Successful Treatment of Refractory Post-Transplant Lymphoproliferative Disorder With Chimeric Antigen Receptor T-Cell Therapy in a Heart Transplant Recipient.

Post-transplant lymphoproliferative disorders (PTLDs) are opportunistic malignancies that complicate the success of hematopoietic stem cell or solid organ transplantation. These disorders often arise post-transplant due to the immunosuppression required for minimizing the risk of rejection of donor tissue. First-line treatment of these disorders includes limiting immunosuppression when permissible. Subsequent treatment includes the use of monoclonal anti-CD20 antibody (rituximab), and/or combination chemotherapy. Chimeric antigen receptor (CAR) T-cell therapy has revolutionized the treatment paradigm in many lymphoid malignancies. It is not approved for PTLD due to exclusion of PTLD patients from pivotal clinical trials. Also, its utilization post-transplant can be complex and multidisciplinary care is of utmost importance for successful administration of a potentially curative treatment. We present a 68-year-old patient with history of heart transplant for non-ischemic cardiomyopathy, diagnosed with PTLD that was refractory to treatment using current guidelines until successfully receiving CAR T-cell therapy.

Sitravatinib combined with PD-1 blockade enhances cytotoxic T-cell infiltration by M2 to M1 tumor macrophage repolarization in esophageal adenocarcinoma.

Esophageal adenocarcinoma (EAC) is a leading cause of cancer-related mortality. Sitravatinib is a novel multi-gene tyrosine kinase inhibitor (TKI) that targets tumor-associated macrophage (TAM) receptors, VEGF, PDGF and c-Kit. Currently, sitravatinib is actively being studied in clinical trials across solid tumors and other TKIs have shown efficacy in combination with immune checkpoint inhibitors (ICI) in cancer models. In this study, we investigated the anti-tumor activity of sitravatinib alone and in combination with PD-1 blockade in an EAC rat model. Treatment response was evaluated by mortality, pre- and post-treatment MRI, gene expression, immunofluorescence and immunohistochemistry. Our results demonstrated adequate safety and significant tumor shrinkage in animals treated with sitravatinib, and more profoundly, sitravatinib and PD-1 inhibitor, AUNP-12 (P < 0.01). Suppression of TAM receptors resulted in increased gene expression of pro-inflammatory cytokines and decreased expression of anti-inflammatory cytokines, enhanced infiltration of CD8+ T cells, and M2 to M1 macrophage phenotype repolarization in the tumor microenvironment of treated animals (P < 0.01). Moreover, endpoint immunohistochemistry staining corroborated the anti-tumor activity by downregulation of Ki67 and upregulation of Caspase-3 in the treated animals. Additionally, pretreatment gene expression of TAM receptors and PD-L1 were significantly higher in major responders compared with the non-responders, in animals that received sitravatinib and AUNP-12 (P < 0.02), confirming that TAM suppression enhances the efficacy of PD-1 blockade. In conclusion, this study proposes a promising immunomodulatory strategy using a multi-gene TKI to overcome developed resistance to an ICI in EAC, establishing rationale for future clinical development.

Cyclic Thrombocytopenia in the Setting of Intracranial Hemorrhage: A Diagnostic and Therapeutic Challenge.

Cyclic thrombocytopenia (CTP) as the name suggests presents with cyclic episodes of thrombocytopenia and is frequently initially misdiagnosed as immune thrombocytopenia. Following a lack of sustained response or abnormally increased response to common treatments used for immune thrombocytopenia, a proper diagnosis of CTP can then be made. Prior reports have shown a subset of patients who respond to cyclosporin A. Here, we present a case of CTP that was initially at another facility presumed to have and treated for immune thrombocytopenic purpura. However, after multiple attempts to treat with steroids, intravenous immunoglobulin (IVIG), rituximab, and eltrombopag, episodes of severe thrombocytopenia followed by thrombocytosis continued. The patient ultimately developed intracerebral hemorrhage (ICH) in the setting of one of the episodes of severe thrombocytopenia and developed multiple subsequent complications from which the patient unfortunately did not recover. It was only after developing ICH that the patient had been evaluated at a center with hematology consultation capabilities, at which time after a detailed review of his case and pattern recognition the proper diagnosis of CTP was made with initiation of cyclosporine. This case was further complicated by need to maintain an adequate platelet threshold post-ventriculoperitoneal shunt placement which was necessary due to his ICH and was placed before diagnosis of CTP could be made. While CTP is a rare diagnosis, this case reinforces a greater need to properly diagnose and consider cyclosporine treatment for CTP, as it has been effective in some patients and may help to prevent patient morbidity and especially catastrophic bleeding complications.

