Emil Toma

Dynamics and Consequences of IL-21 Production in HIV-Infected Individuals: A Longitudinal and Cross-Sectional Study

IL-21 is a relatively newly discovered immune-enhancing cytokine that plays an essential role in controlling chronic viral infections. It is produced mainly by CD4+ T cells, which are also the main targets of HIV-1 and are often depleted in HIV-infected individuals. Therefore, we sought to determine the dynamics of IL-21 production and its potential consequences for the survival of CD4+ T cells and frequencies of HIV-specific CTL. For this purpose, we conducted a series of cross-sectional and longitudinal studies on different groups of HIV-infected patients and show in this study that the cytokine production is compromised early in the course of the infection. The serum cytokine concentrations correlate with CD4+ T cell counts in the infected persons. Among different groups of HIV-infected individuals, only elite controllers maintain normal production of the cytokine. Highly active antiretroviral therapy only partially restores the production of this cytokine. Interestingly, HIV infection of human CD4+ T cells inhibits cytokine production by decreasing the expression of c-Maf in virus-infected cells, not in uninfected bystander cells. We also show that the frequencies of IL-21–producing HIV-specific, but not human CMV-specific, Ag-experienced CD4+ T cells are decreased in HIV-infected viremic patients. Furthermore, we demonstrate in this study that recombinant human IL-21 prevents enhanced spontaneous ex vivo death of CD4+ T cells from HIV-infected patients. Together, our results suggest that serum IL-21 concentrations may serve as a useful biomarker for monitoring HIV disease progression and the cytokine may be considered for immunotherapy in HIV-infected patients.

Evidence for a correlation between antibody-dependent cellular cytotoxicity-mediating anti-HIV-1 antibodies and prognostic predictors of HIV infection

Using our gp120/41-expressing, NK cell activity-resistant CEM.NKR cell clones as targets in HIV-1-specific antibody-dependent cellular cytotoxicity (ADCC) assays, we demonstrate here that the serum titers of anti-HIV-1 ADCC antibodies bear a significant (P < 0.05) positive correlation with the peripheral blood CD4+ T cell counts and a negative one with the number of copies of HIV-1 RNA in the plasma of HIV-infected individuals. These findings underscore the importance of these antibodies as a protective immune parameter in these infections.

Decreased levels of circulating IL-21 in HIV-infected AIDS patients: Correlation with CD4+ T-cell counts

IL-21 is a relatively newly discovered multifunctional and pleiotropic cytokine. It is produced primarily by CD4(+) T cells, the principal targets of the virus, and therefore this cytokine has special relevance to HIV infection. Here we show for the first time that serum levels of this cytokine are significantly reduced in HIV-infected AIDS patients and correlate significantly with their CD4(+) T-cell counts. These data suggest that the cytokine levels could act as a valuable biomarker for the progression of AIDS.

Comparative Evaluation of the Cytomegalovirus DNA Load in Polymorphonuclear Leukocytes and Plasma of Human Immunodeficiency Virus-Infected Subjects

The cytomegalovirus (CMV) DNA load was determined in polymorphonuclear leukocytes (PMNL) and plasma samples from 106 human immunodeficiency virus-infected subjects at risk of developing CMV disease (group 1) and from 27 AIDS patients with documented CMV disease (group 2). For both groups, the number of CMV copies in PMNL was significantly higher than in plasma when results were derived from an equivalent blood volume (P < .001, PMNL vs. plasma). Additionally, group 2 (symptomatic) patients had a greater viral DNA load than group 1 (asymptomatic) subjects (P < .001 for both PMNL and plasma). The sensitivity, specificity, and positive and negative predictive values of qualitative polymerase chain reaction using PMNL (PCR-PMNL) for the presence of CMV disease were 100%, 58%, 38%, and 100%, respectively, compared with 70%, 93%, 74%, and 92% for qualitative PCR-plasma and 93%, 92%, 76%, and 98% for quantitative PCR-PMNL using a cutoff of 16,000 copies/mL. Thus, the best strategy for diagnosing CMV disease in these individuals relies on quantitative assessment of the viral DNA load in PMNL.

