Protection against Trichinella spiralis induced by a monoclonal antibody that promotes killing of newborn larvae by granulocytes

Summary Mouse monoclonal antibodies directed against biochemically defined surface antigens of Trichinella spiralis were selected and tested for their ability to destroy parasites in vivo and in vitro. One of these (NIM-M5; IgGl), which recognised a surface component of approximately 64 K molecular weight in newborn larvae (NBL), bound to a surface component of this stage (as shown by fluorescence), and mediated the adherence of rodent eosinophil leucocytes to the surface of living NBL. Following cell adherence mediated by this monoclonal antibody, the worms were killed. This effect was enhanced by fresh normal serum suggesting a role for complement in this phenomenon. A monoclonal antibody directed against a surface component of infective larvae (NIM-M1; IgM) did not promote adherence of cells nor killing of NBL in vitro. The effect of NIM-M5 on the development of NBL to the intramuscular stage was examined. Treatment of NBL with the NIM-M5 monoclonal antibody prior to their injection into mice, together with passive transfer of NIM-M5 for 3 days, significantly reduced (36–51%) the proportion of larvae recovered by digestion 28 days later. Thus a single monoclonal antibody to NBL was able to mediate eosinophil-dependent destruction of worms in vitro and reduce infectivity in vivo. These observations suggest that antibodies capable of mediating eosinophil-induced destruction of nematodes in vitro may also be important in protection against infection.