Bioinformatics Detection of Vaccine Candidate Regions in Molecular Data of Tick Pathogens
Project no. 22196 · Status: Kapanmış · 2020
Summary
Tick-borne pathogens increasingly threaten animal and human health and cause great economic damage. Among these pathogens, babesiosis caused by Babesia caballi species in horses has a mild and chronic clinical manifestation and causes serious health problems and deaths in horses. Although anaplasmosis caused by Anaplasma ovis in sheep has a mild and chronic clinical course, it has been reported by various researchers that it is very common in sheep in Turkey and may be the reason for the decrease in meat and milk yield. Rickettsia aeschlimannii and Rickettsia massiliae species cause Mediterranean spotted fever, a type of rickettsiosis in humans, and this disease shows findings such as necrotic sores, sores on the palms and soles, fever and widespread maculopapular rash in infected humans. Rap-1 protein is a secretory protein that allows the merozoite form of Babesia parasite to enter and invade the host erythrocyte. Msp4 protein is the surface protein that plays a role in the interaction of Anaplasma bacteria with the host, while OmpB protein is the surface protein that plays a role in the adhesion of Rickettsia bacteria to the host cell tissues. It has been reported that all three proteins show antigenic and immunogenic properties in different species of the aforementioned pathogens, as well as contain vaccine candidate and diagnostic epitopes. Although vaccine studies for pathogens are increasing day by day, in this thesis, the production of molecular data of surface and secretory proteins such as Rap-1, Msp4, and OmpB, prediction of vaccine candidate and diagnostic epitopes and design of multi-epitope peptide vaccines using bioinformatics methods with reverse vaccinology and immunoinformatics perspectives were aimed for the pathogens Babesia caballi, Anaplasma ovis, Rickettsia aeschlimannii and Rickettsia massiliae in ticks of Turkey. For this purpose, molecular data of Rap-1 and Msp4 proteins for Babesia caballi and Anaplasma ovis pathogens, respectively, and of C and N terminal regions of OmpB proteins for Rickettsia aeschlimannii and Rickettsia massiliae pathogens was produced for the first time from tick samples (Rhipicephalus sanguineus, Rhipicephalus turanicus, Rhipicephalus bursa, Hyalomma marginatum, Hyalomma anatolicum, Hyalomma aegyptium, and Haemaphysalis erinacei) collected from various host organisms (dog, cat, cattle, goat, sheep, and tortoise) (n :110) in 4 provinces (İzmir, Aydın, Şanlıurfa, and Siirt) of Turkey. The data was compared with the data of world isolates, and potential vaccine candidate and diagnostic epitopes were predicted by bioinformatics methods. Among the identified vaccine candidate epitopes, antigenic, immunogenic and prominent ones in terms of prevalence in isolates were selected and multi-epitope peptide vaccines were designed by linking them with linker sequences. The designed vaccines were tested by molecular docking and immune simulation. In conclusion, Rap-1 and Msp4 proteins for Babesia caballi and Anaplasma ovis, and OmpB protein for Rickettsia aeschlimannii and Rickettsia massiliae were shown to be good vaccine candidate proteins when evaluated in terms of physicochemical, signal peptide, subcellular localization, BetaWrap motif presence, secondary structure, post-translational modifications and conserved epitopes. In addition, it has been demonstrated by molecular docking that the designed vaccines interact with the TLR-2 receptor, which is an innate immune system element that recognizes pathogen-related ligands in parasite and bacterial infections. Immune simulation has shown that vaccines (except for BabeVac 1) also stimulate IgM and IgG antibodies and IFN-g cytokines. This study has the potential to pave the way for the development of multi-epitope peptide vaccines for tick-borne Babesia caballi and Anaplasma ovis pathogens that cause diseases in farm animals and against tick-borne Rickettsia aeschlimannii and Rickettsia massiliae pathogens that cause diseases in humans in the world and Turkey. It is recommended that the predicted epitopes are produced as synthetic peptides in the following serological studies, tested for the capture of antibodies in the sera of farm animals and humans positive for these pathogens, as well as the application of the designed vaccines in animal models.