Clindamycin with Primaquine vs. Trimethoprim-Sulfamethoxazole Therapy for Mild and Moderately Severe Pneumocystis carinii Pneumonia in Patients with AIDS: A Multicenter, Double-Blind, Randomized Trial (CTN 004)

This double-blind, randomized, multicenter trial compared clindamycin/primaquine (Cm/Prq) with trimethoprim-sulfamethoxazole (TMP-SMZ) as therapy for AIDS-related Pneumocystis carinii pneumonia (PCP). Forty-five patients received clindamycin (450 mg four times daily [q.i.d.]) and primaquine (15 mg of base/d); 42 received TMP-SMZ (320 mg/1,600 mg q.i.d. if weight of > or = 60 kg or 240 mg/1,200 mg q.i.d. if weight of < 60 kg) plus placebo primaquine. Overall, the efficacy of Cm/Prq was similar to that of TMP-SMZ (success rate, 76% vs. 79%, respectively); Cm/Prq was associated with fewer adverse events (P = .04), less steroid use (P = .18), and more rashes (P = .07). These differences were even greater for patients with PaO2 of > 70 mm Hg (P = .02, P = .04, and P = .02, respectively). For patients with PaO2 of < or = 70 mm Hg (23 Cm/Prq recipients and 21 TMP-SMZ recipients), the efficacy of Cm/Prq was similar to that of TMP-SMZ (success rate, 74% vs. 76%, respectively); Cm/Prq was associated with similar adverse events (P = .57), steroid use (P = .74), and rashes (P = .78). This trial confirms that Cm/Prq is a reasonable alternative therapy for mild and moderately severe PCP.

Clindamycin with primaquine for pneumocystis carinii pneumonia

Combined therapy with clindamycin and primaquine was used in twenty-eight episodes of Pneumocystis carinii pneumonia in 25 patients, of whom 17 had been unresponsive or intolerant to conventional treatment and 8 were being treated for the first time. The treatment was effective in all but two episodes, the main adverse reaction being a generalised maculopapular rash.

Emergence and prevalence of cytomegalovirus UL97 mutations associated with ganciclovir resistance in AIDS patients

Objectives: To evaluate the prevalence of the most common cytomegalovirus (CMV) UL97 mutations associated with ganciclovir resistance directly in polymorphonuclear leukocytes (PMNL) of patients with AIDS and CMV retinitis. Also to correlate the presence (or absence) of these mutations with the systemic CMV viral load and the ophthalmologic outcome of these subjects. Methods: Monthly blood samples were obtained from 19 patients with AIDS and CMV retinitis who had been treated with systemic ganciclovir for ≥ 2 months. Detection of CMV UL97 mutations was done using nested PCR amplification followed by restriction enzyme analysis. The viral load was assessed with a polymerase chain reaction-based assay and non-isotopic hybridization detection. Results: CMV UL97 mutations were detected in PMNL of four of 13 (30.8%) patients who had been treated with ganciclovir for ≥ 3 months but in none of six patients who had been treated for < 3 months. All four patients with detectable UL97 mutations were presenting evidence of retinitis progression at the time those mutations were first detected (mean, 145.7 days of ganciclovir) and three of four patients had a viral DNA load > 10 000 copies per 105 PMNL contrasting with the copy numbers in the 15 subjects without mutations (mean, 492.9 copies per 105 PMNL after a mean of 146.8 days of ganciclovir). Conclusions: The prevalence of the most common CMV UL97 mutations associated with ganciclovir resistance in PMNL of patients with AIDS treated for ≥ 3 months (30.8%) appears to be higher than the rate of emergence of ganciclovir-resistant CMV isolates as previously reported using phenotypic assays (about 8%). Moreover, the detection of these mutations is associated with a considerable increase in the CMV DNA load in the blood as well as with progression of CMV retinitis during ganciclovir therapy.

