Safety, pharmacokinetics and pharmacodynamics of selgantolimod, an oral Toll-like receptor 8 agonist: a Phase Ia study in healthy subjects.

BACKGROUND: Selgantolimod is a novel oral, selective Toll-like receptor 8 (TLR8) agonist in development for the treatment of chronic hepatitis B (CHB). TLR8 is an endosomal innate immune receptor and a target for treatment of viral infections. This first-in-human study investigated the safety, tolerability, pharmacokinetics (PK) and pharmacodynamics (PD) of selgantolimod in healthy volunteers. METHODS: Of 71 subjects enrolled, 59 received a single dose of selgantolimod (0.5, 1.5, 3 or 5 mg) or placebo, and 12 were evaluated for food effect. Safety, PK and PD activity by induction of cytokines, chemokines and acute phase proteins were assessed. PK/PD analyses were conducted. RESULTS: Single doses of 0.5-5 mg were generally safe. No serious adverse events (AEs) or AEs leading to discontinuation were reported, and most were Grade 1 in severity. Selgantolimod displayed rapid absorption and dose-proportional PK and PD activity. Food had minimal effect on PK but resulted in diminished PD activity. In PK/PD analyses, near-saturation of induction for most evaluated biomarkers occurred at the 5-mg dose. CONCLUSIONS: Single doses of up to 5 mg selgantolimod were safe and induced dose-dependent PD responses. These data support evaluation of selgantolimod in combination with other agents in future clinical studies of CHB. Australian New Zealand Clinical Trials Registration: ACTRN12616001646437.

Combined GS-4774 and Tenofovir Therapy Can Improve HBV-Specific T-Cell Responses in Patients With Chronic Hepatitis.

BACKGROUND & AIMS: One strategy to treat chronic hepatitis B virus (HBV) infection could be to increase the functions of virus-specific T cells. We performed a multicenter phase 2 study to evaluate the safety and efficacy of GS-4774, a yeast-based therapeutic vaccine engineered to express HBV antigens, given with tenofovir disoproxil fumarate (TDF) to untreated patients with chronic HBV infection. METHODS: We performed an open-label study at 34 sites in Canada, Italy, New Zealand, Romania, South Korea, and United States from July 2014 to August 2016. Adults who were positive for HB surface antigen (HBsAg) > 6 months and levels of HBV DNA ≥2000 IU/mL who had not received antiviral treatment for HBV within 3 months of screening were randomly assigned (1:2:2:2) to groups given oral TDF 300 mg daily alone (n = 27; controls) or with 2, 10, or 40 yeast units GS-4774 (n = 168), administered subcutaneously every 4 weeks until week 20 for a total of 6 doses. Blood samples were collected and analyzed and patients received regular physical examinations. Efficacy was measured by decrease in HBsAg from baseline to week 24. Specific responses to HBV (production of interferon gamma [IFNG], tumor necrosis factor [TNF], interleukin 2 [IL2], and degranulation) were measured in T cells derived from 12 HBeAg-negative patients with genotype D infections, after overnight or 10 days of stimulation of peripheral blood mononuclear cells with peptides from the entire HBV proteome. T-regulatory cells were analyzed for frequency and phenotype. Data from studies of immune cells were compared with data on reductions in HBsAg, HBV DNA, and alanine aminotransferase in blood samples from patients. RESULTS: GS-4774 was safe and well tolerated but did not produce significant decreases in levels of HBsAg. Production of IFNG, TNF, and IL2 increased significantly at weeks 24 and 48, compared with baseline, in HBV-specific CD8+ T cells from patients given GS-4774 but not from controls. GS-4774 had greater effects on CD8+ than CD4+ T cells, which were not affected at all or very weakly by TDF with or without GS-4774. GS-4774 did not affect responses of T cells to other viruses tested. HBV core peptides induced the greatest production of IFNG by T cells following overnight stimulation, whereas HBV envelope antigens did not induce a response. Following 10 days of stimulation, production of IFNG and TNF increased with time of exposure to GS-4774; the greatest levels of responses were to HBV envelope antigens followed by core and polymerase peptides. We observed a correlation in patients given GS-4774 between increased T-cell functions and reductions in numbers of T-regulatory cells. CONCLUSIONS: In a phase 2 study of patients with chronic HBV infection given TDF with or without GS-4774, we found that vaccination can increase production of IFNG, TNF, and IL2 by CD8+ T cells exposed to antigenic peptides, with little effect on CD4+ T cells. Although GS-4774 did not reduce levels of HBsAg in patients, its strong immune stimulatory effect on CD8+ T cells might be used in combination with other antiviral agents to boost the antivirus immune response. Clinicaltrials.gov no: NCT02174276.

