Identification and characterization of HIV-specific resident memory CD8+ T cells in human lymphoid tissue

Abstract

Current paradigms of CD8⁺ T cell-mediated protection in HIV infection center almost exclusively on studies of peripheral blood, which is thought to provide a window into immune activity at the predominant sites of viral replication in lymphoid tissues (LTs). Through extensive comparison of blood, thoracic duct lymph (TDL), and LTs in different species, we show that many LT memory CD8⁺ T cells bear phenotypic, transcriptional, and epigenetic signatures of resident memory T cells (T_RMs). Unlike their circulating counterparts in blood or TDL, most of the total and follicular HIV-specific CD8⁺ T cells in LTs also resemble T_RMs Moreover, high frequencies of HIV-specific CD8⁺ T_RMs with skewed clonotypic profiles relative to matched blood samples are present in LTs of individuals who spontaneously control HIV replication in the absence of antiretroviral therapy (elite controllers). Single-cell RNA sequencing analysis confirmed that HIV-specific T_RMs are enriched for effector-related immune genes and signatures compared with HIV-specific non-T_RMs in elite controllers. Together, these data indicate that previous studies in blood have largely failed to capture the major component of HIV-specific CD8⁺ T cell responses resident within LTs.

Fig. 1.. CD69 is not coupled to an early immune activation signature in HIV-infected LNs.

(A) Frequency of CD69 expression on total LN CD8⁺ T cells from HIV⁺ and HIV⁻ subjects. Red indicates ART⁻ and orange indicates ART⁺ in the HIV⁺ scatter plot group. (B) Frequency of CD69 expression on total blood (top) and LN (bottom) CD8⁺ T cells. Matched samples from one subject are shown in the representative flow cytometry plots. Lines connect matched samples across all subjects in the graph. (C) Correlation between the frequency of memory (non-CCR7^hi non-CD45RO⁻) CD8⁺ T cells and CD69 expression on total blood (top) and LN (bottom) CD8⁺ T cells. Blue: HIV⁻ subjects: red: HIV⁺ ART⁻ subjects; orange HIV⁺ ART⁺ subjects. (D) Frequency of CCR7⁻ CD69⁺ memory CD8⁺ T cells in HIV⁻ (blue) and HIV⁺ (red: ART⁻; orange: ART⁺) subjects. (E) Co-expression pattern of Ki-67 and CD69 in/on total LN CD8⁺ T cells from an HIV⁻ subject (left) and an HIV⁺ ART⁻ subject (right) with acute infection (Fiebig V). (F) Frequency of Ki-67^–/+ CD69⁺ CD8⁺ T cells in LNs from HIV⁺ subjects with acute infection (n = 7). (G) Expression intensity of CD69, ICOS, Ki-67, and CD38 in multidimensional viSNE space. viSNE plots were derived using 27576 cells (n = 17 subjects) and the markers shown in Fig. 1I. (H) The same viSNE display with sub-populations colored using the PhenoGraph implementation of Cytofkit (top). Distribution of CD69 expression over all 14 sub-populations derived using PhenoGraph (bottom). (I) Hierarchical clustering of expression intensity (z-score) for all assessed markers within the different sub-populations derived using PhenoGraph. Median and IQR are shown for all scatter/bar plots. **P < 0.01; ***P < 0.001. Conventional (fluorescence) flow cytometry was used for all stains in (A-F) and mass cytometry (CYTOF) was used in (G-I).

Fig. 2.. CD69⁺ CD8⁺ T cells display T_RM characteristics in LTs.

(A) Frequency of CD69 expression on memory CD8⁺ T cells (blue) in blood, spleen, iliac (Ili) LNs, mesenteric (Mes) LNs, and tonsils from HIV⁻ subjects. Asterisks denote statistical comparisons versus blood. (B) Frequency of CD69^–/+ cells among CCR7⁺ (T_CM) and CCR7⁻ (T_EM) CD8⁺ T cells. Bar plots are based on all subjects in (A). (C) Heat-map displaying expression frequency (blue = 0%; red = 100%) for the indicated markers among blood, spleen, IliLN, MesLN, and tonsil memory CD8⁺ T cells. (D) tSNE clustering on blood (red), spleen (orange), IliLN (blue), MesLN (green), and tonsil (black) memory CD8⁺ T cells. Values for the tSNE analysis are derived from all markers in (C). (E) CD69 expression on CD103⁺, CXCR5⁺, CD49a⁺, CCR5⁺, CXCR6⁺, and CD52⁺ memory CD8⁺ T cells from MesLNs. (F) Average expression frequency (blue = 0%; red = 100%) for the indicated markers among blood, spleen, IliLN, MesLN, and tonsil CD69⁻ and CD69⁺ memory CD8⁺ T cells. Colors denote average frequencies, derived from all subjects in (C). Median and IQR are shown for all scatter/bar plots. *P < 0.05; **P < 0.01; ***P < 0.001. Conventional flow cytometry was used for all stains in this figure.

Fig. 3.. CD69⁺ CD8⁺ T cells display functional and transcriptional T_RM signatures in LTs.

