Gabriella D'Ettorre

HIV-associated immune activation: From bench to bedside

HIV infection is associated with a state of chronic, generalized immune activation that has been shown in many studies to be a key predictor of progression to AIDS. Consistent with this model, nonpathogenic SIV infections of natural hosts, such as the sooty mangabeys, are characterized by low levels of immune activation during the chronic phase of infection. The molecular, cellular, and pathophysiological mechanisms underlying the HIV-associated immune activation are complex and still poorly understood. There is, however, growing consensus that both viral and host factors contribute to this phenotype, with emphasis on the role played by the mucosal immune dysfunction (and consequent microbial translocation) as well as the pattern of in vivo-infected CD4(+) T cells. The observation that antiretroviral therapy (ART)-induced suppression of HIV replication does not fully resolve immune activation provided the rationale for a number of exploratory studies of potential immune modulatory treatments to be used in HIV-infected individuals in addition to standard ART. This review provides an update on the causes and consequences of the HIV-associated immune activation, and a summary of the immune modulatory approaches that are currently under clinical investigation.

Improvement in neutrophil and monocyte function during highly active antiretroviral treatment of HIV-1-infected patients

OBJECTIVE To investigate the effect of highly active antiretroviral treatment (HAART) on neutrophil and monocyte function in patients with moderately advanced HIV-1 infection. DESIGN Eighteen HIV-1-infected patients with CD4 T cell counts below 350/microl, no concomitant active infection, and no previous use of protease inhibitors were treated with indinavir or ritonavir and two reverse-transcriptase inhibitors and were followed up for 9 months. Ten age- and sex-matched healthy subjects were included as controls. METHODS The functional activity of neutrophils and monocytes was measured by assessing chemotaxis towards a bacterial peptide, killing activity against Candida albicans, and oxidative burst as measured by chemiluminescence production. RESULTS Neutrophils and monocytes from the treatment group exhibited a significantly diminished baseline chemotactic and fungicidal activity compared with healthy controls (P < 0.001). After starting HAART, there was a significant improvement in chemotaxis and fungicidal activity of phagocytic cells (P < 0.001). Values of chemotaxis reached normal ranges in 13 out of 18 patients (72%) for neutrophils and eight out of 18 (44%) for monocytes, whereas phagocyte killing was rarely restored to normal values (3/18 cases for monocytes and 0/18 for neutrophils). The administration of HAART was also associated with significantly increased phagocyte chemiluminescence production in response to phorbol-12-myristate 13-acetate or opsonized C. albicans (P < 0.01). CONCLUSION The functional improvement of two critical components of innate antimicrobial immunity, such as neutrophils and monocytes, may contribute to the improved cell-mediated immune responses against opportunistic infections in HAART-treated patients.

Cross-presentation of caspase-cleaved apoptotic self antigens in HIV infection

We found that the proteome of apoptotic T cells includes prominent fragments of cellular proteins generated by caspases and that a high proportion of distinct T cell epitopes in these fragments is recognized by CD8+ T cells during HIV infection. The frequencies of effector CD8+ T cells that are specific for apoptosis-dependent epitopes correlate with the frequency of circulating apoptotic CD4+ T cells in HIV-1–infected individuals. We propose that these self-reactive effector CD8+ T cells may contribute to the systemic immune activation during chronic HIV infection. The caspase-dependent cleavage of proteins associated with apoptotic cells has a key role in the induction of self-reactive CD8+ T cell responses, as the caspase-cleaved fragments are efficiently targeted to the processing machinery and are cross-presented by dendritic cells. These findings demonstrate a previously undescribed role for caspases in immunopathology.

Interleukin-15 in HIV infection: immunological and virological interactions in antiretroviral-naive and -treated patients.

