ITIH4 and pulmonary arterial hypertension: Because gp120 determines HIV tropism40 and can trigger different signaling pathways upon interactions with specific co-receptors, we leveraged multiple HIV models including existing peripheral blood samples from patients with HIV-PAH enrolled in the NHLBI Lung HIV studies, in vitro approaches, HIV transgenic rats, and bronchoalveolar lavage fluids from PLWH to test the hypothesis that signature sequences in the HIV gp120 gene will reveal specific viral tropism in patients with HIV-PAH45–47.