Evaluating for Human Herpesvirus 6 in the Liver Explants of Children With Liver Failure of Unknown Etiology.

BACKGROUND: Liver failure of unknown etiology (LFUE) has a transplant-free survival rate <25%. Human herpesvirus 6 (HHV-6) may be associated with LFUE, but studies are limited by small sample size. METHODS: We identified all children who underwent liver transplant for LFUE at a single quaternary children's hospital; 51/65 cases could be age matched with controls (children who underwent liver transplant for metabolic liver disease). Quantitative polymerase chain reaction for HHV-6 was performed on DNA from formalin-fixed paraffin-embedded liver explant tissue. RESULTS: HHV-6 was detected in 34/51 cases (66.7%) and 19/51 controls (37.3%) (P = .005). Average HHV-6 viral load was 213207 copies/106 cells in positive cases (range: 7293-1102030) and 38115 copies/106 cells in positive controls (range: 1382-122375) (P = .0008). HHV-6 was present significantly more often in cases compared to controls in patients younger than 6 years. In particular, in patients younger than 3 years, HHV-6 was present in 13/27 cases (48.1%) and 2/27 controls (7.4%) (P = .0009). CONCLUSIONS: HHV-6 was detected in liver explants significantly more often and in higher quantities in children transplanted for LFUE compared to controls, suggesting HHV-6 should be evaluated in young children who present with LFUE.

Improved Bone Safety of Tenofovir Alafenamide Compared to Tenofovir Disoproxil Fumarate Over 2 Years in Patients With Chronic HBV Infection.

BACKGROUND & AIMS: Long-term use of tenofovir disoproxil fumarate (TDF) reduces bone mineral density (BMD). Tenofovir alafenamide (TAF), a new prodrug of tenofovir, has shown non-inferior efficacy to TDF in patients with chronic hepatitis B virus (HBV) infection, with improved bone effects at 48 weeks. We performed a randomized trial to evaluate the bone safety of TAF compared with TDF over 2 years, assessing baseline risk factors for bone loss, were evaluated after 2 years of treatment. METHODS: In a double-blind study, hepatitis B e antigen (HBeAg)-positive patients (n = 873) and HBeAg-negative patients (n = 425) were randomly assigned (2:1) to groups given TAF (25 mg; n = 866) or TDF (300 mg; n = 432) once daily. We assessed bone safety, including hip and spine BMD, using dual-energy X-ray absorptiometry and measured changes in serum markers of bone turnover over 96 weeks. RESULTS: At baseline, treatment groups were well matched. At week 96, patients receiving TAF had significantly smaller decreases in hip BMD (mean reduction of 0.33%) than patients receiving TDF (mean reduction of 2.51%) (P < .001) and spine BMD (reduction of 0.75% in patients receiving patients receiving TAF vs reduction of 2.57% in patients receiving TDF) (P < .001). For hip BMD, the magnitude of difference in bone loss between the TAF and TDF groups increased at week 96 compared to week 48 (P < .001). The TAF group had minimal changes in markers of bone turnover by 12 weeks of treatment, but the TDF group had significant changes, compared to baseline. Risk factors for bone loss had fewer effects in patients receiving TAF than TDF at week 96. CONCLUSIONS: In double-blind randomized trials, we found that after 2 years of treatment, patients receiving TAF had continued improvements in bone safety compared with patients receiving TDF. Clinicaltrial.gov ID NCT01940471 and NCT01940341.

