Infestation of rabbits with just-molted adults of the cattle tick Rhipicephalus microplus: biological parameters and efficiency.

In this study, we report for the first time the successful infestation of rabbits with just-molted, unfed adults of Rhipicephalus microplus. Six New Zealand White rabbits were experimentally infested with 20 female and 20 male unfed adult ticks released into plastic chambers fixed on the shaved backs of each host. The attachment and feeding processes were successful. The biological characteristics of the ticks and the occurrence of adverse events in the tick-attachment area were studied. The average engorgement period was 10.7 days, and 33.3% of the engorged females completed the parasitic phase. The average weight of the recovered engorged females was 149.8 mg, with an average egg mass weight of 70.9 mg, a conversion efficiency index of 47.3%, and a hatching percentage of 88.31%. The adverse reactions found in the tick-attachment area were the usual inflammatory responses of the organism to infestation by these ectoparasites; however, it did not prevent the ticks from feeding and completing their life cycle. These data indicate that the infestation of rabbits with just-molted, unfed adult ticks could be a valuable, alternative animal model for rapid and economical evaluation of vaccine candidates and new molecules with acaricidal activity against Rhipicephalus microplus.

Novel chimeric E2CD154 subunit vaccine is safe and confers long lasting protection against classical swine fever virus.

E2CD154 is a vaccine candidate against classical swine fever (CSF) based on a chimeric protein composed of the E2 glycoprotein fused to porcine CD154 antigen, and formulated in the oil adjuvant Montanide™ ISA 50 V2. This vaccine confers early protection in pigs and prevents vertical transmission in pregnant sows. The objectives of this study were to assess the safety of this immunogen in piglets, to compare several doses of antigen in the formulation, and to study the duration of the immunity provided by this vaccine for up to 9 months. Three trials were conducted by immunizing pigs with a two-dose regime of the vaccine. Challenge experiments were carried out with the highly pathogenic Margarita strain. No local or systemic adverse effects were documented, and neither macroscopic nor microscopic pathological findings were observed in the vaccinated animals. The three antigen doses explored were safe and induced CSF protective neutralizing antibodies. The dose of 50 µg was selected for further development because it provided the best clinical and virological protection. Finally, this protective immunity was sustained for at least 9 months. This study demonstrates that E2CD154 vaccine is safe; defines a vaccine dose of 50 µg antigen, and evidences the capacity of this vaccine to confer long term protection from CSFV infection for up to 9 months post- vaccination. These findings complement previous data on the evaluation of this vaccine candidate, and suggest that E2CD154 is a promising alternative to modified live vaccines in CSF endemic areas.

Immunogenicity of E2CD154 Subunit Vaccine Candidate against Classical Swine Fever in Piglets with Different Levels of Maternally Derived Antibodies.

E2CD154 is a novel subunit vaccine candidate against classical swine fever virus (CSFV). It contains the E2 envelope protein from CSFV fused to the porcine CD154 molecule formulated in the oil adjuvant MontanideTM ISA50 V2. Previous works evidenced the safety and immunogenicity of this candidate. Here, two other important parameters related to vaccine efficacy were assessed. First, the existence of high maternally derived antibody (MDA) titers in piglets born to sows vaccinated with E2CD154 was demonstrated. These MDA titers remained above 1:200 during the first seven weeks of life. To assess whether the titers interfere with active vaccination, 79 piglets from sows immunized with either E2CD154 or a modified live vaccine were vaccinated with E2CD154 following a 0-21-day biphasic schedule. Animals immunized at either 15, 21, or 33 days of age responded to vaccination by eliciting protective neutralizing antibody (NAb) titers higher than 1:600, with a geometric mean of 1:4335, one week after the booster. Those protective levels of NAb were sustained up to six months of age. No vaccination-related adverse effects were described. As a conclusion, E2CD154 is able to induce protective NAb in piglets with different MDA levels and at different days of age.

A chemical conjugate of the tick P0 peptide is efficacious against Amblyomma mixtum.

After Rhipicephalus microplus, the most important tick species affecting livestock industry in Cuba belong to the Amblyomma genus. There are few reports of effective vaccine antigens for these species. Recently, vaccination and challenge trials using a peptide from the P0 acidic ribosomal protein of R. microplus ticks (pP0) as antigen have shown an efficacy around 90% against tick species from the Rhipicephalus genus. Given the high degree of sequence conservation among tick species, pP0 could be an antigen of versatile use in anti-tick vaccine formulations. In this paper, seven rabbits were immunized with a chemical conjugate of pP0 to keyhole limpet haemocyanin. Rabbits were challenged with an average of 1,900 Amblyomma mixtum larvae from a Cuban tick strain. The average number of recovered fed larvae and the viability of larvae in the moulting process were significantly lower in vaccinated animals compared with the control group. The overall vaccine efficacy of the P0 peptide antigen is 54% according to the calculated parameters.