归巢CD4~+T淋巴细胞的变化特点

目的分析Ⅰ型艾滋病病毒(HIV-1)急性期感染者肠道归巢CD4~+T淋巴细胞(简称CD4细胞)的变化特点及在HIV-1致病机制中的作用。方法共纳入26例HIV-1急性期感染者、31例HIV-1慢性期感染者和20例健康对照者。采用流式细胞仪检测三组样本的肠道归巢CD4细胞的比例和数量,并分析HIV-1急性期感染者肠道归巢CD4细胞与CD4细胞之间的相关性。结果与健康对照者相比,HIV-1急性期感染者肠道归巢CD4细胞的比例(平均值13.5%vs 11.0%,P0.05)和数量(平均值88.1vs 61.9,P0.01)均显著减少。HIV-1慢性期感染者肠道归巢CD4细胞的比例(平均值11.0%vs 8.1%,P0.01)和数量(平均值61.9vs 11.9,P0.000 1)均显著低于HIV-1急性期感染者。HIV-1急性期感染者肠道归巢CD4细胞的数量与外周血CD4细胞(r=0.53,P=0.006)和CD4/CD8细胞比例(r=0.51,P=0.009)呈显著正相关,与血浆中HIV-1病毒载量(r=-0.70,P=0.000 6)和机体T细胞免疫活化水平(r=-0.57,P=0.003)呈显著负相关。结论肠道归巢CD4细胞的丢失可能在HIV-1急性期感染的致病机制中起作用。     

Relationship of frequency of CD4+CD25+Foxp3+ regulatory T cells with disease progression in antiretroviral-naive HIV-1 infected Chinese

Forty-five antiretroviral-naive HIV-1 infected patients and 14 healthy controls in North China were enrolled in this study. The frequency of CD4+CD25+Foxp3+ regulatory T cells (Tregs) and levels of expression of CD95, HLA-DR and CD38 in T cells were detected by flow cytometry. We found that the frequency of Tregs was higher in AIDS patients than in asymptomatic HIV-1 infected patients (P=0.004). The frequency of Tregs was significantly correlated with absolute CD4 count, viral load, CD4+CD95+ T cells and CD8+CD95+ T cells (P<0.05). The relationship between the frequency of Tregs and immune activation was not found in HIV-infected patients. We concluded that the frequency of Tregs in HIV-infected Chinese patients was significantly correlated with disease progression.     

Selective stimulation of CD4+ versus CD8+ T-cell subsets in symptomatic and asymptomatic HIV-1-infected individuals.

To analyze the proliferative capacity of CD4+ or CD8+ T-cell subsets of individuals infected with human immunodeficiency virus type 1 (HIV-1) and to optimize the in vitro conditions for virus replication, CD4+ or CD8+ cells of HIV-1-infected patients were selectively activated inside the whole peripheral blood mononuclear cell (PMNC) population by dual antibody stimulation. To do so PMNC of HIV-1-infected individuals were stimulated with the per se nonmitogenic anti-CD3 antibody fragment BMA030 F(ab)2 crosslinked through goat antimouse antibodies with an anti-CD4 or an anti-CD8 antibody, which lead to selective proliferation of either the CD4+ or the CD8+ T-cell subset. In the presence of monocyte supernatant and recombinant interleukin-2 (rIL2) CD4+ cells of HIV-1 patients responded normally upon such stimulation as their proliferation correlated (r = 0.9) to the percentage CD4+ cells present in the PMNC population. Selective stimulation and proliferation of CD8+ cells could, however, only partially be elicited by dual antibody stimulation, even in the presence of rIL-2 and monocyte supernatant. Their proliferative response did not correspond (r = 0.1) to the percentage CD8+ cells present in the PMNC culture. A positive correlation (r = 0.7) was detected only between percentage CD8+ HLA-DR- cells and proliferation. This confirmed previous studies showing that the defective in vitro proliferative response of peripheral blood lymphocytes of HIV-infected individuals to mitogens, which is usually interpreted being due to a CD4 cell defect, is actually due to a failure of CD8+DR+ cells to proliferate.(ABSTRACT TRUNCATED AT 250 WORDS)     

