CCL2 and dementia: Genetic risks for opiate abuse [40] or neuroAIDS, such as familial predisposition to dementia [41], MOR polymorphisms [42-44] and/or epigenetic changes in MOR [45], as well as polymorphisms in comorbid factors such as CCR5 [46-48], CCL2/MCP-1 [49], apolipoprotein ε (ApoE) allelic variations [50] (the ApoE4 allele has been linked to HIV-1 dementia and neuropathy [51, 52]) and prodynorphin [53-58] may also contribute to the complexity.