Candidate Protective Antigens Research Articles

A subunit vaccine encoding glycoprotein holds potential to protect snakehead (Channa argus) from snakehead vesiculovirus infection

Snakehead vesiculovirus (SHVV) is one of the most harmful viral diseases to the snakehead farming industry. Subunit vaccines with highly protective effects strongly depend on the type of vaccine antigen. In order to screen the potential antigen proteins with efficient immunogenicity and reactogenicity, the glycoprotein (G), matrix protein (M), nucleoprotein (N) and phosphoprotein (P) of SHVV were molecular cloned, sequences analyzed and prokaryotic expressed in this study, then four recombinant proteins were served as subunit vaccines to immunize snakehead by intraperitoneal injection to evaluate the immune effects based on the indexes including the serum antibody level, nonspecific enzyme activity, immune-related gene expression and relative percent survivals (RPS). The results showed that compared with control group, the serum antibody levels and T-AOC activities were significantly higher in all four subunit vaccine groups, the serum ACP and AKP activities in four subunit vaccine groups were higher with different degree, and the detected immune-related genes expression levels were remarkably higher in four subunit vaccine groups except IL-8 gene in spleen of rP group. Among four subunit vaccines, rG protein displayed better immune effect than other three proteins. Besides, the RPS of rG group was highest with 83.3%, followed by rM (66.7%), rN (50.0%) and rP (8.3%), respectively. The above results indicated that glycoprotein was a better candidate protective antigen of SHVV and held potential to protect Snakehead from SHVV infection in the type of subunit vaccine.

A Quantum Vaccinomics Approach for the Design and Production of MSP4 Chimeric Antigen for the Control of Anaplasma phagocytophilum Infections.

Anaplasma phagocytophilum Major surface protein 4 (MSP4) plays a role during infection and multiplication in host neutrophils and tick vector cells. Recently, vaccination trials with the A. phagocytophilum antigen MSP4 in sheep showed only partial protection against pathogen infection. However, in rabbits immunized with MSP4, this recombinant antigen was protective. Differences between rabbit and sheep antibody responses are probably associated with the recognition of non-protective epitopes by IgG of immunized lambs. To address this question, we applied quantum vaccinomics to identify and characterize MSP4 protective epitopes by a microarray epitope mapping using sera from vaccinated rabbits and sheep. The identified candidate protective epitopes or immunological quantum were used for the design and production of a chimeric protective antigen. Inhibition assays of A. phagocytophilum infection in human HL60 and Ixodes scapularis tick ISE6 cells evidenced protection by IgG from sheep and rabbits immunized with the chimeric antigen. These results supported that the design of new chimeric candidate protective antigens using quantum vaccinomics to improve the protective capacity of antigens in multiple hosts.

Differentially Represented Proteins in Response to Infection with Mycobacterium tuberculosis Identified by Quantitative Serum Proteomics in Asian Elephants.

Tuberculosis is a major global concern. Tuberculosis in wildlife is a risk for zoonotic transmission and becoming one of the challenges for conservation globally. In elephants, the number of cases is likely rising. The aim of this study was to identify proteins related to tuberculosis infection in elephants, which could then be used for the development of diagnostic tools and/or vaccines. A serum proteomics approach was used to characterize differentially represented proteins in response to Mycobacterium tuberculosis in Asian elephants (Elaphas maximus). Blood samples were collected from eight elephants, four of which were antibody positive for tuberculosis and four were antibody negative. Proteomics analysis identified 26 significantly dysregulated proteins in response to tuberculosis. Of these, 10 (38%) were identified as immunoglobulin and 16 (62%) as non-immunoglobulin proteins. The results provided new information on the antibody response to mycobacterial infection and biomarkers associated with tuberculosis and protective response to mycobacteria in Asian elephants. Protective mechanisms included defense against infection (Alpha-1-B glycoprotein A1BG, Serpin family A member 1 SERPINA1, Transthyretin TTR), neuroprotection (TTR), and reduced risks of inflammation, infections, and cancer (SERPINA1, Keratin 10 KRT10). Using a translational biotechnology approach, the results provided information for the identification of candidate diagnostic, prognostic, and protective antigens for monitoring and control of tuberculosis in Asian elephants.

Using Proteomic Approaches to Unravel the Response of Ctenocephalides felis felis to Blood Feeding and Infection With Bartonella henselae.

