A US study has found that although HAART benefits neurocognitive function by boosting the immune system, it does not completely protect the central nervous system from damage caused by HIV infection, nor fully repair damage that might occur prior to HIV treatment.
The study, which is published in the November 14th edition of NeuroReport involved 39 HIV-negative controls and 39 HIV-positive individuals. The HIV-positive patients were divided by the investigators on the basis of their HIV viral load.
At baseline, the HIV-positive patients had a mean CD4 cell count of 403 cells/mm3 compared to 798 cells/mm3 in the control patients.
Neurological function was assessed by recording brain activity during the performance of tasks. To do this, investigators recorded individuals’ contingent negative variation (CNV) whilst a reaction time test was performed. CNV is considered to be a measure of anticipation and preparation potential as well as an indication of a person's ability to initiate physical activity. Neuropsychological tests were also employed, and MRI scans were used to measure the size of various parts of the brain in 31 of the HIV-positive patients and 35 of the controls.
Investigators found that the HIV-positive patients had marginally reduced early CNV activity (p=0.07), and significantly lower later CNV activity compared to controls (p
An undetectable viral load was not associated with improved late CNV.
Individuals in both the HIV-positive and control arms of the study were able to perform their study tasks equally well (97% accuracy versus 95% respectively). However, reaction times were significantly quicker in both early and late CNV for the HIV-negative controls.
MRI scans indicated that the HIV-positive patients had significantly less thalamic volume in the brain than the controls (p=0.04), and there was a trend for HIV-positive individuals to have reduced white matter in both the frontal and temporal lobes.
Further analysis revealed that there was a significant difference in thalamic volume between the HIV-positive individuals with a viral load below 50 copies/mL and controls (p=0.02), but not between viraemic individuals and controls. The thalamus acts as a "relay station" for sensory information.
Neuropsychological tests using colour (p=0.03), words (p
The investigators noted several major findings from their study, including:
- CNV activity is significantly lower in HIV-positive patients than in the control arm of the study, and that the successful use of HAART does not seem to alter this.
- HIV-positive individuals taking HAART have reduced thalamic volume compared to controls.
- Patients with a detectable HIV viral load displayed more impairment in neuropsychological tests than both HIV-positive individuals with a controlled viral load and the HIV-negative controls.
The investigators conclude that although HAART benefits neurocognitive performance did to improved immune function, it does not appear to be fully “protect the CNS against HIV-related damage, as evidenced by reduced CNV amplitudes.” However, in the article the investigators acknowledge that medical history prior to infection with HIV and/or the side-effects of HAART could be the cause of brain impairment.
Further information on this website
Treating HIV in the brain and other compartments
Reference
Chao LL et al. Abnormal contingent negative variation in HIV patients receiving antiretroviral therapy. NeuroReport 14: 2111 – 2115, 2003.