Enhanced mucosal immune responses induced by a combined candidate mucosal vaccine based on Hepatitis A virus and Hepatitis E virus structural proteins linked to tuftsin

The Re-Emergence of Hepatitis E Virus in Europe and Vaccine Development

Hepatitis E virus (HEV) is one of the leading causes of acute viral hepatitis. Transmission of HEV mainly occurs via the fecal-oral route (ingesting contaminated water or food) or by contact with infected animals and their raw meat products. Some animals, such as pigs, wild boars, sheep, goats, rabbits, camels, rats, etc., are natural reservoirs of HEV, which places people in close contact with them at increased risk of HEV disease. Although hepatitis E is a self-limiting infection, it could also lead to severe illness, particularly among pregnant women, or chronic infection in immunocompromised people. A growing number of studies point out that HEV can be classified as a re-emerging virus in developed countries. Preventative efforts are needed to reduce the incidence of acute and chronic hepatitis E in non-endemic and endemic countries. There is a recombinant HEV vaccine, but it is approved for use and commercially available only in China and Pakistan. However, further studies are needed to demonstrate the necessity of applying a preventive vaccine and to create conditions for reducing the spread of HEV. This review emphasizes the hepatitis E virus and its importance for public health in Europe, the methods of virus transmission and treatment, and summarizes the latest studies on HEV vaccine development.

A combined inactivated cholera and hepatitis A vaccine-induced potent protective immunity in a mouse model

Cholera and hepatitis A are serious infections spread by consuming contaminated food or water. Vaccination is the most effective strategy to prevent them. Inactivated vaccines are available for both diseases. Our goal in this study is to evaluate the immunogenic response of hepatitis A and cholera combination vaccines compared to the separate vaccines. Hepatitis A and cholera vaccine formulations with and without adjuvants (alum or chitosan) were developed and injected into mice intraperitoneally. We measured the rate of seroconversion; serum-specific antibody titers; lymphoproliferation analysis; cytokine secretions for IL2, IL4, IL10, and IFN-; and a challenge test against cholera strains in the vaccinated mice. Based on the results, the combined vaccination formulation, whether adjuvanted or not, significantly boosted the immune response on both humoral and cellular levels against both hepatitis A and cholera antigens compared to the individual vaccines. These findings validated an important concept for developing an effective combined cholera and hepatitis A vaccine that could be introduced as a novel combined vaccine for travelers as part of a standard immunization schedule. KEY POINTS: • Cholera and hepatitis A combined vaccines (with or without adjuvants) were prepared. • The vaccines were injected into mice groups for humoral and cellular immunity evaluation. • Combined vaccines gave substantial protection against both immunogens.

Targeted Drug Delivery Using Tuftsin-bearing Liposomes: Implications in the Treatment of Infectious Diseases and Tumors

Tuftsin, a tetrapeptide (Thr-Lys-Pro-Arg), acts as an immunopotentiating molecule with its ability to bind and activate many immune cells, including macrophages or monocytes, neutrophils and dendritic cells. The specific targeting activity of tuftsin has been further increased by its palmitoylation followed by its incorporation into the lipid bilayer of liposomes. Tuftsin-bearing liposomes (Tuft-liposomes) possess several characteristics that enable them to act as a potential drug and vaccine carriers. Tuft-liposomes-loaded anti-microbial drugs have been shown to be highly effective against many infectious diseases, including tuberculosis, leishmaniasis, malaria, candidiasis and cryptococosis. Moreover, Tuft-liposomes also increased the activity of anticancer drug etoposide against fibrosarcoma in mice. Tuft-liposomes showed the immune-potentiating effect and rejuvenated the immune cells in the leukopenic mice. In addition, antigens encapsulated in Tuftsin-bearing liposomes demonstrated greater immunogenicity by increasing the T cell proliferation and antibody secretion. Keeping into consideration their specific targeting and immunopotentiating effects, Tuft-liposomes may potentially be used as promising drug and vaccine delivery systems.

