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

Influenza A virus during pregnancy disrupts maternal intestinal immunity and fetal cortical development in a dose- and time-dependent manner

Epidemiological studies link exposure to viral infection during pregnancy, including influenza A virus (IAV) infection, with increased incidence of neurodevelopmental disorders (NDDs) in offspring. Models of maternal immune activation (MIA) using viral mimetics demonstrate that activation of maternal intestinal T helper 17 (TH17) cells, which produce effector cytokine interleukin (IL)-17, leads to aberrant fetal brain development, such as neocortical malformations. Fetal microglia and border-associated macrophages (BAMs) also serve as potential cellular mediators of MIA-induced cortical abnormalities. However, neither the inflammation-induced TH17 cell pathway nor fetal brain-resident macrophages have been thoroughly examined in models of live viral infection during pregnancy. Here, we inoculated pregnant mice with two infectious doses of IAV and evaluated peak innate and adaptive immune responses in the dam and fetus. While respiratory IAV infection led to dose-dependent maternal colonic shortening and microbial dysregulation, there was no elevation in intestinal TH17 cells nor IL-17. Systemically, IAV resulted in consistent dose- and time-dependent increases in IL-6 and IFN-γ. Fetal cortical abnormalities and global changes in fetal brain transcripts were observable in the high-but not the moderate-dose IAV group. Profiling of fetal microglia and BAMs revealed dose- and time-dependent differences in the numbers of meningeal but not choroid plexus BAMs, while microglial numbers and proliferative capacity of Iba1+ cells remained constant. Fetal brain-resident macrophages increased phagocytic CD68 expression, also in a dose- and time-dependent fashion. Taken together, our findings indicate that certain features of MIA are conserved between mimetic and live virus models, while others are not. Overall, we provide consistent evidence of an infection severity threshold for downstream maternal inflammation and fetal cortical abnormalities, which recapitulates a key feature of the epidemiological data and further underscores the importance of using live pathogens in NDD modeling to better evaluate the complete immune response and to improve translation to the clinic.

Exploration of cell type-specific somatic mutations in schizophrenia and the impact of maternal immune activation on the somatic mutation profile in the brain

AIM

Schizophrenia (SZ) is a severe psychiatric disorder caused by the interaction of genetic and environmental factors. Although somatic mutations that occur in the brain after fertilization may play an important role in the cause of SZ, their frequencies and patterns in the brains of patients and related animal models have not been well studied. This study aimed to find somatic mutations related to the pathophysiology of SZ.

METHODS

We performed whole-exome sequencing (WES) of neuronal and nonneuronal nuclei isolated from the postmortem prefrontal cortex of patients with SZ (n = 10) and controls (n = 10). After detecting somatic mutations, we explored the similarities and differences in shared common mutations between two cell types and cell type-specific mutations. We also performed WES of prefrontal cortex samples from an animal model of SZ based on maternal immune activation (MIA) and explored the possible impact of MIA on the patterns of somatic mutations.

RESULTS

We did not find quantitative differences in somatic mutations but found higher variant allele fractions of neuron-specific mutations in patients with SZ. In the mouse model, we found a larger variation in the number of somatic mutations in the offspring of MIA mice, with the occurrence of somatic mutations in neurodevelopment-related genes.

CONCLUSION

Somatic mutations occurring at an earlier stage of brain cell differentiation toward neurons may be important for the cause of SZ. MIA may affect somatic mutation profiles in the brain.