Immunization with the glutathione S-transferase Sj26GST with Chi-CpG NP against Schistosoma japonicum in mice.

Schistosomiasis caused by Schistosoma japonicum (S. japonicum) is a major public health problem in the Philippines, China and Indonesia. In this study, the immunopotentiator CpG-ODN was encapsulated within chitosan nanoparticles (Chi NPs) to create a combination adjuvant (Chi-CpG NP). This approach was employed to enhance the immunogenicity of 26 kDa glutathione S-transferase (Sj26GST) from S. japonicum through intranasal immunization. The results demonstrated higher levels of specific anti-Sj26GST antibodies and Sj26GST-specific splenocyte proliferation compared to mice that were immunized with Sj26GST + Chi-CpG NP. Cytokine analysis of splenocytes revealed that the Sj26GST + Chi-CpG NP induced a slight Th1-biased immune response, with increased production of IFN-γ by CD4+ T-cells in the spleen. Subsequently, mice were intradermally inoculated with 1 × 107 organisms in the Coeliac cavity. The bacterial organ burden detected in the liver of immunized mice suggested that Sj26GST + Chi-CpG NP enhances protective immunity to inhibit S. japonicum colonization. Therefore, Sj26GST + Chi-CpG NP vaccination enhances Sj26GST-specific immunogenicity and provides protection against S. japonicum.

Characterization of T cell responses to co-administered hookworm vaccine candidates Na-GST-1 and Na-APR-1 in healthy adults in Gabon.

Two hookworm vaccine candidates, Na-GST-1 and Na-APR-1, formulated with Glucopyranosyl Lipid A (GLA-AF) adjuvant, have been shown to be safe, well tolerated, and to induce antibody responses in a Phase 1 clinical trial (Clinicaltrials.gov NCT02126462) conducted in Gabon. Here, we characterized T cell responses in 24 Gabonese volunteers randomized to get vaccinated three times with Na-GST-1 and Na-APR-1 at doses of 30µg (n = 8) or 100µg (n = 10) and as control Hepatitis B (n = 6). Blood was collected pre- and post-vaccination on days 0, 28, and 180 as well as 2-weeks after each vaccine dose on days 14, 42, and 194 for PBMCs isolation. PBMCs were stimulated with recombinant Na-GST-1 or Na-APR-1, before (days 0, 28 and 180) and two weeks after (days 14, 42 and 194) each vaccination and used to characterize T cell responses by flow and mass cytometry. A significant increase in Na-GST-1 -specific CD4+ T cells producing IL-2 and TNF, correlated with specific IgG antibody levels, after the third vaccination (day 194) was observed. In contrast, no increase in Na-APR-1 specific T cell responses were induced by the vaccine. Mass cytometry revealed that, Na-GST-1 cytokine producing CD4+ T cells were CD161+ memory cells expressing CTLA-4 and CD40-L. Blocking CTLA-4 enhanced the cytokine response to Na-GST-1. In Gabonese volunteers, hookworm vaccine candidate, Na-GST-1, induces detectable CD4+ T cell responses that correlate with specific antibody levels. As these CD4+ T cells express CTLA-4, and blocking this inhibitory molecules resulted in enhanced cytokine production, the question arises whether this pathway can be targeted to enhance vaccine immunogenicity.

Induction of Immunogenic Response in BALB/c Mice by Live and Killed Form of Recombinant Lactococcus lactis Displaying EG95 of Echinococcus granulosus.

Background: Cystic echinococcosis is a zoonotic parasitic infection caused by Echinococcus granulosus worldwide and is associated with economic losses among livestock animals. EG95 is an immunogenic antigen from the E. granulosus. Lactococcus lactis has been prested as a safe vehicle for antigen delivery. The goal of this study was to design a novel L. lactis strain displaying EG95 as a vaccine delivery system. Methods: The eg95 encoding gene fragment fused to the M6 anchoring protein was cloned into the pNZ7021 vector, and L. lactis NZ9000 displaying recombinant EG95 was constructed. The expression of an approximately 32-kDa EG95 protein was confirmed by Western blotting and immunofluorescence analysis. The immune responses were evaluated in BALB/c mice immunized orally and subcutaneously with the live and killed recombinant L. lactis, respectively. Results: Total IgG level in mice immunized with heat-killed recombinant L. lactis (pNZ7021-eg95) significantly increased compared to the control group. Mucosal IgA was significantly higher in mice received live recombinant L. lactis (pNZ7021-eg95) compared to the control mice. Splenic lymphocytes from immunized mice represented the high levels of IFN-γ and the low-levels of IL-4 and IL-10. Conclusion: Our results indicate that immunization with EG95-expressing L. lactis can induce both specific humoral and cellular immune responses in mice.

lncRNA028466 regulates Th1/Th2 cytokine expression and associates with Echinococcus granulosus antigen P29 immunity.

