Creatine (CR) is essential for normal brain function. A lack of brain CR results in intellectual disability, epilepsy, and language delay in humans. The most common cause of CR deficiency in humans results from mutations in the CR transporter (SLC6A8). Several large deletion models of Slc6a8 have been characterized and are excellent models for global creatine loss. However, other SLC6A8 variants are reported in humans with creatine transporter deficiency (CTD), including missense mutations, deletions, and point mutations resulting in phenotypes ranging from mild to severe in humans. The purpose of these experiments was to determine if mice carrying a point mutation of the Slc6a8 gene showed cognitive deficits, further validating a new model of CTD. These Slc6a8 knock-in (Slc6a8P544L) mice carry the P544L proline to leucine substitution seen in some humans with CTD. The Slc6a8P544L mice have lower overall body weight and lower brain creatine content. Behavioral assessment revealed deficits in spatial memory but not associative or object recognition memory in Slc6a8P544L mice. These findings are in line with clinical findings and other CTD models. In addition, we show that Slc6a8P544L mice are hypoactive in a home-cage environment. These experiments support the use of Slc6a8P544L mice as a valid representative of behavioral changes in human patients and to develop targeted therapies to rescue specific behavioral deficits in CTD.

Fragile X Syndrome (FXS) is the most common inherited form of intellectual disability. It is caused by a trinucleotide expansion in the 5’ UTR of the Fragile X messenger ribonucleoprotein 1 (FMR1) gene leading to loss of expression of Fragile X messenger ribonucleoprotein (FMRP). There is currently no cure for FXS. We developed an FMR1 gene therapy based on an adeno-associated viral vector designed with strong translational potential for future clinical testing. The viral vector was tested in Fmr1 knockout mice using two translationally relevant delivery routes and ages corresponding to in utero, toddler, and adolescent ages in humans. Functional studies showed that the FMR1 gene therapy improved select translational FXS phenotypes spanning three critical domains: sensory hyperexcitability, adaptation to change, and altered brain activity. Expression after intracerebroventricular injection was most prominent in the forebrain, whereas intravenous delivery predominantly led to expression across midbrain and brainstem, suggesting that a dual route may be needed to achieve full brain coverage. Biodistribution analyses further suggested that FMRP expression must be titrated carefully for optimal rescue. In summary, we show that FMR1 gene therapy using delivery routes and vehicles approved for clinical use improves core phenotypes in a mouse model for FXS.

DEK is an estrogen-responsive chromatin-remodeling protein broadly expressed in the murine and human brain, with high expression in memory-relevant regions such as the hippocampus. Prior work from our group and others has linked DEK loss to cellular features associated with Alzheimer's disease and Alzheimer's disease-related dementias. Notably, our group has demonstrated that DEK expression declines with increasing dementia severity in women, but not in age-matched men, suggesting a sex-specific relationship between DEK loss and cognitive vulnerability. Together, these findings support a potential neuroprotective role for DEK; however, functional consequences of DEK loss in vivo were unknown. Here, we examined behavioral and molecular consequences of Dek loss using male and female constitutive knockout (cKO) mice assessed across cognitive, sensorimotor, and affective domains. Across assays, Dek cKO mice of both sexes exhibited intact locomotor activity, anxiety-related behavior, sensorimotor gating, and fear-associated memory. In contrast, female Dek cKO mice displayed selective impairments in cognitive flexibility despite preserved spatial learning and memory, a phenotype not observed in males and indicative of female-specific vulnerability following DEK loss. This sex difference, observed during Morris water maze reversal learning, suggests disruption of hippocampal-prefrontal circuitry. Guided by known sex differences in hippocampal DEK expression, transcriptomic profiling of hippocampal tissue revealed shared and sex-specific consequences of Dek deficiency, including alterations in cytoskeletal organization, neuronal signaling, chromatin regulatory mechanisms, and cellular stress pathways. Collectively, these findings demonstrate sex- and cognitive-domain-specific effects of DEK loss and support further investigation of DEK in executive function and hippocampal-prefrontal cortex-mediated cognition.

