Immune response variations to Salmonella enterica serovar Typhi recombinant porin proteins in mice

Natural medicine can substitute antibiotics in animal husbandry: protective effects and mechanisms of rosewood essential oil against Salmonella infection

Aniba rosaeodora essential oil (RO) has been traditionally used in natural medicine as a substitute for antibiotics due to its notable antidepressant and antibacterial properties. Salmonella, a prevalent pathogen in foodborne illnesses, presents a major challenge to current antibiotic treatments. However, the antibacterial efficacy and mechanisms of action of RO against Salmonella spp. remain underexplored. This study aims to elucidate the chemical composition of RO, evaluate its antibacterial activity and mechanisms against Salmonella in vitro, and further delineate its anti-inflammatory mechanisms in vivo during Salmonella infection. Gas chromatography-mass spectrometry (GC-MS) was utilized to characterize the chemical constituents of RO. The antibacterial activity of RO was assessed using minimal inhibitory concentration (MIC) and time-kill assays. Various biochemical assays were employed to uncover the potential bactericidal mechanisms. Additionally, mouse and chick models of Salmonella infection were established to investigate the prophylactic effects of RO treatment. RO exhibited significant antibacterial activity against both Gram-positive and Gram-negative bacteria, with an MIC of 4 mg·mL-1 for Salmonella spp. RO treatment resulted in bacterial damage through the disruption of lipid and purine metabolism. Moreover, RO reduced injury and microbial colonization in infected mice and chicks. RO treatment also modulated the host inflammatory response by inhibiting proinflammatory pathways. In conclusion, our findings demonstrate that RO is effective against Salmonella infection, highlighting its potential as an alternative to antibiotics for antibacterial therapy.

Dual immunization with CdtB protein and flagellin epitope offers augmented protection against enteric fever in mice

AIMS

Present study has explored the protective response of dual immunization using two different antigenic entities (i.e. flagellin epitope and cytolethal distending toxin subunit B (CdtB) protein) against lethal challenge of typhoidal serovars in a murine model.

MAIN METHODS

In-vitro immunogenicity of flagellin epitope-BSA conjugate and CdtB protein was confirmed using Indirect ELISA of typhoid positive patients' sera. Further, both entities were administered intraperitoneally in mice individually or in combination, followed by lethal challenge of typhoidal Salmonellae. Various parameters were analysed such as bacterial burden, mice survival, histopathological analysis, cytokine analysis and immunophenotyping. Serum samples obtained from the immunized mice were used for passive immunization studies, wherein mice survival and mechanism of action of the generated antibodies was studied.

KEY FINDINGS

Active immunization studies using the combination of both entities demonstrated improved mice survival after lethal challenge with typhoidal Salmonellae, reduced bacterial burden in organs, expression of immunophenotypic markers in splenocytes and restored tissue histoarchitecture. When used in combination, the effective doses of both the candidates reduced which may be attributed to multiprong approach used by the immune system to recognize Salmonella. Passive immunization studies further determined the protective efficacy of generated antibodies by different mechanisms such as complement mediated bactericidal action, swarming inhibition and increased phagocytic uptake.

SIGNIFICANCE

Present study is the first phase of the proof-of-concept which may prove to be beneficial in developing an effective bi-functional vaccine candidate to render protection against both Vi-positive as well as Vi-negative Salmonella strains.

Identification of Subunits for Novel Universal Vaccines against Three Predominant Serogroups and the Emerging O145 among Avian Pathogenic Escherichia coli by Pan-RV Pipeline

