Background: Although lymphoma is one of the most common malignancies in dogs, remission rates and survival times remain stagnant. Treatment with a multi-agent chemotherapy protocol induces remission for less than one year and the majority of patients relapse. Fewer than 25% of dogs live longer than two years with the currently available treatments. Targeted immunotherapy using checkpoint molecule blockade of PD-1 and PD-L1 shows promise for various types of human cancer, including relapsed/refractory lymphoma; however, little is known regarding the role of these checkpoint molecules in canine lymphoma. Objectives: To determine the patterns of expression of mRNAs encoding PD-1 and its ligands PD-L1 and PD-L2 in lymphoma and reactive lymphoid hyperplasia controls. Methods: Retrospective: formalin-fixed paraffin-embedded (FFPE) tissue from dogs with untreated lymphoma (n=10) and reactive lymphoid hyperplasia (n=10). Prospective: fine-needle aspirates (FNAs) from dogs with untreated lymphoma (n=10) and reactive lymphoid hyperplasia (n=10). Total RNA was extracted, and expression of PD-1, PD-L1, and PD-L2 was measured using qRT-PCR analysis of random-primed cDNA. Checkpoint molecule expression levels were determined using the 2^∆∆CT method. Lymphoma immunophenotype was assessed using immunohistochemical analysis of CD3 and CD79a (FFPE) and review of patient medical records (FNA). Data analysis included Wilcoxon ranksum tests, Dunn's procedure of multiple comparisons, Kruskal-Wallis tests, and regression within an ANOVA. Significance at P < 0.05. Results: PD-1, PD-L1, and PD-L2 expression (normalized internally to 18S rRNA) was lower in lymphoma compared to reactive lymphoid hyperplasia (FFPE); the difference was significant for PD-1 and PD-L2. PD-1 and PD-L2 expression was lower in lymphoma compared to reactive lymphoid hyperplasia (FNA); the difference was significant for PD-1. PD-1, PD-L1, and PD-L2 expression was lower in B cell lymphoma compared to reactive lymphoid hyperplasia (FFPE); this difference was significant for PD-1 and PD-L2. PD-1 and PD-L2 expression was lower in B cell lymphoma compared to reactive lymphoid hyperplasia (FNA); the difference was significant for PD-1. The higher relative abundance of PD-L1 vs PD-1 and PD-L2 vs PD-1 was significantly different between lymphoma and reactive lymphoid hyperplasia (FFPE and FNA). Conclusions: In this study, checkpoint molecule expression was not upregulated in canine lymphoma relative to canine reactive lymphoid hyperplasia, suggesting a limited application of PD-1 and PD-L1 blockade in canine lymphoma. The ligand:receptor relative abundance imbalances reflect the lower PD-1 expression relative to PD-L1 and PD-L2 in lymphoma. Although these results do not suggest that checkpoint inhibitors would be useful for treatment, they give insight into the mechanisms of unchecked lymphocyte proliferation in canine lymphoma. / Master of Science / Lymphoma, a cancer of the white blood cells in the body, is one of the most common malignancies in dogs. Although treatment with a multi-agent chemotherapy protocol results in high remission rates, the remission duration is usually less than one year, with the majority of patients relapsing. In an effort to improve remission rates and survival times, scientists have been working to develop therapeutic interventions that target specific points in the development and replication cycle of a cancer cell. One such strategy, targeting checkpoint molecules programed death (PD)-1 and PD-L1, has shown promise for several different types of human cancers, including lymphoma. PD-1 is a receptor on T cells, which together with its ligands, PD-L1 and PD-L2, decreases lymphocyte function when activated. This is a protective mechanism, acting to inhibit sustained harmful inflammation in a normal healthy dog. Some cancers have taken advantage of this pathway, increasing expression of PD-L1 or L-L2 in order to evade detection by the immune system. To date, little is known regarding the role and expression of these immune checkpoint molecules in dogs with lymphoma. We sought to evaluate if PD-1, PD-L1 and PD-L2 expression is significantly increased in canine lymphoma compared to reactive lymphoid hyperplasia controls. Tissue samples were collected from two sources. Cytology samples of lymphoma and reactive lymphoid hyperplasia were collected by fine needle aspiration from clinical patients. Formalin fixed paraffin embedded tissue samples of lymphoma and reactive lymphoid hyperplasia were collected from the archived tissue bank. Using a molecular analysis technique called quantitative reverse transcription PCR (qRT-PCR) we measured the amount of messenger RNA (mRNA) encoding PD-1 and its ligands PD-L1 and PD-L2 in lymphoma and in reactive lymphoid hyperplasia controls. In our results we did not observe an upregulation in the expression of checkpoint molecules in canine lymphoma relative to canine reactive lymphoid hyperplasia. This suggests there may be a limited therapeutic application for PD-1 and PD-L1/PD-L2 blockade in canine lymphoma. Although these results do not suggest that checkpoint inhibitors would be useful for treatment, they give insight into the mechanisms of unchecked lymphocyte proliferation in canine lymphoma.

