Patrick M. Tarwater

Effectiveness of potent antiretroviral therapies on the incidence of opportunistic infections before and after AIDS diagnosis.

ObjectivesTo determine the effectiveness of potent antiretroviral therapy in reducing opportunistic infections (OI) as both a presenting event and subsequent to an AIDS-defining event. Design and methods A total of 543 seroconverters and 1470 men with AIDS were compared for the time to development of OI as the presenting AIDS event and as a subsequent event in the 1984–1989, 1990–1992, 1993–1995, and 1996–1998 periods, when the major treatments were no therapy, monotherapy, combination therapy, and potent antiretroviral therapy, respectively. ResultsThe seroconverters suffered 132 OI and the participants with AIDS had 717 OI. The relative hazard (RH) of OI as the presenting AIDS event declined by 81% in the calendar period when potent antiretroviral therapy was available compared with the monotherapy period. Declines were observed for Mycobacterium avium complex, cytomegalovirus disease, and esophageal candidiasis, but were statistically significant only for Pneumocystis carinii pneumonia. The RH of OI as a secondary infection dropped by 77% in the last calendar period compared with the monotherapy period. A significant decline was observed for all four OI. Prophylactic drug use did not increase in the era of potent antiretroviral therapy. ConclusionThe hazard of OI in the era of potent antiretroviral therapy has declined dramatically compared with the era of monotherapy, despite the concurrent decrease in the use of prophylactic drugs. Physicians should consider whether it is necessary to include prophylactic drugs as part of the complex drug regimen for patients on potent antiretroviral therapy.

Increased Macrophage Chemoattractant Protein-1 in Cerebrospinal Fluid Precedes and Predicts Simian Immunodeficiency Virus Encephalitis

Macrophage chemoattractant protein-1 (MCP-1) may be a key trigger for the influx of macrophages into the brain in human immunodeficiency virus (HIV) encephalitis. In this study, simian immunodeficiency virus-infected macaques that developed moderate-to-severe encephalitis had significantly higher MCP-1 levels in cerebrospinal fluid (CSF) than in plasma as early as 28 days after inoculation, which was before the development of brain lesions. In contrast, CSF:plasma MCP-1 ratios remained constant at preinoculation levels in macaques that developed minimal or no encephalitis. Abundant MCP-1 protein and mRNA were detected in both macrophages and astrocytes in the brain. Macaques with increased MCP-1 in CSF had significantly greater expression of markers of macrophage and microglia activation and infiltration (CD68; P= .003) and astrocyte activation (glial fibrillary acidic protein; P= .019 and P= .031 in white and gray matter, respectively). The results suggest that the CSF:plasma MCP-1 ratio may be a valuable prognostic marker for the development of HIV-induced central nervous system disease.

The Central Nervous System as a Reservoir for Simian Immunodeficiency Virus (SIV): Steady-State Levels of SIV DNA in Brain from Acute through Asymptomatic Infection

Latent reservoirs of human immunodeficiency virus (HIV) present significant challenges for eradicating HIV from infected persons, particularly reservoirs in the brain established during acute infection. A simian immunodeficiency virus (SIV)/macaque model of HIV dementia was used to show that viral DNA levels in the brain remained at constant levels from acute through asymptomatic infection, despite significant down-regulation of viral RNA in the brain after the acute phase of infection. Viral replication in the brain coincided with activation of macrophages and microglia in the central nervous system; down-regulation of viral replication coincided with increased infiltration of cytotoxic lymphocytes and reduced activation of macrophages and microglia in the brain. Comparison of viral genotypes in the central nervous system and peripheral blood mononuclear cells suggests that recrudescence of viral replication in brain occurs by reactivation of latent viral DNA. Latent virus in the brain must be considered in therapeutic strategies to eliminate HIV from infected persons.