Avian pathogenic Escherichia coli, a causative agent of avian colibacillosis, has been causing serious economic losses in the poultry industry. The increase in multidrug-resistant isolates and the complexity of the serotypes of this pathogen, especially the recently reported emergence of a newly predominant serogroup of O145, make the control of this disease difficult. To address this challenge, a high-throughput screening approach, called Pan-RV (Reverse vaccinology based on pangenome analysis), is proposed to search for universal protective antigens against the three traditional serogroups and the newly emerged O145. Using this approach, a total of 61 proteins regarded as probable antigens against the four important serogroups were screened from the core genome of 127 Avian pathogenic Escherichia coli (APEC) genomes, and six were verified by Western blots using antisera. Overall, our research will provide a foundation for the development of an APEC subunit vaccine against avian colibacillosis. Given the exponential growth of whole-genome sequencing (WGS) data, our Pan-RV pipeline will make screening of bacterial vaccine candidates inexpensive, rapid, and efficient. IMPORTANCE With the emergence of drug resistance and the newly predominant serogroup O145, the control of Avian pathogenic Escherichia coli is facing a serious challenge; an efficient immunological method is urgently needed. Here, for the first time, we propose a high-throughput screening approach to search for universal protective antigens against the three traditional serogroups and the newly emerged O145. Importantly, using this approach, a total of 61 proteins regarded as probable antigens against the four important serogroups were screened, and three were shown to be immunoreactive with all antisera (covering the four serogroups), thereby providing a foundation for the development of APEC subunit vaccines against avian colibacillosis. Further, our Pan-RV pipeline will provide immunological control strategies for pathogens with complex and variable genetic backgrounds such as Escherichia coli and will make screening of bacterial vaccine candidates more inexpensive, rapid, and efficient.

Specific egg yolk immunoglobulin as a promising non-antibiotic biotherapeutic product against Acinetobacter baumannii pneumonia infection

Acinetobacter baumannii is a serious health threat with a high mortality rate. We have already reported prophylactic effects of IgYs raised against OmpA and Omp34 as well as against inactivated whole-cell (IWC) of A. baumannii in a murine pneumonia model. However, the infection was exacerbated in the mice group that received IgYs raised against the combination of OmpA and Omp34. The current study was conducted to propose reasons for the observed antibody-dependent enhancement (ADE) in addition to the therapeutic effect of specific IgYs in the murine pneumonia model. This phenomenon was hypothetically attributed to topologically inaccessible similar epitopes of OmpA and Omp34 sharing similarity with peptides of mice proteins. In silico analyses revealed that some inaccessible peptides of OmpA shared similarity with peptides of Omp34 and Mus musculus. Specific anti-OmpA and anti-Omp34 IgYs cross-reacted with Omp34 and OmpA respectively. Specific IgYs showed different protectivity against A. baumannii AbI101 in the murine pneumonia model. IgYs triggered against OmpA or IWC of A. baumannii were the most protective antibodies. IgY triggered against Omp34 is ranked next after those against OmpA. The lowest protection was observed in mice received IgYs raised against the combination of rOmpA and rOmp34. In conclusion, specific IgYs against OmpA, Omp34, and IWC of A. baumannii could serve as novel biotherapeutics against A. baumannii pneumonia.

rOmpF and OMVs as efficient subunit vaccines against Salmonella enterica serovar Enteritidis infections in poultry farms

Salmonella enterica serovar Enteritidis remains the most prevalent serotype causing human salmonellosis through the consumption of contaminated foods, especially poultry products. The development of a subunit vaccine against S. Enteritidis can not only protect chickens against Salmonella infection in the poultry industry but also cut the transmission sources. In this study, both the expressed recombinant outer membrane protein F (rOmpF) and extracted outer membrane vesicles (OMVs) were developed as subunit vaccines against S. Enteritidis challenge in chickens. Immunization with the subunit vaccine could induce not only antibody production but also strong cell-mediated immune response. Both rOmpF plus QuilA adjuvant and OMVs alone had highly protective efficacy against S. Enteritidis challenge and rapidly decreased the colonization of bacteria in chicken. These findings revealed the potential application of rOmpF and OMVs as subunit vaccines in the poultry industry.

Expression and purification of an immunogenic SUMO-OmpC fusion protein of Salmonella Typhimurium in Escherichia coli

Salmonella is found to be a major causes of food borne diseases globally. Poultry products contaminated with this pathogen is one of the major sources of infections in humans. Outer membrane protein C (OmpC) of Salmonella Typhimurium is a promising DNA vaccine candidate to mitigate Salmonella infection in poultry. However, the large-scale production of bioactive recombinant OmpC (rOmpC) protein is hindered due to the formation of inclusion bodies in Escherichia coli. The objective of this work was to attain high level expression of rOmpC protein, purify and evaluate its functional properties. The ompC gene was optimized and fused with small ubiquitin-related modifier (SUMO) gene for high level expression as soluble protein. The fusion protein with ~58 kDa molecular weight was observed on SDS-PAGE gel. The expression levels of rOmpC fusion protein reached maximum of 38% of total soluble protein (TSP) after 8 h of 0.2% rhamnose induction. Protein purification was carried out using nickel nitrilotriacetic acid (Ni-NTA) purification column. Western blot were performed to analyse expression and immunoreactivity of rOmpC fusion protein. The results indicate that SUMO fusion system is ideal for large scale production of functional rOmpC fusion protein expression in E. coli.

