SPP1 and amyotrophic lateral sclerosis: Based on the NeuN/OPN ratio, the ALS group (1.134 ± 0.632) had significantly more NeuN-reactive neurons compared to the normal (0.93 ± 0.59, p = 0.018), HIV+ ANI (0.844 ± 0.614, p = 0.001), and HIV+ MND/HAD groups (0.836 ± 0.438, p = 0.0002), which were similar to each other (Fig. 7b).