CXCR4 and HIV infectious disease: Besides the exacerbating impact of opioids on neuroinflammation, neuropathology, and immune modulation, opioids can worsen HIV infection through immunosuppression and facilitate viral seeding of the CNS by damaging the BBB integrity, increasing recruitment and activation of myeloid cells, via the release of chemo-attractants from astrocytes, enhancing CCR5 and CXCR4 expression (reviewed in [160]).