Loss of cytomegalovirus-specific CD4+ T cell responses in human immunodeficiency virus type 1-infected patients with high CD4+ T cell counts and recurrent retinitis

Clinical histories are reported for 2 patients treated with highly active antiretroviral therapy (HAART) who experienced multiple relapses of cytomegalovirus (CMV) retinitis, despite suppression of human immunodeficiency virus type 1 (HIV-1) viremia and improvement in CD4+ T cell counts (to >400 cells/microL). CMV-specific CD4+ T cell immune reconstitution was measured directly, using cytokine flow cytometry, which revealed persistent deficits in CMV-specific CD4+ T cell responses in both patients. CMV-specific T cells constituted 0.14% and 0.05% of the total CD4+ T cell count in these patients, which is significantly lower than the percentages for 34 control subjects (0.6%-46%; CD4+ T cell count range, 7-1039 cells/microL; P=.019). Deficits in pathogen-specific immune responses may persist in some individuals, despite suppression of HIV-1 replication and substantial increases in circulating CD4+ T cells after HAART, and such deficits may be associated with significant morbidity from opportunistic infections.     

Clonal CD8+ T cell expansions in peripheral blood from human immunodeficiency virus type 1-infected children

The T cell receptor (TCR) repertoires of 24 human immunodeficiency virus (HIV) type 1-infected children were determined by flow cytometry in combination with sequencing of the highly variable TCR complementarity-determining region 3, permitting a quantitative and qualitative assessment of TCR repertoire. Expanded subsets of CD8(+) cells expressing a particular TCR beta-chain variable region were more commonly identified in HIV-1-infected children than in healthy control subjects (75% vs. 13.5%; P<.0001). Older age and lower percentage of CD4(+) cells were correlated with expansions. Oligoclonal populations occupied 71%-95% of each expanded subset, and predominant clones had high absolute counts. There was evidence of functional differentiation to CD28(-) effector cytotoxic T lymphocytes, and cells bearing identical TCRs were identified in both CD28(+) and CD28(-) cell populations. HIV-1 specificity was observed for expanded clones. Children with expansions were not more likely to have increased numbers of CD8(+) T cells, a finding consistent with the possibility that the CD8(+) TCR repertoire has limited diversity.     

CD4 down-regulation by nef alleles isolated from human immunodeficiency virus type 1-infected individuals.

PCR was used to clone isolates of the human immunodeficiency virus type 1 (HIV-1) nef gene directly from peripheral blood leukocytes of HIV-1-infected individuals. A transient expression system with human CEM T cells was used to assess the effect of nef on CD4 antigen expression on the cell surface. We show that CD4 down-regulation is a frequent property of primary HIV-1 nef alleles. Mutations in conserved amino acid motifs of Nef disrupted CD4 down-regulation. Our observations strongly suggest that CD4 down-regulation reflects a conserved function of nef, which is selected in vivo in human HIV-1 infection. Methodology described here provides quantitative assays to establish whether alterations in nef correlate with the dynamics of disease progression in human AIDS.     

Correlation between circulating stromal cell-derived factor 1 levels and CD4+ cell count in human immunodeficiency virus type 1-infected individuals.

Stromal cell-derived factor 1 (SDF-1) is the natural ligand that recognizes CXCR4, which also serves as a coreceptor for some strains of HIV-1. In this study, we explored SDF-1 blood levels among HIV-1-infected individuals exhibiting a wide range of CD4+ cell counts. Plasma or serum concentrations of SDF-1 protein were measured by ELISA in samples from 31 HIV-1-seronegative individuals and 79 HIV-1-infected subjects. Although SDF-1 protein levels were stable for months among seronegative individuals (mean intrasubject variation, 17%), the absolute values varied widely (0.28 to 106.5 ng/ml; mean, 25.6 ng/ml). In HIV-1-infected subjects, there was a direct correlation between SDF-1 level and CD4+ cell count. Subjects with fewer than 50 CD4+ cells per cubic microliter of blood had significantly lower mean SDF-1 levels (+/-SD) than did either HIV-1-infected subjects with higher CD4+ cell counts or uninfected controls: CD4+ cell count <50, mean SDF-1 level of 10.7+/-33.7, 50 < CD4+ cell count <200, mean SDF-1 level of 12.9+/-19.0, 200 < CD4+ cell count <500, mean SDF-1 level of 19.3+/-36.8; CD4+ cell count >500, mean SDF-1 level of 18.5+/-25.2; uninfected control mean SDF-1 level, 25.6+/-34.7. No significant change in SDF-1 level was detected after administration of antiretroviral therapy in nine subjects with advanced disease (mean intrasubject variation, 43%). Analysis of SDF-1 mRNA expression in lymph nodes from HIV-1-infected subjects at different disease stages revealed that the medullary cords contained stromal cells that express SDF-1 mRNA. This preliminary analysis suggests a possible link between lower SDF-1 levels and disease progression.     