IL-15 and HIV Infection: Lessons for Immunotherapy and Vaccination

IL-15 is a pleiotropic and multifunctional cytokine that has a diverse array of distinct biological effects in the body. It plays a crucial role in host defense from viral and non-viral intracellular pathogens. The cytokine is essential for the development and differentiation of NK cells and for homeostatic expansion of CD8+ memory T cells, NKT cells and certain subsets of intestinal intra-epithelial lymphocytes (iIEL). It acts as a survival factor and inhibits spontaneous apoptosis in T, B and NK cells by increasing expression of different anti-apoptotic proteins. Several studies have shown that IL-15 production is compromised in HIV-infected AIDS patients and exogenous IL-15 drastically enhances functions of immune cells from these patients. Considering these distinct immune enhancing effects, relative safety in animal models, and minimal effects on HIV replication, IL-15 may represent a better cytokine for immune reconstitution in these patients. Furthermore, IL-15 may also act as a better adjuvant in eliciting antiviral immunity in anti-HIV vaccine strategies.

Determinants of Rifabutin-Associated Uveitis in Patients Treated with Rifabutin, Clarithromycin, and Ethambutol for Mycobacterium avium Complex Bacteremia: A Multivariate Analysis

Uveitis occurred in a substantial proportion of AIDS patients receiving rifabutin, 600 mg daily, together with clarithromycin and ethambutol for treatment of Mycobacterium avium complex bacteremia. A case-control study was undertaken to examine potential risk factors for developing uveitis. Of eight parameters examined, only baseline body weight predicted the development of uveitis by both univariate and multivariate analyses (P = .001). The incidence of uveitis was 14% in patients weighing >65 kg, 45% in patients between 55 and 65 kg, and 64% in patients <55 kg. Concomitant therapy with fluconazole, a drug known to raise serum rifabutin concentrations, was not associated with an increased incidence of uveitis. The risk of uveitis was markedly reduced when rifabutin was given at 300 mg daily in combination with clarithromycin and ethambutol.

Enhancement of natural killer and antibody-dependent cytolytic activities of the peripheral blood mononuclear cells of HIV-infected patients by recombinant IL-15.

Natural killer (NK) cells are an important subset of lymphocytes capable of killing virus-infected target cells without prior sensitization. HIV-infected individuals show impairment of their NK cell activity. Although the mechanism responsible for this defect remains unclear, NK cytotoxicity of lymphocytes from these individuals can be partially restored by interleukin (IL)-2. IL-15 is a recently discovered cytokine that shares many biologic activities with IL-2--for example, enhancement of NK activity. In this study, we investigated the effect of recombinant IL-15 (rIL-15) on the NK and antibody-dependent cellular cytotoxicity (ADCC) effector activities of peripheral blood mononuclear cells (PBMCs) from HIV-infected individuals using K562 cell line and HIV gp120-expressing cells. The effect of anti-IL-15 antibodies on NK activity was also examined using PBMCs of HIV-seronegative individuals. Our results show that NK and ADCC activities of PBMCs in HIV-seropositive patients were significantly lower than those of seronegative donors (p < or = 0.05). However, these two activities were significantly enhanced when rIL-15 was added to the assay wells (p < or = 0.05). Moreover, addition of saturating concentrations of neutralizing monoclonal antibodies (mAb) specific for IL-2, IL-12, or interferon (IFN)-gamma in the assays failed to inhibit IL-15-mediated enhancement of NK cell functions. Only the antibody against IL-15 abrogated the upregulation of NK and ADCC activities mediated by IL-15, suggesting that this cytokine enhances NK cell functions through a mechanism that is independent of the induction of other cytokines. IL-15 did not exert any modulatory effect on the expression of CD16 or CD56 molecules. Our results show that IL-15 can increase the NK and ADCC activities of the PBMCs of HIV-infected individuals in vitro. In view of its higher therapeutic index as determined using murine models, IL-15 may represent a better immunotherapeutic agent than IL-2 to restore these functions in HIV-seropositive patients.