Branched montbretin A mimics allow derivatisation and potent amylase inhibition.

Mimics of the complex flavonol glycoside montbretin A in which a flavonol moiety is coupled to a caffeic acid via partially peptidic linkers have proved to be potent inhibitors of human pancreatic alpha-amylase with potential as therapeutics for control of blood glucose levels. After exploring optimal linker length, a synthetic route to a version with a branched linker was devised based on the structure of the enzyme/inhibitor complex. The resultant branched inhibitors were shown to retain nanomolar potency even when decorated with polymers as a means of modifying solubility. Similar improvements, along with nanomolar affinity, could also be achieved through conjugation to cyclodextrins which have the potential to bind to starch binding sites found on the surface of human amylase. Incorporation of a conjugatable branch into this unusual pharmacophore thereby affords considerable flexibility for further modifications to improve pharmacokinetic behaviour or as a site for attachment of capture tags or fluorophores.

SARS-CoV-2 utilization of ACE2 from different bat species allows for virus entry and replication in vitro.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is believed to have a zoonotic origin with bats suspected as a natural host. In this work, we individually express the ACE2 of seven bat species including, little brown, great roundleaf, Pearson's horseshoe, greater horseshoe, Brazilian free-tailed, Egyptian rousette, and Chinese rufous horseshoe in DF1 cells and determine their ability to support attachment and replication of SARS-CoV-2 viruses. We demonstrate that the ACE2 receptor of all seven species made DF1 cells permissible to SARS-CoV-2. The level of virus replication differed between bat species and variants tested. The Wuhan lineage SARS-CoV-2 virus replicated to higher titers than either variant virus tested. All viruses tested grew to higher titers in cells expressing the human ACE2 gene compared to a bat ACE2. This study provides a practical in vitromethod for further testing of animal species for potential susceptibility to current and emerging SARS-CoV-2 viruses.

Identification of a second glycoform of the clinically prevalent O1 antigen from Klebsiella pneumoniae.

Carbapenemase and extended ß-lactamase-producing Klebsiella pneumoniae isolates represent a major health threat, stimulating increasing interest in immunotherapeutic approaches for combating Klebsiella infections. Lipopolysaccharide O antigen polysaccharides offer viable targets for immunotherapeutic development, and several studies have described protection with O-specific antibodies in animal models of infection. O1 antigen is produced by almost half of clinical Klebsiella isolates. The O1 polysaccharide backbone structure is known, but monoclonal antibodies raised against the O1 antigen showed varying reactivity against different isolates that could not be explained by the known structure. Reinvestigation of the structure by NMR spectroscopy revealed the presence of the reported polysaccharide backbone (glycoform O1a), as well as a previously unknown O1b glycoform composed of the O1a backbone modified with a terminal pyruvate group. The activity of the responsible pyruvyltransferase (WbbZ) was confirmed by western immunoblotting and in vitro chemoenzymatic synthesis of the O1b terminus. Bioinformatic data indicate that almost all O1 isolates possess genes required to produce both glycoforms. We describe the presence of O1ab-biosynthesis genes in other bacterial species and report a functional O1 locus on a bacteriophage genome. Homologs of wbbZ are widespread in genetic loci for the assembly of unrelated glycostructures in bacteria and yeast. In K. pneumoniae, simultaneous production of both O1 glycoforms is enabled by the lack of specificity of the ABC transporter that exports the nascent glycan, and the data reported here provide mechanistic understanding of the capacity for evolution of antigenic diversity within an important class of biomolecules produced by many bacteria.

