Normal Anatomy, Histology, and Spontaneous Pathology of the Nasal Cavity of the Cynomolgus Monkey (Macaca fascicularis)

SARS-CoV-2 induces inflammation and intracranial infection through the olfactory epithelium-olfactory bulb pathway in non-human primates

We examined the histopathological changes in the olfactory mucosa of cynomolgus and rhesus macaque models of SARS-CoV-2 infection. SARS-CoV-2 infection induced severe inflammatory changes in the olfactory mucosa. A major histocompatibility complex (MHC) class II molecule, HLA-DR was expressed in macrophage and supporting cells, and melanocytes were increased in olfactory mucosa. Supporting cells and olfactory neurons were infected, and SARS-CoV-2 N protein was detected in the axons of olfactory neurons and in olfactory bulbs. Viral RNA was detected in olfactory bulbs and brain tissues. The olfactory epithelium-olfactory bulb pathway may be important as a route for intracranial infection by SARS-CoV-2.

Nasal anatomy and sniffing in respiration and olfaction of wild and domestic animals

Animals have been widely utilized as surrogate models for humans in exposure testing, infectious disease experiments, and immunology studies. However, respiratory diseases affect both humans and animals. These disorders can spontaneously affect wild and domestic animals, impacting their quality and quantity of life. The origin of such responses can primarily be traced back to the pathogens deposited in the respiratory tract. There is a lack of understanding of the transport and deposition of respirable particulate matter (bio-aerosols or viruses) in either wild or domestic animals. Moreover, local dosimetry is more relevant than the total or regionally averaged doses in assessing exposure risks or therapeutic outcomes. An accurate prediction of the total and local dosimetry is the crucial first step to quantifying the dose-response relationship, which in turn necessitates detailed knowledge of animals' respiratory tract and flow/aerosol dynamics within it. In this review, we examined the nasal anatomy and physiology (i.e., structure-function relationship) of different animals, including the dog, rat, rabbit, deer, rhombus monkey, cat, and other domestic and wild animals. Special attention was paid to the similarities and differences in the vestibular, respiratory, and olfactory regions among different species. The ventilation airflow and behaviors of inhaled aerosols were described as pertinent to the animals' mechanisms for ventilation modulation and olfaction enhancement. In particular, sniffing, a breathing maneuver that animals often practice enhancing olfaction, was examined in detail in different animals. Animal models used in COVID-19 research were discussed. The advances and challenges of using numerical modeling in place of animal studies were discussed. The application of this technique in animals is relevant for bidirectional improvements in animal and human health.

Selected Resources for Pathology Evaluation of Nonhuman Primates in Nonclinical Safety Assessment

Humans and nonhuman primates (NHPs) share numerous anatomical and physiological characteristics, thereby explaining the importance of NHPs as essential animal models for translational medicine and nonclinical toxicity testing. Researchers, toxicologic pathologists, toxicologists, and regulatory reviewers must be familiar with normal and abnormal NHP biological traits when designing, performing, and interpreting data sets from NHP studies. The current compilation presents a list of essential books, journal articles, and websites that provide context to safety assessment and research scientists working with NHP models. The resources used most frequently by the authors have been briefly annotated to permit readers to rapidly ascertain their applicability to particular research endeavors. The references are aimed primarily for toxicologic pathologists working with cynomolgus and rhesus macaques and common marmosets in efficacy and safety assessment studies.

International Harmonization of Nomenclature and Diagnostic Criteria (INHAND): Non-proliferative and Proliferative Lesions of the Non-human Primate (M. fascicularis)

The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions Project (www.toxpath.org/inhand.asp) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP) and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying microscopic lesions observed in most tissues and organs from the nonhuman primate used in nonclinical safety studies. Some of the lesions are illustrated by color photomicrographs. The standardized nomenclature presented in this document is also available electronically on the internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous lesions as well as lesions induced by exposure to test materials. Relevant infectious and parasitic lesions are included as well. A widely accepted and utilized international harmonization of nomenclature for lesions in laboratory animals will provide a common language among regulatory and scientific research organizations in different countries and increase and enrich international exchanges of information among toxicologists and pathologists.