Germline pathogenic variants that activate the Ras/mitogen-activated protein kinase (MAPK) pathway cause neurodevelopmental disorders called 'Rasopathies'. Because many affected proteins directly regulate Ras, causative mutations may alter other Ras-dependent pathways in addition to MAPK signaling. To better understand which Rasopathy sequelae result from hyperactivation of downstream MAP kinases, we engineered mice with a gain-of-function mutation in the terminal MAP kinase gene Mapk1, which encodes ERK2 and is associated with the recently described genetic syndrome MAPK1-related Rasopathy (MRR). Mapk1 mutant mice successfully modeled key aspects of the human MRR phenotype, including small stature, facial dysmorphism, and impaired cognitive function. Importantly, they recapitulated phenotypes identified in Rasopathy models with upstream Ras activation, such as neurofibromatosis type 1 (NF1): oligodendrocyte lineage defects, reactive astrogliosis, memory deficits, and hypersensitivity to sensory stimuli. These findings emphasize the importance of downstream MAPK signaling in the pathophysiology of neurocognitive symptoms observed in Rasopathy syndromes.

Attention deficit hyperactivity disorder (ADHD) occurs in 9.8% of U.S. children and has a large hereditary component arising from multiple gene variants. One of these is Latrophiln-3 (LPHN-3). Using CRISPR/Cas9 we deleted exon 3 in Sprague Dawley rats to create a global Lphn3 knockout (gKO). The gKO rats are hyperactive, startle hyper-reactive, impulsive, and have impaired working, spatial, and egocentric learning and memory. Permethrin (PRM) is a widely used pyrethroid insecticide. Acute exposure to PRM alters acoustic startle but its long-term effects from developmental exposure are unknown. The present experiment tested whether Lphn3 heterozygosity interacts with PRM developmental exposure to affect post exposure neurobehavior in rats. We used Lphn3+/- (Het) rats since they have an intermediate phenotype compared with gKO rats that are severely affected (Regan et al., 2022). There were 4 groups: Lphn3-Het + PRM (120 mg/kg daily by gavage from postnatal day (P) 6-20 in 5 mL/kg corn oil (CO)), Lphn3-Het + CO, wildtype (WT) + PRM, and WT + CO. From 25 litters, 20-22 males and 20-22 females of each combination were obtained with not more than one male and one female from any given litter. Adult offspring were tested in an automated open-field for 1 h, in home-cage activity for 72 h, startle (including prepulse inhibition), novel object recognition (NOR), working memory (radial water maze (RWM)), spatial learning (Morris water maze (MWM)), and egocentric learning in the Cincinnati water maze (CWM). On acquisition and reversal probe trials in the MWM and on learning trials in the CWM, Lphn3-Het-PRM rats performed worse than other groups. In open-field, home-cage, startle, NOR, and RWM there were no interactions between Lphn3 and PRM but there were effects of Lphn3 heterozygosity. The results indicate that heterozygosity of the ADHD risk gene Lphn3 when combined with developmental exposure to PRM increases the adverse effects of either one alone.

BACKGROUND/OBJECTIVES:Variations of the latrophilin-3 (Lphn3) gene have been associated with attention-deficit hyperactivity disorder (ADHD). To explore the functional influence of this gene, Lphn3 knockout (KO) rats were generated and have thus far demonstrated deficits in ADHD-relevant phenotypes, including working memory, impulsivity, and hyperactivity. However, inattention remains unexplored. METHODS:We assessed automatic attention in Lphn3 KO (n = 19) and their control line (wildtype/WT, n = 20) through use of the following auditory event-related potentials (ERPs): P1, N1, P2, and N2. We also extended this exploratory study by comparing these same ERPs in spontaneously hypertensive rats (SHRs, n = 16), the most commonly studied animal model of ADHD, to their control line (Wistar-Kyoto/WKY, n = 20). Electroencephalograms (EEG) were recorded using subdermal needle electrodes at frontocentral sites while freely moving rats were presented with five-tone trains (50 ms tones, 400 ms tone onset asynchronies) with varying short (1 s) and long (5 s) inter-train intervals. Peak amplitudes and latencies were analyzed using GLM-mixed ANOVAs to assess differences across genotypes (KO vs. WTs) and strains (SHRs vs. WKYs). RESULTS:The KOs did not demonstrate any significant differences in peak amplitudes relative to the WT controls, suggesting that the null expression of Lphn3 does not result in the development of inefficiencies in automatic attention. However, the SHRs exhibited significantly reduced peak P1 (and peak-to-peak P1-N1) values relative to the WKYs. These attenuations likely reflect inefficiencies in bottom-up arousal networks that are necessary for efficient automatic processing. CONCLUSIONS:Distinct findings between these animal models likely reflect differing alterations in dopamine and noradrenaline neurotransmission that may underlie ADHD-relevant phenotypes.