Increase and plateau of CD4 T-cell counts in the 3 1/2 years after initiation of potent antiretroviral therapy

We evaluated CD4 cell counts over a 3½ year period following the initiation of potent antiretroviral therapy (ART) in the Multicenter AIDS Cohort Study. The study population included 314 HIV‐infected gay men who provided CD4 cell counts for at least 2 years after the initiation of potent ART. Trends in CD4 cell counts and plasma HIV‐RNA were analyzed by regression methods that incorporated the statistical dependencies of outcomes measured over time within individuals. Regardless of CD4 cell count at initiation of potent ART, CD4 cell counts increased significantly (p < .05) in the first 2 years after initiation. However, between 2 and 3½ years after initiation, these counts neither increased nor decreased. The pattern of the proportion with plasma HIV‐RNA <400 copies/ml was similar to CD4 cell count (i.e., increased significantly after initiation and plateau in the subsequent 1½ years). The single most important predictor of the steady state CD4 cell count that was maintained between 2 and 3½ years after initiation was the change in plasma HIV‐RNA in the first year after initiation of potent ART.

Simian Immunodeficiency Virus-Infected Macaques Treated with Highly Active Antiretroviral Therapy Have Reduced Central Nervous System Viral Replication and Inflammation but Persistence of Viral DNA

BACKGROUND During the era of highly active antiretroviral therapy (HAART), the prevalence of HIV-associated central nervous system (CNS) disease has increased despite suppression of plasma viremia. METHODS In a simian immunodeficiency virus (SIV) model system in which all animals develop AIDS and 90% develop CNS disease by 3 months after inoculation, pigtailed macaques were treated with a regimen of tenofovir disoproxil fumarate, saquinavir, atazanavir, and an integrase inhibitor starting at 12 days after inoculation and were euthanized at approximately 175 days after inoculation. RESULTS Plasma and cerebrospinal fluid (CSF) viral loads declined rapidly after the initiation of HAART. Brain viral RNA was undetectable at necropsy, but viral DNA levels were not different from those in untreated SIV-infected macaques. CNS inflammation was significantly reduced, with decreased brain expression of major histocompatibility complex class II and glial fibrillary acidic protein and reduced levels of CSF CCL2 and interleukin 6. Brain from treated macaques had significantly lower levels of interferon beta, type 1 interferon-inducible gene myxovirus (influenza) resistance A, and indolamine 2,3-dioxygenase messenger RNA, suggesting that immune hyperactivation was suppressed, and fewer CD4(+) and CD8(+) T cells, suggesting that trafficking of T cells from peripheral blood was reduced. Brain levels of CD68 protein and tumor necrosis factor alpha and interferon gamma RNA were reduced but were not significantly lower, indicating continued CNS inflammation. CONCLUSIONS These data, generated in a rigorous, high-viral-load SIV-infected macaque model, showed that HAART provided benefits with respect to CNS viral replication and inflammation but that no change in the level of viral DNA and continued CNS inflammation occurred in some macaques.

CSF antiretroviral drug penetrance and the treatment of HIV-associated psychomotor slowing

The authors evaluated whether highly active antiretroviral therapy (HAART) with multiple CSF-penetrating drugs results in greater improvement in HIV-associated psychomotor slowing than HAART with a single CSF-penetrating drug. Both groups had improvement in CD4 count, plasma viral load, as well as two tests of psychomotor speed. Comparing the two groups, there were no differences in the mean change for CD4 count, viral load, or any of the neuropsychological tests. Multiple and single CSF-penetrating HAART may be equivalent for treating HIV-associated psychomotor slowing.

Prevalence of Sleep Disturbance in Closed Head Injury Patients in a Rehabilitation Unit

Traumatic brain injury (TBI) is a leading cause of disability in young people in the United States. Disorders of arousal and attention are common in closed head injury (CHI). Daytime drowsiness impairs participation in rehabilitation, whereas nighttime wakefulness leads to falls and behavioral disturbances. Sleep disturbances in TBI reported in the literature have included excessive daytime somnolence, sleep phase cycle disturbance, narcolepsy, and sleep apnea. Although well known to the clinician treating these patients, the extent and prevalence of disrupted sleep in patients in an acute inpatient rehabilitation unit has not been described. Objective. To determine the prevalence of sleep wake cycle disturbance (SWCD) in patients with CHI in a TBI rehabilitation unit. Design. Prospective observational. Setting. Inpatient specialized brain injury rehabilitation unit. Patients. Thirty-one consecutive admissions to a brain injury rehabilitation unit with the diagnosis of CHI. Results. Twenty-one patients (68%) had aberrations of nighttime sleep. There was no significant difference in Glasgow Coma Score on admission to trauma nor was there any significant difference in age between the affected and unaffected groups. Patients with SWCD had longer stays in both the trauma center (P < .003) and the rehabilitation center (P < .03). Conclusions. There is a high prevalence of SWCD in CHI patients admitted to a brain injury rehabilitation unit. Patients with SWCD have longer stays in both acute and rehabilitation settings and may be a marker for more severe injury.