Scientific and Regulatory Policy Committee Points to Consider: Fixation, Trimming, and Sectioning of Nonrodent Eyes and Ocular Tissues for Examination in Ocular and General Toxicity Studies

A Working Group of the Society of Toxicologic Pathology's Scientific and Regulatory Policy Committee conducted a technical and scientific review of current practices relating to the fixation, trimming, and sectioning of the nonrodent eye to identify key points and species-specific anatomical landmarks to consider when preparing and evaluating eyes of rabbits, dogs, minipigs, and nonhuman primates from ocular and general toxicity studies. The topics addressed in this Points to Consider article include determination of situations when more comprehensive evaluation of the globe and/or associated extraocular tissues should be implemented (expanded ocular sampling), and what constitutes expanded ocular sampling. In addition, this manuscript highlights the practical aspects of fixing, trimming, and sectioning the eye to ensure adequate histopathological evaluation of all major ocular structures, including the cone-dense areas (visual streak/macula/fovea) of the retina for rabbits, dogs, minipigs, and nonhuman primates, which is a current regulatory expectation for ocular toxicity studies.[Box: see text].

Olfactory epithelium and ontogeny of the nasal chambers in the bowhead whale (Balaena mysticetus)

In a species of baleen whale, we identify olfactory epithelium that suggests a functional sense of smell and document the ontogeny of the surrounding olfactory anatomy. Whales must surface to breathe, thereby providing an opportunity to detect airborne odorants. Although many toothed whales (odontocetes) lack olfactory anatomy, baleen whales (mysticetes) have retained theirs. Here, we investigate fetal and postnatal specimens of bowhead whales (Balaena mysticetus). Computed tomography (CT) reveals the presence of nasal passages and nasal chambers with simple ethmoturbinates through ontogeny. Additionally, we describe the dorsal nasal meatuses and olfactory bulb chambers. The cribriform plate has foramina that communicate with the nasal chambers. We show this anatomy within the context of the whole prenatal and postnatal skull. We document the tunnel for the ethmoidal nerve (ethmoid foramen) and the rostrolateral recess of the nasal chamber, which appears postnatally. Bilateral symmetry was apparent in the postnatal nasal chambers. No such symmetry was found prenatally, possibly due to tissue deformation. No nasal air sacs were found in fetal development. Olfactory epithelium, identified histologically, covers at least part of the ethmoturbinates. We identify olfactory epithelium using six explicit criteria of mammalian olfactory epithelium. Immunohistochemistry revealed the presence of olfactory marker protein (OMP), which is only found in mature olfactory sensory neurons. Although it seems that these neurons are scarce in bowhead whales compared to typical terrestrial mammals, our results suggest that bowhead whales have a functional sense of smell, which they may use to find prey.

Feline lymphoplasmacytic rhinitis (FLPCR): Severity of inflammation correlates with reduced mucosal IgA expression

Feline lymphoplasmacytic rhinitis (FLPCR) is a rare disease with an unclear pathogenesis characterized by lymphoplasmacytic (LPC) inflammation and progressive tissue destruction. Aims were to evaluate specific FLPCR clinical and pathological features to gain insights into disease pathogenesis. Signalment, clinical signs, serology and 47 pin. h biopsies were retrospectively collected from 33 FLPCR and 3 normal cats. Microscopical lesions and immunohistochemistry results utilizing anti-CD3, anti-CD20, anti-FOXP3, anti-feline-IgA, IgG, IgE and anti-FeLV (p27 and gp70), FIV, FCV and, FHV were scored and most were analyzed statistically. The majority of cats were domestic short haired (26/31) with median age of 11 years and a 0.35 F/M ratio. Serology evidenced 3/22 FIV and 1/22 FeLV positive cats. Immunohistochemistry evidenced 1/33 FeLV-p27 positive cats. Common clinical signs were sneezing (19/24 [79 %]), mucous discharge (13/24 [54 %]) and stertor (10/24 [42 %]). In normal tissues, IgAs were expressed in mucin, apical and lateral cell membrane of columnar cells and in periglandular plasma cells. IgGs were expressed in 20-30 % of columnar cells. Number of clinical signs was statistically significantly higher in female cats (p < 0.0001) and was significantly correlated with chronicity (p = 0.004), and IgG scores (p = 0.01). LPC severity scores correlated positively with infiltration of neutrophils (p = 0.015), gland destruction (p = 0.019) and angiogenesis (p = 0.016) and negatively with fibrosis (p < 0.0001). LPC severity scores were also significantly associated to female sex (p = 0.01) and to IgA (p = 0.03), with higher IgA scores associated to lower LPC scores. FLPCR associated to disruption of mucosal defense mechanisms generating cycles of tissue inflammation, tissue damage and repair with progressive loss of function independent from viral infections.