Radiation is an effective treatment for many brain tumors, but often causes cognitive impairment. Ultra-high dose rate (FLASH) radiotherapy is less toxic to many normal tissues and may protect against adverse cognitive effects of cranial irradiation. Adult male Sprague Dawley rats received a single 18 Gy fraction of cranial irradiation with protons at 1 Gy/s (CV), 60 Gy/s (FLASH-60), 95 Gy/s (FLASH-95), or sham treatment (Control) (n ≥ 22/group). Rats were tested in open-field, acoustic (ASR) and tactile startle (TSR), novelty preference, radial water maze (RWM), Morris water maze (MWM), Cincinnati water maze configurations A and B (CWM-A CWM-B), and novelty tests. Locomotion was decreased and TSR increased in all irradiated rats and ASR increased in FLASH-95 rats compared with Controls. In MWM acquisition and reversal, the CV and FLASH-60 rats had reduced path efficiency but during shift and shift reversal all irradiated rats had increased latencies and reduced path efficiencies compared with Controls. In CWM-A all irradiated rats performed below Controls. There were no differences found in CWM-B, novelty tests, or RWM. In summary, FLASH treatment after 18 Gy cranial proton irradiation did not result in reduced cognitive toxicity.

Genetic knockout (KO) models are valuable tools for understanding biological functions and disease mechanisms. KO models in rats have fallen behind those in mice which limits advances in areas where rats have advantages because they can perform more complex cognitive tasks. Two widely used rat strains are Sprague Dawley (SD) and Long Evans (LE). Creating conditional KO models requires crossing Floxed and Cre lines with the constructs of interest but if they are on different genetic backgrounds, offspring will differ not only on the targeted gene but on genes of the differing background strains. We evaluated strain differences in SD and LE rats for behaviors that included: open-field locomotor activity in familiar and novel contexts, acoustic and tactile startle, egocentric and allocentric learning and memory, conditioned freezing, and working memory. Strain differences were found on open-field activity, startle prepulse inhibition, swimming, Cincinnati water maze (CWM), conditioned freezing, and 72 h home-cage activity. However, in the Morris water maze (MWM), performance was comparable between strains during acquisition and reversal, with LE rats performing slightly better in a third, shift phase with the platform in a third location. These data provide information on similarities and differences between SD and LE rats that may be useful to know when these strains are used to create conditional KO models or in regulatory safety studies.

Cognitive decline with aging, and some neurodegenerative conditions like Alzheimer's disease, disproportionately affects females yet few mechanisms beyond steroid hormone signaling fully explain this sex-specific vulnerability. The chromatin-remodeling DEK protein, upregulated by estrogen and progesterone and broadly expressed in the brain, including the hippocampus, may be one such mechanism. We have previously linked DEK loss with indices of neuronal dysfunction, including increased DNA damage, impaired neurite development, and apoptosis, suggesting a potential neuroprotective role. Here, we investigated the molecular and behavioral consequences of Dek loss in vivo. Female Dek constitutive knockout (cKO) mice exhibited a sex-specific behavioral phenotype, with impairments in sensorimotor gating, as measured by pre-pulse inhibition, and in reversal learning in the Morris Water Maze. These findings are suggestive of deficits in pre-attentive sensory processing and cognitive flexibility, respectively. Notably, these cognitive deficits were not observed in male Dek cKO mice and were not attributable to differences in general learning ability, locomotor activity, or anxiety-like behavior. The absence of impairment in object recognition and conditioned fear learning and memory in females suggests that the effects of DEK loss are task-specific and likely brain region-specific. Transcriptomic analysis of hippocampal tissue revealed differentially expressed genes related to inflammation, metabolism, and neuropeptide signaling in all Dek-cKO mice, along with a distinct female-specific transcriptomic profile indicative of impaired neuronal function. Combined, we report for the first time that DEK supports certain aspects of cognitive function, particularly in females. These data may be relevant for understanding sex differences in some cognitive disorders.

