# Analyzing the expression and activation of Perforin-2 -a bactericidal pore-forming protein- with single domain antibodies

> **NIH NIH R21** · UNIVERSITY OF MIAMI SCHOOL OF MEDICINE · 2022 · $191,875

## Abstract

The phagocytosis and destruction of microorganisms is an essential immunological function of
macrophages and other phagocytes that protects us from invading pathogens. However current
understanding of this process is incomplete because we have shown that bacteria are able to
replicate and survive within macrophages that lack Perforin-2 (PRF2); until recently a largely
uncharacterized protein. As expected from cell based studies, when challenged with pathogens PRF2
knockout mice succumb to infectious doses that the majority of their wild-type littermates survive. This
is accompanied by replication and dissemination of bacteria to deeper tissues. Further underscoring
the importance of PRF2 in host defense is the fact that some pathogens deploy effectors to block the
delivery of PRF2 to phagosomes. Recent high resolution structures of PRF2 have shown that it is a
pore-forming protein and that the transition from pre-pore-to-pore is driven by low pH; consistent with
its role within acidifying phagosomes. This is accompanied by substantial intra- and inter-domain
conformational changes. Although the data is not yet extensive, a clinical picture is beginning to
emerge that certain mutations within PRF2 correlate with chronic bacterial infections. Further
research in this area may well reveal that PRF2 haploinsufficiency is the underlying cause of
recurring or persistent infections. These and others studies have established that PRF2 underpins
one of the most basic functions of macrophages and other phagocytes.
 Although considerable advances have been made within this new area of research, progress is
hindered by a critical lack of antibodies that are the mainstay of immunological investigations. Thus,
the objective of this proposal is to isolate and evaluate heavy chain antibodies (VHHs) against PRF2.
We further propose to develop conformation specific VHHs that are able to discriminate between the
monomeric and, oligomeric pre-pore and pore conformations. In Aim1 we will capitalize on the recent
discovery that pH controls PRF2 conformations to isolate VHHs to both mouse and human pre-pore
and pore complexes from a synthetic VHH library. In Aim2 we will produce, rank, and evaluate VHHs
in a variety of immunological assays. As an indicator of initial momentum we already have 18 unique
clones from a screen against the P2 domain of PRF2; some of which are expected to be specific for
PRF2 monomers. We anticipate that anti-PRF2 VHHs will remove current roadblocks that hinder
progress to further elucidate the central role of PRF2 in innate immune defense. PRF2 research is
highly significant to human health because our preliminary data, recent publications, and
characterization of haploinsufficient individuals demonstrate that it underpins an essential function of
phagocytes.

## Key facts

- **NIH application ID:** 10320041
- **Project number:** 5R21AI156567-02
- **Recipient organization:** UNIVERSITY OF MIAMI SCHOOL OF MEDICINE
- **Principal Investigator:** GEORGE Patrick MUNSON
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $191,875
- **Award type:** 5
- **Project period:** 2020-12-17 → 2023-11-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10320041

## Citation

> US National Institutes of Health, RePORTER application 10320041, Analyzing the expression and activation of Perforin-2 -a bactericidal pore-forming protein- with single domain antibodies (5R21AI156567-02). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10320041. Licensed CC0.

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