Immunogenic potential of Rhipicephalus (Boophilus) microplus aquaporin 1 against Rhipicephalus sanguineus in domestic dogs

Authors: MARTINEZ EVORA, PATRICIA - Sao Paulo State University (UNESP); SANCHES, GUSTAVO - Sao Paulo State University (UNESP); Guerrero, Felicito; Perez De Leon, Adalberto - Beto; BECHARA, GERVASIO - Sao Paulo State University (UNESP)

Submitted to: Revista Brasileira de Parasitologia Veterinaria
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/17/2017
Publication Date: 1/17/2017
Citation: Martinez Evora, P., Sanches, G.S., Guerrero, F., Perez De Leon, A.A., Bechara, G.H. 2017. Immunogenic potential of Rhipicephalus (Boophilus) microplus aquaporin 1 against Rhipicephalus sanguineus in domestic dogs. Revista Brasileira de Parasitologia Veterinaria. 26(1):60-66.

Interpretive Summary: Ticks that are resistant to chemicals used for their control presents a problem to deal with emerging tick-borne diseases that affect animals and humans. The brown dog tick (BDT) transmits diseases that kill animals and humans. Vaccines against the BDT provide an alternative to the dependency on chemicals to control ticks and tick-borne diseases. This study evaluated a candidate vaccine containing as antigen the molecule of the southern cattle fever tick known as aquaporin 1 (RmAQP1) for its ability to elicit a protective immune response against the BDT infesting dogs. Five dogs were vaccinated with the RmAQP1 vaccine, and five were injected with the negative control, three times. Twenty-one days after the last vaccination, animals of both groups were infested with TBD to asses vaccine efficacy by measuring several parameters of tick biology and the antibody response. As compared to non-vaccinated animals, adult female ticks feeding on vaccinated dogs engorged in a shorter period of time, larvae took longer to engorge and showed a reduced body weight, and nymphs had a shorter engorgement period and weighed less. Antibody levels specific to RmAQP1 increased after the second immunization, but decreased rapidly after the third vaccination. This vaccine showed some effects on the BDT. Additional studies are warranted, using a higher concentration of RmAQP1 or in combination with other antigens, to fully evaluate the utility of RmAQP1 to protect dogs from infestation with the BDT and associated diseases.

Technical Abstract: This study evaluated a recombinant aquaporin 1 protein of Rhipicephalus (Boophilus) microplus (RmAQP1) as antigen in a vaccine against R. sanguineus. Five dogs were immunized with RmAQP1 (10 µg) + adjuvant (Montanide) (G1), and five were inoculated with adjuvant only (G2), three times. Twenty-one days after the last immunization, animals of both groups were challenged with R. sanguineus larvae, nymphs and adults, and their biotic potential was compared. Blood samples were collected before each immunization and every 28 days after the last immunization for 10 weeks. Serum antibody titers (IgG) were assessed by ELISA. We observed that: engorgement period of adult females from G1 was 12% shorter than G2; larvae from G1 had 8.7% longer engorgement period than G2 and weighed 7.2% less; nymphs from G1 had 4.5% shorter engorgement period than G2 and weighed 3.6% less; although the antibody titers increased following the second immunization, they rapidly decreased after the third immunization. Results indicated low immunoprotection of RmAQP1 against adult R. sanguineus ticks, and possible efficacy on larvae and nymphs fed on immunized dogs. Further studies should be performed for a full evaluation of the immunoprotection of RmAQP1 against R. sanguineus infestations in dogs.