1127 INTERFERON (IFN) PRODUCTION BY MONOCYTE/MACROPHAGES IN RESPONSE TO RESPIRATORY SYNCYTIAL VIRUS (RSV) AND PARAINFLUENZA TYPE 3 (PI3)

Abstract

We have previously reported on RSV and PI3 growth in adherent human peripheral blood mononuclear leukocytes (M's). (Ped Res 18(4), 279A, 1984) with both viruses younger M's (dl post-harvest) are poorer producers of new virus than older M's (d4s7) by ≥ 10 fold. In these experiments we investigated IFN production by M's in response to stimulation with these agents. M's were infected on dl, 2, 4s7 after harvest at a MOI of 0.5-0.6 and washed after 2 hrs of viral adsorption and every 24 hrs. The supernatants were monitored for: antigen production by ELISA; infectious progeny on HEP-2 monolayers; and IFN activity in a VSV plaque-reduction assay. IFN was not detected in 2hr specimens and was maximal at 24hrs after viral exposure. With PI3 IFN production inversely correlated with new virus production. The dl M's produced the highest IFN titers (800 IU) and the least virus (2×10⁴PFU/ml) while the d4 and d7 M's produced lower amounts of IFN (100 and 0 IU) and higher viral titers (3.2-3.4×10⁵PFU/ml). With RSV infection the dl, 2&4 M's produced minimal IFN (<25IU); the d7 M's produced 400 IU. The significance of this IFN production in the d7 M's is uncertain but did not correlate with virus or antigen production, which are lowest on dl and highest on d7. Mock infected cells produced no detectable IFN. The observed IFN activity was successfully blocked with anti-IFN antibody. These findings correlate with the clinical findings that RSV is a poor inducer of IFN while PI can induce IFN production in nasal secretions.

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