The role of CAMKK2 polymorphisms in HIV-associated sensory neuropathy in South Africans

Expression in skin biopsies supports genetic evidence linking CAMKK2, P2X7R and P2X4R with HIV-associated sensory neuropathy

HIV-associated sensory neuropathy (HIV-SN) affects 14-38% of HIV+ individuals stable on therapy with no neurotoxic drugs. Polymorphisms in CAMKK2, P2X7R and P2X4R associated with altered risk of HIV-SN in Indonesian and South African patients. The role of CaMKK2 in neuronal repair makes this an attractive candidate, but a direct role for any protein is predicated on expression in affected tissues. Here, we describe expression of CaMKK2, P2X7R and P2X4R proteins in skin biopsies from the lower legs of HIV+ Indonesians with and without HIV-SN, and healthy controls (HC). HIV-SN was diagnosed using the Brief Peripheral Neuropathy Screen. Biopsies were stained to detect protein gene product 9.5 on nerve fibres and CaMKK2, P2X7R or P2X4R, and were examined using 3-colour sequential scanning confocal microscopy. Intraepidermal nerve fibre densities (IENFD) were lower in HIV+ donors than HC and correlated directly with nadir CD4 T-cell counts (r = 0.69, p = 0.004). However, IENFD counts were similar in HIV-SN+ and HIV-SN- donors (p = 0.19) and so did not define neuropathy. CaMKK2+ cells were located close to dermal and epidermal nerve fibres and were rare in HC and HIV-SN- donors, consistent with a role for the protein in nerve damage and/or repair. P2X7R was expressed by cells in blood vessels of HIV-SN- donors, but rarely in HC or HIV-SN+ donors. P2X4R expression by cells in the epidermal basal layer appeared greatest in HIV-SN+ donors. Overall, the differential expression of CaMKK2, P2X7R and P2X4R supports the genetic evidence of a role for these proteins in HIV-SN.

Neuropathy in Human Immunodeficiency Virus: A Review of the Underlying Pathogenesis and Treatment

This article explores the various causes of the human immunodeficiency virus (HIV), and its associated neuropathy, including the effects of HIV on the nervous system and the long-standing therapy that is often provided to patients with HIV. Several studies regarding the neurotoxic effects of combined antiretroviral therapy (cART) and HIV were reviewed and various hypotheses were discussed. Furthermore, we present the nature of HIV-sensory neuropathy (HIV-SN) among different demographic populations and their subsequent risk factors predisposing them to this condition. It was observed that the incidence of the disease increases in increased survival of the patients as well as in males. Finally, the current approach to HIV-SN and its overlapping features with other causes of peripheral neuropathy have been discussed which demonstrates that a clinical examination is the most important clue for a healthcare professional to suspect the disease. Our main aim was to study the current perspectives and guidelines for diagnosing and managing a patient with HIV-SN to reduce disease prevalence and bring about a more aware frame of mind when following up with an HIV patient.

Brief Report: Polymorphisms in CAMKK2 may Influence Domain-Specific Neurocognitive Function in HIV+ Indonesians Receiving ART

BACKGROUND

Despite effective antiretroviral therapy (ART), milder forms of HIV-associated neurocognitive disorders remain prevalent and are characterized by neuroinflammation, synaptic dysfunction, and neuronal loss.

METHODS

We explore associations between neurocognitive impairment in HIV+ Indonesians and 17 polymorphisms in adjacent genes involved in inflammation and neuronal growth/repair pathways, P2X4R and CAMKK2. HIV+ Indonesians (n = 59) who had received ART for 12 months were assessed to derive Z-scores for the attention, fluency, memory, executive, and motor speed domains relative to local control subjects. These were used to determine total cognitive scores.

RESULTS

No alleles of P2X4R displayed significant associations with neurocognition in bivariate or multivariable analyses. In CAMKK2, rs2686344 influenced total cognitive scores in bivariate analyses (P = 0.04). Multivariable linear regression modeling independently associated rs2686344 with higher executive function Z-scores (P = 0.05) after adjusting for CD4 T-cell counts (adjusted R2 = 0.103, model P = 0.034), whereas rs1653588 associated with lower and rs1718120 (P = 0.05) with higher fluency Z-scores (P = 0.05) after adjusting for education and log10 HIV RNA copies/mL (adjusted R2 = 0.268, model P = 0.001).

CONCLUSIONS

Polymorphisms in CAMKK2 may influence neurocognitive outcomes in specific domains in HIV+ Indonesians receiving ART for 12 months.

Neurocognitive outcomes in indonesians living with HIV are influenced by polymorphisms in the gene encoding purinergic P2X receptor 7

The advent of effective antiretroviral therapy (ART) has decreased the prevalence and severity of HIV-associated neurocognitive disorders (HAND), but milder forms of HAND remain despite optimal treatment. Neuronal injury and loss due to inflammation may mediate HAND. P2X7R encodes purinergic P2X receptor 7 which influences neuroinflammatory pathways and carries polymorphisms associated with sensory neuropathy in HIV patients. We assessed associations between P2X7R polymorphisms and neurocognitive outcomes in Indonesian patients (n ​= ​59) as they commenced ART and after 3, 6 and 12 months. Z-scores were calculated over 5 domains using local controls and evaluated as continuous variables. Optimal linear regression models identified polymorphisms influencing attention, memory, executive function, motor speed and total cognitive function at each time point. rs504677 was associated with lower executive and motor speed Z-scores at 0, 3, 6, and 12 months, and with memory at 0 and 12 months. Memory was positively influenced by carriage of the rs208296 minor allele at 0, 3 and 6 months and by carriage of the rs208307 minor allele at 0 and 12 months. Higher attention Z-scores associated with carriage of minor alleles of rs1653598 after 0 and 12 months. These also positively influenced executive function and motor speed after 0–6 months. This study identifies polymorphisms in P2X7R which influence domain-specific neurocognitive outcomes in HIV+ ​Indonesians prior to and shortly after commencing ART. This implicates purinergic P2X receptor 7 in the pathogenesis of HAND.

