Immunogenicity of Hypothetical Highly Conserved Proteins as Novel Antigens in Anaplasma marginale

Abstract

Anaplasma marginale is a tick-transmitted Gram-negative intraerythrocytic bacterium and the etiological agent of bovine Anaplasmosis. Even though considerable research efforts have been undertaken, Anaplasmosis vaccine development remains a challenging field. Outer-membrane-specific antigens responsible for the ability of more complex immunogens could have a significant role in the protective response. Thus, the identification of outer-membrane antigens represents a major goal in the development of bacterial vaccines. Considering that 40 % of the annotated proteins in A. marginale remain as hypothetical, we selected three candidate antigens, AM1108, AM127, and AM216 based on experimental evidence, in silico structure prediction of β-barrel outer membrane, and orthology clustering. Sequence alignment and analysis demonstrated a high degree of conservation for the three proteins between the isolates from Argentina compared to the American strains. We confirmed the transcription of the three genes in the intraerythrocytic stage. AM1108 and AM216 recombinant proteins elicited specific T-cell response proliferation and a significant rise in TNF-α and IFN-γ transcript levels, respectively. Only AM1108 was able to be recognized by specific antibodies from infected bovines. This study allowed the identification of new candidate components of the outer-membrane fraction of A. marginale. Further studies will be required to analyze their potential as effective antigens for being included in rational vaccine strategies.

Tick vaccines: current status and future directions

“…Antigens from TBP such as Borrelia burgdorferi [67], flaviviruses [68], Ehrlichia chaffeensis [69], Anaplasma phagocytophilum [69][70][71] and Anaplasma marginale [72][73][74][75][76][77][78] among others have been proposed as candidate protective antigens for the control of pathogen infection and transmission. The possibility of combining these pathogen-derived antigens with tick-protective antigens should result in new vaccines for the control of vectorborne diseases (FIGURE 1).…”

Anaplasma marginale: Diversity, Virulence, and Vaccine Landscape through a Genomics Approach

“…Current research efforts aim at new alternatives for designing vaccines including the use of sequencing technologies and omics approaches [13–17]. …”

Bovine Anaplasmosis: Will there ever be an almighty effective vaccine?

“…Many outer membrane proteins and membrane-associated proteins have been tested as vaccine candidates and are yet to be developed into commercial vaccines. Small genomes of A. marginale comprise ~1,000 genes, with many of them (≥60%) still not described ( 8 , 112 ). This fact should bring hope that other proteins involved in replication or metabolic or signaling pathways may be conserved among strains or may perform vital functions for the parasite survival, providing antigen candidates.…”