Objective To investigate the immunological and virological interactions between interleukin (IL)-15 and HIV in antiretroviral-naive and highly active antiretroviral therapy (HAART)-treated patients. Design Three groups of HIV-infected patients were studied: 20 untreated patients with advanced disease; eight patients with viral suppression and immunological response to HAART; and 10 patients with virological and immunological treatment failure. Eleven healthy blood donors were included as controls. Methods The following parameters were evaluated: the production of IL-15 by peripheral blood mononuclear cells (PBMC) stimulated with lipopolysaccharide, Candida albicans and Mycobacterium avium complex; the ability of IL-15 to induce the secretion of IL-8 and monocyte chemotactic protein-1 (MCP-1) from HIV-positive monocytes; and the virological effect of IL-15 and IL-2 on HIV replication in mononuclear cells. Results IL-15 production by PBMC was significantly decreased in antiretroviral-naive patients and in those with treatment failure. On the contrary, in patients with response to HAART IL-15 production was comparable to that of healthy donors. IL-15 was able to stimulate HIV-positive monocytes to produce chemokines, such as IL-8 and MCP-1, that specifically attract neutrophils and monocytes to the site of inflammation thus possibly improving immune response to pathogens during HIV infection. Finally, IL-15 had no major effect on HIV replication in vitro, while only simultaneous administration with IL-2 may induce high levels of HIV production. Conclusions This in vitro study provides new insights in the area of IL-15–HIV interactions and suggests that IL-15 may represent a potential candidate for cytokine treatment in combination with HAART during HIV infection.

HIV Persistence in the Gut Mucosa of HIV-Infected Subjects Undergoing Antiretroviral Therapy Correlates with Immune Activation and Increased Levels of LPS

We investigated the relationship between viral persistence in the gut, microbial translocation, and T cell activation during chronic HIV infection. Plasma levels of LPS, fraction of circulating CD8+CD38+ T cells, and levels of HIV-DNA in rectosigmoid biopsies and peripheral blood mononuclear cells were determined in 22 HIV-infected individuals and 10 healthy controls. We found that in untreated HIV-infected individuals, HIV-DNA load was higher in the gut mucosa than in the blood. Also, ART-treated patients exhibited lower levels of LPS and CD8+CD38+ T cells than untreated patients, but higher levels than controls. In ART-treated individuals, the level of HIV-DNA in the gut correlated with levels of LPS and fraction of CD8+CD38+ T cells. We concluded that in ART-treated individuals, higher levels of gut-associated HIV-DNA are associated with persistent immune activation and microbial translocation.

Hospital-acquired infection surveillance in a neonatal intensive care unit.

BACKGROUND Hospital-acquired infections (HAIs) represent an important cause of morbidity and mortality in neonatal intensive care units (NICUs). METHODS All neonates admitted for > 48 hours between January 2003 and December 2006 in the NICU of the teaching hospital Umberto I of Rome, Italy were considered. RESULTS Of the 575 neonates evaluated, 76 (13.2%) developed a total of 100 HAIs, including 36 bloodstream infections (BSIs), 33 pneumonias, 19 urinary tract infections, 8 conjunctivitis, and 4 onphalitis. There were 7.8 HAIs/1000 patient-days and 12.5 BSIs/1000 days of umbilical catheterization. Logistic analysis identified an association with mechanical ventilation (odds ratio [OR] = 3.05; 95% confidence interval [CI] = 1.75 to 5.31; P < .01) and birth weight <or= 1500 g (OR = 2.34; 95% CI = 1.36 to 4.03; P < .01). Thirty-five neonates (6.1%) died. Klebsiella pneumoniae (37.7%) and coagulase-negative staphylococci (28.6%) were the most frequently isolated microorganisms. Only 3 Candida spp determined BSIs (8.3%). BSI mortality was higher in infections with gram-negative pathogens (36.4%) than in infections with gram-positive pathogens (4.5%). CONCLUSIONS Although we found a low infection and mortality rate, attention should be directed toward antibiotic-resistant gram-negative pathogens.

Ex vivo and in vitro effect of human immunodeficiency virus protease inhibitors on neutrophil apoptosis

Polymorphonuclear leukocytes (PMNL) from human immunodeficiency virus (HIV)-infected patients exhibit accelerated apoptosis and impaired functional activity. HIV protease inhibitor-based therapy produces improvements in both acquired and innate immune responses. Ex vivo and in vitro effects of HIV protease inhibitors on apoptosis and chemotaxis of PMNL were evaluated. After therapy, there was a rapid and significant decrease of PMNL apoptosis, which correlated with increased chemotactic function. These findings were found both in patients with immunological and virological response and in control subjects who showed an increase in CD4(+) T cell counts but no concomitant decline in HIV load. After in vitro treatment with ritonavir or indinavir, apoptosis of both HIV-infected and -uninfected PMNL markedly decreased and correlated with significant enhancement of chemotaxis. These results suggest that HIV protease inhibitors may improve the PMNL function by reducing the apoptosis rate and that this effect may, at least in part, be independent of their antiviral activity.

