Pathology of the Brain and the Eye in Severe Acute Respiratory Syndrome Coronavirus-2-Infected Patients: A Review

SARS-CoV-2 Parainfectious Optic Neuropathy: 3 Case Reports and a Review of the Literature

BACKGROUND

Parainfectious optic neuritis is an inflammatory reaction that occurs shortly after an infection without direct invasion by a pathogen. The clinical profile depends on the infectious organism. Cases of SARS-CoV-2 parainfectious optic neuritis have been reported in the literature, but there are no reviews that have applied strict inclusion criteria to more definitively establish the clinical profile associated with SARS-CoV-2.

METHODS

We present 3 new cases of SARS-CoV-2 parainfectious optic neuritis. We also review the literature for definite cases by selecting only those with unambiguous clinical features and MRI findings of optic neuritis, positive SARS-CoV-2 polymerase chain reaction or serology, and the absence of myelin oligodendrocyte-glycoprotein or aquaporin-4 antibodies or other diseases associated with optic neuritis.

RESULTS

We report 2 cases of monophasic, unilateral SARS-CoV-2 parainfectious optic neuritis with optic disc edema and nadir visual acuities of finger counting. We report 1 case of mild SARS-CoV-2 parainfectious optic neuritis that featured cotton wool spots, peripapillary wrinkles and hemorrhages, and recurrence after an initial steroid taper. We identified 6 cases of unambiguous SARS-CoV-2 parainfectious optic neuritis from the literature. Combining our case series with the case reports in the literature, the average age was 42.8 years, 3/9 had bilateral disease, 6/8 had optic disc edema, 8/9 had nadir visual acuity of finger counting or worse, and all recovered visual acuity to 20/40 or better after therapy with steroids.

CONCLUSIONS

SARS-CoV-2 parainfectious optic neuritis has a clinical profile that is atypical for idiopathic optic neuritis but fairly typical of parainfectious forms of optic neuritis with a severely reduced nadir visual acuity, high likelihood of bilaterality, high incidence of optic disc edema, and prompt and significant response to corticosteroids. Further study with long-term follow-up and epidemiologic investigation will be needed to further characterize this clinical entity.

Neuropathological findings in COVID-19: an autopsy cohort

The literature regarding the neuropathological findings in cases of SARS-CoV-2 infection, which causes coronavirus disease 2019 (COVID-19), is expanding. We identified 72 patients who died of COVID-19 (n = 48) or had recovered shortly before death (n = 24) and had autopsies performed at our institution (49 males, 23 females; median age at death 76.4 years, range: 0.0-95.0 years). Droplet digital polymerase chain reaction (ddPCR) for the detection of SARS-CoV-2 was performed (n = 58) in multiple brain regions. In cases the assay was successfully completed (n = 50), 98.0% were negative (n = 49) and 2% were indeterminate (n = 1). Most histologic findings were typical of the patient age demographic, such as neurodegenerative disease and arteriolosclerosis. A subset of cases demonstrated findings which may be associated with sequelae of critical illness. We identified 3 cases with destructive perivascular lesions with axonal injury, one of which also harbored perivascular demyelinating lesions. These rare cases may represent a parainfectious process versus sequelae of vascular injury. The lack of detectable SARS-CoV-2 by ddPCR or significant histologic evidence of direct infection suggests that active encephalitis is not a feature of COVID-19.

The Delta SARS-CoV-2 Variant of Concern Induces Distinct Pathogenic Patterns of Respiratory Disease in K18-hACE2 Transgenic Mice Compared to the Ancestral Strain from Wuhan

