From Bench to Field: A Guide to Formulating and Evaluating Anti-Tick Vaccines Delving beyond Efficacy to Effectiveness

Abstract

Ticks are ubiquitous blood-sucking ectoparasites capable of transmitting a wide range of pathogens such as bacteria, viruses, protozoa, and fungi to animals and humans. Although the use of chemicals (acaricides) is the predominant method of tick-control, there are increasing incidents of acaricide tick resistance. Furthermore, there are concerns over accumulation of acaricide residues in meat, milk and in the environment. Therefore, alternative methods of tick-control have been proposed, of which anti-tick cattle vaccination is regarded as sustainable and user-friendly. Over the years, tremendous progress has been made in identifying and evaluating novel candidate tick vaccines, yet none of them have reached the global market. Until now, Bm86-based vaccines (Gavac™ in Cuba and TickGARDPLUS™ Australia-ceased in 2010) are still the only globally commercialized anti-tick vaccines. In contrast to Bm86, often, the novel candidate anti-tick vaccines show a lower protection efficacy. Why is this so? In response, herein, the potential bottlenecks to formulating efficacious anti-tick vaccines are examined. Aside from Bm86, the effectiveness of other anti-tick vaccines is rarely assessed. So, how can the researchers assess anti-tick vaccine effectiveness before field application? The approaches that are currently used to determine anti-tick vaccine efficacy are re-examined in this review. In addition, a model is proposed to aid in assessing anti-tick vaccine effectiveness. Finally, based on the principles for the development of general veterinary vaccines, a pipeline is proposed to guide in the development of anti-tick vaccines.

Co-Immunization Efficacy of Recombinant Antigens against Rhipicephalus microplus and Hyalomma anatolicumTick Infestations

“…The immunization efficacy is dependent on many factors, for example, the dose, site of inoculation, adjuvant used, etc. [ 66 , 67 ]. As no separate experiment was conducted to optimize the dose of the Bm86 antigen, the literature was scanned, and the dose of 100 µg was selected [ 68 , 69 , 70 ].…”

The Bm86 Discovery: A Revolution in the Development of Anti-Tick Vaccines

“…These investigations had a “boom” in the first fifteen years of the 21st century, as evidenced by the number of papers and presentations at international conferences addressing the topic [ 74 ]. Notwithstanding promising results obtained in laboratory experiments with diverse antigens against different tick species, none has been tested under field conditions, nor have any been registered as commercial products [ 75 , 76 ]. This fact reflects that the concept demonstration of an effective antigen against ticks is only the first step of a long and costly road to sanitary registration of an anti-tick vaccine, in which there are many involved actors.…”

Tick Vaccines and Concealed versus Exposed Antigens

“…Vaccination with tick “exposed” and “concealed” antigens take advantage on either naturally acquired or artificially induced humoral immune response but more studies are needed to understand specific immunological responses that depend on a wide array of factors such as host species and/or breed, host age, immunocompetence or prior exposure to ticks. To the multifaced host immune response, tick diversity and life cycle particularities make anti tick vaccine development a complex challenge [ 73 , 74 ], but even though the road ahead is long, the Nuttall et al’s article, published in 2006, is an essential read when entering the tick research world.…”