The ability of Hepatitis B surface antigen DNA vaccine to elicit cell-mediated immune responses, but not antibody responses, was affected by the deglysosylation of S antigen

rpoS involved in immune response of Macrobrachium nipponens to Vibrio mimicus infection

Vibrio mimicus is a pathogenic bacterium that cause red body disease in Macrobrachium nipponense, leading to high mortality and financial loss. Based on previous studies, rpoS gene contribute to bacterial pathogenicity during infection, but the role of RpoS involved in the immune response of M. nipponense under V. mimicus infection remains unclear. In this study, the pathogen load and the RNA-seq of M. nipponense under wild-type and ΔrpoS strain V. mimicus infection were investigated. Over the entire infection period, the ΔrpoS strain pathogen load was always lower than that of the wild-type strain in the M. nipponense hemolymph, hepatopancreas, gill and muscle. Furthermore, the expression level of rpoS gene in the hepatopancreas was the highest at 24 hours post infection (hpi), then the samples of hepatopancreas tissue infected with the wild type and ΔrpoS strain at 24 hpi were selected for RNA-seq sequencing. The results revealed a significant change in the transcriptomes of the hepatopancreases infected with ΔrpoS strain. In contrast to the wild-type infected group, the ΔrpoS strain infected group exhibited differentially expressed genes (DEGs) enriched in 181 KEGG pathways at 24 hpi. Among these pathways, 8 immune system-related pathways were enriched, including ECM-receptor interaction, PI3K-Akt signaling pathway, Rap1 signaling pathway, Gap junction, and Focal adhesion, etc. Among these pathways, up-regulated genes related to Kazal-type serine protease inhibitors, S-antigen protein, copper zinc superoxide dismutase, tight junction protein, etc. were enriched. This study elucidates that rpoS can affect tissue bacterial load and immune-related pathways, thereby impacting the survival rate of M. nipponense under V. mimicus infection. These findings validate the potential of rpoS as a promising target for the development of a live attenuated vaccine against V. mimicus.

N-Glycosylation and N-Glycan Processing in HBV Biology and Pathogenesis

Hepatitis B Virus (HBV) glycobiology has been an area of intensive research in the last decades and continues to be an attractive topic due to the multiple roles that N-glycosylation in particular plays in the virus life-cycle and its interaction with the host that are still being discovered. The three HBV envelope glycoproteins, small (S), medium (M) and large (L) share a very peculiar N-glycosylation pattern, which distinctly regulates their folding, degradation, assembly, intracellular trafficking and antigenic properties. In addition, recent findings indicate important roles of N-linked oligosaccharides in viral pathogenesis and evasion of the immune system surveillance. This review focuses on N-glycosylation’s contribution to HBV infection and disease, with implications for development of improved vaccines and antiviral therapies.

N-Linked Glycosylation at an Appropriate Position in the Pre-S2 Domain Is Critical for Cellular and Humoral Immunity against Middle HBV Surface Antigen

Infection with hepatitis B virus (HBV) remains a worldwide health problem, and DNA-based vaccines against HBV have been tested for therapeutic applications. HBV possesses three envelope lipoproteins that are translated from a single reading-frame: large, middle, and small HBV surface antigens. Among these envelope proteins, the middle HBV surface antigen (MHBs) contains a constitutive N-linked glycosylation site at position 4 (Asn4) in the amino-terminal portion (MQWNSTTFHQ) of pre-S2 domain. Asn4 (shown in bold) is essential for secretion of viral particles and conserved among all serotypes of HBV, but its influence on the immunogenicity of MHBs remains unknown. Here, we constructed four MHBs genes carrying mutations, underlined, in the amino-terminal portion of pre-S2 domain. One mutant protein contains Q at position 4 (MQWQSTTFHQ). In addition, each of three mutant MHBs proteins contains a N-linked glycosylation site (N-X-S/T), relocated to position 5 (MQWQNTTFHQ), 6 (MQWQSNTSHQ) or 7 (MQWQSTNFTQ) in pre-S2 domain. The expression and immunogenic properties of mutant DNA vaccines were examined in 293T human renal epithelial cells and in BALB/c mice, respectively. We showed that Asn4 was critical for secretion and immunogenicity of MHBs. Moreover, the MHBs protein that carries a N-linked glycosylation site at position 5 or 7 retained the properties similar to wild-type MHBs. In contrast, the secretion-defective mutant protein carrying Asn at position 6 induced only marginal humoral and cellular immune responses in mice, despite the N-linked glycosylation. In conclusion, N-linked glycosylation at an appropriate position in pre-S2 domain is an essential requirement for DNA vaccine expressing MHBs.

