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CROI 2016: Neurologic Complications of HIV Infection-gender; immune activation/inflammation; HIV CNS Reservoirs: implications for eradication/cure
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Download the PDF here
Serena S. Spudich, MD; Beau M. Ances, MD, PhD
https://www.iasusa.org/tam/may-june2016
from Jules: neurotic & brain decline in functioning is another aging related problem that older patients face. There is little data & no database data reported the current situation & difficulties facing older patients, it is difficult to capture real time current data-but we know from anecdotal reports many older patients >65-are experiencing lots of problems-many are all inter-related-falls & fractures are associated with cognitive impairment-lipid abnormalities & renal function are associated cognitive impairment-all the metabolic abnormalities are associated-of particular note is that immune activation & inflammation in the periphery can cause brain dysfunction & cognitive impairment & neuropathy appears associated with immune activation & inflammation in the periphery.
Excerpts
The brain remains a major target for HIV infection and a site of potential complications for HIV-infected individuals. Emerging data presented at the 2016 Conference on Retroviruses and Opportunistic Infections suggest that during the early stages of infection, activated CD4+ cells may traffic the virus into the central nervous system (CNS). HIV is detectable in cells and tissues of the CNS in some individuals despite suppressive antiretroviral treatment.
A potential source of cerebrospinal fluid HIV escape may be compartmentalized HIV replication within macrophage lineage cells. Virally infected cells can traffic out of the CNS and may have the potential to reseed the systemic compartment. Additional modifiers of HIV-associated neurocognitive disorder (HAND) were identified, including female sex and hepatic dysfunction. Large epidemiologic studies reported an elevated risk of stroke among HIV-infected individuals, related to traditional vascular risk factors, history of recreational drug use, and HIV measures (lower CD4+ cell nadir and higher viral load). Brain imaging may provide a noninvasive means for detecting early changes in the brain associated with HIV infection and may assist in prognosis of HAND. Some potential adjunctive therapies to standard antiretroviral therapy for HIV-infected individuals were considered.
"Although many presentations centered on ingress of cells and HIV into the CNS, the possibility that cells originating in the CNS may traffic out of this compartment into the periphery is a concern of key importance to HIV eradication efforts"
"peripheral immune activation may facilitate entry of HIV-infected cells into the CNS compartment, mediating the relationship between HIV RNA produced in the periphery and that detected in the CSF."
"Overall, use of antiretroviral therapy has led to a reduction in the incidence but not prevalence of more severe forms of HAND.11,12 Findings continue to suggest that despite the introduction of antiretroviral therapy and subsequent virology control, there appears to be a substantial percentage of HIV-infected individuals who still have evidence of poorer cognitive performance, atrophy of grey and white matter, and abnormalities in white matter (Abstract 61)."
"infected cells were trafficked from the CNS to the cervical lymph node....These data suggest a route of viral infection from the CNS to the periphery, highlighting the need to adequately treat the CNS compartment during standard HIV treatment and to consider this compartment in viral eradication efforts."
"ability to address immune abnormalities that persist in the CNS in the context of suppressive antiretroviral therapy will be essential to optimal treatment of HIV infection...in HIV-infected individuals well treated with antiretroviral medications.......identified a unique subset of effector memory cells comprising the majority of T cells in CSF but not blood...identifying unique abnormalities that should be mitigated in the optimal treatment of HIV infection in the CNS."
"among women in the WIHS study.....presence of liver fibrosis was associated with poorer overall cognition and performance on verbal learning, executive function, verbal memory, psychomotor speed, fluency, and fine motor tasks. HCV infection status had no independent association with cognition."
"..... it is also plausible that lipid metabolism impacts HAND by increasing the risk of vascular dysfunction that was previously tied to the presence of HAND in the MACS and other cohorts,4,5 providing a rationale for use of statins or other lipid-lowering agents in persons with HAND." [from Jules: statins can cause myopathy & muscle disorders too, has adverse events associated with its use]
Potential differences between HAND in women and in men were explored by Maki and colleagues (Abstract 416), through a comparison of cognitive test performance among women enrolled in the WIHS (Women's Interagency HIV Study) study and men enrolled in the MACS (Multicenter AIDS Cohort Study) (429 HIV-infected and 281 uninfected individuals in each group). The investigators compared performance on 4 common neuropsychologic tests utilized in both studies, using a mixed-effects regression analysis that matched participants by demographic and disease variables. HIV-infected women performed statistically significantly worse on Trail Making and Grooved Pegboard tests, tests of executive function and processing speed, than HIV-infected men. Differences between women and men in these measures may reflect biologic or sociodemographic differences, but this study provides rationale to further investigate the sources of these differences and whether distinct interventions may be required to address them.
