A 28-year-old woman from Mumbai, diagnosed with HIV-1 infection 6 months ago, presents with a CD4+ count of 45 cells/μL despite being on antiretroviral therapy (ART) for 4 months. Viral load is undetectable (<50 copies/mL). She develops acute confusion, headache, and fever. CSF analysis shows elevated protein (180 mg/dL), low glucose (25 mg/dL), and negative bacterial culture. India ink stain of CSF is positive. Which structural component of HIV-1 is responsible for the initial attachment and entry into CD4+ T cells, and how does its loss relate to her current opportunistic infection?