Among the Ctenocephalides felis felis-borne pathogens, Bartonella henselae, the main aetiological agent of cat scratch disease (CSD), is of increasing comparative biomedical importance. Despite the importance of B. henselae as an emergent pathogen, prevention of the diseases caused by this agent in cats, dogs and humans mostly relies on the use of ectoparasiticides. A vaccine targeting both flea fitness and pathogen competence is an attractive choice requiring the identification of flea proteins/metabolites with a dual effect. Even though recent developments in vector and pathogen -omics have advanced the understanding of the genetic factors and molecular pathways involved at the tick-pathogen interface, leading to discovery of candidate protective antigens, only a few studies have focused on the interaction between fleas and flea-borne pathogens. Taking into account the period of time needed for B. henselae replication in flea digestive tract, the present study investigated flea-differentially abundant proteins (FDAP) in unfed fleas, fleas fed on uninfected cats, and fleas fed on B. henselae-infected cats at 24 hours and 9 days after the beginning of blood feeding. Proteomics approaches were designed and implemented to interrogate differentially expressed proteins, so as to gain a better understanding of proteomic changes associated with the initial B. henselae transmission period (24 hour timepoint) and a subsequent time point 9 days after blood ingestion and flea infection. As a result, serine proteases, ribosomal proteins, proteasome subunit α-type, juvenile hormone epoxide hydrolase 1, vitellogenin C, allantoinase, phosphoenolpyruvate carboxykinase, succinic semialdehyde dehydrogenase, glycinamide ribotide transformylase, secreted salivary acid phosphatase had high abundance in response of C. felis blood feeding and/or infection by B. henselae. In contrast, high abundance of serpin-1, arginine kinase, ribosomal proteins, peritrophin-like protein, and FS-H/FSI antigen family member 3 was strongly associated with unfed cat fleas. Findings from this study provide insights into proteomic response of cat fleas to B. henselae infected and uninfected blood meal, as well as C. felis response to invading B. henselae over an infection time course, thus helping understand the complex interactions between cat fleas and B. henselae at protein levels.

RNA-seq analysis and gene expression dynamics in the salivary glands of the argasid tick Ornithodoros erraticus along the trophogonic cycle

BackgroundThe argasid tick Ornithodoros erraticus is the main vector of tick-borne human relapsing fever (TBRF) and African swine fever (ASF) in the Mediterranean Basin. Tick salivary proteins secreted to the host at the feeding interface play critical roles for tick feeding and may contribute to host infection by tick-borne pathogens; accordingly, these proteins represent interesting antigen targets for the development of vaccines aimed at the control and prevention of tick infestations and tick-borne diseases.MethodsTo identify these proteins, the transcriptome of the salivary glands of O. erraticus was de novo assembled and the salivary gene expression dynamics assessed throughout the trophogonic cycle using Illumina sequencing. The genes differentially upregulated after feeding were selected and discussed as potential antigen candidates for tick vaccines.ResultsTranscriptome assembly resulted in 22,007 transcripts and 18,961 annotated transcripts, which represent 86.15% of annotation success. Most salivary gene expression took place during the first 7 days after feeding (2088 upregulated transcripts), while only a few genes (122 upregulated transcripts) were differentially expressed from day 7 post-feeding onwards. The protein families more abundantly overrepresented after feeding were lipocalins, acid and basic tail proteins, proteases (particularly metalloproteases), protease inhibitors, secreted phospholipases A2, 5′-nucleotidases/apyrases and heme-binding vitellogenin-like proteins. All of them are functionally related to blood ingestion and regulation of host defensive responses, so they can be interesting candidate protective antigens for vaccines.ConclusionsThe O. erraticus sialotranscriptome contains thousands of protein coding sequences—many of them belonging to large conserved multigene protein families—and shows a complexity and functional redundancy similar to those observed in the sialomes of other argasid and ixodid tick species. This high functional redundancy emphasises the need for developing multiantigenic tick vaccines to reach full protection. This research provides a set of promising candidate antigens for the development of vaccines for the control of O. erraticus infestations and prevention of tick-borne diseases of public and veterinary health relevance, such as TBRF and ASF. Additionally, this transcriptome constitutes a valuable reference database for proteomics studies of the saliva and salivary glands of O. erraticus.Graphical

Eimeria tenella: IMP1 protein delivered by Lactococcus lactis induces immune responses against homologous challenge in chickens

