Translational research in myelodysplastic syndromes

The myelodysplastic syndromes (MDS) are receiving unusual attention recently as great strides have been made in understanding the biology. Recognition that excessive cytokine-induced apoptosis plays a significant role in the cytopenias of the majority of patients opened the doors to anti-cytokine therapy, with thalidomide being used with success in approximately 20% patients. Other therapies that have emerged include the thalidomide analog lenalidomide which is particularly beneficial for 5q- patients as well as a subset of non-5q- patients with low or intermediate-1 risk MDS. Other targeted therapies include vitamins, agents that are cytoprotective, differentiation inducers, anti-angiogenic, or immune modulatory. In addition, inhibitors of proteasome, methylation, histone deacetylation, farnesylation, receptor tyrosine kinases, topoisomerase, and matrix mettaloproteinases have yielded encouraging responses in subsets of patients. Specific therapies have also been developed for genetic abnormalities that lead to fusion genes (TEL-PDGFR-beta, or FIP1L1-PDGFR-alpha), or abnormal proteins due to mutations/functional inactivation (FLT3), dysregulated expression (EVI-1). In a short span of ten years, the field has evolved from having no effective therapy to offer the majority of MDS patients save chemotherapy, to having one FDA approved drug, several on the way to approval, and a number of novel agents producing exciting clinical results. This chapter summarizes the novel targets and targeted therapies in the rapidly evolving therapeutic landscape of MDS.     

Carcinoembryonic antigen-related cell adhesion molecule (CEACAM)-binding recombinant polypeptide confers protection against infection by respiratory and urogenital pathogens

The human-specific pathogens Neisseria meningitidis, N. gonorrhoea, Haemophilus influenzae and Moraxella catarrhalis share the property of targeting the carcinoembryonic antigen (CEA)-related cell adhesion molecules (CEACAMs) expressed on human epithelia. CEACAMs are signalling receptors implicated in cell adhesion and regulation of several physiological functions. Their targeting by pathogens can lead to tissue invasion. Although the CEACAM-binding ligands of the bacteria are structurally diverse, they target a common site on the receptor. We have generated a recombinant polypeptide that blocks the interactions of the mucosal pathogens with human epithelial cells and antibodies against it inhibit M. catarrhalis interactions with the receptor. As such, it is a potential antimicrobial agent to prevent infection via a strategy unlikely to promote bacterial resistance and a vaccine candidate against M. catarrhalis. In addition, it could serve more widely as a novel research tool and as a potential therapeutic agent in CEACAM-based physiological disorders.     

Antibodies recognizing a variety of different structural motifs on meningococcal Lip antigen fail to demonstrate bactericidal activity.

The neisserial Lip antigen is a conserved antigen associated with the pathogenic Neisseria species, and is composed of multiple repeats of a consensus pentapeptide. A series of monoclonal antibodies reacting with meningococcal Lip antigen were subjected to epitope mapping, using solid-phase synthetic peptides based on the consensus repeat sequence. The antibodies were found to recognize different continuous epitopes based on the consensus sequence. One monoclonal antibody was utilized in affinity chromatography to obtain purified Lip antigen and the antigen was used for immunization of mice. The resulting antisera did not recognize Lip antigen on Western blots but reacted specifically with Lip antigen in immune precipitation experiments, indicating that the predominant polyclonal immune response was directed against conformational epitopes. Despite the diversity of both continuous and conformational epitopes recognized by the antibodies produced, none of the antibodies demonstrated the ability to promote complement-mediated bactericidal activity. Thus despite its initial apparent promise as a potential vaccine candidate the case for the inclusion of Lip antigen in vaccine formulation cannot be supported at present.     

Evidence for a simple Cl conductance pathway in nutrient membrane of frog stomach

A decrease in nutrient Cl⁻ results in an increased negativity of the nutrient relative to the secretory side. The possibility emerged that Cl⁻ transport could be attributed to a neutral mechanism involving Cl⁻ in the nutrient membrane coupled to a simple Cl⁻ conductance pathway in the secretory membrane. The decrease in PD (potential difference) with a decrease in nutrient Cl⁻ could arise from a decrease in cellular Cl⁻ so that the ratio of Cl⁻ in cell to Cl⁻ in secretory solution was decreased. Experiments were designed to determine whether there was a need to assume a simple Cl⁻ conductance pathway. A 10-fold decrease in Cl⁻ gave in HCO₃⁻-containing nutrient solutions a PD decrease of 20 mV, in HCO₃⁻-free nutrient solutions, a PD decrease of 13.5 mV, and in HCO₃⁻-free and Na⁺-free solutions, a PD decrease of 6.7 mV. The decrease of 6.7 mV could not be attributed to a neutral Cl⁻HCO₃⁻ exchanger or a NaCl symport. Also there was no evidence for a KCl symport from changes in Cl⁻ in presence and absence of K⁺. It followed that the decrease of 6.7 mV provided evidence for a simple Cl⁻ conductance pathway in the nutrient membrane.     

Expression of pathogen-like Opa adhesins in commensal Neisseria: genetic and functional analysis

Several species of commensal Neisseriae (Cn) may colonize the human nasopharynx, but little is known about their adhesion mechanisms. We have investigated structural and functional similarities between adhesins of Cn and of Neisseria meningitidis (Nm), also a frequent colonizer of the nasopharynx. In this study, we demonstrate the expression of Opa-like proteins in nine strains of Cn. Phylogenetic analysis segregated the majority of the Cn Opa in a cluster separated from the pathogenic cluster with a few exceptions. One Opa, which located within the pathogenic cluster, was strikingly similar (74%) to an Opa of a Neisseria gonorrhoeae (Ng) strain and, like Ng, it lacked the extra Y¹¹ or the ¹³⁶DKF¹³⁸ triplet insert, which are conserved among many N. meningitidis Opa proteins. Most importantly, the majority of the Cn Opa proteins were able to interact with human CEACAM1 (CD66a) molecules, previously identified as receptors for pathogenic Opa proteins. By the use of CEACAM1 N-domain mutants, we demonstrate that Cn Opa target the same region of the N-domain of the receptor as that used by Nm. Furthermore, Cn strains bound to cell-expressed human CEACAM1. In competition assays, adherent Cn strain C450, exhibiting high affinity for CEACAM1, was not displaced by a Nm isolate and vice versa . But in simultaneous incubation, Nm out-competed the Cn strain. This is the first study to demonstrate the expression of adhesins in Cn that are structurally and functionally closely related to pathogenic adhesins. The studies imply that some Cn have the potential to occupy and thus compete with the pathogens for receptors on human mucosa, their common and exclusive niche.     

Electron Microscopic Localization of Herpesvirus-type Particles in Marek''s Disease

Upon cultivation of chicken lymphoid tumors induced by Georgia isolate of Marek's disease, clusters of refractile rounded cells appeared consistently in the cell cultures. Intranuclear mature, immature, enveloped, and empty herpesvirus-type particles, usually associated with smaller particles, were observed in all rounded cells in the affected areas. Cytoplasmic inclusions containing mature enveloped virus particles were also seen in the rounded cells. Often fibroblasts growing in the vicinity of the cytopathic effect area contained a few herpesvirus-type particles. The original tumors prior to cultivation did not reveal any virus particles, and the virus in infected cultures was always cell-associated. Control cell cultures neither developed the rounded cells nor demonstrated the presence of any type of virus particles.     

Genetic and expression deregulation of immunoregulatory genes in rheumatoid arthritis

Molecular Biology Reports - Rheumatoid arthritis (RA) is one of the most common autoimmune diseases globally, and is an important public health concern, associating with early death and systemic...