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Neurocognitive outcomes in HIV+ ​Indonesians were assessed over one year on ART.

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Overall scores were influenced by age, education and CD4 T-cell counts.

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Five intronic polymorphisms in P2X7R affected scores of selected domains.

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The influence of P2X7R polymorphisms varied over time on ART.

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P2X7R may influence neurocognitive changes on ART.

Large Mitochondrial DNA Deletions in HIV Sensory Neuropathy

OBJECTIVE

The primary objective of this study was to evaluate the correlation of large mitochondrial DNA (mtDNA) deletions in skin samples of people with HIV (PWH) with measures of neuropathy and prior exposure to therapy. We hypothesized that deletions would be associated with neuropathy. As secondary objectives, we determined the correlation of deletion burden with demographic data and neuropathy measures.

METHODS

In this retrospective cohort study, we measured the accumulation of large mtDNA deletions in skin biopsies from PWH recruited as part of the AIDS Clinical Trials Group (ACTG). Our cohort includes individuals with and without sensory neuropathy, as well as individuals with normal or abnormal skin biopsies. Skin biopsies, sural and peroneal nerve conduction studies, total neuropathy score, and deletion burden scores were measured, along with baseline demographic data such as age, CD4+ cell count, viral counts, and prior nucleoside reverse transcriptase inhibitor exposures.

RESULTS

Sixty-seven PWH were enrolled in the study. The mean age of the cohort (n = 67) was 44 years (SD 6.8, range 32-65 years), and 9 participants were female. The mean CD4+ T-cell count was 168 cells/mm³ (SD 97 cells/mm³, range 1-416 cells/mm³) and mean viral load was 51,129 copies/mL (SD 114,586 copies/mL, range 147-657,775 copies/mL). We determined that there was a correlation between the total mtDNA deletion and intraepidermal nerve fiber density (IENFD) (r = -0.344, p = 0.04) and sural nerve amplitude (r = -0.359, p = 0.004).

CONCLUSIONS

Both IENFD and sural nerve amplitude statistically correlate with mitochondrial mutation burden in PWH, specifically in those with HIV-associated sensory neuropathy as assessed by skin biopsy.

Brief Report: Demographic and Genetic Associations With Markers of Small and Large Fiber Sensory Neuropathy in HIV Patients Treated Without Stavudine

Neurotoxic antiretroviral therapy (ART) such as stavudine has been now replaced with safer therapies, reducing the prevalence of neuropathy from 34% to 15% in HIV+ Indonesians. However, it is unclear whether the residual cases display damage to small or large nerve fibers and whether both are influenced by known risk factors, including alleles of CAMKK2 associated with neuropathy in HIV patients. The encoded protein influences the growth and repair of nerve fibers. HIV-positive adults on ART for >12 months without exposure to stavudine were screened for neuropathy using the AIDS Clinical Trials Group Brief Peripheral Neuropathy Screen (BPNS). Large fiber neuropathy was assessed by nerve conduction (NC) and small fiber neuropathy using stimulated skin wrinkling (SSW) applied to the fingers. CAMKK2 alleles were assessed by TaqMan OpenArray technology. Neuropathy diagnoses were more common with SSW than BPNS (49/173 vs 26/185, χ; P = 0.0009), with poor alignment between these outcomes (P = 0.60). NC and BPNS diagnosed neuropathy at similar frequencies (29/151 vs 26/185; P = 0.12) and were aligned (P < 0.0001). In bivariate analyses, all diagnoses were associated with patients' age and persistent HIV replication, with minor effects from CD4 T-cell counts and time on ART. CAMKK2 alleles associated with neuropathy diagnosed with BPNS and SSW but not NC. Multivariable analyses confirmed the importance of age and HIV replication, with distinct CAMKK2 polymorphisms affecting BPNS and SSW. Paradoxically, height was protective against skin wrinkling. Overall the data link CAMKK2 genotypes with small rather than large fiber damage. SSW may reflect pathology distinct from that identified using BPNS.

Immunohistochemical evidence of P2X7R, P2X4R and CaMKK2 in pyramidal neurons of frontal cortex does not align with Alzheimer's disease

Alzheimer's disease (AD) is an incurable neurodegenerative condition resulting in progressive cognitive decline. Pathological features include Aβ plaques, neurofibrillary tangles, neuroinflammation and neuronal death. Purinergic receptors 7 and 4 (P2X7R and P2X4R) and calcium/calmodulin-dependent kinase kinase 2 (CaMKK2) are implicated in neuronal death. We used immunohistochemistry to investigate the distribution of these proteins in neurones from frontal cortex of donors (n = 3/group; aged 79-83 years) who died with and without AD. Neurones were identified morphologically and immunoperoxidase staining was achieved using commercial antibodies. Immunoreactive neurones were counted for each protein by 2-3 raters blinded to the diagnoses. We observed no differences in percentages of P2X7R, P2X4R or CaMKK2 positive neurones (p = 0.2-0.99), but sections from individuals with AD had marginally fewer neurones (p = 0.10). Hence P2X7R, P2X4R or CaMKK2 appear to be expressed in neurones from older donors, but expression does not associate with AD.