Hepatitis E Virus Infection: Circulation, Molecular Epidemiology, and Impact on Global Health

Infection with hepatitis E virus (HEV) represents the most common source of viral hepatitis globally. Although infecting over 20 million people annually in endemic regions, with major outbreaks described since the 1950s, hepatitis E remains an underestimated disease. This review gives a current view of the global circulation and epidemiology of this emerging virus. The history of HEV, from the first reported enteric non-A non-B hepatitis outbreaks, to the discovery of the viral agent and the molecular characterization of the different human pathogenic genotypes, is discussed. Furthermore, the current state of research regarding the virology of HEV is critically assessed, and the challenges towards prevention and diagnosis, as well as clinical risks of the disease described. Together, these points aim to underline the significant impact of hepatitis E on global health and the need for further in-depth research to better understand the pathophysiology and its role in the complex disease manifestations of HEV infection.

Immunological evaluation of fusion protein of Brugia malayi abundant larval protein transcript-2 (BmALT-2) and Tuftsin in experimental mice model

Introduction

Filariasis, a neglected tropical helminth disease needs vaccine besides mass drug administration for its successful eradication.

Methods

An attempt was made to produce a fusion protein (P-TUFT-ALT-2) of abundant larval transcript protein-2 and Tuftsin to enhance its immunogenicity. The fusion construct was expressed in Pichia pastoris, a nonexpensive commercial expression system. This study focused on the evaluation of immunological response produced by P-TUFT-ALT-2 in Balb/c mice.

Result and discussion

P-TUFT-ALT-2 showed an enhanced IgG peak titre compared to E. coli expressed E-ALT-2 and P. pastoris expressed P-ALT-2. IgG2b, IgG2a and IgG1 production were predominant indicating a balanced Th1/Th2 response. P-TUFT-ALT-2 also induced about 28% and 9.5% higher splenocyte proliferation over control and E-ALT-2 respectively. Splenocytes produced predominant IFN-γ followed by IL-5, IL-2 and IL-10 specifying a balanced Th1/Th2 response. P-TUFT-ALT-2 showed 55% to 80% with an average of 65% cytotoxicity in B. malayi L3 larvae in in vitro ADCC assay.

Conclusion

This experiment validates P-TUFT-ALT-2 as a potential vaccine candidate for human lymphatic filariasis.

Peptide Vaccines: New Trends for Avoiding the Autoimmune Response

Background:

Several marketed antiviral vaccines (such as that against hepatitis virus A and/or B, influenza virus, human papillomavirus, yellow fever virus, measles, rubella and mumps viruses) may elicit various autoimmune reactions.

Results:

The cause of autoimmune response due to vaccination may be: 1. the adjuvant which is regularly added to the vaccine (especially in the case of various oil substrates), 2. the specific viral component itself (a protein or glycoprotein potentially possessing cross-reactive epitopes) and/or 3. contamination of the vaccine with traces of non-viral proteins mostly cellular in origin. Believing that peptide vaccines might represent an optimal solution for avoiding the above-mentioned problems, we discuss the principles of rational design of a typical peptide vaccine which should contain oligopeptides coming either from the selected structural virion components (i.e.capsid proteins and/or envelop glycoproteins or both) or from the virus-coded non-structural polypeptides. The latter should be equally immunogenic as the structural virus proteins. Describing the feasibility of identification and design of immunogenic epitopes, our paper also deals with possible problems of peptide vaccine manufacturing. The presented data are in part based on the experience of our own, in part, they are coming from the results published by others.

Conclusion:

Any peptide vaccine should be able to elicit relevant and specific antibody formation, as well as an efficient cell-mediated immune response. Consequently, the properly designed peptide vaccine is expected to consist of carefully selected viral peptides, which should stimulate the receptors of helper T/CD4 cells as well as of cytotoxic (T/CD8) lymphocytes.

Development of new hepatitis E vaccines

Hepatitis E virus (HEV) infection is an emerging zoonotic disease posing a severe threat to public health in the world, especially to pregnant women. Currently, no specific treatments are available for HEV infection. Therefore, it is crucial to develop vaccine to prevent this infection. Although several potential candidate vaccines against HEV have been studied for their immunogenicity and efficacy, only Hecolin® which is developed by Xiamen Innovax Biotech Co., Ltd. and approved by China Food and Drug Administration (CFDA) in 2012, is the licensed HEV vaccine in the world so far. Extensive studies on safety, immunogenicity and efficacy in phase III clinical trials have shown that Hecolin® is a promising vaccine for HEV prevention and control. In this article, the advances on HEV vaccine development and research are briefly reviewed.