Nucleic acid vaccination strategies against infectious diseases

INTRODUCTION

Gene vaccines are an interesting and emerging alternative for the prevention of infectious diseases, as well as in the treatment of other pathologies including cancer, allergies, autoimmune diseases, or even drug dependencies. When applied to the target organism, these vaccines induce the expression of encoded antigens and elicit the corresponding immune response, with the potential ability of being able to induce antibody-, helper T cell-, and cytotoxic T cell-mediated immune responses.

AREAS COVERED

Special attention is paid to the variety of adjuvants that may be co-administered to enhance and/or to modulate immune responses, and to the methods of delivery. Finally, this article reviews the efficacy data of gene vaccines against infectious diseases released from current clinical trials.

EXPERT OPINION

Taken together, this approach will have a major impact on future strategies for the prevention of infectious diseases. Better-designed nucleic acid constructs, novel delivery technologies, as well as the clarification of the mechanisms for antigen presentation will improve the potential applications of this vaccination strategy against microbial pathogens.

IgE anti Hepatitis B virus surface antigen antibodies detected in serum from inner city asthmatic and non asthmatic children

Viral Hepatitis type B (HBV) is a public health concern, but has not been linked to asthma. Immunoglobulin (Ig) G is involved in HBV immune responses; less is known about IgE antibodies (Abs) against HBV in asthma. Given the importance of HBV, we sought to determine whether HBV vaccine contributes to asthma in children, by stimulating specific IgE production. Total IgE, IgE- or IgG-anti-HBVs Abs were studied in vaccinated pediatric asthmatics and non asthmatics. We found: (1) total IgE was higher in asthmatics; (2) total IgE did not correlate with IgE anti-HBVs; (3) IgE anti-HBVs did correlate with IgG-anti-HBVs in all subjects; (4)IgE- and IgG-HBVs Abs were similar in both groups; (5) IgE- or IgG anti-HBVs Abs did not correlate with age. Our findings indicate that HBV vaccination induces IgE responses in asthmatics and non asthmatics.

DNA immunization

DNA immunization was discovered in early 1990s, and its use has been expanded from vaccine studies to a broader range of biomedical research areas, such as the generation of high-quality polyclonal and monoclonal antibodies as research reagents. In this unit, three common DNA immunization methods are described: needle injection, electroporation, and gene gun. In addition, several common considerations related to DNA immunization are discussed.

Post-translational intracellular trafficking determines the type of immune response elicited by DNA vaccines expressing Gag antigen of Human Immunodeficiency Virus Type 1 (HIV-1)

In the current study, immune responses induced by Gag DNA vaccines with different designs were evaluated in Balb/C mice. The results demonstrated that the DNA vaccine with the full length wild type gag gene (Wt-Gag) mainly produced Gag antigens intracellularly and induced a higher level of cell-mediated immune (CMI) responses, as measured by IFN-gamma ELISPOT, intracellular cytokine staining (ICS), and cytotoxic T lymphocytes (CTL) assays against a dominant CD8(+) T cell epitope (AMQMLKETI). In contrast, the addition of a tissue plasminogen activator (tPA) leader sequence significantly improved overall Gag protein expression/secretion and Gag-specific antibody responses; however, Gag-specific CMI responses were decreased. The mutation of zinc-finger motif changed Gag protein expression patterns and reduced the ability to generate both CMI and antibody responses against Gag. These findings indicate that the structure and post-translational processing of antigens expressed by DNA vaccines play a critical role in eliciting optimal antibody or CMI responses.

Removing N-terminal sequences in pre-S1 domain enhanced antibody and B-cell responses by an HBV large surface antigen DNA vaccine

Although the use of recombinant hepatitis B virus surface (HBsAg) protein vaccine has successfully reduced global hepatitis B infection, there are still a number of vaccine recipients who do not develop detectable antibody responses. Various novel vaccination approaches, including DNA vaccines, have been used to further improve the coverage of vaccine protection. Our previous studies demonstrated that HBsAg-based DNA vaccines could induce both humoral and CMI responses in experimental animal models. However, one form of the the HBsAg antigen, the large S antigen (HBs-L), expressed by DNA vaccine, was not sufficiently immunogenic in eliciting antibody responses. In the current study, we produced a modified large S antigen DNA vaccine, HBs-L(T), which has a truncated N-terminal sequence in the pre-S1 region. Compared to the original HBs-L DNA vaccine, the HBs-L(T) DNA vaccine improved secretion in cultured mammalian cells and generated significantly enhanced HBsAg-specific antibody and B cell responses. Furthermore, this improved HBsL DNA vaccine, along with other HBsAg-expressing DNA vaccines, was able to maintain predominantly Th1 type antibody responses while recombinant HBsAg protein vaccines produced in either yeast or CHO cells elicited mostly Th2 type antibody responses. Our data indicate that HBsAg DNA vaccines with improved immunogenicity offer a useful alternative choice to recombinant protein-based HBV vaccines, particularly for therapeutic purposes against chronic hepatitis infection where immune tolerance led to poor antibody responses to S antigens.

