Effect of adjuvants on immune response and protective immunity elicited by recombinant Hsp60 (GroEL) of Salmonella typhi against S. typhi infection

GroEL is an immunodominant surface-exposed antigen of Rickettsia typhi

Rickettsioses are neglected and emerging potentially fatal febrile diseases that are caused by obligate intracellular bacteria, rickettsiae. Rickettsia (R.) typhi and R. prowazekii constitute the typhus group (TG) of rickettsiae and are the causative agents of endemic and epidemic typhus, respectively. We recently generated a monoclonal antibody (BNI52) against R. typhi. Characterization of BNI52 revealed that it specifically recognizes TG rickettsiae but not the members of the spotted fever group (SFG) rickettsiae. We further show that BNI52 binds to protein fragments of ±30 kDa that are exposed on the bacterial surface and also present in the periplasmic space. These protein fragments apparently derive from the cytosolic GroEL protein of R. typhi and are also recognized by antibodies in the sera from patients and infected mice. Furthermore, BNI52 opsonizes the bacteria for the uptake by antigen presenting cells (APC), indicating a contribution of GroEL-specific antibodies to protective immunity. Finally, it is interesting that the GroEL protein belongs to 32 proteins that are differentially downregulated by R. typhi after passage through immunodeficient BALB/c CB17 SCID mice. This could be a hint that the rickettsia GroEL protein may have immunomodulatory properties as shown for the homologous protein from several other bacteria, too. Overall, the results of this study provide evidence that GroEL represents an immunodominant antigen of TG rickettsiae that is recognized by the humoral immune response against these pathogens and that may be interesting as a vaccine candidate. Apart from that, the BNI52 antibody represents a new tool for specific detection of TG rickettsiae in various diagnostic and experimental setups.

Robust immunity induced by multi-epitope DnaK peptides, potential vaccine candidates against Salmonella: An in vitro study

Enteric fever is a common yet serious issue, most troublesome in underdeveloped and developing nations affecting all age group primarily children. Pitfalls of existing vaccines along with rapidly rising Multi-Drug-Resistant Salmonella strains necessitate the need for the development of new vaccine candidates having potential to provide complete protection. Several vaccine strategies are being pursued to stimulate protective immunity against typhoid, including conjugate vaccines for the elicitation of cellular and humoral responses as both arms of immunity are essential for complete protection. Bacterial HSPs are highly immunogenic to produce humoral and cellular immune responses. In this study, we are reporting in vitro immunostimulatory activity of immunodominant multi-epitope protective antigenic DnaK peptides identified earlier by immunoinformatics approach. Remarkable increase in antibody titer, lymphocyte proliferation, cytokines and NO level with individual /mixture of DnaK peptides as compared to control demonstrate immunogenic potential of these peptides that effectively augments both humoral and cellular immune responses. None of the peptides cause any hemolysis in human RBCs. Overall; our findings strongly elucidate the immune-stimulatory potential of DnaK peptides to be explored as potent vaccine candidates against multiple pathogens.

Multi-epitope DnaK peptide vaccine accords protection against lethal S. typhimurium challenge: Elicits both cell mediated immunity and long-lasting serum-neutralizing antibody titers

Typhoid vaccine development has been impeded by inability of currently available vaccines to induce cellular immunity along with neutralizing antibodies against all serovars of S. Typhi and S. Paratyphi. Unfortunately, antibiotic treatment has shown to be an ineffective therapy due to development of resistance against multiple antibiotics. In the present study, we have explored the immunogenicity and protective efficacy of in-silico designed multi-epitope DnaK peptides as candidate vaccine molecules against Salmonella. Immunization studies in mouse typhoid model revealed three of these peptides (DP1, DP5 and DP7) are highly efficacious, stimulating both humoral and cell mediated immunity along with long lasting antibody memory response. There was significant increase in antibody titers (IgG, IgG1, IgG2a, IgA and IgM), lymphocyte proliferative responses and cytokine levels. Immunized groups showed marked reduction in organ bacterial load, fecal shedding and pronounced protection (upto 80%) as compared to unimmunized controls after challenge with S. typhimurium. Our results demonstrate the huge potential of DnaK peptide vaccine candidates (DP1, DP5 and DP7) to accord protective immunity with significant increase in survivability against Salmonella infection in mice, thus commending these molecules as promising agents to tackle typhoid.

