Pocket proteins p107 and p130 exhibit increased expression in macrophages during SIV encephalitis.

Progression of HIV encephalitis (HIVE) is associated with neuronal damage and loss because of infiltration of infected and/or activated macrophages into the CNS. We have previously observed increased inactivation of the retinoblastoma susceptibility gene product (pRb) by phosphorylation in neurons and glia of HIVE and the simian model of HIVE (SIVE). To determine if other pRb family members are altered in response to increased macrophage-secreted factors, we investigated expression of pRb family members p107 and p130 in SIVE. Both p130 and p107 exhibited increased staining in macrophages, but not neurons, astrocytes or T-cells in SIVE. Increased p130 and p107 immunostaining was not limited to virally infected or PCNA-expressing macrophages. Most p107-positive staining was observed in perivascular macrophages, suggesting p107 may indicate macrophages at a specific stage of differentiation soon after migration. In contrast, cytoplasmic p130 was found in the majority of macrophages present in SIVE cases and may indicate activation as it was not seen in microglia in control CNS. These findings suggest that p107 and p130 are differentially expressed in CNS macrophage populations which may have multiple derivations and/or roles in lentiviral encephalitis.