PURPOSE OF REVIEWRobust and dynamic innate and adaptive responses characterize the acute central nervous system (CNS) response to HIV and other viral infections. In a state of chronic infection or ...viral latency, persistent immune activation associates with abnormality in the CNS. Understanding this process is critical, as immune-mediated abnormality in nonrenewable CNS cells may result in long-term neurologic sequelae for HIV-infected individuals.
RECENT FINDINGSIn humans, immune activation is reduced by suppressive combination antiretroviral therapy, but persists at abnormally elevated levels on treatment. CNS immune activation is initiated in acute infection and progressively increases until combination antiretroviral therapy is started. Newly identified characteristics of the CNS immune surveillance network include features of homeostasis and function of brain microglial cells, lymphatic drainage from CNS to cervical lymph nodes, and cells in cerebrospinal fluid associated with neurocognitive impairment.
SUMMARYMore research is required to determine whether early intervention to reduce infection limits the immunopathology established by sustained immune responses that ultimately fail to resolve infection, and to unravel mechanisms of persistent immune activation during treated HIV so that strategies can be developed to therapeutically protect the brain.
Purpose of Review
This review focuses on the cerebrospinal fluid (CSF) findings in connection to the central nervous system (CNS) reservoir in treatment-naïve and virally suppressed PLWH, followed by ...the findings in CSF HIV-1 escape and analytical treatment interruption studies.
Recent Findings
Compared to chronic infection, initiating antiretroviral therapy (ART) during acute HIV-1 infection results in more homogeneous longitudinal benefits in the CNS. Viral variants in CSF HIV-1 escape are independently linked to infected cells from the systemic reservoir and in the CNS, highlighting the phenomenon as a consequence of different mechanisms. HIV-infected cells persist in CSF in nearly half of the individuals on stable ART and are associated with worse neurocognitive performance.
Summary
Future studies should probe into the origin of the HIV-infected cells in the CSF. Examining the capacity for viral replication would provide new insight into the CNS reservoir and identify strategies to eradicate it or compensate for the insufficiency of ART.
The character of central nervous system (CNS) HIV infection and its effects on neuronal integrity vary with evolving systemic infection. Using a cross-sectional design and archived samples, we ...compared concentrations of cerebrospinal fluid (CSF) neuronal biomarkers in 143 samples from 8 HIV-infected subject groups representing a spectrum of untreated systemic HIV progression and viral suppression: primary infection; four groups of chronic HIV infection neuroasymptomatic (NA) subjects defined by blood CD4+ T cells of >350, 200-349, 50-199, and <50 cells/µL; HAD; treatment-induced viral suppression; and 'elite' controllers. Samples from 20 HIV-uninfected controls were also examined. The neuronal biomarkers included neurofilament light chain protein (NFL), total and phosphorylated tau (t-tau, p-tau), soluble amyloid precursor proteins alpha and beta (sAPPα, sAPPβ) and amyloid beta (Aβ) fragments 1-42, 1-40 and 1-38. Comparison of the biomarker changes showed a hierarchy of sensitivity in detection and suggested evolving mechanisms with progressive injury. NFL was the most sensitive neuronal biomarker. Its CSF concentration exceeded age-adjusted norms in all HAD patients, 75% of NA CD4<50, 40% of NA CD4 50-199, and 42% of primary infection, indicating common neuronal injury with untreated systemic HIV disease progression as well as transiently during early infection. By contrast, only 75% of HAD subjects had abnormal CSF t-tau levels, and there were no significant differences in t-tau levels among the remaining groups. sAPPα and β were also abnormal (decreased) in HAD, showed less marked change than NFL with CD4 decline in the absence of HAD, and were not decreased in PHI. The CSF Aβ peptides and p-tau concentrations did not differ among the groups, distinguishing the HIV CNS injury profile from Alzheimer's disease. These CSF biomarkers can serve as useful tools in selected research and clinical settings for patient classification, pathogenetic analysis, diagnosis and management.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
HIV infection is a multi-organ disease that involves the central nervous system (CNS). While devastating CNS complications such as HIV-associated dementia and CNS opportunistic infection typically ...manifest years after HIV acquisition, HIV RNA is readily detected in the cerebrospinal fluid in untreated neuroasymptomatic people with HIV, highlighting that HIV neuroinvasion predates overt clinical manifestations. Over the past two decades, increased awareness of HIV infection within the at-risk population, coupled with the accessibility of nucleic acid testing and modern HIV immunoassays, has made the detection of acute and early HIV infection readily achievable. This review aims to summarize research findings on CNS involvement during acute and early HIV infection, as well as the outcomes following the immediate initiation of antiretroviral therapy during this early stage of infection. The knowledge gap in long-term neuroprotection through early ART within the first year of infection will be discussed.
