Epitope-Based Vaccines with the Anaplasma marginale MSP1a Functional Motif Induce a Balanced Humoral and Cellular Immune Response in Mice

Abstract

Bovine anaplasmosis is a hemoparasitic disease that causes considerable economic loss to the dairy and beef industries. Cattle immunized with the Anaplasma marginale MSP1 outer membrane protein complex presents a protective humoral immune response; however, its efficacy is variable. Immunodominant epitopes seem to be a key-limiting factor for the adaptive immunity. We have successfully demonstrated that critical motifs of the MSP1a functional epitope are essential for antibody recognition of infected animal sera, but its protective immunity is yet to be tested. We have evaluated two synthetic vaccine formulations against A. marginale, using epitope-based approach in mice. Mice infection with bovine anaplasmosis was demonstrated by qPCR analysis of erythrocytes after 15-day exposure. A proof-of-concept was obtained in this murine model, in which peptides conjugated to bovine serum albumin were used for immunization in three 15-day intervals by intraperitoneal injections before challenging with live bacteria. Blood samples were analyzed for the presence of specific IgG2a and IgG1 antibodies, as well as for the rickettsemia analysis. A panel containing the cytokines’ transcriptional profile for innate and adaptive immune responses was carried out through qPCR. Immunized BALB/c mice challenged with A. marginale presented stable body weight, reduced number of infected erythrocytes, and no mortality; and among control groups mortality rates ranged from 15% to 29%. Additionally, vaccines have significantly induced higher IgG2a than IgG1 response, followed by increased expression of pro-inflammatory cytokines. This is a successful demonstration of epitope-based vaccines, and protection against anaplasmosis may be associated with elicitation of effector functions of humoral and cellular immune responses in murine model.

Theranostic applications of phage display to control leishmaniasis: selection of biomarkers for serodiagnostics, vaccination, and immunotherapy

“…Thus, it has been successfully applied to identify mimotopes used to diagnose malaria (22) (23) , toxoplasmosis (24) (25) , hepatitis A (26) , neurocysticercosis (27) , strongyloidiasis (28) , thyroid cancer (29) , Chagas' disease (30) , and bovine anaplasmosis (31) , and to develop vaccine candidates against cysticercosis (32) , herpes simplex virus infection (33) , cancer (34) , taeniasis (35) , hepatitis B (36) , trichinellosis (37) , Alzheimer's disease (38) , and bovine anaplasmosis (39) . Phage display technology has been also instrumental in the selection of therapeutic agents to treat various cancers such as glioblastoma, melanoma, leukemia, and prostate and thyroid cancers (40) (41) .…”

“…In another study, three peptides expressed in reactive phage clones and selected against serum from leprosy patients were successfully validated as tools for serological diagnosis of leprosy (44) . A similar approach has been applied to develop diagnostics for other animal and human diseases, such as neurocysticercosis (27) , strongyloidiasis (28) , and bovine anaplasmosis (39) . Phage particles carrying antigenic determinants may be directly used for therapy.…”

Anaplasma marginale major surface protein 1a: A marker of strain diversity with implications for control of bovine anaplasmosis

“…Two critical epitopes, STSSQL and SEASTSSQLGA, were identified using phage display technology for identification of immunodominant epitopes recognized by a neutralizing monoclonal antibody against MSP1a (Santos et al, 2012(Santos et al, , 2013. When these epitopes were used as antigen in immunization studies in a mouse model, the number of infected erythrocytes was reduced and mortality was not observed (Santos et al, 2013).…”

“…When these epitopes were used as antigen in immunization studies in a mouse model, the number of infected erythrocytes was reduced and mortality was not observed (Santos et al, 2013). However, details of the MSP1a genotype of the A. marginale strain used in the challenge-exposure were not reported or was the variation of this neutralization sensitive peptide among A. marginale strains.…”

Immune response and biochemistry of calves immunized with rMSP1a ( Anaplasma marginale) using carbon nanotubes as carrier molecules

“…Among them, MSP1a plays an important role in the infection by A. marginale, being associated with the adhesion capacity of rickettsia to the bovine erythrocytes and tick cells (GARCIA-GARCIA et al, 2004), and it has been shown to trigger a protective immune response (BROWN et al, 1998(BROWN et al, , 2001. Recent studies using recombinant MSP1a (rMSP1a) in immunization trials of cattle and laboratory animal models demonstrated an induction of humoral and cellular immune responses associated with an upregulation of pro-inflammatory cytokines (SANTOS et al, 2013;SILVESTRE et al, 2014), suggesting the possibility of its usage in immunization protocols.…”