Banff 2022 liver group meeting report: monitoring long term allograft health.

The Banff Working Group on Liver Allograft Pathology met in September 2022. Participantsincluded hepatologists, surgeons, pathologists, immunologists and histocompatibility specialists.Presentations and discussions focused on the evaluation of long-term allograft health, including noninvasive and tissue monitoring, immunosuppression optimisation and long-term structural changes.Potential revision of the rejection classification scheme to better accommodate and communicate lateT cell-mediated rejection patterns and related structural changes, such as nodular regenerativehyperplasia, were discussed. Improved stratification of long-term maintenance immunosuppression tomatch the heterogeneity of patient settings will be central to improving long-term patient survival.Such personalised therapeutics are in turn contingent on better understanding and monitoring ofallograft status within a rational decision-making approach, likely to be facilitated in implementationwith emerging decision support tools. Proposed revisions to rejection classification emerging fromthe meeting include incorporation of interface hepatitis and fibrosis staging. These will be opened toonline testing, modified accordingly and subject to consensus discussion leading up to the next Banffconference

Landscape of somatic single nucleotide variants and indels in colorectal cancer and impact on survival

Colorectal cancer (CRC) is a biologically heterogeneous disease. To characterize its mutational profile, we conduct targeted sequencing of 205 genes for 2,105 CRC cases with survival data. Our data shows several findings in addition to enhancing the existing knowledge of CRC. We identify PRKCI, SPZ1, MUTYH, MAP2K4, FETUB, and TGFBR2 as additional genes significantly mutated in CRC. We find that among hypermutated tumors, an increased mutation burden is associated with improved CRC-specific survival (HR=0.42, 95% CI: 0.21-0.82). Mutations in TP53 are associated with poorer CRC-specific survival, which is most pronounced in cases carrying TP53 mutations with predicted 0% transcriptional activity (HR=1.53, 95% CI: 1.21-1.94). Furthermore, we observe differences in mutational frequency of several genes and pathways by tumor location, stage, and sex. Overall, this large study provides deep insights into somatic mutations in CRC, and their potential relationships with survival and tumor features. Large scale sequencing study is of paramount importance to unravel the heterogeneity of colorectal cancer. Here, the authors sequenced 205 cancer genes in more than 2000 tumours and identified additional mutated driver genes, determined that mutational burden and specific mutations in TP53 are associated with survival odds

Phenotypic T Cell Exhaustion in a Murine Model of Bacterial Infection in the Setting of Pre-Existing Malignancy

<div><p>While much of cancer immunology research has focused on anti-tumor immunity both systemically and within the tumor microenvironment, little is known about the impact of pre-existing malignancy on pathogen-specific immune responses. Here, we sought to characterize the antigen-specific CD8⁺ T cell response following a bacterial infection in the setting of pre-existing pancreatic adenocarcinoma. Mice with established subcutaneous pancreatic adenocarcinomas were infected with <i>Listeria monocytogenes</i>, and antigen-specific CD8⁺ T cell responses were compared to those in control mice without cancer. While the kinetics and magnitude of antigen-specific CD8⁺ T cell expansion and accumulation was comparable between the cancer and non-cancer groups, bacterial antigen-specific CD8⁺ T cells and total CD4⁺ and CD8⁺ T cells in cancer mice exhibited increased expression of the coinhibitory receptors BTLA, PD-1, and 2B4. Furthermore, increased inhibitory receptor expression was associated with reduced IFN-γ and increased IL-2 production by bacterial antigen-specific CD8⁺ T cells in the cancer group. Taken together, these data suggest that cancer's immune suppressive effects are not limited to the tumor microenvironment, but that pre-existing malignancy induces phenotypic exhaustion in T cells by increasing expression of coinhibitory receptors and may impair pathogen-specific CD8⁺ T cell functionality and differentiation.</p></div

Antigen-specific T cell cytokine production in control and cancer mice following intracellular cytokine stimulation.