Survival Benefit with Re-resection and Optimal Time to Re-resection in Gallbladder Cancer: a National Cancer Database Study.

PURPOSE: Gallbladder cancer is often diagnosed incidentally after cholecystectomy. Most patients will then undergo re-resection for potential residual disease; however, overall survival (OS) benefit data in this scenario is variable. This National Cancer Database analysis (NCDB) compared OS in patients with T1b-T3 gallbladder cancer who underwent re-resection and evaluated if time to resection impacts OS. METHODS: We reviewed the NCDB for patients who received initial cholecystectomy for gallbladder cancer and were subsequently eligible for re-resection based on tumor stage (T1b-T3 disease). Patients with re-resection were subdivided into four cohorts based on time to re-resection: 0-4 weeks, 5-8 weeks, 9-12 weeks, and > 12 weeks. We used a Cox proportional hazards ratio to identify factors associated with worse survival and logistic regression to evaluate characteristics associated with re-resection. OS was calculated using Kaplan Meier curves. RESULTS: A total of 791 (5.82%) patients received re-resection. Cox proportional hazards analysis showed a comorbidity score of 1 was associated with worse survival. Patients with higher comorbidity scores and treatment at comprehensive community, integrated, or academic cancer programs were less likely to undergo re-resection. Re-resection showed significantly improved OS [HR 0.87; 95 CI 0.77-0.98; p = 0.0203]. Improved survival was appreciated when re-resection was completed at 5-8 weeks [HR 0.67; CI 0.57-0.81], 9-12 weeks [HR 0.64; CI 0.52-0.79], or > 12 weeks [HR 0.61; CI 0.47-0.78] compared to 0-4 weeks. CONCLUSION: Optimal timing to re-resection in gallbladder cancer supports previous data showing benefit at > 4 weeks. However, there was no significant survival difference as to whether re-resection was completed at 5-8 weeks, 9-12 weeks, or > 12 weeks post initial cholecystectomy.

A Case of Vancomycin-Induced Severe Immune Thrombocytopenia.

A male in his 60s presented with left lower extremity fractures following a vehicle accident. Hemoglobin, initially, was 12.4 mmol/L, and platelet count was 235 k/mcl. On day 11 of admission, his platelet count initially dropped to 99 k/mcl, and after recovery it rapidly decreased to 11 k/mcl on day 16 when the INR was 1.3 and aPTT was 32 s, and he continued to have a stable anemia throughout admission. There was no response in platelet count post-transfusion of four units of platelets. Hematology initially evaluated the patient for disseminated intravascular coagulation, heparin-induced thrombocytopenia (anti-PF4 antibody was 0.19), and thrombotic thrombocytopenic purpura (PLASMIC score of 4). Vancomycin was administered on days 1-7 for broad spectrum antimicrobial coverage and day 10, again, for concerns of sepsis. Given the temporal association of thrombocytopenia and vancomycin administration, a diagnosis of vancomycin-induced immune thrombocytopenia was established. Vancomycin was discontinued, and 2 doses of 1000 mg/kg of intravenous immunoglobulin 24 h apart were administered with the subsequent resolution of thrombocytopenia.

Diffuse Large B Cell Lymphoma Raising Suspicion for an Infection: A Case Report.

Newly discovered liver lesions have a broad differential ranging from malignancy to infection. While tissue biopsy is the gold standard diagnostic modality, imaging can also aid in diagnosis. Hepatocellular carcinoma (HCC) can be diagnosed via imaging alone; however, masses suspicious for infection ultimately require biopsy and culture. We report a case of a 72-year-old male who presented with subjective fever, nausea, decreased appetite, dark urine, elevated liver function tests, and CT evidence of an exophytic liver mass. Differentials included infections such as hepatobiliary actinomycosis, abscess, solid malignancy, or lymphoma. Obtaining a definitive diagnosis with tissue biopsy endoscopically and percutaneously was quite difficult due to the location of the lesion around the porta hepatis. Subsequent laparoscopic biopsy revealed diffuse large B cell lymphoma (DLBCL).

