Hepatitis C virus impairs brain function in HIV-positive people

Hepatitis C virus (HCV) can travel into the brain and replicate there causing significant cognitive impairment in people with HIV co-infection, say researchers at the San Diego HIV Neurobehavioral Research Center in a study published in the July edition of the Journal of Infectious Diseases.

There has recently been a surge of research interest in a possible link between HCV infection and cognitive impairment after HCV DNA was discovered in brain tissue and cerebrospinal fluid.

HCV levels in the blood are known to be linked with the severity of memory impairment in HCV-infected individuals but it has been difficult to study virus levels in the central nervous system (CNS).

This study looks specifically at people with both HIV and HCV infection, as the immune suppression associated with HIV infection can make it easier for HCV to replicate.

Researchers studied post-mortem brain tissue from 12 people who had HCV/HIV coinfection and 13 HIV-infected people who were HCV-negative.

They looked for HCV ribonucleic acid (RNA) - which is the template for HCV DNA and therefore evidence that the virus has been actively replicating.

They found HCV RNA in the brain tissue of all the HIV/HVC-coinfected individuals but none of the HCV-negative individuals.

Antibodies to HCV were also found in the CNS of people with the coinfection.

The researchers then looked back at the cognitive abilities of the individuals, assessed before death, and found that presence of HCV RNA was significantly associated with considerable cognitive impairment as well as the presence of brain issue inflammation, or encephalitis.

The researchers conclude that their results support the idea that replicating HCV is capable of causing neurological damage is present in people also infected with HIV.

Exactly how the virus causes this damage is unclear but this study has also found evidence that HCV virus may be found in a specific type of brain cell called the astroglia.

These cells are involved in a huge range of activities in the brain, including the transportation of a neurotransmitter called glutamate.

Previous studies have suggested that glutamate transport is defective in people with HCV infection and HIV is also known to impair glutamate transport.

This suggests that HCV and HIV might be working together to block clearance of glutamate from the synapses of people with the coinfection, possibly leading to structural damage in the brain and therefore cognitive impairment, the authors conclude.