Cloning, expression and immunological evaluation of a short fragment from Rv3391 of Mycobacterium tuberculosis

Antigenic and conserved peptides from diverse Helicobacter pylori antigens

Since the revolutionary finding of Helicobacter pylori as a common bacterial infection, that a high research effort for its eradication has been conducted. Epitope based-vaccine presents advantages over protein-based, as they can be designed to contain epitopes from diverse proteins, therefore, more easily representing the immune-variability of the bacterial population, while minimizing the toxicity associated to some whole proteins. In the present work, an iterative method, to design antigenic and conserved B-epitopes from diverse virulent factors of H. pylori, was established. The method considered the trade-off between epitopes antigenicity and conservation among the bacterial population. For the method validation, five virulent factors from H. pylori were selected. From each virulent factor, two epitopes were predicted, each with twelve residues of aminoacids. The corresponding ten peptides were synthesised and evaluated by enzyme-linked immunosorbent assay using polyclonal antibodies raised against a specific H. pylori strain. All ten peptides were recognised by the antibodies and were consequently antigenic and conserved. This result could strongly contribute to the design of a multivalent epitope-based vaccine, representing the immunogenetic variability within the bacterial population, leading to a sustained and effective immunogenic protection.

Identification of RD5-encoded Mycobacterium tuberculosis proteins as B-cell antigens used for serodiagnosis of tuberculosis

Comparative genomic studies have identified several Mycobacterium tuberculosis-specific genomic regions of difference (RDs) which are absent in the vaccine strains of Mycobacterium bovis BCG and which may be useful in the specific diagnosis of tuberculosis (TB). In this study, all encoded proteins from DNA segment RD5 of Mycobacterium tuberculosis, that is, Rv3117–Rv3121, were recombined and evaluated by enzyme-linked immunosorbent assays for antibody reactivity with sera from HIV-negative pulmonary TB patients (n = 60) and healthy controls (n = 32). The results identified two immunodominant antigens, that is, Rv3117 and Rv3120, both of which revealed a statistically significant antigenic distinction between healthy controls and TB patients (P < 0.05). In comparison with the well-known early-secreted antigen target 6 kDa (ESAT-6) (sensitivity 21.7%, specificity 90.6%), the higher detection sensitivity and higher specificity were achieved (Rv3117: sensitivity 25%, specificity 96.9%; Rv3120: sensitivity 31.7%, specificity 96.9%). Thus, the results highlight the immunosensitive and immunospecific nature of Rv3117 and Rv3120 and indicate promise for their use in the serodiagnosis of TB.