CD8+ cytotoxic T lymphocyte responses to lytic proteins of human herpes virus 8 in human immunodeficiency virus type 1-infected and -uninfected individuals

T cell immunity to lytic proteins of herpesviruses is important in host control of infection. We have characterized the cytotoxic T lymphocyte (CTL) response to 5 human herpesvirus 8 (HHV-8) homologues of lytic proteins in HHV-8-seropositive individuals. HLA class I-restricted, CD8(+) CTL responses to >/=1 HHV-8 lytic protein were detected in all 14 HHV-8-seropositive study subjects tested, with or without human immunodeficiency virus type 1 (HIV-1) infection, but not in any of 5 HHV-8-seronegative individuals. Seven of these study subjects with both HHV-8 and HIV-1 infection had greater anti-CTL reactivity to glycoprotein H (open-reading frame 22) than did the 7 study subjects infected only with HHV-8. Moreover, there was a strong, inverse correlation between HIV-1 load and glycoprotein H-specific CTL lysis in the study subjects infected with both viruses. CTL reactivity to HHV-8 lytic proteins may be involved in host control of HHV-8-related diseases, such as Kaposi's sarcoma.     

Equal plasma viral loads predict a similar rate of CD4+ T cell decline in human immunodeficiency virus (HIV) type 1- and HIV-2-infected individuals from Senegal, West Africa

Human immunodeficiency virus (HIV) type 2 infection is characterized by slower disease progression to acquired immunodeficiency syndrome than results from HIV-1 infection. To better understand the biological factors underlying the different natural histories of infection with these 2 retroviruses, we examined the relationship between HIV RNA and DNA levels and the rate of CD4(+) T cell decline among 472 HIV-1- and 114 HIV-2-infected individuals from Senegal. The annual rate of CD4(+) T cell decline in the HIV-2 cohort was approximately one-fourth that seen in the HIV-1 cohort. However, when the analysis was adjusted for baseline plasma HIV RNA level, the rates of CD4(+) T cell decline per year for the HIV-1 and HIV-2 cohorts were similar (a rate increase of approximately 4% per year for each increase in viral load of 1 log(10) copies/mL). Therefore, plasma HIV load is predictive of the rate of CD4(+) T cell decline over time, and the correlation between viral load and the rate of decline appears to be similar among all HIV-infected individuals, regardless of whether they harbor HIV-1 or HIV-2.     

A tumor necrosis factor-alpha-inducible promoter variant of interferon-gamma accelerates CD4+ T cell depletion in human immunodeficiency virus-1-infected individuals

A polymorphism, -179G/T, in the promoter of the interferon (IFN)-gamma gene (IFNG) confers differential tumor necrosis factor-alpha (TNF-alpha) inducibility to the IFNG promoter. The rarer allele, -179T, but not -179G, is inducible by TNF-alpha. We investigated the effects of IFNG -179G/T on AIDS pathogenesis. In 298 African American human immunodeficiency virus (HIV)-1 seroconverters, the IFNG -179G/T genotype was associated with accelerated progression to CD4 <200 and AIDS-1993, a finding suggesting that IFNG -179T is a risk factor for AIDS progression, as measured by CD4 cell count. It is possible that increased IFN-gamma production induced by TNF-alpha when -179T is present causes CD4 cell depletion by apoptosis.     

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.     

