Although the pathogenesis of HIV-PAH is unclear, data from animal models and in vitro human pulmonary microvascular endothelial cells (HPMVEC) implicate the role of HIV viral proteins - namely, transactivator of transcription (Tat), glycoprotein 120 (gp120), and negative factor (Nef) [16]. The gene discussed is S100B; the disease is pulmonary arterial hypertension.