# Mechanisms of DDO Adjuvancy

> **NIH NIH R01** · WASHINGTON UNIVERSITY · 2021 · $483,905

## Abstract

SUMMARY
 Adjuvants able to induce long lasting type-1 cellular immunity, including both Th1 CD4+ T cells and
cytotoxic CD8+ T cells, are highly sought out for the development of vaccines against intracellular pathogens
that evade antibodies. We have identified a powerful new class of adjuvant that elicits protective type-1 biased
responses. These adjuvants are synthetic RNA oligonucleotides derived from defective viral genomes (DDOs)
and trigger strong immune responses by engaging cellular RIG-I-like receptors (RLRs). DDOs contain a unique
immunostimulatory motif that we identified as essential for their ability to trigger RLR signaling. In mice, DDOs
induce localized expression of type I IFNs and other cytokines and promote accumulation of DCs in the
draining lymph node. In addition, DDOs promote a type I IFN-dependent IgG2b/c-biased antibody response
able to protect mice from lethal virus challenge and induce IFNγ-producing antigen-specific CD4+ and CD8+ T
cells. Moreover, DDOs synergize with the squalene-based adjuvant AddaVax, providing strong type-1
immunity bias to vaccines adjuvanted with AddaVax+DDOs. These data support our central hypothesis that
DDOs represent a new class of adjuvants that stimulate the RLR/type I IFN signaling axis to drive
optimal long-lived type-1 humoral and cellular immunity.
 Experiments in this proposal use the combined expertise and unique set of tools of the Lopez and
Scott laboratories to assess the quality, longevity, and protective capacity of DDO-induced T cell responses
during vaccination, and to characterize specific molecular and cellular mechanisms responsible for directing
the type-1 immune response after DDO administration. Specifically, in Aim 1 we will use our ability to track
DDOs in vivo, together with a series of reporter and transgenic mice, to identify the early interactions of DDOs
with cells of the immune system, in particular DCs, and to identify potential key targets for the development of
type -1 biased responses. In Aim 2, we will assess the development and quality of T helper 1 cells, cytotoxic T
cells, T follicular helper cells, and tissue resident T cells in response to a vaccine adjuvanted with DDOs alone
or in combination with AddaVax, and assess the role of type I IFNs in establishing these responses. In Aim 3,
we will test the ability of DDOs to induce CD4+-mediated protection against the intracellular protozoan parasite
Leishmania, since protection against this parasite is dependent upon CD4+ Th1 cells and is independent of
antibodies, and we will directly assess the ability of DDOs to induce protective T cell responses using a model
influenza vaccine in ferrets.

## Key facts

- **NIH application ID:** 10242966
- **Project number:** 5R01AI134862-04
- **Recipient organization:** WASHINGTON UNIVERSITY
- **Principal Investigator:** Carolina B. Lopez
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $483,905
- **Award type:** 5
- **Project period:** 2018-08-15 → 2023-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10242966

## Citation

> US National Institutes of Health, RePORTER application 10242966, Mechanisms of DDO Adjuvancy (5R01AI134862-04). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10242966. Licensed CC0.

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