Vinyl Halide-Modified Unsaturated Cyclitols are Mechanism-Based Glycosidase Inhibitors.

Suitably configured allyl ethers of unsaturated cyclitols act as substrates of ß-glycosidases, reacting via allylic cation transition states. Incorporation of halogens at the vinylic position of these carbasugars, along with an activated leaving group, generates potent inactivators of ß-glycosidases. Enzymatic turnover of these halogenated cyclitols (F, Cl, Br) displayed a counter-intuitive trend wherein the most electronegative substituents yielded the most labile pseudo-glycosidic linkages. Structures of complexes with the Sulfolobus ß-glucosidase revealed similar enzyme-ligand interactions to those seen in complexes with a 2-fluorosugar inhibitor, the lone exception being displacement of tyrosine 322 from the active site by the halogen. Mutation of Y322 to Y322F largely abolished glycosidase activity, consistent with lost interactions at O5, but minimally affected (7-fold) rates of carbasugar hydrolysis, yielding a more selective enzyme for unsaturated cyclitol ether hydrolysis.

Development of an in vitro model for animal species susceptibility to SARS-CoV-2 replication based on expression of ACE2 and TMPRSS2 in avian cells.

The SARS-CoV-2 (SARS-CoV-2) virus has caused a worldwide pandemic because of the virus's ability to transmit efficiently human-to-human. A key determinant of infection is the attachment of the viral spike protein to the host receptor angiotensin-converting enzyme 2 (ACE2). Because of the presumed zoonotic origin of SARS-CoV-2, there is no practical way to assess the susceptibility of every species to SARS-CoV-2 by direct challenge studies. In an effort to have a better predictive model of animal host susceptibility to SARS-CoV-2, we expressed the ACE2 and/or transmembrane serine protease 2 (TMPRSS2) genes from humans and other animal species in the avian fibroblast cell line, DF1, that is not permissive to infection. We demonstrated that expression of both human ACE2 and TMPRSS2 genes is necessary to support SARS-CoV-2 infection and replication in DF1 and a non-permissive sub-lineage of MDCK cells. Titers of SARS-CoV-2 in these cell lines were comparable to those observed in control Vero cells. To further test the model, we developed seven additional transgenic cell lines expressing the ACE2 and TMPRSS2 derived from Felis catus (cat), Equus caballus (horse), Sus domesticus (pig), Capra hircus (goat), Mesocricetus auratus (Golden hamster), Myotis lucifugus (Little Brown bat) and Hipposideros armiger (Great Roundleaf bat) in DF1 cells. Results demonstrate permissive replication of SARS-CoV-2 in cat, Golden hamster, and goat species, but not pig or horse, which correlated with the results of reported challenge studies. Cells expressing genes from either bat species tested demonstrated temporal replication of SARS-CoV-2 that peaked early and was not sustained. The development of this cell culture model allows for more efficient testing of the potential susceptibility of many different animal species for SARS-CoV-2 and emerging variant viruses.

Hypercellular bone marrow in aplastic anemia: A case report of two patients.

Aplastic anemia is a disorder of bone marrow failure characterized by a hypocellular bone marrow. We report two cases with an initial hypercellular bone marrow at the time of presentation, suggesting a new phase in the pathogenesis of the disease.

A bifunctional O-antigen polymerase structure reveals a new glycosyltransferase family.

