Cytokines,Hepatic Fibrosis,and Antiretroviral Therapy Role in Neurocognitive Disorders HIV Related

Abstract

The HIV may trigger a process of neuronal loss and axonal degeneration throughout the brain, which is carried on by the immune system releasing of proinflammatory cytokines, so that chronic inflammation associated with dysregulated innate immune response, glial cell dysfunction, and adverse antiretroviral therapy (ART) effect play an important role causing milder HIV-associated neurocognitive disorders or asymptomatic neurocognitive impairment. All patients have been tested for neurocognitive functioning through a comprehensive, five-domain neuropsychological battery performed in the study. Human cytokine (interleukin [IL]-6, IL-8, IL-18, and tumor necrosis factor [TNF]-α) and brain-derived neurotrophic factor serum levels were quantified using ELISAs, and the hepatic fibrosis was estimated using the noninvasive Fibrosis 4 (FIB-4) score. The study showed a group of 40 HIV-infected individuals and it was observed that almost 40% of HIV⁺ individuals, even if clinically asymptomatic, displayed some degree of neurocognitive dysfunction, compared to normative performance standards, at least in two cognitive areas. The functions affected the most were memory, attention, executive function, and psychomotor processing speed. Three cytokines (IL-6, IL-8, and IL-18) to be significantly linked to test results in specific neurocognitive domain were found. Treatments with nucleoside reverse transcriptase inhibitor plus non-nucleoside reverse transcriptase inhibitor alone were instead associated with poor neurocognitive outcome, especially in verbal fluency, fine motility, and Zung Depression Scale. Elevated value of FIB-4 score showed an opposite connection with cognitive performance as well, underlining the direct association between hepatic steatosis and neurocognitive deficit. The cytokine panel and the FIB-4 score can predict presence or worsening of neurocognitive functions in HIV-infected individuals. An ART switch can be suggested according to the neurocognitive domain involved the most, advising a therapy with protease inhibitors or/and integrase inhibitors to improve fluency, executive functions, and to prevent depression.

Introduction

HIV infects macrophages/microglia in the central nervous system (CNS), causing activation of the monocyte/macrophage system associated with more severe forms of HIV-associated neurocognitive disorders (HAND) in untreated patients.^1

–4 The HAND ranges from asymptomatic neurocognitive impairment (ANI) to minor neurocognitive disorder and HIV-associated dementia (HAD), affecting 20%–50% of HIV-infected individuals, despite viral suppression on antiretroviral therapy (ART).^5,6 Less is known about mechanism(s) underlying the mild forms of HAND that are now prevalent in patients on ART with viral suppression in plasma and cerebrospinal fluid (CSF). Furthermore, the mild forms of HAND appear to have subtypes, probably reflecting distinct, although possibly overlapping, pathophysiological mechanisms. These mechanisms are not yet defined, but may include dysregulated innate immune responses and chronic inflammation associated with persistently elevated type I and II interferon, ongoing low-level viral replication, vascular injury, metabolic abnormalities, glial cell dysfunction, decreased white matter integrity, and adverse effects of ART drugs.^7

–10

One of the hallmarks of neurodegeneration is inflammation in the CNS, and dysregulation of cytokine and chemokine production may play a critical role to perpetuate the inflammatory cycle. Elevated levels of several proinflammatory cytokines, including interleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor (TNF)-α, have been associated to neuroinflammation in neurodegenerative diseases, including Alzheimer's disease,^11,12 Parkinson's disease,^13

–16 and HAND.¹⁷ In particular, elevated levels of cytokines have been reported to correlate with the degree of HAND, and IL-6 and IL-8 were associated to neurocognitive disorders HIV correlated.¹⁸

The lack of HAND-specific biomarkers has delayed the risk identification, diagnosis, and treatment evaluation. Inflammatory cytokines may represent the potential biomarkers because they likely play an important role in the occurrence and persistence of HAND. Previous studies have reported an association between neurocognitive impairment in HIV-infected subjects and increased CSF levels of IL-8, MCP-1, IP-10, and G-CSF,¹⁹ or altered levels of several chemokines and cytokines in the CSF of patients with HAD.²⁰ In HIV-1 patients, several markers of macrophage activation are showed to be correlated to the ability to remember to do something in the future.²¹ Recently, plasma cytokine concentrations are related to attention, executive, and psychomotor functioning associated in patients with HIV/hepatitis C coinfection.^22,23

The aim of this study was to evaluate the relationship between systemic inflammation, cognitive function, fibrosis hepatic, and ART and to understand the role of selected cytokines in HIV-related cognitive impairment using the serum as to determine if these cytokines may represent useful peripheral indices of brain activity.