Emerging data indicate that HIV DNA and RNA may continue to be detectable in cells and tissues of the CNS in some individuals taking suppressive antiretroviral treatment. A potential source of escape of HIV in CSF may be compartmentalized HIV replication within macrophage lineage cells.
Seipone and colleagues (Abstract 398) approached the question of whether a concurrent opportunistic infection in the CNS might impact the extent of HIV compartmentalization in the CNS by assessing HIV replication among HIV-infected individuals with or without documented tuberculous meningitis (TB meningitis). The investigators found statistically significantly higher levels of HIV RNA in the CSF in 15 individuals with TB meningitis as compared to 22 individuals without TB meningitis. However, in an analysis of env sequencing by single-genome amplification that compared degree of compartmentalization between 4 participants with TB meningitis and 4 without, no clear patterns emerged. This study was limited by a small sample size, but the finding of higher HIV RNA levels in CSF in individuals with an opportunistic infection in the CNS warrants further analysis, specifically of the interaction between HIV replication dynamics and concurrent inflammatory disorders in the CNS, including opportunistic infections.
In a complementary longitudinal study, Bowman and colleagues (Abstract 401) confirmed a relationship between HIV compartmentalization in the CNS and neurocognitive response to antiretroviral therapy. Using single-genome amplification
or deep sequencing of HIV env in CSF and blood, the investigators detected HIV compartmentalization in the CNS in 35% of 28 study participants before the initiation of antiretroviral therapy at CD4+ cell counts below 400 copies/ μL. The effect of HIV compartmentalization was examined with respect to performance on a detailed neuropsychologic testing battery at baseline and at 6 months and 12 months after starting treatment. At the baseline visit, no laboratory parameters differed between the compartmentalized and noncompartmentalized groups, and neurocognitive impairment was not statistically significantly higher in the group with compartmentalization than in the group without. However, at 6 months and 12 months after initiation of antiretroviral treatment, the overall global deficit score, a measure of neurocognitive impairment, was statistically significantly lower in the noncompartmentalized than in the compartmentalized group. An interpretation of this finding may be that measurable HIV compartmentalization in the CNS before the initiation of antiretroviral therapy reflects a robust site of HIV replication in the CNS that is less responsive to therapy due to reduced antiretroviral exposure in CNS tissues or cells of replication. Additionally, or alternately, compartmentalized HIV replication in the CNS before antiretroviral treatment may result in more severe inflammatory and neural injuries that are irreversible or slower to reverse with therapy.
The existence of a viral reservoir is defined not only by the potential for HIV infection of a given cell or tissue but also by the persistence of HIV in the setting of apparently effective antiretroviral treatment. de Oliveira and colleagues (Abstract 143) assessed paired blood and CSF samples from 16 participants with suppressed HIV RNA in blood at a median 2 years after initiation of early (before 4 months of estimated infection) or delayed (after 14 months of estimated infection) antiretroviral therapy. Cell-associated HIV DNA in peripheral blood mononuclear cells (PBMCs) and CSF cellular pellets was measured by digital droplet polymerase chain reaction (PCR) testing, followed by next-generation sequencing of partial env from these samples and subsequent phylogenetic analysis. HIV DNA was detected overall in 15 of 16 PBMC samples and 10 of 16 CSF samples. Although CSF interleukin (IL)-6 and tumor necrosis factor-α were lower among those in the early treatment group, there was no difference between HIV DNA detectability in either sample type between the 2 treatment groups. Genetic analysis of env sequences from 8 paired CSF and blood samples revealed that 7 had statistically significant HIV compartmentalization in the CNS, with unique CSF-specific sequences detected despite early treatment and longitudinal persistence of CSF-unique sequences over a 5-month period during treatment. A challenge of these experiments is the low HIV DNA input from the CSF samples, which could bias compartmentalization analysis. Overall, the findings are consistent with recognition of compartmentalization in the CNS early in untreated HIV infection and suggest the potential persistence of compartmentalized HIV in cells of the CNS despite treatment.
