Literature Analysis: Multiplex Fluorescence IHC Empowers Research on SARS-CoV-2 Brain Invasion Mechanisms

1. Literature Information

Key Research Teams: Alkiko Iwasaki Team (Yale University), Kristian Pietras Team

Research Focus: Exploring the mechanism of SARS-CoV-2 invading the brain, including the target cells of infection, the pathway of central nervous system (CNS) entry, and the induced neuroinflammatory response and blood-brain barrier damage

Key Technology: Multiplex Fluorescence Immunohistochemistry (mIHC), human brain organoid model, ACE2 transgenic SARS-CoV-2 mouse model, clinical sample pathological analysis

Sample Information: Frontal cortex sections of COVID-19 patients, brain samples of non-infected control patients, human brain organoids, ACE2 transgenic mouse brain tissues

Key Product Utilized: Multiplex Fluorescence IHC Staining Kits (4-color to 7-color) and personalized technical services from the Absin product line of ANT BIO PTE. LTD.

2. Research Background

Coronavirus Disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has persisted for nearly four years since its outbreak in late 2019 and remains unresolved. Although COVID-19 is primarily recognized as a respiratory disease, clinical observations have revealed that some patients exhibit neurological symptoms such as altered consciousness, epilepsy, and sensory disturbances. These findings have led scientists to hypothesize that SARS-CoV-2 may also target the brain, highlighting the urgent need to clarify the mechanism of SARS-CoV-2 neuroinvasion to provide a basis for the diagnosis and treatment of COVID-19-related neurological complications.

Traditional research techniques are limited in comprehensively analyzing the spatial distribution of virus-infected cells, immune cell infiltration, and blood-brain barrier integrity in brain tissues. Multiplex Fluorescence Immunohistochemistry (mIHC) technology, which enables simultaneous detection of multiple molecular markers on a single tissue section, has become an indispensable tool for deciphering the complex pathological processes of SARS-CoV-2 brain invasion. It provides rich spatial and quantitative information for accurately identifying infected cells, tracing infection pathways, and evaluating pathological damage.

3. Core Research Findings

3.1 Initial Evidence of SARS-CoV-2 Neuroinvasion

In March 2021, the Alkiko Iwasaki team from Yale University, using human brain organoids, ACE2 transgenic SARS-CoV-2 mouse models, and clinical analysis, first clearly demonstrated that SARS-CoV-2 can directly infect neurons. This infection induces metabolic disorders and nervous system hypoxia, ultimately leading to neuronal apoptosis. The study confirmed the neuroinvasive ability of SARS-CoV-2 and indicated that this process is ACE2-dependent, involving metabolic changes and local vascular alterations.

3.2 Brain Pericytes: The "Window" for SARS-CoV-2 Entry into the CNS

As early as the beginning of the pandemic, researchers had confirmed that angiotensin-converting enzyme 2 (ACE2) is the main receptor for SARS-CoV-2 to enter host cells. In October 2021, the Kristian Pietras team published a study titled "Infection of Brain Pericytes Underlying Neuropathology of COVID-19 Patients," which applied mIHC technology to study the effects of SARS-CoV-2 on the brain from a pathological perspective.

The team performed 4-color multiplex fluorescence staining on frontal cortex sections of a COVID-19 patient, targeting ACE2, CD31+ vascular endothelial cells, and PDGFRβ+ perivascular cells. The results showed that ACE2 was exclusively expressed by pericytes, suggesting that pericytes may be the target cells of SARS-CoV-2 in the brain.

SARS-CoV-2 is a positive-strand, single-stranded RNA virus. Infected cells produce double-stranded RNA (dsRNA) as an intermediate during viral replication, which can be detected using the J2 antibody against dsRNA. Immunohistochemical staining with the J2 antibody revealed punctate positive staining in discrete perivascular non-endothelial cells in the brains of COVID-19 patients, while no signal was detected in the brains of non-infected patients. This result further confirmed that brain pericytes are particularly susceptible to viral infection and may serve as a "window" for SARS-CoV-2 to enter the CNS.

3.3 SARS-CoV-2 Infection Induces Neuroinflammation

After obtaining initial evidence of SARS-CoV-2 brain infection, the research team hypothesized that this infection is likely to induce neuroinflammation. To verify this, mIHC staining was performed on brain sections from COVID-19 patients and non-infected controls to detect 5 immune cell populations, including helper T cells, cytotoxic T lymphocytes, regulatory T cells, B cells, and macrophages. The results confirmed the hypothesis, showing significant infiltration of these immune cells in the brains of COVID-19 patients, indicating that SARS-CoV-2 infection triggers a robust neuroinflammatory response.

