Maternal COVID-19 infection and the fetus: Immunological and neurological perspectives

Immunoneuropsychiatry is an emerging field about the interaction between the immune and nervous systems. Infection and infection-related inflammation (in addition to genetics and environmental factors) can act as the etiopathogenesis of neuropsychiatric disorders (NPDs). Exposure to COVID-19 in utero may be a risk factor for developing NPDs in offspring in the future. Maternal immune activation (MIA) and subsequent inflammation can affect fetal brain development. Inflammatory mediators, cytokines, and autoantibodies can pass through the placenta and the compromised blood-brain barrier after MIA, leading to neuroinflammation. Neuroinflammation also affects multiple neurobiological pathways; for example, it decreases the production of the neurotransmitter serotonin. Fetal sex may affect the mother's immune response. Pregnant women with male fetuses have been reported to have decreased maternal and placental humoral responses. This suggests that in pregnancies with a male fetus, fewer antibodies may be transferred to the fetus and contribute to males' increased susceptibility/vulnerability to infectious diseases compared to female infants. Here, we want to discuss maternal COVID-19 infection and its consequences for the fetus, particularly the neurological outcomes and the interaction between fetal sex and possible changes in maternal immune responses.

Maternal and Fetal Immune Response to in Utero Stem Cell Transplantation

Purpose of Review

In Utero Hematopoietic Cellular Transplantation (IUHCT) is a promising intervention for the non-toxic treatment of congenital disease that hinges on the assumption of fetal immunologic immaturity and an inability to reject a hematopoietic allograft. However, clinical IUCHT has failed except in cases where the fetus is severely immunocompromised. The current review examines recent studies of engraftment barriers stemming from either the fetal or maternal immune system.

Recent Findings

New reports have illuminated roles for maternal humoral and cellular immunity and fetal innate cellular immunity in the resistance to allogeneic IUHCT. These experimental findings have inspired new approaches to overcome these barriers. Despite these advances, postulates regarding a maternal immune barrier to IUHCT provide an inadequate explanation for the well-documented clinical success only in the treatment of fetal immunodeficiency with normal maternal immunity.

Summary

Characterization of the maternal and fetal immune response to allogeneic IUHCT provides new insight into the complexity of prenatal tolerance. Future work in this area should aim to provide a unifying explanation for the observed patterns of success and failure with clinical IUHCT.

Transfer of maternal immunity and programming of the newborn immune system

As placental mammals, the pregnant women and the fetus have intense and prolonged interactions during gestation. There is increasing evidence that multiple molecular as well as cellular components originating in pregnant women are transferred to the fetus. The transfer of maternal antibodies has long been recognized as a central component of newborn immunity against pathogens. More recent studies indicate that inflammatory mediators, micronutrients, microbial products and maternal cells are transferred in utero and influence the fetal immune system. Together, these multiple signals are likely to form a complex network of interactions that program the neonatal immune system and tune its homeostatic regulation. Maternal disorders, in particular infectious diseases, modify these signals and may thereby alter immunity in early life. Understanding maternal programming of the newborn immune system could provide a basis for interventions promoting child health.

Monitoring fetal immune development in human pregnancies: current concepts and future goals

The vast majority of the current knowledge on immune development in the fetal period has been gained from animal studies, particularly from mouse models. This has led to a great improvement in our current understanding of immune ontogeny. However, it has also become clear that in many ways the mouse model of pregnancy differs from the situation in human pregnancy, such as the degree and importance of trophoblast invasion, the kind of MHC class repertoire of the extravillous trophoblast cells, and differences concerning the development and regulation of T-cells. It will be of paramount importance to develop non-invasive screening methods to assess fetal immune development in humans. The focus of this mini-review is to discuss how prenatal ultrasound evaluation can be used as a tool to monitor fetal immune development in human pregnancies. To identify the fetuses at risk of immune disorders could be the first step to developing prevention strategies in the future.