Preferential recognition of epitopes on peroxynitrite-modified alpha-2-macroglobulin by circulating autoantibodies in rheumatoid arthritis patients.

Autoimmune responses against post-translationally modified antigens are a hallmark of several autoimmune diseases. In this work, we have studied the changes in alpha-2-macroglobulin (α2M) upon modification by peroxynitrite. Furthermore, we have evaluated the immunogenicity of modified α2M in experimental rabbits and rheumatoid arthritis (RA) patients. Peroxynitrite-modified α2M showed disturbed microenvironment and altered aromatic residues under UV and fluorescence studies. Aggregation, reduction in ß-sheet content, production of nitrotyrosine and shift in amide I and II bands were observed in the modified α2M by polyacrylamide gel electrophoresis besides CD and FTIR spectroscopic analysis. The exposure of hydrophobic clusters and changes in contact positions were observed in ANS and ThT binding assays. Immunological studies using ELISA showed peroxynitrite-modified α2M as highly immunogenic producing high titre of specific antibodies in immunized rabbits. Cross-reactivity studies revealed the polyspecificity of the elicited antibodies. Direct binding ELISA and competitive inhibition studies confirmed the presence of circulating antibodies in the sera of RA patients having high specificity towards the peroxynitrite-modified α2M as compared to the native α2M. Sera from healthy (normal) human subjects showed lower binding with the native and modified protein. This study confirms that peroxynitrite induces structural modifications in α2M and makes it immunogenic. The presence of neo-antigenic determinants on modified α2M with enhanced binding for circulating autoantibodies in RA patients could offer new possibilities for diagnosis and etiopathology of the disease. Communicated by Ramaswamy H. Sarma.

Human papillomavirus: current status and issues of vaccination.

An association between human papillomavirus (HPV) infection and the development of cervical cancer was initially suggested over 30 years ago, and today there is clear evidence that certain subtypes of HPV are the causative agents of such malignancies. Papillomaviruses make up a vast family that comprises hundreds of different viruses. These viruses infect epithelia in humans and animals and cause benign hyperproliferative lesions, commonly called warts or papillomas, which can occasionally progress to squamous cell cancer. HPV infections are considered the most common among sexually transmitted diseases. One of the most prevalent cancer types induced by HPV (mostly types 16 and 18) is cervical cancer. Vaccination is the most effective means of preventing this infectious disease. These prophylactic vaccines, based on virus-like particles (VLPs), are extremely effective in providing protection from infection in almost 100 % of cases. VLP vaccines of HPV are subunit vaccines consisting only of the major viral capsid protein of HPV. There are two types of vaccine available: bivalent vaccine (against HPV-16/18) and quadrivalent vaccine (against HPV-6/11/16/18). Second-generation prophylactic HPV vaccines, currently in clinical trials, may hold several merits over the current bivalent and quadrivalent vaccines, such as protection against additional oncogenic HPV types, less dependence on cold-chain storage and distribution, and non-invasive methods of delivery.