BACKGROUND: Cystic echinococcosis (CE) is a parasitic disease that is caused by Echinococcus granulosus (Eg). The recombinant Echinococcus granulosus antigen P29 (rEg.P29) was shown to confer effective immunity to sheep and mice during E. granulosus secondary infection in our previous study. In this study, we sought to investigate the ability of long noncoding RNA 028466 (lncRNA028466) as a regulator for the protective immunity mediated by rEg.P29 vaccination and to study the effects of lncRNA028466 on CD4+T cell differentiation in mice spleen. METHODS: Female BALB/c mice were divided into two groups and were vaccinated subcutaneously with rEg.P29 antigen and PBS as a control (12 mice each group). Following prime-boost vaccination, CD4+T, CD8+T, and B cells from the spleen were isolated by flow cytometry. Quantitative real-time PCR (qRT-PCR) was performed to measure the expression of lncRNA028466 in these three kinds of cells. Then, lncRNA028466 was overexpressed and knocked down in naive CD4+T cells, and Th1 and Th2 cytokine expression was detected. qRT-PCR, western blot, and ELISA were performed to evaluate the production of IFN-γ, IL-2, IL-4, and IL-10, and flow cytometry was performed to detect the differentiation of Th1 and Th2 subgroups. RESULTS: lncRNA028466 was significantly decreased after the second week of immunization with rEg.P29 antigen. The proportion of CD4+ T cells was increased after rEg.P29 immunization. Overexpression of lncRNA028466 facilitated the production of IL-4, IL-10 and suppressed the production of IFN-γ, IL-2. Furthermore, after transfection with siRNA028466, IL-2 production was facilitated and IL-10 production was suppressed in naive CD4+ T cells. CONCLUSIONS: Immunization with rEg.P29 downregulated the expression of lncRNA028466, which was related to a higher Th1 immune response and a lower Th2 immune response. Our results suggest that lncRNA028466 may be involved in rEg.P29-mediated immune response by regulating cytokine expression of Th1 and Th2.

ASCVac-1, a Multi-Peptide Chimeric Vaccine, Protects Mice Against Ascaris suum Infection.

Control of human ascariasis, the most prevalent neglected tropical disease globally affecting 450 million people, mostly relies on mass drug administration of anthelmintics. However, chemotherapy alone is not efficient due to the high re-infection rate for people who live in the endemic area. The development of a vaccine that reduces the intensity of infection and maintains lower morbidity should be the primary target for infection control. Previously, our group demonstrated that immunization with crude Ascaris antigens in mice induced an IgG-mediated protective response with significant worm reduction. Here, we aimed to develop a multipeptide chimera vaccine based on conserved B-cell epitopes predicted from 17 common helminth proteomes using a bioinformatics algorithm. More than 480 B-cell epitopes were identified that are conserved in all 17 helminths. The Ascaris-specific epitopes were selected based on their reactivity to the pooled sera of mice immunized with Ascaris crude antigens or infected three times with A. suum infective eggs. The top 35 peptides with the strongest reactivity to Ascaris immune serum were selected to construct a chimeric antigen connected in sequence based on conformation. This chimera, called ASCVac-1, was produced as a soluble recombinant protein in an Escherichia coli expression system and, formulated with MPLA, was used to immunize mice. Mice immunized with ASCVac-1/MPLA showed around 50% reduced larvae production in the lungs after being challenged with A. suum infective eggs, along with significantly reduced inflammation and lung tissue/function damage. The reduced parasite count and pathology in infected lungs were associated with strong Th2 immune responses characterized by the high titers of antigen-specific IgG and its subclasses (IgG1, IgG2a, and IgG3) in the sera and significantly increased IL-4, IL-5, IL-13 levels in lung tissues. The reduced IL-33 titers and stimulated eosinophils were also observed in lung tissues and may also contribute to the ASCVac-1-induced protection. Taken together, the preclinical trial with ASCVac-1 chimera in a mouse model demonstrated its significant vaccine efficacy associated with strong IgG-based Th2 responses, without IgE induction, thus reducing the risk of an allergic response. All results suggest that the multiepitope-based ASCVac-1 chimera is a promising vaccine candidate against Ascaris sp. infections.

