# Single-chain antibodies to block HIV transcription and prevent reactivation from latently infected resting CD4+ T cells

> **NIH NIH R21** · UNIVERSITY OF CALIFORNIA, SAN FRANCISCO · 2022 · $201,875

## Abstract

PROJECT SUMMARY
Despite decades of successful antiretroviral therapy (ART), persistent HIV-infected resting CD4+ T cells can
remain undetected in tissue reservoirs. HIV replication is cytopathic in activated CD4+ T cells; however, a fraction
of HIV-infected activated CD4+ T cells revert to the resting G0 phenotype in tissue reservoirs. These persistent
HIV-infected resting CD4+ T cells undergo intermittent activation and produce fully infectious virus. HIV is
invariably detected in the plasma when patients discontinue ART because plasma viremia is reseeded by
intermittent activation of persistent HIV-infected resting CD4+ T cells in the tissue reservoirs.
In response to RFA-AI-19-072: Novel Therapeutics Directed to Intracellular HIV Targets, we propose an
innovative analytic bioassay to identify next-generation single-chain antibodies that sustain HIV remission. Our
research is focused on the essential role of heat shock protein 90 (Hsp90) in HIV replication, and we have shown
that mild heat shock (39.5°C) accelerates HIV transcription. Increased Hsp90 activity at 39.5°C was critical for
full-length HIV RNA synthesis by host transcription factors, and we have shown that 39.5°C reactivates latent
HIV replication in ART-suppressed aviremic HIV-infected patient samples, in human resting CD4+ T cells isolated
from fully suppressed humanized mice, and in three distinct in vitro models of HIV latency.
Reactivation of latent HIV depends on multiple host proteins interacting with their HIV counterpart, and the
recently developed QUECEL (quiescent effector cell latency) model of HIV latency is an ideal in vitro system to
identify single-chain antibodies that disrupt HIV-host protein interactions. The QUECEL carries a modified HIV
provirus that depends on all the HIV-host protein interactions to reactivate latent HIV RNA synthesis. The latent
QUECEL depends on host protein interaction for both the HIV Tat-mediated transcription and HIV Rev-mediated
export of the full-length viral genome, and we anticipate that single-chain antibodies will disrupt these critical
HIV-host protein interactions required for reactivation of HIV latency. We have proof that the QUECEL can be
reactivated at 39.5°C and designed a high-complexity single-chain antibody library to selectively enrich for
candidates that prevent QUECEL reactivation. The prospective antiviral candidates will then be further enriched
in resting CD4+ T cells isolated from ART-treated aviremic patients, and we anticipate identifying potent single-
chain antibodies that disrupt the HIV-host protein interactions required to reactivate HIV from latency.
Our analytic bioassay is innovative because 1) mild heat shock activation is physiologically similar to the
intermittent cellular activation occurring in persistent HIV-infected tissue reservoirs and 2) the small size of single-
chain antibodies will increase the target range to the surface area of HIV proteins, effectively blocking critical
host-protein intera...

## Key facts

- **NIH application ID:** 10308728
- **Project number:** 5R21AI156897-02
- **Recipient organization:** UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
- **Principal Investigator:** Cheryl Stoddart
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $201,875
- **Award type:** 5
- **Project period:** 2020-12-01 → 2022-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10308728

## Citation

> US National Institutes of Health, RePORTER application 10308728, Single-chain antibodies to block HIV transcription and prevent reactivation from latently infected resting CD4+ T cells (5R21AI156897-02). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10308728. Licensed CC0.

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