Strategy for the enrichment of protein biomarkers from diverse bacterial select agents

BACKGROUND

Some pathogenic bacteria can be potentially used for nefarious applications in the event of bioterrorism or biowarfare. Accurate identification of biological agent from clinical and diverse environmental matrices is of paramount importance for implementation of medical countermeasures and biothreat mitigation.

OBJECTIVE

A novel methodology is reported here for the development of a novel enrichment strategy for the generally conserved abundant bacterial proteins for an accurate downstream species identification using tandem MS analysis in biothreat scenario.

METHODS

Conserved regions in the common bacterial protein markers were analyzed using bioinformatic tools and stitched for a possible generic immuno-capture for an intended downstream MS/MS analysis. Phylogenetic analysis of selected proteins was carried out and synthetic constructs were generated for the expression of conserved stitched regions of 60 kDa chaperonin GroEL. Hyper-immune serum was raised against recombinant synthetic GroEL protein.

RESULTS

The conserved regions of common bacterial proteins were stitched for a possible generic immuno-capture and subsequent specific identification by tandem MS using variable regions of the molecule. Phylogenetic analysis of selected proteins was carried out and synthetic constructs were generated for the expression of conserved stitched regions of GroEL. In a proof-of-concept study, hyper-immune serum raised against recombinant synthetic GroEL protein exhibited reactivity with ~60 KDa proteins from the cell lysates of three bacterial species tested.

CONCLUSION

The envisaged methodology can lead to the development of a novel enrichment strategy for the abundant bacterial proteins from complex environmental matrices for the downstream species identification with increased sensitivity and substantially reduce the time-to-result.

Intranasal Immunization of Mice with Multiepitope Chimeric Vaccine Candidate Based on Conserved Autotransporters SigA, Pic and Sap, Confers Protection against Shigella flexneri

Shigellosis is a diarrheal disease and the World Health Organization prompts the development of a vaccine against Shigella flexneri. The autotransporters SigA, Pic and Sap are conserved among Shigella spp. We previously designed an in silico vaccine with immunodominat epitopes from those autotransporters, and the GroEL protein of S. typhi as an adjuvant. Here, we evaluated the immunogenicity and protective efficacy of the chimeric multiepitope protein, named rMESF, in mice against lethal infection with S. flexneri. rMESF was administered to mice alone through the intranasal (i.n.) route or accompanied with Complete Freund’s adjuvant (CFA) intradermically (i.d.), subcutaneously (s.c.), and intramuscular (i.m.), as well as with Imject alum (i.m.). All immunized mice increased IgG, IgG1, IgG2a, IgA and fecal IgA titers compared to PBS+CFA and PBS+alum control groups. Furthermore, i.n. immunization of mice with rMESF alone presented the highest titers of serum and fecal IgA. Cytokine levels (IFN-γ, TNF-α, IL-4, and IL-17) and lymphocyte proliferation increased in all experimental groups, with the highest lymphoproliferative response in i.n. mice immunized with rMESF alone, which presented 100% protection against S. flexneri. In summary, this vaccine vests protective immunity and highlights the importance of mucosal immunity activation for the elimination of S. flexneri.

Identification of novel vaccine candidate against Salmonella enterica serovar Typhi by reverse vaccinology method and evaluation of its immunization