While the human immunodeficiency virus (HIV) can be managed with antiretroviral therapy (ART), there is no cure for the disorder. If ART is discontinued, viral RNA levels rapidly increase in most individuals due to the presence of a cell-mediated hidden replication competent viral burden known as the viral reservoir. In order to successfully cure this disease, a mechanism to eliminate the viral reservoir must be developed. Preliminary research completed using a toll-like-receptor agonist 7 (TLR7) has shown favorable results supporting this goal. In a simian immunodeficiency virus (SIV) model, dosing rhesus macaques (RMs) with TLR7 agonists resulted in the development of controlled viremia. A controlled RM is a SIV positive animal that is able to maintain an undetectable viral load without continued therapeutic intervention. In cases of controlled SIV/HIV, viral RNA no longer replicates despite the discontinuation of all treatment. This implies that the viral reservoir is either completely eliminated or severely reduced. In this study, we quantified expression levels of several immune checkpoint and activation markers including CD69, CD39, CXCR5, TCF7, PD-1, PD-L1, TIGIT, CTLA-4, Tim-3, and Lag-3 on isolated peripheral blood mononuclear immune cells (PBMCs) [including CD4+ T cells, CD8+ T cells, natural killer (NK) cells, and B cells] in both controlled and non-controlled RMs. Our goal was to identify possible mechanisms by which controlled RMs are able to successfully modulate the host immune response after discontinuing TLR7 agonist treatment. The subjects each received one of two different TLR7 agonists (GS-9620 and GS-986). Isolated peripheral blood mononuclear cells (PBMCs) were obtained from two controlled RMs and two non-controlled RMs. Samples were analyzed using flow cytometry to identify and quantify levels of markers above. Expression levels of PD-1 and PD-L1 were elevated in PBMCs obtained from non-controlled RMs when compared to levels seen in controlled RMs. In contrast, levels of TIGIT and CTLA4 were downregulated in samples obtained from the controlled RMs. This suggests that immune checkpoint markers responsible for viral control and SIV/HIV pathogenesis have different functional roles. Additionally, the controlled RMs showed high expression of CD69 and CD39 on B cells and increased levels of CXCR5 on CD4+ T cells. This suggests that newly activated B cells likely contribute to the observed improvements in immune function. The results obtained provide favorable support for the potential role of immune checkpoint blockade as an HIV-specific immunotherapy that may contribute to the development of a controlled population. However, it is worthwhile to note that this study was completed using a relatively small sample size (n=4). Thus, interpretations of the findings herein must be replicated with a larger sample prior to forming any definitive conclusions.