Materials and Methods

Study design

An analytical transversal study, including 40 Caucasian subjects with HIV infection who were under continuous ART, followed at the Clinic of the Infectious Diseases, Department of Medicine and Science of Ageing, “G. d'Annunzio” University (Chieti-Pescara, Italy).

Patients were clinically stable and virologically suppressed with plasma viral load <40 copies HIV RNA/ml and a CD4⁺ cell count of >300 cells/ml during the 6-month period before the start of the study. The patients had no opportunistic infections during this time and no ART changes in 12 months before the study started. During their baseline visit, blood was taken to perform biochemical and hematological measurements. Clinical assessment included anthropometric measurements and physical examination. It encouraged patients throughout the study to report any adverse events or changes in their condition and to continue with their usual diet and lifestyle. It was excluded from participation from those who (1) were using steroids, growth hormone, testosterone, or any anabolic agent in the previous 6 months, (2) were engaged in drug abuse, (3) had an acute infection or inflammation in the previous 3 months, (4) had kidney disease and reduced glomerular filtration rate, (5) hepatic disease, and (6) previous diagnosis of HAND and neurological disorders.

The study protocol was approved by the Ethics Committee at the University “G. d'Annunzio” Chieti-Pescara (Ethics Committee Project No. 3 the June 2, 2012) and was performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki. Overnight fasting venous blood samples were collected for immunological analyses during the intervention period for analysis.

Neuropsychological examination

All patients underwent a comprehensive neuropsychological battery exploring Memory (Immediate and Delayed recall of Rey's words, Delayed recall of Rey's figure), Attention and working memory (Digit span Forward, Spatial span Forward, Double Barrage), Executive functions (Stroop test, Trail Making Test B, Drawings, and WAIS Digit Symbol), Speed of psychomotor processing (Grooved Pegboard Test for both dominant and nondominant hand), and Language (Letter Fluency). The Zung Depression scale and the Instrumental Activities of Daily Living (IADL) Scale were also administered.^24,25

Full testing took about 40 min. A trained medical doctor administered and scored all tests, adjusting them for age, gender, and education on the basis of normative data available for the Italian population.

Patients were considered as mild cognitively impaired if they scored below the normative cutoff in ≥2 tests according to the standard criteria for composite neuropsychological battery.²⁶

Biochemical analyses

Fasting venous blood samples were collected from the antecubital vein of all participants at their first clinic examination. Plasma levels of glucose, insulin, triglycerides, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma GT, alkaline phosphatase, total bilirubin, direct and indirect bilirubin, albumin, complete blood count, and creatinine were determined. Routine laboratory tests were performed at the Division of Clinical Pathology in the same hospital.

The Fibrosis 4 (FIB-4) score is a noninvasive scoring system based on several laboratory tests that help to estimate the amount of scarring in the liver. FIB-4 Index was determined using the formula proposed by Sterling et al. ²⁷: (age × AST)/(platelets (10⁹/liter) × ALT1/2).

Virologic and immunologic markers

CD4⁺- and CD8⁺-T cell counts were obtained by flow cytometry of lymphocyte subpopulations. Plasma viral load (HIV-RNA) was determined using the “Amplicor” method (Roche Molecular Diagnostics, Milan, Italy) with a detection limit of >40 HIV RNA copies/ml of plasma.

Cytokine measurements

Blood was collected in serum separator vacutainer tubes (BD Biosciences, Oxford, United Kingdom) and centrifuged at 3,000 rpm for 10 minutes. Aliquots of serum were stored at −20°C for later enzyme-linked immunosorbent assay (ELISA) analysis. Human cytokine levels in serum from HIV-infected patients were quantified using specific ELISAs for IL-6, IL-8, Il-18, TNF-α, and brain-derived neurotrophic factor (BDNF). ELISAs were conducted with commercial kits (R&D System) according to the manufacturer's instructions. The plates were read at 450 nm, and the absorbances were transformed to pg/ml, using calibration curves prepared with cytokine standards included in the kits. The intra- and inter-assay reproducibilities were >90%. Duplicate values that differed from the mean by greater than 10% were not considered for further analysis.

Sample size and statistical analyses

The minimum required sample size for the multiple regression on the basis of previously observed data or published results was estimated. The minimum sample size (n = 38) with five predictors was determined to obtain an effect size of 0.4 with at least 80% of desired statistical power level and an alpha error rate of 5%.