Salmonella enterica serovar Typhi (S. Typhi) is an essential enteric fever causing bacterium worldwide. Due to the emergence of multidrug-resistant strains, urgently attention is needed to prevent the global spread of them. Vaccination is an alternative approach to control these kinds of infections. Currently available commercial vaccines have significant limitations such as non-recommendation for children below six years of age and poor long-term efficacy. Thus, the development of a new vaccine overcoming these limitations is immediately required. Reverse Vaccinology (RV) is one of the most robust approaches for direct screening of genome sequence assemblies to identify new protein-based vaccines. The present study aimed to identify potential vaccine candidates against S. Typhi by using the RV approach. Immunogenicity of the best candidate against S. Typhi was further investigated. The proteome of S. Typhi strain Ty2 was analyzed to identify the most immunogenic, conserved, and protective surface proteins. Among the predicted vaccine candidates, steD (fimbrial subunit) was the best for qualifying all the applied criteria. The synthetic steD gene was expressed in E.coli, and the mice were immunized with purified recombinant steD protein and then challenged with a lethal dose of S. Typhi. Immunized animals generated high protein-specific antibody titers and demonstrated 70% survival following lethal dose challenge with S. Typhi. Pretreatment of the S. Typhi cells with immunized mice antisera significantly decreased their adhesion to Caco-2 cells. Altogether, steD as a protective antigen could induce a robust and long term and protective immunity in immunized mice against S. Typhi challenge.

Protective Effect of Recombinant Proteins of Cronobacter Sakazakii During Pregnancy on the Offspring

Cronobacter sakazakii is a food-borne pathogen carried in milk powder that can cause severe bacteremia, enterocolitis, and meningitis in newborns, which can lead to death of newborns. Preventing infection by this pathogen is significant to the health of newborns. Since infants and young children are the main target group of C. sakazakii, it is considered that maternal immunity can enhance the protection of newborns. Previous studies showed that two proteins of C. sakazakii (GroEL and OmpX) exhibited high expression levels and elicited strong immune reactions, suggesting their potential as vaccine candidates. In this study, GroEL and OmpX were recombinantly expressed in Escherichia coli and purified as immunogens to immunize pregnant rats. Three days after birth, the progeny were challenged with C. sakazakii to determine the protective effect of maternal immunity on the offspring. The results showed that immunization during pregnancy decreased bacterial load in the brain and blood, reduced brain and intestine damage, and significantly increased specific antibody titers in the offspring. Immunization with the recombinant proteins significantly increased cytokine levels in the serum of the progeny. The group whose mothers were immunized with OmpX produced more IL-4, while the group whose mothers were immunized with GroEL produced more IFN-γ, indicating that the immunogens enhanced the Th2 and Th1 responses, respectively. However, although the immune response was induced by both proteins, only the offspring of the pregnant rats immunized with OmpX or OmpX/GroEL mixture showed delayed death, possibly because immunization with OmpX led to a stronger humoral immune response in the offspring, suggesting that OmpX was a better vaccine candidate than GroEL. This study first reported that exposure to C. sakazakii proteins during pregnancy could improve the offspring's ability to resist infection caused by this pathogen.

Heat-shock proteins in diagnosis and treatment: an overview of different biochemical and immunological functions

Heat-shock proteins (HSPs) have been involved in different functions including chaperone activity, protein folding, apoptosis, autophagy and immunity. The HSP families have powerful effects on the stimulation of innate immune responses through Toll-like receptors and scavenger receptors. Moreover, HSP-mediated phagocytosis directly enhances the processing and presentation of internalized antigens via the endocytic pathway in adaptive immune system. These properties of HSPs have been used for development of prophylactic and therapeutic vaccines against infectious and noninfectious diseases. Several studies also demonstrated the relationship between HSPs and drug resistance as well as their use as a novel biomarker for detecting tumors in patients. The present review describes different roles of HSPs in biology and medicine especially biochemical and immunological aspects.

The evaluation of immunogenic impact of selected bacterial, recombinant Hsp60 antigens in DBA/2J mice