Avian coccidiosis leads to severe economic losses on the global poultry industry. Immune mapped protein-1 (IMP1) is a novel membrane protein, and was reported to be a candidate protective antigen. However, production and utilization modes of IMP1 using Lactococcus lactis as delivery vector were not reported untill now. In the present study, Eimeria tenella IMP1 (EtIMP1) protein was expressed in L. lactis under the nisin-inducible promoter, and EtIMP1 protein was produced in cytoplasmic, cell wall-anchored and secreted forms. Each chicken was orally immunized with one of the three live EtIMP1-expressing lactococci three times at 2 weeks intervals (immunized group), or with live bacteria harboring empty vector (immunized control group). Chickens in immunized and immunized control group were challenged with E. tenella sporulated oocysts to assess the immune responses. The results showed that proliferative responses of peripheral blood T lymphocytes, mRNA expression levels of IL-2, IL-4, IL-10 and IFN-γ in spleen tissues, levels of serum IgG and secretory IgA (sIgA) in cecal lavage fluids from chickens in immunized group were all significantly elevated compared to that in immunized control group. All three the live EtIMP1-expressing lactococci significantly decreased oocyst shedding, alleviated pathological damage in cecum and improved weight gain compared with bacteria harboring empty vector. These results suggested EtIMP1 protein delivered by L. lactis might be a promising candidate in developing novel vaccines against Eimeria infection.

Soil-Transmitted Helminth Vaccines: Are We Getting Closer?

Parasitic helminths infect over one-fourth of the human population resulting in significant morbidity, and in some cases, death in endemic countries. Despite mass drug administration (MDA) to school-aged children and other control measures, helminth infections are spreading into new areas. Thus, there is a strong rationale for developing anthelminthic vaccines as cost-effective, long-term immunological control strategies, which, unlike MDA, are not haunted by the threat of emerging drug-resistant helminths nor limited by reinfection risk. Advances in vaccinology, immunology, and immunomics include the development of new tools that improve the safety, immunogenicity, and efficacy of vaccines; and some of these tools have been used in the development of helminth vaccines. The development of anthelminthic vaccines is fraught with difficulty. Multiple lifecycle stages exist each presenting stage-specific antigens. Further, helminth parasites are notorious for their ability to dampen down and regulate host immunity. One of the first significant challenges in developing any vaccine is identifying suitable candidate protective antigens. This review explores our current knowledge in lead antigen identification and reports on recent pre-clinical and clinical trials in the context of the soil-transmitted helminths Trichuris, the hookworms and Ascaris. Ultimately, a multivalent anthelminthic vaccine could become an essential tool for achieving the medium-to long-term goal of controlling, or even eliminating helminth infections.

Genetic diversity of the ATAQ gene in Rhipicephalus microplus collected in Mexico and implications as anti-tick vaccine.

The cattle tick Rhipicephalus microplus has a large impact on cattle production due to its bloodsucking habit and transmission of pathogens that cause babesiosis and anaplasmosis. Application of acaricides constitutes the major control method but is often accompanied by serious drawbacks, including environmental contamination and an increase in acaricide resistance by ticks. The recent development of anti-tick vaccines has provided positive results in the post-genomic era, owing to the rise of reverse vaccinological and bioinformatics approaches to analyze and identify candidate protective antigens for use against ticks. The ATAQ protein is considered a novel antigen for the control of the cattle tick R. microplus; it is expressed in midguts and Malpighian tubules of all ticks from the Rhipicephalus genus. However, genetic diversity studies are required. Here, the ATAQ gene was sequenced of seven R. microplus tick isolates from different regions in Mexico to understand the genetic diversity. The results showed that sequence identity among the Mexican isolates ranged between 98 and 100% and 97.8–100% at the nucleotide and protein levels, respectively. Alignments of deduced amino acid sequences from different R. microplus ATAQ isolates in Mexico revealed a high degree of conservation. However, the Mexican isolates differed from the R. microplus “Mozambique” strain, at 20 amino acid residues. Finally, the analysis of more R. microplus isolates, and possibly of other Rhipicephalus species, to determine the genetic diversity in the ATAQ locus is essential to suggest this antigen as a vaccine candidate that might control tick infestations.

Vaccination with Ectoparasite Proteins Involved in Midgut Function and Blood Digestion Reduces Salmon Louse Infestations.