Exploitation of two siderophore receptors, BauA and BfnH, for protection against Acinetobacter baumannii infection

Iron uptake system is expressed in early stages of Acinetobacter baumannii infections under iron-restricted conditions. This study is aimed at the evaluation of immuno-protectivity of BfnH in comparison with BauA in both mature and selected fragmental proteins. The study was designed in single and combined forms of antigens. BfnH is presented in 3472 strains of A. baumannii with more than 97% identity. The preliminary immune-informatics analysis of this protein indicated a region from the β-barrel domain including exposed loops 2-5, with antigenic score comparable to that of BfnH. There was a significant rise in the specific IgG response in all test groups. The bacterial challenge with a lethal dose of A. baumannii demonstrated partial protection of whole proteins which coincides with a significant reduction in the bacterial population colonized in the main organs and an increase in the survival level. Passive immunization of the mice brought about 50% survival in the mice groups immunized with BfnH and with a combination of BfnH and BauA. The protectivity of siderophore receptors suggests their potential immunogenic role that could be considered as a component of multivalent subunit vaccine candidates against A. baumannii.

Specific egg yolk antibodies (IgY) confer protection against Acinetobacter baumannii in a murine pneumonia model

AIM

Acinetobacter baumannii, an increasingly serious health threat, is considered as one of the six most dangerous microbes of high mortality rate. However, treatment of its infections is difficult because of the lack of efficient antibiotic or commercial vaccines. Passive immunization through administration of specific antibodies such as IgY, could be an attractive practical solution.

METHODS AND RESULTS

In the current study, antigenicity of two recombinant outer membrane proteins (OmpA and Omp34) as well as inactivated whole cell of A. baumannii was assessed by ELISA. Moreover, prophylactic effects of specific IgY antibodies (avian antibody) raised against these antigens were evaluated in a murine pneumonia model. The specific IgY antibodies had various prophylactic effects in the pneumonia model. OmpA was the most potent antigen in terms of triggering antibody and conferring protection. While a synergic effect was observed in ELISA for antibodies raised against a combination of OmpA and Omp34 (which are known as Omp33-36 and Omp34 kDa), an antagonistic effect was unexpectedly seen in challenges. The reason for this phenomenon remains to be precisely addressed.

CONCLUSION

All the specific IgY antibodies could protect mice against pneumonia caused by A. baumannii.

SIGNIFICANCE AND IMPACT OF THE STUDY

The specific IgY antibodies could be employed as a pharmaceutical against pneumonia caused by A. baumannii.

Mucosal and systemic responses of immunogenic vaccines candidates against enteric Escherichia coli infections in ruminants: A review

Innumerable Escherichia coli of animal origin are identified, which are of economic significance, likewise, cattle, sheep and goats are the carrier of enterohaemorrhagic E. coli, which are less pathogenic, and can spread to people by way of direct contact and through the contamination of foodstuff or portable drinking water, causing serious illness. The immunization of ruminants has been carried out for ages and is largely acknowledged as the most economical and maintainable process of monitoring E. coli infection in ruminants. Yet, only a limited number of E. coli vaccines are obtainable. Mucosal surfaces are the most important ingress for E. coli and thus mucosal immune responses function as the primary means of fortification. Largely contemporary vaccination processes are done by parenteral administration and merely limited number of E. coli vaccines are inoculated via mucosal itinerary, due to its decreased efficacy. Nevertheless, aiming at maximal mucosal partitions to stimulate defensive immunity at both mucosal compartments and systemic site epitomises a prodigious task. Enormous determinations are involved in order to improve on novel mucosal E. coli vaccines candidate by choosing apposite antigens with potent immunogenicity, manipulating novel mucosal itineraries of inoculation and choosing immune-inducing adjuvants. The target of E. coli mucosal vaccines is to stimulate a comprehensive, effective and defensive immunity by specifically counteracting the antibodies at mucosal linings and by the stimulation of cellular immunity. Furthermore, effective E. coli mucosal vaccine would make vaccination measures stress-free and appropriate for large number of inoculation. On account of contemporary advancement in proteomics, metagenomics, metabolomics and transcriptomics research, a comprehensive appraisal of the immeasurable genes and proteins that were divulged by a bacterium is now in easy reach. Moreover, there exist marvellous prospects in this bourgeoning technologies in comprehending the host bacteria affiliation. Accordingly, the flourishing knowledge could massively guarantee to the progression of immunogenic vaccines against E. coli infections in both humans and animals. This review highlight and expounds on the current prominence of mucosal and systemic immunogenic vaccines for the prevention of E. coli infections in ruminants.