A low level of CD4+CD28+ T cells is an independent predictor of high mortality in human immunodeficiency virus type 1-infected patients

This study investigated coexpression of CD28, CD45RA, and CD45RO on CD4(+) and CD8(+) cells in 107 human immunodeficiency virus (HIV) type 1-infected patients, who were followed-up prospectively and were not treated with highly active antiretroviral therapy, and 65 control subjects. The most important novel finding was that a 50% reduction in CD4(+)CD28(+) cells predicted increased mortality (relative hazards [HR], 1.6; 95% confidence interval [CI], 1.0-2.6; P=.04), even after adjusting for the CD4(+) cell counts, virus load, beta(2)-microglobulin and hemoglobin levels, and HIV disease stage. Patients with progressed HIV infection had decreased concentrations of all studied cell subsets. Concerning the proportions of cells, only CD4(+)CD28(+), CD4(+)CD45RA(+), and CD8(+)CD45RO(+) cells decreased with HIV progression. Low proportions of CD4(+)CD45RA(+), CD8(+)CD45RA(+), and CD8(+)CD45RO(+) cells predicted mortality only in univariate but not in multivariate Cox analyses. If our results are confirmed in other studies, coexpression of CD28 on CD4(+) cells may be a useful marker to evaluate HIV progression.     

Antibodies to CD4 in individuals infected with human immunodeficiency virus type 1.

The attachment of human immunodeficiency virus type 1 (HIV-1) to target cells is mediated by a specific interaction between the viral envelope glycoprotein (gp120) and the CD4 receptor. Here we report that approximately 10% of HIV-1-infected individuals produce antibodies that recognize the extracellular portion of the CD4 molecule. Carboxyl-terminal deletions of CD4 that do not affect HIV-1 gp120 binding eliminate recognition of CD4 by patient antisera. In contrast, mutations in the amino-terminal domain of CD4 that attenuate HIV-1 gp120 binding do not diminish CD4 recognition by patient antisera. These results suggest that HIV-1 infection can generate antibodies directed against a region of the viral receptor distinct from the virus-binding domain.     

Association between HIV Type 1-specific T cell responses and CD4+ T cell counts or CD4+:CD8+ T cell ratios in HIV Type 1 subtype B infection in China

CD4+ T cell counts and CD4+:CD8+ T cell ratios represent key determinants of HIV disease progression and infectivity. However, the relationship between the HIV-1-specific cytotoxic T lymphocyte (CTL) response and these determinants has not been elucidated for all HIV-1B and HIV-1C proteins. In the present study, virusspecific T cell responses to HIV-1B and HIV-1C proteins were analyzed with interferon gamma (IFN-gamma) enzyme- linked immunospot (ELISpot) assays using synthetic overlapping peptides corresponding to naturally occurring HIV-1B and HIV-1C consensus sequences. For Gag/Gag p24/Gag p17, a correlation between T cell responses and CD4+ T cell count in HIV-1 clade B and clade C was seen: elevated T cell response resulted in higher CD4+ T cell production. A statistically significant correlation between the Pol-specific T cell response and CD4+ T cell counts was also found in HIV-1 subtype C. For all HIV-1B and HIV-1C proteins, a correlation between the HIV-1-specific T cell response and CD4+:CD8+ T cell ratios was found for Tat and Pol proteins. CD4+ T cell counts in patients with Tat and/or Rev T cell response were higher than in patients without Tat and/or Rev T cell response. We suggest that this correlation within HIV-1B and HIV-1C Gag p24/Gag p17 responses makes the Gag p24/Gag p17 region a potential vaccine candidate and that HIV-1-specific CTL epitopes toward Pol are important in controlling HIV-1 infection; we emphasize that future vaccination strategies should include these early antigens, Tat and Rev.     

CD8(+) T cell activation in women coinfected with human immunodeficiency virus type 1 and hepatitis C virus

Immune activation is a hallmark of human immunodeficiency virus type 1 (HIV-1) infection and impacts innate and adaptive immunity. Individuals coinfected with HIV-1 and hepatitis C virus (HCV) may have increased immune activation early in HIV disease because of a high HCV antigen load in tissues such as the liver. We evaluated T cell markers of activation and maturation in women with or without HIV-1 infection, by HCV antibody and HCV RNA status. We found increased percentages of activated CD8(+) T cells (i.e., CD8(+)HLA-DR(+)38(+) cells and CD8(+)CD28(+)HLA-DR(+) cells) but not of CD4(+) T cells among women who tested positive for HIV-1, HCV antibody, and HCV RNA, compared with HIV-1-positive women who tested negative for HCV antibody. Because CD8(+) T cell activation is related to HIV-1 disease progression, these data may have implications for the medical management of patients coinfected with HIV-1 and HCV.     