We examined DA activity in the medial prefrontal cortex (mPFC) and nucleus accumbens core (NAcc) in two Different Rat Models of Attention-Deficit/Hyperactivity Disorder: Spontaneously Hypertensive Rats (SHR) Versus Lphn3 Knockout Rats. We examined baseline stimulation-evoked phasic DA release, half-life, and DA autoreceptor (DAR) functioning in the mPFC and NAcc, as well as the response to nomifensine (10 mg/kg, IP), a DA transporter (DAT) blocker, on these measures in the NAcc. Both rat models were hypodopaminergic, with notable regional and mechanistic differences. The SHRs displayed decreased DA release in the NAcc compared to their control strain (i.e., WKY rats), with no differences in the mPFC, leading a much lower NAcc-to-PFC DA release ratio in SHRs compared to controls suggesting an imbalance in DA transmission between these regions. The Lphn3 KO rats were considered hypodopaminergic based on the reduced summed DA release in the mPFC and NAcc compared to WT controls, although differences were not observed when examining each site independently. Lphn3 KOs displayed increased DA half-life in the mPFC compared with Lphn3 WT rats, an indication of decreased DAT reuptake, with no differences in the NAcc. DAT blockade by nomifensine had a similar effect on DA release in the NAcc of SHRs and WKYs, but increased DA release in the NAcc of Lphn3 KOs to a greater extent than in WTs. These results suggest that the efficacy of pharmacotherapies used to treat externalizing disorders such as ADHD and/or SUD, likely differ between SHRs and Lphn3 KO rats.

The prevalence of attention deficit hyperactivity disorder (ADHD) is 9.8 % in U.S. children. Several variants of Latrophiln-3 (LPHN-3) are associated with ADHD. Using CRISPR/Cas9 we deleted exon 3 in rats to create a global Lphn3 knockout. These rats are hyperactive, startle hyper-reactive, impulsive, and have impaired working, spatial, and egocentric learning and memory. Deltamethrin (DLM) is a widely used pyrethroid insecticide. Several epidemiological studies report an increase in ADHD prevalence in children exposed to pyrethroids. Developmental exposure to DLM in rats results in multiple behavioral deficits. The present experiment tested whether Lphn3 disruption interacts with developmental DLM exposure. Because Lphn3-/- rats are severely impaired, we used Lphn3+/- (Hets) because they have an intermediate phenotype. Rats were treated by gavage once/day from postnatal day 6-20 with DLM resulting in four groups: Lphn3-Het + DLM (1.0 mg/kg), Lphn3-Het + Corn Oil (CO), Lphn3+/+ (wildtype: WT) + DLM, and WT + CO. From 31 litters, 19-27 offspring per genotype per treatment per sex were obtained with not more than 1 rat of each group and sex used from any one litter. Adult offspring were tested for exploration (open-field), 72-h home-cage activity, startle, novel object recognition (NOR), radial water maze (RWM), Morris water maze (MWM), and Cincinnati water maze (CWM). On MWM acquisition trials and the reversal probe trial, Lphn3-Het-DLM rats performed worse than other groups. This group also was impaired learning the CWM. No interactions were found for open-field, home-cage, startle, NOR, or RWM. The results show that the ADHD risk gene Lphn3 in combination with developmental DLM exposure has selective adverse effects compared with either factor alone.

Latrophilin-3 (LPHN3) is a brain specific adhesion G-protein coupled receptor associated with elevated risk of attention deficit hyperactivity disorder (ADHD). We developed a global Lphn3 knock-out (gKO) rat using CRISPR/Cas9 to delete exon-3. Here we report the development of a floxed Lphn3 rat crossed with tyrosine hydroxylase (Th-Cre) rats to create a conditional Lphn3 KO rat specific for catecholaminergic-positive cells. The gKO rats are hyperactive and have egocentric and allocentric navigation deficits but showed sparing of conditioned contextual and novel object recognition memory. Here we compared gKO and cKO rats controlling for litter effects. Both gKO and cKO rats were hyperactive and were impaired in egocentric navigation in the Cincinnati water maze (CWM) with deficits greater in gKO rats. The gKO rats were impaired in allocentric navigation in the Morris water maze (MWM) whereas cKO rats were only slightly affected compared with WT, cre, and floxed rats. Striatal tyrosine hydroxylase and dopamine D1 receptors were not significantly different in either model, nor were NMDA-NR1 or NMDA-NR2 in the hippocampus. We previously showed, however, that dopamine is released more rapidly in the striatum of gKO rats by fast-scan cyclic voltammetry. The cKO model shows an important role of catecholamines in the phenotype of LPHN3 disruption and add evidence that this synaptic protein plays a role in neuroplasticity that are consistent with ADHD. ### Competing Interest Statement The authors have declared no competing interest.