(A) RNA-seq heat-map showing differentially expressed genes (fold change > 2; P < 0.05) between human MesLN memory CD69⁻ and CD69⁺ CD8⁺ T cells. (B) Ingenuity pathway analysis based on all differentially expressed genes (P < 0.05) between CD69⁻ and CD69⁺ CD8⁺ T cells in the RNA-seq dataset. The top pathways involved in the “physiological system development and function” arm are shown in the table. (C) Differential expression patterns of T_RM-related and T_CM/EM-related genes between human LN memory CD69⁻ and CD69⁺ CD8⁺ T cells (top) and between splenic CD69⁻ and CD69⁺ CD8⁺ T cells from P14 TCR-transgenic mice (bottom). (D) ATAC-seq volcano plot showing open chromatin regions adjacent to specific genes. Green marks ATAC-seq peaks that are differentially enriched (fold change > 2; P < 0.05) in human hepatic LN memory CD69⁻ and CD69⁺ CD8⁺ T cells. (E) ATAC-seq tracks from human LN memory CD69⁻ (red) and CD69⁺ (blue) CD8⁺ T cells. (F) Enriched ATAC-seq de novo motifs for CD69⁺ (left) and CD69⁻ (right) CD8⁺ T cells (G) Human memory CD69⁻ and CD69⁺ CD8⁺ T cells from spleen, tonsil, and hepatic LNs (n = 2 each) were assessed over time for CD69 expression in the presence or absence of rhIL-7. Lines represent mean ± SD. Conventional flow cytometry was used for all stains in this figure.

Fig. 4.. Anatomical distribution of CD69⁺ CD8⁺ T cells in LNs and thoracic duct lymph.

(A) Whole imaged confocal microscopy of mesLN from human (left) and zoomed in area (middle). Histocytometry gating strategy to identify localization of CD8⁺ T and B cells in the LNs (right). (B) Identification of B cell follicles (red) and extra-follicular areas (green) in the whole imaged area using histocytometry (left). Middle graphs, shows absolute numbers of CD69⁺CD103⁻ and CD69⁺CD103⁺ within all imaged extra-follicular (EF) and B cell follicular (F) areas for three imaged LNs. Example of histocytometry imaging showing the distribution of CD8⁺CD69⁺ cells within the zoomed in LN area. (C) Localization in the human body of the thoracic duct. (D) Flow plots of CD69 expression on human thoracic duct lymph (TDL) and mesenteric LN (MesLN) memory CD8⁺ T cells from two unmatched subjects. Frequency of CD69⁺ CD8⁺ T cells in TDL (n = 7 subjects) and LTs from all subjects (n = 25) in Fig. 2A. (E) Frequency of CD69 expression on blood, inguinal (Ing) LN, MesLN, tonsil, spleen, and TDL memory (non-CD28⁺ non-CD95⁻) CD8⁺ T cells from sample-matched rhesus macaques. Each color indicates fluid/tissue from one specific rhesus macaque. Asterisks denote statistical comparisons versus TDL. *P < 0.05; **P < 0.01; ***P < 0.001. Conventional flow cytometry was used for all stains in this figure.

Fig. 5.. Majority of HIV-specific CD8⁺ T cells display a T_RM phenotype in LNs.

(A) Flow cytometry plots of on memory CD8+ T cells showing CD69 expression on matched HIV-tetramer⁺ cells in blood and LNs (left), and matched HIV-tetramer⁺ cells in blood and TDL (middle). Frequency of CD69 expression on HIV-tetramer⁺ cells in blood (n = 13 subjects), ART⁻ LNs (n = 4 subjects), ART⁺ LNs (n = 4 subjects), and TDL (n = 7 subjects) (right). (B) Distribution of LN HIV-tetramer⁺ (spec) CD69⁺ CD8⁺ T cells among the naïve (CD45RO⁻ CCR7⁺), T_CM (CD45RO⁺ CCR7⁺), T_EM (CD45RO⁺ CCR7⁻), and effector (T_EFF; CD45RO⁻ CCR7⁻) compartments. (C) CD69 and CD103 expression profiles for blood (blue), LN (red: ART⁻; orange: ART⁺), and TDL (yellow) HIV-specific CD8⁺ T cells. (D) Representative flow cytometry plots showing memory CMV-tetramer⁺ (left) and HIV-tetramer⁺ (right) CD8⁺ T cell frequencies in blood (top) and LNs (bottom) from the same subject. (E) Frequency of CD69 and CD103 expression on LN CMV-NV9-specific and HIV-FK10-specific CD8⁺ T cells in the same subjects with detectable tetramer⁺ responses to both viruses. Each color represents a matched subject and a matched tetramer⁺ response. (F) Representative flow cytometry plots showing CD69 expression on Perforin⁺ Granzyme B (GzmB)⁺ HIV-specific CD8⁺ T cells in LNs (left). Frequency of CD69^–/+ cells among Perforin⁺ (n = 20 responses) and GzmB⁺ (n = 16 responses) HIV-specific CD8⁺ T cells in ART⁺ and ART⁻ LNs (right). (G) Flow plots showing CXCR5 and CD69 co-expression on blood, LN, and TDL memory CD8⁺ T cells in HIV⁺ subjects (matched for blood and LNs, but not for TDL). Frequency of CXCR5 expression on memory CD8⁺ T cells in blood, LNs (red: ART⁻; orange: ART⁺), and TDL. (H) Frequency of CD69 expression on blood, LN, and TDL CXCR5⁺ memory CD8⁺ T cells in HIV⁺ subjects. (I) Frequency of CCR7 expression on LN CD69⁺ CXCR5⁺ memory CD8⁺ T cells in HIV⁺ subjects. Bar plots are based on all subjects in Fig. 5A. (J) Representative flow cytometry plots showing CXCR5 and CD69 co-expression on blood, LN, and TDL HIV-tetramer⁺ CD8⁺ T cells (matched for blood and LNs, but not for TDL). (K) Frequency of CD69 expression on blood (n = 18 responses), LN (n = 21 responses), and TDL (n = 10 responses) HIV-specific CXCR5⁺ CD8⁺ T cells. (L) Frequency of CCR7 expression on LN (n = 21 responses) HIV-specific CD69⁺ CXCR5⁺ CD8⁺ T cells. (M) Frequency of CD69⁺ CXCR5⁺ cells among LN CMV-specific and HIV-specific CD8⁺ T cells in subjects with detectable tetramer⁺ responses to both viruses. Each dot represents a single tetramer⁺ response in all scatter plots. Each color represents a matched subject and a matched tetramer⁺ response. *P < 0.05, **P < 0.01; ***P < 0.001. Conventional flow cytometry was used for all stains in this figure.

