Identification of a Novel Keto Sugar Component in Streptococcus pneumoniae Serotype 12F Capsular Polysaccharide and Impact on Vaccine Immunogenicity

Implementation of conjugate vaccine technology revolutionized the ability to effectively elicit long-lasting immune responses to bacterial capsular polysaccharides. Although expansion of conjugate vaccine serotype coverage is designed to target residual disease burden to pneumococcal serotypes not contained in earlier vaccine versions, details of polysaccharide Ag structure, heterogeneity, and epitope structure components contributing to vaccine-mediated immunity are not always clear. Analysis of Streptococcus pneumoniae serotype 12F polysaccharide by two-dimensional nuclear magnetic resonance spectroscopy and mass spectrometry revealed a partial substitution of N-acetyl-galactosamine by the keto sugar 2-acetamido-2,6-dideoxy-xylo-hexos-4-ulose (Sug) in up to 25% of the repeat units. This substitution was not described in previous published structures for 12F. Screening a series of contemporary 12F strains isolated from humans (n = 17) identified Sug incorporation at varying levels in all strains examined. Thus, partial Sug substitution in S. pneumoniae serotype 12F may have always been present but is now detectable by state-of-the-art analytical techniques. During the steps of conjugation, the serotype 12F Sug epitope is modified by reduction, and both polysaccharide PPSV23 and conjugate PCV20 vaccines contain 12F Ags with little to no Sug epitope. Both PCV20 and PPSV23 vaccines were evaluated for protection against circulating 12F strains with varying amounts of Sug in their repeat unit based on an opsonophagocytic killing assay involving HL-60 cells and rabbit complement. Both vaccines elicited human-derived neutralizing Abs against serotype 12F, independent of Sug level between ∼2 and 25 mol%. These findings suggest that the newly identified serotype 12F Sug epitope is likely not an essential epitope for vaccine-elicited protection.

A comprehensive molecular study identified 12 complementation groups with 56 novel FANC gene variants in Indian Fanconi anemia subjects

Fanconi anemia (FA) is a rare autosomal or X-linked genetic disorder characterized by chromosomal breakages, congenital abnormalities, bone marrow failure (BMF), and cancer. There has been a discovery of 22 FANC genes known to be involved in the FA pathway. This wide number of pathway components makes molecular diagnosis challenging for FA. We present here the most comprehensive molecular diagnosis of FA subjects from India. We observed a high frequency (4.42 ± 1.5 breaks/metaphase) of chromosomal breakages in 181 FA subjects. The major clinical abnormalities observed were skin pigmentation (70.2%), short stature (46.4%), and skeletal abnormalities (43.1%), along with a few minor clinical abnormalities. The combination of Sanger sequencing and Next Generation Sequencing could molecularly characterize 164 (90.6%) FA patients and identified 12 different complementation groups [FANCA (56.10%), FANCG (16.46%), FANCL (12.80%), FANCD2 (4.88%), FANCJ (2.44%), FANCE (1.22%), FANCF (1.22%), FANCI (1.22%), FANCN (1.22%), FANCC (1.22%), FANCD1 (0.61%) and FANCB (0.61%)]. A total of 56 novel variants were identified in our cohort, including a hotspot variant: a deletion of exon 27 in the FANCA gene and a nonsense variant at c.787 C>T in the FANCG gene. Our comprehensive molecular findings can aid in the stratification of molecular investigation in the diagnosis and management of FA patients.

Clinical and Genetic Spectrum of a Large Cohort of Patients With Leukocyte Adhesion Deficiency Type 1 and 3: A Multicentric Study From India

Leukocyte adhesion deficiency (LAD) syndrome is a group of inborn errors of immunity characterized by a defect in the cascade of the activation and adhesion leading to the failure of leukocyte to migrate to the site of tissue injury. Three different types of LAD have been described. The most common subtype is LAD type 1 (LAD1) caused due to defects in the ITGβ2 gene. LAD type 2 (LAD2) is caused by mutations in the SLC35C1 gene leading to a generalized loss of expression of fucosylated glycans on the cell surface and LAD type 3 (LAD3) is caused by mutations in the FERMT3 gene resulting in platelet function defects along with immunodeficiency. There is a paucity of data available from India on LAD syndromes. The present study is a retrospective analysis of patients with LAD collated from 28 different centers across India. For LAD1, the diagnosis was based on clinical features and flow cytometric expression of CD18 on peripheral blood leukocytes and molecular confirmation by Sanger sequencing. For patients with LAD3 diagnosis was largely based on clinical manifestations and identification of the pathogenic mutation in the FERMT3 gene by next-generation Sequencing. Of the total 132 cases diagnosed with LAD, 127 were LAD1 and 5 were LAD3. The majority of our patients (83%) had CD18 expression less than 2% on neutrophils (LAD1°) and presented within the first three months of life with omphalitis, skin and soft tissue infections, delayed umbilical cord detachment, otitis media, and sepsis. The patients with CD18 expression of more than 30% (LAD1⁺) presented later in life with skin ulcers being the commonest manifestation. Bleeding manifestations were common in patients with LAD3. Persistent neutrophilic leukocytosis was the characteristic finding in all patients. 35 novel mutations were detected in the ITGβ2 gene, and 4 novel mutations were detected in the FERMT3 gene. The study thus presents one of the largest cohorts of patients from India with LAD, focusing on clinical features, immunological characteristics, and molecular spectrum.