Escherichia coli outer membrane protein F (OmpF): an immunogenic protein induces cross-reactive antibodies against Escherichia coli and Shigella

Diarrhea caused by pathogenic Escherichia coli (E. coli) is one of the most serious infectious diseases in humans and animals. Due to antibiotics resistance and the lack of efficient vaccine, more attention should be paid to find potential versatile vaccine candidates to prevent diseases. In this study, the sequence homology analysis indicated that OmpF from E. coli CVCC 1515 shares a high identity (90−100%) with about half of the E. coli (46.7%) and Shigella (52.8%) strains. Then the recombinant OmpF was supposed to be developed as a versatile vaccine to prevent E. coli infection. OmpF was expressed in E. coli BL21 (DE3) using the auto-induction method. The recombinant OmpF (rOmpF) protein had an average molecular weight of 40 kDa with the purity of 90%. Immunological analysis indicated that the titers of anti-rOmpF sera against rOmpF and whole cells were 1:240,000 and 1:27,000, respectively. The opsonophagocytosis result showed that 72.21 ± 11.39 and 11.04 ± 3.90% of bacteria were killed in the rOmpF immunization and control groups, respectively. The survival ratio of mice immunized with rOmpF ranged between 40 and 60% as observed within 36 h after challenge, indicating mice were partially protected from E. coli CVCC 1515 infection. The expressed rOmpF protein induced an effective immune response, but only provide a weak protection against pathogenic E. coli CVCC 1515 and a small reduction in E. coli CICC 21530 (O157:H7) excretion in a mouse infection model. Native forms of the OmpF antigen may be studied for immunogenicity and potential protective efficacy.

The Proteome of Biologically Active Membrane Vesicles from Piscirickettsia salmonis LF-89 Type Strain Identifies Plasmid-Encoded Putative Toxins

Piscirickettsia salmonis is the predominant bacterial pathogen affecting the Chilean salmonid industry. This bacterium is the etiological agent of piscirickettsiosis, a significant fish disease. Membrane vesicles (MVs) released by P. salmonis deliver several virulence factors to host cells. To improve on existing knowledge for the pathogenicity-associated functions of P. salmonis MVs, we studied the proteome of purified MVs from the P. salmonis LF-89 type strain using multidimensional protein identification technology. Initially, the cytotoxicity of different MV concentration purified from P. salmonis LF-89 was confirmed in an in vivo adult zebrafish infection model. The cumulative mortality of zebrafish injected with MVs showed a dose-dependent pattern. Analyses identified 452 proteins of different subcellular origins; most of them were associated with the cytoplasmic compartment and were mainly related to key functions for pathogen survival. Interestingly, previously unidentified putative virulence-related proteins were identified in P. salmonis MVs, such as outer membrane porin F and hemolysin. Additionally, five amino acid sequences corresponding to the Bordetella pertussis toxin subunit 1 and two amino acid sequences corresponding to the heat-labile enterotoxin alpha chain of Escherichia coli were located in the P. salmonis MV proteome. Curiously, these putative toxins were located in a plasmid region of P. salmonis LF-89. Based on the identified proteins, we propose that the protein composition of P. salmonis LF-89 MVs could reflect total protein characteristics of this P. salmonis type strain.

Vaccination with Salmonella Typhi recombinant outer membrane protein 28 induces humoral but non-protective immune response in rabbit

Aim:

Typhoid is one of the most important food and water borne disease causing millions of deaths over the world. Presently, there is no cost effective vaccine available in India. The outer-membrane proteins (Omps) of Salmonella have been exhibited as a potential candidate for development of subunit vaccine against typhoid. The objective of the present study was to evaluate the use of recombinant Omp 28 protein for immunization of rabbit to elucidate its protection against virulent Salmonella Typhi.