The quantitative variables were summarized as mean and standard deviation or median and interquartile range (IQR) according to their distribution and qualitative variables as frequency and percentage. A Shapiro–Wilk's test was performed to evaluate the departures from normality distribution for each variable.

Cytokine concentrations were summarized as median and IQR. Every cytokine concentration was graphically described with box plots: the bottom and top of the box are the first and third quartiles, and the band inside the box is the median. The ends of the whiskers defined the IQR extended by 1.5 times the length of the box toward maximum (upper inner fence) and minimum (lower inner fence) values (Tukey box plot).

The relationship between clinical variables and serum cytokine concentrations was next examined through stepwise multiple linear regression with backward selection. For these analyses, age, body mass index (BMI), FIB-4 score, and treatment were entered as independent measures predicting individual plasma cytokine concentration.

A stepwise multiple linear regression with backward selection was performed to test the relationship between plasma cytokine concentrations and performance on individual neurocognitive test. For these analyses, the five cytokines (BDNF, IL-6, IL-8, IL-18, and TNF-α) were entered as potential predictors into regression models, with the cognitive performance scores treated as dependent measures. In addition, FIB-4 score and treatment were entered into regression analyses as covariates. Three types of treatment were entered in the model as covariates: nucleoside reverse transcriptase inhibitor (NRTI) plus non-nucleoside reverse transcriptase inhibitor (NNRTI), integrase inhibitors (INI), and protease inhibitors (PI). Every treatment type was coded as “1” = present “0” = absent. Leave-one-out cross-validation (LOOCV) was conducted to examine the performance of the linear regression models for predicting neurocognitive score from cytokine levels. The false discovery rate (FDR) correction was used to control the family-wise type I error rate, and an FDR-adjusted p-value less than 0.05 was determined to be statistically significant.

All statistical tests were evaluated at an alpha level of 0.05. Statistical analysis was performed using IBM^® SPSS Statistics v 20.0 software (SPSS, Inc., Chicago, IL).

Results

Study population

A total of 40 patients (35 male), mean age was 47.8 years, and mean education was 12 years, were enrolled. The risk factors for HIV infection were heterosexual transmission 17 (41.5%), men who have sex with men 18 (43.9%), and 6 with a history of previous intravenous drug use (14.6%). All patients, with mean of 8 years (IQR 5–14) of HIV infection, were in ART without therapeutic changes for more than 12 months, and all patients used two NRTI as backbone plus NNRTI in 20 patients, plus PI in 13 patients, and plus INI in seven patients. They had HIV RNA <40 cell/ml and CD4 cell count >300 cell/ml up on 6 months. Furthermore, they had normal BMI with a mean of 23.5 ± 4.2 and a FIB-4 score of 1.10 (IQR 0.81–1.37) that evaluated the hepatic; no patients had hepatitis C virus (HCV)-related chronic hepatitis.

Viroimmunological and blood metabolic markers

All HIV infected patients were treated with combined ART according to currently accepted guidelines. Viral load was persistently undetectable, and the CD4⁺ cell count was of 646 (IQR 523–964) cells/μl. There were no significant differences in the mean serum concentrations of main metabolic parameters, particularly in glucidic and lipidic assessments. Indices of liver and kidney functions did not show any substantial change with respect to range of normality (data not shown).

Neurocognitive examination

All cognitively impaired patients showed a profile type of ANI,²⁶ without significant interference in the everyday life (IADL ≥7). Analyzing the proportion of impairment with the score below the normal cutoff, at each single task, as values of the median did not significantly differ with the normal parameter, but 16 patients (40%) showed two or more pathologic tasks; 4 patients had two pathologic tests, 6 patients had three pathologic tests, and 6 patients had four pathologic tests. The overall test assessment showed that 12.5% of patients had a pathological result of the battery exploring Memory tests, 22.5% of patients showed a pathological test of attention and working memory, the 65.0% was pathologic on executive functions, and 22.5% had low points on speed of psychomotor processing. Only three patients (7.5%) showed significant pathologic data at Zung Depression scores. Raw scores at each task and comparison cutoff are illustrated in Table 1.

Table 1.