A human-derived protein SBP (HBsAg-binding protein) can bind to hepatitis B virus surface antigen (HBsAg) and enhance the immune response to hepatitis B virus (HBV) vaccine

A high titer of antibody to HBsAg (Hepatitis B virus surface antigen) (anti-HBs) is a requisite for the prevention of HB (Hepatitis B), and adjuvants generally play a great role in eliciting special anti-HBs to HB vaccine. However, adjuvants still need to be improved because of their shortages such as unremarkable efficacy, undesirable side effect or poor security. In this study, we used HBsAg separated from HB patient sera to screen a human liver cDNA expression library, and found a novel HBsAg-binding protein (SBP), which is located at the human chromosome 14q32.33 and is similar to human IgG heavy chain in structure. Western blot demonstrated that SBP existed in both healthy human sera and HB patient sera. Furthermore, SBP could bind to HBsAg by its N-terminal domain. Notably, we confirmed that SBP could promote dendritic cells (DC) to phagocytize HBsAg more effectively and enhance the immunogenicity of HB vaccine, when SBP was mixed proportionally with HBsAg and the resulting mixture was infused into mice. These results suggest that SBP could be developed into a safe and promising adjuvant of HB vaccine.

Polyvalent DNA vaccines expressing HA antigens of H5N1 influenza viruses with an optimized leader sequence elicit cross-protective antibody responses

Highly pathogenic avian influenza A (HPAI) H5N1 viruses are circulating among poultry populations in parts of Asia, Africa, and the Middle East, and have caused human infections with a high mortality rate. H5 subtype hemagglutinin (HA) has evolved into phylogenetically distinct clades and subclades based on viruses isolated from various avian species. Since 1997, humans have been infected by HPAI H5N1 viruses from several clades. It is, therefore, important to develop strategies to produce protective antibody responses against H5N1 viruses from multiple clades or antigenic groups. In the current study, we optimized the signal peptide design of DNA vaccines expressing HA antigens from H5N1 viruses. Cross reactivity analysis using sera from immunized rabbits showed that antibody responses elicited by a polyvalent formulation, including HA antigens from different clades, was able to elicit broad protective antibody responses against multiple key representative H5N1 viruses across different clades. Data presented in this report support the development of a polyvalent DNA vaccine strategy against the threat of a potential H5N1 influenza pandemic.

Chloroplast-derived vaccines against human diseases: achievements, challenges and scopes

Infectious diseases represent a continuously growing menace that has severe impact on health of the people worldwide, particularly in the developing countries. Therefore, novel prevention and treatment strategies are urgently needed to reduce the rate of these diseases in humans. For this reason, different options can be considered for the production of affordable vaccines. Plants have been proved as an alternative expression system for various compounds of biological importance. Particularly, plastid genetic engineering can be potentially used as a tool for cost-effective vaccine production. Antigenic proteins from different viruses and bacteria have been expressed in plastids. Initial immunological studies of chloroplast-derived vaccines have yielded promising results in animal models. However, because of certain limitations, these vaccines face many challenges on production and application level. Adaptations to the novel approaches are needed, which comprise codon usage and choice of proven expression cassettes for the optimal yield of expressed proteins, use of inducible systems, marker gene removal, selection of specific antigens with high immunogenicity and development of tissue culture systems for edible crops to prove the concept of low-cost edible vaccines. As various aspects of plant-based vaccines have been discussed in recent reviews, here we will focus on certain aspects of chloroplast transformation related to vaccine production against human diseases.

Profiles of B and T cell immune responses elicited by different forms of the hepatitis B virus surface antigen

Gene-based hepatitis B virus (HBV) vaccines have been proposed as a novel approach to improve the immunogenicity toward non-responders and to allow for protection against potential viral escape mutants. Furthermore, there is significant interest in using DNA or viral vector vaccines to serve as therapeutic agents to treat chronic HBV infections that are resistant to existing drug therapies. However, the key protective antigen of HBV, the surface protein (HBsAg), can be expressed in three different sizes due to its multiple translational initiation sites: small, middle, and large forms of HBsAg. It is not clear whether the immunogenicity of these HBsAg is same, especially their ability to elicit HBsAg-specific B cell and T cell immune responses in addition to the traditional serum HBsAg-specific antibody responses. In the current study, the immunogenicity of three forms of HBsAg DNA vaccines was analyzed individually in a mouse model. Our results indicated that different forms of the HBsAg have unique immunogenicity profiles and this information is useful for the selection of optimal gene-based HBV vaccines for further improved prophylactic and therapeutic applications.