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Background: Many health issues prevalent in African American (AA) populations are associated with chronic inflammation and related health conditions, including autoimmune diseases, infectious diseases, neurologic disorders, metabolic syndromes, and others. The current study aims to understand plasma microbiome translocation as a potential trigger for chronic inflammation. Methods: In this study, 16 Caucasian American (CA) and 22 African American (AA) healthy individuals were recruited. Microbial DNA was isolated from the plasma samples and sequenced via microbial 16S rRNA V3-4 sequencing. The plasma levels of 33 cytokines and chemokines were evaluated. The proinflammatory microbiomes were verified using human THP-1 cells in vitro. Results: The plasma levels of IL-6, IL-15, MIP-1α, MIP-1β, and MIP-3α were higher in the AA people, whereas IL-1α and IL-27 were elevated in the CA people. The plasma microbiomes exhibited eight bacterial genera/phyla differentially enriched in the CA and AA people. Given the critical role of IL-6 in chronic inflammation and associated diseases, we identified five bacteria genera significantly associated with IL-6. The abundance of Actinomyces was positively correlated with the plasma IL-6 level (r = 0.41, p = 0.01), while the abundance of Kurthia (r = −0.34, p = 0.04), Noviherbaspirillum (r = −0.34, p = 0.04), Candidatus Protochlamydia (r = −0.36, p = 0.03), and Reyranella (r = −0.39, p = 0.02) was negatively correlated with this. Finally, the THP-1 cells treated with heat-killed bacteria produced higher levels of IL-6 in vitro in response to the Actinomyces species compared to the species in the genus either uncorrelated or negatively correlated with IL-6. Conclusions: This is the first study to report potential blood microbiome translocation as a driver for persistently elevated IL-6 levels in the periphery in healthy AA versus CA people. Understanding the plasma microbiome linked to the IL-6 levels in people with different racial backgrounds is essential to unraveling the therapeutic approaches to improve precision medicine. [ABSTRACT FROM AUTHOR]

Objective: Black groups have increased prevalence and accelerated pathogenicity of systemic lupus erythematosus (SLE) compared to other ethnic/racial groups. The microbiome and systemic microbial translocation are considered contributing factors to SLE disease pathogenesis. However, racial differences in the plasma microbiome and microbial translocation in lupus remain unknown. Methods: In the current study, we investigated plasma levels of microbial translocation (lipopolysaccharide [LPS] and zonulin) and the plasma microbiome using microbial 16S RNA sequencing of Black and White patients with SLE and Black and White healthy controls. Results: Plasma microbial translocation was increased in Black patients versus in White patients and in patients with SLE versus healthy controls regardless of race. Compared to sex, age, and disease status, race had the strongest association with plasma microbiome differences. Black groups (Black controls and Black patients) had lower α‐diversity than White groups (White controls and White patients) and more distinct β‐diversity. Black and White patients demonstrated differences in plasma bacterial presence, including Staphylococcus and Burkholderia. Compared to White patients, Black patients had higher SLE Disease Activity Index (SLEDAI) scores and urinary protein levels as well as a trend for increased anti–double‐stranded DNA (dsDNA) antibody levels consistent with the known increased severity of lupus in Black patients overall. Certain plasma bacteria at the genus level were identified that were associated with the SLEDAI score, urinary protein, and anti‐dsDNA antibody levels. Conclusion: This study reveals racial differences in both quality and quantity of plasma microbial translocation and identified specific plasma microbiome differences associated with SLE disease pathogenesis. Thus, this study may provide new insights into future potential microbiome therapies on SLE pathogenesis. [ABSTRACT FROM AUTHOR]

