Production of mononuclear cell chemotactic factors during Sindbis virus infection of mice.

Draining lymph node cells of mice infected subcutaneously with Sindbis virus (SV) produced two mononuclear chemotactic factors in vitro. One factor did not require the addition of SV in vitro and was only detectable during the first week after infection. A second factor, resembling lymphocyte-derived chemotactic factor, required the addition of SV in vitro, was first detectable at 3 days, reached a peak at 15 to 18 days, and was gone by 29 days after infection. The production of this factor was virus specific. Diluent-inoculated mice produced no detectable mononuclear chemotactic factors in response to SV. In vitro production of the virus-specific chemotactic factor was dependent on both adherent cells and sensitized Lyt1+ T cells. In vitro production of the spontaneous factor was associated only with adherent cells but also appeared to be T cell dependent, since the lymph node cells from SV-infected athymic nude mice failed to produce either factor. Infectious center assays showed that adherent cells contained infectious SV without replicating it, suggesting the engulfment of virus by macrophages in the lymph node draining the area of virus replication. These cells probably process virus as antigen for presentation to T cells, resulting in local production of chemotactic factors as well as production in more distant sites of viral replication after leaving the lymph node. These virus-stimulated, mononuclear cell-produced chemotactic factors are likely to be of importance in generating the mononuclear inflammatory response.