Autism-Relevant Behaviors in the Antigen-Driven Mouse Model of Maternal Autoantibody Related Autism

Background: Maternal autoantibodies reactive to fetal brain proteins have been described in a subset of mothers of children with autism spectrum disorder (ASD), but not in mothers of typically developing children, by numerous researchers. Additionally, several animal models have demonstrated the pathological significance of these autoantibodies using passive transfer of human IgG, further supporting their role in the development of ASD. Our lab identified the seven protein antigens for maternal autoantibody related (MAR) ASD, finding antibody reactivity to these proteins in 23% of mothers of children with ASD versus less than 1% in women with typically developing children. Most recently, we have mapped the antigenic epitope sequences recognized by these ASD-specific maternal autoantibodies. Previous animal models have all utilized passive transfer of human IgG yielding promising results but did not reflect a constant exposure to the salient autoantibodies throughout gestation, as would be the case in the clinical setting.

Objectives: This study aimed to generate the first biologically relevant animal model of MAR ASD in order to directly assess the pathologic significance of prenatal exposure to epitope-specific autoantibodies in generating autism-relevant behaviors in offspring.

Methods: Prior to breeding, female C57BL/6J dams were randomly assigned to either MAR-ASD or control treatment. In order to generate epitope-specific autoantibodies that mimic those found in the mothers of children with ASD, the MAR-ASD females received a series of immunizations containing peptide epitope sequences of the four primary target proteins of MAR ASD (lactate dehydrogenase A and B, collapsin response mediator protein 1, and stress-induced phosphoprotein 1) conjugated via Multiple Antigenetic Peptide (MAP) system technologies in addition to adjuvant. Control females were injected with saline only. Following confirmation of autoantibody production in immunized animals by ELISA, females were then paired with male breeders to produce the experimental offspring of interest. Subsequent male and female offspring were tested for a variety of autism-relevant behaviors and developmental milestones (MAR-ASD offspring = 24; Control offspring = 22).

Results: MAR-ASD offspring had significant alterations in development, with significant increases in body weight on postnatal days (PD) 4-14 and head width on PD 12 relative to control offspring (p<0.01). During juvenile reciprocal social interactions on PD 25, MAR-ASD offspring displayed robust deficits in social interactions as compared to control offspring, with significant decreases in the number of front approach, nose-to-nose sniffing, nose-to-anogenital sniffing, push/crawl, and following bouts (p<0.045). Furthermore, significantly more rearing and self-grooming (p<0.0001) bouts were observed in MAR-ASD offspring compared to controls (p<0.0001).

Conclusions: Our results suggest that the presence of autism-specific maternal autoantibodies to fetal brain protein during gestation produce alterations in development and behaviors that are highly relevant to ASD. By generating the MAR ASD-specific epitope antibodies in female mice prior to breeding, our antigen-driven model demonstrates for the first time that these ASD-specific maternal autoantibodies are directly responsible for alterations in behaviors. These findings contribute to the ongoing efforts toward identification of biological markers specific to sub-phenotypes of autism, and the establishment of a highly translatable animal model of ASD.