Since the advent of combination antiretroviral therapy (cART), HIV has transformed from a fatal disease to a chronic illness that often presents with milder central nervous system (CNS) symptoms ...laced with related confounders. The immune recovery associated with access to cART has led to a new spectrum of immune-mediated presentations of infection, phenotypically distinct from the conditions observed in advanced disease.HIV-associated neurocognitive disorder (HAND) entails a categorized continuum of disorders reflecting an array of clinical presentation, outcome, and increasing level of severity: asymptomatic neurocognitive impairment (ANI), mild neurocognitive disorder (MND), and HIV-associated dementia (HAD). HAND is defined through an assessment of neurocognitive abilities and functional performance. Progressive neurologic symptoms detected in patients on cART with detectable CSF viral load and a suppressed plasma viral load, or CSF viral load 1 log10 greater than low detectable plasma viral load, characterize a phenomenon termed symptomatic CSF "escape." CD8+ T-cell encephalitis, possibly a form of CNS immune reconstitution inflammatory syndrome, resembles CNS "escape" as it presents in patients despite viral suppression with cART. Cerebral toxoplasmosis, cryptococcal meningitis, and progressive multifocal leukoencephalopathy, are AIDS defining conditions with associated high mortality risk. Cerebral toxoplasmosis and cryptococcal meningitis typically manifest in immunosuppressed patients (<200 CD4+ T-cells/μL), while PML can occur in patients with higher CD4+ T-cell counts.Neurologic conditions are increasingly interconnected with chronic diseases, and classic opportunistic infections may have altered phenotypes in the cART era. However, there exist promising diagnostic methods and therapeutic approaches, as well as associated pitfalls in diagnosis and treatment.
In order to characterize the cellular composition of cerebrospinal fluid (CSF) in a healthy state and in the setting of chronic pleocytosis associated with HIV-1 (HIV) infection, multi-parameter flow ...cytometry was used to identify and quantitate cellular phenotypes in CSF derived from HIV-uninfected healthy controls and HIV-infected subjects across a spectrum of disease and treatment. CD4+ T cells were the most frequent CSF population and the CD4:CD8 ratio was significantly increased in the CSF compared to blood (p = 0.0232), suggesting preferential trafficking of CD4+ over CD8+ T cells to this compartment. In contrast, in HIV-infection, CD8+ T cells were the major cellular component of the CSF and were markedly increased compared to HIV-uninfected subjects (p<0.001). As with peripheral blood, the CSF CD4:CD8 ratio was reversed in HIV-infected subjects compared to HIV-uninfected subjects. Monocytes, B cells and NK cells were rare in the CSF in both groups, although absolute counts of CSF NK cells and B cells were significantly increased in HIV-infected subjects (p<0.05). Our studies show that T cells are the major cellular component of the CSF in HIV-infected and uninfected subjects. The CSF pleocytosis characteristic of HIV infection involves all lymphocyte subsets we measured, except for CD4+ T cells, but is comprised primarily of CD8+ T cells. The reduced proportion of CD4+ T cells in the CSF may reflect both HIV-related peripheral loss and changes in trafficking patterns in response to HIV infection in the central nervous system.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Cerebrospinal fluid (CSF) neurofilament light chain protein (NFL) is a sensitive marker of neuronal injury in a variety of neurodegenerative conditions, including the CNS dysfunction injury that is ...common in untreated HIV infection. However, an important limitation is the requirement for lumbar puncture. For this reason, a sensitive and reliable blood biomarker of CNS injury would represent a welcome advance in both clinical and research settings.
