Long-term tolerance to skin commensals is established neonatally through a specialized dendritic cell subgroup

Early-life establishment of tolerance to commensal bacteria at barrier surfaces carries enduring implications for immune health but remains poorly understood. Here, we showed that tolerance in skin was controlled by microbial interaction with a specialized subset of antigen-presenting cells. More particularly, CD301b+ type 2 conventional dendritic cells (DCs) in neonatal skin were specifically capable of uptake and presentation of commensal antigens for the generation of regulatory T (Treg) cells. CD301b+ DC2 were enriched for phagocytosis and maturation programs, while also expressing tolerogenic markers. In both human and murine skin, these signatures were reinforced by microbial uptake. In contrast to their adult counterparts or other early-life DC subsets, neonatal CD301b+ DC2 highly expressed the retinoic-acid-producing enzyme, RALDH2, the deletion of which limited commensal-specific Treg cell generation. Thus, synergistic interactions between bacteria and a specialized DC subset critically support early-life tolerance at the cutaneous interface.

Changes in Immune-Related Biomarkers and Endocannabinoids as a Function of Frequency of Cannabis Use in People Living With and Without HIV

Background: Cannabis use is common among people living with HIV (PLWH). Some observational studies of PLWH have linked cannabis use to lower immune markers; however, this is yet to be confirmed. In addition, whether HIV affects the endogenous cannabinoid system has not been studied. Our objective was to examine changes in immune-related biomarkers and endocannabinoids as a function of cannabis use frequency in people living with and without HIV. Materials and Methods: Data were obtained from a longitudinal study of men who have sex with men living in Los Angeles with, or at risk for, HIV. By design, half were PLWH. Those eligible for the parent study were willing and able to return for follow-up every 6 months. Those eligible for inclusion in this study reported varying levels of current cannabis use at follow-up. Specifically, one visit corresponded to a period of daily use and another to a period of infrequent use (weekly, monthly, or less than monthly). Banked serum from all eligible participants was analyzed for immune-related biomarkers, endocannabinoids, and paracannabinoids. Results: The analysis included 36 men, 19 of whom were PLWH. PLWH reported greater lifetime methamphetamine or amphetamine use (68% vs. 0%) and current cigarette use (55% vs. 20%) than people without HIV. Serum levels of HIV-related immune biomarkers including tumor necrosis factor receptor 2 (TNFR2; p=0.013) and CD27 (p=0.004) were greater in PLWH, alongside lower anandamide (AEA) (F1,34=5.337, p=0.027) and oleoylethanolamide (OEA) (F1,34=8.222, p=0.007) levels relative to people without HIV. Frequency of cannabis use did not impact the serum analytes in our study. Conclusions: Higher levels of TNFR2 and CD27 and lower levels of AEA and OEA in PLWH underscore the role of the TNF/TNFR superfamily in HIV, while highlighting a new role for the enzymatic activity of fatty acid amide hydrolase (the enzyme that hydrolyzes AEA and OEA) in HIV. Findings that cannabis frequency did not impact the immune phenotype may not generalize to other populations of PLWH. Additional work is required to further clarify the relationship between immune markers and endocannabinoids as a function of cannabis use frequency in PLWH. ClinicalTrials.gov ID: NCT01201083.

Brief Report: Impact of Methamphetamine Use and Rectal STIs on Systemic and Rectal Mucosal Inflammation

BACKGROUND

Methamphetamine (MA) use is associated with sexual risk behavior as well as systemic and mucosal inflammation, suggesting parallel biological and behavioral mechanisms of HIV transmission among men who have sex with men (MSM) who use MA. Data evaluating the combined biological effects of MA use with concomitant rectal gonococcal and/or chlamydial (GC/CT) infection on inflammation are limited.

SETTING

Secondary analysis of stored rectal and plasma specimens from 100 MSM participating in an NIDA-funded longitudinal cohort in Los Angeles, CA.

METHODS

This cross-sectional analysis evaluated systemic and rectal inflammatory markers under 2 conditions: (1) recent MA use (by urine drug screen) and (2) rectal GC/CT infection. We evaluated 50 participants with recent MA use (25 with and 25 without rectal GC/CT) and 50 MSM without MA use (25 with and 25 without rectal GC/CT). Log-transformed plasma and rectal immune markers were regressed on MA exposure and rectal GC/CT, controlling for HIV status and age.

RESULTS

Median age was 32 (range 19-45) years, and 58% of participants were living with HIV. Plasma tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-8, IL-1ß, and rectal IL-6 were associated with rectal GC/CT and MA use, independent of HIV status. Higher levels of rectal TNF-α, IL-1ß, and IL-17a were associated with rectal GC/CT.

CONCLUSIONS

Systemic and rectal inflammation was positively associated with rectal GC/CT and MA use. Condomless sex in the setting of GC/CT- and MA-induced immune activation may provide a basis for synergistic biobehavioral mechanisms that promote HIV/STI transmission among MSM who use MA.