3.4 SARS-CoV-2 Destroys the Blood-Brain Barrier

In late 2020, a U.S. research team found that SARS-CoV-2 can cause "leaks" in the blood-brain barrier, potentially damaging the brain's neural network. The Kristian Pietras team conducted 7-color multiplex fluorescence immunohistochemical analysis to further verify this finding. The results showed leakage of fibrinogen around blood vessels, confirming that SARS-CoV-2 infection of pericytes disrupts the tightly structured blood-brain barrier, which may facilitate the spread of the virus in the CNS and exacerbate neurological damage.

4. Product Empowerment: Absin mIHC Solutions Drive Research Progress

The breakthroughs in this series of SARS-CoV-2 brain invasion mechanism studies are inseparable from the strong support of multiplex fluorescence IHC technology. The Absin product line of ANT BIO PTE. LTD. provides a full range of multiplex fluorescence IHC solutions, including 4-color to 7-color staining kits and personalized technical services, which played a crucial role in the research. Their specific contributions are as follows:

4.1 Core Product Advantages Matching Research Needs

1.       Multi-target simultaneous detection capability: The 4-color to 7-color multiplex fluorescence IHC staining kits can simultaneously detect multiple markers (such as ACE2, CD31, PDGFRβ, dsRNA, fibrinogen, and various immune cell markers) on a single tissue section. This enables researchers to clarify the spatial relationship between virus-infected cells, vascular cells, and immune cells in one experiment, greatly improving research efficiency.

2.       High sensitivity and specificity: The kits adopt Tyramide Signal Amplification (TSA) technology, which significantly enhances the detection signal of low-abundance proteins (such as dsRNA in infected cells). The pre-optimized dyes and secondary antibodies ensure clear and specific staining results, avoiding false positives and false negatives.

3.       Easy operation and complete supporting: The kits are equipped with all necessary components such as dyes and secondary antibodies, and do not require specialized equipment for operation. Researchers with basic IHC experience can complete the experiments, reducing the threshold for technology application.

4.2 Personalized and Standardized Technical Services

In addition to high-quality kits, ANT BIO PTE. LTD. also provides personalized mIHC technical services, including pre-experiment verification, antibody optimization, multi-staining effect evaluation, and formal experiment implementation. The service process strictly follows standardized procedures: from experimental plan confirmation, sample and antibody submission, pre-experiment exploration (including antibody validation and optimal working condition confirmation), to formal staining, scanning imaging, data analysis, and result delivery. This ensures the reliability and reproducibility of experimental results.

For researchers with specific needs, the standardized FLASH Panel detection service is also available. This service offers pre-optimized panels for different species (human and mouse) and research purposes (such as T cell typing, tumor-associated macrophage analysis, and PD-1/PD-L1 feasibility analysis). Researchers only need to provide samples, and the service team will directly deliver experimental results, featuring high cost-effectiveness and time-saving advantages.

5. Research Significance and Prospects

This series of studies has clarified the key mechanism of SARS-CoV-2 brain invasion, revealing that pericytes act as the entry window, and infection induces neuroinflammation and blood-brain barrier damage. These findings provide important theoretical basis for understanding the neurological complications of COVID-19 and developing targeted therapeutic strategies.

Given the rapid mutation rate of SARS-CoV-2, research on its pathogenic mechanism will continue for a long time. Multiplex fluorescence IHC technology, with its ability to provide more abundant information than conventional IHC/immunofluorescence, will remain a powerful tool in pathological research. ANT BIO PTE. LTD. will continue to optimize its mIHC product system and technical services, supporting researchers in in-depth exploration of the pathogenic mechanisms of infectious diseases and promoting the progress of related fields.

6. Brand Mission

ANT BIO PTE. LTD. is dedicated to empowering life science research through the provision of high-quality, reliable reagents and comprehensive solutions. Our specialized sub-brands (Absin, Starter, UA) are strategically positioned to cover a full spectrum of research needs: Absin focuses on general reagents and kits, Starter specializes in antibodies, and UA is dedicated to recombinant proteins. We strive to support researchers in unlocking scientific mysteries, advancing medical progress, and addressing unmet clinical needs through continuous innovation and customer-centric services.

7. Related Product List

8. Disclaimer

This article is AI-compiled and interpreted based on the original work in document 1226.docx (Attention please, COVID-19 Virus is Invading the Brain!) and the referenced literatures (Song E et al., J Exp Med. 2021; Bocci M et al., Int J Mol Sci. 2021). All intellectual property (e.g., images, data) of the original publications shall belong to the corresponding journals and research teams. For any infringement, please contact us promptly and we will take immediate action.

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At ANTBIO, we are committed to advancing life science research through high-quality, reliable reagents and comprehensive solutions. Our specialized sub-brands (Absin, Starter, UA) cover a full spectrum of research needs, from general reagents and kits to antibodies and recombinant proteins. With a focus on innovation, quality, and customer-centricity, we strive to be your trusted partner in unlocking scientific mysteries and driving medical progress. Explore our product portfolio today and elevate your research to new heights.