A systematic approach for the identification of novel, serologically reactive recombinant Varicella-Zoster Virus (VZV) antigens

Novel LysM motifs for antigen display on lactobacilli for mucosal immunization

We characterized two LysM domains of Limosilactobacillus fermentum, belonging to proteins Acglu (GenBank: KPH22907.1) and Pgb (GenBank: KPH22047.1) and bacterium like particles (BLP) derived from the immunomodulatory strain Lacticaseibacillus rhamnosus IBL027 (BLPs027) as an antigen display platform. The fluorescence protein Venus fused to the novel LysM domains could bind to the peptidoglycan shell of lactobacilli and resisted harsh conditions such as high NaCl and urea concentrations. Acglu with five LysM domains was a better anchor than Pgb baring only one domain. Six-week-old BALB/c mice were nasally immunized with the complex Venus-Acglu-BLPs027 at days 0, 14 and 28. The levels of specific serum IgG, IgG1 and IgG2a and the levels of total immunoglobulins (IgT) and IgA in broncho-alveolar lavage (BAL) were evaluated ten days after the last boosting. Venus-Acglu-BLPs027, nasally administered, significantly increased specific BAL IgT and IgA, and serum IgG levels. In addition, spleen cells of mice immunized with Venus-Acglu-BLPs027 secreted TNF-α, IFN-γ and IL-4 when stimulated ex vivo in a dose-dependent manner. We constructed a Gateway compatible destination vector to easily fuse the selected LysM domain to proteins of interest for antigen display to develop mucosal subunit vaccines.

Oral Vaccination with Hepatitis E Virus Capsid Protein and Immunobiotic Bacterium-Like Particles Induce Intestinal and Systemic Immunity in Mice

The hepatitis E virus (HEV) genotype 3 (GT3) is an emergent pathogen in industrialized countries. It is transmitted zoonotically and may lead to chronic hepatitis in immunocompromised individuals. We evaluated if the major antigen of HEV, the capsid protein, can be used in combination with immunobiotic bacterium-like particles (IBLP) for oral vaccination in a mouse model. We have cloned and expressed the RGS-His₅-tagged HEV GT3 capsid protein (ORF2) in E. coli and purified it by NiNTA. IBLP were obtained from two immunobiotic Lactobacillus rhamnosus strains acid- and heat-treated. ORF2 and the IBLP were orally administered to Balb/c mice. After three oral immunizations (14-day intervals), blood, intestinal fluid, Peyer´s patches, and spleen samples were drawn. IgA- and IgG-specific antibodies were determined by ELISA. Mononuclear cell populations from Peyer's patches and spleen were analyzed by flow cytometry, and the cytokine profiles were determined by ELISA to study cellular immunity. Orally administered recombinant ORF2 and IBLP from two L. rhamnosus strains (CRL1505 and IBL027) induced both antigen-specific humoral and cellular immune responses in mice. IBLP027 was more effective in inducing specific secretory IgA in the gut. IFN-γ, TNF-α, and IL-4 were produced by Peyer's plaques lymphocytes stimulated with ORF2 ex vivo suggesting a mixed Th1/Th2-type adaptive immune response in immunized mice. Oral vaccines are not invasive, do not need to be administered by specialized personal, and elicit both systemic and local immune responses at the port of entry. Here, we present an experimental oral vaccine for HEV GT3, which could be further developed for human and/or veterinary use.

