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

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.Keywords: Rhipicephalus sanguineus, aquaporin, RmAQP1, immunity, domestic dog, ticks. ResumoEste estudo avaliou a proteína recombinante (aquaporina) do carrapato Rhipicephalus (Boophilus) microplus como antígeno em vacina contra Rhipicephalus sanguineus. Cinco cães foram imunizados com RmAQP1 (10 µg) + adjuvante (G1) e cinco foram inoculados apenas com adjuvante (G2), três vezes. 21 dias após a última imunização todos os animais foram desafiados com larvas, ninfas e adultos de R. sanguineus, e potencial biótico dos carrapatos foi comparado. Amostras de sangue foram coletadas antes de cada imunização e a cada 28 dias após a última imunização, durante 10 semanas. Títulos de anticorpos dos soros dos cães foram avaliados por ELISA. Resultados: o período de ingurgitamento das fêmeas do G1 foi 12% mais curto que o período de ingurgitamento de G2; o período de ingurgitamento das larvas do G1 8,7% foi mais longo e o peso 7,2% menor que no caso de G2; o período de ingurgitamento das ninfas do G1 4,5% foi mais curto e peso 3,6% menor que no caso do G2; aumento dos títulos de anticorpos do G1 após a segunda imunização e declínio após a terceira imunização. Os resultados indicaram baixo potencial de imunoproteção de RmAQP1 contra R. sanguineus adultos, e possível eficácia contra larvas e ninfas, na dose testada. Sugere-se desenvolver novos estudos para melhor avaliação da eficácia de RmAQP1 contra R. sanguineus em cães.Palavras-chave: Rhipicephalus sanguineus, aquaporina, RmAQP1, imunidade, cão doméstico, carrapatos.

Identification of Ixodid Tick-Specific Aquaporin-1 Potential Anti-tick Vaccine Epitopes: An in-silico Analysis

“…The tick AQP1 from this study contained an aspartic acid residue (D) after the second NPA motif which is the signature sequence of Aquaglyceroporin (AQGP) (Figures 7, 10A,B). This finding is in conformity with previous studies which looked at AQP1 proteins from different tick species (Bowman and Sauer, 2004; Guerrero et al, 2014; Évora et al, 2017; Ishibashi et al, 2017). An aspartic acid residue always coexists with a longer loop which increases the pore's permeability to larger molecules such as glycerol (Ishibashi et al, 2011).…”

Vaccination with Ectoparasite Proteins Involved in Midgut Function and Blood Digestion Reduces Salmon Louse Infestations

“…Focusing on functionally relevant biological processes and proteins, such as tick attachment and feeding, proteases and protease inhibitors at the tick-host interface, water balance, blood digestion, heme and iron metabolism, detoxification, mating, vitellogenesis, and fertility, allowed the identification of candidate vaccine tick protective antigens [26,37]. Some of these antigens, such as Aquaporin [37][38][39][40], Ferritin [41][42][43][44], and 64TRP cement protein [45,46], have shown efficacy in vaccine formulations for the control of tick infestations, thus providing support for the potential of this predictive model for the identification of candidate protective antigens. Nevertheless, these experiments were conducted in mammalian animal models, which show differences in the immune response when compared to fish [47].…”

“…Toll-like receptors (TLRs), such as TLR6 (P30), play an important role in the innate and adaptive immune responses to pathogens and are the target of new vaccine adjuvants by using lipopeptides that activate TLR2/6 heterodimers for use in Leishmania vaccines [48]. Potassium chloride and amino acid transporters and other solute carriers involved in cellular hypotonic salinity response and transmembrane transport, such as P33, have been used as candidate protective antigens in vaccine formulations against hard ticks (e.g., Aquaporin; [37][38][39][40]), soft ticks (e.g., ABC transporter; [37] and sulfate/anion exchanger; [49]) ticks and cat flea (e.g., zinc transporter ZIP13 homolog; [25]). Solute carriers, such as human solute carrier family 11 member 1 protein (SLC11A1), have been implicated in the control of bacterial replication and might influence the responses to vaccines with recombinant bacteria in different ways such as regulation of bacterial load or recombinant antigen dose, class II molecule expression, costimulatory or adjuvant activity, or antigen processing [50].…”

Anti‐tick and pathogen transmission blocking vaccines

“…39 A recombinant vaccine using a recombinant epitope of a Rhipicephalus (Boophilus) microplus AQP in cattle elicited immunity that significantly reduced the number of feeding ticks by 68% and 75% in two respective trials, 40 and cross-protective immunity was observed against Rhipicephalus sanguineus in dogs. 41 Vaccination with species-specific and conserved AQP antigens showed efficacy against Ixodes ricinus larvae and Ornitodoros erraticus ticks in rabbits. 42,43 These studies showed reduction in larval and nymphal feeding durations, accompanied by reduction in weight of engorged ticks.…”

“…Silencing of AQP using RNAi showed a 30% reduction of blood volume ingestion in Ixodes ricinus ticks, but did not cause detachment of ticks, 35 and reduced tick fitness with larval lethality in Rhipicephalus ( Boophilus) microplus ticks, with enhanced efficacy in calves infected with Babesia bovis compared to uninfected calves 39 . A recombinant vaccine using a recombinant epitope of a Rhipicephalus (Boophilus) microplus AQP in cattle elicited immunity that significantly reduced the number of feeding ticks by 68% and 75% in two respective trials, 40 and cross‐protective immunity was observed against Rhipicephalus sanguineus in dogs 41 . Vaccination with species‐specific and conserved AQP antigens showed efficacy against Ixodes ricinus larvae and Ornitodoros erraticus ticks in rabbits 42,43 .…”