96 weeks treatment of tenofovir alafenamide vs. tenofovir disoproxil fumarate for hepatitis B virus infection.

BACKGROUND & AIMS: Tenofovir alafenamide (TAF) is a new prodrug of tenofovir developed to treat patients with chronic hepatitis B virus (HBV) infection at a lower dose than tenofovir disoproxil fumarate (TDF) through more efficient delivery of tenofovir to hepatocytes. In 48-week results from two ongoing, double-blind, randomized phase III trials, TAF was non-inferior to TDF in efficacy with improved renal and bone safety. We report 96-week outcomes for both trials. METHODS: In two international trials, patients with chronic HBV infection were randomized 2:1 to receive 25 mg TAF or 300 mg TDF in a double-blinded fashion. One study enrolled HBeAg-positive patients and the other HBeAg-negative patients. We assessed efficacy in each study, and safety in the pooled population. RESULTS: At week 96, the differences in the rates of viral suppression were similar in HBeAg-positive patients receiving TAF and TDF (73% vs. 75%, respectively, adjusted difference -2.2% (95% CI -8.3 to 3.9%; p = 0.47), and in HBeAg-negative patients receiving TAF and TDF (90% vs. 91%, respectively, adjusted difference -0.6% (95% CI -7.0 to 5.8%; p = 0.84). In both studies the proportions of patients with alanine aminotransferase above the upper limit of normal at baseline, who had normal alanine aminotransferase at week 96 of treatment, were significantly higher in patients receiving TAF than in those receiving TDF. In the pooled safety population, patients receiving TAF had significantly smaller decreases in bone mineral density than those receiving TDF in the hip (mean % change -0.33% vs. -2.51%; p <0.001) and lumbar spine (mean % change -0.75% vs. -2.57%; p <0.001), as well as a significantly smaller median change in estimated glomerular filtration rate by Cockcroft-Gault method (-1.2 vs. -4.8 mg/dl; p <0.001). CONCLUSION: In patients with HBV infection, TAF remained as effective as TDF, with continued improved renal and bone safety, two years after the initiation of treatment. Clinicaltrials.gov number: NCT01940471 and NCT01940341. LAY SUMMARY: At week 96 of two ongoing studies comparing the efficacy and safety of tenofovir alafenamide (TAF) to tenofovir disoproxil fumarate (TDF) for the treatment of chronic hepatitis B patients, TAF continues to be as effective as TDF with continued improved renal and bone safety. Registration: Clinicaltrials.gov number: NCT01940471 and NCT01940341.

Safety, efficacy and pharmacodynamics of vesatolimod (GS-9620) in virally suppressed patients with chronic hepatitis B.

BACKGROUND & AIMS: Vesatolimod (GS-9620) is an oral agonist of toll-like receptor 7, an activator of innate and adaptive immune responses. Herein the safety and efficacy of vesatolimod is assessed after once-weekly treatment in patients with chronic hepatitis B (CHB) infection suppressed on oral antiviral treatment. METHODS: In a phase II, double-blind, randomized, placebo (PBO)-controlled study, 162 patients stratified by hepatitis B surface antigen (HBsAg) levels and serum hepatitis B e antigen (HBeAg) status were randomized 1:3:3:3 to once-weekly oral PBO or vesatolimod (1-, 2-, or 4-mg doses) for 4, 8 or 12 weeks per cohort. Efficacy was assessed by change in baseline HBsAg (log10 IU/ml) at the primary endpoint (Week 24). Safety assessments included adverse events (AE) and laboratory abnormality monitoring. Pharmacodynamic assessments included peripheral cytokine level quantification and interferon-stimulated gene (ISG) mRNA expression evaluation. RESULTS: The majority of patients were male (76%) and HBeAg-negative (79%) at baseline. Most (41-80%) experienced ≥1 AE during the study with the majority of AEs mild or moderate in severity. No significant declines in HBsAg were observed at the primary (Week 24) or secondary endpoints (Weeks 4, 8, 12, and 48). ISG15 induction was dose-dependent and consistent after repeat dosing, returning closer to baseline by one week after treatment at all dose levels; no patient demonstrated significant serum interferon alpha (IFNα) expression at any timepoint evaluated. Multivariate analyses showed that ≥2-fold ISG15 induction is associated with 2- or 4-mg vesatolimod dose and female sex. CONCLUSIONS: Vesatolimod was safe and well-tolerated in patients with CHB, demonstrating consistent dose-dependent pharmacodynamic induction of ISG15 without significant systemic induction of IFNα expression or related symptoms. However, no significant HBsAg declines were observed. LAY SUMMARY: In a phase II study, vesatolimod, an oral, once-weekly, experimental immune-activating drug for the treatment of hepatitis B virus (HBV), is safe and well-tolerated in chronic HBV patients who are virally suppressed on oral antiviral treatment. Despite demonstrating on-target biomarker responses in patients, no significant declines in hepatitis B surface antigen were observed. Clinical Trial Number: GS-US-283-1059; NCT 02166047.

