Recombinant gp120 proteins cause apoptosis in Primary Human neurons and reduce BDNF levels.

<p><b>A.</b><i>gp120 mediated neuronal apoptosis</i>. Primary Human Neurons were treated with 1 nM each recombinant gp120 s from representative US-B (HIV-1_Bal), Southern African HIV-1C (HIV-1_96ZM651) and Indian HIV-1C (HIV-1_IN16055) isolates. Percent TUNEL positive cells from 20 different fields in 3x wells per treatment were analyzed and the level of apoptosis was determined. Similar to what was determined using immuno-depletion of gp120 in HIV-1-infected supernatants, the recombinant gp120 from Indian isolate showed a significantly lower percentage of neurotoxicity. <b>B.</b><i>gp120-mediated effect on BDNF release</i>. Supernatants were collected from the primary human neurons following treatment with recombinant gp120s at 6 and 24 hours. Secreted BDNF levels were measured using ELISA and the results were plotted as a percentage of the Control (PBS). Both HIV-1_Bal (US clade-B) and HIV-1_96ZM651 (Southern African clade-C) gp120s resulted in a 40% decrease in secreted BDNF levels at 6 h and a decrease of 60% at 24 h as opposed to HIV-1 IN₁₆₀₅₅ which showed no decrease at 6 h and a 10% decrease at 24 hours compared to Control (PBS). <b>C.</b><i>Neuronal apoptosis caused by recombinant gp120 proteins.</i> Tunnel stained primary human neurons co-stained with anti-neurotubulin antibodies and DAPI (Prolong Gold anti-fade with DAPI, Invitrogen) to verify the direct effect of recombinant gp120 on neuronal death. The four panels show representative fields for neurons treated with PBS and 1 nM recombinant gp120 s from Indian HIV-1C, Southern African HIV-1C and US-B, isolates. Neurons treated with Southern African clade C gp120 and US- Clade B show greater neurotoxicity. (*p<0.05; **<i>p</i><0.01; ***<i>p</i><0.005).