Mucosa-Associated Lymphoid Tissue and Tertiary Lymphoid Structures of the Eye and Ear in Laboratory Animals

Mucosa-associated lymphoid tissue (MALT) of special senses is poorly described and can be confused with nonspecific mononuclear cell infiltrates and tertiary lymphoid structures (TLS). In the eye, MALT consists mostly of conjunctiva-associated lymphoid tissue (CALT) and lacrimal drainage-associated lymphoid tissue (LDALT). In humans, CALT and LDALT are important components of the normal eye-associated lymphoid tissue (EALT), but EALT is less frequently described in ocular tissues of animals. The EALT are acquired postnatally in preferential mucosal sites, expand with antigenic exposure, form well-developed lymphoid follicles, and are reported to senesce. Lymphoid follicles that are induced concurrently with chronic inflammation are more appropriately considered TLS but must be differentiated from inflammation in MALT. Less understood is the etiology for formation of lymphoid tissue aggregates in the ciliary body, limbus, or choroid of healthy eyes in animals and humans. In the healthy eustachian tube and middle ear of animals and humans, MALT may be present but is infrequently described. Concurrent with otitis media, lymphoid follicles in the eustachian tube are probably expanded MALT, but lymphoid follicles in the middle ear may be TLS. The purpose of this comparative review is to familiarize toxicologic pathologists with MALT in the special senses and to provide considerations for differentiating and reporting eye and ear MALT from immune or inflammatory cell infiltrates or inflammation in nonclinical studies, and the circumstances for reporting TLS in compartments of the eye and ear.

Multisite Analysis of Lesions in the Respiratory Tract of the Rat and Nonhuman Primate (Cynomolgus Monkey) Exposed to Air, Vehicle, and Inhaled Small Molecule Compounds

This paper presents a review of the nature, range, and incidences of background pathology findings in the respiratory tract of cynomolgus monkeys and rats. Data were collected from 81 inhalation studies and 133 non-inhalation studies evaluated at 3 geographically distinct contract research organization facilities. The inhalation studies were comprised of 44 different small molecule pharmaceuticals or chemicals which were also analyzed in order to understand the patterns of induced changes within the respiratory tract. The lung was the most frequently affected organ in both species, with increased alveolar macrophages being the most common background and test article-related finding. In the upper respiratory tract (URT), inflammatory cell infiltrates were the most common background findings in the nasal cavity in monkeys. Induced URT findings were more frequent in rats than monkeys, with squamous metaplasia in the larynx, and goblet cell hyperplasia in the nasal cavity being the most common. Overall, the data revealed a limited pattern of response to inhaled molecules in the respiratory tract, with background and test article-related findings often occurring in the same regions. It is hoped that these data will assist in the interpretation of findings in the respiratory tract induced by novel inhaled small molecule entities.

Use of Nasal Pathology in the Derivation of Inhalation Toxicity Values for Hydrogen Sulfide

Nasal pathology can play an important role in the risk assessment process. For example, olfactory neuron loss (ONL) is one of the most sensitive end points seen in subchronic rodent hydrogen sulfide (H₂S) studies and has been used by several agencies to derive health-protective toxicity values. Alternative methods that rely on computational fluid dynamics (CFD) models to account for the influence of airflow on H₂S-induced ONL have been proposed. The use of CFD models result in toxicity values that are less conservative than those obtained using more traditional methods. These alternative approaches rely on anatomy-based CFD models. Model predictions of H₂S delivery (flux) to the olfactory mucosal wall are highly correlated with ONL in rodents. Three major areas of focus for this review include a brief description of nasal anatomy, H₂S-induced ONL in rodents, derivation of a chronic inhalation reference concentration for H₂S, and the use of CFD models to derive alternative toxicity values for this gas.