Paternal Chronic Bacterial-Like Infection Induces Intergenerational Changes in Offspring Anxiety and Cognition

Background Paternal transient infection and immune activation can induce intergenerational behavioural changes via epigenetic modifications. We have recently discovered that acute lipopolysaccharide (LPS) exposure alters offspring's anxiety and depressive traits. However, the effects of chronic paternal immune activation (PIA) remain unclear. Chronic bacterial-like infections are prevalent in global populations and can lead to persistent inflammatory states which may have lasting impacts on progeny. Therefore, it is crucial to understand whether paternal prolonged immune activation in sires induces distinct or more pronounced intergenerational behavioural changes in their offspring. Aims & Objectives We aimed to investigate whether a six-week regimen of escalating LPS doses, modeling chronic bacterial-like infection in male C57BL/6J mice, leads to altered anxiety-like and cognitive outcomes in offspring. This study is significant as it seeks to clarify how chronic paternal immune challenges may program neurobehavioral phenotypes, thereby providing insights into multigenerational implications for human mental health. Method Eight-week-old male C57BL/6J mice received once-weekly escalating intraperitoneal injections of LPS (0.33–0.83 mg/kg) over six weeks. Throughout this period, body weight, food intake, water intake, and clinical severity score were monitored daily to assess health status and confirm chronic immune activation. Four weeks after the final injection—to allow immune-mediated modifications to be incorporated into the germline—treated males were bred with wildtype females. Sperm samples were then collected from sires for small RNA sequencing to characterize the non-coding RNA landscape, given its potential role in the epigenetic transmission of altered phenotypes. Offspring were evaluated for anxiety-like behaviour using the open-field test, light-dark box, and elevated-plus maze, while the cognitive function was assessed with the novel-object recognition and Y-maze tasks. Results Males treated with LPS showed significant weight loss, reduced food and water intake, and elevated clinical severity score 24 hours after each injection compared to controls, indicating chronic immune activation. Their offspring exhibited reduced anxiety, demonstrated by increased exploration in the open field center, more time in lit zones in the light-dark box, and more frequent open-arm entries in the elevated-plus maze. They also spent more time exploring novel objects in the novel-object recognition test, whereas no differences were observed in the Y-maze. Discussion & Conclusions Our findings suggest that paternal chronic bacterial-like infection can alter offspring anxiety-like and cognitive behaviours, emphasizing the significance of paternal health in the intergenerational transmission of psychiatric vulnerabilities. Further analyses of non-coding RNAs will investigate their potential roles in epigenetic inheritance and may inform future novel interventions to mitigate anxiety-related disorders across generations.