Gene transfer by retrovirus vectors occurs only in cells that are actively replicating at the time of infection.

TLDR

Retroviral infection is generally blocked in nonreplicating (stationary‑phase) cells, and although earlier studies suggested that allowing later cell division might permit infection, those experiments used replication‑competent virus and were confounded by viral spread. The study aimed to compare gene transfer efficiency between stationary and replicating rat embryo fibroblasts using a replication‑defective retrovirus vector. A replication‑defective retrovirus vector was employed to infect rat embryo fibroblasts under stationary or replicating conditions. Gene transfer was 100‑fold lower in stationary cells, and inducing division after infection (6 h–10 days post‑infection) did not relieve the block, demonstrating that retroviral infection requires cells to be replicating at the time of infection and underscoring implications for vector use.

Abstract

Previous reports have shown that retrovirus infection is inhibited in nonreplicating (stationary-phase [hereafter called stationary]) cells. Infection of stationary cells was shown to occur when the cells were allowed to replicate at times up to a week after infection, suggesting that an unintegrated retrovirus could persist in a form that was competent to integrate after release of the block to replication. However, those studies were complicated by the use of replication-competent virus, which can spread in the infected cells. We have used a replication-defective retrovirus vector to compare the efficiency of gene transfer in stationary and replicating rat embryo fibroblasts. In agreement with previous results, gene transfer was inhibited 100-fold in stationary versus replicating cells. In contrast to previously reported results, the block to infection could not be relieved by stimulating stationary cells to divide at times from 6 h to 10 days after infection. Thus, for successful retroviral infection, the infected cells must be replicating at the time of infection. These results have important implications for the use of retroviral vectors for gene transfer.