# Characterization of CD8+ T cell killer activity and the mechanisms responsible for detachment from dead target cells

> **NIH NIH F32** · MASSACHUSETTS GENERAL HOSPITAL · 2020 · $69,306

## Abstract

Project Summary
 The adaptive CD8+ T cell response is essential for controlling viral replication during acute and chronic
stages of HIV infection and is a determining factor in HIV disease progression. However, despite induction of
HIV-specific CD8+ T cell responses, infected individuals achieve only partial control of infection. The inability to
eradicate HIV stems from the virus’ ability to evade potent T cell responses via epitope mutation and driving T
cell dysfunction. However, some persons are able to durably control viremia without the need for antiretroviral
medications. While control is associated with “protective” MHC-I alleles, it is not associated with the magnitude
of CD8+ T cell responses as measured by standard IFN-γ ELISPOT assays, but rather by functional ability to
mediate particularly potent cytolytic function. As yet, no study has fully characterized the CD8+ T cell
specificities that actually kill HIV-infected cells. Furthermore, previous work shows that CD8+ T cell cytokine
effector function is discordant with cytolytic function. This, in part, is attributed to inefficient effector-target
detachment, causing hyper-activation, and increased secretion of pro-inflammatory cytokines, which can
contribute to inflammation, a hallmark of HIV infection. Given the importance of CD8+ T cells to cure and
vaccine strategies, defining and engaging responses with optimal antiviral activity while limiting excessive T
cell activation is of utmost importance. For the first part of this proposal I hypothesize that HIV epitope
specificities of CD8+ T cells that kill rather than produce cytokine, an effect of perforin expression, better
associate with and predict control of HIV infection. To address this hypothesis, two methods, one using
perforin/IFN-γ secretion as a readout for cytolytic/cytokine function, and the other, a novel microfluidics-based
assay that couples single CD8+ T cells and targets, will be used to sort viable effector cells based on cytolytic
or cytokine function. Transcriptional analysis of sorted populations will provide insight into pathways that
regulate perforin and hence cytolytic function. In addition, perforin-based specificity mapping will compare HIV
specificities of cytolytic CD8+ T cells for HIV+ progressors and controllers, providing insight into optimal antiviral
responses to engage for potential therapeutics. For non-cytolytic effectors, which inefficiently detach from their
target, limiting their excessive activation is essential to prevent unwanted downstream inflammation. Previous
studies suggest that target cell apoptosis is required for effector-target detachment, yet the exact signal for
detachment is unknown. Thus, for the second part of this proposal, I hypothesize that CTLs detach from target
cells following recognition of phosphatidylserine (PS) exposure on the target, a common apoptotic signal.
Immunological techniques will be used to probe the involvement of PS and PS-binding inhibitory proteins, ...

## Key facts

- **NIH application ID:** 9863747
- **Project number:** 5F32AI143480-02
- **Recipient organization:** MASSACHUSETTS GENERAL HOSPITAL
- **Principal Investigator:** Kiera L. Clayton
- **Activity code:** F32 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $69,306
- **Award type:** 5
- **Project period:** 2019-02-01 → 2021-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9863747

## Citation

> US National Institutes of Health, RePORTER application 9863747, Characterization of CD8+ T cell killer activity and the mechanisms responsible for detachment from dead target cells (5F32AI143480-02). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9863747. Licensed CC0.

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