Peripheral T cell lymphoma: Clinico-pathological characteristics & outcome from a tertiary care centre in south India

Background & objectives

Peripheral T cell lymphomas (PTCLs) are a heterogeneous group of non-Hodgkin's lymphomas (NHLs), with universally poor outcome. This study was undertaken to provide data on demographics and outcomes of patients with PTCL who underwent treatment in a single tertiary care centre in southern India.

Methods

Retrospective study was done on all patients (age ≥18 yr) diagnosed with PTCL from January 2007 to December 2012. The diagnosis of PTCL was made according to the WHO Classification of Tumors of Hematopoietic and Lymphoid Tissues.

Results

A total of 244 adult patients were diagnosed with PTCL (non-cutaneous). The most common subtype was PTCL-not otherwise specified (35.7%), followed by anaplastic large cell lymphoma (ALCL), ALK negative (21.3%), natural killer/T cell lymphoma, angioimmunoblastic T-cell lymphoma (AITL), ALCL, ALK positive, hepatosplenic T cell lymphoma (HSTCL) and adult T cell leukaemia/lymphoma followed in frequency with 13.1, 11.5, 8.6, 8.2 and 1.6 per cent cases, respectively. The three-year Kaplan-Meier overall survival (OS) and event-free survival (EFS) for the patients who received chemotherapy (n=122) were 33.8±5.0 and 29.3±4.7 per cent, respectively. Various prognostic indices developed for T cell lymphomas were found to be useful.

Interpretation & conclusions

Except for ALCL, ALK positive, all other PTCLs showed poor long-term outcome with CHOP-based chemotherapy. Novel therapies are needed to improve the outcome.

Allogeneic Stem Cell Transplant for Acute Myeloid Leukemia: Evolution of an Effective Strategy in India

Purpose There are limited data from developing countries on the role and cost-effectiveness of allogeneic stem cell transplantation (allo-SCT) for patients with acute myeloid leukemia (AML). Patients and Methods We undertook a retrospective descriptive study of all patients with AML who underwent allo-SCT from 1994 to 2013 at our center to evaluate the clinical outcomes and cost-effectiveness of this therapeutic modality. Results Two hundred fifty-four consecutive patients, median age 34 years, who underwent allo-SCT at our center were included in this study. There were 161 males (63.4%). The 5-year overall survival (OS) and event-free survival for the entire cohort was 40.1 ± 3.5% and 38.7 ± 3.4%, respectively. The 5-year OS for patients in first (CR1), second, and third complete remission and with disease/refractory AML was 53.1 ± 5.2%, 48.2 ± 8.3%, 31.2 ± 17.8%, and 16.0 ± 4.4%, respectively ( P < .001). From 2007, reduced intensity conditioning (RIC) with fludarabine and melphalan (Flu/Mel) was used in a majority of patients in CR1 (n = 67). Clinical outcomes were compared with historical conventional myeloablative conditioning regimens (n = 38). Use of Flu/Mel was associated with lower treatment-related mortality at 1 year, higher incidence of chronic graft-versus-host-disease, and comparable relapse rates. The 5-year OS and event-free survival for Flu/Mel and myeloablative conditioning group was 67.2 ± 6.6% versus 38.1 ± 8.1% ( P = .003) and 63.8 ± 6.4% versus 32.3 ± 7.9% ( P = .002), respectively. Preliminary cost analysis suggests that in our medical cost payment system, RIC allo-SCT in CR1 was likely the most cost-effective strategy in the management of AML. Conclusion In a resource-constrained environment, Flu/Mel RIC allo-SCT for AML CR1 is likely the most efficacious and cost-effective approach in a subset of newly diagnosed young adult patients.

Gaucher Disease Presenting in an Adult with Intracerebral Bleed

Gaucher disease (GD) is the most common lysosomal storage disorder, caused by deficiency of acid beta glucosidase. GD usually presents in children but occasional cases can present in adulthood. Here we report a case of type I GD in a 37 year old female who presented with intracerebral bleed due to long standing thrombocytopenia. She underwent splenectomy in view of limited resources for enzyme replacement therapy. With splenectomy her platelet counts normalised and neurological status also improved.

Population pharmacokinetics of Daunorubicin in adult patients with acute myeloid leukemia

PURPOSE

Chemotherapy drug resistance and relapse of the disease have been the major factors limiting the success of acute myeloid leukemia (AML) therapy. Several factors, including the pharmacokinetics (PK) of Cytarabine (Ara-C) and Daunorubicin (Dnr), could contribute to difference in treatment outcome in AML.

METHODS

In the present study, we evaluated the plasma PK of Dnr, the influence of genetic polymorphisms of genes involved in transport and metabolism of Dnr on the PK, and also the influence of these factors on clinical outcome. Plasma levels of Dnr and its major metabolite, Daunorubicinol (DOL), were available in 70 adult de novo AML patients. PK parameters (Area under curve (AUC) and clearance (CL)) of Dnr and DOL were calculated using nonlinear mixed-effects modeling analysis performed with Monolix. Genetic variants in ABCB1, ABCG2, CBR1, and CBR3 genes as well as RNA expression of CBR1, ABCB1, and ABCG2 were compared with Dnr PK parameters.

RESULTS

The AUC and CL of Dnr and DOL showed wide inter-individual variation. Patients with an exon1 variant of rs25678 in CBR1 had significantly higher plasma Dnr AUC [p = 0.05] compared to patients with wild type. Patients who achieved complete remission (CR) had significantly lower plasma Dnr AUC, Cmax, and higher CL compared to patients who did not achieve CR.

CONCLUSION

Further validation of these findings in a larger cohort of AML patients is warranted before establishing a therapeutic window for plasma Dnr levels and targeted dose adjustment.