A Novel In-House Enzyme-Linked Immunosorbent Assay for Genotype 3 Hepatitis E Virus Reveals High Seroprevalence in Blood Donors in Northern Argentina

The Hepatitis E virus (HEV) is an emergent virus that causes acute hepatitis in immunocompetent hosts and chronic hepatitis in immunocompromised hosts. In Latin America, the main circulating genotype HEV-3 is usually of zoonotic origin. Diagnosis and seroprevalence studies mainly rely on the detection of specific antibodies. There are scarce data on the seroprevalence of HEV infection in Latin America mainly due to the lack of awareness of HEV circulation. Furthermore, in some countries, like Argentina, HEV testing is not included in routine assays. In order to provide tools to deepen the knowledge on HEV epidemiology in South America, we designed a new in-house ELISA based on the native recombinant protein ORF2 aa112–608 and demonstrated its potential for detecting anti-HEV immunoglobulin G (IgG) in human serum samples. The following conditions were determined: an optimal antigen concentration of 0.25 μg/ml, a serum dilution of 1:80, gelatin as a blocking agent, and a secondary antibody dilution of 1:2000. A relative sensitivity of 93.33% (95% CI: 77.9–99.2%) and a relative specificity of 99.4% (95% CI: 96.7–100%) were determined using a panel of previously characterized sera and a gold standard (HEV IgG ELISA, DIA.PRO, Italy). Further, we obtained a very good agreement (κ index = 0.94, 95% CI: 0.87–1.00) with the gold standard. We screened 813 blood donor samples with this newly developed ELISA and found a seroprevalence of 9.23% (95% confidence interval, 7.33–11.43%). We show for the first time evidence of past HEV infection in Tucuman, the most populated city in northern Argentina. We expect that this study will raise the interest of health decision makers who should intercede to include indirect testing of HEV in regular diagnostic protocols. In conclusion, the in-house ELISA developed in this work shows a very good agreement with an already licensed commercial HEV IgG ELISA (DIA.PRO, ITALY), which can be used as an epidemiologic tool for HEV surveillance.

Varicella Virus-Host Interactions During Latency and Reactivation: Lessons From Simian Varicella Virus

Varicella zoster virus (VZV) is a neurotropic alphaherpesvirus and the causative agent of varicella (chickenpox) in humans. Following primary infection, VZV establishes latency in the sensory ganglia and can reactivate to cause herpes zoster, more commonly known as shingles, which causes significant morbidity, and on rare occasions mortality, in the elderly. Because VZV infection is highly restricted to humans, the development of a reliable animal model has been challenging, and our understanding of VZV pathogenesis remains incomplete. As an alternative, infection of rhesus macaques with the homologous simian varicella virus (SVV) recapitulates the hallmarks of VZV infection and thus constitutes a robust animal model to provide critical insights into VZV pathogenesis and the host antiviral response. In this model, SVV infection results in the development of varicella during primary infection, generation of an adaptive immune response, establishment of latency in the sensory ganglia, and viral reactivation upon immune suppression. In this review, we discuss our current knowledge about host and viral factors involved in the establishment of SVV latency and reactivation as well as the important role played by T cells in SVV pathogenesis and antiviral immunity.

Herpes Zoster and Immunogenicity and Safety of Zoster Vaccines in Transplant Patients: A Narrative Review of the Literature

This narrative review focuses on the herpes zoster (HZ) and its prevention in transplant patients. Varicella zoster virus (VZV) is highly contagious and distributed worldwide in humans. Primary VZV infection usually causes varicella and then establishes a lifelong latency in dorsal root ganglia. Reactivation of VZV leads to HZ and related complications such as postherpetic neuralgia. Age and decreased immunity against VZV are important risk factors for developing HZ. Transplant patients are at increased risk for developing HZ and related complications due to their immunocompromised status and the need for lifetime immunosuppression. Diagnosis of HZ in transplant patients is often clinically difficult, and VZV-specific antibodies should be determined by serologic testing to document prior exposure to VZV during their pre-transplant evaluation process. Although antiviral agents are available, vaccination should be recommended for preventing HZ in transplant patients considering their complicated condition and weak organ function. Currently, there are two licensed HZ vaccines, of which one is a live-attenuated vaccine and the other is a HZ subunit vaccine. Both vaccines have shown promising safety and efficacy in transplants patients and especially the subunit vaccine could be administered post-transplant since this vaccine does not contain any live virus. Larger studies are needed about safety and immunogenicity of HZ vaccines in transplant populations, and extra efforts are needed to increase vaccine usage according to guidelines.