Lipopolysaccharide O-antigen is an attractive candidate for immunotherapeutic strategies targeting antibiotic-resistant Klebsiella pneumoniae. Several K. pneumoniae O-serotypes are based on a shared O2a-antigen backbone repeating unit: (→ 3)-α-Galp-(1 → 3)-ß-Galf-(1 →). O2a antigen is synthesized on undecaprenol diphosphate in a pathway involving the O2a polymerase, WbbM, before its export by an ATP-binding cassette transporter. This dual domain polymerase possesses a C-terminal galactopyranosyltransferase resembling known GT8 family enzymes, and an N-terminal DUF4422 domain identified here as a galactofuranosyltransferase defining a previously unrecognized family (GT111). Functional assignment of DUF4422 explains how galactofuranose is incorporated into various polysaccharides of importance in vaccine production and the food industry. In the 2.1-Å resolution structure, three WbbM protomers associate to form a flattened triangular prism connected to a central stalk that orients the active sites toward the membrane. The biochemical, structural and topological properties of WbbM offer broader insight into the mechanisms of assembly of bacterial cell-surface glycans.

Development of an active site titration reagent for α-amylases.

α-Amylases are among the most widely used classes of enzymes in industry and considerable effort has gone into optimising their activities. Efforts to find better amylase mutants, such as through high-throughput screening, would be greatly aided by access to precise and robust active site titrating agents for quantitation of active mutants in crude cell lysates. While active site titration reagents designed for retaining ß-glycosidases quantify these enzymes down to nanomolar levels, convenient titrants for α-glycosidases are not available. We designed such a reagent by incorporating a highly reactive fluorogenic leaving group onto unsaturated cyclitol ethers, which have been recently shown to act as slow substrates for retaining glycosidases that operate via a covalent 'glycosyl'-enzyme intermediate. By appending this warhead onto the appropriate oligosaccharide, we developed efficient active site titration reagents for α-amylases that effect quantitation down to low nanomolar levels.

New insights into lipopolysaccharide assembly and export.

Lipopolysaccharide is an important immunomodulatory and structural component found in the outer membrane of Gram-negative bacteria. The biosynthesis of this glycoconjugate proceeds by a highly conserved pathway and, as such, is an attractive target for antibiotic action. We highlight here recent work focused on understanding this pathway with an emphasis on new insights related to chain length control and transport across the inner and outer cell membranes.

Klebsiella pneumoniae O1 and O2ac antigens provide prototypes for an unusual strategy for polysaccharide antigen diversification.

A limited range of different structures is observed in O-antigenic polysaccharides (OPSs) from Klebsiella pneumoniae lipopolysaccharides. Among these, several are based on modifications of a conserved core element of serotype O2a OPS, which has a disaccharide repeat structure [→3)-α-d-Galp-(1→3)-ß-d-Galf-(1→]. Here, we describe the enzymatic pathways for a highly unusual modification strategy involving the attachment of a second glycan repeat-unit structure to the nonreducing terminus of O2a. This occurs by the addition of the O1 [→3)-α-d-Galp-(1→3)-ß-d-Galp-(1→] or O2c [→3)-ß-d-GlcpNAc-(1→5)-ß-d-Galf-(1→] antigens. The organization of the enzyme activities performing these modifications differs, with the enzyme WbbY possessing two glycosyltransferase catalytic sites solely responsible for O1 antigen polymerization and forming a complex with the O2a glycosyltransferase WbbM. In contrast, O2c polymerization requires glycosyltransferases WbmV and WbmW, which interact with one another but apparently not with WbbM. Using defined synthetic acceptors and site-directed mutants to assign the activities of the WbbY catalytic sites, we found that the C-terminal WbbY domain is a UDP-Galp-dependent GT-A galactosyltransferase adding ß-(1→3)-linked d-Galp, whereas the WbbY N terminus includes a GT-B enzyme adding α-(1→3)-linked d-Galp These activities build the O1 antigen on a terminal Galp in the O2a domain. Using similar approaches, we identified WbmV as the UDP-GlcNAc transferase and noted that WbmW represents a UDP-Galf-dependent enzyme and that both are GT-A members. WbmVW polymerizes the O2c antigen on a terminal Galf. Our results provide mechanistic and conceptual insights into an important strategy for polysaccharide antigen diversification in bacteria.