Summary of Cognitive Test Performances

	Median	IQR	Normality range/cutoff	Patients with pathologic test, n (%)
Memory
Rey word spiked	42.20	36.65–48.15	>28.53	2 (5.0)
Rey word retarded spiked	7.80	6.55–10.45	>4.69	3 (7.5)
Attention and working memory
Verbal span forward	6.00	5.00–7.00	5.00–9.00	2 (5.0)
Spatial span forward	5.00	5.00–6.00	5.00–9.00	5 (12.5)
Double barrage	0.98	0.94–0.99	>0.92	4 (10.0)
Executive functions
Stroop test E spiked	0.75	0.38–1.75	<36.91	2 (5.0)
Stroop test T spiked	19.50	15.75–22.90	<4.24	—
Trail making test B—T	195.50	104.25–397.50	111.29″–248.89″	5 (12.5)
Trail making test B—E	0.00	0.00–2.00	−0.21–2.39	4 (10.0)
Drawings test	5.00	2.00–6.00	3.85–6.15	13 (32.5)
WAIS digit symbol	9.00	7.00–10.50	>6.00	5 (12.5)
Speed of psychomotor processing
Pegboard test DOM	67.00	60.00–79.00	55.94–74.32	8 (20.0)
Pegboard test non-DOM	75.00	64.50–84.50	59.68–80.30	7 (17.5)
Language
Verbal fluency test spiked	36.30	27.85–41.90	>17.35	1 (2.5)
Depression
Zung depression score	31.00	26.50–38.50	<50.00	3 (7.5)

DOM, dominant; IQR, interquartile range; WAIS, Wechsler Adult Intelligence Scale.

Serum cytokine levels and cognitive impairment

The median value of analyzed cytokine serum levels was of 3946.7 pg/ml (IQR 1935.1–8265.3) for BDNF, 3.37 pg/ml (IQR 2.21–6.35) for IL-6, 7.66 pg/ml (IQR 5.84–9.88) for IL-8, 504.99 pg/ml (IQR 430.93–591.31) for IL-18, and 11.60 pg/ml (IQR 9.91–14.45) for TNF-α (Supplementary Fig. S1; Supplementary Data are available online at www.liebertpub.com/aid). Overall, serum cytokine levels were significantly associated with performances on many neurocognitive measures. IL-6 (p = .023) and IL-18 (p = .049) were negative, associated with reduced verbal function in the domain of working memory. Low IL-8 levels were associated with elevated performance on the Stroop test (p = .008). There was a positive relationship between IL-6 and performance on Trail making (p = .032). Elevated levels of TNF-α were associated a with low score of Wais Digit Span test (p = .024). BDNF serum levels were associated with a long time to performance on Grooved Pegboard Test for the dominant hand test (p = .045). IL-18 serum levels were associated to the performance on Grooved Pegboard Test for the nondominant hand test (p = .015) (Table 2).

Table 2.

Cognitive Test Performance as a Function of Cytokine Levels

	β (95% CI)	p	Adjusted R²	p
Attention and working memory
Verbal span forward			0.165	.013
IL-6	−0.348 (−0.644 to −0.052)	.023
IL-18	−0.298 (−0.595 to −0.002)	.049
Executive functions
Stroop test E spiked			0.431	<.001
IL-8	−0.385 (−0.664 to −0.106)	.008
FIB-4 score	0.674 (0.410 to 0.939)	<.001
Trail making test B—T			0.921	.002
IL-6	0.270 (0.028 to 0.426)	.032
FIB-4 score	0.664 (0.260 to 0.627)	.002
II (treatment)	0.462 (0.367 to 1.595)	.002
Trail making test B—E			0.208	.015
FIB-4 score	0.464 (0.154 to 0.774)	.004
Wais digit span			0.478	<.001
TNF-α	−0.282 (−0.525 to −0.040)	.024
FIB-4 score	−0.523 (−0.775 to −0.270)	<.001
PI (treatment)	−0.274 (−1.025 to −0.059)	.029
Speed of psychomotor processing
Pegboard DOM			0.449	<.001
FIB-4 score	0.795 (0.516 to 1.074)	<.001
BDNF	0.267 (0.006 to 0.529)	.045
INI (treatment)	−0.330 (−1.522 to −0.191)	.013
Pegboard non-DOM			0.522	<.001
INI (treatment)	−0.285 (−1.327 to −0.156)	.015
IL-18	0.283 (0.058 to 0.509)	.015
FIB-4 score	0.650 (0.426 to 0.875)	<.001

Results of stepwise multiple linear regression with backward selection. Cytokines, FIB-4 score, and treatment (NRTI+NNRTI, INI, and PI) variables were entered as predictors of cognitive test performance. NRTI+NNRTI, INI, and PI were coded as “1” = present and “0” = absent. All p-values reported in the table are significant after FDR adjustment with q = 0.05.