The immunogenicity of breast cancer (BC) is quite heterogeneous among the clinical subtypes, with immune responses identified most frequently in triple negative (TNBC) and HER2-positive tumors. The extent, spatial localization, distribution patterns, organization and phenotype of the BC immune infiltrate are currently being widely investigated but require standardization before they can be used clinically. One highly relevant unmet clinical need is to understand how immune features are linked to prognosis and potential benefit from treatments, particularly immunotherapy. The present work investigated tumor-infiltrating lymphocytes (TIL), tertiary lymphoid structures (TLS), the expression of multiple targetable inhibitory immune checkpoint molecules (PD-1, PD-L1 and PD-L2, CTLA-4, LAG3 and TIM3) and their clinical relevance in primary BC. Different technical approaches were employed including: flow cytometry (FC) on fresh tissue homogenates; immunohistochemistry (IHC) and immunofluorescence (IF) on formalin-fixed paraffin embedded (FFPE) tissue blocks from untreated primary tumors; and gene expression on a large dataset of BC patients with available long-term survival data. Flow cytometric analysis of PD-1 expression and its principal ligands PD-L1 and PD-L2 together with CTLA-4, LAG3 and TIM3 on TIL in fresh untreated primary tumors revealed that PD-1 and CTLA-4 are most highly expressed on BC TIL and PD-L1 is the principal PD-1 ligand in BC. Immune checkpoint molecule expression parallels the extent of TIL infiltration and TLS presence and number, with the patterns detected similar to that observed in secondary lymphoid organs. Significantly improved disease-specific survival (DSS) has been associated with PD-1hi HER2-enriched and PD-L1hi, PD-L2hi and CTLA-4hi basal-like BC; however there is significant heterogeneity between individual tumors even within the same subtype. These observations suggest that determining expression levels of multiple targetable inhibitory immune checkpoint molecules in patients might help to successfully target them in BC patients most likely to respond.We examined the concordance between two experienced immuno-pathologists who read 800 IHC-stained slides from five independent series over a period of four years to determine the reproducibility of assessing multiple immune biomarkers. This included scoring TIL, TLS, PD-1 and PD-L1 together with detailed information on the spatial localization and cell types expressing these molecules in the tumor microenvironment (TME). The interobserver reproducibility for the assessment of TIL and TLS was consistently good to excellent overtime, while the concordance for PD-L1 evaluation ranged from fair to excellent when it was only expressed on tumor cells (TC); and the concordance for PD-1 evaluation was fair to excellent when it was expressed in TLS and evaluated in primary tumors. Neither PD-L1 expression by TC, nor PD-1 expression within a TLS was significantly associated with prognosis in our datasets.The extent of TIL, TLS and PD-1 and PD-L1 expression were studied in a cohort of TNBC patients who underwent genetic counseling for their personal/familial history of BC or ovarian cancer (OC). This study revealed a remarkable similarity in patterns of immune infiltration between the two cohorts. Interestingly, a higher prevalence of TIL intermediate cases (≥10% and <50% TIL) was detected in the BRCA-mutated cohort, suggesting that this group may be more immunogenic.We next investigated whether the extent and presence of these immune parameters were associated with prognosis in the most highly infiltrated, aggressive BC subtypes (TNBC and HER2-positive). We determined the ideal cut-off for each subtype (TNBC and HER2-positive) to use TIL as a categorical variable. This study found a consistent prognostic impact from TIL (in any tumor compartment including stromal, intratumoral and global areas) and a novel association between PD-L1 expression within TLS and better survival in TNBC. This last effect was driven by baseline stromal TIL, strengthening the importance of reliably quantifying the levels of TIL in BC. Overall, our analyses show that among the targetable inhibitory immune checkpoint molecules investigated in BC, PD-1 and CTLA-4 are most highly expressed by BC TIL and are associated with higher infiltration of TIL; PD-L1 is the principal ligand for PD-1; TIL and TLS are reproducibly scored on IHC-stained tissues; and TIL levels are associated with a better prognosis in TNBC independent of their location in the TME at optimal cut-offs. Our data also provide new insight on targetable inhibitory immune checkpoint molecule expression and location as well as showing a prognostic role for TIL assessed by IHC in primary BC, which identifies these biomarkers as ideal candidates for further investigation. / Doctorat en Sciences médicales (Médecine) / info:eu-repo/semantics/nonPublished