Poor predictive value of cytomegalovirus (CMV)-specific T cell assays for the development of CMV retinitis in patients with AIDS

BACKGROUND

We examined the potential clinical utility of using a cytomegalovirus (CMV)-specific T cell immunoassay to determine the risk of developing new-onset CMV retinitis (CMVR) in patients with acquired immunodeficiency syndrome (AIDS).

METHODS

CMV-specific T cell assays were performed by multiparameter flow cytometry using stored peripheral blood mononuclear cells that had been obtained in an observational study 2-6 months before new-onset CMVR was diagnosed in case patients (at a study visit during which a dilated ophthalmologic examination revealed no evidence of CMVR) and at the same study visit in control subjects (matched by absolute CD4(+) T cell count at entry) who did not subsequently develop retinitis during 1-6 years of study follow-up.

RESULTS

There were no significant differences in CMV-specific CD4(+) or CD8(+) T cell interferon-gamma or interleukin-2 expression in peripheral blood mononuclear cells from case patients and control subjects. Although there were trends toward lower percentages and absolute numbers of CMV-specific, cytokine-expressing CD8(+) T cells with a "late memory" phenotype (CD27(-)CD28(-)) as well as with an "early memory" phenotype (CD27(+)CD28(+)CD45RA(+)) in case patients than in control subjects, these differences were not statistically significant.

CONCLUSIONS

Many studies have reported that CMV-specific CD4(+) and CD8(+) T cell responses distinguish patients with active CMVR (i.e., who lack CMV-protective immunity) from those with inactive CMVR after immune restoration by antiretroviral treatment (i.e., who have CMV-protective immunity). However, the multiple CMV-specific immune responses we measured do not appear to have clinical utility for predicting the risk for patients with AIDS of developing new-onset CMVR with sufficient accuracy to be used in guiding therapeutic management.

Increased carotid intima-media thickness in HIV patients is associated with increased cytomegalovirus-specific T-cell responses

OBJECTIVES

HIV-infected subjects are at increased risk for myocardial infarction. The mechanism of this increased risk remains unclear. Since cytomegalovirus (CMV) infection has been associated with accelerated atherosclerosis in the transplant population and immune responses against CMV may be altered by HIV disease, we hypothesized that enhanced T-cell responses against CMV would be associated with increased atherosclerosis in subjects with HIV.

METHODS

We measured high-sensitivity C-reactive protein (hs-CRP), T-cell activation, CMV-specific T-cell responses, and carotid artery intima-media thickness (IMT) in 93 HIV-infected subjects and in 37 uninfected controls.

RESULTS

The mean age of the HIV-infected subjects was 48 years and 85 (91%) were male. The median carotid IMT was higher in the HIV-infected group compared to the uninfected group (0.95 mm versus 0.68 mm, P < 0.001). This difference remained significant after controlling for all traditional risk factors. Compared to HIV-negative controls, HIV-infected subjects had higher median levels of hs-CRP (P = 0.05), higher levels of CD4 and CD8 T-cell activation (P < 0.0001) and higher CMV-specific interferon-gamma CD8 T-cell responses (P < 0.0001). CMV-specific T-cell responses, but not hs-CRP and T-cell activation, were independently associated with higher carotid IMT (P = 0.001).

CONCLUSIONS

HIV-infected subjects had thicker carotid IMT compared to controls. While HIV patients also had higher T-cell activation, hs-CRP levels, and CMV-specific T-cell responses, only CMV-specific T-cell responses were independently associated with IMT. Accelerated atherosclerosis in HIV patients may be mediated by heightened CMV-induced immune responses.

Protective immunity to cytomegalovirus (CMV) retinitis in AIDS is associated with CMV-specific T cells that express interferon- gamma and interleukin-2 and have a CD8+ cell early maturational phenotype

To determine potential correlates of immune recovery from AIDS-related cytomegalovirus retinitis (CMVR), multiparameter flow cytometry was used to characterize CMV-specific T cells from subjects with CMVR. Individuals with active retinitis were compared with those who had been clinically immunorestored by antiretroviral therapy and had > or =2 years of ophthalmologic follow-up without anti-CMV therapy or retinitis reactivation or progression. In comparison with patients with active retinitis, immunorestored patients had higher circulating CD4(+) and CD8(+) T cells expressing interleukin-2 and interferon- gamma in response to combined CMV pp65 and IE1 peptide pool stimulation. CD4(+) T cell responses were predominantly to pp65, whereas CD8(+) T cell responses were predominantly to IE. Immunorestored patients, compared with patients with active retinitis, had increased levels of circulating CMV-specific CD8(+) T cells with "early" (CD27(+)CD28(+)CD45RA(+), CD27(+)CD28(+)CD45RA(-)) and "intermediate" (CD27(-)CD28(+)CD45RA(-)) phenotypes. Recovery from AIDS-related CMVR after the initiation of antiretroviral therapy may be mediated by CMV-specific CD4(+) and CD8(+) T cells capable of promoting antigen-specific CD8(+) T cell proliferation.

