# Microglial-Targeted GCPII Inhibition Reverses Neurocognitive Impairment and Synaptic Loss After EcoHIV Infection

## TL;DR

A new drug targeting brain immune cells improves cognitive and social function in mice infected with a model HIV virus.

## Contribution

A microglia-targeted GCPII inhibitor reverses HIV-related cognitive and synaptic deficits at lower doses.

## Key findings

- D-2-PMPA increases cerebrospinal fluid NAAG levels by over 600% in EcoHIV-infected mice.
- D-2-PMPA reverses cognitive and social deficits without affecting locomotion or anxiety.
- The treatment restores synaptic density and dendritic architecture in the prefrontal cortex.

## Abstract

What are the main findings?
D-2-PMPA preferentially accumulates in brain microglia and increases NAAG levels in EcoHIV-infected mice.D-2-PMPA reverses EcoHIV-induced cognitive, social, and synaptic deficits.

D-2-PMPA preferentially accumulates in brain microglia and increases NAAG levels in EcoHIV-infected mice.

D-2-PMPA reverses EcoHIV-induced cognitive, social, and synaptic deficits.

What is the implication of the main findings?
Targeting microglial GCPII represents a promising approach for treating HIV-associated neurocognitive disorders.

Targeting microglial GCPII represents a promising approach for treating HIV-associated neurocognitive disorders.

HIV-associated neurocognitive impairment persists despite combination antiretroviral therapy, largely driven by chronic microglial activation that sustains neuroinflammation and neuronal injury. Activated microglia contribute to HIV-associated brain pathology by releasing proinflammatory mediators that disrupt synaptic integrity and impair cognition. N-acetylaspartylglutamate (NAAG), an abundant neuropeptide that maintains glutamatergic homeostasis, is hydrolyzed by glutamate carboxypeptidase II (GCPII) to glutamate. We previously demonstrated that reduced brain and cerebrospinal fluid NAAG levels in people living with HIV correlate with cognitive impairment, and that pharmacological GCPII inhibition with 2-(phosphonomethyl)-pentanedioic acid (2-PMPA) elevates brain NAAG and improves cognition in EcoHIV-infected mice. To enhance brain delivery and preferentially target activated microglia, we conjugated 2-PMPA to a generation 4 hydroxyl poly(amidoamine) (PAMAM) dendrimer (D-2-PMPA). Our findings demonstrate that D-2-PMPA achieves preferential microglial drug delivery, resulting in a >600% increase in cerebrospinal fluid NAAG levels. At doses 8.3-fold lower than free 2-PMPA, this formulation reversed EcoHIV-induced deficits in social interaction, novel object recognition, and fear-conditioned memory without altering locomotor activity or anxiety-like behavior. D-2-PMPA also restored prefrontal cortex synaptic density and preserved dendritic architecture. Together, these findings demonstrate that microglia-targeted GCPII inhibition represents a potent nanotherapeutic strategy to restore synaptic integrity and cognitive function in HIV-associated neurocognitive impairment.