The Hepatitis E virus intraviral interactome

Hepatitis E virus (HEV) is an emerging virus causing epidemic acute hepatitis in developing countries as well as sporadic cases in industrialized countries. The life cycle of HEV is still poorly understood and the lack of efficient cell culture systems and animal models are the principal limitations for a detailed study of the viral replication cycle. Here we exhaustively examine all possible intraviral protein-protein interactions (PPIs) of HEV by systematic Yeast two-hybrid (Y2H) and LuMPIS screens, providing a basis for studying the function of these proteins in the viral replication cycle. Key PPIs correlate with the already published HEV 3D structure. Furthermore, we report 20 novel PPIs including the homodimerization of the RNA dependent RNA polymerase (RdRp), the self-interaction of the papain like protease, and ORF3 interactions with the papain-like protease and putative replicase components: RdRp, methylase and helicase. Furthermore, we determined the dissociation constant (K_d) of ORF3 interactions with the viral helicase, papain-like protease and methylase, which suggest a regulatory function for ORF3 in orchestrating the formation of the replicase complex. These interactions may represent new targets for antiviral drugs.

Systematic reference sample generation for multiplexed serological assays

Quality controls of serological assays have to contain defined amounts of human antibodies specific for the targeted antigen. A prevailing issue for array-based antigen assays is that dozens of antigens are targeted within the same assay. Commonly different patient sera are combined and optimal pools are empirically identified. Here, we report a mathematical approach how an optimal sample pool composition can be systematically calculated and accurately compiled. The approach was used to compose suitable quality controls for a 71 plex Tuberculosis antigen bead array using a limited number of positive human sera.

Malaria vaccines: high-throughput tools for antigens discovery with potential for their development

Malaria is a disease induced by parasites of the Plasmodium genus, which are transmitted by Anopheles mosquitoes and represents a great socio-economic burden Worldwide. Plasmodium vivax is the second species of malaria Worldwide, but it is the most prevalent in Latin America and other regions of the planet. It is currently considered that vaccines represent a cost-effective strategy for controlling transmissible diseases and could complement other malaria control measures; however, the chemical and immunological complexity of the parasite has hindered development of effective vaccines. Recent availability of several genomes of Plasmodium species, as well as bioinformatic tools are allowing the selection of large numbers of proteins and analysis of their immune potential. Herein, we review recently developed strategies for discovery of novel antigens with potential for malaria vaccine development.

Surface-activated microtiter-plate microarray for simultaneous CRP quantification and viral antibody detection

Microarrays are widely used in high-throughput DNA and RNA hybridization tests and recently adopted to protein and small molecule interaction studies in basic research and diagnostics. Parallel detection of serum antibodies and antigens has several potential applications in epidemiologic research, vaccine development, and in the diagnosis of allergies, autoimmunity, and infectious diseases. This study demonstrates an immobilization method for immunoassay-based microarray in conventional 96-well polystyrene plates for a serologic diagnostic method combined with quantitative C-reactive protein (CRP) assay. A synthetic peptide (HIV-1), a recombinant protein (Puumala hantavirus nucleocapsid), and purified virus preparations (Sindbis and adenoviruses) were used as antigens for virus-specific antibody detection and monoclonal anti-CRP antibody for antigen detection. The microarray was based on conventional enzyme immunoassays and densitometry from photographed results. Peptide and recombinant antigens functioned well, while whole virus antigens gave discrepant results in 1 out of 23 samples from the reference method, tested with human sera with various antibody responses. The CRP results were in concordance in the concentration range 0.5-150 mg/L with 2 commercially available CRP assays: ReaScan rapid test (R(2) = 0.9975) and Cobas 6000 analyzer (R(2) =0.9595). The results indicate that microtiter plates provide a promising platform for further development of microarrays for parallel antibody and antigen detection.

