C-Reactive Protein (CRP) Is Essential for Efficient Systemic Transduction of Recombinant Adeno-Associated Virus Vector 1 (rAAV-1) and rAAV-6 in Mice

Abstract

eThe clinical relevance of gene therapy using the recombinant adeno-associated virus (rAAV) vectors often requires widespread distribution of the vector, and in this case, systemic delivery is the optimal route of administration. Humoral blood factors, such as antibodies or complement, are the first barriers met by the vectors administered systemically. We have found that other blood proteins, galectin 3 binding protein (G3BP) and C-reactive protein (CRP), can interact with different AAV serotypes in a speciesspecific manner. While interactions of rAAV vectors with G3BP, antibodies, or complement lead to a decrease in vector efficacy, systemic transduction of the CRP-deficient mouse and its respective control clearly established that binding to mouse CRP (mCRP) boosts rAAV vector 1 (rAAV-1) and rAAV-6 transduction efficiency in skeletal muscles over 10 times. Notably, the high efficacy of rAAV-6 in CRP-deficient mice can be restored by reconstitution of the CRP-deficient mouse with mCRP. Human CRP (hCRP) does not interact with either rAAV-1 or rAAV-6, and, consequently, the high efficiency of mCRP-mediated muscle transduction by these serotypes in mice cannot be translated to humans. No interaction of mCRP or hCRP was observed with rAAV-8 and rAAV-9. We show, for the first time, that serum components can significantly enhance rAAV-mediated tissue transduction in a serotype-and species-specific manner. Bioprocessing in body fluids should be considered when transfer of a preclinical proof of concept for AAV-based gene therapy to humans is planned.A deno-associated virus (AAV) vectors attract great attention as a promising tool for a wide range of applications in gene therapy. The process of cell transduction by recombinant AAVs (rAAVs) has been studied in detail, and cellular receptors responsible for the virus entry have been identified. Most of these studies were accomplished in cell culture (1-3) without taking into account the exposure of rAAVs to components of body fluids in the in vivo situation. Interestingly, in many cases, protein classes having specific posttranslational modifications, such as ␣-2,3 and ␣-2,6 sialic acids, N-linked glycoproteins, or heparan sulfate proteoglycan, were identified as primary cell receptors for efficient rAAV transduction (4-6). These posttranslational modifications are common between mammalian species, giving hope to the possibility that rAAV efficiency could be similar across species and that animal data are predictive of the human situation.Nevertheless, some recent data indicate that interactions of cellular receptors or blood proteins with rAAVs can be species specific. Thus, adeno-associated virus vector 3 (rAAV-3), which efficiently transduces human hepatocytes through the hepatocyte growth factor receptor (HGFR), failed to transduce murine hepatocytes, suggesting that AAV-3 specifically uses human HGFR, but not murine HGFR, as a cellular coreceptor for transduction (7-9). In human and dog blood, but neither mouse nor monkey blood, galectin 3 binding protein (G3BP) in...

Human Immune Responses to Adeno-Associated Virus (AAV) Vectors

“…While even low-titer NAbs are associated with efficient vector neutralization in vivo (44)(45)(46), the presence of binding non-NAbs appear to enhance rAAV transduction efficacy, at least in some tissues (43). Pre-existing anti-AAV antibodies in individuals receiving rAAV vectors are being investigated as a potential source of toxicity related to complement activation (47) although a direct interaction of rAAV vectors with complement proteins was also reported (48,49).…”

Systemic delivery of adeno-associated viral vectors

“…Inactivation by pre-existing neutralizing antibodies has been well documented. Recently, Denard et al found that some blood proteins bind to certain AAV serotypes in a species-specific manner [92,93]. In particular, AAV-6 interacts with the galectin 3 binding protein in human and dog sera but not macaque and mouse sera.…”

“…On the other side, AAV-6 interacts with the C-reactive protein in mouse but not human sera. Instead of inhibition, this interaction boosts systemic delivery [93]. …”

An Emerging Adeno-Associated Viral Vector Pipeline for Cardiac Gene Therapy

“…Interestingly, both AAV1 and AAV6 do not interact with murine or macaque G3BP. Further, both AAV strains have been shown to bind murine C-reactive protein, but not the human counterpart (Denard et al, 2013). These findings highlight the potential for variability in species-specific interactions between AAV capsids and host proteins in general.…”