Elucidation of immunological response and its regulatory network by P-TUFT-ALT-2: a promising fusion protein vaccine for human lymphatic filariasis

Human lymphatic filariasis, a mosquito-borne neglected tropical parasitic disease, needs an early development of prophylactic agents such as a vaccine for its successful elimination. Our earlier study suggested the enhanced immunological response by fusion protein (P-TUFT-ALT-2) of Tuftsin and ALT-2 in a mice model. We cultured human peripheral blood mononuclear cells (PBMCs) and treated cells with Escherichia coli-expressed ALT-2 (E-ALT-2) and P-TUFT-ALT-2. Real-time polymerase chain reaction was performed to identify the mRNA copy number of various cytokine and transcription factor genes. The recombinant vaccine candidate was also validated for humans by immunoreactivity with human sera samples of natural infection. In this study, P-TUFT-ALT-2 stimulated 12% higher PBMC proliferation in endemic normal (EN) individuals than E-ALT-2 alone. There was enhanced production of IFN γ, IL-2, IL-5 and IL-12, indicating a balanced Th1/Th2 response. However, higher expression of IL-5 and lower IL-4 validate the humoral response through an IL-5-dependent manner. Also, high level of IL-17 indicates a strong Th/Treg regulation over T-cell activation. The upregulated T-bet might have enhanced IFN-γ production, whereas GATA-3 was supposed to enhance IL-5 expression. The fusion protein also exhibited 15-16% higher reactivity with EN clinical sera, exposing the upregulation of IgG1 and IgM in natural infection. The higher reactivity of P-TUFT-ALT-2 with sera of natural infection (EN) was validated indirectly by B-cell activation through various cytokines and regulatory genes produced from different T cells. Thus, these findings endorse P-TUFT-ALT-2 as a potential vaccine candidate for human lymphatic filariasis.

A Recombinant HAV Expressing a Neutralization Epitope of HEV Induces Immune Response against HAV and HEV in Mice

Hepatitis A virus (HAV) and hepatitis E virus (HEV) are causative agents of acute viral hepatitis transmitted via the fecal–oral route. Both viruses place a heavy burden on the public health and economy of developing countries. To test the possibility that HAV could be used as an expression vector for the development of a combination vaccine against hepatitis A and E infections, recombinant HAV-HEp148 was created as a vector to express an HEV neutralization epitope (HEp148) located at aa 459–606 of the HEV capsid protein. The recombinant virus expressed the HEp148 protein in a partially dimerized state in HAV-susceptible cells. Immunization with the HAV-HEp148 virus induced a strong HAV- and HEV-specific immune response in mice. Thus, the present study demonstrates a novel approach to the development of a combined hepatitis A and E vaccine.

Specific memory B cell response and participation of CD4+ central and effector memory T cells in mice immunized with liposome encapsulated recombinant NE protein based Hepatitis E vaccine candidate

BACKGROUND

Liposome encapsulated neutralizing epitope protein of Hepatitis E virus (HEV), rNEp, our Hepatitis E vaccine candidate, was shown to be immunogenic and safe in pregnant and non-pregnant mice and yielded sterilizing immunity in rhesus monkeys.

METHODS

The current study in Balb/c mice assessed the levels and persistence of anti-HEV IgG antibodies by ELISA, frequencies of B, memory B, T and memory T cells by flow cytometry and HEV-specific IgG secreting memory B cells by ELISPOT till 420days post immunization (PI) with 5?g rNEp encapsulated in liposome based adjuvant (2 doses, 4weeks apart). Mice immunized with a lower dose (1?g) were assessed only for anamnestic response post booster dose.

RESULTS

Vaccine candidate immunized mice (5?g dose) elicited strong anti-HEV IgG response that was estimated to persist for lifetime. At day 120 PI, frequency of memory B cells was higher in immunized mice than those receiving adjuvant alone. Anti-HEV IgG titers were lower in mice immunized with 1?g dose. A booster dose yielded a heightened antibody response in mice with both high (>800GMT, 5?g) and low (?100GMT, 1?g) anti-HEV IgG titers. At day 6th post booster dose, HEV-specific antibody secreting plasma cells (ASCs) were detected in 100% and 50% of mice with high and low anti-HEV IgG titers, respectively, whereas the frequencies of CD4⁺ central and effector memory T cells were high in mice with high anti-HEV IgG titers only.

