Regulatory T Cells Occupy an Isolated Niche in the Intestine that Is Antigen Independent

Summary: Regulatory T cells (Tregs) are CD4+ T cells that maintain immune homeostasis and prevent autoimmunity. Like all CD4+ T cells, Tregs require antigen-specific signals via T cell receptor-major histocompatibility complex class II (TCR-MHCII) interactions for their development. However, the requirement for MHCII in Treg homeostasis in tissues such as intestinal lamina propria (LP) is unknown. We examined LP Treg homeostasis in a transgenic mouse model that lacks peripheral TCR-MHCII interactions and generation of extrathymic Tregs (iTregs). Thymically generated Tregs entered the LP of weanlings and proliferated independently of MHCII to fill the compartment. The adult LP was a closed niche; new thymic Tregs were excluded, and Tregs in parabiotic pairs were LP resident. The isolated LP niche was interleukin-2 (IL-2) independent but dependent on commensal bacteria. Thus, an LP Treg niche can be filled, isolated, and maintained independently of antigen signals and iTregs. This niche may represent a tissue-specific mechanism for maintaining immune tolerance. : Regulatory T cells (Tregs) maintain immune homeostasis and prevent autoimmunity. Korn et al. describe a unique Treg niche in the intestinal lamina propria that does not require T cell receptor signals for development or maintenance and is physiologically isolated from the Tregs that circulate through lymphoid organs. Maintenance of this niche is dependent upon local commensal bacteria. The authors propose that this isolated niche may represent a tissue-specific mechanism for maintaining immune tolerance

Early emergence of anti-HCV antibody implicates donor origin in recipients of an HCV-infected organ

Hepatitis C virus (HCV) seroconversion among HCV-uninfected transplant recipients from HCV-infected (NAT+/Antibody+) or HCV-exposed (NAT-/Antibody+) donors has been reported. However, the origin of anti-HCV antibody and the implications of seroconversion remain unknown. We longitudinally tested plasma from HCV-uninfected kidney (n = 31) or heart transplant recipients (n = 9) of an HCV NAT+ organ for anti-HCV antibody (both IgG and IgM isotypes). Almost half of all participants had detectable anti-HCV antibody at any point during follow-up. The majority of antibody-positive individuals became positive within 1-3 days of transplantation, and 6 recipients had detectable antibody on the first day posttransplant. Notably, all anti-HCV antibody was IgG, even in samples collected posttransplant day 1. Late seroconversion was uncommon (approximate to 20%-25% of antibody+ recipients). Early antibody persisted over 30 days in kidney recipients, whereas early antibody dropped below detection in 50% of heart recipients within 2 weeks after transplant. Anti-HCV antibody is common in HCV-uninfected recipients of an HCV NAT+ organ. The IgG isotype of this antibody and the kinetics of its appearance and durability suggest that anti-HCV antibody is donor derived and is likely produced by a cellular source. Our data suggest that transfer of donor humoral immunity to a recipient may be much more common than previously appreciated

Trial of Transplantation of HCV-Infected Kidneys into Uninfected Recipients

An open-label pilot trial involving 10 patients shows that hepatitis C virus genotype 1–infected kidneys transplanted into HCV-negative recipients, followed by direct-acting antiviral therapy, can result in excellent allograft function with cure of HCV infection. To the Editor: Waiting times for kidney transplants exceed 3 to 5 years in many parts of the United States. 1 Yet more than 500 high-quality kidneys from deceased donors with hepatitis C virus (HCV) infection are discarded annually. 2 , 3 Direct-acting antiviral agents, which are associated with high HCV cure rates and manageable side effects, have created the potential to substantially increase the number of kidney transplants by making HCV-infected kidneys available to HCV-negative candidates on the waiting list. 4 , 5 In this open-label, single-group, pilot trial at the University of Pennsylvania (Transplanting Hepatitis C Kidneys into Negative Kidney Recipients [THINKER]; ClinicalTrials.gov . . 

