AAV1-CMV-mCherry

Viral vectors are an active area of research and development for the treatment of central nervous system (CNS) diseases. However, systemic delivery of large molecular weight biologics is complicated by limited crossing of the blood-brain barrier, immune clearance in the circulation, off-target effects, and systemic or organ toxicity. In the field of drug delivery, quantitative, high-resolution spatial analysis of drug distribution in the brain and other organs is a challenge. To address this issue, researchers introduced a computational pipeline to reconstruct and quantify the three-dimensional distribution of locally delivered viral vectors from two-dimensional microscopy images of subsampled brain sections. The pipeline combines existing and newly developed machine learning and other computational tools to effectively eliminate a large number of false positive artifacts in large-scale images of uncleared tissue sections, and subsampling adequately predict the dispersion of model viral vectors from the perspective of local drug delivery. In addition, the pipeline successfully captures differences in the distribution of adenoviral (AdV) and adeno-associated viral (AAV) vectors, which exhibit different size and transport properties.

Here, researchers tested whether a quantitative 3D reconstruction pipeline could capture differences in the distribution of two different viral vectors, AAV and adenovirus (AdV) (Figure 1). AAV1-CMV-mCherry and AdV-CMV-eGFP vectors were co-administered via needle injection or capsule implantation. Consistent with the hypothesis, visual inspection of 3D renderings of viral vector distribution indicated that the smaller AAV1 vector was dispersed farther than the larger AdV vector in the rat brain (Figure 1a). Quantification of various parameters of viral vector distribution further supported this hypothesis (Figures 1b and c). The smaller AAV1 vector transduced approximately 10,000 cells in a brain tissue volume of approximately 100 mm3, either via needle injection or capsule implantation (Figure 1b). In contrast, the larger AdV virus did not disperse as well, transducing 30-40 times fewer cells than AAV1. AdV was also distributed in a significantly smaller volume of brain tissue compared to AAV1 (Figure 1b). In the needle case, AdV was confined to the needle tract (Figure 1a), and it affected a brain tissue volume that was more than 100-fold smaller than that of AAV1 (Figure 1b). Quantification of the distance between virus+cells and the drug delivery boundary further supported the superior dispersion of AAV1 (Figures 1b and c). Thus, overall, the quantitative 3D reconstruction pipeline successfully captured the broader dispersion of the smaller viral vector.

Figure 1. Comparison of AAV1 and AdV distribution using the quantitative 3D reconstruction pipeline. (Poceviciute R, et al., 2024)