Materials and Methods:

Immune potential of recombinant Omp28 was tested in New Zealand Rabbits. Rabbits were divided into two groups, i.e., control and test group. Control group was injected with phosphate buffer saline with adjuvant while test group were injected with recombinant Omp28 along with adjuvant. Rabbits were bleed and serum was collected from each rabbit. Serum was tested by Enzyme-linked immunosorbent assay (ELISA) for humoral response. Rabbits were challenged with virulent culture to test the protective immunity.

Results:

Humoral response was provoked at 15^th day and maintained till 30^th day. The mean ELISA titer at 15^th day was 1 : 28000 (mean titer log 10 : 4.4472) and on the 30^th day was 1 : 25866 (mean titer log 10 : 4.4127). Protective immune potential of Omp 28 was assessed by challenge studies in rabbits for which vaccinated and control rabbits were challenged with 10⁹ cells of virulent culture of S. Typhi. In control group, out of six, no rabbit could survive after 48 days while in vaccinated group, three out of six rabbit were survived.

Conclusion:

Immunization of rabbit with recombinant Omp 28 induced a strong humoral response which was exhibited by high antibody titer in ELISA. Subsequently, intraperitoneal homologous challenge of the immunized New Zealand rabbit resulted in lack of significant protection. These findings indicate that Omp 28 though provoked the humoral immunity but could not provide the protective immunity in rabbit model.

In silico identification of vaccine candidates against Klebsiella oxytoca

Klebsiella oxytoca causes several diseases in immunocompromised as well as healthy individuals. Increasing resistance to a number of antibiotics makes treatment options limited. Prevention using vaccine could be an important solution to get rid of infections caused by Klebsiella oxytoca. In recent time, genome based approaches have contributed significantly in vaccine development. Our aim was to identify the most conserved and immunogenic antigens that can be considered as potential vaccine candidates. KEGG database was used to find out pathways unique to the bacteria. Subcellular localization of the protein sequences taken from the selected 36 pathways were predicted using PSORTb v3.0.2 and CELLO v2.5. Prediction of B cell epitope and the probability of the antigenicity were evaluated by using IEDB and Vaxijen respectively. BLASTp was done to find out the similarity of the selected proteins with the human proteome. Proteins failing to comply with the set parameters were filtered at each step. Finally, we identified 6 surface exposed proteins as potential vaccine candidates against Klebsiella oxytoca.

Reversible synthesis of colanic acid and O-antigen polysaccharides in Salmonella Typhimurium enhances induction of cross-immune responses and provides protection against heterologous Salmonella challenge

Colanic Acid (CA) and lipopolysaccharide (LPS) are two major mannose-containing extracellular polysaccharides of Salmonella. Their presence on the bacterial surface can mask conserved protective outer membrane proteins (OMPs) from the host immune system. The mannose moiety in these molecules is derived from GDP-mannose, which is synthesized in several steps. The first two steps require the action of phosphomannose isomerase, encoded by pmi (manA), followed by phosphomannomutase, encoded by manB. There are two copies of manB present in the Salmonella chromosome, one located in the cps gene cluster (cpsG) responsible for CA synthesis, and the other in the rfb gene cluster (rfbK) involved in LPS O-antigen synthesis. In this study, it was demonstrated that the products of cpsG and rfbK are isozymes. To evaluate the impact of these genes on O-antigen synthesis, virulence and immunogenicity, single mutations (Δpmi, ΔrfbK or ΔcpsG) and a double mutation (ΔrfbK ΔcpsG) were introduced into both wild-type Salmonella enterica and an attenuated Δcya Δcrp vaccine strain. The Δpmi, ΔrfbK and ΔcpsG ΔrfbK mutants were defective in LPS synthesis and attenuated for virulence. In orally inoculated mice, strain S122 (Δcrp Δcya ΔcpsG ΔrfbK) and its parent S738 (Δcrp Δcya) were both avirulent and colonized internal tissues. Strain S122 elicited higher levels of anti-S. Typhimurium OMP serum IgG than its parent strain. Mice immunized with S122 were completely protected against challenge with wild-type virulent S. Typhimurium and partially protected against challenge with either wild-type virulent S. Choleraesuis or S. Enteritidis. These data indicate that deletions in rfbK and cpsG are useful mutations for inclusion in future attenuated Salmonella vaccine strains to induce cross-protective immunity.