Absence of miR-182 Augments Cardiac Allograft Survival.

BACKGROUND: MicroRNAs (miRNAs) are small noncoding RNA molecules that regulate the posttranscriptional expression of target genes and are important regulators in immune responses. Previous studies demonstrated that the miRNA, miR-182 was significantly increased during allograft rejection. Further, the transcription factor Forkhead box (FOX) protein 1, (FOXO1) was shown to be a target of miR-182. The aim of this study is to further examine the role of miR-182 in alloimmune responses. METHODS: Transplantation of BALB/c cardiac allografts was performed in C57BL/6, miR-182, B6.129S-H2 (MHC II and CD4 T cell-deficient) and B6.129S2-Tap1 (MHC I and CD8 T cell-deficient) mice, with or without CTLA-4Ig administration. T cell phenotype, FOXO1 protein levels and graft infiltrating lymphocytes were determined in C57BL/6 or miR-182 mice by flow cytometric analysis, Western blot, and immunohistochemistry, respectively. RESULTS: We now show that T cells, mainly CD4 are the main cellular source of miR-182 during allograft rejection. In the absence of miR-182, CTLA-4Ig treatment significantly increased allograft survival (31.5 days C57BL/6 vs 60 days miR-182; P < 0.01). Further, CTLA4-Ig treatment inhibits miR-182 expression, increases FOXO1 levels, and reduces the percentage of CD4CD44 T cells after transplantation. Fewer T cells infiltrate the cardiac allografts, and memory T cells are significantly decreased in allograft recipients deficient in miR-182 with CTLA4-Ig treatment (P < 0.01). CONCLUSIONS: Our findings suggest that miR-182 contributes to the T-cell responses to alloantigen especially under costimulation blockade. Therapeutics that target specific miRNAs may prove beneficial in transplantation.

Mass cytometry reveals a distinct immunoprofile of operational tolerance in pediatric liver transplantation.

Long-term IS in transplant patients has significant morbidity, poorer quality of life, and substantial economic costs. TOL, defined as graft acceptance without functional impairment in the absence of IS, has been achieved in some pediatric LT recipients. Using mass cytometry, peripheral blood immunotyping was performed to characterize differences between tolerant patients and patients who are stable on single-agent IS. Single-cell mass cytometry was performed using blood samples from a single-center pediatric LT population of operationally tolerant patients to comprehensively characterize the immune cell populations in the tolerant state compared with patients on chronic low-dose IS. Specific T-cell populations of interest were confirmed by flow cytometry. This high-dimensional phenotypic analysis revealed distinct immunoprofiles between transplant populations as well as a CD4+ TOT (CD4+ CD5+ CD25+ CD38-/lo CD45RA) that correlates with tolerance in pediatric LT recipients. In TOL patients, the TOT was significantly increased as compared to patients stable on low levels of IS. This TOT cell was confirmed by flow cytometry and is distinct from classic Treg cells. These results demonstrate the power of mass cytometry to discover significant immune cell signatures that have diagnostic potential.

