In this study we evaluated the effects of the anti-microsporidial
exospore monoclonal antibody 3B6, recognizing 3
Encephalitozoon species, Encephalitozoon intestinalis
(Syn. Septata intestinalis), Encephalitozoon cuniculi,
and Encephalitozoon hellem on microsporidial growth in vitro.
Pre-treatment of spores for 24 h with mAb 3B6 resulted in 21–29%
fewer infected host cells 4 days after inoculation of the cultures compared
to cultures pre-treated with medium or an
irrelevant isotype control mAb (P<0·001). Fewer intracellular
spores (1·2±0·2) in infected cells were found when
mAb 3B6 was present in cultures compared to cultures with medium alone
(4·3±0·8) or an irrelevant isotype control mAb
(4·2±0·9; P<0·001). This decrease
appeared not to be dependent on time of exposure, mAb concentration, or
presence
of complement. It is concluded that antibodies, particularly those directed
to potential neutralizing-sensitive epitopes on
spores, may have a role in the control of microsporidial growth in
vitro.