Twelve-Month Outcomes After Transplant of Hepatitis C-Infected Kidneys Into Uninfected Recipients A Single-Group Trial

Background: Organs from hepatitis C virus (HCV)-infected deceased donors are often discarded. Preliminary data from 2 small trials, including THINKER-1 (Transplanting Hepatitis C kidneys Into Negative KidnEy Recipients), suggested that HCV-infected kidneys could be safely transplanted into HCV-negative patients. However, intermediate-term data on quality of life and renal function are needed to counsel patients about risk. Objective: To describe 12-month HCV treatment outcomes, estimated glomerular filtration rate (eGFR), and quality of life for the 10 kidney recipients in THINKER-1 and 6-month data on 10 additional recipients. Design: Open-label, nonrandomized trial. (ClinicalTrials.gov: NCT02743897) Setting: Single center. Participants: 20 HCV-negative transplant candidates. Intervention: Participants underwent transplant with kidneys infected with genotype 1 HCV and received elbasvir-grazoprevir on posttransplant day 3. Measurements: The primary outcome was HCV cure. Exploratory outcomes included 1) RAND-36 Physical Component Summary (PCS) and Mental Component Summary (MCS) quality-of-life scores at enrollment and after transplant, and 2) posttransplant renal function, which was compared in a 1:5 matched sample with recipients of HCV-negative kidneys. Results: The mean age of THINKER participants was 56.3 years (SD, 6.7), 70% were male, and 40% were black. All 20 participants achieved HCV cure. Hepatic and renal complications were transient or were successfully managed. Mean PCS and MCS quality-of-life scores decreased at 4 weeks; PCS scores then increased above pretransplant values, whereas MCS scores returned to baseline values. Estimated GFRs were similar between THINKER participants and matched recipients of HCV-negative kidneys at 6 months (median, 67.5 vs. 66.2 mL/min/1.73m(2); 95% CI for between-group difference, -4.2 to 7.5 mL/min/1.73m(2)) and 12 months (median, 72.8 vs. 67.2 mL/min/1.73m(2); CI for between-group difference, -7.2 to 9.8 mL/min/1.73m(2)). Limitation: Small trial. Conclusion: Twenty HCV-negative recipients of HCV-infected kidneys experienced HCV cure, good quality of life, and excellent renal function. Kidneys from HCV-infected donors may be a valuable transplant resource

Transplanting hepatitis C virus-infected hearts into uninfected recipients: A single-arm trial

The advent of direct-acting antiviral therapy for hepatitis C virus (HCV) has generated tremendous interest in transplanting organs from HCV-infected donors. We conducted a single-arm trial of orthotopic heart transplantation (OHT) from HCV-infected donors into uninfected recipients, followed by elbasvir/grazoprevir treatment after recipient HCV was first detected (NCT03146741; sponsor: Merck). We enrolled OHT candidates aged 40-65 years; left ventricular assist device (LVAD) support and liver disease were exclusions. We accepted hearts from HCV-genotype 1 donors. From May 16, 2017 to May 10, 2018, 20 patients consented for screening and enrolled, and 10 (median age 52.5 years; 80% male) underwent OHT. The median wait from UNOS opt-in for HCV nucleic-acid-test (NAT)+ donor offers to OHT was 39 days (interquartile range [IQR] 17-57). The median donor age was 34 years (IQR 31-37). Initial recipient HCV RNA levels ranged from 25 IU/mL to 40 million IU/mL, but all 10 patients had rapid decline in HCV NAT after elbasvir/grazoprevir treatment. Nine recipients achieved sustained virologic response at 12 weeks (SVR-12). The 10th recipient had a positive cross-match, experienced antibody-mediated rejection and multi-organ failure, and died on day 79. No serious adverse events occurred from HCV transmission or treatment. These short-term results suggest that HCV-negative candidates transplanted with HCV-infected hearts have acceptable outcomes