Serum Adenosine Deaminase (ADA) Activity: A Novel Screening Test to Differentiate HIV Monoinfection From HIV-HBV and HIV-HCV Coinfections

Adenosine deaminase 2 regulates the activation of the toll-like receptor 9 in response to nucleic acids

Human cells contain two types of adenosine deaminases (ADA) each with unique properties: ADA1, which is present in all cells where it modulates intracellular functions and extracellular signaling, and ADA2, which is secreted by immune cells. The exact intracellular functions of ADA2 remain undetermined and less defined than those of ADA1. ADA2 has distinct characteristics, such as low adenosine affinity, heparin-binding ability, and putative lysosomal entry. Here, we confirm that ADA2 is a lysosomal protein that binds toll-like receptor 9 (TLR9) agonists, specifically CpG oligodeoxynucleotides (CpG ODNs). We show that interferon-alpha (IFN-α) is secreted in response to TLR9 activation by CpG ODNs and natural DNA and markedly increases when ADA2 expression is downregulated in plasmacytoid dendritic cells (pDCs). Additionally, the pretreatment of pDCs with RNA further stimulates IFN-α secretion by pDCs after activation with CpG ODNs. Our findings indicate that ADA2 regulates TLR9 responses to DNA in activated pDCs. In conclusion, decreasing ADA2 expression or blocking it with specific oligonucleotides can enhance IFN-α secretion from pDCs, improving immune responses against intracellular infections and cancer.

Adenosine Deaminase as a Potential Diagnostic and Prognostic Biomarker for Severe Fever with Thrombocytopenia Syndrome

BACKGROUND

Severe fever with thrombocytopenia syndrome (SFTS) is a serious infectious disease caused by the Dabie bandavirus, with a high mortality rate. Currently, there are no effective vaccines or specific treatments for SFTS. Early diagnosis and accurate severity assessment are crucial.

METHODS

This study included 171 cases of SFTS, COVID-19, and hepatitis B virus (HBV) patients and healthy controls. We compared the serum adenosine deaminase (ADA) activity across these groups. The diagnostic and prognostic efficiency of serum ADA for SFTS was evaluated by using receiver operating characteristic (ROC) curve analysis. We also examined the correlation between serum ADA in SFTS patients and clinical lab parameters as well as serum cytokines.

RESULTS

SFTS patients had significantly higher serum ADA activity than those of COVID-19, HBV patients, and healthy controls. Nonsurvivor SFTS patients had notably higher ADA than survivors. ROC analysis indicated ADA as an effective SFTS diagnostic and prognostic biomarker. ADA correlated with prognosis, viral load, APTT, PT, AST, ferritin, negatively with HDL-c and LDL-c, and positively with cytokines like IL-6, TNF-α, and IL-1β. Multiorgan failure patients showed significant ADA increase.

CONCLUSION

Elevated serum ADA activity in SFTS patients is linked with disease severity and prognosis, showing potential as a diagnostic and prognostic biomarker for SFTS.

Biomarkers for Assessment of Human Immunodeficiency Virus and its Co-Infection with Hepatitis B and Hepatitis C Viruses: A Comprehensive Review

Recently, prevalence of hepatitis B virus (HBV), and hepatitis C virus (HCV) co-infection with Human immunodeficiency virus (HIV), has dramatically increased worldwide due to their shared routes of transmission. Compared to the sporadic infection with HIV, HBV, and HCV, concurrent infection with these agents increases the complications of these viruses. Furthermore, co-infection may also alter the therapeutic strategies against HIV. Accordingly, choosing appropriate biomarkers to detect these co-infections is one of the main concerns in the field of diagnostic pathology. Up to now, several markers have been introduced for the simultaneous diagnosis of HIV, HBV, and HCV. In this regard, serum adenosine deaminase activity (ADA), FibroTests, AST-to-Platelet Ratio Index (APRI), Fibrosis-4, Hyaluronic acid, and micro ribonucleic acids (MiR) have been investigated as potential biomarkers for diagnosis of HIV-HCV/HBV co-infections. This review summarizes diagnostic values of the current and emerging biomarkers in HIV patients concurrently infected with HBV and HCV.

ELISA based assays to measure adenosine deaminases concentration in serum and saliva for the diagnosis of ADA2 deficiency and cancer

Adenosine deaminases (ADAs) are enzymes of purine metabolism converting adenosine to inosine. There are two types of ADAs in humans ADA1 and ADA2. While both ADA1 and ADA2 share the same substrate, they differ in expression, cellular localization, and catalytic properties. The genetic deficiency of ADA1 results in severe combined immunodeficiency (SCID), while lack in ADA2 (DADA2) results in multiple phenotypes ranging from systemic inflammation to vascular pathology. Clinical studies have shown that the levels of ADAs in biological fluids are altered in pathophysiological conditions, suggesting that ADA activity could be a convenient marker for the diagnosis of immune diseases and cancer. Here, we describe sensitive and straightforward ELISA assays to measure ADA1 and ADA2 concentrations in biological fluids. Analysis of the serum and saliva samples from the healthy controls and DADA2 patients revealed that ADA2 enzyme concentration is significantly lower in patients than in healthy controls. In contrast, the concentration of ADA2 increases in the serum of patients with large granular leukocyte leukemia (LGLL) and patients’ saliva with head and neck cancer. Thus, this simple, non-invasive method allows for distinguishing healthy controls from the affected patient. It can be implemented in screening and diagnosis of DADA2 and follow up the treatment of LGLL and several types of head and neck cancer.

