Compared to the normal control group (0.612 ± 0.255, n = 9), OPN levels did not differ significantly with the other groups (HIV + NC, 0.576 ± 0.212, n = 5; HIV+ impaired, 0.682 ± 0.254, n = 5; ALS, 0.524 ± 0.207, n = 5), although there was a trend of increased OPN in the HIV+ MND/HAD group (Fig. 2a). Here, SPP1 is linked to amyotrophic lateral sclerosis.