Heat Shock Proteins (HSP) are highly conserved proteins that are widely spread throughout all organisms. They function in the cytoplasm as chaperones; however, they could be expressed on the cell surface. It has been shown that Hsp60 obtained from gram-negative bacteria are able to stimulate cells of the acquired and innate immune system. The aim of this study was the evaluation of the immunogenic properties of recombinant Hsp60 proteins derived from four common pathogenic bacteria: Escherichia coli, Histophilus somni, Pasteurella multocida and Salmonella Enteritidis. The analysis of the humoral immune response in DBA/2J mice hyperimmunized with selected rHsp60 revealed high levels of IgG rHsp60-antibody with the predominance of the IgG₁ subclass, in the reaction with both homologous and heterologous antigens. The presence of IgG_2a and IgG_2b was also observed; however, no antibodies of subclass IgG₃ were detected. The comparison of plasma IgG antibody reactivity of mice immunized with two different doses of rHsp60 (10/20 μg) showed that the lower dose was sufficient to induce a strong humoral response. The reactivity of the IgG rHsp60-antibody with whole bacterial cells showed a significantly higher reaction with H. somni compared with other pathogens. It was demonstrated that the addition of all rHsp60 with polymyxin B to the culture medium stimulated splenocytes isolated from hyperimmunized mice to release IL-1β and IL-6. As a strong stimulator of the immune system, bacterial-origin Hsp60 seems to be an interesting potential component of subunit vaccines aimed at the development of protection for animals during infections caused by gram-negative bacteria.

The surface-displayed chaperones GroEL and DnaK of Mycoplasma pneumoniae interact with human plasminogen and components of the extracellular matrix

Mycoplasma pneumoniae is a common cause of community-acquired infections of the human respiratory tract. The strongly reduced genome of the cell wall-less bacteria results in limited metabolic pathways and a small number of known virulence factors. In addition to the well-characterized adhesion apparatus and the expression of tissue-damaging substances, surface-exposed proteins with a primary function in cytosol-located processes such as glycolysis have been attracting attention in recent years. Due to interactions with host factors, it has been suggested that these bacterial proteins contribute to pathogenesis. Here, we investigated the chaperones GroEL and DnaK of M. pneumoniae as candidates for such moonlighting proteins. After successful expression in Escherichia coli and production of polyclonal antisera, the localization of both chaperones on the surface of bacteria was confirmed. Binding of recombinant GroEL and DnaK to human A549 cells, to plasminogen as well as to vitronectin, fibronectin, fibrinogen, lactoferrin and laminin was demonstrated. In the presence of both recombinant proteins and host activators, plasminogen can be activated to the protease plasmin, which is able to degrade vitronectin and fibrinogen. The results of the study extend the spectrum of surface-exposed proteins in M. pneumoniae and indicate an additional role of both chaperones in infection processes.

Co-administration of rIpaB domain of Shigella with rGroEL of S. Typhi enhances the immune responses and protective efficacy against Shigella infection

Shigella species cause severe bacillary dysentery in humans and are associated with high morbidity and mortality. The Invasion plasmid antigen (IpaB) protein, which is conserved across all Shigella spp., induces macrophage cell death and is required to invade host cells. The present study evaluates the immunogenicity and protective efficacy of the recombinant (r) domain region of IpaB (rIpaB) of S. flexneri. rIpaB was administered either alone or was co-administered with the rGroEL (heat shock protein 60) protein from S. Typhi as an adjuvant in a mouse model of intranasal immunization. The IpaB domain region (37 kDa) of S. flexneri was amplified from an invasion plasmid, cloned, expressed in BL21 Escherichia coli cells and purified. Immunization with the rIpaB domain alone stimulated both humoral and cell-mediated immune responses. Furthermore, robust antibody (IgG, IgA) and T-cell responses were induced when the rIpaB domain was co-administered with rGroEL. Antibody isotyping revealed higher IgG1 and IgG2a antibody titers and increased interferon-gamma (IFN-γ) secretion in the co-administered group. Immunization of mice with the rIpaB domain alone protected 60%-70% of the mice from lethal infection by S. flexneri, S. boydii and S. sonnei, whereas co-administration with rGroEL increased the protective efficacy to 80%-85%. Organ burden and histopathological studies also revealed a significant reduction in lung infection in the co-immunized mice compared with mice immunized with the rIpaB domain alone. This study emphasizes that the co-administration of the rIpaB domain and rGroEL protein improves immune responses in mice and increases protective efficacy against Shigella infection. This is also the first report to evaluate the potential of the GroEL (Hsp 60) protein of S. Typhi as an adjuvant molecule, thereby overcoming the need for commercial adjuvants.

rIL-22 as an adjuvant enhances the immunogenicity of rGroEL in mice and its protective efficacy against S. Typhi and S. Typhimurium