Sequence-Based Screening of Patients With Idiopathic Polyarteritis Nodosa, Granulomatosis With Polyangiitis, and Microscopic Polyangiitis for Deleterious Genetic Variants in ADA2

OBJECTIVE

Deficiency of adenosine deaminase 2 (DADA2) is a monogenic form of vasculitis that can resemble polyarteritis nodosa (PAN). This study was undertaken to identify potential disease-causing sequence variants in ADA2 in patients with idiopathic PAN, granulomatosis with polyangiitis (GPA), or microscopic polyangiitis (MPA).

METHODS

Patients with idiopathic PAN (n = 118) and patients with GPA or MPA (n = 1,107) were screened for rare nonsynonymous variants in ADA2 using DNA sequencing methods. ADA-2 enzyme activity was assessed in selected serum samples.

RESULTS

Nine of 118 patients with PAN (7.6%) were identified as having rare nonsynonymous variants in ADA2. Four patients (3.4%) were biallelic for pathogenic or likely pathogenic variants, and 5 patients (4.2%) were monoallelic carriers for 3 variants of uncertain significance and 2 likely pathogenic variants. Serum samples from 2 patients with PAN with biallelic variants were available and showed markedly reduced ADA-2 enzyme activity. ADA-2 enzyme testing of 86 additional patients revealed 1 individual with strongly reduced ADA-2 activity without detectable pathogenic variants. Patients with PAN and biallelic variants in ADA2 were younger at diagnosis than patients with 1 or no variant in ADA2, with no other clinical differences noted. None of the patients with GPA or MPA carried biallelic variants in ADA2.

CONCLUSION

A subset of patients with idiopathic PAN meet genetic criteria for DADA2. Given that tumor necrosis factor inhibition is efficacious in DADA2 but is not conventional therapy for PAN, these findings suggest that ADA-2 testing should strongly be considered in patients with hepatitis B virus-negative idiopathic PAN.

A rapid assay to screen adenosine deaminase inhibitors from Ligustri Lucidi Fructus against metabolism of cordycepin utilizing ultra-high-performance liquid chromatography-tandem mass spectrometry

Cordycepin has recently received increased attention owing to its extensive pharmacological activity. Adenosine deaminase (ADA) is widely distributed in mammalian blood and tissues; as a result, cordycepin is quickly metabolized upon entering into the body and converted into the inactive metabolite 3'-deoxyinosine, thus limiting its activity when administered alone. We herein present a novel ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for screening ADA inhibitors against the metabolism of cordycepin. Cordycepin and 3'-deoxyinosine were chosen as substrate and product, respectively. A proper separation was achieved for all analytes within 3 min. 3'-Deoxyinosine was quantified in the presence or absence of potential ADA inhibitors to evaluate ADA activity. The assay can simultaneously determine substrate and product, with the endogenous substance and ADA inhibitors added not interfering in its activity. After optimizing the enzymatic incubation and UHPLC-MS/MS conditions, Km and Vmax values for ADA deamination of cordycepin were 95.18 ± 7.85 μm and 363.90 ± 12.16 μmol/min/unit, respectively. Oleanolic acid and ursolic acid from Ligustri Lucidi Fructus were chosen as ADA inhibitors with half maximal inhibitory concentration values of 21.82 ± 0.39 and 18.41 ± 0.14 μm, respectively. A non-competitive inhibition model was constructed and this assay can be used to screen other potential ADA inhibitors quickly and accurately.

Adenosine deaminase inhibition

Adenosine deaminase is a critical enzyme in purine metabolism that regulates intra and extracellular adenosine concentrations by converting it to inosine. Adenosine is an important purine that regulates numerous physiological functions by interacting with its receptors. Adenosine and consequently adenosine deaminase can have pro or anti-inflammatory effects on tissues depending on how much time has passed from the start of the injury. In addition, an increase in adenosine deaminase activity has been reported for various diseases and the significant effect of deaminase inhibition on the clinical course of different diseases has been reported. However, the use of inhibitors is limited to only a few medical indications. Data on the increase of adenosine deaminase activity in different diseases and the impact of its inhibition in various cases have been collected and are discussed in this review. Overall, the evidence shows that many studies have been done to introduce inhibitors, however, in vivo studies have been much less than in vitro, and often have not been expanded for clinical use.

Adenosine signaling and adenosine deaminase regulation of immune responses: impact on the immunopathogenesis of HIV infection

Infection by human immunodeficiency virus (HIV) causes the acquired immune deficiency syndrome (AIDS), which has devastating effects on the host immune system. HIV entry into host cells and subsequent viral replication induce a proinflammatory response, hyperactivating immune cells and leading them to death, disfunction, and exhaustion. Adenosine is an immunomodulatory molecule that suppresses immune cell function to protect tissue integrity. The anti-inflammatory properties of adenosine modulate the chronic inflammation and immune activation caused by HIV. Lack of adenosine contributes to pathogenic events in HIV infection. However, immunosuppression by adenosine has its shortcomings, such as impairing the immune response, hindering the elimination of the virus and control of viral replication. By attempting to control inflammation, adenosine feeds a pathogenic cycle affecting immune cells. Deamination of adenosine by ADA (adenosine deaminase) counteracts the negative effects of adenosine in immune cells, boosting the immune response. This review comprises the connection between adenosinergic system and HIV immunopathogenesis, exploring defects in immune cell function and the role of ADA in protecting these cells against damage.