Serologic analysis of the IgG antibody response in children with varicella zoster virus wild-type infection and vaccination

INTRODUCTION

In contrast to varicella zoster virus (VZV) primary infection, VZV vaccination does not seem to provide lifelong immunity against varicella. Because more people get vaccinated every year, the development of sensitive serological test systems for the detection of protective anti-VZV IgG will become important in the future.

METHODS

We have previously developed a novel VZV line assay based on 5 different recombinant VZV antigens. In this study, we compared this novel assay with a commercially available glycoprotein enzyme immunoassay (RIDASCREEN VZV IgG) in detecting anti-VZV IgG of children with previous varicella infection and VZV vaccination.

RESULTS

One hundred twenty-five children were included in this study, 72 with a history of varicella infection and 53 with VZV vaccination. Both assays detected anti-VZV IgG antibodies in both study groups with similar sensitivities. The VZV line assay revealed striking differences in the anti-VZV IgG composition against the VZV open reading frames, 4, 14 and 49, between both study groups, indicating that wild-type varicella infection causes a more diverse immune response against VZV than does vaccination. The exploitation of these results enabled the discrimination of both study groups with a sensitivity of 0.93 and a specificity of 0.83, indicating that the serologic differentiation of children with previous varicella infection and VZV vaccination might be possible.

CONCLUSION

The VZV line assay enables the detection of anti-VZV IgG with sensitivities comparable to glycoprotein enzyme immunoassays and might be suitable for the serologic discrimination between children with a history of varicella infection and VZV vaccination.

RNA interference is responsible for reduction of transgene expression after Sleeping Beauty transposase mediated somatic integration

Background

Integrating non-viral vectors based on transposable elements are widely used for genetically engineering mammalian cells in functional genomics and therapeutic gene transfer. For the Sleeping Beauty (SB) transposase system it was demonstrated that convergent transcription driven by the SB transposase inverted repeats (IRs) in eukaryotic cells occurs after somatic integration. This could lead to formation of double-stranded RNAs potentially presenting targets for the RNA interference (RNAi) machinery and subsequently resulting into silencing of the transgene. Therefore, we aimed at investigating transgene expression upon transposition under RNA interference knockdown conditions.

Principal Findings

To establish RNAi knockdown cell lines we took advantage of the P19 protein, which is derived from the tomato bushy stunt virus. P19 binds and inhibits 21 nucleotides long, small-interfering RNAs and was shown to sufficiently suppress RNAi. We found that transgene expression upon SB mediated transposition was enhanced, resulting into a 3.2-fold increased amount of colony forming units (CFU) after transposition. In contrast, if the transgene cassette is insulated from the influence of chromosomal position effects by the chicken-derived cHS4 insulating sequences or when applying the Forg Prince transposon system, that displays only negligible transcriptional activity, similar numbers of CFUs were obtained.

Conclusion

In summary, we provide evidence for the first time that after somatic integration transposon derived transgene expression is regulated by the endogenous RNAi machinery. In the future this finding will help to further improve the molecular design of the SB transposase vector system.

Systematic screening for novel, serologically reactive Hepatitis E Virus epitopes

Background

The National Institutes of Health classified Hepatitis E as an emerging disease since Hepatitis E Virus (HEV) is the major cause of acute hepatitis in developing countries. Interestingly, an increasing number of sporadic cases of HEV infections are described in industrialized countries as zoonosis from domestic livestock. Despite the increasing relevance of this pathogen in clinical virology, commercial antibody assays are mainly based on fragments of HEV open reading frame (ORF) 2 and ORF3. The largest ORF1 (poly-)protein, however, is not part of current testing formats.

Methods

From a synthesized full length HEV genotype 1 cDNA-bank we constructed a complete HEV gene library consisting of 15 respective HEV ORF domains. After bacterial expression and purification of nine recombinant HEV proteins under denaturating conditions serum profiling experiments using 55 sera from patients with known infection status were performed in microarray format. SPSS software assessed the antigenic potential of these nine ORF domains in comparison to seven commercial HEV antigens (genotype 1 and 3) by performing receiver operator characteristics, logistic regression and correlation analysis.