Lamers and colleagues (Abstract 345) similarly demonstrated that HIV DNA persisted in the CNS compartment along with other tissue sites among 20 individuals with undetectable HIV RNA (using a lower limit of detection of 40-400 copies/mL) in plasma at autopsy. Fifteen of these individuals had cancer, and the majority were documented as taking antiretroviral treatment at the time of death, with the remainder documented as taking antiretroviral treatment near the time of death. HIV DNA was detected by digital droplet PCR assay in the majority of 87 brain tissue samples analyzed. Nearly all brain tissue samples demonstrated pathology, although only a few showed classic HIV-associated changes of microglial nodule encephalitis or CD68+ infiltrates. An RNA-scope assay detected HIV RNA colocalizing with CD68+ cells, likely macrophages, in brain samples from 2 donors with CNS malignancies, and single-genome sequencing revealed clustering of HIV DNA from brain with other anatomic compartments. These data are some of the first to demonstrate the persistence of HIV DNA and even HIV RNA in the brains of infected individuals taking apparently systemically successful antiretroviral treatment, necessitating further research into potential HIV persistence in the CNS despite suppression of high-level HIV replication.
CNS HIV Entry and Immune Cell Trafficking
These data support the hypothesis that peripheral immune activation may facilitate entry of HIV-infected cells into the CNS compartment, mediating the relationship between HIV RNA produced in the periphery and that detected in the CSF.
A complete understanding of the mechanisms that establish and maintain CNS HIV infection is key to designing interventions to address potential HIV reservoirs in the CNS. HIV enters the CNS in the first weeks after transmission to the host and can be detected throughout the course of untreated HIV infection. However, the means by which HIV is trafficked into the CNS compartment during initial and chronic infection is incompletely understood. A number of studies focused on aspects of trafficking of HIV or immune cells in or out of the CNS during the course of infection.
In an effort to examine determinants of the level of HIV present in the CNS in the earliest stages of infection, Schuetz and colleagues (Abstract 404) examined various sites, including gut mucosa, PBMCs, and CSF in 38 participants in Thailand with antibody-negative acute HIV infection at an estimated duration of infection of 15 days. The investigators found correlations between measures of immune activation (percentage of CD8+ and Ki67+ cells) in the blood and gut and the level of HIV RNA in the CSF, independent of the level of plasma HIV RNA. These data support the hypothesis that peripheral immune activation may facilitate entry of HIV-infected cells into the CNS compartment, mediating the relationship between HIV RNA produced in the periphery and that detected in the CSF.
Li and colleagues (Abstract 142) examined CD8+ and CD4+ cells and monocytes in paired CSF and blood samples obtained in a longitudinal study of men recently infected with HIV. Beginning at a median 3.3 months post infection, the percentage of activated CD4+ and CD8+ cells increased at an accelerated rate in the CNS compartment compared with the blood during untreated infection; percentage of activated cells in the CNS compartment did not measurably decline during 7 months of follow-up during antiretroviral therapy, despite declining in the blood. Moreover, HIV RNA concentrations in the CSF independently correlated with the percentage of activated CD4+ cells but not of CD8+ cells or activated or trafficked monocytes in CSF. These findings suggest that during the early stages of infection, activated CD4+ cells trafficking to the CNS might be a major source of HIV replication, modifying the traditional concept that infected monocytes are the primary "Trojan horse" carrying HIV to the CNS (for review, see Abstract 62).
Although many presentations centered on ingress of cells and HIV into the CNS, the possibility that cells originating in the CNS may traffic out of this compartment into the periphery is a concern of key importance to HIV eradication efforts. If HIV-infected immune cells or free virus might egress from the CNS, then persistent infection in CNS cells may lead to reseeding of HIV in the systemic compartment despite successful systemic HIV remission or eradication. Recent evidence that the brain has a dedicated lymphatic system that allows for trafficking of immune cells directly from the CNS to the deep cervical lymph nodes supports this concept,1 but trafficking of infected cells has not previously been observed.
