Immuno-Informatics Design of Multi-Epitope Vaccine Candidate Against Anaplasma phagocytophilum Using Major Surface...

Bovine anaplasmosis is an intracellular tick-borne, non-contagious disease caused by gram-negative bacteria of the family Anaplasmataceae and order Rickettsia. Anaplasma phagocytophilum is the etiological agent for human granulocytic anaplasmosis associated with severe health implications in parts of Europe and the USA and tick-borne fever in a broad host range, including cattle. Major surface protein 4 (MSP-4) is highly conserved and recognized as an essential immunodominant protein on the bacterial membrane, playing a crucial role in host-cell interaction. Despite the pathogenic and zoonotic implications of A. phagocytophilum, effective vaccines have not been developed. The present research aimed to develop multiple epitope-based constructs targeting the pathogen, with the aid of computational immunology tools within a reverse vaccinology framework.

The development and design of a multiepitope vaccine construct targeting the major surface protein-4 (MSP-4) antigen were accomplished using an immunoinformatic approach.

The vaccine design incorporated 10 CD8⁺, 9 CD4⁺, and 2 B-cell epitopes, interlinked through AAK, GPGPG, and KK peptides to facilitate optimal presentation of efficient conformation. The EAAK linker facilitated the precise attachment of the immunostimulant adjuvant to the N-terminal of the subunit vaccine, thereby augmenting its capacity to stimulate and boost the immunogenic efficacy of the vaccine. The construct demonstrated a high antigenicity (0.84), was free from allergenic reactions, exhibited excellent solubility (0.97), structurally stable during binding interactions, and an inducer of important cytokines such as IFN-γ and interleukin 4. The vaccine construct weighs 47.98 kDa, with a calculated aliphatic index score (98.33), overall predicted instability index value (29.94), and a GRAVY value of 0.339, revealing favorable physicochemical properties that suggest its overall stability and hydrophobicity.

The vaccine construct induced sufficient humoral and cellular response during immune simulation. Analysis of the immunogen model further confirmed its potential to stimulate the immune system effectively against bovine A. phagocytophilum infection. However, further validation is required using experimental approaches.