In our previous study, at baseline, there was no significant difference between host gene expression of HAART eligible and ineligible HIV+TB+ groups 11. However, the prevalence of mortality among HAART ineligible groups was higher than eligible groups 17. Assessing immunological profiles contributors’ for mortality from HIV-TB co-infection is essential to prediction of mortality, to facilitate the development of effective assays, the discovery of novel therapeutic targets and enable appropriate risk stratification to target new interventions appropriately, and aid monitoring of treatment responses. Here, we used a focused gene expression profiling platform, dcRT-MLPA 15, targeting innate and adaptive immune response genes, to analyze RNA expression levels of 105 pre-selected genes in peripheral blood of TB-HIV-co-infected individuals and identified biomarkers with excellent predictor capacity between 9 death groups and 18 survivor matched controls. The expression levels of 8 single genes (CCL5, PTPRCv1, CD3E, IL7R, NOD1, IL-4δ2 and GNLY) could accurately predict which active TB with HIV coinfected patients will be death with AUCs ≥75, indicating these interrelating biomarkers are strongly associated with TB-HIV-coinfected related mortality.
The lower expression of T-cell associated genes (PTPRCv1, CD3E and IL7R) in these death groups may reflect reduce responsiveness of TCR signaling which may represent an HIV-induced evasion mechanism in individuals with weak immune system 18-20. Given the fact that HIV infection accelerates decreasing of the expression of all investigated T cell subsets which leads to HIV progression. However, our result shows lower expression of PTPRCv1 cells was associated with an increased risk of dying which is similar with previous report 21. This lower expression may related to depletion of naive T cells 22,23, and a relative expansion of immature and activated CD4+ cells 24,25. Lower gene expression of CD3E in death groups suggests lack of preTCR-associated intrinsic kinase activity which may play critical role in transmitting signal across T cell membrane 26. Previous study demonstrated that low CD3E expression was a predictor of poor survival 27. This may correlated with the infiltration levels of CD8+ T cells to the infection cite that leads deletion of T-cells and with the increase of pathological stage 28. Lower expression of IL7R were also reported in AIDS patients elsewhere previously 29. These findings shows impaired T-cell functions and immune failure described in TB/HIV patients that can predict the mortality. The function of IL-7R has improved the functionality of tolerized CD8 T cells their ignorance to self-antigens and promote CD8 T cell cytotoxicity to self-antigens which protects autoimmune 30.
Our finding shows, the gene expression of CCL5 (Myeloid associated gene) was amongst the strongest differentially expressed genes between death groups and survived matched controls, with potential discriminatory power between death groups and survived matched controls. This is consistent with the expression profiles of soluble CCL5/RANTES from plasma 31. T cells preferentially used CCR5 interactions with ligands (CCL5 and CCL4) for early migration into Mtb-infected lungs and granuloma formation 32, which indicates CCL5 contributes to early, protective, Mtb-specific immunity 33, but may also important role in immunopathogenesis during TB 34.
The survived matched control had increased host gene expression over the follow up time (Figure 5), which is similar with our previously finding ‘most gene expression were normalized at the end of anti-TB treatment of TB patients to levels observed in latent TB infected and uninfected control subjects during HIV infection” 11. This finding shows clearing of the TB bacilli from the infection body and restore gene expression due to anti-TB treatment. However, anti-TB treatment may be less likely to clear of the TB bacilli and restore gene expression in these death group. Moreover, HAART have not any impact on the level of gene expression during HIV infection. Therefore, other therapeutic that can restore these gene (PTPRCv1, CD3E, IL7R and CCL5) might be needed to save lives.
Our finding also shows low gene expressions of NOD1 and NLRP13 in death HIV+TB+ groups compared to survived groups, but less likely predict the mortality. Mekonnen and his colleagues demonstrated, NOD1 was identified novel genetic associations with TB in Ethiopian populations 35. NOD1 plays important roles in the detection of bacteria and the production of proinflammatory molecules, given that both signaling pathways lead to NF-κB and MAPK activation 36. NOD1 deficiency mice show increased susceptibility to lung infection, which is associated with reduced neutrophil recruitment to the lungs 37, and associated with the development of inflammatory disorders 38. In the contrast of the other gene expression, the gene expression of IL-4δ2 was higher in death HIV+TB+ groups compared to survive matched controls that might be correlated with disease severity 39,40. However, IL-4δ2 may has less probable to predict the mortality; [AUC (95%CI) = 0.77 (0.57 - 0.97)].
In conclusion, the expression of PTPRCv1, CD3E, CCL5 and IL7R in peripheral blood can predict the mortality in HIV+TB+ co-infected individuals. In the future, the identified biomarkers could be applied to facilitate the development of effective assays for both tuberculosis and HIV diseases, the discovery of novel therapeutic targets and enable appropriate risk stratification to target new interventions appropriately, and aid monitoring of treatment responses. Future work could determine to completely characterise these signatures in different populations and larger study populations.