Alvarez and colleagues (Abstract 141) presented evidence that infected cells traffic from the CNS, employing super paramagnetic iron oxide nanoparticles (SPIONs; foreign particles likely to be ingested by phagocytic cells, including macrophages and microglial cells in the brain). The investigators injected fluorescent SPIONs into the cisterna magna of the brain of SIV-infected or uninfected macaques, monitoring SPION uptake by perivascular cells during the first day after injection. Robust transit of SPION-containing cells from the CNS to the cervical lymph nodes was observed over the following 7 days in both infected and uninfected animals, and these cells were characterized as CD163+ cells, indicating a macrophage-monocyte lineage. With staining, the investigators confirmed that some of the SPION-containing cells in the lymph nodes of infected animals were SIV infected, demonstrating that in this accelerated macaque model, infected cells were trafficked from the CNS to the cervical lymph node. These data suggest a route of viral infection from the CNS to the periphery, highlighting the need to adequately treat the CNS compartment during standard HIV treatment and to consider this compartment in viral eradication efforts.
The ability to address immune abnormalities that persist in the CNS in the context of suppressive antiretroviral therapy will be essential to optimal treatment of HIV infection. HIV RNA levels, soluble measures of inflammation, and CSF cell characteristics improve in response to systemically suppressive antiretroviral therapy but may not completely normalize despite prolonged treatment.2,3 Chung and colleagues (Abstract 411) demonstrated the feasibility of applying both flow cytometry and newly emerging mass spectrometry methods to examine characteristics of CSF and blood cells in HIV-infected individuals well treated with antiretroviral medications, despite having low clinical CSF white blood cell counts. Mass spectrometry, unlike flow cytometry, uses heavy metals rather than fluorescein dyes to label cell surface receptors, allowing for resolution of up to 40 distinct surface markers simultaneously in a single sample. Among 7 individuals taking antiretroviral treatment, with a median white blood cell count of 2/μL, mass spectrometry generated interpretable data and identified a unique subset of effector memory cells comprising the majority of T cells in CSF but not blood. These methods have potential in future investigations of individuals with treated HIV infection, as a means of identifying unique abnormalities that should be mitigated in the optimal treatment of HIV infection in the CNS.
Valcour and colleagues (Abstract 422) performed a novel exploration of the potential contribution of minimal hepatic encephalopathy associated with liver fibrosis and HAND among women in the WIHS study. Neuropsychologic testing results among 258 women with liver fibrosis-defined by aspartate aminotransferase (AST)-to-platelet ratio index-were compared with those of 1221 women without liver fibrosis within the WIHS study. After adjustment for hepatitis C virus (HCV) infection status and HIV disease markers, the presence of liver fibrosis was associated with poorer overall cognition and performance on verbal learning, executive function, verbal memory, psychomotor speed, fluency, and fine motor tasks. HCV infection status had no independent association with cognition. These findings suggest that liver fibrosis may be an additional contributor to cognitive dysfunction in HIV-infected women in particular and possibly in persons living with HIV infection more generally. These results suggest possible new specific therapeutic interventions for HAND in individuals who have concomitant hepatic dysfunction.
In another assessment of potential toxic metabolic contributors to HAND, mitochondrial dysfunction and neurocognitive performance were evaluated by Samuels and colleagues (Abstract 144), in a cohort of 1011 participants from the CHARTER study. This study revealed a relationship between mitochondrial DNA content in blood cells and the presence of cognitive impairment. This association was primarily driven by correlations among individuals with only incidental comorbidities, suggesting that mitochondrial DNA content in blood cells may be a contributor to HAND in the absence of other factors. In a subset of 335 study participants, elevated cell-free mitochondrial DNA in the CSF was associated with increased measures of HIV RNA, inflammation, and iron metabolism in the CSF but not with neurocognitive performance.
http://www.natap.org/2016/CROI/croi_202.htm
"mtDNA associated with worse cognitive outcomes".....both HIV & ART duration associated with mtDNA damage"
Stroke and Cerebrovascular Disease in HIV: An
Emerging Concern
As HIV becomes more of a chronic disease, additional cofactors (eg, cerebrovascular disease) are becoming increasingly important when treating HIV-infected individuals.6 Becker and colleagues (Abstract 388) suggested that cardiovascular disease risk factors may be as important as HIV-associated factors in predicting rate of change in the brain. Although the overall incidence and mortality of stroke among HIV-infected individuals has decreased, Berenguer and colleagues (Abstract 639) demonstrated that the risk of stroke still remains elevated among HIV-infected individuals compared with uninfected individuals, based on large epidemiologic studies. Even after controlling for traditional risk factors, HIV-infected individuals have a substantially higher risk of ischemic stroke than uninfected individuals.7 Crane and colleagues (Abstract 636) showed that most strokes seen among HIV-infected individuals are ischemic rather than hemorrhagic in nature.
