Sex-dependent behavioral alterations in a poly(I:C)-induced maternal immune activation mouse model without segment filamentous bacteria

Maternal immune activation is one of the environmental risk factors for offspring to develop psychiatric disor-ders. A synthetic viral mimetic immunogen, polyinosinic-polycytidylic acid (poly(I:C)), is used to induce maternal immune activation in animal models of psychiatric disorders. In the mouse poly(I:C) model, the ex-istence of segment filamentous bacteria (SFB) in the maternal intestine has been reported to be important for the induction of ASD-related behavioral alterations as well as atypical cortical development called cortical patches. This study aimed to elucidate the effect of a single poly(I:C) injection during embryonic day (E) 9 to E16 on offspring's behavior in the ensured absence of maternal SFB by vancomycin drinking in C57BL/6N mice. The cortical patches were not found at either injection timings with poly(I:C) or PBS vehicle, tested in male or female offspring at postnatal day 0 or 1. Prepulse inhibition was decreased in male adult offspring most strongly at poly (I:C) injection timings later than E11, whereas a modest but significant decrease was observed in female offspring with an injection during E12 to E15. The decrease in social interaction was observed in female offspring most conspicuously at injection timings later than E11, whereas a significant decrease was observed in male offspring with an injection during E12 to E15. In conclusion, this study indicated that behavioral alterations could be induced without maternal SFB. The effect on behavior was substantially different between males and females.