BDNF, brain-derived neurotrophic factor; CI, confidence interval; FDR, false discovery rate; FIB-4, fibrosis 4; IL, interleukin; INI, integrase inhibitors; TNF, tumor necrosis factor; NRTI, nucleoside reverse transcriptase inhibitor; NNRTI, non-nucleoside reverse transcriptase inhibitor; PI, protease inhibitors.

Clinical variables and neurocognitive functions

Elevated performance on the Stroop test was associated to high value of FIB-4 score (p < .001). There was a positive relationship between performance on Trail making and FIB-4 score (p = .002) and INI treatment (p = .002). Wais Digit Span test is negatively associated to FIB-4 score (p < .001) and PI treatment (p = .029). Long time to performance on Grooved Pegboard Test for dominant hand test was associated with the FIB-4 score (p < .001) and absences of INI treatment (p = .013). The performance on Grooved Pegboard Test for nondominant hand test was associated with FIB-4 score (p < .001) and absences of INI treatment (p = .015). Reduction of verbal fluency spiked associated with NRTI+NNRTI (p = .030) treatment. Finally, the Zung Depression scale was correlated with NNRTI treatment (p = .048) (Supplementary Table S1).

Serum cytokine levels and clinical variables

Significant association was found between serum cytokine levels and clinical factors. The results of the regression model for each cytokine showed that IL-8 was significantly associated with FIB-4 score (p = .039). Positive association was observed between BMI and IL-18 (p = .006) and BDNF (p = .001). None of the clinical variables was significantly associated with TNF-α and IL-6 serum levels.

The predictive accuracy of these modeling approaches was evaluated by LOOCV; the correlation coefficient for predicted versus observed averaged across all cross-validation runs was statistically significant for all models.

Discussion

Several studies estimate that 40%–50% of HIV⁺ individuals display some degree of neurocognitive dysfunction compared with normal performance standards.^6,28
–30 Although impairment profiles, HIV⁺ individuals³¹ are commonly identified with deficits in the speed of information processing, fine motor speed and dexterity, aspects of learning and memory, and multiple domains of executive functioning.^32,33 There was a study demonstrating HIV⁺ patients with executive function deficits having reduced volumes of several subcortical structures, primarily in the caudate nucleus by magnetic resonance.³⁴ Even though the improvement in neurological outcomes and a reduction of HAD in the era of ART have been obtained, the benefits for HIV cognitive disorders differ between individuals and the type of antiretroviral drug and its penetration. Thus, no conclusive results on the efficacy of ART on cognitive performance improvement or on the best combination to reduce cognitive weakening were obtained. Nevertheless, a meta-analysis revealed more attentional, motor, and executive skill impairments in HIV⁺ individuals treated with ART than in patients treated with monotherapy with PI.^24,35,36

Given the preponderance of cognitive deficits in memory, attention, and executive functions, and speed of psychomotor processing tests in HIV-infected individuals, it was hypothesized that performance in these cognitive domains would be associated with serum cytokine levels. In the present study, the neurocognitive evaluation highlights that most of the patients had test scores within the normal range, although the 40% of patients showed two or more pathologic tasks that allowed us to classify patients in ANI.

Inflammation may be differentially involved in various forms of dementias both in HIV-negative and in HIV-positive patients.^23,37
–39 Several studies found increased levels of inflammatory cytokines in neurocognitive disorders. HIV infection triggers inflammatory responses associated with microglial cell activation inducing release of neurotoxic proinflammatory cytokines.^3,40,41 The inflammatory component of HIV infection in the CNS is regarded as a critical component of HIV-associated brain dysfunction^42
–44; HIV-associated neuronal loss and dysfunction are mediated by increased apoptosis and axonal degeneration throughout the brain.^45,46 Frontal–striatal areas have been primarily involved,^47
–49 consistent with findings of attention-executive and psychomotor impairments common in HIV-infected persons. Neuroimaging approaches, such as magnetic resonance spectroscopy, can detect abnormalities that reflect cerebral inflammation in HIV-infected people.^50,51

The results of this study indicated that higher IL-6 and IL-18 serum levels are associated with bad performances in attention and working memory, expressed with verbal span forward test, so the inflammation degree is correlated with cognitive ability of attention and memory. A strong relation was shown between executive functions and IL-8 serum levels, IL-6, and TNF-α. In literature, these associations between cognitive function and IL-6, IL-8, IL-18, TNF-α, and soluble TNF receptors have been extensively reported.^52,53 In these patients, the IL-18, a proinflammatory cytokine,^54
–56 was associated to a nondominant hand pegboard, so an inflammatory worsening, highlighted by increased IL-18 levels, matched with a worse test performance.