Liver microRNA Profile of Induced Allograft Tolerance.

BACKGROUND: Although the liver is less immunogenic than other solid organs, most liver transplant recipients receive lifelong immunosuppression. In both experimental models and clinical transplantation, total lymphoid irradiation (TLI) has been shown to induce allograft tolerance. Our goal was to identify the microRNAs (miRNAs) expressed in tolerant liver allograft recipients in an experimental model of TLI-induced tolerance. METHODS: To identify the miRNAs associated with TLI-induced tolerance, we examined syngeneic recipients (Lewis→Lewis) and allogeneic recipients (Dark Agouti→Lewis) of orthotropic liver transplants that received posttransplant TLI, allogeneic recipients that were not treated posttransplantation and experienced acute rejection, and native Dark Agouti livers. Quantitative-polymerase chain reaction miRNA array cards were used to profile liver grafts. RESULTS: We identified 12 miRNAs that were specifically and significantly increased during acute rejection. In early tolerance, 33 miRNAs were altered compared with syngeneic livers, with 80% of the miRNAs increased. In established tolerance, 42 miRNAs were altered. In addition, miR-142-5p and miR-181a demonstrated increased expression in tolerant livers (both early and established tolerance) as compared with syngeneic livers. A principal component analysis of all miRNAs assayed demonstrated a profile in established tolerance that was closely related to that seen in syngeneic livers. CONCLUSIONS: The miRNA profile of established tolerant allografts is very similar to syngeneic grafts, suggesting tolerance may be a return to an immunological state of quiescence.

Chronic high Epstein-Barr viral load carriage in pediatric small bowel transplant recipients.

The development of EBV infection and PTLD is normally associated with a high EBV load in peripheral blood. Often, children undergoing primary or reactivation of EBV infection subsequent to ITx will have chronically elevated EBV loads. To better understand this phenomenon and its consequences, we retrospectively reviewed the records of children who underwent ITx (either isolated or part of multivisceral transplantation) at our center from 1992 to 2007, to identify chronic high EBV load carriers in this population. CHL state was defined as the presence of high load for >50% of samples for greater than or equal to six months following either asymptomatic infection or complete clinical resolution of EBV disease/PTLD. Thirty-five CHL carriers were identified from our patient population. Pretransplant serologies were available on 34 of these patients: 17 were EBV negative and 17 seropositive; one had unknown EBV serostatus prior to transplant. Seven of the 17 seronegative patients developed their CHL carrier state at the time of their primary EBV infection. Thirteen of the 35 (37%) HLC patients developed EBV disease after meeting the definition of high-load carrier states. EBV-related diseases developing in CHL carriers included EBV adenitis (n=1), EBV enteritis (n=7), PTLD (n=4), and EBV+ spindle cell tumor (n=1). Disease was seen in 7/17 of the seronegative (one PTLD) and 6/17 of the seropositive patients (three PTLD). Thirteen of 35 patients (37%) resolved their CHL state without apparent sequelae while nine remain asymptomatic CHL carriers. Three children have had more than one episode of CHL. These data provide important information about the outcome of chronic EBV high-load carriage in pediatric intestinal transplant recipients.

Antigen-presenting cells under the influence of alcohol.

The negative influence of alcohol (ethanol) and its metabolites on innate and adaptive immunity is well-recognized. Much attention has recently been focused on the impact of acute and chronic alcohol exposure on antigen-presenting cells (APC). In particular, insights have been gained into how the properties of human blood monocytes and rodent macrophages are influenced by alcohol in vitro and in vivo. Here, we review the impact of alcohol on various aspects of APC function and the underlying mechanisms, including its effects on intracellular signaling events. We also discuss new information regarding the influence of alcohol on various APC populations in the liver, a primary site of alcohol metabolism.

Chronic ethanol exposure affects in vivo migration of hepatic dendritic cells to secondary lymphoid tissue.

