Kidney Week

Abstract: SA-PO0118

Comparative Analysis of Kidney-Tropic Adeno-Associated Virus (AAV) Vectors: Distinguishing True Transduction from Protein Reabsorption

Session Information

• ADPKD and Cystic Kidney Disease - 3
  October 24, 2026 | Location: Exhibit Hall A, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Genetic Diseases of the Kidneys

• 1201 Genetic Diseases of the Kidneys: Cystic (Monogenic)

Authors

• Milagros, Sergio, Fundacion para la Investigacion Medica Aplicada, Pamplona, Navarre, Spain

Sergio Milagros

• Santana, Nerea, Fundacion para la Investigacion Medica Aplicada, Pamplona, Navarre, Spain

Nerea Santana

• Neri, Leire, Fundacion para la Investigacion Medica Aplicada, Pamplona, Navarre, Spain

Leire Neri

• Carte, Beatriz, Fundacion para la Investigacion Medica Aplicada, Pamplona, Navarre, Spain

Beatriz Carte

• Zabaleta, Nerea, Fundacion para la Investigacion Medica Aplicada, Pamplona, Navarre, Spain

Nerea Zabaleta

• Gonzalez-Aseguinolaza, Gloria, Fundacion para la Investigacion Medica Aplicada, Pamplona, Navarre, Spain

Gloria Gonzalez-Aseguinolaza

• Aldabe, Rafael, Fundacion para la Investigacion Medica Aplicada, Pamplona, Navarre, Spain

Rafael Aldabe, PhD

Group or Team Name

• Gene Therapy for Genetic Diseases

Background

Inherited renal diseases affect ~0.2% of the population, yet efficient gene therapy delivery to kidney cells remains elusive. The kidney's filtration barrier restricts vector access to the renal epithelium based on size and charge. To overcome these barriers, we evaluated the transduction efficiency and tropism of specialized renal AAV variants compared to systemic standards.

Methods

We compared the renal tropism of AAV-KP1, AAV-KP2, and AAV-KP3 against AAV9. To bypass the glomerular filtration barrier, vectors were administered locally via retroureteral injection into the left renal pelvis, or systemically via intravenous administration. Two weeks post-injection, transduction efficiency was assessed by quantifying vector genome copies and transgene mRNA by qPCR and FISH, and protein expression (GFP/mCherry) by immunohistochemistry throughout the renal parenchyma.

Results

Retroureteral administration of AAV-KP1, AAV-KP2, and AAV-KP3 in the left kidney resulted in robust and widespread transduction across the renal epithelium, from the proximal tubule to the collecting duct. In contrast, AAV9 showed minimal renal tropism even with local delivery. Notably, retroureteral administration did not prevent vector entry into the systemic circulation, as evidenced by a high hepatic transduction. Contralateral (right) kidney transduction was restricted to the glomerulus, yet in a subset of animals, GFP protein accumulation was detected in proximal tubular cells of the uninjected kidney despite negligible transgene mRNA levels. Consistent with this observation, systemic administration of either AAV-KP1 or AAV9 also led to accumulation of the transgene-encoded proteins mCherry and GFP in proximal tubular cells despite nearly undetectable transgene mRNA. This suggests that the observed GFP/mCherry was largely due to the reabsorption of filtered proteins rather than successful viral transduction.

Conclusion

Retroureteral delivery of AAV-KP1, AAV-KP2, and AAV-KP3 constitutes an efficient strategy for transducing renal epithelial cells. However, given the intrinsic protein reabsorption capacity of the proximal tubule, protein detection alone is insufficient to confirm productive vector transduction. Transgene mRNA analysis is therefore essential to distinguish genuine gene expression from filtered protein uptake in renal epithelial cells.