Safety and immunogenicity of Towne cytomegalovirus vaccine with or without adjuvant recombinant interleukin-12

The Towne, human cytomegalovirus (CMV) vaccine is safe and immunogenic but has not prevented infection at doses tested to date. We administered 3000 pfu Towne CMV vaccine, with or without adjuvant recombinant interleukin-12 (rhIL-12), to CMV-seronegative healthy volunteers and then measured CMV gB-specific IgG titers and CMV-specific CD4+ and CD8+ T cell proliferation and IFNgamma expression after stimulation with whole viral lysate and immunodominant peptide CMV antigens. Adjuvant rhIL-12 at doses up to 2 microg were well-tolerated and associated with (1) dose-related increases in peak anti-CMV gB IgG titers (though not in sustained titers), (2) dose-related increases in the weak CMV viral lysate-specific CD4+ T cell proliferation responses induced by vaccine alone after 360 days of follow-up, and (3) decreases in the very robust CMV IE-specific peak CD4+ T cell and Day 360 CD8+ T cell proliferation responses induced by the vaccine alone. Also, qualitative CD8+ T cell IFNgamma responses to stimulation with the immunodominant CMV antigen, pp65, tended to occur more frequently in vaccinees who received 0.5-2.0 microg rhIL-12 compared to lower dose or no rhIL-12. Thus, adjuvant IL-12 may be a promising strategy for improving antibody and T cell immune responses to a CMV vaccine.

Antigen-specific T cell responses induced by Towne cytomegalovirus (CMV) vaccine in CMV-seronegative vaccine recipients

BACKGROUND

Towne cytomegalovirus (CMV) vaccine is safe and immunogenic, though its protective efficacy has yet to be optimized.

OBJECTIVE

Describe antigen-specific T cell responses to Towne vaccination.

STUDY DESIGN

3000 pfu Towne CMV vaccine were given to 12 CMV-seronegative volunteers. CMV-specific CD4+ and CD8+ T cell proliferation and IFNgamma expression were measured by flow cytometry after stimulation with CMV lysate or peptides.

RESULTS

All vaccinees developed CD4+ and CD8+ T cell proliferation and CD4+ T cell IFNgamma responses to multiple CMV antigens, but their CD8+ T cells had low or undetectable IFNgamma responses to pp65 peptide pool. The seven HLA-A2+ subjects had higher CD8+ T cell proliferation and IFNgamma responses to IE than pp65, and two never developed CD8+ T cell IFNgamma responses to pp65. Peak CD4+ T cell IFNgamma responses to CMV lysate were lower than values observed in natural CMV seropositives. Initial CD4+ and CD8+ T cell responses to lysate and pp65 waned after 12 months to levels that were lower than those in healthy CMV seropositives, while vaccinees' CD8+ T cell responses to IE were robust and prolonged.

CONCLUSION

Correlating CMV antigen-specific T cell responses with clinical protective efficacy may facilitate future CMV vaccine development.

Standardization of cytokine flow cytometry assays

BACKGROUND

Cytokine flow cytometry (CFC) or intracellular cytokine staining (ICS) can quantitate antigen-specific T cell responses in settings such as experimental vaccination. Standardization of ICS among laboratories performing vaccine studies would provide a common platform by which to compare the immunogenicity of different vaccine candidates across multiple international organizations conducting clinical trials. As such, a study was carried out among several laboratories involved in HIV clinical trials, to define the inter-lab precision of ICS using various sample types, and using a common protocol for each experiment (see additional files online).