In vivo validation of the immunogenicity of recombinant Baumannii Acinetobactin Utilization A protein (rBauA)

Acinetobacter baumannii has become a tremendous challenge to modern healthcare as an antimicrobial resistant. Replication and persistence of A. baumannii within eukaryotes is based on iron acquisition functions including siderophore biosynthesis. Iron transport into the cytosol is mediated by specific membrane receptors which recognize the iron-siderophore complexes. Expression of this acinetobactin mediated Iron uptake system is vital for intracellular growth of A. baumannii. Baumannii acinetobactin utilization (BauA), is an outer membrane protein, acting out the siderophore-ferric complex receptor. This study was aimed at analysis of immunogenicity and specificity of BauA. The genomic bauA was amplified via PCR method and after digestion, bauA was ligated into pET28a. The recombinant gene was expressed in Escherichia coli BL21(DE3) and the product was analyzed by SDS-PAGE and purified by Ni-NTA affinity chromatography method. The recombinant BauA (rBauA) was confirmed by western blot analysis using anti-His antibodies and its immunogenicity was assessed by injecting the rBauA to BALB/c mice. Antibodies produced therein could effectively recognize and bind rBauA. The immunized mice challenged with bacterial doses higher than LD50 survived. The antibodies were highly specific to A. baumannii and its clinical isolates. Passive immunization using serum raised against BauA protected mice from infection. BauA can be nominated as an immunogen against A. baumannii.

Influence of heat-labile serum components in the presence of OmpA on the outer membrane of Salmonella gallinarum

Salmonella gallinarum is the causative agent of fowl typhoid. Being a Gram-negative bacteria, its outer membrane proteins (OMP) can be regulated by different microenvironments. S. gallinarum was cultured under the following conditions: nutrient broth (NB), NB supplemented with serum from specific pathogen-free birds (NBS) and NB with serum incubated at 56 °C prior to incubation with the bacteria (NBSD); OMP were subsequently extracted. Several changes were observed in the apparent expression of OMP, mainly a decrease in an OMP with a size of 30 kDa, approximately, under the NBS condition. In contrast, the same event was not observed in NB and NBSD when using one- and two-dimensional polyacrylamide gels (SDS-PAGE). Using the OMP with a size of 30 kDa, approximately, as antigen in indirect ELISA, we were able to differentiate serum from healthy and vaccinated birds, as well as birds infected with S. gallinarum and S. enteritidis. The amino-terminal of this protein was sequenced, showing 100 % identity with OmpA of S. typhimurium. Subsequently, we designed primers to amplify the gene by PCR. The partial sequence of the amplified gene showed 100 % identity with OmpA of S. gallinarum. (1) Heat-labile serum components influence the presence of OmpA in the OM of S. gallinarum; (2) by the way of ELISA, OmpA allows to specifically differentiate healthy from diseased birds.

Evaluation of recombinant outer membrane protein C based indirect enzyme-linked immunoassay for the detection of Salmonella antibodies in poultry

Aim:

To evaluate the efficacy of recombinant outer membrane proteinC (rOmpC) based enzyme-linked immunoassay (ELISA) for the diagnosis of salmonellosis in poultry.

Materials and Methods:

Three antigens were prepared, and the indirect ELISA was standardized using the antigens and the antiserum raised in chicken against Omp and rOmpC. Sera were collected from a total of 255 apparently healthy field chickens and screened for the presence of Salmonella antibodies by this ELISA.

Results:

The sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of Omp revealed major polypeptides at 36, 42 and 52 kDa, and the rOmpC was evident by a single protein band of 43 kDa. The Omp and rOmpC antigen revealed an optimum concentration of 78 and 156 ng, respectively, in the assay, while the whole cell antigen gave an optimum reaction at a concentration of 10⁶ organisms/ml. The test was found to be specific as it did not react with any of the antisera of seven other organisms. The developed ELISA detected Salmonella antibodies from 22 (8.62%) samples with rOmpC antigen, while 24 (9.41%) samples gave a positive reaction with both Omp and whole cell antigens.

Conclusion:

We suggest rOmpC based indirect ELISA as a suitable screening tool for serological monitoring of poultry flocks.