Arachidonic Acid Is a Safe and Efficacious Schistosomicide, and an Endoschistosomicide in Natural and Experimental Infections, and Cysteine Peptidase Vaccinated Hosts.

Blood flukes of the genus Schistosoma are covered by a protective heptalaminated, double lipid bilayer surface membrane. Large amounts of sphingomyelin (SM) in the outer leaflet form with surrounding water molecules a tight hydrogen bond barrier, which allows entry of nutrients and prevents access of host immune effectors. Excessive hydrolysis of SM to phosphoryl choline and ceramide via activation of the parasite tegument-associated neutral sphingomyelinase (nSMase) with the polyunsaturated fatty acid, arachidonic acid (ARA) leads to parasite death, via allowing exposure of apical membrane antigens to antibody-dependent cell-mediated cytotoxicity (ADCC), and accumulation of the pro-apoptotic ceramide. Surface membrane nSMase represents, thus, a worm Achilles heel, and ARA a valid schistosomicide. Several experiments conducted in vitro using larval, juvenile, and adult Schistosoma mansoni and Schistosoma haematobium documented ARA schistosomicidal potential. Arachidonic acid schistosomicidal action was shown to be safe and efficacious in mice and hamsters infected with S. mansoni and S. haematobium, respectively, and in children with light S. mansoni infection. A combination of praziquantel and ARA led to outstanding cure rates in children with heavy S. mansoni infection. Additionally, ample evidence was obtained for the powerful ARA ovocidal potential in vivo and in vitro against S. mansoni and S. haematobium liver and intestine eggs. Studies documented ARA as an endogenous schistosomicide in the final mammalian and intermediate snail hosts, and in mice and hamsters, immunized with the cysteine peptidase-based vaccine. These findings together support our advocating the nutrient ARA as the safe and efficacious schistosomicide of the future.

Investigating Immunization With Nucleotide Enzymes of Schistosoma mansoni: Nucleoside Diphosphate Kinase and Adenylosuccinate Lyase as New Antigenic Targets Against Schistosomiasis.

Schistosomiasis, caused by Schistosoma mansoni trematode worm, affects more than 1.5 million people in Brazil. The current treatment consists in the administration of Praziquantel, the only medicine used for treatment for more than 40 years. Some of the limitations of this drug consist in its inactivity against schistosomula and parasite eggs, the appearance of resistant strains and non-prevention against reinfection. Thus, the objective of this study was to evaluate the effect of immunization with recombinant functional enzymes of the purine salvage pathway of S. mansoni, Nucleoside Diphosphate Kinase (NDPK) and Adenylosuccinate Lyase (ADSL), to evaluate the host immune response, as well as the parasite load after vaccination. For this, Balb/c mice were divided into 5 groups: control (uninfected and untreated), non-immunized/infected, NDPK infected, ADSL infected, and NDPK + ADSL infected. Immunized groups received three enzyme dosages, with a 15-day interval between each dose, and after 15 days of the last application the animals were infected with 80 cercariae of S. mansoni. On the 47th day after the infection, fecal eggs were counted and, on the 48th day after the infection, the evaluation of leukocyte response, parasite load, antibody production, cytokines quantification, and histopathological analysis were performed. The results showed that immunizations with NDPK, ADSL or NDPK + ADSL promoted a discreet reduction in eosinophil counts in lavage of peritoneal cavity. All immunized animals showed increased production and secretion of IgG1, IgG2a, and IgE antibodies. Increased production of IL-4 was observed in the group immunized with the combination of both enzymes (NDPK + ADSL). In addition, in all immunized groups there were reductions in egg counts in the liver and intestine, such as reductions in liver granulomas. Thus, we suggest that immunizations with these enzymes could contribute to the reduction of schistosomiasis transmission, besides being important in immunopathogenesis control of the disease.

Attempts to induce tolerance to Trichostrongylus colubriformis infection in sheep.