Blood microbiome is important to investigate microbial-host interactions and the effects on systemic immune perturbations. However, this effort has met with major challenges due to low microbial biomass and background artifacts. In the current study, microbial 16S DNA sequencing was applied to analyze plasma microbiome. We have developed a quality-filtering strategy to evaluate and exclude low levels of microbial sequences, potential contaminations, and artifacts from plasma microbial 16S DNA sequencing analyses. Furthermore, we have applied our technique in three cohorts, including tobacco-smokers, HIV-infected individuals, and individuals with systemic lupus erythematosus (SLE), as well as corresponding controls. More than 97% of total sequence data was removed using stringent quality-filtering strategy analyses; those removed amplicon sequence variants (ASVs) were low levels of microbial sequences, contaminations, and artifacts. The specifically enriched pathobiont bacterial ASVs have been identified in plasmas from tobacco-smokers, HIV-infected individuals, and individuals with SLE but not from control subjects. The associations between these ASVs and disease pathogenesis were demonstrated. The pathologic activities of some identified bacteria were further verified in vitro. We present a quality-filtering strategy to identify pathogenesis-associated plasma microbiome. Our approach provides a method for studying the diagnosis of subclinical microbial infection as well as for understanding the roles of microbiome-host interaction in disease pathogenesis. [ABSTRACT FROM AUTHOR]

Objective: Systemic lupus erythematosus (SLE) is characterized by the production of antibodies against self antigens. However, the events underlying autoantibody formation in SLE remain unclear. This study was undertaken to investigate the role of plasma autoantibody levels, microbial translocation, and the microbiome in SLE. Methods: Plasma samples from 2 cohorts, one with 18 unrelated healthy controls and 18 first‐degree relatives and the other with 19 healthy controls and 21 SLE patients, were assessed for autoantibody levels by autoantigen microarray analysis, measurement of lipopolysaccharide (LPS) levels by Limulus amebocyte assay, and determination of microbiome composition by microbial 16S ribosomal DNA sequencing. Results: First‐degree relatives and SLE patients exhibited increased plasma autoantibody levels compared to their control groups. Parents and children of lupus patients exhibited elevated plasma LPS levels compared to controls (P = 0.02). Plasma LPS levels positively correlated with plasma anti–double‐stranded DNA IgG levels in first‐degree relatives (r = 0.51, P = 0.03), but not in SLE patients. Circulating microbiome analysis revealed that first‐degree relatives had significantly reduced microbiome diversity compared to their controls (observed species, P = 0.004; Chao1 index, P = 0.005), but this reduction was not observed in SLE patients. The majority of bacteria that were differentially abundant between unrelated healthy controls and first‐degree relatives were in the Firmicutes phylum, while differences in bacteria from several phyla were identified between healthy controls and SLE patients. Bacteria in the Paenibacillus genus were the only overlapping differentially abundant bacteria in both cohorts, and were reduced in first‐degree relatives (adjusted P [Padj] = 2.13 × 10−12) and SLE patients (Padj = 0.008) but elevated in controls. Conclusions: These results indicate a possible role of plasma microbial translocation and microbiome composition in influencing autoantibody development in SLE. [ABSTRACT FROM AUTHOR]

Autoantibodies binding on CD4+ T cells may mediate CD4+ T cell death, and prevent CD4+ T cell recovery in aviremic HIV‐infected patients under ART. Although effective antiretroviral therapy (ART) suppresses HIV viral replication, prevents AIDS‐related complications, and prolongs life, a proportion of patients fails to restore the patients' CD4+ T cell number to the level of healthy individuals. Increased mortality and morbidity have been observed in these patients. In the current study, we have investigated the role of auto‐IgGs in CD4+ T cell apoptosis and recovery in a cross‐sectional study. All HIV+ subjects were on viral‐suppressive ART treatment with a different degree of CD4+ T cell reconstitution. Total auto‐IgG binding on CD4+ T cell surfaces and its associated apoptosis and CD4+ T cell recovery were analyzed by flow cytometry ex vivo. Total IgGs from plasma were tested for their binding capacities to CD4+ T cell surfaces and their mediation to CD4+ T cell death through NK cell cytotoxicity in vitro. HIV+ subjects had increased surface binding of auto‐IgGs on CD4+ T cells compared with healthy controls, and IgG binding was associated with elevated CD4+ T cell apoptosis in HIV+ subjects but not in healthy controls. Plasma IgGs from HIV+ subjects bound to CD4+ T cells and induced cell apoptosis through NK cytotoxicity in vitro. Soluble CD4 (sCD4) preincubation prevented NK cell‐mediated CD4+ T cell death. Our results suggest that plasma autoantibodies may play a role in some HIV+ patients with poor CD4+ T cell recovery under viral‐suppressive ART. [ABSTRACT FROM AUTHOR]

