Using immunoinformatics and bioinformatics approach to design novel and effective rational in-silico vaccine against human Astrovirus targeting the capsid polyprotein VP90: a silent threat to global gastrointestinal tract.

The human Astrovirus, classified within the family Astroviridae and genus Mammastrovirus, is a significant pathogen predominantly affecting immunocompromised individuals and young children, and it is the causative agent of viral gastroenteritis. Currently, there are no effective antiviral treatments or vaccines in stock for HAstV illness, demonstrating the urgent need for vaccine development against this disease. This study used the Capsid Polyprotein VP90 to predict B-cell, CTL and HTL epitopes using precise Immunoinformatics approach. Non-allergenic and immunogenic epitopes were selected for the formulation of a subunit vaccine. Appropriate linkers, namely KK, GPGPG, and AAY, were employed to connect these epitopes. Immune simulation revealed elevated IgM and IgG titers (> 600,000/ml), accompanied by increased cytokine production (IFN-γ ≈ 430,000/ml; IL-2 ≈ 180,000/ml), demonstrating a strong and balanced humoral and cellular immune response. The antigenicity and immunogenicity examination resulted in antigenicity values of 0.5997 and 0.939735 respectively. The structural model of the vaccine was generated and validated using ProSA, Rampage, and ERRAT servers, yielding a Z-score of - 7.53, an ERRAT value of 97.004, and a Ramachandran plot that demonstrated 93.0% of residues were located within the favored region. Subsequent docking analyses indicated that TLR7 exhibited a strong binding affinity towards the vaccine model, characterized by 219 non-bonding contacts, 4 salt bridges, and 14 hydrogen bonds. The vaccine sequence, reverse-translated for optimal expression, was cloned into the pET28a ( +) vector. To optimize the vaccine developed in this research, further experimental validation is warranted.