BACKGROUND AND OBJECTIVES: The possibility of manipulating the immune response in lambs to the gastrointestinal nematode Trichostrongylus colubriformis to reduce production losses associated with infection was investigated. In a series of four experiments, attempts to immunize sheep via the mucosal route to modify the immune response and induce mucosal tolerance are outlined. Initially, a proof of concept study was conducted with lambs being injected with multiple doses of a somatic T colubriformis antigen without an adjuvant in the rectal submucosa and subsequently challenged with T colubriformis L3 larvae. This was followed by a dose-response study comparing different antigen doses to identify the optimum dose of the nematode antigen for successful induction of mucosal tolerance. The final two studies were conducted to determine the larval stage specificity of the parasite antigen and the most suitable site of delivery required to stimulate mucosal tolerance. METHODS: In the proof of concept study, lambs either received repeated injections in the rectal submucosa at 3 × weekly intervals with 15 µg of L3, 11 µg of L4 and 21 µg of immature adult (L5) somatic T colubriformis antigens (ANT) or not (INF) prior to infection with T colubriformis. In the dose-rate study, antigen dose rates of 100%, 50%, 10%, 1% or 0% of the antigen concentration used in the proof of concept study were compared while the larval stage study compared antigen from either L3, L4, L5 stages or combination of all (COMB) and the route of administration study compared antigen delivery into either the rectal submucosa (RE) or sub-cutaneous injection (SC). RESULTS: During infection, lamb growth was improved by antigen treatment between days 21 and 42 in the proof of concept study (P = .009), for groups 10%, 50% and 100% in the dose-rate study (P < .05 for all) and in RE in the route of administration study with no improvement observed in the larval stage study. No differences in faecal egg counts were observed (P > .05 for all). Parasite-specific IgA and IgE showed a dose-response (the dose-rate study), were not affected by larval stage (the larval stage study) and were greater in RE than SC (the route of administration study). IL-4 production following lymphocyte stimulation was greatest in COMB (the larval stage study) and RE (the route of administration study). CONCLUSIONS: Although antigen treatment improved performance, this was inconsistent and appeared to stimulate immunity rather than induce tolerance. Combined larval stages were more efficient than individual stages, and intra-rectal administration was more effective than sub-cutaneous.

The Protective Role of Toll-Like Receptor Agonist Monophosphoryl Lipid A Against Vaccinated Murine Schistosomiasis.

PURPOSE: Schistosomiasis is a disease that afflicts over 220 million people worldwide. To date, there is no vaccine against schistosomiasis and chemotherapy relies basically on a single drug, praziquantel. The current study was undertaken to investigate the therapeutic effects of monophosphoryl lipid A (MPLA) as an adjuvant in soluble egg antigen (SEA)-vaccinated and Schistosoma mansoni-infected mice. METHODS: Mice were divided into two groups of uninfected and Schistosoma mansoni infected. The two groups were treated differently with MPLA, SEA and praziquantel. Study parameters included parasitological, immunological and biochemical parameters. RESULTS: Parasitological parameters revealed that intraperitoneal injection of MPLA into SEA-vaccinated and S. mansoni-infected mice was effective in reducing the worm and egg burden, granuloma count and diameter as well as the total area of infection in their livers versus SEA-untreated but infected ones. In addition, MPLA showed ameliorative action on the elevated liver oxidative stress marker, including malondialdehyde (MDA) and a decrease in the level of the antioxidant enzymes, reduced glutathione (GSH) and catalase (CAT) which may have a role in the liver damage and fibrosis due to S. mansoni infection. CONCLUSION: Treatment with MPLA has multi-functions in attenuating the deleterious impacts of S. mansoni infection in mice livers. Its effects are mediated through a reduction of ova count, worm burden, granuloma diameter and amelioration of antioxidant defense systems, and liver function biomarkers.

Vaccination of mice with a recombinant novel cathepsin B inhibits Trichinella spiralis development, reduces the fecundity and worm burden.

