Delayed-onset adenosine deaminase deficiency with a novel synonymous mutation and a case series from China

Background Adenosine deaminase(ADA)is a key enzyme in the purine salvage pathway.Genetic defects of the ADA gene can cause a subtype of severe combined immunodeficiency.To date,few Chinese cases have been reported.Methods We retrospectively reviewed the medical records of patients diagnosed with ADA deficiency in Beijing Children's Hospital and summarized the previously published ADA deficiency cases from China in the literature.Results Nine patients were identified with two novel mutations(W272X and Q202=).Early-onset infection,thymic abnor-malities and failure to thrive were the most common manifestations of Chinese ADA-deficient patients.The ADA genotype has a major effect on the clinical phenotype.Notably,a novel synonymous mutation(c.606G>A,p.Q202=)was identified in a delayed-onset patient,which affected pre-mRNA splicing leading to a frameshift and premature truncation of the protein.Furthermore,the patient showed γδT cells expansion with an increased effect or phenotype,which may be associated with the delayed onset of disease.In addition,we reported cerebral aneurysm and intracranial artery stenosis for the first time in ADA deficiency.Five patients died with a median age of four months,while two patients received stem cell transplantation and are alive.Conclusions This study described the first case series of Chinese ADA-deficient patients.Early-onset infection,thymic abnormalities and failure to thrive were the most common manifestations in our patients.We identified a synonymous muta-tion that affected pre-mRNA splicing in the ADA gene,which had never been reported in ADA deficiency.Furthermore,we reported cerebral aneurysm in a delayed-onset patient for the first time.Further study is warranted to investigate the underlying mechanisms.

Combined detections of interleukin 27, interferon-γ, and adenosine deaminase in pleural effusion for diagnosis of tuberculous pleurisy

Background Previous studies reported interleukin-27 （IL-27）, interferon-y （IFN-γ）, or adenosine deaminase （ADA） alone plays a helpful role in diagnosing tuberculous pleural effusion （TPE）. The present study aims at comparing the diagnostic accuracy of pleural IL-27, IFN-γ, and ADA, and investigate the diagnostic accuracy of the combination of IL-27, IFN-γ, or/ and ADA for differentiating TPE from pleural effusions with the other etiologies. Methods The concentrations of IL-27, IFN-γ and ADA were simultaneously determined in pleural fluids and sera from 40 patients with TPE; 26 with malignant pleural effusion, seven with infectious pleural effusion, and eight with transudative pleural effusion by enzyme linked immunosorbent assay and colorimetric method. The corresponding biochemical indexs were also simultaneously determined. Results The concentrations of pleural IL-27 and IFN-γ in the tuberculous group were significantly higher than those in the malignant, infectious, and transudative groups. The concentrations of ADA in TPE were significantly higher than those in MPE or transudative effusions, while much lower than those in infectious effusions. Among these three biomarkers, IL- 27 was the most effective for TPE diagnosis, with the cut off value of 900.8 ng/L. IL-27 had a high sensitivity of 95% and specificity of 97.6% for differential diagnosis of TPE from non-TPEs. Combinations of IL-27, IFN-γ and ADA measurements further increased the sensitivity or specificity up to 100%. Conclusions Compared to non-TPEs, IL-27, IFN-γ and ADA all simultaneously increased in TPE; and among these three rapid detection methods, IL-27 appeared to be the best for distinguishing tuberculous from non-TPEs, especially from MPE. Combinations of the three markers （IL-27, IFN-γ and ADA） yielded the highest sensitivity and specificity. These findings suggest that the applications of a new biomarker, IL-27, alone or with IFN-γ and ADA, may contribute to more efficient diagnosis strategies in the management of tuberculous pleurisy.

Cysteine Not Required for Catalytic Activity of Adenosine Deaminase

Homology comparison of human, murine and E coli adenosine deaminases revealed a single conserved cysteine residue. On the basis of many previous reports indicating that there is an essential Cys residue involved in enzymatic activity, this conserved Cys was proposed to be the essential one involved in the catalytic activity of the enzyme. Using site directed mutagenesis and steady state kinetics, the role of the single conserved Cys residue was tested. However, results presented here indicate that this conserved Cys is not required for enzyme activity, strongly suggesting that cysteine should not be required for the enzymatic activity of adenosine deaminase. The preponderance of previously reported data indicating the “essentiality” of the Cys residue for enzymatic activity are discussed .

Gene therapy and genome editing for primary immunodeficiency diseases

In past two decades the gene therapy using genetic modified autologous hematopoietic stem cells(HSCs)transduced with the viral vector has become a promising alternative option for treating primary immunodeficiency diseases(PIDs).Despite of some pitfalls at early stage clinical trials,the field of gene therapy has advanced significantly in the last decade with improvements in viral vector safety,preparatory regime for manufacturing high quality virus,automated CD34 cell purification.Hence,the overall outcome from the clinical trials for the different PIDs has been very encouraging.In addition to the viral vector based gene therapy,the recent fast moving forward developments in genome editing using engineered nucleases in HSCs has provided a new promising platform for the treatment of PIDs.This review provides an overall outcome and progress in gene therapy clinical trials for SCID-X,ADA-SCID,WAS,X-CGD,and the recent developments in genome editing technology applied in HSCs for developing potential therapy,particular in the key studies for PIDs.

Genetics of severe combined immunodeficiency

Severe Combined Immunodeficiency(SCID)is an inherited group of rare,lifethreatening disorders due to the defect in T cell development and function.Clinical manifestations are characterised by recurrent and severe bacterial,viral,and fungal opportunistic infections that start from early infancy period.Haematopoietic stem cell transplantation(HSCT)is the treatment of choice.The pattern of inheritance of SCID may be X-linked or autosomal recessive.Though the diagnosis of SCID is usually established by flow cytometry-based tests,genetic diagnosis is often needed for genetic counselling,prognostication,and modification of pre-transplant chemotherapeutic agents.This review aims to highlight the genetic aspects of SCID.

Insight into the deamination mechanism of 6-cyclopropylamino guanosine analogs for anti-HIV drug design

Deamination is a crucial step in the transformation of 6-cyclopropylamino guanosine prodrug to its active form. A convenient method using capillary electrophoresis （CE） without sample labeling was developed to analyze the deamination of a series of D-/L-6-cyclopropylamino guanosine analogs by mouse liver homogenate, mouse liver microsome, and adenosine deaminase （ADA）. A two-step process involving a 6-amino guanosine intermediate formed by oxidative N-dealkylation was demonstrated in the metabolism of 6-cyclopropylamino guanosine to 6-hydroxy guanosine. The results indicated that the transformation rates of different prodrugs to the active form varied greatly, which were closely correlated with the configuration of nucleosides and the structure of glycosyl groups. Most importantly, D-form analogs were metabolized much faster than their L-counterparts, thus clearly pointed out that compared to guanine, modification of glycosyl part might be a better choice for the development of L-Kuanosine analogs for the treatment of HIV,