A Route to Polyprenol Pyrophosphate-Based Probes of O-Polysaccharide Biosynthesis in Klebsiella pneumoniae O2a.

An approach for the assembly of polyprenol pyrophosphate-based probes of O-polysaccharide biosynthesis in Klebsiella pneumoniae serotype O2a is described. This convergent route features high-yielding, diastereoselective glycosylations and the late-stage installation of the polyprenol pyrophosphate moiety. Although applied to the synthesis of a nonasaccharide bearing a farnesyl group (1), the modular nature of the route makes it amenable to the synthesis of additional derivatives containing either larger glycans or different lipid domains.

The LPG1x family from Leishmania major is constituted of rare eukaryotic galactofuranosyltransferases with unprecedented catalytic properties.

Galactofuranosyltransferases are poorly described enzymes despite their crucial role in the virulence and the pathogenicity of numerous microorganisms. These enzymes are considered as potential targets for therapeutic action. In addition to the only well-characterised prokaryotic GlfT2 from Mycobacterium tuberculosis, four putative genes in Leishmania major were previously described as potential galactofuranosyltransferases. In this study, we have cloned, over-expressed, purified and fully determined the kinetic parameters of these four eukaryotic enzymes, thus demonstrating their unique potency in catalysing the transfer of the galactofuranosyl moiety into acceptors. Their individual promiscuity revealed to be different, as some of them could efficiently use NDP-pyranoses as donor substrates in addition to the natural UDP-galactofuranose. Such results pave the way for the development of chemoenzymatic synthesis of furanosyl-containing glycoconjugates as well as the design of improved drugs against leishmaniasis.

Rearranged T Cell Receptor Sequences in the Germline Genome of Channel Catfish Are Preferentially Expressed in Response to Infection.

Rearranged V(D)J genes coding for T cell receptor α and ß chains are integrated into the germline genome of channel catfish. Previous analysis of expressed TCR Vß2 repertoires demonstrated that channel catfish express multiple public clonotypes, which were shared among all the fish, following infection with a common protozoan parasite. In each case a single DNA sequence was predominately used to code for a public clonotype. We show here that the rearranged VDJ genes coding for these expressed public Vß2 clonotypes can be amplified by PCR from germline DNA isolated from oocytes and erythrocytes. Sequencing of the Vß2 PCR products confirmed that these expressed public Vß2 clonotypes are integrated into the germline. Moreover, sequencing of PCR products confirmed that all five Vß gene families and Vα1 have rearranged V(D)J genes with diverse CDR3 sequences integrated into the germline. Germline rearranged Vß2 and Vß4 genes retain the intron between the leader and Vß sequence. This suggests that the germline rearranged TCR Vß genes arose through VDJ rearrangement in T cells, and subsequently moved into the germline through DNA transposon mediated transposition. These results reveal a new dimension to the adaptive immune system of vertebrates, namely: the expression of evolutionarily conserved, rearranged V(D)J genes from the germline.

Synthesis of the Campylobacter jejuni 81-176 Strain Capsular Polysaccharide Repeating Unit Reveals the Absolute Configuration of its O-Methyl Phosphoramidate Motif.

The O-methyl phosphoramidate (MeOPN) motif is a non-stoichiometric modification of capsular polysaccharides (CPS) in ≈70 % of all Campylobacter jejuni strains. Infections by C. jejuni lead to food-borne illnesses and the CPS they produce are key virulence factors. The MeOPN phosphorus atom in these CPS is stereogenic and is found as a single stereoisomer. However, to date, the absolute stereochemistry at this atom has been undefined. We report the synthesis of the three repeating units found in C. jejuni 81-176 CPS; one of these possesses a MeOPN group. In the course of these studies we established that the stereochemistry of the phosphorus atom in this MeOPN group is R. These studies represent the first unequivocal proof of stereochemistry of this group in any C. jejuni CPS. The compounds produced are anticipated to be useful tools in investigations targeting the function and biosynthesis of this structurally-interesting modification, which so far has only been identified in campylobacter.