# TARGETING COMPLEMENT TO GRAM-NEGATIVE BACTERIA WITH ANTIBODY: PROPERDIN CONJUGATES

> **NIH NIH R21** · WASHINGTON UNIVERSITY · 2020 · $196,614

## Abstract

Project Summary
There is an urgent need for the development of innovative strategies to counter the growing threat of multi-drug
resistance. Complement (C) presents the first line of defense against microbial intruders. Complement directs
the removal of invasive bacteria through two major mechanisms: 1) the clearance of opsonized bacteria by the
mononuclear phagocytic system; and 2) the disruption of bacterial cell integrity by the membrane attack complex
(MAC), leading to lysis. Many Gram-negative bacteria resist C attack by expressing outer membrane
components that recruit fluid phase complement regulators that serve to protect host tissues. Our long-term goal
is to develop novel C-based antibiotics that can be effective against pathogenic Gram-negative bacteria.
Properdin, a component of the complement alternative activation pathway (AP), is the sole positive regulator of
complement. It plays an essential role in combatting pyogenic infection, serving to stabilize the labile AP
convertase, a key player in the cascade. In certain circumstances properdin can also initiate C activity by binding
directly to a target, forming a platform for convertase assembly. High MW properdin, manufactured in the
laboratory, binds readily to Streptococcus pneumonia and N. meningitides, initiating C-dependent bactericidal
activity in vitro, and conferring protection against infection in animal models. High MW properdin, however, binds
a variety of biological surfaces and would potentially cause dangerous second site C activity. We posit that
properdin antimicrobial activity would be more specific and safe if targeted via an antibody drug conjugate. We
have previously engineered scFv-properdin bifunctional constructs and demonstrated their capacity to direct C
activity to a red blood cell in vitro. Importantly, properdin-initiated complement activation occurs in the presence
of endogenous fluid phase and surface bound complement inhibitors, including the host C regulators that protect
many Gram-negative bacteria. We propose to engineer single chain antibody/properdin conjugates that bind to
the Gram-negative outer wall and mediate bacterial lysis and clearance. To that end we propose the following
specific aims:
1. Produce scFV-properdin bifunctional proteins that can recognize the major Gram-negative cell wall
components (lipopolysaccharide, LPS).
2. Use in vitro and in vivo assays to characterize the capacity of scFv-properdin bifunctional proteins
prepared in SA#1 to mobilize a complement response against Gram-negative bacteria.

## Key facts

- **NIH application ID:** 9854886
- **Project number:** 5R21AI137223-02
- **Recipient organization:** WASHINGTON UNIVERSITY
- **Principal Investigator:** DENNIS EMIL HOURCADE
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $196,614
- **Award type:** 5
- **Project period:** 2019-01-25 → 2021-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9854886

## Citation

> US National Institutes of Health, RePORTER application 9854886, TARGETING COMPLEMENT TO GRAM-NEGATIVE BACTERIA WITH ANTIBODY: PROPERDIN CONJUGATES (5R21AI137223-02). Retrieved via AI Analytics 2026-06-11 from https://api.ai-analytics.org/grant/nih/9854886. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*