From the article:
The research team found that even though HIV does not infect neurons, it tries to stop the brain from producing a protein growth factor – mature brain derived neurotrophic factor (mature BDNF) – that Mocchetti says acts like “food” for brain neurons.
[…]
Mocchetti believes that HIV stops production of mature BDNF because that protein interferes with the ability of the virus to attack other brain cells. It does this through the potent gp120 envelope protein that sticks out from the viral shell – the same protein that hooks on to brain macrophages and microglial cells to infect them. “In earlier experiments, when we dumped gp120 into neuronal tissue culture, there was a 30-40 percent loss of neurons overnight. That makes gp120 a remarkable neurotoxin.”