CD44 is not required for poliovirus replication in cultured cells and does not limit replication in monocytes.

Although poliovirus receptor is required to mediate poliovirus infection, its role in mediating the tissue specificity of poliovirus replication in natural infections remains unclear due to the presence of this receptor in nonsusceptible cells. It has been hypothesized that CD44 has a role in determining the susceptibility of cell to poliovirus. To test this hypothesis, we determined whether HepG2, a cultured cell line that lacks cell surface CD44, can support poliovirus replication. We found that PV(1) Mahoney, PV(2)W2, and PV(3)Leon strains of poliovirus can replicate in HepG2 cells. Jurkat cells, which also lack CD44, support PV replication. These results suggest that CD44 is not required for poliovirus replication in cultured cells. To examine this question further expression of CD44 in primary human monocytes was examined. Greater than 90% of monocytes express the poliovirus receptor but only 6% of these cells are susceptible to poliovirus infection, making this a good system to study blocks to poliovirus replication. 97% of primary human monocytes reacted with a monoclonal antibody against CD44 that has been shown to block poliovirus binding and replication. This finding suggests that CD44 is present on more cells that poliovirus infects, making CD44 unlikely to be the factor limiting poliovirus replication in human tissues.