An antigen specific to the liver stage of rodent malaria recognized by a monoclonal antibody

Summary Vaccines currently being evaluated against malaria are based on proteins derived from the blood, sporozoite and sexual stages. Antigens from the liver stage, which is now recognized as the major target of protective sporozoite induced immunity, have received comparatively little attention. This paper describes the generation of a monoclonal antibody (MoAb), which recognizes an antigen specific to the liver stage of the rodent malaria Plasmodium berghei. The antigen is expressed throughout liver stage development and appears to be localized to the parasitophorous vacuole membrane. The MoAb did not affect the growth of liver stages cultured in vitro nor could protection be demonstrated in vivo following passive transfer of the antibody.     

A plant‐produced influenza subunit vaccine protects ferrets against virus challenge

Background Influenza A viruses are of major concern for public health, causing worldwide epidemics associated with high morbidity and mortality. Vaccines are critical for protection against influenza, but given the recent emergence of new strains with pandemic potential, and some limitations of the current production systems, there is a need for new approaches for vaccine development. Objective To demonstrate the immunogenicity and protective efficacy of plant‐produced influenza antigens. Method We engineered, using influenza A/Wyoming/3/03 (H3N2) as a model virus, the stem and globular domains of hemagglutinin (HA) produced in plants as fusions to a carrier protein and used purified antigens with and without adjuvant for ferret immunization. Results These plant‐produced antigens were highly immunogenic and conferred complete protection against infection in the ferret challenge model. The addition of plant‐produced neuraminidase was shown to enhance the immune response in ferrets. Conclusions Plants can be used as a production vehicle for vaccine development against influenza. Domains of HA can generate protective immune responses in ferrets.     

T‐helper 17 cell: A distinctive cell in liver diseases

T‐helper (Th)17 cells, a new population of effector CD4⁺ T cells, are characterized by the secretion of interleukin (IL)‐17. It has been demonstrated that Th17 cells are distinct from Th1 and Th2 cells; they play important roles in the pathogenesis of numerous inflammatory and autoimmune diseases; and are closely related to host defense, tumorigenesis and transplant rejection. Moreover, it has been found that these cells have a close and intricate connection with the regulatory T cells, which play an important role in maintaining self‐tolerance and down‐tuning immune responses. In the present review, we find that they are significantly elevated in various kinds of liver diseases including liver autoimmunity and inflammatory diseases, alcoholic liver disease and hepatocellular carcinoma.     

A recombinant chimeric protein composed of human and mice‐specific CD4+ and CD8+ T‐cell epitopes protects against visceral leishmaniasis

In this study, a recombinant chimeric protein (RCP), which was composed of specific CD4⁺ and CD8⁺ T‐cell epitopes to murine and human haplotypes, was evaluated as an immunogen against Leishmania infantum infection in a murine model. BALB/c mice received saline were immunized with saponin or with RCP with or without an adjuvant. The results showed that RCP/saponin‐vaccinated mice presented significantly higher levels of antileishmanial IFN‐γ, IL‐12 and GM‐CSF before and after challenge, which were associated with the reduction of IL‐4 and IL‐10 mediated responses. These animals showed significant reductions in the parasite burden in all evaluated organs, when both limiting dilution and quantitative real‐time PCR techniques were used. In addition, the protected animals presented higher levels of parasite‐specific nitrite, as well as the presence of anti‐Leishmania IgG2a isotype antibodies. In conclusion, the RCP/saponin vaccine could be considered as a prophylactic alternative to prevent against VL.     

Lactoferrin protects against concanavalin A‐induced liver injury in mice

Background: Liver diseases, caused by viral infection, autoimmune conditions, alcohol ingestion or the use of certain drugs, are a significant health issue, as many can develop into liver failure. Lactoferrin (Lac) is an iron‐binding glycoprotein that belongs to the transferrin family. Owing to its multiple biological functions, Lac has been evaluated in a number of clinical trials to treat infections, inflammation and cancer. Aim: The present study aims to reveal a profound hepatoprotective effect of Lac, using a mouse model of Concanavalin A (Con A)‐induced hepatitis, which mimics the pathophysiology of human viral and autoimmune hepatitis. Method: C57Bl/6J mice were injected with bovine Lac following Con A challenge. The effects of Lac on interferon (IFN)‐γ and interleukin (IL)‐4 expression were determined. The roles of Lac on T‐cell apoptosis and activation, and leukocytes infiltration were examined. Result: The data demonstrated that the protective effect of Lac was attributed to its ability to inhibit T‐cell activation and production of IFN‐γ, as well as to suppress IL‐4 production by hepatic natural killer T cells. Conclusion: These findings indicate a great therapeutic potential of Lac in treating in treating inflammatory hepatitis and possibly other inflammatory diseases.     

