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Tissue-resident memory (TRM) CD8+T-cells are non-recirculating, long-lived cells housed in tissues that can confer protection against mucosal pathogens. Human immunodeficiency virus-1 (HIV-1) is a mucosal pathogen and the gastrointestinal tract is an important site of viral pathogenesis and transmission. Thus, CD8+TRMcells may be an important effector subset for controlling HIV-1 in mucosal tissues. This study sought to determine the abundance, phenotype, and functionality of CD8+TRMcells in the context of chronic HIV-1 infection. We found that the majority of rectosigmoid CD8+T-cells were CD69+CD103+S1PR1−and T-betLowEomesoderminNeg, indicative of a tissue-residency phenotype similar to that described in murine models. HIV-1-specific CD8+TRMresponses appeared strongest in individuals naturally controlling HIV-1 infection. Two CD8+TRMsubsets, distinguished by CD103 expression intensity, were identified. CD103LowCD8+TRMprimarily displayed a transitional memory phenotype and contained HIV-1-specific cells and cells expressing high levels of Eomesodermin, whereas CD103HighCD8+TRMprimarily displayed an effector memory phenotype and were EomesoderminNeg. These findings suggest a large fraction of CD8+T-cells housed in the human rectosigmoid mucosa are tissue-resident and that TRMcontribute to the anti-HIV-1 immune response. Further exploration of CD8+TRMwill inform development of anti-HIV-1 immune-based therapies and vaccines targeted to the mucosa.

Tissue-resident memory (TRM) CD8+T-cells are non-recirculating, long-lived cells housed in tissues that can confer protection against mucosal pathogens. Human immunodeficiency virus-1 (HIV-1) is a mucosal pathogen and the gastrointestinal tract is an important site of viral pathogenesis and transmission. Thus, CD8+TRMcells may be an important effector subset for controlling HIV-1 in mucosal tissues. This study sought to determine the abundance, phenotype, and functionality of CD8+TRMcells in the context of chronic HIV-1 infection. We found that the majority of rectosigmoid CD8+T-cells were CD69+CD103+S1PR1−and T-betLowEomesoderminNeg, indicative of a tissue-residency phenotype similar to that described in murine models. HIV-1-specific CD8+TRMresponses appeared strongest in individuals naturally controlling HIV-1 infection. Two CD8+TRMsubsets, distinguished by CD103 expression intensity, were identified. CD103LowCD8+TRMprimarily displayed a transitional memory phenotype and contained HIV-1-specific cells and cells expressing high levels of Eomesodermin, whereas CD103HighCD8+TRMprimarily displayed an effector memory phenotype and were EomesoderminNeg. These findings suggest a large fraction of CD8+T-cells housed in the human rectosigmoid mucosa are tissue-resident and that TRMcontribute to the anti-HIV-1 immune response. Further exploration of CD8+TRMwill inform development of anti-HIV-1 immune-based therapies and vaccines targeted to the mucosa.

Sequestering of latent HIV in follicular helper T cells within B-cell follicles that largely exclude cytotoxic T cells is a major barrier to cellular immune-based approaches to eradicate HIV. Here, we show that the clinical-grade human interleukin-15 (IL-15) superagonist ALT-803 activates and redirects simian immunodeficiency virus (SIV)–specific CD8+T cells from the peripheral blood into B-cell follicles. In agreement with the increased trafficking of SIV-specific cytotoxic T cells to sites of cryptic viral replication, lymph nodes of elite controlling macaques contained fewer cells expressing SIV RNA or harboring SIV DNA post–ALT-803 treatment. These data establish ALT-803 as an immunotherapeutic for HIV and other chronic viral pathogens that evade host immunity by persisting in B-cell follicles.

Sequestering of latent HIV in follicular helper T cells within B-cell follicles that largely exclude cytotoxic T cells is a major barrier to cellular immune-based approaches to eradicate HIV. Here, we show that the clinical-grade human interleukin-15 (IL-15) superagonist ALT-803 activates and redirects simian immunodeficiency virus (SIV)–specific CD8+ T cells from the peripheral blood into B-cell follicles. In agreement with the increased trafficking of SIV-specific cytotoxic T cells to sites of cryptic viral replication, lymph nodes of elite controlling macaques contained fewer cells expressing SIV RNA or harboring SIV DNA post–ALT-803 treatment. These data establish ALT-803 as an immunotherapeutic for HIV and other chronic viral pathogens that evade host immunity by persisting in B-cell follicles.

Spinocerebellar ataxia type 1 (SCA1) is a neurodegenerative disease caused by the expression of mutant ataxin-1 that contains an expanded polyglutamine tract. Overexpression of mutant ataxin-1 in Purkinje cells of transgenic mice results in a progressive ataxia and Purkinje cell pathology that are very similar to those seen in SCA1 patients. Two prominent aspects of pathology in the SCA1mice are the presence of cytoplasmic vacuoles and dendritic atrophy. We found that the vacuoles in Purkinje cells seem to originate as large invaginations of the outer cell membrane. The cytoplasmic vacuoles contained proteins from the somatodendritic membrane, including mGluR1, GluRΔ1/Δ2, GluR2/3, and protein kinase C (PKC) γ. Further examination of PKCγ revealed that its sequestration into cytoplasmic vacuoles was accompanied by concurrent loss of PKCγ localization at the Purkinje cell dendritic membrane and decreased detection of PKCγ by Western blot analysis. In addition, the vacuoles were immunoreactive for components of the ubiquitin/proteasome degradative pathway. These findings present a link between vacuole formation and loss of dendrites in Purkinje cells of SCA1mice and indicate that altered somatodendritic membrane trafficking and loss of proteins including PKCγ, are a part of the neuronal dysfunction in SCA1transgenic mice.

The invention of MHC‐tetramer technology to label antigen‐specific T cells has lead to a greatly enhanced understanding of T lymphocyte biology. This protocol describes the use of MHC class I tetramers to stain antigen‐specific T cells in tissue sections. In situ tetramer staining (IST) can be used to determine the localization, abundance, and phenotype of antigen‐specific T cells in native environments and in three‐dimensional space. IST is broadly applicable because it can be used to stain essentially any antigen‐specific T cell in any tissue for which MHC tetramers are available. IST can be combined with histochemistry and/or immunohistochemistry to permit visualization and characterization of antigen‐specific T cells relative to other cell types in stained tissue sections. Thus, IST is a useful and valuable component of MHC‐tetramer technology.