Fig. 6.. SIV-specific CD8+ T cells develop TRM characteristics over time.

Representative flow cytometry plots showing CD69 expression on blood (top) and superficial LN (sLN; bottom) SIV-specific (Mamu A*01-Gag-CM9) CD8⁺ T cells at 13 and 90 days post-infection (dpi; left). Longitudinal dynamics of CD69 (blue) and Ki-67 (red) expression on/in blood, sLN, MesLN, and spleen SIV-CM9 or TL9-specific CD8⁺ T cells (13 dpi: n = 12; 90 dpi: n = 3). The longitudinal SIV-CM9 or TL9-specific CD8⁺ T cell response is plotted at each time point as mean ± SD. *P < 0.05, **P < 0.01; ***P < 0.001. Conventional flow cytometry was used for all stains in this figure.

Fig. 7.. Elite controllers exhibit high magnitudes of CD69+ HIV-specific CD8+ T cells in LNs.

(A) Representative flow cytometry plots of memory CD8+ T cells showing CD69 expression on HIV-tetramer⁺ cells in matched blood and LN samples from an HIV elite controller (EC). (B) Relative distribution of HIV-specific CD8⁺ T cells in blood and LNs from elite controllers (black) and other HIV⁺ subjects (red: ART⁻; orange: ART⁺). (C) Magnitude of LN HIV-tetramer⁺ CD69⁺ CD8⁺ T cell responses in elite controllers and other HIV⁺ subjects (red: ART⁻; orange: ART⁺). (D) Magnitude of LN HIV-tetramer⁺ CD69⁺ CD8⁺ T cell responses specific for immunodominant HLA-B*5701-restricted and non-HLA-B*5701-restricted epitopes in elite controllers (n = 2). Data points were only included where both HLA-B*5701⁺ and HLA-B*5701⁻ tetramers were tested to avoid analysis biases. Each dot represents a single tetramer⁺ response in all scatter plots. *P < 0.05; **P < 0.01. Conventional flow cytometry was used for all stains in this figure.

Fig. 8.. Distribution of HIV-specific clonotypes between LN and blood.

(A) Single-cell (sc) RNA-seq was conducted on CD69⁺ and CD69⁻ index sorted HLA-B*2705-restricted and/or HLA-B*5701-restricted Gag-specific CD8⁺ T cells from LNs of two elite controllers. The heat-map (left) illustrates the single-cell gene expression variability of differentially expressed genes (P < 0.01) and violin plots (right) immune-related genes differentially expressed between CD69⁺ and CD69⁻ single HIV-specific CD8⁺ T cells. (B) CDR3 amino acid sequence, and percent frequency are shown for each HLA-B*2705-restricted and HLA-B*5701-restricted clonotype. The frequency of CD69 expression for each clonotype was obtained from single-cell index data (right). (C) CD69 expression on LN clonotypes where higher frequencies of specific clonotypes are present in LNs versus blood (LN > blood; n = 7) or vice versa (LN < blood; n = 7). Bars show mean ± SD. (D) Correlation between CD69 expression on LN clonotypes and the distribution of clonotypes between LNs and blood (frequency of a given clonotype in LNs minus the corresponding frequency in blood). Data points were only included where at least one clonotype was present in both compartments. *P < 0.05; **P < 0.01. Conventional flow cytometry was used for all stains in this figure.