BACKGROUND: Trichinella spiralis is a major zoonotic tissue-dwelling nematode, which is a public health concern and a serious hazard to animal food safety. It is necessary to exploit an anti-Trichinella vaccine to interrupt the transmission of Trichinella infection among animals and from animals to humans. The purpose of the present study was to characterize the novel T. spiralis cathepsin B (TsCB) and to evaluate the immune protection elicited by immunization with recombinant TsCB (rTsCB). METHODS: The complete cDNA sequences of the TsCB gene were cloned, expressed and purified. The antigenicity of rTsCB was investigated by western blot analysis and ELISA. Transcription and expression of TsCB at various T. spiralis life-cycle stages were analyzed by RT-PCR and indirect immunofluorescent assay (IIFA). The mice were subcutaneously immunized with rTsCB, and serum level of TsCB-specific IgG (IgG1 and IgG2a) and IgE antibodies were assayed by ELISA. Immune protection elicited by vaccination with rTsCB was investigated. RESULTS: The TsCB was transcribed and expressed in four T. spiralis life-cycle stages (adult worm, AW; newborn larvae, NBL; muscle larvae, ML; and intestinal infective L1 larvae), it was primarily located in the cuticle and stichosome of the parasitic nematode. Vaccination of mice with rTsCB produced a prominent antibody response (high level of specific IgG and IgE) and immune protection, as demonstrated by a 52.81% AW burden reduction of intestines at six days post-infection (dpi) and a 50.90% ML burden reduction of muscles at 35 dpi after oral larva challenge. The TsCB-specific antibody response elicited by immunization with rTsCB also impeded intestinal worm growth and decreased the female fecundity. CONCLUSIONS: TsCB might be considered as a novel potential molecular target to develop vaccines against T. spiralis infection.

Anti-Ascaris suum immunoglobulin Y as a novel biotechnological tool for the diagnosis of human ascariasis.

Human ascariasis is a neglected tropical disease of great relevance to public health and is considered the most frequent helminthiasis in poor regions. Accurately diagnosing this parasite has been challenging due to limitations of current diagnostic methods. Immunoglobulin Y (IgY) technology is a very effective alternative for the production of highly specific and profitable antibodies. This study aimed to produce and apply anti-Ascaris suum IgY antibodies in the immunodiagnosis of human ascariasis. Five immunizations comprising total saline extract from A. suum adult life forms were given at 14-day intervals to Gallus gallus domesticus hens of the Isa Brown line. Eggs and blood samples were collected weekly and fortnightly, respectively, to monitor the production of antibodies. The specificity of antibodies was confirmed by dot-blot, kinetic enzyme-linked immunosorbent assay (ELISA), avidity ELISA, immunoblotting and indirect immunofluorescence antibody tests. The application for disease diagnosis was performed through the detection of immune complexes in human serum samples by sandwich ELISA. Peaks of IgY anti-A. suum production occurred at weeks 6 and 8. IgY showed high avidity levels after the second dose of immunization, ranging from 64% to 93%, with a mean avidity index of 78.30%. Purified IgY recognized 12 bands of proteins from A. suum saline extract. Eggs, the uterine portion and cuticles of A. suum female adult are reactive in immunofluorescence. The detection of immune complexes showed diagnostic values of 80% sensitivity and 90% specificity. In conclusion, specific IgY have been shown to be a potential immunodiagnostic tool with promising future applications in human ascariasis.

Intranasal immunization with recombinant Trichinella spiralis serine protease elicits protective immunity in BALB/c mice.

The aim of this study was to observe the intestinal mucosal/systemic responses triggered by intranasal vaccination using recombinant Trichinella spiralis serine protease (rTsSP) and its capacity to elicit immune protection against larva challenge in a murine model. rTsSP coupled with cholera toxin B subunit (CTB) was used to vaccinate mice via intranasal route. The results revealed that intranasal vaccination with rTsSP plus CTB elicited significantly intestinal local sIgA response and a TsSP-specific systemic antibody response in vaccinated mice. Furthermore, more goblet cells/acidic mucins and IgA-secreting cells were observed in jejunum from vaccinated mice. Anti-rTsSP immune serum strongly recognized the cuticle of various worm stages (muscle larva, intestinal infective larva and adult worm). The level of IFN-γ, IL-4 and IL-10 of rTsSP-vaccinated mice was significantly elevated relative to CTB and PBS control groups. The vaccinated mice exhibited a 71.10% adult reduction at 9 days pi and a 62.10% muscle larva reduction at 42 days pi following larva challenge. Additionally, vaccination with rTsSP also dampened intestinal T. spiralis development and decreased the female fecundity. Our results showed that intranasal vaccination using rTsSP adjuvanted with CTB triggered significantly local sIgA response and systemic concurrent Th1/Th2 response that induced an obvious protection against Trichinella infection.

A Survey on the Adjuvant Role of Naloxone Alone or Combined with Alum in Vaccination Against Fasciolosis in BALB/c Mice.