HIV／AIDS患者血浆病毒载量及外周血T淋巴细胞亚群的变化

目的：观察国内HIV／AIDS患者血浆病毒载量和外周血CD4^ 、CD8^ T淋巴细胞的变化，探讨这些变化的临床意义。方法：选择未经抗病毒治疗的HIV／AIDS患者124例，用bDNA法检测血浆病毒载量，并用流式细胞仪检测外周血CD4^ 、CD8^ T淋巴细胞。结果：AIDS患者的血浆病毒载量明显高于HIV感染者，血浆病毒载量与CD4^ 细胞计数呈显著负相关，但其最高峰位于CD4^ 细胞计数100／μl处，然后随着CD4^ 细胞计数的下降而减少。CD4^ T细胞计数为AIDS组＜HIV组＜正常对照组：HIV感染者的CD8^ T细胞计数显著高于正常组和AIDS组，而AIDS患者CD8^ T细胞数则随着CD4^ T细胞减少而下降。结论：血浆病毒载量随着疾病进展而显著升高，但在疾病晚期则有所降低。外周血CD4^ T细胞计数随着疾病的进展而进行性减少；CD8^ T细胞计数在感染早期显著升高，进入晚期则减少。在评价HIV感染者和AIDS患者病情时，应结合病毒载量、CD4^ 、CD8^ T细胞计数综合分析。     

Relationship of CD4+CD25+ regulatory T cells to immune status in HIV-infected patients

OBJECTIVE: To determine whether the frequencies of CD4+CD25+ regulatory T cells (T Reg) were related to immune status in HIV-infected patients. METHODS: Peripheral blood CD4 T-cell populations were examined for T-helper 1 cells (Th1), T-helper 2 cells (Th2), and T Reg by intracellular staining for interferon (IFN)-gamma and interleukin (IL)-4, and surface staining for CD25, respectively. The immunoregulatory properties of T Reg were assessed by measurement of the inhibitory effects of isolated CD4+CD25+ T Reg on CD4+CD25- T-cell proliferation. RESULTS: Isolated CD4+CD25+ T Reg from both HIV-infected patients and healthy controls strongly expressed CD45RO, HLA-DR, and FoxP3. HIV-infected patients with detectable plasma HIV-1 RNA showed a statistically significant increase in CD4+CD25high T Reg frequencies (P < 0.05) compared to healthy controls, with T Reg frequency inversely proportional to CD4 T-cell count (P < 0.01). However, in HIV-infected patients with undetectable plasma HIV-1 RNA, CD4+CD25high T Reg frequencies were not increased and were not related to CD4 T-cell counts. In both HIV-infected patient groups, T Reg frequency was inversely related to Th1 frequency (detectable HIV-1 RNA: P < 0.05; undetectable: P < 0.001), but positively related to Th2 frequency (detectable HIV-1 RNA: P < 0.01; undetectable: P < 0.001). T Reg activity was lower in patients with detectable plasma HIV-1 RNA than in patients with undetectable plasma HIV-1 RNA. CONCLUSIONS: Increased T Reg frequencies in peripheral blood were related to low peripheral blood CD4 T-cell counts and polarization toward Th2 immune responses in HIV-infected patients.     

Human immunodeficiency virus DNA is present in a high percentage of CD4+ lymphocytes of seropositive individuals.

Human immunodeficiency virus type 1 (HIV-1) infects predominantly CD4+ cells in human peripheral blood and infection is associated with CD4+ lymphocyte dysfunction in patients with AIDS. To determine the frequency of HIV-1 infection in CD4+ lymphocytes in vivo, peripheral blood CD4+ lymphocytes were isolated by fluorescence-activated cell sorting from HIV-1-infected persons with clinical disease ranging from asymptomatic to AIDS. Using standard and booster polymerase chain reaction analyses, study patients with AIDS and AIDS-related complex (ARC) were found to harbor the HIV-1 genome in at least 10% of CD4+ lymphocytes, and approximately 10-fold less infected cells were found in those with asymptomatic infection. In addition, the peripheral blood mononuclear cells from patients with ARC frequently contained a higher absolute number of HIV-1-infected CD4+ lymphocytes than those with AIDS or asymptomatic infection. It is likely that this high level of infection of CD4+ lymphocytes is the primary cause for the progressive immunologic deficiency observed in patients infected with HIV-1.     

