Abstract
BackgroundThe horn fly, Haematobia irritans irritans, causes significant production losses to the cattle industry. Horn fly control relies on insecticides; however, alternative control methods such as vaccines are needed due to the fly's capacity to quickly develop resistance to insecticides, and the pressure for eco-friendly options.MethodsWe used a reverse vaccinology approach comprising three vaccine prediction and 11 annotation tools to evaluate and rank 79,542 translated open reading frames (ORFs) from the horn fly's transcriptome, and selected 10 transcript ORFs as vaccine candidates for expression in Pichia pastoris. The expression of the 10 selected transcripts and the proteins that they encoded were investigated in adult flies by reverse transcription polymerase chain reaction (RT-PCR) and mass spectrometry, respectively. Then, we evaluated the immunogenicity of a vaccine candidate in an immunization trial and the antigen’s effects on horn fly mortality and fecundity in an in vitro feeding assay.ResultsSix of the ten vaccine candidate antigens were successfully expressed in P. pastoris. RT-PCR confirmed the expression of all six ORFs in adult fly RNA. One of the vaccine candidate antigens, BI-HS009, was expressed in sufficient quantity for immunogenicity and efficacy trials. The IgG titers of animals vaccinated with BI-HS009 plus adjuvant were significantly higher than those of animals vaccinated with buffer plus adjuvant only from days 42 to 112, with a peak on day 56. Progeny of horn flies feeding upon blood from animals vaccinated with BI-HS009 plus adjuvant collected on day 56 had 63% lower pupariation rate and 57% lower adult emergence than the control group (ANOVA: F(1, 6) = 8.221, P = 0.028 and F(1, 6) = 8.299, P = 0.028, respectively).ConclusionsThe reverse vaccinology approach streamlined the discovery process by prioritizing possible vaccine antigen candidates. Through a thoughtful process of selection and in vivo and in vitro evaluations, we were able to identify a promising antigen for an anti-horn fly vaccine.Graphical abstract
Highlights
The horn fly, Haematobia irritans irritans, causes significant production losses to the cattle industry
Vaxign includes a pipeline of software programs (PSORTb [29], TMHMM [30, 31], SPAAN [32], Basic Local Alignment Search Tool (BLAST) [33, 34], Immune Epitope Database (IEDB) [35]) and predicts possible vaccine targets based on antigen subcellular location, adhesion, epitope binding to Major histocompatibility complex (MHC) class I and class II, and little if any sequence similarity to human, mouse, and/or pig proteins (Table 1)
These 420 open reading frames (ORFs) were ranked by VaxiJen analysis scores, and the 100 ORFs with the highest score were selected for manual annotation, described above (Fig. 1, Additional file 4: Dataset S3)
Summary
The horn fly, Haematobia irritans irritans, causes significant production losses to the cattle industry. The horn fly, Haematobia irritans irritans (Diptera: Muscidae) (Linnaeus, 1758), is present in central and southern Europe, Asia Minor, North Africa, and the Americas [1] Large populations of this fly can cause significant blood loss and annoyance in livestock, reducing milk production, weaning weight, and weight gain, resulting in Domingues et al Parasites Vectors (2021) 14:442 economic losses estimated at $876 million (~ $1.7 billion when adjusted for inflation using the Bureau of Labor Statistics calculator [2]) and $2.56 billion per year in the USA [3] and Brazil [4], respectively. Reverse vaccinology has been successfully used for the development of vaccines against viruses [11] and the prokaryote pathogen Neisseria meningitidis serogroup B [12]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