The neurotrophin BDNF has trophic activity and exerts multiple activities on a variety of neurons such as modulation of dendritic branching and spines in the cortex and long-term potentiation in the hippocampus.^57,58 Through these properties, BDNF plays a critical role in learning and memory and preservation of cortical circuits. A reduction of BDNF secretion/activity is responsible for the loss of cortical and hippocampal synapses and fear learning and mirrors the cognitive decline in mental illnesses.^59
–61

In these patients, serum levels of BDNF were not associated to attention, working memory ability, and executive functions. However, BDNF serum levels were associated with lengthening of the times of performance on Grooved Pegboard Test for the dominant hand test. These findings are in line with data showing a correlation between BDNF and preclinical stages of Alzheimer's disease.⁶² Several studies suggest that BDNF exerts neuroprotective effects both in vivo and in vitro by regulating neuronal expression of the HIV coreceptor, CXCR4.⁶³ The debate on the possible source of BDNF in serum may help the interpretation of this data. In fact, blood cells were sources of BDNF, even when no signs of systemic inflammation were evidenced.

These results showed that the executive functions and the speed of psychomotor processing are all associated with the fibrosis hepatic level by FIB-4 score, so that steatosis degree may be in direct connection with neurocognitive deficits. Increased gut permeability and immune activation, both markers of intestinal damage, have been related to increased morbidity due to neurocognitive, cardiovascular, or liver lesions.^64,65 It seems that also high hepatic fibrosis and NNRTI therapy correlate with basal ganglia deficit. There is a study that shows that NNRTIs yielded a marked increase in drug intolerance due to significantly higher concentrations in coinfected patients with an advanced liver fibrosis stage.⁶⁶

The executive functions are considerably associated with ART, in fact a worse test performance is correlated to therapies without PI. Moreover, the Pegboard test evaluates psychomotor processing speed, it mirrors basal ganglia deficit, and it is significantly associated with therapies without INI or PI. A reduction in the verbal fluency was correlated with ART without PI and INI, therefore, based on NRTI and NNRTI schemes. The literature showed that the Zung score for depression is predictably correlated to the ART therapy and the NNRTI use.^67,68 These results confirm the relationship between depression and NNRTI therapy in HIV⁺ patients.

The reason why the prevalence of cognitive impairment is increasing is not understood, especially since contributions of HIV virus have been significantly reduced by successful antiretroviral treatments. Contributing factors for persistent impairment can be neuronal injury occurring before HIV treatment initiation, toxicity of ART, ongoing low-level CNS inflammation with neurologic damage, or comorbid conditions.²⁸

Conclusions

Levels of selected cytokines reflected the activation of the immune response in CNS or periphery. This study is crucial to highlight that serum cytokines can be mechanistic mediators of neurocognitive changes in HIV-infected individuals. Since the same negative relationship between low point with verbal fluency test spiked and use of NRTI+NNRTI was not detected for the therapy with NRTI+PI or NRTI+INI and verbal fluence, it was hypothesized that PI or/and INI therapy may modify verbal fluency and it may also reduce executive function, worsening the cognitive domain compromised the most, and enhance depression risk. In addition, FIB-4 score was retained as a significant predictor of bad neurocognitive functioning, especially executive functions.

Taken together, these results increase existing understanding of the role of cytokines on cognitive function in individuals with HIV infection, suggesting that different cytokines may have a differential impact on neurocognitive imbalance, which may be modified by immunodeficiency and medications.

These results highlight that the evaluation of biomarkers as IL-6, IL-8, and IL-18 levels may help to open a new way to perform an early diagnosis of HAND in HIV.

These preliminary results suggest that in HIV⁺ patients with stable ART, serum cytokine levels, which can be easily accessed, may help the prediction of cognitive function, over and above the contribution of clinical HIV markers, and research should continue to further examine this relationship specifically for identifying patients at risk of neurocognitive problems.

Footnotes

Acknowledgment

This research was supported by the grants from the Italian MIUR (60%, 2012–2013).

Author Disclosure Statement

No competing financial interests exist.

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