BACKGROUND: Fasciolosis is a zoonotic parasitic disease imposing a heavy load of livestock losses worldwide. PURPOSE: We aimed to evaluate immune-stimulatory effects of naloxone (NLX), an opioid receptor antagonist, in combination with alum in mice vaccinated with excretory-secretory antigens (E/S) of Fasciola hepatica. METHODS: 8-week-old female BALB/c mice were subcutaneously vaccinated using E/S antigens of F. hepatica. Experimental groups (14 mice per group) included: vaccine (E/S antigen), alum vaccine (E/S antigen plus alum), NLX vaccine (E/S antigen plus NLX), and alum-NLX vaccine (E/S antigen plus a mixture of alum-NLX). The control group was infused with PBS. Lymphocyte proliferation and the levels of IFN-γ, IL-4, IgG2a, IgG1, and total IgG were measured. RESULTS: Mice vaccinated with NLX or alum-NLX adjuvants showed significantly higher rates of lymphocyte proliferation, IFN-γ, total IgG, and IgG2a levels. The mice that were injected with alum showed a significantly higher concentration of IL-4. Ratios of IFN-γ/Il-4 and IgG2a/IgG1 were significantly higher in the NLX and alum-NLX groups in comparison with the groups vaccinated either with alum or without any adjuvant. A significantly higher protection rate (62.5%) was seen in mice vaccinated with the alum-NLX adjuvant compared to the other groups. CONCLUSION: NLX can be effective in conferring cellular immunity and protection against F. hepatica. It is recommended to consider this agent as a potential adjuvant in vaccines against fasciolosis.

Linear epitopes in Onchocerca volvulus vaccine candidate proteins and excretory-secretory proteins.

In our previous study, a proteome-wide screen was conducted to identify linear epitopes in this parasite's proteome, resulting in the discovery of three immunodominant motifs. Here, we investigated whether such antigenic peptides were found in proteins that were already known as vaccine candidates and excretome/secretome proteins for Onchocerca volvulus This approach led to the identification of 71 immunoreactive stretches in 46 proteins. A deep-dive into the immunoreactivity profiles of eight vaccine candidates that were chosen as most promising candidates for further development (Ov-CPI-2, Ov-ALT-1, Ov-RAL-2, Ov-ASP-1, Ov-103, Ov-RBP-1, Ov-CHI-1, and Ov-B20), resulted in the identification of a poly-glutamine stretch in Ov-RAL-2 that has properties for use as a serodiagnostic marker for O. volvulus infection. A peptide ELISA was developed, and the performance of this assay was evaluated. Based on this assessment, it was found that this assay has a sensitivity of 75.0% [95% CI: 64.9%-83.5%] and a specificity of 98.5% [95% CI: 94.6%-99.8%]. Furthermore, 8.7% reactivity in Asian parasite-infected individuals (8 out of 92) was observed. Besides this identification of a linear epitope marker, the information on the presence of linear epitopes in vaccine candidate proteins might be useful in the study of vaccines for river blindness.

Evaluation of an OV-16 IgG4 Enzyme-Linked Immunosorbent Assay in Humans and Its Application to Determine the Dynamics of Antibody Responses in a Non-Human Primate Model of Onchocerca volvulus Infection.

Onchocerciasis is a neglected parasitic disease targeted for elimination. Current World Health Organization guidelines for elimination include monitoring antibody responses to the recombinant Onchocerca volvulus antigen OV-16 in children to demonstrate the absence of transmission. We report the performance characteristics of a modified OV-16 enzyme-linked immunosorbent assay (ELISA) and describe anti-OV-16 responses in serum samples from laboratory-inoculated nonhuman primates (NHPs) in relation to microfilariae (mf) in skin snip biopsies. This OV-16 IgG4 ELISA had sensitivity and specificity of 88.2% and 99.7%, respectively, as determined by receiver operator characteristic analysis using a serum panel of 110 positive and 287 negative samples from people infected with other filariae or other parasitic infections. Anti-OV-16 responses in inoculated NHP (N = 9) were evaluated at quarterly intervals for IgM and the four IgG subclasses. Enzyme-linked immunosorbent assay results showed a well-defined IgG4 reactivity pattern and moderate IgG1 antibody responses. Meanwhile, the reactivity by IgG2, IgG3, or IgM did not show a clear pattern. Temporal evolution of IgG4 reactivity was evaluated through monthly testing, showing that NHPs developed anti-OV-16 IgG4 on average at 15 months postinoculation (range: 10-18 months). The average time to detectable mf was also 15 months (range: 11-25). The OV-16 ELISA used in this study was robust and allowed the detection of IgG4 responses, which were observed only among animals with detectable mf (N = 5), four of which showed declines in antibody responses once mf cleared. These findings also confirmed that the most informative antibody subclass responses to OV-16 are IgG4.