Recovery of replication-competent virus from CD4 T cell reservoirs and change in coreceptor use in human immunodeficiency virus type 1-infected children responding to highly active antiretroviral therapy

Highly active antiretroviral therapy (HAART) suppresses plasma viremia in most patients with human immunodeficiency virus (HIV) infection. Prospective study of HIV-infected children (n=27) shows that, in 8 of 12 who responded to HAART (>/=0.5 log reduction in plasma HIV RNA), HAART restricted the number of coreceptors used by the predominant HIV isolate (mean number of coreceptors used at baseline was 4, vs. 1 coreceptor used at 6 months after treatment). This decrease was most striking in 6 of 8 children whose HIV coreceptor tropism changed from X4-tropic at baseline to R5-tropic. In 6 of 10 children tested, with plasma HIV RNA levels of <50 copies/mL, R5-tropic virus was isolated from CD4 T cell reservoirs. All the responding children had a significant increase in naive CD4 T cells (P<.05). These results show that persistent HIV T cell reservoirs are present in children and that HAART may influence the number and type of coreceptors used by the predominant virus isolate.     

Evaluation of initial CD4+ T cell counts in individuals with newly diagnosed human immunodeficiency virus infection,by sex and race,in urban settings

The CD4+ T cell count is an important determinant of disease stage and prognosis in human immunodeficiency virus (HIV)-infected individuals. This study evaluated the CD4+ T cell counts in individuals at the time of diagnosis of HIV infection at 4 community clinics in large urban settings with relatively high frequencies of HIV infection. Of 2223 individuals, 57% and 36% had CD4+ T cell counts < 350 and < 200 cells/mm(3), respectively, at the time of diagnosis. There were no clear differences by sex or race. Enhanced educational efforts regarding the importance of HIV testing for at-risk individuals across sex and race strata in community settings may be important for early identification of individuals with HIV infection. This in turn could impact efforts to reduce transmission, and it could impact the prognosis for patients who receive antiretroviral therapy.     

Killing of primary CD4+ T cells by non-syncytium-inducing macrophage-tropic human immunodeficiency virus type 1.

Understanding the mechanism by which human immunodeficiency virus type 1 (HIV-1) kills CD4+ T lymphocytes is important to the development of therapeutic and prophylactic strategies. Recent studies have indicated that, in some cases, progression to AIDS is associated with the appearance of syncytium-inducing, T cell line-tropic HIV-1 variants. Nevertheless, approximately 50% of subjects with AIDS harbor only non-syncytium-inducing, macrophage-tropic (NSI-M) variants of HIV-1. In most asymptomatic patients, NSI-M HIV-1 isolates are the predominant virus type found. We report here that cytopathicity of NSI-M HIV-1 for primary CD4+ T lymphocytes can be directly detected in vitro. The extent of CD4+ T-cell killing was not completely correlated with the rate of viral replication, suggesting that other characteristics of HIV-1 contribute to its cytopathicity. Our findings suggest that: (i) direct killing by NSI-M HIV-1 may contribute to CD4+ T-lymphocyte depletion in vivo, and (ii) the determinants of HIV-1 cytopathicity for CD4+ T lymphocytes and cell tropism or syncytia-forming ability are not necessarily tightly linked.     

Biphasic decay of latently infected CD4+ T cells in acute human immunodeficiency virus type 1 infection

Latent infection of resting CD4(+) T cells represents a major barrier to eradication of human immunodeficiency virus type 1 (HIV-1). The establishment and rate of decay of latent HIV-1 in resting CD(+) T cells from 9 acute seroconverters, 7 of whom began to receive highly active antiretroviral therapy (HAART) shortly after presentation, were studied. Before the initiation of therapy, these patients had very high frequencies of latently infected CD4(+) T cells, with a median frequency of 205 infectious units per million resting CD4(+) T cells. These values are > or =1 log higher than those seen in chronically infected patients who are not undergoing HAART. The number of latently infected cells declined dramatically after initiation of HAART but then tended to level off at a low but stable level. The biphasic decay of latent HIV in resting CD4(+) T cells in acute seroconverters supports current models of pre- and postintegration latency.