The Differential Early Responses of Human Leukocytes to Influenza Virus and Respiratory Syncytial Virus

The current studies examined very early events associated with activation and initiation of a human immune response after sham exposure or exposure to influenza virus (IAV) versus respiratory syncytial virus (RSV), focusing on the function of a critical accessory cell for lymphocyte responses. Calcium mobilization by monocytes/macrophages was rapid and marked in response to exposure to IAV but was muted in response to RSV. Monocytes/macrophages exposed to IAV showed markedly enhanced expression of Cox-2 mRNA measured soon after exposure, whereas exposure to RSV resulted in reduced expression (relative to control cells). In contrast, expression of the constitutively expressed 2.8 kb Cox-1 mRNA was relatively constant. The 72/74 kDa/pl 7.5 protein doublet (product of the <i>Cox-2</i> gene) was identified in lysates of IAV-exposed monocytes/macrophages but not RSV-exposed monocytes/macrophages. The results demonstrate that human monocytes/macrophages show reduced responses to RSV, similar to previously demonstrated effects of RSV on lymphocyte responses. This relative lack of early responses may contribute substantially to the ability of RSV to re-infect individuals.