The parasite-derived rOv-ASP-1 is an effective antigen-sparing CD4+ T cell-dependent adjuvant for the trivalent inactivated influenza vaccine, and functions in the absence of MyD88 pathway.

Vaccination remains the most cost-effective biomedical approach for controlling influenza disease. In times of pandemics, however, these vaccines cannot be produced in sufficient quantities for worldwide use by the current manufacturing capacities and practices. What is needed is the development of adjuvanted vaccines capable of inducing an adequate or better immune response at a decreased antigen dose. Previously we showed that the protein adjuvant rOv-ASP-1 augments influenza-specific antibody titers and survival after virus challenge in both young adult and old-age mice when administered with the trivalent inactivated influenza vaccine (IIV3). In this study we show that a reduced amount of rOv-ASP-1, with 40-times less IIV3 can also induce protection. Apparently the potency of the rOv-ASP-1 adjuvanted IIV3 vaccine is independent of the IIV3-specific Th1/Th2 associated antibody responses, and independent of the presence of HAI antibodies. However, CD4+ T helper cells were indispensable for the protection. Further, rOv-ASP-1 with or without IIV3 elicited the increased level of various chemokines, which are known chemoattractant for immune cells, into the muscle 4 h after immunization, and significantly induced the recruitment of monocytes, macrophages and neutrophils into the muscles. The recruited monocytes had higher expression of the activation marker MHCII on their surface as well as CXCR3 and CCR2; receptors for IP-10 and MCP-1, respectively. These results show that the rOv-ASP-1 adjuvant allows substantial antigen sparing of IIV3 by stimulating at the site of injection the accumulation of chemokines and the recruitment of immune cells that can augment the activation of CD4+ T cell immune responses, essential for the production of antibody responses. Protection elicited by the rOv-ASP-1 adjuvanted IIV3 vaccine also appears to function in the absence of MyD88-signaling. Future studies will attempt to delineate the precise mechanisms by which the rOv-ASP-1 adjuvanted IIV3 vaccine works.

Sex and vaccination: Insights from female rats vaccinated with juvenile-specific proteases from Fasciola hepatica.

Most animal research is less evidence-based for females, with the majority of studies conducted on males. Since immune responses vary between males and females, sexual dimorphism in immunity contributes, among other things, to sex-based differences post-vaccination. However, the issue of sex effects in animal vaccine research is rarely considered in vaccine study design. Previously, we have evaluated the efficacy of cathepsin L3 (FhCL3-1 and FhCL3-2) and B3 proteases (FhCB3) from juvenile Fasciola hepatica as vaccines against fasciolosis in male rats. Their administration resulted in reductions in liver fluke recovery in the range of 47-63% when compared with an infection control group. Here, we investigated if the protective effect of vaccination with these proteins can also be observed for female rats. The data indicates females were not protected from F. hepatica infection when vaccinated with juvenile cathepsins. Only in the FhCL3-2 vaccinated group was a low, non-significant, reduction in worm burden observed (21%). Although liver fluke mean body lengths and wet weights were reduced in vaccinated animals when compared with the infection controls, these effects were adjuvant- not vaccine-induced, while for males changes in these parameters were related primarily to vaccination. Specific humoral responses throughout the study were evident; however, trends in antibody responses in females replicated trends observed previously for male humoral responses. Formerly, elevated levels of FhCL3-1 and FhCL3-2 specific IgG1 and IgG2a were suggested to be correlated with protection. Here, despite increased and clear responses of these antibodies, protection was not observed. Hence, in the present study the roles of IgG1 and IgG2 in liver fluke reduction are questionable. Results demonstrated in our study show that observations obtained in one sex are not always applicable to the other sex. Hopefully, the findings of the study will stimulate discussion of the issue of sex impacts on post-vaccination outcomes and will encourage researchers to consider sex in their future vaccine studies.

Molecular cloning of enolase from Trichinella spiralis and the protective immunity in mice.