<p>CD8⁺Thy1.1⁺ T cells in the control and cancer groups were stimulated with SIINFEKL peptide. No statistically significant differences were noted in intracellular production of IFN-γ or IL-2; n = 8–10.</p

Correlation of coinhibitory receptor expression to antigen-specific cytokine production.

<p>A) The frequency of PD-1, 2B4, and BTLA expression was compared to the frequency of cells producing IFN-γ. Increased inhibitory receptor expression is correlated with reduced cytokine production. n = 8–10 (PD-1 and BTLA) and 4–5 (2B4). B) The frequency of PD-1, 2B4, and BTLA expression was compared to the frequency of cells producing IL-2. Increased inhibitory receptor expression is correlated with increased cytokine production; n = 8–10 (PD-1 and BTLA) and 4–5 (2B4).</p

Experimental design and bacterial antigen-specific immune responses.

<p>A) C57BL/6 mice were randomized to control vs. cancer groups. The cancer group received a subcutaneous injection of Pan02 cells. Following 3 weeks, all mice were given an IV injection of transgenic (Tg) T cell receptor (TCR) CD8⁺Thy1.1⁺ T cells. After 24 hours, uninfected mice were sacrificed for the day 0 time point, and all other mice were given an intraperitoneal injection of LM-OVA and underwent spleen collections at days 5 and 14 post-infection. B) At days 5 or 14 following infection, there were no significant differences in antigen-specific CD8+T cells expansion between the control and cancer groups. The mean frequencies in control vs. cancer were 6.97±1.49% vs. 6.89±2.49% at day 5, respectively and 5.38±0.73% vs. 4.90±1.19% at day 14, respectively; n = 8–10 at all time points.</p

Effect of cancer and LM-OVA infection on coinhibitory receptor expression.

<p>A) Data presented is following selection of the CD8⁺Thy1.1⁺ T cell population. CD8⁺Thy1.1⁺ T cells in cancer group had increased mean frequencies of BTLA⁺ T cells. They were 8.58±1.07% in control vs. 20.72±5.58% in cancer mice following infection (*p<0.05; n = 8–10) at day 5. Mean frequencies of 2B4 (n = 4–5) and PD-1 (n = 8–10) had a trend toward increased expression in the cancer group, but were not statistically significant. B) In the absence of infection (day 0), the control and cancer groups did not have any significant differences in the expression or co-expression of 2B4, BTLA, and PD-1 on CD4⁺ T cells. At day 5, however, CD4⁺ T cells in the cancer group expressed a higher frequency of BTLA (4.03±0.46 vs. 6.77±0.59) and 2B4 (2.67±0.22 vs. 3.95±0.25). The inhibitory profile was further altered when looking at co-expression. The cancer group had higher expression of PD-1⁺BTLA⁺ (3.76±0.47 vs. 5.65±0.42) and 2B4⁺PD-1⁺ (2.50±0.23 vs. 3.76±0.26) CD4⁺ T cells. Following resolution of infection at day 14, the expression of 2B4 (n = 4–5), 2B4⁺PD-1⁺ (n = 4–5), or PD-1 was no longer different in both groups, however, the frequency of expression CD4⁺ PD-1⁺BTLA⁺ T cells remained elevated in the cancer group (3.99±0.44 vs. 5.56±0.48). **p<0.01; *p<0.05; n = 8–10 at days 0, 5, and 14, unless otherwise stated. C) At baseline (day 0), cancer mice had reduced expression of CD8⁺PD-1⁺ T cells compared to control mice (14.03±0.61 in control vs. 11.91±0.47 in cancer). However, expression of 2B4, BTLA, 2B4⁺PD-1⁺ or PD-1⁺BTLA⁺ was unchanged prior to infection. At day 5 following infection, cancer mice had increased frequencies of expression of CD8⁺BTLA⁺ (8.78±0.95 vs. 13.66±0.64) and CD8⁺PD-1⁺BTLA⁺ (6.55±0.83 vs. 9.22±0.47) T cells. Following resolution of infection at day 14, only the mean frequency of BTLA expression in the cancer group remained elevated (6.72±1.40 vs. 8.76±2.03); **p<0.01; *p<0.05; n = 8–10.</p