Immune efficacy of five novel recombinant Bordetella bronchiseptica proteins

Background

The Gram-negative pathogen Bordetella bronchiseptica causes acute and chronic respiratory infection in a variety of animals. Currently, there is no vaccine to prevent these infections. To identify useful candidate antigens for such a vaccine, five B. bronchiseptica genes including amino acid ATP-binding cassette transporter substrate-binding protein (ABC), lipoprotein (PL), outer membrane porin protein (PPP), leu/ile/val-binding protein (BPP), and conserved hypothetical protein (CHP) were cloned and the recombinant proteins were expressed. The immune responses of mice to vaccination with individual recombinant proteins were measured.

Results

Each of the tested recombinant proteins induced a high antibody titer. PPP and PL showed protective indices against challenges with B. bronchiseptica. The protection ratios were 62.5 and 50 %, respectively, compared with 12.5 % for control vaccinations. The protection ratios of ABC, BPP, and CHP were not significantly different from the controls. IgG-subtype and cytokine analysis demonstrated that PPP and PL can induce two immune responses: a humoral immune response and a cell-mediated immune response. The humoral immunity-mediated, Th2-type response dominated.

Conclusion

The identification of PPP and PL, which offer immune-protective potential, identifies them as candidates for the development of a diagnostic test or a vaccine for B. bronchiseptica.

Colorimetric biosensing of targeted gene sequence using dual nanoparticle platforms

We have developed a colorimetric biosensor using a dual platform of gold nanoparticles and graphene oxide sheets for the detection of Salmonella enterica. The presence of the invA gene in S. enterica causes a change in color of the biosensor from its original pinkish-red to a light purplish solution. This occurs through the aggregation of the primary gold nanoparticles–conjugated DNA probe onto the surface of the secondary graphene oxide–conjugated DNA probe through DNA hybridization with the targeted DNA sequence. Spectrophotometry analysis showed a shift in wavelength from 525 nm to 600 nm with 1 μM of DNA target. Specificity testing revealed that the biosensor was able to detect various serovars of the S. enterica while no color change was observed with the other bacterial species. Sensitivity testing revealed the limit of detection was at 1 nM of DNA target. This proves the effectiveness of the biosensor in the detection of S. enterica through DNA hybridization.

Computational vaccinology and epitope vaccine design by immunoinformatics

Human immune system includes variety of different cells and molecules correlating with other body systems. These instances complicate the analysis of the system; particularly in postgenomic era by introducing more amount of data, the complexity is increased and necessity of using computational approaches to process and interpret them is more tangible.Immunoinformatics as a subset of bioinformatics is a new approach with variety of tools and databases that facilitate analysis of enormous amount of immunologic data obtained from experimental researches. In addition to directing the insight regarding experiment selections, it helps new thesis design which was not feasible with conventional methods due to the complexity of data. Considering this features immunoinformatics appears to be one of the fields that accelerate the immunological research progression.In this study we discuss advances in genomics and vaccine design and their relevance to the development of effective vaccines furthermore several division of this field and available tools in each item are introduced.

Identification and validation of T-cell epitopes in outer membrane protein (OMP) of Salmonella typhi

This study aims to design epitope-based peptides for the utility of vaccine development by targeting outer membrane protein F (Omp F), because two available licensed vaccines, live oral Ty21a and injectable polysaccharide, are 50% to 80% protective with a higher rate of side effects. Conventional vaccines take longer time for development and have less differentiation power between vaccinated and infected cells. On the other hand, Peptide-based vaccines present few advantages over other vaccines, such as stability of peptide, ease to manufacture, better storage, avoidance of infectious agents during manufacture, and different molecules can be linked with peptides to enhance their immunogenicity. Omp F is highly conserved and facilitates attachment and fusion of Salmonella typhi with host cells. Using various databases and tools, immune parameters of conserved sequences from Omp F of different isolates of Salmonella typhi were tested to predict probable epitopes. Binding analysis of the peptides with MHC molecules, epitopes conservancy, population coverage, and linear B cell epitope prediction were analyzed. Among all those predicted peptides, ESYTDMAPY epitope interacted with six MHC alleles and it shows highest amount of interaction compared to others. The cumulative population coverage for these epitopes as vaccine candidates was approximately 70%. Structural analysis suggested that epitope ESYTDMAPY fitted well into the epitope-binding groove of HLA-C*12:03, as this HLA molecule was common which interact with each and every predicted epitopes. So, this potential epitope may be linked with other molecules to enhance its immunogenicity and used for vaccine development.