Salmonella infection, ranging from mild, self-limiting diarrhea to severe gastrointestinal, septicemic disease and enteric fever, is a global health problem both in humans and animals. Rapid development of microbial drug resistance has led to a need for efficacious and affordable vaccines against Salmonella. Microbial heat shock proteins (HSPs), including HSP60 and HSP70, are the dominant antigens that promote the host immune response. Co-administration of these antigens with cytokines, such as IL-22, which plays an important role in antimicrobial defense, can enhance the immune response and protection against pathogens. Therefore, the aim of the present study was to determine the immunogenicity of rGroEL (Hsp60) of S. Typhi, alone or administered in combination with murine rIL-22, and its protective efficacy against lethal infection with Salmonella, in mice. There was appreciable stimulation of the humoral and cell-mediated immune responses in mice immunized with rGroEL alone. However, co-administration of rGroEL with rIL-22 further boosted the antibody titers (IgG, IgG1 and IgG2a), T-cell proliferative responses and the secretion of both Th1 and Th2 cytokines. Additionally, rGroEL alone accorded 65%-70% protection against lethal challenge with S. Typhi and S. Typhimurium, which increased to 90% when co-administered with rIL-22.

Characterization of the chaperonin GroEL in Mycoplasma gallisepticum

Mycoplasma gallisepticum (MG) is a common and widespread cause of chronic respiratory disease in poultry. In this study, antigenic proteins were identified from MG membrane using two-dimensional gel electrophoresis (2-DE) analysis followed by Western blot and matrix-assisted desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), including translation elongation factor Tu, dihydrolipoamide acetyltransferase (E2) component of pyruvate dehydrogenase complex, trigger factor, chaperone protein DnaK, heat shock protein GroEL and so on. Furthermore, recombinant MG GroEL protein was successfully expressed in E. coli BL21 (DE3) with pET-28a (+) vector and found to possess ATPase activity and contributed to the refolding of recombinant MG PrpC protein. Complement-dependent bactericidal assay indicated that the rabbit antisera against MG rGroEL had satisfactory bactericidal effect, which is similar to the chicken antisera induced by MG-inactivated vaccine, suggesting MG GroEL is a protective antigen, could be used as a novel vaccine candidate. This study is the first report of the biological characterization of chaperone GroEL protein in MG.

A novel adjuvant, the mixture of alum and naltrexone, augments vaccine-induced immunity against Plasmodium berghei

We previously showed that the mixture of naltrexone (NLT), a general opioid antagonist, and alum, acts as an effective adjuvant in enhancing vaccine-induced T helper 1 (TH1) humoral immune responses against Toxoplasma gondii. Here, we tested the efficacy of the mixture of NLT and alum in the induction of immunity in response to blood stages of Plasmodium berghei (BSPb) as a model vaccine. BALB/c mice were divided into five vaccination groups. Mice in the experimental groups received the BSPb vaccine alone or in combination with the adjuvant alum, NLT or the alum-NLT mixture. Mice in the control group received PBS. All mice were immunized on days 0, 7 and 14. Two weeks after the last immunization, immune responses to Plasmodium berghei were assessed. Our results indicated that including the alum-NLT mixture as an adjuvant during vaccination increased the ability of the BSPb vaccine to enhance lymphocyte proliferation, shifted the immune response towards a TH1 profile and increased Plasmodium berghei-specific IgG2a. This resulted in improved protective immunity against Plasmodium berghei. In conclusion, administering alum-NLT mixture in combination with the BSPb vaccine enhanced the vaccine-induced immunity, and shifted the immune response toward TH1 pattern.

