Interactions Between Human Plasma Components and A Xenogenic Adenovirus Vector: Reduced Immunogenicity During Gene Transfer

Abstract

By the time we are adolescents most of us have been in contact with several of the >50 human adenovirus (HAd) serotypes. These common subclinical infections lead to an efficient anti-adenovirus cross-reacting adaptive immunity. During gene therapy, the ubiquitous anti-adenovirus humoral response and complement activation will modify and dictate vector biodistribution, as well as the response to the virion and transgene(s). In this study, we assayed the interactions of a xenogenic adenovirus derived from canine serotype 2 (CAV-2) with naturally occurring human antibodies (Abs) and the complement system. In our cohort, we found class G immunoglobulins (Igs) that recognized the intact CAV-2 virion and the external virion proteins. However, the majority of donors had low or no neutralizing Abs, class A, or class M Igs. Purified anti-HAd serotype 5 Abs also recognized CAV-2 virion proteins. In addition, in spite of the presence of anti-CAV-2 IgGs, CAV-2 poorly activated the classical and alternative complement cascades. This atypical response was due to a block upstream of the component 3 (C3) convertase and interplay between the component 1 (C1) inhibitor, the C1q-C1r2-C1s2 complex and CAV-2. Our data demonstrate that some xenogenic adenovirus vectors, like CAV-2, could lead to notably different outcomes following systemic delivery.

Clearance of Adenovirus by Kupffer Cells Is Mediated by Scavenger Receptors, Natural Antibodies, and Complement

“…These technical factors may help to explain why there is considerable disagreement among previous studies on the mechanisms by which Ad5 activates human complement. Although all studies agree that the lectin pathway plays no role, some studies found that only the classical pathway is involved (9,66), other studies found that the alternative but not the classical pathway is involved (4,23), and an additional study found that both the classical and alternative pathways are involved depending on the concentration of Ad (41).…”

“…Several previous in vitro studies with human plasma or serum have shown that Ad5 can bind to and activate complement (4,9,23,41). One issue with using human material is that individual humans have variable levels of specific anti-Ad antibodies that activate complement via the classical pathway (9).…”

Human Coagulation Factor X-Adenovirus Type 5 Complexes Poorly Stimulate an Innate Immune Response in Human Mononuclear Phagocytes

“…We did not include other host blood factors in this study. Among these, there are lactoferrin, ␣-defensin, complement factor C1 and C3, coagulation FVII, and protein C (61,62). Combining these factors in an exclusively human assay will contribute to a better understanding of the host-pathogen interaction with HAds.…”

DNA/NYVAC Vaccine Regimen Induces HIV-Specific CD4 and CD8 T-Cell Responses in Intestinal Mucosa

“…The neutralizing activity of the plasma of each volunteer enrolled was determined by transduction inhibition assays using the 911 cell line (28).…”

“…It was then relevant to determine whether Ad5-NAb titers correlated with the presence and/or the proliferative capacity of Ad-specific CD4 T cells isolated from gut mucosal tissues in naturally adenovirus-infected volunteers. To address this issue, Ad5-NAb titers were determined for each volunteer as previously described (28). The volunteers were stratified into two groups based on their Ad5 serostatus: (i) Ad5 NAb low (titer, Ͻ18) and (ii) Ad5 NAb high (Ͼ18) (6,20).…”