Vaccines against invasive Salmonella disease: current status and future directions

Though primarily enteric pathogens, Salmonellae are responsible for a considerable yet under-appreciated global burden of invasive disease. In South and South-East Asia, this manifests as enteric fever caused by serovars Typhi and Paratyphi A. In sub-Saharan Africa, a similar disease burden results from invasive nontyphoidal Salmonellae, principally serovars Typhimurium and Enteritidis. The existing Ty21a live-attenuated and Vi capsular polysaccharide vaccines target S. Typhi and are not effective in young children where the burden of invasive Salmonella disease is highest. After years of lack of investment in new Salmonella vaccines, recent times have seen increased interest in the area led by emerging-market manufacturers, global health vaccine institutes and academic partners. New glycoconjugate vaccines against S. Typhi are becoming available with similar vaccines against other invasive serovars in development. With other new vaccines under investigation, including live-attenuated, protein-based and GMMA vaccines, now is an exciting time for the Salmonella vaccine field.

Salmonella Typhimurium TTSS-2 deficient mig-14 mutant shows attenuation in immunocompromised mice and offers protection against wild-type Salmonella Typhimurium infection

Background

Development of Salmonella enterica serovar Typhimurium (S. Typhimurium) live attenuated vaccine carrier strain to prevent enteric infections has been a subject of intensive study. Several mutants of S. Typhimurium have been proposed as an effective live attenuated vaccine strain. Unfortunately, many such mutant strains failed to successfully complete the clinical trials as they were suboptimal in delivering effective safety and immunogenicity. However, it remained unclear, whether the existing live attenuated S. Typhimurium strains can further be attenuated with improved safety and immune efficacy or not.

Results

We deleted a specific non-SPI (Salmonella Pathogenicity Island) encoded virulence factor mig-14 (an antimicrobial peptide resistant protein) in ssaV deficient S. Typhimurium strain. The ssaV is an important SPI-II gene involved in Salmonella replication in macrophages and its mutant strain is considered as a potential live attenuated strain. However, fatal systemic infection was previously reported in immunocompromised mice like Nos2^−/− and Il-10^−/− when infected with ssaV deficient S. Typhimurium. Here we reported that attenuation of S. Typhimurium ssaV mutant in immunocompromised mice can further be improved by introducing additional deletion of gene mig-14. The ssaV, mig-14 double mutant was as efficient as ssaV mutant, with respect to host colonization and eliciting Salmonella-specific mucosal sIgA and serum IgG response in wild-type C57BL/6 mice. Interestingly, this double mutant did not show any systemic infection in immunocompromised mice.

Conclusions

This study suggests that ssaV, mig-14 double mutant strain can be effectively used as a potential vaccine candidate even in immunocompromised mice. Such attenuated vaccine strain could possibly used for expression of heterologous antigens and thus for development of a polyvalent vaccine strain.

In silico determination and validation of baumannii acinetobactin utilization a structure and ligand binding site

Acinetobacter baumannii is a deadly nosocomial pathogen. Iron is an essential element for the pathogen. Under iron-restricted conditions, the bacterium expresses iron-regulated outer membrane proteins (IROMPs). Baumannii acinetobactin utilization (BauA) is the most important member of IROMPs in A. baumannii. Determination of its tertiary structure could help deduction of its functions and its interactions with ligands. The present study unveils BauA 3D structure via in silico approaches. Apart from ab initio, other rational methods such as homology modeling and threading were invoked to achieve the purpose. For homology modeling, BLAST was run on the sequence in order to find the best template. The template was then served to model the 3D structure. All the models built were evaluated qualitatively. The best model predicted by LOMETS was selected for analyses. Refinement of 3D structure as well as determination of its clefts and ligand binding sites was carried out on the structure. In contrast to the typical trimeric arrangement found in porins, BauA is monomeric. The barrel is formed by 22 antiparallel transmembrane β -strands. There are short periplasmic turns and longer surface-located loops. An N-terminal domain referred to either as the cork, the plug, or the hatch domain occludes the β -barrel.