Infestation with the salmon louse Lepeophtheirus salmonis (Copepoda, Caligidae) affects Atlantic salmon (Salmo salar L.) production in European aquaculture. Furthermore, high levels of salmon lice in farms significantly increase challenge pressure against wild salmon populations. Currently, available control methods for salmon louse have limitations, and vaccination appears as an attractive, environmentally sound strategy. In this study, we addressed one of the main limitations for vaccine development, the identification of candidate protective antigens. Based on recent advances in tick vaccine research, herein, we targeted the salmon louse midgut function and blood digestion for the identification of candidate target proteins for the control of ectoparasite infestations. The results of this translational approach resulted in the identification and subsequent evaluation of the new candidate protective antigens, putative Toll-like receptor 6 (P30), and potassium chloride, and amino acid transporter (P33). Vaccination with these antigens provided protection in Atlantic salmon by reducing adult female (P33) or chalimus II (P30) sea lice infestations. These results support the development of vaccines for the control of sea lice infestations.

A vaccinology Approach to the Identification and Characterization of Dermanyssus Gallinae Candidate Protective Antigens for the Control of Poultry Red Mite Infestations.

The poultry red mite (PRM), Dermanyssus gallinae, is a hematophagous ectoparasite considered as the major pest in the egg-laying industry. Its pesticide-based control is only partially successful and requires the development of new control interventions such as vaccines. In this study, we follow a vaccinology approach to identify PRM candidate protective antigens. Based on proteomic data from fed and unfed nymph and adult mites, we selected a novel PRM protein, calumenin (Deg-CALU), which is tested as a vaccine candidate on an on-hen trial. Rhipicephalus microplus Subolesin (Rhm-SUB) was chosen as a positive control. Deg-CALU and Rhm-SUB reduced the mite oviposition by 35 and 44%, respectively. These results support Deg-CALU and Rhm-SUB as candidate protective antigens for the PRM control.

In silico selection of functionally important proteins from the mialome of Ornithodoros erraticus ticks and assessment of their protective efficacy as vaccine targets

BackgroundNew candidate protective antigens for tick vaccine development may be identified by selecting and testing antigen candidates that play key biological functions. After blood-feeding, tick midgut overexpresses proteins that play essential functions in tick survival and disease transmission. Herein, Ornithodoros erraticus midgut transcriptomic and proteomic data were examined in order to select functionally significant antigens upregulated after feeding to be tested as vaccine candidate antigens.MethodsTranscripts annotated as chitinases, tetraspanins, ribosomal protein P0 and secreted proteins/peptides were mined from the recently published O. erraticus midgut transcriptome and filtered in a second selection step using criteria based on upregulation after feeding, predicted antigenicity and expression in the midgut proteome. Five theoretical candidate antigens were selected, obtained as recombinant proteins and used to immunise rabbits: one chitinase (CHI), two tetraspanins (TSPs), the ribosomal protein P0 (RPP0) and one secreted protein PK-4 (PK4).ResultsRabbit vaccination with individual recombinant candidates induced strong humoral responses that mainly reduced nymph moulting and female reproduction, providing 30.2% (CHI), 56% (TSPs), 57.5% (RPP0) and 57.8% (PK4) protection to O. erraticus infestations and 19.6% (CHI), 11.1% (TSPs), 0% (RPP0) and 8.1% (PK4) cross-protection to infestations by the African tick Ornithodoros moubata. The joint vaccine efficacy of the candidates was assessed in a second vaccine trial reaching 66.3% protection to O. erraticus and 25.6% cross-protection to O. moubata.ConclusionsThese results (i) indicate that argasid chitinases and RPP0 are promising protective antigens, as has already been demonstrated for ixodid chitinases and RPP0, and could be included in vaccines targeting multiple tick species; (ii) reveal novel protective antigens tetraspanins and secreted protein PK-4, never tested before as protective antigens in ticks; and (iii) demonstrate that multi-antigenic vaccines increased vaccine efficacy compared with individual antigens. Lastly, our data emphasize the value of the tick midgut as a source of protective candidate antigens in argasids for tick control.

Reduction in Oviposition of Poultry Red Mite (Dermanyssus gallinae) in Hens Vaccinated with Recombinant Akirin.