Compared to the original ancestral strain of SARS-CoV-2, the Delta variant of concern has shown increased transmissibility and resistance toward COVID-19 vaccines and therapies. However, the pathogenesis of the disease associated with Delta is still not clear. In this study, using K18-hACE2 transgenic mice, we assessed the pathogenicity of the Delta variant by characterizing the immune response following infection. We found that Delta induced the same clinical disease manifestations as the ancestral SARS-CoV-2, but with significant dissemination to multiple tissues, such as brain, intestine, and kidney. Histopathological analysis showed that tissue pathology and cell infiltration in the lungs of Delta-infected mice were the same as in mice infected with the ancestral SARS-CoV-2. Delta infection caused perivascular inflammation in the brain and intestinal wall thinning in K18-hACE2 transgenic mice. Increased cell infiltration in the kidney was observed in both ancestral strain- and Delta-infected mice, with no clear visible tissue damage identified in either group. Interestingly, compared with mice infected with the ancestral strain, the numbers of CD45⁺ cells, T cells, B cells, inflammatory monocytes, and dendritic cells were all significantly lower in the lungs of the Delta-infected mice, although there was no significant difference in the levels of proinflammatory cytokines between the two groups. Our results showed distinct immune response patterns in the lungs of K18-hACE2 mice infected with either the ancestral SARS-CoV-2 or Delta variant of concern, which may help to guide therapeutic interventions for emerging SARS-CoV-2 variants. IMPORTANCE SARS-CoV-2 variants, with the threat of increased transmissibility, infectivity, and immune escape, continue to emerge as the COVID-19 pandemic progresses. Detailing the pathogenesis of disease caused by SARS-CoV-2 variants, such as Delta, is essential to better understand the clinical threat caused by emerging variants and associated disease. This study, using the K18-hACE2 mouse model of severe COVID-19, provides essential observation and analysis on the pathogenicity and immune response of Delta infection. These observations shed light on the changing disease profile associated with emerging SARS-CoV-2 variants and have potential to guide COVID-19 treatment strategies.

Mechanisms of Entry Into the Central Nervous System by Neuroinvasive Pathogens

BACKGROUND

The literature on neurological manifestations, cerebrospinal fluid analyses, and autopsies in patients with COVID-19 continues to grow. The proposed mechanisms for neurological disease in patients with COVID-19 include indirect processes such as inflammation, microvascular injury, and hypoxic-ischemic damage. An alternate hypothesis suggests direct viral entry of SARS-CoV-2 into the brain and cerebrospinal fluid, given varying reports regarding isolation of viral components from these anatomical sites.

EVIDENCE ACQUISITION

PubMed, Google Scholar databases, and neuroanatomical textbooks were manually searched and reviewed.

RESULTS

We provide clinical concepts regarding the mechanisms of viral pathogen invasion in the central nervous system (CNS); advances in our mechanistic understanding of CNS invasion in well-known neurotropic pathogens can aid in understanding how viruses evolve strategies to enter brain parenchyma. We also present the structural components of CNS compartments that influence viral entry, focusing on hematogenous and transneuronal spread, and discuss this evidence as it relates to our understanding of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2).

CONCLUSIONS

Although there is a paucity of data supporting direct viral entry of SARS-CoV-2 in humans, increasing our knowledge of the structural components of CNS compartments that block viral entry and pathways exploited by pathogens is fundamental to preparing clinicians and researchers for what to expect when a novel emerging virus with neurological symptoms establishes infection in the CNS, and how to design therapeutics to mitigate such an infection.

Investigation of the Clinical Laboratory Indexes in COVID-19 Patients with Ocular Symptoms in Iran: A Single-Center Experience

Objectives: Ocular symptoms are prevalent in coronavirus infectious disease 2019 (COVID-19) patients, which may be related to clinical/paraclinical conditions. This study investigated the association between laboratory indexes and ocular symptoms in COVID-19 patients. Methods: In this cross-sectional study, 108 polymerase chain reaction (PCR)-confirmed COVID-19 patients admitted to the Rouhani Hospital, Babol, Iran, were enrolled. Ocular symptoms were investigated using standard ophthalmologic examinations. Routine laboratory investigation was done according to the standard management in patients with COVID-19 infection. Results: The erythrocyte sedimentation rate (ESR) and the serum levels of the blood urea nitrogen (BUN) and creatinine (Cr) were significantly higher in COVID-19 patients with ocular discharge and exudate (P = 0.002, 0.045, 0.046, and 0.027, respectively), while the red blood cell (RBC) and albumin were lower in COVID-19 patients with ocular discharge and exudate (P = 0.029 and 0.027, respectively). The serum levels of creatine kinase (CPK) and iron (Fe) were significantly higher in non-photophobic COVID-19 patients than in photophobic patients (P =0.033 and 0.050, respectively). In contrast, the serum level of procalcitonin was lower than photophobic COVID-19 patients (P = 0.024). The serum level of phosphorus (P) was significantly higher in COVID-19 patients with itchy eyes compared to COVID-19 patients without itchy eyes (P = 0.026). Conclusions: The footprint of laboratory indexes was demonstrated in ocular symptoms of COVID-19 patients. The kidney biomarkers were correlated with ocular discharge and exudate, and electrolytes were associated with tear-related symptoms.