Trichinella spiralis, the main pathogen of trichinosis, infects a wide range of mammalian hosts and is one of the most widespread parasites worldwide. For parasites, glycolysis is the most important way to generate energy. Previous studies showed that some enzymes involved in the glycolytic pathway play roles in regulation the host immunity. In this paper, enolase from T. spiralis was cloned and the protective potentials were studied. One hundred and sixty ICR mice were divided into four groups and vaccinated with recombinant enolase (pET-ENO), eukaryotic recombinant plasmid encoding enolase (pVAX1-ENO) and negative controls (pVAXl and PBS), respectively. Two weeks after the second immunization, each mouse was challenged orally with 200 muscle larvae (MLs) of T. spiralis. Results showed that mice vaccinated with pET-ENO and pVAX1-ENO induced specific antibodies of IgG, IgA, IgM, but no IgE. Subclasses of IgG antibodies showed that mice immunized with recombinant protein and recombinant plasmids induced a Th1/Th2 immune response. Concentrations of serum cytokines were detected and showed significant increase of IFN-γ, IL-4 and TGFß1, while IL-17 in each group was not significantly different. Flow cytometric analysis showed significant increase of CD4+ and CD8+ T lymphocytes in the groups immunized with recombinant protein and recombinant plasmids. Challenge infection demonstrated that immunized groups had a reduced number of worm burdens. The reductions of larvae per gram muscle (LPG) in pET-ENO and pVAX1-ENO group were 17.7% and 15.8% when compared with PBS control.

The use of gold nanorods as a new vaccine platform against schistosomiasis.

Schistosomiasis is an important parasitic disease affecting >207 million people in 76 countries around the world and causing approximately 250,000 deaths per year. At present, the main strategy adopted for the control of schistosomiasis is the use of safe chemotherapy, such as praziquantel. However, the high rates of reinfection after treatment restrict the use of this treatment approach and assume the need for other forms of control such as vaccination. Sm29 is a protein that is localized in the Schistosoma mansoni tegument of adult worms and schistosomula and is considered a powerful vaccine candidate. Because of the chemical, physical and immunological characteristics of nanoparticles, nanocarriers have received increasing attention. In the field of nanotechnology, gold nanorods are considered potential vaccine carriers. In this study, we bound S. mansoni rSm29 protein to gold nanorods either directly or by cysteamine functionalization. When the worm burden was evaluated, the AuNRs-NH2-rSm29 group of immunized mice showed the best protection level (34%). Following AuNRs-NH2-rSm29 immunization, we observed a Th1 immunological response in mice with higher production of IFN-γ, mainly by CD4+ and CD8+ T cells. Furthermore, AuNRs-NH2-rSm29 could activate dendritic cells in vitro, enhancing MHCII and MHCI expression and the production of IL-1ß in a NLRP3-, ASC- and Caspase-1-dependent manner. In summary, our findings support the use of nanorods as an immunization strategy in vaccine development against infectious diseases.

Vaccination against Fasciola hepatica using cathepsin L3 and B3 proteases delivered alone or in combination.

No licensed vaccine is currently available for prevention of Fasciola hepatica infections. However, considering the alarming increase in drug resistance, there is an urgent need for a safe and fully effective vaccine against fasciolosis. Here, we tested if cathepsins L (FhCL3-1, FhCL3-2) and B (FhCB3) secreted by juvenile liver flukes are viable vaccine targets when delivered alone or in combination in a rat model. Since control over the early immune response is crucial for parasite's establishment in its host, it was hypothesised that targeting fluke juvenile stages may prove beneficial. Moreover, it was assumed that selected antigens will act in a cumulative manner to interfere with liver fluke migration and thereby will reduce F. hepatica infection. Recombinant FhCL3-1 and FhCL3-2 delivered alone reduced liver fluke burdens by 47 % and 63 %, respectively. A trivalent vaccine containing rFhCL3-1/CL3-2/CB3 did not increase the protective vaccine efficacy compared to the rFhCL3-2 vaccinated group (53 %), although, reductions in liver fluke wet weight (statistically significant) and liver damage score were most pronounced. Further, the highest IgG1 and IgG2a levels were seen in rFhCL3-2 vaccinated rats, the group for which the highest reduction in worm burden was demonstrated. Moreover, IgG1 and IgG2a levels in vaccinated rats were significantly elevated compared to those reported for control groups up to 4 week post-infection. While the mechanism of protection remains unknown, it appears that it depends on vaccine-induced antibodies directed against cathepsins. The obtained results imply that F. hepatica juvenile-specific cathepsins are promising vaccine candidates that induce responses that successfully target early migratory liver fluke stages. Now, the challenge is to evaluate these juvenile-specific cathepsins for use in livestock.