The poultry red mite (PRM), Dermanyssus gallinae, is a hematophagous ectoparasite of birds with worldwide distribution that causes economic losses in the egg-production sector of the poultry industry. Traditional control methods, mainly based on acaricides, have been only partially successful, and new vaccine-based interventions are required for the control of PRM. Vaccination with insect Akirin (AKR) and its homolog in ticks, Subolesin (SUB), have shown protective efficacy for the control of ectoparasite infestations and pathogen infection/transmission. The aim of this study was the identification of the akr gene from D. gallinae (Deg-akr), the production of the recombinant Deg-AKR protein, and evaluation of its efficacy as a vaccine candidate for the control of PRM. The anti-Deg-AKR serum IgY antibodies in hen sera and egg yolk were higher in vaccinated than control animals throughout the experiment. The results demonstrated the efficacy of the vaccination with Deg-AKR for the control of PRM by reducing mite oviposition by 42% following feeding on vaccinated hens. A negative correlation between the levels of serum anti-Deg-AKR IgY and mite oviposition was obtained. These results support Deg-AKR as a candidate protective antigen for the control of PRM population growth.

Function-guided selection of midgut antigens from Ornithodoros erraticus ticks and an evaluation of their protective efficacy in rabbits

The identification of candidate protective antigens for the development of tick vaccines may be approached by selecting antigen candidates that play key biological functions. Tick midgut proteins that play essential functions in tick survival and disease transmission are upregulated in response to blood feeding and digestion. In this study, Ornithodoros erraticus midgut transcriptomic and proteomic data upon feeding were inspected to select functionally relevant antigens to be assessed as vaccine candidate antigens. For this, we primarily focused on proteins with relevant biological functions in key physiological processes for ticks and tick-host-pathogen interactions. Later, we used additional criteria based on overexpression after feeding, predicted antigenicity and cellular localisation, resulting in the selection of four theoretical candidates, two aquaporins (OeAQP, OeAQP1), one ABC transporter (OeABC) and one selenoprotein T (OeSEL). Rabbit vaccination with synthetic immunogenic peptides designed from the extracellular antigenic regions of the selected candidates induced humoral responses that reduced tick feeding and reproduction performance. Both AQPs and OeSEL demonstrated significant protection efficacy against the homologous species O. erraticus, but lower non-significant cross-species protection against Ornithodoros moubata. Conversely, OeABC showed no protection against the homologous species O. erraticus, but significant cross-species protection against O. moubata. These results are the first demonstration of the protective potential of argasid aquaporins, suggesting that they might be included in vaccines for the control of multiple tick species. Additionally, these results also unveiled two novel protective antigens from argasid ticks, OeABC and OeSEL, belonging to functional protein families that have never been explored as a source of vaccine candidates and are deserving of further studies. Finally, our data add value to the midgut as a protective candidate antigen source in argasids for the control of tick infestations.

High throughput discovery and characterization of tick and pathogen vaccine protective antigens using vaccinomics with intelligent Big Data analytic techniques

ABSTRACTIntroduction: The incidence of tick-borne diseases (TBDs) is growing worldwide, and vaccines appear as the most effective and environmentally sound intervention for the prevention and control of TBDs.Areas covered: The vaccinomics approach combines omics technologies and bioinformatics for the characterization of tick-host-pathogen molecular interactions and the development of next-generation vaccines. The two main challenges of the vaccinomics approach are the integration and analysis of omics datasets, and the development of screening platforms for the identification of candidate protective antigens. To address these challenges we propose the application of intelligent Big Data analytic techniques for the high throughput discovery and characterization of tick and pathogen derived candidate vaccine protective antigens.Expert commentary: This innovative approach should improve the development and efficacy of vaccines for the control and prevention of TBDs.

Rhipicephalus bursa Sialotranscriptomic Response to Blood Feeding and Babesia ovis Infection: Identification of Candidate Protective Antigens.