Hydrogen‐rich saline protects against liver injury in rats with obstructive jaundice

Background: Hydrogen selectively reduces levels of hydroxyl radicals and alleviates acute oxidative stress in many models. Hydrogen‐rich saline provides a high concentration of hydrogen that can be easily and safely applied. Aims: In this study, we investigated the effects of hydrogen‐rich saline on the prevention of liver injury induced by obstructive jaundice in rats. Methods: Male Sprague–Dawley rats (n=56) were divided randomly into four experimental groups: sham operated, bile duct ligation (BDL) plus saline treatment [5 ml/kg, intraperitoneal (i.p.)], BDL plus low‐dose hydrogen‐rich saline treatment (5 ml/kg, i.p.) and BDL plus high‐dose hydrogen‐rich saline treatment (10 ml/kg, i.p.). Results: The liver damage was evaluated microscopically 10 days after BDL. Serum alanine aminotransferase and aspartate aminotransferase levels, tissue malondialdehyde content, myeloperoxidase activity, tumour necrosis factor‐α, interleukin (IL)‐1β, IL‐6 and high‐mobility group box 1 levels were all increased significantly by BDL. Hydrogen‐rich saline reduced levels of these markers and relieved morphological liver injury. Additionally, hydrogen‐rich saline markedly increased the activities of anti‐oxidant enzymes superoxide dismutase and catalase and downregulated extracellular signal‐regulated protein kinase (ERK)1/2 activation. Conclusions: Hydrogen‐rich saline attenuates BDL‐induced liver damage, possibly by the reduction of inflammation and oxidative stress and the inhibition of the ERK1/2 pathway.     

Immune response to hepatitis B vaccine in patients with chronic hepatitis C infection: A systematic review and meta‐analysis

Hepatitis B virus and hepatitis C virus (HCV) co‐infection can add to the severity of hepatitis and the risks of liver cirrhosis and hepatocellular carcinoma. Whether chronic HCV infection decreases antibody response to hepatitis B vaccination is still controversial. We evaluate the influence of HCV infection on antibody response to hepatitis B vaccination by a systematic review of published works with a meta‐analysis of clinical trials. The random‐effects model of DerSimonian and Laird with heterogeneity and sensitivity analyses were used in this study. The end‐point of interest was the rate of patients showing seroconversion of antibody responses at completion of hepatitis B vaccination schedule among patients with chronic HCV infection versus healthy controls. We identified 11 studies involving 704 patients with HCV and 812 controls. Our results show a significant decrease in antibody seroconversion rates among patients with HCV versus healthy controls (pooled odds ratio = 0.17 [95% confidence interval, 0.11–0.28]). The P‐value was 0.21 for our test of study heterogeneity. Stratified analysis in subgroups of interest and sensitivity analysis did not meaningfully change our results. Our meta‐analysis showed patients with hepatitis C infection have a statistically significant lower rate of seroconversion in comparison to healthy controls, both in cirrhotic and non‐cirrhotic patients. Chronic HCV infection can decrease the immune response to a standard schedule of hepatitis B vaccination. Further studies are needed to investigate the optimum vaccination schedule for patients with chronic HCV infection.     

Sm‐p80‐based DNA vaccine made in a human use approved vector VR1020 protects against challenge infection with Schistosoma mansoni in mouse

Although there is an effective drug (praziquantel) available for the treatment of schistosomiasis, yet the disease is still spreading unabated and is rampant in 76 countries. Control via praziquantel treatment has so far been insufficient in reducing the disease transmission. Therefore, a vaccine in addition to other strategies, for example, improving sanitation and introduction of new drugs are essential to successfully control and eventually eradicate schistosomiasis. To this effect, we have targeted a functionally important antigen, Sm‐p80 as a vaccine candidate. In this study, full length cDNA of Sm‐p80 was cloned in VR1020, a FDA approved vector for human use. The protective efficacy of this vaccine formulation was tested in a murine model. Sm‐p80‐VR1020 vaccine formulation was able to induce 47% reduction in worm burden. Serology on samples obtained from vaccinated animals revealed a strong antibody response which included IgG and all of its subtypes, IgM and IgA. Proliferating splenocytes in response to recombinant Sm‐p80 produced a wide spectrum of cytokines representing Th1, Th2 and Th17 types, as ascertained via RT‐PCR analysis. These findings further strengthen the importance of Sm‐p80 molecule as a vaccine candidate for intestinal schistosomiasis.     

Next‐generation sequencing of the intrahepatic antibody repertoire delineates a unique B‐cell response in HBV‐associated acute liver failure

Hepatitis B virus (HBV) is a major cause of acute liver failure (ALF) worldwide. While liver damage in classic acute hepatitis B is believed to be T‐cell mediated, the pathogenesis of HBV‐associated ALF remains largely unknown. Access to liver specimens from well‐characterized patients with HBV‐associated ALF provided us with the opportunity to perform next‐generation sequencing (NGS) of the entire VH repertoires of IgM and IgG from the livers of four ALF patients, a control liver donor and a patient with chronic HBV infection. We found that ALF is not associated with expansion of specific B‐cell lineages. However, NGS showed that the intrahepatic VH repertoires from ALF patients were characterized by the abundant presence of antibodies in germline configuration in contrast to their marginal prevalence in controls. Moreover, NGS identified a large number of VH genes in germline configuration with identical VDJ sequences in the IgM and IgG repertoires in all four ALF patients, indicating that isotype switch from IgM to IgG had occurred without somatic hypermutation. The results of this study indicate that the presence of intrahepatic antibodies in unmutated germline configuration is a broad phenomenon in the global antibody repertoire generated from total RNA derived from whole‐liver tissue that is strongly associated with ALF, suggesting a major role of T cell–independent humoral immunity in the pathogenesis of ALF.     