The authors present a reply to comments on their article on reduced diversity in the circulating microbiome of first-degree relatives. Topics discussed include the absence of diversity between African American control and patients with systemic lupus erythematosus (SLE) groups, and the possible role of race in differences in circulating microbiome diversity. The authors agree that diet, smoking status, and body mass index could account for diversity differences between the two groups.

Plasma level of microbial translocation is a marker of mucosal permeability. Increased mucosal permeability ignites elevated microbial translocation and as a consequence of systemic inflammation. Pregnant women with depression have higher levels of inflammatory markers relative to pregnant women without depression, however, no studies have reported whether systemic microbial translocation will change in depressed women during pregnancy. In this study, we examined the plasma LPS level of depressed women during pregnancy. The results showed that the plasma LPS level was significantly increased in depressed mothers during their 8–12 weeks gestation compared to healthy controls. Compared to 8–12 weeks gestation, the plasma LPS levels were significantly decreased at 24–28 weeks gestation and 6–8 weeks postpartum in both depressed subjects and healthy controls. Furthermore, the plasma levels of pro-inflammatory cytokines (TNF-α and MCP/CCL2) associated with microbial translocation were significantly increased in depressed subjects during 8–12 weeks gestation compared to healthy controls. These results indicate that the level of microbial translocation is increased in depressed women during early pregnancy. [ABSTRACT FROM AUTHOR]

There is an intricate interplay between the microbiome and the immune response impacting development of normal immunity and autoimmunity. However, we do not fully understand how the microbiome affects production of natural-like and pathogenic autoantibodies. Peptidoglycan (PGN) is a component of the bacterial cell wall which is highly antigenic. PGNs from different bacteria can differ in their immune regulatory activities. C57BL/6 and MRL/lpr mice were intraperitoneally injected with saline or PGN from Staphylococcus aureus or Bacillus subtilis. Spleen anti-double-stranded DNA (dsDNA) IgG + B cells were sorted for B-cell receptor sequencing. Serum autoantibody levels and kidney damage were analyzed. Further, the association between plasma S. aureus translocation and systemic lupus erythematosus (SLE) pathogenesis was assessed in women. Administration of B. subtilis PGN induced natural-like anti-dsDNA autoantibodies (e.g., IgM, short lived IgG response, and no tissue damage), whereas S. aureus PGN induced pathogenic anti-dsDNA autoantibodies (e.g., prolonged IgG production, low IgM, autoantibody-mediated kidney damage) in C57BL/6 and/or MRL/lpr mice. However, serum total IgG did not differ. S. aureus PGN induced antibodies with reduced clonality and greater hypermutation of IGHV3-74 in splenic anti-dsDNA IgG + B cells from C57BL/6 mice. Further, S. aureus PGN promoted IgG class switch recombination via toll-like receptor 2. Plasma S. aureus DNA levels were increased in women with SLE versus control women and correlated with levels of lupus-related autoantibodies and renal involvement. S. aureus PGN induces pathogenic autoantibody production, whereas B. subtilis PGN drives production of natural nonpathogenic autoantibodies. • PGNs from S. aureus and Bacillus subtilis contribute to the production of pathogenic or nonpathogenic autoantibodies respectively. • S. aureus PGN induces class switch recombination via TLR2; S. aureus PGN induces autoantibodies IgG anti-dsDNA with reduced clonality and greater hypermutation of IGHV3-74 in splenic anti-dsDNA IgG + B cells from C57BL/6 mice. • Plasma S. aureus DNA levels were increased in women with SLE versus control women and correlated with levels of lupus-related autoantibodies and renal involvement. [ABSTRACT FROM AUTHOR]