Type-specific human papillomavirus-DNA load in anal infection in HIV-positive men

Objective:To characterize anal human papillomavirus (HPV) infections in terms of genotype prevalence and type-specific DNA load in HIV-positive men. Design:HIV-positive men attending the colo-proctological clinic of a University Hospital in Rome were recruited prospectively from November 2004 to July 2007. HIV-negative outpatients attending the same clinic over the same period were used as a control group. Methods:Anal brushings were tested for HPV-DNA using polymerase chain reactions and direct sequencing; type-specific HPV-DNA copies were measured in most positive samples. HPV data were correlated with patient HIV status and risk factors. Results:HPV-DNA infection was detected in 81% of HIV-positive men. Almost all homosexual men were HPV-infected. The infection rate in low-risk HPV types was higher than in high-risk types. The spectrum of HPV genotypes was comparable between HIV-positive and HIV-negative men. Numbers of HPV-DNA copies varied greatly between samples but did not differ significantly between HIV-positive and HIV-negative men. In many samples, low-risk (HPV 6, 61, 70, and 74) viral loads were comparable with those of high-risk HPVs. Conclusion:Type-specific HPV-DNA copies at baseline appear to be independent of patient immune status and of HPV genotype. HPV genotype risk and viral load should be further evaluated for their potential predictive role in persistence and progression.

Drug-Associated Resistance Mutations in Plasma and Peripheral Blood Mononuclear Cells of Human Immunodeficiency Virus Type 1-Infected Patients for Whom Highly Active Antiretroviral Therapy Is Failing

ABSTRACT In 32 patients for whom highly active antiretroviral therapy was failing, a good agreement between drug resistance-associated mutations in plasma and peripheral blood mononuclear cells (PBMCs) was found (k = 0.85). The mutations with the lowest agreement were 20R, 63P, and 84V in the protease gene and 184V in the reverse transcriptase gene. In eight patients, primary drug resistance mutations were detected only in PBMCs.

HIV-1 residual viremia and proviral DNA in patients with suppressed plasma viral load (<400 HIV-RNA cp/ml) during different antiretroviral regimens.

Low levels of plasma viremia (below 50 copies/ml of HIV-1 RNA) can be detected in the majority of HIV+ subjects successfully treated with HAART. Aim of our study was to evaluate the impact of different antiretroviral regimens on this residual viremia and on proviral HIV-1 DNA in HAART-treated subjects with plasma HIV RNA <400 cp/ml and no history of virological failure. To this purpose, a cross-sectional analysis of 319 HIV-positive patients on HAART with plasma HIV RNA <400 cp/ml was performed. Subjects had been on HAART for a median of 3.6 years: the current regimen included two nucleoside reverse transcriptase inhibitors (NRTIs) plus a protease inhibitor (PI) in 104 (32.6%) cases, of which 73 treated with a boosted PI; two NRTIs plus a non-NRTI (NNRTI) were prescribed in 166 (52.2%) cases, and NRTIs-only in 49 cases (15.4%). Patients treated with PI had the lowest nadir CD4 cell count (237+191 cells/microl) compared to patients treated with NNRTI (384+192 cells/microl) or NRTIs-only (387+222 cells/microl). Cell-associated HIV-1 DNA was measured in 231 subjects. Residual viremia was measured in 238 subjects with plasma HIV-1 RNA levels < 50 copies/ml. Multivariate analysis showed that the use of NNRTI was independently associated to low levels of residual viremia and high levels of HIV-1DNA, whereas the use of PI was independently associated to low levels of HIV-1 DNA. The better virological performance of NNRTI in terms of low residual viremia is consistent with specific literature data, whereas the greater impact of PI on the viral reservoirs is noteworthy and needs further investigations.