Coordinated regulation of SIV replication and immune responses in the CNS.

Central nervous system (CNS) invasion during acute-stage HIV-infection has been demonstrated in a small number of individuals, but there is no evidence of neurological impairment at this stage and virus infection in brain appears to be controlled until late-stage disease. Using our reproducible SIV macaque model to examine the earliest stages of infection in the CNS, we identified immune responses that differentially regulate inflammation and virus replication in the brain compared to the peripheral blood and lymphoid tissues. SIV replication in brain macrophages and in brain of SIV-infected macaques was detected at 4 days post-inoculation (p.i.). This was accompanied by upregulation of innate immune responses, including IFNβ, IFNβ-induced gene MxA mRNA, and TNFα. Additionally, IL-10, the chemokine CCL2, and activation markers in macrophages, endothelial cells, and astrocytes were all increased in the brain at four days p.i. We observed synchronous control of virus replication, cytokine mRNA levels and inflammatory markers (MHC Class II, CD68 and GFAP) by 14 days p.i.; however, control failure was followed by development of CNS lesions in the brain. SIV infection was accompanied by induction of the dominant-negative isoform of C/EBPβ, which regulates SIV, CCL2, and IL6 transcription, as well as inflammatory responses in macrophages and astrocytes. This synchronous response in the CNS is in part due to the effect of the C/EBPβ on virus replication and cytokine expression in macrophage-lineage cells in contrast to CD4+ lymphocytes in peripheral blood and lymphoid tissues. Thus, we have identified a crucial period in the brain when virus replication and inflammation are controlled. As in HIV-infected individuals, though, this control is not sustained in the brain. Our results suggest that intervention with antiretroviral drugs or anti-inflammatory therapeutics with CNS penetration would sustain early control. These studies further suggest that interventions should target HIV-infected individuals with increased CCL2 levels or HIV RNA in the CNS.

Mechanism for the Establishment of Transcriptional HIV Latency in the Brain in a Simian Immunodeficiency Virus–Macaque Model

BACKGROUND The brain is considered to be a reservoir of latent human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV). We examined the mechanism by which innate immune responses contribute to the establishment of this reservoir. METHODS Gene-specific RNA and DNA were quantitated using real-time reverse-transcription polymerase chain reaction (RT-PCR). Protein expression was examined using Western blot analysis. Binding to and regulation of the SIV long terminal repeat (LTR) was examined using electrophoretic mobility shift assay, luciferase reporter constructs, and chromatin immunoprecipitation assay. RESULTS Interferon-beta (IFN-beta) and myxovirus A (MxA) mRNA are produced in the brain during acute SIV infection. IFN-beta both suppresses SIV LTR activity and induces expression of the dominant-negative isoform of CCAAT/enhancer-binding protein-beta (C/EBP-beta). C/EBP-beta and its dominant-negative isoform respectively enhance and suppress histone acetylation at the SIV LTR and are present at the SIV LTR in vivo. SIV DNA persists when viral RNA is undetectable in the brain, and activation of the LTR is suppressed at the level of histone acetylation. CONCLUSION Innate immune responses to virus infection that suppress acute virus replication in the brain also facilitate transcriptional latency of SIV. These data provide the first mechanistic model of HIV latency in the brain.

Response to systemic HIV viral load suppression correlates with psychomotor speed performance.

The authors evaluated the association of a virologic response to highly active antiretroviral therapy, or a subsequent rebound, with performance on two measures of psychomotor speed in HIV-positive subjects. Virologic suppression was associated with improved performance on measures of psychomotor speed, and virologic rebound was associated with psychomotor speed performance decline. Changes in plasma HIV viral load in HIV-positive individuals with cognitive slowing correlate with performance on tests of psychomotor speed.