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

Abstract

The immunoprophylactic management of ticks is the most effective option to control tick infestations and counter spread the acaricide resistance problem worldwide. Several researchers reported an inconsistent efficacy of the single antigen-based immunization of hosts against different tick species. In the present study, to develop a multi-target immunization protocol, proteins from Rhipicephalus microplus BM86 and Hyalomma anatolicum subolesin (SUB) and tropomyosin (TPM) were targeted to evaluate the cross-protective potential. The sequence identities of the BM86, SUB, and TPM coding genes amongst Indian tick isolates of targeted species were 95.6–99.8%, 98.7–99.6%, and 98.9–99.9%, respectively, while at the predicted amino acid level, the identities were 93.2 to 99.5, 97.6 to 99.4, and 98.2 to 99.3%. The targeted genes were expressed in the eukaryotic expression system, pKLAC2-Kluyveromyces lactis, and 100 µg each of purified recombinant protein (Bm86-89 kDa, SUB-21 kDa, and TPM-36 kDa) mixed with adjuvant was injected individually through the intramuscular route at different sites of the body on days 0, 30, and 60 to immunize cross-bred cattle. Post-immunization, a statistically significant (p < 0.001) antibody response (IgG, IgG1, and IgG2) in comparison to the control, starting from 15 to 140 days, against each antigen was recorded. Following multi-antigen immunization, the animals were challenged twice with the larvae of R. microplus and H. anatolicum and theadults of H. anatolicum, and a significant vaccine efficacy of 87.2% and 86.2% against H. anatolicum larvae and adults, respectively, and 86.7% against R. microplus was obtained. The current study provides significant support to develop a multi-antigen vaccine against cattle tick species.

Testing Efficacy of a Conserved Polypeptide from the Bm86 Protein against Rhipicephalus microplus in the Mexican Tropics

“…Cattle immunized with the polypeptide Bm86 showed higher anti-pBm86 levels after the first immunization and decreased after the second immunization. However, remained significantly different ( p < 0.05) compared to the control group, which has been commonly found in previous studies with the Bm86 vaccine [ 25 , 32 , 48 , 51 ]. Contrary to the Bm86 antigen results, antibody levels were low in immunized cattle, possibly for different reasons, such as the health condition and the age of the animals used in the experiment [ 40 ].…”

More than Three Decades of Bm86: What We Know and Where to Go

“…Although good protection against an Indian field isolate of R. microplus was shown by Kumar et al [ 79 ], where the recombinant Bm95 antigen from the Argentinean strain A of R. microplus was used (i.e., vaccine efficacy of ~81%). A recent study by Parthasarathi et al [ 92 ] using a multi-antigen vaccine including a full-length Bm86 produced from the Indian IVRI-I strain did, however, produce superior protection of more than 88%. In turn, Blecha et al [ 106 ] conducted in silico prediction of linear T- and B-cell epitopes using both bovine MHC I (via BoLA loci) and mouse MHC I and II (via the H-2 locus) alleles for prediction of antigenic peptide sequences from various global R. microplus geographical strains.…”

“…The Gavac ® Plus vaccine also later demonstrated an 81% efficacy against an unspecified Indian field isolate of R. microplus [ 79 ] ( Table 1 ). A follow-up homologous cattle immunisation and tick challenge study performed in 2023 by Parthasarathi et al [ 92 ] conferred 84.6–88.9% protection from two separate infestations on the same vaccinated animals using Bm86 identified from the IVRI-I Indian R. microplus ( Table 1 ).…”

“…Despite the reported levels of protection conferred within and between tick species ( Table 2 ), no species-specific vaccines or combinatorial vaccines containing the most prevalent (and protective) native Bm86 orthologues have been investigated for commercialization to date. Only one recent study by Parthasarathi et al [ 92 ] demonstrated cross-species protection between Indian IVRI-II strains of R. microplus (84.6% and 88.9% vaccine efficacy) and H. anatolicum (86.2% efficacy against adult infestations) by using a multi-antigen vaccine containing Bm86 derived from the R. microplus strain, as well as Subolesin and tropomyosin isolated from the H. anatolicum strain, respectively. The studies described above highlight the fact that other factors besides sequence homology might be playing a role in Bm86-based vaccine efficacy.…”

Evolution of tick vaccinology

“…This vaccine is now under field trial in Uganda (Kabi et al, 2022). Other personalized SUB vaccines have been evaluated against different Indian tick species (Parthasarathi et al, 2023).…”