For decades, regulatory guidelines for safety assessment in rodents for drugs, chemicals, pesticides, and food additives with developmental neurotoxic potential have recommended a single test of learning and memory (L&M). In recent years some agencies have requested two such tests. Given the importance of higher cognitive function to health, and the fact that different types of L&M are mediated by different brain regions assessing higher functions represents a step forward in providing better evidence-based protection against adverse brain effects. Given the myriad of tests available for assessing L&M in rodents this leads to the question of which tests best fit regulatory guidelines. To address this question, we begin by describing the central role of two types of L&M essential to all mammalian species and the regions/networks that mediate them. We suggest that the tests recommended possess characteristics that make them well suited to the needs in regulatory safety studies. By brain region, these are (1) the hippocampus and entorhinal cortex for spatial navigation, which assesses explicit L&M for reference and episodic memory and (2) the striatum and related structures for egocentric navigation, which assesses implicit or procedural memory and path integration. Of the tests available, we suggest that in this context, the evidence supports the use of water mazes, specifically, the Morris water maze (MWM) for spatial L&M and the Cincinnati water maze (CWM) for egocentric/procedural L&M. We review the evidentiary basis for these tests, describe their use, and explain procedures that optimize their sensitivity.

Developmental stress, including low socioeconomic status (SES), can induce dysregulation of the hypothalamic-pituitary-adrenal axis and result in long-term changes in stress reactivity. Children in lower SES conditions often experience more stress than those in other SES groups. There are multiple model systems of early environmental stress (EES), one of which is reduced cage bedding. Here we tested the effects of both prenatal and lactational EES in rats on a range of long-term behavioral and cognitive outcomes. There were persistent reductions in body weight in the EES rats in both sexes. The behavioral results showed no effects on learning and memory using tests of spatial learning or cognitive flexibility in the Morris water maze, egocentric learning in the Cincinnati water maze, or working memory in the radial-arm maze. There were no effects on basic open-field activity, elevated zero-maze, or forced swim test, but EES rats had reduced time in the dark side of the light/dark test. When rats were drug challenged in the open-field with d-amphetamine or MK-801, there were no differential responses to d-amphetamine, but the EES group under responded compared with the drug-induced hyperactivity in the control group in both males and females. The objective was to establish a developmental stress model that induced cognitive deficits and to the extent that this method did not cause such effects it was not the model we sought. However, the data showed several long-term effects of EES, including the reduced response to the irreversible NMDA antagonist MK-801. This effect merits further investigation.

The creatine (Cr)-phosphocreatine shuttle is essential for ATP homeostasis. In humans, the absence of brain Cr causes significant intellectual disability, epilepsy, and language delay. Mutations of the creatine transporter (SLC6A8) are the most common cause of Cr deficiency. In rodents, Slc6a8 deletion causes deficits in spatial learning, novel object recognition (NOR), as well as in contextual and cued freezing. The mechanisms that underlie these cognitive deficits are not known. Due to the heterogeneous nature of the brain, it is important to determine which systems are affected by a loss of Cr. In this study, we generated mice lacking Slc6a8 in GABAergic neurons by crossing Slc6a8FL mice with Gad2-Cre mice. These Gad2-specific Slc6a8 knockout (cKO) mice, along with the ubiquitous Slc6a8 KO (Slc6a8-/y), Gad2-Cre+, and wild-type (WT) mice were tested in the Morris water maze, NOR, conditioned freezing, and the radial water maze. Similar to the Slc6a8-/y mice, cKO mice had reduced contextual and cued freezing compared with WT mice. The cKO mice had a mild spatial learning deficit during the reversal phase of the MWM, however they were not as pronounced as in Slc6a8-/y mice. In NOR, the Gad2-Cre mice spent less time with the novel object, similar to the reduced novel time in the cKO mice. There were no changes in radial water maze performance. Slc6a8 deletion in GABAergic neurons is sufficient to recapitulate the conditioned freezing deficits seen in Slc6a8-/y mice.