RESULTS

Three sample types (activated, fixed, and frozen whole blood; fresh whole blood; and cryopreserved PBMC) were shipped to various sites, where ICS assays using cytomegalovirus (CMV) pp65 peptide mix or control antigens were performed in parallel in 96-well plates. For one experiment, antigens and antibody cocktails were lyophilised into 96-well plates to simplify and standardize the assay setup. Results ((CD4+)cytokine+ cells and (CD8+)cytokine+ cells) were determined by each site. Raw data were also sent to a central site for batch analysis with a dynamic gating template. Mean inter-laboratory coefficient of variation (C.V.) ranged from 17-44% depending upon the sample type and analysis method. Cryopreserved peripheral blood mononuclear cells (PBMC) yielded lower inter-lab C.V.'s than whole blood. Centralized analysis (using a dynamic gating template) reduced the inter-lab C.V. by 5-20%, depending upon the experiment. The inter-lab C.V. was lowest (18-24%) for samples with a mean of > 0.5% IFNgamma + T cells, and highest (57-82%) for samples with a mean of < 0.1% IFNgamma + cells.

CONCLUSION

ICS assays can be performed by multiple laboratories using a common protocol with good inter-laboratory precision, which improves as the frequency of responding cells increases. Cryopreserved PBMC may yield slightly more consistent results than shipped whole blood. Analysis, particularly gating, is a significant source of variability, and can be reduced by centralized analysis and/or use of a standardized dynamic gating template. Use of pre-aliquoted lyophilized reagents for stimulation and staining can provide further standardization to these assays.

Strong Cell‐Mediated Immune Responses Are Associated with the Maintenance of Low‐Level Viremia in Antiretroviral–Treated Individuals with Drug‐Resistant Human Immunodeficiency Virus Type 1

Antiretroviral (ARV)-treated patients often maintain low to moderate levels of viremia, despite the emergence of drug-resistant human immunodeficiency virus (HIV). We studied host and viral factors that may contribute to the control of viral replication in a cohort of 189 adults. Among ARV-treated patients with detectable viremia, there was a bell-shaped relationship between Gag-specific CD4+ T cell responses and viremia, with the highest cellular immune responses observed in patients with plasma HIV RNA levels of 1000-10,000 copies/mL. In contrast, there was a negative association between Gag-specific CD4+ T cell responses and viremia among ARV-untreated individuals with wild-type HIV. Strong cellular immune responses among individuals with drug-resistant HIV predicted subsequent lack of virological progression. Finally, there was a positive correlation between replicative capacity and viremia. Collectively, these data suggest that the selection of drug-resistance mutations may reduce the pathogenic potential of HIV, which leads to a balanced state of enhanced cellular immunity and low-level viremia.

T cell activation is associated with lower CD4+ T cell gains in human immunodeficiency virus-infected patients with sustained viral suppression during antiretroviral therapy

Although T cell activation is associated with disease progression in untreated human immunodeficiency virus type 1 (HIV-1) infection, its significance in antiretroviral-treated patients is unknown. Activated (CD38(+)HLA-DR(+)) T cell counts were measured in 99 HIV-infected adults who had maintained a plasma HIV RNA level <or=1000 copies/mL for a median of 21 months while receiving antiretroviral therapy. Patients with sustained viral suppression had lower levels of T cell activation than untreated patients but higher levels than HIV-uninfected control subjects. Persistent T cell activation was associated with decreased CD4(+) T cell gains during therapy. For every 5% increase in the proportion of activated CD8(+) T cells, 35 fewer CD4(+) T cells/mm(3) were gained. Increased T cell activation was associated with shorter duration of viral suppression, hepatitis C virus coinfection, frequent low-level viremia, and lower nadir CD4(+) T cell counts. Interventions that directly target T cell activation or the determinants of activation may prove to be useful adjuvants to antiretroviral therapy.

A pilot study of the discontinuation of antifungal therapy for disseminated cryptococcal disease in patients with acquired immunodeficiency syndrome, following immunologic response to antiretroviral therapy

To determine whether microbiologic cure of acquired immunodeficiency syndrome (AIDS)-related disseminated cryptococcosis is possible in patients receiving highly active antiretroviral therapy (HAART), antifungal therapy was discontinued in 6 patients with a history of disseminated cryptococcosis who had received > or =12 months of antifungal therapy. All were asymptomatic and had absolute CD4+ T cell counts of >150 cells/microL (range, 178-525 cells/microL). Blood, cerebrospinal fluid (CSF), and urine samples were obtained for fungal culture. Serum and CSF cryptococcal antigen titers were also obtained. All 6 patients had CSF and blood cultures negative for Cryptococcus neoformans and were receiving HAART. All patients' subsequent cultures remained sterile, and all patients were clinically asymptomatic 24 months after ending antifungal therapy. Disseminated cryptococcal disease can be cured by prolonged antifungal therapy in some patients with AIDS who experience sustained CD4 lymphocyte increases while receiving HAART.