Plasma levels of bacterial DNA correlate with immune activation and the magnitude of immune restoration in persons with antiretroviral-treated HIV infection

Abstract

The significance of elevated plasma levels of bacterial lipopolysaccharide (LPS) in persons with chronic HIV infection remains undefined. We measured LPS levels by use of limulus lysate assay, and DNA sequences encoding bacterial ribosomal 16S RNA (16S rDNA) were assessed by quantitative polymerase chain reactions in plasma samples obtained from 242 donors. Plasma levels of 16S rDNA were significantly higher in human immunodeficiency virus (HIV)-infected subjects than in uninfected subjects, and they correlated with LPS levels. Higher levels of 16S rDNA were associated with higher levels of T cell activation and with lower levels of CD4 T cell restoration during antiretroviral therapy. Antiretroviral therapy reduces but does not fully normalize plasma levels of bacterial 16S rDNA, an index of microbial translocation from the gastrointestinal tract. High levels of 16S rDNA during therapy are strongly associated with reduced increases in the CD4(+) T lymphocyte count, irrespective of plasma HIV RNA levels. These findings are consistent with the importance of microbial translocation in immunodeficiency and T cell homeostasis in chronic HIV infection.

Figure 1

Elevation of bacterial 16S ribosomal DNA (rDNA) levels in the plasma of HIV-infected subjects in the Case Western Reserve University study (cross-sectional study 1). Bacterial 16S rDNA levels were measured by quantitative polymerase chain reaction. P values were calculated using the Mann-Whitney U and Kruskal-Wallis H tests. HAART, highly active antiretroviral therapy; HIV⁻, HIV negative; VL, viral load.

Figure 2

Correlation of plasma levels of bacterial 16S ribosomal DNA (rDNA) with HIV RNA levels (A) but not with circulating CD4⁺ T cell counts (B). P values were calculated using Spearman's correlation test. Data were derived from the Case Western Reserve University cohort (cross-sectional study 1). HAART, highly active antiretroviral therapy; VL, viral load.

Figure 3

Correlation of plasma levels of bacterial 16S ribosomal DNA (rDNA) with plasma levels of lipopolysaccharide (LPS) among antiretroviral therapy–treated patients with low or undetectable HIV viremia. P values were calculated using Spearman's correlation test. All patients were followed in the University of California, San Francisco Study on the Consequences of the Protease Inhibitor Era (SCOPE) cohort study (cross-sectional study 2).

Figure 4

Correlation of plasma levels of bacterial 16S ribosomal DNA (rDNA) with indices of CD8 T cell activation and cellular restoration. A, Plasma 16S rDNA levels correlate directly with the frequency of CD38 and HLA-DR expression on CD8⁺ T cells. B, Plasma 16S rDNA levels correlate inversely with the magnitude of CD4⁺ T lymphocyte restoration after antiretroviral therapy (ART). C, Increases in CD4⁺ T lymphocyte counts after ART correlate inversely with the proportions of CD8⁺ T cells expressing CD38 and HLA-DR. P values were calculated using Spearman's correlation test. All patients were followed in the University of California, San Francisco Study on the Consequences of the Protease Inhibitor Era (SCOPE) cohort study (cross-sectional study 2).

Figure 5

Effects of antiretroviral therapy on plasma levels of bacterial 16S ribosomal DNA (rDNA), HIV RNA levels, immune activation, and CD4 T cell counts. A, Progressive decrease in plasma levels of bacterial 16S rDNA after administration of effective combination antiretroviral therapy (ART). B, Decreased expression of CD38 and HLA DR on CD8⁺ T cells in association with receipt of combination ART. C, Plasma levels of HIV RNA decrease with combination ART. D, CD4 T cell counts increase with combination ART. Comparisons are made to baseline values after 1, 8, and 48 weeks of ART. Data shown are median values and 95% confidence intervals. P values were calculated using the Wilcoxon signed rank test (n = 20) (AIDS Clinical Trials Group 5014 longitudinal study). HAART, highly active antiretroviral therapy.

Figure 6

Correlation of pretreatment plasma levels of bacterial 16S ribosomal DNA (rDNA) with indices of immune activation, and inverse correlation, after 48 weeks of therapy, with the magnitude of immune restoration. A, In treatment-naive subjects, correlation of plasma levels of bacterial 16S rDNA with frequencies of CD38⁺HLA-DR⁺CD8⁺ T cells (n = 54). B, At the end of 48 weeks of antiretroviral therapy, inverse correlation of plasma levels of bacterial 16S rDNA with the magnitude of increases in CD4 T cell counts (n = 20). P values were calculated using Spearman's correlation test (AIDS Clinical Trials Group 5014 longitudinal study) (Note: baseline samples were available for 54 subjects; only 20 subjects had samples available for analysis at baseline and at weeks 1, 8, and 48).