Investigations in animal models of anti-nmdar encephalitis
- Autores: Anna Garcia Serra
- Directores de la Tesis: Josep Dalmau Obrador (dir. tes.)
- Lectura: En la Universitat de Barcelona ( España ) en 2021
- Idioma: español
- Tribunal Calificador de la Tesis: Romana Hoftberger (presid.), Xavier Altafaj Tardío (secret.), Luis Antonio Querol Gutiérrez (voc.)
- Materias:
- Texto completo no disponible (Saber más ...)
- Resumen
Background: Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is a neuronal antibody-mediated disease that associates with prominent neuropsychiatric symptoms and predominantly affects women of childbearing age. Animal models of this disease have enabled the demonstration that patients’ antibodies are pathogenic as they bind to NMDARs and cause their internalization, resulting in a decrease of synaptic levels of these receptors, impairment of synaptic plasticity, memory deficits, and depressive-like and psychotic-like behaviors. These antibodies are class G immunoglobulins (IgG); thus, they can be transferred across the placenta in pregnant patients with anti-NMDAR encephalitis and potentially be detrimental for the fetus/newborn. On the other hand, novel therapeutic strategies to accelerate patients’ recovery are of interest.
Objectives: 1) Report the effects of anti-NMDAR encephalitis in pregnant patients and their babies, 2) develop an animal model of placental transfer of IgG antibodies from patients with anti-NMDAR encephalitis to determine their potential pathogenic effects in the fetus and offspring, 3) investigate whether treatment with a neonatal Fc receptor (FcRn) inhibitor prevents the placental transfer of patients’ IgG and abrogates the antibody-mediated alterations in the previously developed mouse model, and 4) study the potential therapeutic use of a positive allosteric modulator (PAM) of NMDAR (i.e., SGE-301) in a reported mouse model of cerebroventricular infusion of patients’ cerebrospinal fluid (CSF) antibodies.
Methods: Clinical data of patients with anti-NMDAR encephalitis during pregnancy was retrospectively collected from consultations to our group and reviewed from the English literature between 2010 and 2019. To develop the animal model, pregnant C57BL/6J mice were administered via tail vein patients' or controls' IgG from serum on days 14, 15 and 16 of gestation, when the placenta is able to transport IgG and the immature fetal blood-brain barrier is less restrictive to IgG crossing. Using this model, an antibody able to block FcRn-IgG binding required for placental IgG transcytosis was administered via tail vein six hours prior to patients’ or controls’ IgG injections on days 14-16 of gestation to determine whether it could prevent antibody-mediated effects in fetus/offspring. To assess the potential therapeutic effect of SGE-301, adult mice receiving cerebroventricular infusion of patients’ CSF through mini-osmotic pumps during 14 days were treated with a daily subcutaneous administration of this NMDAR PAM. An extensive combination of techniques was used for these studies, including immunocytochemistry with HEK cells or dissociated rat hippocampal neurons, brain immunohistochemical staining, confocal microscopy, electrophysiology on acute hippocampal sections, and comprehensive panels of standardized developmental and behavioral tasks. All studies were conducted with sets of mice at different time points during fetal or postnatal development into adulthood, or during and after antibody infusion.
Results: (1) Up to 90% of newborns from patients who develop anti-NMDAR encephalitis during pregnancy or become pregnant during recovery are healthy at birth, and only 3 of 16 infants had transient neurologic or respiratory symptoms. All of the babies who had assessable follow-up (7–96 months) had normal development. (2) IgG antibodies from patients with anti-NMDAR encephalitis intravenously injected to pregnant mice are transferred across the placenta, reach fetal brain and cause a decrease in NMDAR clusters and in cortical plate thickness, along with a reduction of cell-surface and synaptic NMDAR levels, increased dendritic arborization, a decrease of mature (mushroom-shaped) spine density, microglial activation, thinning of brain cortical layers II–IV with cellular compaction, a delay in innate reflexes and eye opening, depressive-like behavior, deficits in nest building, poor motor coordination, and impaired social-spatial memory and hippocampal plasticity after birth. Remarkably, all these paradigms progressively improved (becoming similar to those of controls) during follow-up without further implications in mature adulthood. (3) In pregnant mice that receive patients’ IgG, treatment with FcRn antibody prevents the IgG from reaching the fetal brain, abrogating the decrease of NMDAR clusters and the reduction of cortical plate thickness that were observed in fetuses from untreated pregnant mice. Moreover, among the offspring exposed in utero to patients’ IgG, those whose mothers are treated with FcRn antibody do not develop the alterations that occur in offspring of untreated mothers, including impairment in hippocampal plasticity, delay in innate reflexes, and visuospatial memory deficits. (4) In mice infused with patients’ CSF, daily subcutaneous administration of SGE-301 prevents the hippocampal memory impairment and synaptic alterations caused by NMDAR antibodies from patients with anti-NMDAR encephalitis.
Conclusions: My studies have contributed to gain insight into the outcome of babies from pregnant patients with anti-NMDAR encephalitis and to unravel the antibody-mediated synaptic alterations underlying the transient developmental and behavioral impairment using a mouse model of placental transfer of patients’ IgG. Overall, these findings have provided potential therapeutic strategies in antibody-mediated diseases of the CNS during pregnancy (i.e., FcRn inhibitor) or in an adult mouse model of anti-NMDAR encephalitis (SGE-301).