Relationship between antibody-dependent cellular cytotoxicity, plasma HIV type 1 RNA, and CD4+ lymphocyte count

To explore the role of antibody-dependent cellular cytotoxicity (ADCC) in controlling HIV-1 infection, ADCC was compared with plasma RNA and CD4+ cell count in 40 patients not receiving antiretroviral therapy and in seven patients after the initiation of treatment. Among untreated patients, ADCC effector cell function of peripheral blood mononuclear cells, measured by (51)Cr release assay, correlated inversely with viral load (R = -0.42, p = 0.007) and directly with CD4+ cell count (R = 0.52, p = 0.001). On the other hand, HIV-1-specific ADCC antibody level correlated directly with viral load, but only among patients with high CD4+ cell counts. Therapy-induced changes in ADCC effector cell function correlated strongly with changes in CD4+ cell count (R = 0.86, p = 0.014), whereas there was no consistent pattern of change in ADCC antibody with therapy. In a novel assay, ADCC reduced virus yield from CD4+ lymphocytes infected with a primary HIV isolate. ADCC may contribute to control of viremia, and CD4+ lymphocytes likely play a role in ADCC effector and antibody functions.     

SDF-1alpha is a potent inducer of HIV-1-Specific CD8+ T-cell chemotaxis, but migration of CD8+ T cells is impaired at high viral loads

Multiple impairments in HIV-1-specific cytotoxic T cells (CTL) have been reported, but derangements in HIV-1-specific CD8+ T-cell chemotaxis have not been described previously. We assessed migration to SDF-1alpha (stromal cell-derived factor 1-alpha) and CX3CL1 in vitro and expression of cognate receptors, CXCR4 and CX3CR1, by flow cytometry in peripheral blood and lymph node CD8+ T cells from HIV-1-seropositive and -seronegative individuals. Compared with seronegative individuals, percentages of CXCR4+CD8+ T cells were reduced (median, 26% versus 74%, p < 0.001) and percentages of CX3CR1+CD8+ T cells were increased (median, 33% versus 15%, p = 0.03) in seropositive individuals. Robust migration of peripheral blood mononuclear cell (PBMC) CD8+ T cells to SDF-1alpha (1 alphag/ml) was observed in both HIV-1-seropositive (median chemotactic index [CI] 4.9) and -seronegative (median CI 2.8) subjects (p = 0.46). CI to SDF-1alpha was not significantly related to percentage of CXCR4+CD8+ T cells or density of CXCR4, but correlated inversely with plasma HIV-1 RNA concentration (r = -0.82, p = 0.03). Little chemotaxis was observed in response to CX3CL1 and it was unrelated to CX3CR1 expression. Lymph node CD8+ T-cell chemotaxis to SDF-1alpha and CX3CL1 in four subjects demonstrated the same patterns observed in PBMC. HIV-1-specific tetramer-staining CD8+ T cells exhibited chemotaxis of similar magnitude as PBMC CD8+ T cells in a subset of subjects. These data suggest that SDF-1alpha is a potent chemoattractant for HIV-1-specific CTL, but that impairments in migration of HIV-1-specific CTL may exist at high viral loads. Improved understanding of the determinants of CTL localization may provide insight into novel therapies to enhance delivery of CTL to sites of HIV-1 replication.     

Relationship between the size of the human immunodeficiency virus type 1 (HIV-1) reservoir in peripheral blood CD4+ T cells and CD4+:CD8+ T cell ratios in aviremic HIV-1-infected individuals receiving long-term highly active antiretroviral therapy

It has been demonstrated that human immunodeficiency virus type 1 (HIV-1) replication persists in most infected individuals receiving highly active antiretroviral therapy (HAART). However, studies addressing the relationship between low levels of ongoing viral replication and immunologic parameters, such as the CD4+:CD8+ T cell ratio, in such individuals have been lacking. Here, a statistically significant inverse correlation is shown between the frequency of CD4+ T cells carrying HIV-1 proviral DNA and the CD4+:CD8+ T cell ratio in infected individuals receiving HAART and in whom plasma viremia had been suppressed below the limit of detection for prolonged periods of time. No correlation was found between the frequency of HIV-1-specific cytotoxic CD8+ T lymphocytes (CTLs) and the CD4+:CD8+ T cell ratios in those individuals. These data suggest that persistent, low-level, ongoing viral replication, although not sufficient to maintain HIV-1-specific CTL responses, may explain, in part, why normalization of the CD4+:CD8+ T cell ratio is not achieved in some infected individuals successfully treated with HAART.