AAV-Delivered hACE2 Animal Models: A Flexible Platform for Studying Viral Entry, Disease Mechanisms, and Therapeutic Strategies

Introduction

Recombinant adeno-associated virus, or rAAV, has become a powerful tool in gene delivery, disease modeling, and preclinical research. In the context of coronavirus research, one important application is the use of rAAV vectors to deliver human angiotensin-converting enzyme 2, or hACE2, into animal models. Because ACE2 is a key cellular receptor used by SARS-CoV and SARS-CoV-2 for host-cell entry, hACE2 expression can help generate animal models that more closely reproduce key aspects of human viral susceptibility.

rAAV-hACE2 models provide researchers with a flexible alternative to traditional transgenic animal models. Instead of requiring the generation and breeding of germline-modified animals, rAAV-mediated hACE2 expression allows investigators to introduce hACE2 into selected tissues of existing animal strains. This approach can accelerate model development, broaden the choice of genetic backgrounds, and support studies of viral entry, host immune responses, disease mechanisms, vaccine evaluation, and antiviral drug development.

Why hACE2 Animal Models Are Important

Many viruses show species-specific differences in receptor usage and host susceptibility. For SARS-CoV-2 research, conventional laboratory mice are less naturally susceptible to infection because mouse ACE2 does not fully recapitulate the interaction between human ACE2 and the viral spike protein. hACE2 animal models address this limitation by expressing the human receptor in relevant tissues, allowing researchers to study viral entry, tissue tropism, inflammation, immune response, and disease progression in vivo.

Traditional hACE2 transgenic mice have been widely used, but they may be limited by availability, genetic background, expression pattern, and disease phenotype. rAAV-mediated hACE2 delivery offers a complementary strategy. By selecting an appropriate AAV serotype, promoter, and route of administration, researchers can achieve tissue-directed hACE2 expression and generate models suitable for specific research questions.

Why rAAV Is Useful for hACE2 Model Development

rAAV vectors are well suited for in vivo gene delivery because they can transduce a variety of tissues, support relatively long-term transgene expression, and generally remain episomal in host cells. These properties make rAAV useful for establishing temporary or semi-stable expression of hACE2 in animal tissues without creating a permanent transgenic line.

For hACE2 model development, rAAV offers several advantages:

• Flexible model generation using existing mouse strains or other animal backgrounds.
• Tissue-directed hACE2 expression depending on vector design and delivery strategy.
• Faster model establishment compared with traditional transgenic breeding.
• Compatibility with studies of viral pathogenesis, immune response, vaccine protection, and antiviral efficacy.
• Ability to study disease mechanisms in specific genetic or immunological backgrounds.

This flexibility is especially valuable when researchers need to evaluate host factors, immune pathways, age-related susceptibility, comorbidities, or therapeutic interventions in different animal models.

Applications of rAAV-hACE2 Animal Models

rAAV-hACE2 models have been used primarily as research tools for studying coronavirus biology and related disease mechanisms. By enabling hACE2 expression in vivo, these models can support investigation of how viruses enter host tissues, how local and systemic immune responses develop, and how inflammatory injury contributes to disease outcomes.

Major research applications include:

• Viral entry and tissue tropism: rAAV-hACE2 models help researchers study how receptor expression influences viral susceptibility in specific tissues.
• Disease pathogenesis: These models can be used to evaluate inflammatory responses, tissue injury, and host-pathogen interactions after viral challenge under appropriate biosafety conditions.
• Vaccine evaluation: rAAV-hACE2 models can support preclinical assessment of whether vaccine candidates reduce viral replication, disease severity, or inflammatory pathology.
• Antiviral drug testing: These models provide a platform for evaluating antiviral agents, neutralizing antibodies, or host-directed therapies in vivo.
• Host factor studies: Because rAAV-hACE2 can be applied to different genetic backgrounds, it can help researchers investigate how specific immune or disease-related pathways affect infection outcomes.

Scientific and Technical Considerations

Although rAAV-hACE2 models are valuable, they must be interpreted carefully. hACE2 expression driven by an AAV vector may not fully match the natural distribution, regulation, or expression level of ACE2 in humans. Vector dose, promoter choice, tissue tropism, timing of expression, and host immune responses can all influence model behavior.

There are also important biological considerations. ACE2 is not only a viral entry receptor; it is also an enzyme involved in the renin-angiotensin system, where it helps regulate angiotensin II and angiotensin-(1–7) signaling. Therefore, artificial overexpression of hACE2 may influence local physiology, inflammation, vascular tone, or tissue repair pathways. These effects should be considered when interpreting disease phenotypes.

Key limitations include:

• AAV-driven hACE2 expression may differ from endogenous human ACE2 expression.
• Tissue distribution depends strongly on AAV serotype, promoter, and administration route.
• Immune responses to AAV or hACE2 may affect model performance.
• hACE2 expression level may influence disease severity and experimental reproducibility.
• Findings from rAAV-hACE2 models should be validated using complementary systems when possible.

rAAV-hACE2 animal models will likely continue to support infectious disease research, especially when rapid and flexible model generation is needed. Future improvements may include more tissue-specific promoters, regulatable expression systems, improved AAV capsids, and more refined control of hACE2 expression levels. These advances could make rAAV-hACE2 models more physiologically relevant and better suited for studying specific disease mechanisms.

Beyond coronavirus research, the broader concept of rAAV-mediated receptor expression may be useful for modeling other infectious diseases or receptor-dependent biological processes. By enabling controlled expression of human entry factors or disease-related genes in animal tissues, rAAV vectors can help bridge the gap between cell-based assays and complex in vivo models.

Conclusion

rAAV-mediated hACE2 expression has become a valuable tool for developing flexible animal models of viral entry and disease pathogenesis. By delivering human ACE2 into selected tissues, rAAV vectors allow researchers to study infection mechanisms, immune responses, vaccine protection, and antiviral strategies in vivo.

While these models are powerful, they are not perfect replicas of human disease. Careful attention to vector design, tissue specificity, expression level, immune response, and biosafety is essential. When used appropriately and interpreted alongside complementary models, rAAV-hACE2 animal systems can provide important insights into infectious disease biology and therapeutic development.