Hyporeactivity due to infection: recognition of a transferable hyporeactive factor in the serum of encephalomyocarditis virus-infected mice.

As previously reported, mice infected with encephalomyocarditis (EMC) virus progressively develop a state of hyporeactivity to interferon induction as evidenced by an 80% reduction in serum interferon levels produced in response to four different inducers administered 96 h after initiation of infection. In the current report, this hyporesponsiveness was further documented in vitro in peritoneal exudate cells harvested at the time of maximal hyporeactivity (96 h) during EMC virus infection. These peritoneal cell preparations (containing no detectable interferon or virus) produced significantly less interferon than cells from uninfected mice following exposure to Newcastle disease virus or Chikungunya virus. More importantly, hyporeactivity could be transferred to normal peritoneal cells incubated in serum (containing no detectable interferon or virus) from EMC virus-infected mice during the hyporeactive period. Incubation of peritoneal exudate cells with up to a 1:200 dilution of serum from hyporeactive animals still resulted in a significant reduction in the interferon response induced by Newcastle disease virus or Chikungunya virus. Furthermore, it could be shown that this serum hyporeactive factor was effective in mouse cells but not in rabbit, chicken, or human cells.