Results

HEV antigens produced with our method for serum profiling experiments exhibit the same quality and characteristics as commercial antigens. Serum profiling experiments detected Y, V and X domains as ORF1-antigens with potentially comparable diagnostic significance as the well established epitopes of ORF2 and ORF3. However no obvious additional increase in sensitivity or specificity was achieved in diagnostic testing as revealed by bioinformatic analysis. Additionally we found that the C-terminal domain of the potential transmembrane protein ORF3 is responsible for IgG and IgM seroreactivity. Data suggest that there might be a genotype specific seroreactivity of homologous ORF2-antigens.

Conclusions

The diagnostic value of identified ORF1 epitopes might not necessarily improve sensitivity and specificity, but broaden the overall quality of existing test systems. ORF2 and ORF3-antigens are still commonly used in diagnostic assays and possibly hold the potential to serologically differentiate between genotype 1 and 3 infections. Our systematic approach is a suitable method to investigate HEV domains for their serologic antigenicity. Epitope screening of native viral domains could be a preferable tool in developing new serologic test components.

Varicella zoster virus ORF25 gene product: an essential hub protein linking encapsidation proteins and the nuclear egress complex

Varicella zoster virus (VZV) ORF25 is a 156 amino acid protein belonging to the approximately 40 core proteins that are conserved throughout the Herpesviridae. By analogy to its functional orthologue UL33 in Herpes simplex virus 1 (HSV-1), ORF25 is thought to be a component of the terminase complex. To investigate how cleavage and encapsidation of viral DNA links to the nuclear egress of mature capsids in VZV, we tested 10 VZV proteins that are predicted to be involved in either of the two processes for protein interactions against each other using three independent protein-protein interaction (PPI) detection systems: the yeast-two-hybrid (Y2H) system, a luminescence based MBP pull-down interaction screening assay (LuMPIS), and a bioluminescence resonance energy transfer (BRET) assay. A set of 20 interactions was consistently detected by at least 2 methods and resulted in a dense interaction network between proteins associated in encapsidation and nuclear egress. The results indicate that the terminase complex in VZV consists of ORF25, ORF30, and ORF45/42 and support a model in which both processes are closely linked to each other. Consistent with its role as a central hub for protein interactions, ORF25 is shown to be essential for VZV replication.

Protein microarrays and biomarkers of infectious disease

Protein microarrays are powerful tools that are widely used in systems biology research. For infectious diseases, proteome microarrays assembled from proteins of pathogens will play an increasingly important role in discovery of diagnostic markers, vaccines, and therapeutics. Distinct formats of protein microarrays have been developed for different applications, including abundance-based and function-based methods. Depending on the application, design issues should be considered, such as the need for multiplexing and label or label free detection methods. New developments, challenges, and future demands in infectious disease research will impact the application of protein microarrays for discovery and validation of biomarkers.

Amphipathic C-terminal region of Escherichia coli NADH dehydrogenase-2 mediates membrane localization

Respiratory NADH dehydrogenase-2 (NDH-2) of Escherichia coli is a membrane-bound flavoprotein. Bioinformatics approaches suggested the involvement of NDH-2 C-terminal region in membrane anchorage. Here, we demonstrated that NDH-2 is a peripheral membrane protein and that its predicted C-terminal amphipathic Arg390-Ala406 helix is sufficient to bind the protein to lipid membranes. Additionally, a cytosolic NDH-2 protein (Trun-3), lacking the last 43 aminoacids, was purified and characterized. FAD cofactor was absent in purified Trun-3. Upon the addition of FAD, Trun-3 maximum velocity was similar to native NDH-2 rate with ferricyanide and MTT acceptors. However, Trun-3 activity was around 5-fold lower with quinones. No significant difference in K(m) values was observed for both enzymes. For the first time, an active and water soluble NDH-2 was obtained, representing a major improvement for structural/functional characterizations.