Probing the biophysical interaction between Neocarzinostatin toxin and EpCAM RNA aptamer

Neocarzinostatin (NCS) a potent DNA-damaging, anti-tumor toxin extracted from Streptomyces carzinostaticus that recognizes double-stranded DNA bulge and induces DNA damage. 2 Fluoro (2F) Modified EpCAM RNA aptamer is a 23-mer that targets EpCAM protein, expressed on the surface of epithelial tumor cells. Understanding the interaction between NCS and the ligand is important for carrying out the targeted tumor therapy. In this study, we have investigated the biophysical interactions between NCS and 2-fluro Modified EpCAM RNA aptamer using Circular Dichroism (CD) and Infra-Red (IR) spectroscopy. The aromatic amino acid residues spanning the β sheets of NCS are found to participate in intermolecular interactions with 2 F Modified EpCAM RNA aptamer. In-silico modeling and simulation studies corroborate with CD spectra data. Furthermore, it reinforces the involvement of C and D1 strand of NCS in intermolecular interactions with EpCAM RNA aptamer. This the first report on interactions involved in the stabilization of NCS-EpCAM aptamer complex and will aid in the development of therapeutic modalities towards targeted cancer therapy.

Blood-stage Plasmodium infection induces CD8+ T lymphocytes to parasite-expressed antigens, largely regulated by CD8α+ dendritic cells

Although CD8+ T cells do not contribute to protection against the blood stage of Plasmodium infection, there is mounting evidence that they are principal mediators of murine experimental cerebral malaria (ECM). At present, there is no direct evidence that the CD8+ T cells mediating ECM are parasite-specific or, for that matter, whether parasite-specific CD8+ T cells are generated in response to blood-stage infection. To resolve this and to define the cellular requirements for such priming, we generated transgenic P. berghei parasites expressing model T cell epitopes. This approach was necessary as MHC class I-restricted antigens to blood-stage infection have not been defined. Here, we show that blood-stage infection leads to parasite-specific CD8+ and CD4+ T cell responses. Furthermore, we show that P. berghei-expressed antigens are cross-presented by the CD8α+ subset of dendritic cells (DC), and that this induces pathogen-specific cytotoxic T lymphocytes (CTL) capable of lysing cells presenting antigens expressed by blood-stage parasites. Finally, using three different experimental approaches, we provide evidence that CTL specific for parasite-expressed antigens contribute to ECM.

Functional analysis of Plasmodium falciparum merozoite antigens : implications for erythrocyte invasion and vaccine development

Malaria is a major human health problem and is responsible for over 2 million deaths per year. It is caused by a number of species of the genus Plasmodium, and Plasmodium falciparum is the causative agent of the most lethal form. Consequently, the development of a vaccine against this parasite is a priority. There are a number of stages of the parasite life cycle that are being targeted for the development of vaccines. Important candidate antigens include proteins on the surface of the asexual merozoite stage, the form that invades the host erythrocyte. The development of methods to manipulate the genome of Plasmodium species has enabled the construction of gain-of-function and loss-of-function mutants and provided new strategies to analyse the role of parasite proteins. This has provided new information on the role of merozoite antigens in erythrocyte invasion and also allows new approaches to address their potential as vaccine candidates.