B-cell epitopes in GroEL of Francisella tularensis

The chaperonin protein GroEL, also known as heat shock protein 60 (Hsp60), is a prominent antigen in the human and mouse antibody response to the facultative intracellular bacterium Francisella tularensis (Ft), the causative agent of tularemia. In addition to its presumed cytoplasmic location, FtGroEL has been reported to be a potential component of the bacterial surface and to be released from the bacteria. In the current study, 13 IgG2a and one IgG3 mouse monoclonal antibodies (mAbs) specific for FtGroEL were classified into eleven unique groups based on shared VH-VL germline genes, and seven crossblocking profiles revealing at least three non-overlapping epitope areas in competition ELISA. In a mouse model of respiratory tularemia with the highly pathogenic Ft type A strain SchuS4, the Ab64 and N200 IgG2a mAbs, which block each other’s binding to and are sensitive to the same two point mutations in FtGroEL, reduced bacterial burden indicating that they target protective GroEL B-cell epitopes. The Ab64 and N200 epitopes, as well as those of three other mAbs with different crossblocking profiles, Ab53, N3, and N30, were mapped by hydrogen/deuterium exchange–mass spectrometry (DXMS) and visualized on a homology model of FtGroEL. This model was further supported by its experimentally-validated computational docking to the X-ray crystal structures of Ab64 and Ab53 Fabs. The structural analysis and DXMS profiles of the Ab64 and N200 mAbs suggest that their protective effects may be due to induction or stabilization of a conformational change in FtGroEL.

Molecular cloning, characterization, and expression of hsp60 in caudal fin regeneration of Misgurnus anguillicaudatus

Urodele amphibians and teleost fish are capable of nearly perfect regeneration of lost appendages. The fin constitutes an important model for studying the molecular basis of tissue regeneration. It has been known that heat shock protein 60 (Hsp60) is a multifunctional protein of the heat shock protein family. The purpose of this study is to investigate the role of hsp60 as a part of a stress response system after fin injury or in fin regeneration. We firstly cloned full-length cDNA of hsp60 from Misgurnus anguillicaudatus (designated as MaHsp60) by RACE method. The cDNA contains a 83-bp 5'UTR, a 1,728-bp open reading frame encoding 492 amino acids and a 542-bp 3'UTR (Accession No.: KF537340). The phylogenetic tree shows that the MaHsp60 fits within the hsp60 clade. Then quantitative RT-PCR detected that MaHsp60 began to increase rapidly its expression at 1 dpa and reached its peak at 2 dpa. Next, spatial distribution analysis of MaHsp60 in fins showed that MaHsp60 located mainly in the deeper layer of regenerated epidermis when MaHsp60 expressed most. After the MaHsp60 had been cloned into the pET-32a vector, SDS-PAGE analysis confirmed that the MaHsp60 protein was efficiently expressed in Escherichia coli BL21 and adjustable with the temperature. These findings have revealed that MaHsp60, a highly conserved gene during vertebrate evolution as well as related to stress response, is involved in the formation of wound epidermis which occurs as the first phase of fin regeneration after fin amputation in caudal fin regeneration.

Co-expression of S. Typhi GroEL and IL-22 gene augments immune responses against Salmonella infection

Recombinant DNA vaccines represent a novel method for generating in situ expression of vaccine antigens. Intramuscular injections of naked DNA are able to elicit potent humoral and cellular immune responses but still numerous factors limit the immunogenicity of DNA vaccines. Co-expression of cytokines with antigen encoding genes in DNA vectors can improve the immune responses and modify Th1/Th2 balance. In this study, the immunomodulatory effect of Interleukin 22 (IL-22) as an adjuvant was studied by DNA vaccination with S. Typhi Heat shock protein 60 (HSP60/GroEL) in mice. Further, DNA construct of IL-22 gene fused with GroEL was developed and immunization studies were carried out in mice. DNA vaccination with GroEL alone stimulated humoral and cell-mediated immune responses. Co-immunization (IL-22+GroEL) further resulted in increase in T-cell proliferative responses, antibody titres (IgG, IgG1, IgG2a) and secretion of IFNγ (Th1), IL-1β and Th2 (IL-4, IL-6) cytokines. Co-expression (IL-22-GroEL DNA) also promoted antibody titres and cytokine levels were significantly higher as compared to co-immunized group. A reduction in bacterial load in spleen, liver and intestine was seen in all the immunized groups as compared to control, with least organ burden in fusion DNA construct group (co-expression). Improved protective efficacy (90%) against lethal challenge by Salmonella was observed with IL-22-GroEL co-expressing DNA vector as compared with plasmid encoding GroEL only (50-60%) or co-immunization group (75-80%). This study thus shows that co-expression of IL-22 and GroEL genes enhances the immune responses and protective efficacy, circumventing the need of any adjuvant.

