Angiotensin Peptides as Modulators of SARS-CoV-2 Spike–AXL Interaction: Implications for Cardiovascular and Viral Pathogenesis

Study Background and Research Question

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the causative agent of COVID-19, initiates infection by binding its spike glycoprotein to host cell receptors. While angiotensin-converting enzyme 2 (ACE2) has been widely recognized as a primary receptor, recent research has identified additional host factors such as neuropilin-1 (NRP1) and AXL that facilitate viral entry, especially in tissues with low ACE2 expression. Concurrently, angiotensin peptides—core effectors of the renin-angiotensin system (RAS)—are central to cardiovascular regulation and are biochemically interlinked with SARS-CoV-2 pathogenesis. The reference study by Oliveira et al. (2025) investigates whether naturally occurring angiotensin fragments, including truncated forms such as Angiotensin 1/2 (5-7), modulate the interaction between the SARS-CoV-2 spike protein and its receptors, focusing on AXL as a novel entry pathway.

Key Innovation from the Reference Study

This work represents the first systematic delineation of how specific angiotensin peptides, generated through physiological RAS processing, directly influence the binding affinity between the SARS-CoV-2 spike protein and AXL. The study moves beyond conventional ACE2-centric models by highlighting AXL-mediated infection routes and demonstrates that shorter, naturally occurring angiotensin peptides—including the H2N-Ile-His-Pro-OH tripeptide (Angiotensin 1/2 (5-7))—potently enhance spike–AXL binding. This positions angiotensin fragments not only as regulators of blood pressure but also as functional modulators of viral entry, bridging cardiovascular and infectious disease biology.

Methods and Experimental Design Insights

Oliveira et al. employed antibody-based binding assays to quantify interactions between recombinant SARS-CoV-2 spike protein and host cell receptors (ACE2, NRP1, AXL) in the presence of various angiotensin peptides. The experimental design included both full-length and truncated angiotensin peptides, encompassing classical forms (angiotensin I (1–10), angiotensin II (1–8)) and shorter derivatives generated by stepwise C- and N-terminal deletions (e.g., angiotensin (1–7), angiotensin (5–7)). Peptide modifications—such as substitution or phosphorylation at residue 4—were also tested to probe structure-activity relationships. The magnitude of spike–receptor binding was assessed quantitatively, enabling direct comparison of each peptide's modulatory effect.

Core Findings and Why They Matter

The study revealed that:

• Angiotensin II (1–8) causes a two-fold increase in spike–AXL binding, while the longer angiotensin I (1–10) has no significant effect (Oliveira et al., 2025).
• Shorter peptides derived by C-terminal truncation (e.g., angiotensin (1–7), angiotensin (1–6)) retain or enhance this activity.
• N-terminally truncated fragments—including angiotensin (5–7) (the H2N-Ile-His-Pro-OH peptide)—exhibit even greater potentiation of spike–AXL binding, with certain forms (like angiotensin IV) driving up to a 2.7-fold increase.
• Substitution of tyrosine at position 4, or its phosphorylation, further augments spike–AXL interaction, indicating a critical structural motif for this effect.
• Some peptides (notably angiotensin IV) also enhance spike binding to ACE2 and NRP1, but the most pronounced and selective effects are observed with AXL.

These findings underscore a direct mechanistic link between RAS peptides and viral entry mechanisms, suggesting that RAS dysregulation—common in hypertension and cardiovascular disease—may potentiate SARS-CoV-2 infectivity via non-ACE2 pathways. This insight not only deepens our understanding of COVID-19 pathogenesis but also highlights the need for integrated approaches in hypertension and viral research.

Why this cross-domain matters, maturity, and limitations

The cross-domain relevance of these results is significant: angiotensin peptides are established vasoconstrictors and central to blood pressure control, yet this study reveals their additional capacity to modulate viral spike–host receptor interactions. The maturity of this evidence is supported by direct binding assays and structure–activity analysis, but further in vivo validation and clinical correlation are necessary. The precise physiological concentrations at which such modulatory effects occur in human tissues remain to be elucidated, and extrapolation to patient outcomes should be done cautiously until corroborated by translational studies.

Comparison with Existing Internal Articles

Several internal resources discuss the technical and translational applications of Angiotensin 1/2 (5-7), particularly in the context of RAS-driven assays and hypertension research:

• The article "Angiotensin 1/2 (5-7): Unlocking Translational Opportunities" provides mechanistic insights into how the H2N-Ile-His-Pro-OH peptide bridges cardiovascular signaling and viral pathogenesis, closely paralleling the reference study's cross-domain focus.
• "Angiotensin 1/2 (5-7): Practical Solutions for Reliable Cell-Based Assays" details how this peptide supports reproducible workflows in cell signaling and cytotoxicity assays, offering practical protocols that align with the binding assays described by Oliveira et al.
• Other resources, such as "Precision Tool for RAS-Driven Assays", highlight technical nuances relevant for researchers adapting these findings to experimental systems.

What distinguishes the reference study is its demonstration of angiotensin peptide involvement in viral receptor modulation, a novel biological dimension that complements the assay-focused guidance of internal articles. Integrating both knowledge streams may support more holistic experimental designs in RAS and COVID-19 research.

Limitations and Transferability

While the reference paper provides robust in vitro evidence for angiotensin peptide–spike–receptor interactions, several limitations must be noted:

• The binding assays are conducted under controlled laboratory conditions, which may not capture the complexity of in vivo peptide dynamics or the influence of tissue-specific factors.
• Peptide concentrations used in vitro may not reflect physiological or pathophysiological states in patients, particularly those with hypertension or cardiovascular comorbidities.
• Although the study implicates several angiotensin fragments—including Angiotensin 1/2 (5-7)—in enhancing spike–AXL binding, the downstream effects on viral infectivity and clinical outcomes require further investigation.

As such, while the findings offer compelling mechanistic hypotheses, translation to therapeutic targeting or clinical risk stratification should await additional in vivo validation.

Protocol Parameters

• Peptide selection: For spike–AXL binding assays, short angiotensin fragments such as H2N-Ile-His-Pro-OH (Angiotensin 1/2 (5-7)) can be employed to probe structure–activity relationships as demonstrated by Oliveira et al.
• Concentration range: Literature protocols typically test peptides at micromolar concentrations (e.g., 1–10 μM), but optimization may be required depending on assay conditions.
• Buffer compatibility: The H2N-Ile-His-Pro-OH peptide is highly soluble in water, DMSO, and ethanol at ≥36.5–50 mg/mL, facilitating its use in various biochemical and receptor-binding assays, as supported by the product information.
• Storage: Peptide stock solutions should be freshly prepared or stored at -20°C as solids for optimal stability; short-term use of solutions is recommended.
• Controls: Include negative (no peptide) and positive (full-length angiotensin II) controls to contextualize binding enhancement effects.

Research Support Resources

Researchers interested in further delineating the role of angiotensin peptides in renin-angiotensin system research, blood pressure regulation, or SARS-CoV-2 spike protein binding can utilize high-purity H2N-Ile-His-Pro-OH peptides. Angiotensin 1/2 (5-7) (SKU A1049) from APExBIO is validated for solubility and biochemical compatibility, supporting reliable cell-based and biochemical workflows as outlined in the reference study. This reagent facilitates reproducibility and mechanistic exploration across hypertension and COVID-19 research domains.