Ticks are among the most prevalent blood-feeding arthropods, and they act as vectors and reservoirs for numerous pathogens. Sialotranscriptomic characterizations of tick responses to blood feeding and pathogen infections can offer new insights into the molecular interplay occurring at the tick-host-pathogen interface. In the present study, we aimed to identify and characterize Rhipicephalus bursa salivary gland (SG) genes that were differentially expressed in response to blood feeding and Babesia ovis infection. Our experimental approach consisted of RNA sequencing of SG from three different tick samples, fed-infected, fed-uninfected, and unfed-uninfected, for characterization and inter-comparison. Overall, 7,272 expressed sequence tags (ESTs) were constructed from unfed-uninfected, 13,819 ESTs from fed-uninfected, and 15,292 ESTs from fed-infected ticks. Two catalogs of transcripts that were differentially expressed in response to blood feeding and B. ovis infection were produced. Four genes coding for a putative vitellogenin-3, lachesin, a glycine rich protein, and a secreted cement protein were selected for RNA interference functional studies. A reduction of 92, 65, and 51% was observed in vitellogenin-3, secreted cement, and lachesin mRNA levels in SG, respectively. The vitellogenin-3 knockdown led to increased tick mortality, with 77% of ticks dying post-infestation. The reduction of the secreted cement protein-mRNA levels resulted in 46% of ticks being incapable of correctly attaching to the host and significantly lower female weights post-feeding in comparison to the control group. The lachesin knockdown resulted in a 70% reduction of the levels associated with B. ovis infection in R. bursa SG and 70% mortality. These results improved our understanding of the role of tick SG genes in Babesia infection/proliferation and tick feeding. Moreover, lachesin, vitellogenin-3, and secreted cement proteins were validated as candidate protective antigens for the development of novel tick and tick-borne disease control measures.

A reverse vaccinology approach to the identification and characterization of Ctenocephalides felis candidate protective antigens for the control of cat flea infestations

BackgroundDespite the abundance of the domestic cat flea, Ctenocephalides felis (Bouché, 1835) and disease risks associated with them, flea control is difficult and requires the development of new control interventions such as vaccines. In this study, a reverse vaccinology approach was designed to achieve a rational selection of cat flea candidate protective antigens.MethodsBased on transcriptomics and proteomics data from unfed adult fleas it was possible to select more specific candidate protective antigens based on highly represented and functionally relevant proteins present in the predicted exoproteome. The protective capacity of the recombinant antigens was evaluated for the control of C. felis infestations in vaccinated cats.ResultsVaccination with recombinant antigens induced an antibody response in immunized cats. Furthermore, a correlation was obtained between the effect of vaccination (antibody levels) and vaccine efficacy on flea phenotype (egg hatchability). The results suggested that the main effect of vaccination with these antigens was on reducing cat flea egg hatchability and fertility, with an overall vaccine efficacy of 32–46%. Although vaccination with these antigens did not have an effect on flea infestations, vaccines affecting reproductive capacity could reduce cat flea populations, particularly under conditions of direct insect transmission between cats.ConclusionsThese results support the development of vaccines with protective antigens affecting flea reproduction and development after feeding on immunized animals for the control of cat flea infestations.

Vaccinomics Approach to the Identification of Candidate Protective Antigens for the Control of Tick Vector Infestations and Anaplasma phagocytophilum Infection.

Anaplasma phagocytophilum is an emerging tick-borne pathogen causing human granulocytic anaplasmosis (HGA), tick-borne fever (TBF) in small ruminants, and other forms of anaplasmosis in different domestic and wild animals. The main vectors of this pathogen are Ixodes tick species, particularly I. scapularis in the United States and I. ricinus in Europe. One of the main limitations for the development of effective vaccines for the prevention and control of A. phagocytophilum infection and transmission is the identification of effective tick protective antigens. The objective of this study was to apply a vaccinomics approach to I. scapularis-A. phagocytophilum interactions for the identification and characterization of candidate tick protective antigens for the control of vector infestations and A. phagocytophilum infection. The vaccinomics pipeline included the use of quantitative transcriptomics and proteomics data from uninfected and A. phagocytophilum-infected I. scapularis ticks for the selection of candidate protective antigens based on the variation in tick mRNA and protein levels in response to infection, their putative biological function, and the effect of antibodies against these proteins on tick cell apoptosis and pathogen infection. The characterization of selected candidate tick protective antigens included the identification and characterization of I. ricinus homologs, functional characterization by different methodologies including RNA interference, immunofluorescence, gene expression profiling, and artificial tick feeding on rabbit antibodies against the recombinant antigens to select the candidates for vaccination trials. The vaccinomics pipeline developed in this study resulted in the identification of two candidate tick protective antigens that could be selected for future vaccination trials. The results showed that I. scapularis lipocalin (ISCW005600) and lectin pathway inhibitor (AAY66632) and I. ricinus homologs constitute candidate protective antigens for the control of vector infestations and A. phagocytophilum infection. Both antigens are involved in the tick evasion of host defense response and pathogen infection and transmission, but targeting different immune response pathways. The vaccinomics pipeline proposed here could be used to continue the identification and characterization of candidate tick protective antigens for the development of effective vaccines for the prevention and control of HGA, TBF, and other forms of anaplasmosis caused by A. phagocytophilum.