To explore whether plasma concentrations of NFL might be used to detect CNS injury in HIV infection, an ultrasensitive Single molecule array (Simoa) immunoassay was developed. Using a cross-sectional design, we measured NFL in paired CSF and plasma samples from 121 HIV-infected subjects divided into groups according to stage of their systemic disease, presence of overt HIV-associated dementia (HAD), and after antiretroviral treatment (ART)-induced viral suppression. HIV-negative controls were also examined.
Plasma and CSF NFL concentrations were very highly correlated (r=0.89, P<0.0001). While NFL was more than 50-fold lower plasma than CSF it was within the quantifiable range of the new plasma assay in all subjects, including the HIV negatives and the HIV positives with normal CSF NFL concentrations. The pattern of NFL changes were almost identical in plasma and CSF, both exhibiting similar age-related increases in concentrations along with highest values in HAD and substantial elevations in ART-naïve neuroasymptomatic subjects with low blood CD4+ T cells.
These results show that plasma NFL may prove a valuable tool to evaluate ongoing CNS injury in HIV infection that may be applied in the clinic and in research settings to assess the presence if active CNS injury. Because CSF NFL is also elevated in a variety of other CNS disorders, sensitive measures of plasma NFL may similarly prove useful in other settings.
•Plasma NFL is a sensitive marker of neuronal injury•Plasma and CSF NFL concentrations were highly correlated•Plasma NFL is useful to detect active axonal injury in treated and untreated HIV
A sensitive blood biomarker of neuronal injury has long been sought for. Here we describe an ultrasensitive quantification measurement of the axonal neurofilament light chain protein (NFL) in blood. We test this in the setting of HIV brain injury in which cerebrospinal fluid (CSF) NFL has been well characterized and noted to be a reliable biomarker of neuronal injury.
Blood and CSF NFL were highly correlated and measurement of plasma NFL was able to detect both severe and subclinical neuronal injury in HIV.
CSF NFL is elevated in a wide range of additional neurodegenerative settings, so the reported findings likely have broader implications, though this requires additional direct study.
Human immunodeficiency virus type 1 (HIV-1) infection of the central nervous system (CNS) can lead to the development of HIV-1-associated dementia (HAD). We examined the virological characteristics ...of HIV-1 in the cerebrospinal fluid (CSF) of HAD subjects to explore the association between independent viral replication in the CNS and the development of overt dementia. We found that genetically compartmentalized CCR5-tropic (R5) T cell-tropic and macrophage-tropic HIV-1 populations were independently detected in the CSF of subjects diagnosed with HIV-1-associated dementia. Macrophage-tropic HIV-1 populations were genetically diverse, representing established CNS infections, while R5 T cell-tropic HIV-1 populations were clonally amplified and associated with pleocytosis. R5 T cell-tropic viruses required high levels of surface CD4 to enter cells, and their presence was correlated with rapid decay of virus in the CSF with therapy initiation (similar to virus in the blood that is replicating in activated T cells). Macrophage-tropic viruses could enter cells with low levels of CD4, and their presence was correlated with slow decay of virus in the CSF, demonstrating a separate long-lived cell as the source of the virus. These studies demonstrate two distinct virological states inferred from the CSF virus in subjects diagnosed with HAD. Finally, macrophage-tropic viruses were largely restricted to the CNS/CSF compartment and not the blood, and in one case we were able to identify the macrophage-tropic lineage as a minor variant nearly two years before its expansion in the CNS. These results suggest that HIV-1 variants in CSF can provide information about viral replication and evolution in the CNS, events that are likely to play an important role in HIV-associated neurocognitive disorders.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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