IntroductionImpulsivity is a symptom of attention-deficit/hyperactivity disorder (ADHD) and variants in the Lphn3 (Adgrl3) gene (OMIM 616417) have been linked to ADHD. This project utilized a delay-discounting (DD) task to examine the impact of Lphn3 deletion in rats on impulsive choice. “Positive control” measures were also collected in spontaneously hypertensive rats (SHRs), another animal model of ADHD.MethodsFor Experiment I, rats were given the option to press one lever for a delayed reward of 3 food pellets or the other lever for an immediate reward of 1 pellet. Impulsive choice was measured as the tendency to discount the larger, delayed reward. We hypothesized that impulsive choice would be greater in the SHR and Lphn3 knockout (KO) rats relative to their control strains - Wistar-Kyoto (WKY) and Lphn3 wildtype (WT) rats, respectively.ResultsThe results did not completely support the hypothesis, as only the SHRs (but not the Lphn3 KO rats) demonstrated a decrease in the percent choice for the larger reward. Because subsequent trials did not begin until the end of the delay period regardless of which lever was selected, rats were required to wait for the next trial to start even if they picked the immediate lever. Experiment II examined whether the rate of reinforcement influenced impulsive choice by using a DD task that incorporated a 1 s inter-trial interval (ITI) immediately after delivery of either the immediate (1 pellet) or delayed (3 pellet) reinforcer. The results of Experiment II found no difference in the percent choice for the larger reward between Lphn3 KO and WT rats, demonstrating reinforcement rate did not influence impulsive choice in Lphn3 KO rats.DiscussionOverall, there were impulsivity differences among the ADHD models, as SHRs exhibited deficits in impulsive choice, while the Lphn3 KO rats did not.

Recent studies suggest that ultra-high dose rates of proton radiation (>40 Gy/s; FLASH) confer less toxicity to exposed healthy tissue and reduce cognitive decline compared with conventional radiation dose rates (~1 Gy/s), but further preclinical data are required to demonstrate this sparing effect. In this study, postnatal day 11 (P11) rats were treated with whole brain irradiation with protons at a total dose of 0, 5, or 8 Gy, comparing a conventional dose rate of 1 Gy/s vs. a FLASH dose rate of 100 Gy/s. Beginning on P64, rats were tested for locomotor activity, acoustic and tactile startle responses (ASR, TSR) with or without prepulses, novel object recognition (NOR; 4-object version), striatal dependent egocentric learning ([configuration A] Cincinnati water maze (CWM-A)), prefrontal dependent working memory (radial water maze (RWM)), hippocampal dependent spatial learning (Morris water maze (MWM)), amygdala dependent conditioned freezing, and the mirror image CWM [configuration B (CWM-B)]. All groups had deficits in the CWM-A procedure. Weight reductions, decreased center ambulation in the open-field, increased latency on day-1 of RWM, and deficits in CWM-B were observed in all irradiated groups, except the 5 Gy FLASH group. ASR and TSR were reduced in the 8 Gy FLASH group and day-2 latencies in the RWM were increased in the FLASH groups compared with controls. There were no effects on prepulse trials of ASR or TSR, NOR, MWM, or conditioned freezing. The results suggest striatal and prefrontal cortex are sensitive regions at P11 to proton irradiation, with reduced toxicity from FLASH at 5 Gy.

The ongoing epidemic caused by the coronavirus SARS-CoV-2 is characterized by a variety of pathologic processes within the syndrome of COVID-19. Usually beginning as an upper respiratory infection with potential progression to a pneumonitis, many cases of COVID-19 that show minimal signs or symptoms initially may develop adverse systemic sequelae later, such as widespread thrombo-embolic phenomena, systemic inflammatory disorders (especially in children), or vasculitis. Here, we present a patient who suffered a sudden cardiac death following persistent SARS-CoV-2 viral positivity for four-and-one-half months after a mild clinical viral course. At routine autopsy, a remarkable plasma cell-rich necrotizing aortitis was uncovered. The aortic intima displayed diffuse, circumferential ongoing chronic intimal edema, inflammation, and neo-vascularization. The plasma cell-rich inflammatory process also involved the origin of the left main coronary artery (LM) causing a coronary arteritis accompanied by subacute, stenosing intimal vascular smooth muscle cell (VSMC) proliferation resulting in acute myocardial necrosis as a cause of death. A similar vasculitis and plaque were noted during the routine autopsy at the ostium of the celiac artery; vasculitis was not found systemically or in smaller caliber vessels. Through a variety of techniques including extensive histopathologic and immunohistochemical characterization, immunostaining localization of viral antigen, and transmission electron microscopy we present highly suggestive evidence that this unique necrotizing, plasma cell-rich aortitis is a rare sequela of COVID-19.