CONCLUSIONS

Taken together, the vaccine candidate effectively generates persistent and anamnestic antibody response, elicits participation of CD4⁺ memory T cells and triggers memory B cells to differentiate into ASCs upon boosting. This approach of assessing the immunogenicity of vaccine candidate could be useful to explore the longevity of HEV-specific memory response in future HEV vaccine trials in human.

Responses of primary human nasal epithelial cells to EDIII-DENV stimulation: the first step to intranasal dengue vaccination

Background

About half of the world’s population are living in the endemic area of dengue viruses implying that a rapid-mass vaccination may be required. In addition, a major target of dengue vaccine are children, thus, a needle-free administration is more attractive. These problems may be overcome by the alternative route of vaccination such as topical, oral and intranasal vaccination. Here, we investigated the possibility to deliver a dengue immunogen intranasally, a painless route of vaccination. The tested immunogen was the domain III of dengue serotype-3 E protein (EDIII-D3) loaded into trimethyl chitosan nanoparticles (EDIII-D3 TMC NPs). The primary human nasal epithelial cells, HNEpCs, were used as an in vitro model for nasal responses.

Results

At tested concentrations, EDIII-D3 TMC NPs not only exerted no detectable toxicity toward HNEpC cultures but also efficiently delivered EDIII-D3 immunogens into HNEpCs. Moreover, HNEpCs quickly and strongly produced proinflammatory cytokines (IL-1β, IL-6, TNF-α), type-I IFN, the growth factors (GM-CSF, IL-7), the chemokines (MCP-1, MIP-1β, IL-8), Th1-related cytokines (IL-2, IL-12p70, IL-17, IFN-γ) and Th2-related cytokine (IL-4) in response to EDIII-D3 TMC NPs treatment.

Conclusions

A potential mucosal delivery system for dengue immunogens was revealed and found to stimulate a strong local innate antiviral response which possibly leading to a systemic adaptive immunity.

Ex-vivo evaluation of the mucoadhesive properties of Cedrela odorata and Khaya senegalensis gums with possible applications for veterinary vaccine delivery

Background

Few studies have investigated the interaction of bioadhesives with biologic tissues for veterinary application. Hence, this study evaluates the mucoadhesive property and vaccine delivery properties of polymers from phytogenic origin. Gums from Cedrela odorata and Khaya senegalensis were harvested, purified, dried and compressed into 500 mg tablets individually and in combined ratios. The time taken for these tablets, placed on freshly excised (5 × 5 cm) trachea and duodenal tissues of cattle, chicken, pig, sheep and goat and fastened to the basket end of a tablet dissolution machine probe set at 50 rev/min in a phosphate buffer 6.8 pH at 37 °C, to fall off the tissue was the peak adhesion time (PAT). Gum with best PAT was combined with Newcastle disease vaccine and the procedure repeated. Haemagglutination assay (HA) was conducted on the gum polymer-vaccine mix with gum and vaccine individually as controls.

Results

On intestinal and trachea tissues, Cedrela gum polymer averagely had prolonged PAT (≈1 h 30 min and 1 h respectively) while average PAT values of Khaya gums followed the same trend but too transient PAT (≈6 and 0.3 min respectively). However on combination, Cedrela–Khaya polymer mix (1:1) was best on chicken, cattle and sheep trachea and intestinal tissues (PAT of 1 h 30 min and 2 h 24 min respectively). On combination with vaccine, the PAT of the gums reduced slightly on cattle and sheep tissues while other animal tissue showed varied results. The HA results showed the gum polymer boosted the HA property of the vaccine (Log 10⁵), when compared to vaccine alone (Log 10⁴).

Conclusion

Hence, mucoadhesives from phytogenic sources have potential for non-invasive vaccine application.

Differential Immune Responses in Mice Immunized with Recombinant Neutralizing Epitope Protein of Hepatitis E Virus Formulated with Liposome and Alum Adjuvants