Aggregatibacter actinomycetemcomitans GroEL protein promotes conversion of human CD4+ T cells into IFNγ IL10 producing Tbet+ Th1 cells

One of the heat shock family protein (Hsp) expressing bacteria is the gram negative, periodontal pathogen Aggregatibacter actinomycetemcomitans (Aa). A. actinomycetemcomitans’ Hsp is a 64-kDa GroEL-protein, which has been shown to influence the host cells. In this study we used recombinant A. actinomycetemcomitans GroEL (rAaGroEL) protein as a model antigen to study GroEL-mediated T cell immune response. Human peripheral mononuclear cells (PBMCs), when stimulated with recombinant rAaGroEL, expressed early activation marker CD69 and IL-2R (CD25). CD25 and CD69 expressions were higher in CD4+ T cells compared to CD8+ T cells. rAaGroEL-responding CD4+ T cells expressed IL-10, IFNγ and TNFα cytokines. Interestingly, there were also IL-10 and IFNγ double cytokine producing CD4+ T cells. Additionally, IFNγ expressing CD4+ T cells were also T-bet positive. Altogether the results suggest that rAaGroEL protein affects CD4+ T cells to differentiate into IFNγ IL10-secreting T-bet+ Th1 cells.

Mucosal immunization with caseinolytic protease X elicited cross-protective immunity against pneumococcal infection in mice

Streptococcus pneumoniae resides on the mucosal surface of the upper respiratory tract and is ready to spread and trigger clinical diseases. Hence the vaccine that can eliminate the nasopharyngeal colonization was thought to be an ideal protective strategy against pneumococcal invasive diseases. Caseinolytic protease X (ClpX), a pneumococcal caseinolytic protease ATPase subunit, was shown to be a non-transmembrane protein by bioinformatics analysis. Consistent with the in silico prediction, the secretory expression of ClpX, instead of surface exposure, was further confirmed by flow cytometry and Western blot. Furthermore, ClpX was highly conserved in nine different serotypes of S. pneumoniae at both gene and protein concentrations. In addition, the anti-ClpX IgG antibody levels in human serum samples were much higher in healthy children, compared with pediatric patients, and displayed an age-related increase. Finally, ClpX protein antigen was introduced to BALB/c mice through a mucosal route, and protection against nasopharyngeal colonization and lethal infection caused by different S. pneumoniae serotypes was successfully elicited. Our findings suggest that ClpX is a potential candidate antigen that could be incorporated in pneumococcal protein vaccines.

A novel adjuvant, mixture of alum and the beta-adrenergic receptor antagonist propranolol, elicits both humoral and cellular immune responses for heat-killed Salmonella typhimurium vaccine

OBJECTIVE

To determine the efficacy of the mixture of propranolol (PRP), a beta-adrenergic receptor antagonist, and alum, as a new adjuvant, in the induction of humoral and cellular immunity in response to heat-killed Salmonella typhimurium (S. typhimurium) (HKST) as a model vaccine.

METHODS

BALB/c mice were divided into five groups. Mice in the experimental groups received either the HKST vaccine alone or in combination with the adjuvant alum, PRP or the alum-PRP mixture. Mice in the negative control group received phosphate-buffered saline. All mice were immunized two times on days 0 and 14. Two weeks after the last immunization, immune responses to S. typhimurium were assessed.

RESULTS

Administration of the alum-PRP mixture as an adjuvant increased the ability of the HKST vaccine to enhance lymphocyte proliferation, shifted the immune response towards a T-helper (Th) 1 pattern and increased S. typhimurium specific IgG, IgG2a and IgG1. This resulted in improved protective immunity against S. typhimurium.

CONCLUSION

Administration of the alum-PRP mixture as an adjuvant in combination with the HKST vaccine, can enhance both humoral and cellular immunity and shift the immune responses to a Th1 pattern.