Targeting a global health problem: Vaccine design and challenges for the control of tick-borne diseases.

It has been over twenty years since the first vaccines for the control of tick infestations became commercially available. These vaccines proved their efficacy and the potential of this approach for the control of tick-borne diseases (TBDs), which represent a growing burden for human and animal health worldwide. In all these years, research in this area has produced new tick-derived and pathogen-derived candidate protective antigens. However, the potential of vaccines for the control of TBDs has been underestimated due to major challenges to reduce tick infestations, pathogen infection, multiplication and transmission, tick attachment and feeding time and/or host pathogen infection. Nevertheless, vaccines constitute the most safe and effective intervention for the control of TBDs in humans, domestic and wild animals.

Anaplasma phagocytophilum MSP4 and HSP70 Proteins Are Involved in Interactions with Host Cells during Pathogen Infection.

Anaplasma phagocytophilum transmembrane and surface proteins play a role during infection and multiplication in host neutrophils and tick vector cells. Recently, A. phagocytophilum Major surface protein 4 (MSP4) and Heat shock protein 70 (HSP70) were shown to be localized on the bacterial membrane, with a possible role during pathogen infection in ticks. In this study, we hypothesized that A. phagocytophilum MSP4 and HSP70 have similar functions in tick-pathogen and host-pathogen interactions. To address this hypothesis, herein we characterized the role of these bacterial proteins in interaction and infection of vertebrate host cells. The results showed that A. phagocytophilum MSP4 and HSP70 are involved in host-pathogen interactions, with a role for HSP70 during pathogen infection. The analysis of the potential protective capacity of MSP4 and MSP4-HSP70 antigens in immunized sheep showed that MSP4-HSP70 was only partially protective against pathogen infection. This limited protection may be associated with several factors, including the recognition of non-protective epitopes by IgG in immunized lambs. Nevertheless, these antigens may be combined with other candidate protective antigens for the development of vaccines for the control of human and animal granulocytic anaplasmosis. Focusing on the characterization of host protective immune mechanisms and protein-protein interactions at the host-pathogen interface may lead to the discovery and design of new effective protective antigens.

Identification of immune protective genes of Eimeria maxima through cDNA expression library screening

BackgroundEimeria maxima is one of the most prevalent Eimeria species causing avian coccidiosis, and results in huge economic loss to the global poultry industry. Current control strategies, such as anti-coccidial medication and live vaccines have been limited because of their drawbacks. The third generation anticoccidial vaccines including the recombinant vaccines as well as DNA vaccines have been suggested as a promising alternative strategy. To date, only a few protective antigens of E. maxima have been reported. Hence, there is an urgent need to identify novel protective antigens of E. maxima for the development of neotype anticoccidial vaccines.MethodsWith the aim of identifying novel protective genes of E. maxima, a cDNA expression library of E. maxima sporozoites was constructed using Gateway technology. Subsequently, the cDNA expression library was divided into 15 sub-libraries for cDNA expression library immunization (cDELI) using parasite challenged model in chickens. Protective sub-libraries were selected for the next round of screening until individual protective clones were obtained, which were further sequenced and analyzed.ResultsAdopting the Gateway technology, a high-quality entry library was constructed, containing 9.2 × 106 clones with an average inserted fragments length of 1.63 kb. The expression library capacity was 2.32 × 107 colony-forming units (cfu) with an average inserted fragments length of 1.64 Kb. The expression library was screened using parasite challenged model in chickens. The screening yielded 6 immune protective genes including four novel protective genes of EmJS-1, EmRP, EmHP-1 and EmHP-2, and two known protective genes of EmSAG and EmCKRS. EmJS-1 is the selR domain-containing protein of E. maxima whose function is unknown. EmHP-1 and EmHP-2 are the hypothetical proteins of E. maxima. EmRP and EmSAG are rhomboid-like protein and surface antigen glycoproteins of E. maxima respectively, and involved in invasion of the parasite.ConclusionsOur results provide a cDNA expression library for further screening of T cell stimulating or inhibiting antigens of E. maxima. Moreover, our results provide six candidate protective antigens for developing new vaccines against E. maxima.