The overall incidence of ischemic stroke was 1.69% among HIV-infected individuals according to data presented by Chow and colleagues (Abstract 43). Although the risk of ischemic stroke is elevated across the lifespan of an individual, the greatest risk was actually seen in younger HIV-infected individuals. In particular, Chow and colleagues demonstrated that HIV-infected women have a higher risk of stroke even after adjustment for age, race, vascular, and sex-specific risk factors (Abstracts 638 and 43). The greatest risk of stroke among HIV-infected women occurred among those aged 40 years to 49 years. Chow and colleagues (Abstract 43) and Crane and colleagues (Abstract 636) identified traditional risk factors associated with ischemic stroke, including older age, elevated blood pressure, active or past recreational drug use, current smoking, diabetes, and HIV-associated variables (lower CD4+ cell nadir and higher viral load). The increased risk of ischemic stroke associated with unsuppressed virus corresponded to an effect of aging by approximately 15 years.
Hatleberg and colleagues (Abstract 637) identified risk factors for hemorrhagic stroke, including elevated blood pressure and poor renal function. Controversy still remains concerning the impact of HCV infection, as one study demonstrated an increased risk for hemorrhagic stroke among HIV/HCV-coinfected individuals. Although Berenguer and colleagues (Abstract 639) identified an increased risk of stroke among a large cohort of HIV/HCV-coinfected individuals in Spain, Crane and colleagues (Abstract 636) and Chow and colleagues (Abstract 43) did not observe a substantially increased risk among participants with HIV/HCV coinfection compared with those with HIV monoinfection in studies performed in the United States. [abs 43-CROI:STROKE INCIDENCE HIGHEST IN WOMEN AND BLACK HIV-INFECTED PARTICIPANTS IN ALLRT COHORT-(02/26/16)]
For all epidemiologic studies, careful analysis and adjudication are needed, as the diagnosis and medical coding of stroke are often complicated and may be overrepresented (approximately 45% of strokes coded using the International Classification of Diseases [ICD]-9 required additional discussion by clinicians). As noted by Crane and colleagues (Abstract 636) and Chow and colleagues (Abstract 43), additional limitations of these large observational datasets include that information is not collected at regular intervals using standard metrics and that, typically, homogenous convenience samples are utilized. These cohorts often have a higher proportion of white men.
HIV and Cardiovascular Disease: Report back from 2016 Conference on Retroviruses and Opportunistic Infections-by Priscilla Hsue MD Professor of Medicine, UCSF -(04/04/16)
CROI abs. 636:Design, implementation, and findings of next generation stroke adjudication in HIV
CROI abs. 638:Persistently Increased Ischemic Stroke Risk in HIV-Infected Women
Juan Berenguer reports stroke rates going down among HIV+ BUT stroke rates going up among HCV/HIV coinfected patients.
http://www.croiwebcasts.org/console/player/29636?mediaType=audio&
Overall, use of antiretroviral therapy has led to a reduction in the incidence but not prevalence of more severe forms of HAND.11,12 Findings continue to suggest that despite the introduction of antiretroviral therapy and subsequent virology control, there appears to be a substantial percentage of HIV-infected individuals who still have evidence of poorer cognitive performance, atrophy of grey and white matter, and abnormalities in white matter (Abstract 61). Underwood and colleagues (Abstract 148) used a k-means cluster method and found that brain and cognitive abnormalities often occurred together in HIV-infected individuals. In particular, increased atrophy of grey matter was associated with lower fractional anisotropy as measured by diffusion tensor imaging.
Cysique and colleagues (Abstract 391) showed that HIVinfected individuals with a history of neurocognitive impairment often have loss of neuronal integrity within subcortical and cortical regions. Granziera and colleagues (Abstract 381) showed that volumetric changes in the brain may have longitudinal predictive power to detect subsequent changes in neuropsychologic performance. A combination of methods (neuroimaging, CSF analysis, and neuropsychologic performance testing) may therefore provide a more complete understanding of changes in the brain caused by HIV infection (Abstract 61). As noted by many of these studies, additional investigations are needed that 1) pool data from various modalities and cohorts (Abstracts 383 and 386); 2) longitudinally access HIV-infected individuals (especially those with well-controlled virus) (Abstracts 384 and 381); and 3) include appropriate uninfected controls for comparison (Abstracts 61 and 146).
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