Parasite load stemming from immunization route determines the duration of liver‐stage immunity

Immunization with radiation‐attenuated Plasmodium sporozoites (RAS) induces sterile and long‐lasting protective immunity. Although intravenous (IV) route of RAS immunization is reported to induce superior immunity compared to intradermal (ID) injection, its role in the maintenance of sterile immunity is yet to be understood. We investigated whether the route of homologous sporozoite challenge of Plasmodium berghei (Pb) RAS‐immunized mice would influence the longevity of protection. C57BL/6 mice immunized with Pb‐RAS by IV were 100% protected upon primary IV/ID sporozoite challenge. In contrast, ID immunization resulted in 80% protection, regardless of primary challenge route. Interestingly, the route of primary challenge was found to bring difference in the maintenance of sterile protection. While IV Pb RAS‐immunized mice remained protected at all challenges regardless of the route of primary challenge, ID Pb‐RAS‐immunized mice receiving ID primary challenge became parasitaemic upon secondary IV challenge. Significantly, primary IV challenge of Pb RAS ID‐immunized mice resulted in 80% and 50% survival at secondary and tertiary challenges, respectively. According to phenotypically diverse liver CD8⁺ T cells, the percentages and the numbers of both CD8⁺ T effector memory and resident memory cells were significantly higher in IV than in ID Pb RAS‐immunized mice. IFN‐γ‐producing CD8⁺ T cells specific to Pb TRAP₁₃₀ and MIP‐4‐Kb‐17 were also found significantly higher in IV mice than in ID mice. The enhanced T‐cell generation and the longevity of protection appear to be dependent on the parasite load during challenge when infection is tolerated under suboptimal CD8⁺ T‐cell response.     

Model for end‐stage liver disease,model for end‐stage liver disease‐sodium and Child–Turcotte–Pugh scores over time for the prediction of complications of liver cirrhosis

Background/Aims: There has been no report concerning the predictive capability of each scoring system in determining the development of complications of liver cirrhosis such as variceal bleeding and/or hepatic encephalopathy. Methods: We retrospectively studied 128 patients with liver cirrhosis [92 males; mean (standard deviation) 54.2 (11.2) years] admitted to our institution from March 2004 to April 2006. Seventy‐three patients (57.0%, group 1) were admitted because of complications of cirrhosis and 55 patients (43.0%, group 2) were admitted for causes unrelated to complications of cirrhosis. We calculated values for model for end‐stage liver disease (MELD), MELD‐sodium (MELD‐Na) and Child–Turcotte–Pugh (CTP) scores on admission and at 3 and 6 months before admission. Each delta score was defined as the difference in the scores of 3 and 6 months before admission. Results: The relative risk for complications in the patients with ΔMELD/3 months ≥1.35, ΔMELD‐Na/3 months ≥1.35 and ΔCTP/3 months ≥1 was 2.05 [95% confidence intervals (CI) 1.47–2.85, P<0.01], 2.04 (95% CI 1.45–2.88, P<0.01) and 1.98 (95% CI 1.39–2.81, P<0.01) respectively. The area under the receiver‐operating characteristic curves of ΔMELD/3 months, ΔMELD‐Na/3 months and ΔCTP/3 months for the occurrence of cirrhotic complications were 0.691, 0.694 and 0.722 respectively. A higher ΔMELD/3 months (≥1.35), ΔMELD‐Na/3 months (≥1.35) and ΔCTP/3 months (≥1) was associated with decreased survival. Conclusions: Delta model for end‐stage liver disease/3 months, ΔMELD‐Na/3 months and ΔCTP/3 months were clinically useful parameters for predicting the occurrence of cirrhotic complications.     

Evidence of cross‐stage CD8+ T cell epitopes in malaria pre‐erythrocytic and blood stage infections

Malaria parasites have a complex, multistage life cycle and there is a widely held view that each stage displays a distinct set of antigens presented to the immune system. Yet, molecular analysis of malaria parasites suggests that many putative antigenic targets are shared amongst the different stages. The specificities of these cross‐stage antigens and the functions of the immune responses they elicit are poorly characterized. It is well‐known that CD8+ T cells play opposing immune functions following Plasmodium berghei (Pb) infection of C57BL/6 mice. Whilst these cells play a crucial role in protective immunity against pre‐erythrocytic stages, they are implicated in the development of severe disease during blood stages. Recently, CD8+ T cell epitopes derived from proteins supposedly specific for either pre‐erythrocytic or blood stages have been described. In this brief report, we have compiled and confirmed data that the majority of the mRNAs and/or proteins from which these epitopes are derived display expression across pre‐erythrocytic and blood stages. Importantly, we provide evidence of cross‐stage immune recognition of the majority of these CD8+ T cell epitopes. Hence, our findings provide a resource to further examine the relevance of antigen‐specific cross‐stage responses during malaria infections.