SPP1 and amyotrophic lateral sclerosis: OPN levels in microglia were significantly elevated compared to normal controls (0.758 ± 0.376, n = 9) for ALS (1.356 ± 0.848, p < 0.0001, n = 5), HIV+ ANI (1.463 ± 0.934, p < 0.0001, n = 5), and HIV+ MND/HAD (1.467 ± 0.721, p < 0.0001, n = 5), but there were no differences between the disease groups (Fig. 4a).