Structure-based vaccines provide protection in a mouse model of ehrlichiosis

BACKGROUND

Recent advances in bioinformatics have made it possible to predict the B cell and T cell epitopes of antigenic proteins. This has led to design of peptide based vaccines that are more specific, safe, and easy to produce. The obligately intracellular gram negative bacteria Ehrlichia cause ehrlichioses in humans and animals. As yet there are no vaccines to protect against Ehrlichia infection.

METHODOLOGY/PRINCIPAL FINDINGS

We applied the principle of structural vaccinology to design peptides to the epitopes of Ehrlichia muris outer membrane P28-19 (OMP-1/P28) and Ehrlichia Heat shock protein 60 (Hsp60/GroEL) antigenic proteins. Both P28-19 and Ehrlichia Hsp60 peptides reacted with polyclonal antibodies against E. canis and E. chaffeensis and could be used as a diagnostic tool for ehrlichiosis. In addition, we demonstrated that mice vaccinated with Ehrlichia P28-19 and Hsp60 peptides and later challenged with E. muris were protected against the pathogen.

CONCLUSIONS/SIGNIFICANCE

Our results demonstrate the power of structural vaccines and could be a new strategy in the development of vaccines to provide protection against pathogenic microorganisms.

A novel adjuvant, a mixture of alum and the general opioid antagonist naloxone, elicits both humoral and cellular immune responses for heat-killed Salmonella typhimurium vaccine

In the current study, we tested the efficacy of the mixture of naloxone, an opioid receptor antagonist, and alum, as a new adjuvant, in the induction of humoral and cellular immunity in response to heat-killed Salmonella typhimurium (HKST) as a model vaccine. BALB/c mice were divided into five groups. Mice in the experimental groups received either the HKST vaccine alone or in combination with the adjuvant alum, naloxone or the alum-naloxone mixture. Mice in the negative control group received phosphate-buffered saline. All mice were immunized two times on days 0 and 14. Two weeks after the last immunization, immune responses to S. typhimurium were assessed. Our results indicated that the administration of the alum-naloxone mixture as an adjuvant increased the ability of the HKST vaccine to enhance lymphocyte proliferation, shifted the immune response towards a T-helper 1 (Th1) pattern and increased S. typhimurium-specific immunoglobulin G (IgG), IgG2a, IgG1 and the ratio of IgG2a to IgG1. This resulted in improved protective immunity against S. typhimurium. In conclusion, the administration of the alum-naloxone mixture as an adjuvant, in combination with the HKST vaccine, can enhance both humoral and cellular immunity and shift the immune responses to a Th1 pattern.

Naloxone and alum synergistically augment adjuvant activities of each other in a mouse vaccine model of Salmonella typhimurium infection

Alum is the most commonly used adjuvant for human vaccination but is a poor inducer of cell mediated immunity and T helper 1 (Th1) responses. We have previously shown that naloxone (NLX), which is a general opioid antagonist, acts as an effective adjuvant in enhancing vaccine-induced cellular immunity and Th1 immune responses. Here, we tested the efficacy of an alum-NLX mixture, as a new adjuvant, in the induction of humoral and cellular immunity in response to endotoxin-removed lysate (ERL) of Salmonella typhimurium (S. typhimurium) as a model vaccine. BALB/c mice were divided into five vaccination groups. Mice in the experimental groups received either the ERL vaccine alone or in combination with the adjuvant alum, NLX or the alum-NLX mixture. Mice in the negative control group received phosphate-buffered saline. All mice were immunized on days 0 and 7. Two weeks after the last immunization, immune responses to S. typhimurium were assessed. Our results indicate that including the alum-NLX mixture as an adjuvant during vaccination increased the ability of the ERL vaccine to enhance lymphocyte proliferation, shifted the immune response toward a Th1 profile and increased S. typhimurium-specific IgG, IgG2a and the ratio of IgG2a to IgG1. This resulted in improved protective immunity against S. typhimurium. In conclusion, administering an alum-NLX mixture adjuvant in combination with the ERL vaccine enhances both humoral and cellular immunity, and shifts the immune response to a Th1 pattern.