The mechanisms by which chronic ethanol (EtOH) consumption results in an immune-compromised state have not been fully elucidated. No studies to date have ascertained whether EtOH affects the migratory capacity of dendritic cells (DC), potent immune regulators. We hypothesized that EtOH exposure might affect hepatic and splenic DC trafficking to secondary lymphoid tissues and the resulting immune response. Hepatic DC from EtOH-treated animals migrated in greater numbers to draining lymphoid tissue than controls, whereas spleen DC were unaffected. Moreover, hepatic EtOH-exposed (E) DC induced more vigorous priming of allogeneic T cells in vivo compared with splenic EDC or controls. Altered hepatic EDC migration was independent of either CCR7 or CD11a expression, with no striking changes in surface expression of other adhesion molecules analyzed. The modified trafficking to secondary lymphoid tissue observed for hepatic EDC may play a role in the altered immune response to microbial pathogens in chronic alcohol users.

Ethanol affects the generation, cosignaling molecule expression, and function of plasmacytoid and myeloid dendritic cell subsets in vitro and in vivo.

The influence of ethanol (EtOH) on multiple dendritic cell (DC) subsets, in the steady state or following their mobilization in vivo, has not been characterized. Herein, generation of mouse bone marrow-derived DC (BMDC) in response to fms-like tyrosine kinase 3 ligand was inhibited by physiologically relevant concentrations of EtOH with selective suppression of plasmacytoid (p)DC. EtOH reduced surface expression of costimulatory molecules (CD40, CD80, CD86) but not that of coinhibitory CD274 (B7-H1) on resting or CpG-stimulated DC subsets. Interleukin (IL)-12p70 production by activated DC was impaired. Consistent with these findings, EtOH-exposed BMDC exhibited a reduced capacity to induce naïve, allogeneic T cell proliferation and impaired ability to prime T cells in vivo. DC subsets freshly isolated from EtOH-fed mice were also examined. Liver DC, inherently immature and resistant to maturation, exhibited little change in their low surface cosignaling molecule expression, whereas splenic DC showed reduced expression of surface costimulatory molecules in response to CpG stimulation in vivo. These splenic DC elicited reduced naïve, allogeneic T cell proliferation in vitro, and the stimulatory capacity of resting but not CpG-activated liver DC was reduced by chronic EtOH administration. T cells from animals primed with EtOH-exposed DC produced elevated levels of IL-10 following ex vivo challenge with donor alloantigen. Thus, EtOH impairs cytokine-driven differentiation and function of myeloid DC and pDC in vitro. Hepatic DC from chronic EtOH-fed mice are less affected than splenic DC, which exhibit impaired functional maturation following CpG stimulation. These results indicate a potential mechanism by which alcohol consumption is associated with immunosuppression.

Low TLR4 expression by liver dendritic cells correlates with reduced capacity to activate allogeneic T cells in response to endotoxin.

Signaling via TLRs results in dendritic cell (DC) activation/maturation and plays a critical role in the outcome of primary immune responses. So far, no data exist concerning TLR expression by liver DC, generally regarded as less immunostimulatory than secondary lymphoid tissue DC. Because the liver lies directly downstream from the gut, it is constantly exposed to bacterial LPS, a TLR4 ligand. We examined TLR4 expression by freshly isolated, flow-sorted C57BL/10 mouse liver DC compared with spleen DC. Real-time PCR revealed that liver CD11c+CD8alpha- (myeloid) and CD11c+CD8alpha+ ("lymphoid-related") DC expressed lower TLR4 mRNA compared with their splenic counterparts. Lower TLR4 expression correlated with reduced capacity of LPS (10 ng/ml) but not anti-CD40-stimulated liver DC to induce naive allogeneic (C3H/HeJ) T cell proliferation. By contrast to LPS-stimulated splenic DC, these LPS-activated hepatic DC induced alloantigen-specific T cell hyporesponsiveness in vitro, correlated with deficient Th1 (IFN-gamma) and Th2 (IL-4) responses. When higher LPS concentrations (> or =100 ng/ml) were tested, the capacity of liver DC to induce proliferation of T cells and Th1-type responses was enhanced, but remained inferior to that of splenic DC. Hepatic DC activated by LPS in vivo were inferior allogeneic T cell stimulators compared with splenic DC, whereas adoptive transfer of LPS-stimulated (10 ng/ml) liver DC induced skewing toward Th2 responses. These data suggest that comparatively low expression of TLR4 by liver DC may limit their response to specific ligands, resulting in reduced or altered activation of hepatic adaptive immune responses.