In the developing countries, Hepatitis E virus (HEV) is a predominant cause of sporadic acute hepatitis in adults and waterborne epidemics leading to high mortality in pregnant women. Vaccine development mainly focuses on the structural capsid protein open-reading-frame-2 (ORF-2) of the virus. We successfully evaluated liposome-adjuvanted recombinant neutralizing epitope protein (rNEp), a part of ORF-2, 458-607aa, in mice and rhesus macaques. We compared immune response to adjuvants alone, rNEp alone, or adjuvanted with liposome (lipo-rNEp)/alum (al-rNEp) in mice following intramuscular administration of two doses of 5 μg each. IgG anti-HEV titers (enzyme-linked immunosorbent assay), immunophenotyping (flow cytometry, CD3(+)CD4(+), CD3(+)CD8(+), CD11c(+), CD11b(+), CD19(+) cells; costimulatory markers CD80, CD86, MHC-I, MHC-II, and early activation marker CD69), and levels of Th1/Th2 cytokines (IL-2/IFN-γ/IL-4/IL-5 and additionally IL-1β/IL-6/IL-10/TNF for early time points) were determined at early (4/12/24-h postdose-1) and later time points (2 weeks post-both doses). IgG anti-HEV titers were higher in the lipo-rNEp group than al-rNEp post-both doses (p < 0.05). At early time points, cell type proportions were comparable at the site of injection; IL-Iβ levels increased in lipo-rNEp, 24 h, while IL-6 levels rose in lipo-rNEp/al-rNEp/alum-alone groups, 4 h, compared to controls. In the draining lymph nodes (DLNs), CD11c(+)CD86(+) cells increased at 24 h in liposome-alone/lipo-rNEp groups. A rise in the CD11c(+)CD69(+) cells was noted in the lipo-rNEp group compared to other groups (p < 0.05). Cytokine levels in the spleen/sera remained unchanged in all the groups (p > 0.05). At 2 weeks postdose-2, CD11c(+)MHC-II(+)/CD11b(+)MHC-II(+) cells increased in the spleen in the lipo-rNEp and al-rNEp groups, respectively. In the DLNs, CD19(+)MHC-II(+) cells increased in rNEp/al-rNEp/lipo-rNEp groups post-both doses and CD11c(+)CD86(+) cells in the lipo-rNEp group. A balanced Th1/Th2 response was evident in the lipo-rNEp, while a Th2 bias was noted in al-rNEp. Different immune response gene clustering patterns were noted in uncultured spleens from immunized mice and cultured-stimulated splenocytes. In conclusion, lipo-rNEp is a better immunogen, works through dendritic cells, and elicits a balanced Th1/Th2 response, while alum functions through macrophages and induces a Th2 response.

Molecular modelling, synthesis and biological evaluation of peptide inhibitors as anti-angiogenic agent targeting neuropilin-1 for anticancer application

Vascular endothelial growth factor (VEGF) and its co-receptor neuropilin-1 (NRP-1) are important targets of many pro-angiogenic factors. In this study, nine peptides were synthesized and evaluated for their molecular interaction with NRP-1 and compared to our previous peptide ATWLPPR. Docking study showed that the investigated peptides shared the same binding region as shown by tuftsin known to bind selectively to NRP-1. Four pentapeptides (DKPPR, DKPRR, TKPPR and TKPRR) and a hexapeptide CDKPRR demonstrated good inhibitory activity against NRP-1. In contrast, peptides having arginine residue at sites other than the C-terminus exhibited low activity towards NRP-1 and this is confirmed by their inability to displace the VEGF₁₆₅ binding to NRP-1. Docking study also revealed that replacement of carboxyl to amide group at the C-terminal arginine of the peptide did not affect significantly the binding interaction to NRP-1. However, the molecular affinity study showed that these peptides have marked reduction in the activity against NRP-1. Pentapeptides having C-terminal arginine showed strong interaction and good inhibitory activity with NRP thus may be a good template for anti-angiogenic targeting agent.

Specific IgA Enhances the Transcytosis and Excretion of Hepatitis A Virus

Hepatitis A virus (HAV) replicates in the liver, and is excreted from the body in feces. However, the mechanisms of HAV transport from hepatocytes to the gastrointestinal tract are poorly understood, mainly due to lack of suitable in vitro models. Here, we use a polarized hepatic cell line and in vivo models to demonstrate vectorial transport of HAV from hepatocytes into bile via the apical cell membrane. Although this transport is specific for HAV, the rate of fecal excretion in inefficient, accounting for less than 1% of input virus from the bloodstream per hour. However, we also found that the rate of HAV excretion was enhanced in the presence of HAV-specific IgA. Using mice lacking the polymeric IgA receptor (pIgR^−/−), we show that a proportion of HAV:IgA complexes are transported via the pIgR demonstrating a role for specific antibody in pathogen excretion.