# Mechanisms of adenovirus neutralization

> **NIH NIH R01** · EMORY UNIVERSITY · 2020 · $718,200

## Abstract

ABSTRACT
Intravascular administration of adenovirus (Ad) vectors holds great promise for improving survival of patients
with disseminated metastatic cancer and ameliorating numerous genetic diseases through permanent correction
of the hematopoietic stem cell compartment. Although potentially advantageous, intravascular delivery makes
therapeutic Ads vulnerable to humoral components of the innate and adaptive arms of the immune system.
Extensive previous analyses by us and others showed that binding of coagulation FX to HAdv-5-based vectors
in the blood facilitates highly efficient hepatocyte transduction, triggering hepatotoxicity. Furthermore, a relatively
high prevalence of HAdv-5-neutralizing antibodies (NAbs) in the human population, prompted active
development of therapeutic vectors based on alternate Ad serotypes that don't interact with FX and exhibit low
NAb prevalence. Our preliminary studies indicate however, that both pre-existing neutralizing and non-
neutralizing humoral immunity can significantly exacerbate the host inflammatory antiviral response. We found
that the majority of human sera that lack HAdv-5-neutralizing activity are still able to trigger complement fixation
on the virus, leading to potentiated inflammatory cytokine production by immune cells. Moreover, we found that
immunization of mice with adenovirus HAdv-11 triggers generation of non-neutralizing antibodies, which are
highly efficient at complement fixation on phylogenetically-distant HAdv-5 virus. Based on these findings, we
propose a novel concept of cryptic opsonizing non-neutralizing antibodies, or CON-Abs, which bind to Ad after
systemic delivery, trigger complement fixation on the virus, and target Ad-immune complexes (Ad-ICs) to
immune phagocytic cells, leading to drastically potentiated systemic inflammation. The molecular mechanisms
mediating the immune-stimulatory properties of pre-existing non-neutralizing immunity and its effect on the safety
of systemic Ad delivery are virtually unknown. Therefore, in Specific Aim 1 of this project we will analyze how
phylogenetically-distant HAdv serotypes trigger generation of CON-Abs to HAdv-5. In Specific Aim 2, we will
determine the structural bases for CON-Ab-mediated complement fixation on the virus and complement-
mediated virus neutralization. In Specific Aim 3 we will determine specific cell types and their receptors that
sequester Ad-ICs in vivo; and in Specific Aim 4 we will determine specific signaling pathways responsible for the
exacerbated inflammatory response to Ad-ICs and develop targeted pharmacological approaches to improve
the safety of systemic Ad delivery in gene transfer and cancer therapy models. The proposed studies will provide
new mechanistic insights into fundamental functions of innate and adaptive immunity and host anti-viral defense,
as well as allow for the development of novel patient stratification tools and pharmacological approaches to
improve the safety of clinical interventions t...

## Key facts

- **NIH application ID:** 10120985
- **Project number:** 2R01AI107960-06
- **Recipient organization:** EMORY UNIVERSITY
- **Principal Investigator:** PHOEBE L STEWART
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $718,200
- **Award type:** 2
- **Project period:** 2014-06-01 → 2025-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10120985

## Citation

> US National Institutes of Health, RePORTER application 10120985, Mechanisms of adenovirus neutralization (2R01AI107960-06). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10120985. Licensed CC0.

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