Disparate ability of murine CD8alpha- and CD8alpha+ dendritic cell subsets to traverse endothelium is not determined by differential CD11b expression.

Upon Ag uptake and response to maturation stimuli, dendritic cells (DC) are directed through lymphatic or blood vessel endothelium to T cell areas of secondary lymphoid tissues by the constitutively expressed CC chemokines CCL19 and CCL21. We have shown that mature (m) murine CD8alpha+ DC exhibit poorer migratory ability to these chemokines than classic CD8alpha- DC by quantifying their in vitro chemotaxis through unmodified Transwell filters. We hypothesized that lower surface expression (compared to CD8alpha- mDC) of the adhesion molecule CD11b on CD8alpha+ DC might limit their ability to adhere to filter pores in vitro and/or endothelium in vitro/in vivo. To test the role of this and/or other adhesion molecules (CD11a, CD31, CD54 and CD62L) in regulating murine DC subset migration, we used specific mAbs to block their function and quantified their migration through resting or tumour necrosis factor (TNF)-alpha-activated endothelial cell (EC) layered-Transwell filters. Both CD8alpha+ and CD8alpha- subsets migrated through resting EC (albeit less than in the absence of EC) in response to CCL19 and CCL21, and migration through TNF-alpha-activated EC was enhanced. In contrast to reports concerning human DC, transendothelial migration of the murine DC subsets was not dependent on CD11b, CD31, or CD62L expression by these cells. CD54 and CD11a, however, were at least partly involved in DC/EC interactions. This is the first report to examine adhesion molecules involved in transendothelial migration of murine DC subsets.

Comparative evaluation of CC chemokine-induced migration of murine CD8alpha+ and CD8alpha- dendritic cells and their in vivo trafficking.

Murine CD11c(+)CD8alpha(-) and CD11c(+)CD8alpha(+) dendritic cells (DCs) differentially regulate T cell responses. Although specific chemokines that recruit immature (i) or mature (m) CD8alpha(-) DCs have been identified, little is known about the influence of chemokines on CD8alpha(+) DCs. iDCs and mDCs isolated from spleens of fms-like tyrosine kinase 3 ligand-treated B10 mice were compared directly for migratory responses to a panel of CC chemokines or following local or systemic administration. In vitro assays were performed using Transwell(R) chambers. iDCs did not respond to any CC chemokines tested. Both subsets of mDCs migrated to CCL19 and CCL21, with consistently lower percentages of CD8alpha(+) DCs migrating. Chemokine receptor mRNA and protein expression were analyzed, but no correlation between expression and function was demonstrated. In vivo trafficking of fluorochrome-labeled DCs (B10; H2(b)) was assessed by immunohistochemistry and by rare-event flow cytometric analysis of allogeneic recipient (BALB/c; H2(d)) draining lymph node (DLN) and spleen cells. Twenty-four hours after intravenous injection, chloromethylfluorescein diacetate-positive CD8alpha(+) and CD8alpha(-) mDCs were detected by immunohistochemistry in spleens in similar numbers (that decreased over time). Following subcutaneous injection, both DC subsets were detected in DLN at 24 h, but only CD8alpha(-) DCs were evident by flow analysis at 48 h. Although CD8alpha(+) DCs migrate from peripheral tissues to T cell areas of (allogeneic) secondary lymphoid organs, they appear to mobilize as mDCs and less efficiently than CD8alpha(-) mDCs.