Immune response at birth, long-term immune memory and 2 years follow-up after in-utero anti-HBV DNA immunization

Impact of lamivudine treatment in late pregnancy on the development of the foetal immune response to hepatitis B virus: a meta-analysis in R with the metafor package

BACKGROUND

Hepatitis B virus (HBV) infection is a worldwide public health burden, especially in Asia and Africa. Concerns were raised that foetal exposure to HBV and antiretroviral therapy (ART) might suppress the innate immune response and reduce the production of hepatitis B surface antibody (HBsAb) in foetuses and infants. We therefore conducted the current study to evaluate the impact of ART on the development of the immune response to HBV in foetuses and infants.

METHODS

We selected lamivudine instead of telbivudine or tenofovir as the intervention measurement because it was the oldest and most widely used ART during pregnancy and its safety data have been sufficiently documented. A comprehensive search was conducted in eight electronic databases, including four Chinese and four English databases. Studies that met the following eligibility criteria were included: human randomized controlled trials (RCTs); participants in the treatment group were exclusively exposed to lamivudine; participants in the control group were exposed to placebo, no treatment or hepatitis B immunoglobulin; all participants were HBV-positive pregnant women with a high viral load and the main outcome of interest was neonatal HBsAb seropositivity. Data were tabulated and analysed using R software.

RESULTS

Nine RCTs were included and analysed. Compared with controls, lamivudine significantly decreased HBsAb seronegativity in the newborn within 24 h after birth (indicating the foetal immune response to HBV). Similar results were noted in infants within 6-7 months after birth and infants within 12 months (indicating the neonatal immune response to HBV vaccine).

CONCLUSIONS

Lamivudine treatment in late pregnancy boosted the foetal immune response to HBV in utero and enhanced the neonatal immune response to hepatitis B vaccine after birth.

Hematogenous Routing of Exogenous mRNA Delivered Into the Amniotic Fluid

INTRODUCTION

Therapies based on exogenous messenger RNA (mRNA) administration have emerged as a powerful novel strategy for the actual or potential treatment of an assortment of diseases, including congenital surgical pathologies. We sought to determine whether the minimally invasive transamniotic route could be an alternative for prenatal mRNA delivery.

METHODS

Pregnant Sprague-Dawley dams underwent laparotomy followed by volume-matched intra-amniotic injections in all their fetuses (n = 120) of either a suspension of a custom firefly luciferase mRNA encapsulated by a lipid- and synthetic cationic polymer-based composite, or of a suspension of the same encapsulation components without mRNA, on gestational day 17 (E17; term = E21-22). On E18, E19, E20, and E21, samples from 14 fetal anatomical sites and maternal serum were procured for the screening of mRNA incorporation by host cells by measurement of luciferase activity via microplate luminometry. Statistical analysis was by Mann-Whitney U-test, including Bonferroni-adjustment.

RESULTS

Overall survival was 87.5% (105/120). Controlled by the encapsulating composite without mRNA, luciferase activity was detected in the animals that received encapsulated mRNA in the following fetal annexes: amniotic fluid, amnion, chorion, umbilical cord, and placenta (P = 0.033 to <0.001), as well as in the following fetal sites: liver, stomach, intestines, and lungs (P = 0.043-0.002).

CONCLUSIONS

Packaged exogenous mRNA can be incorporated by the fetus at least at select anatomical sites after simple intra-amniotic administration in a rodent model. The pattern and chronology of mRNA incorporation are compatible with transplacental hematogenous routing, as well as with fetal swallowing/aspiration. Further study of transamniotic mRNA administration is warranted.

Prospects and progress of DNA vaccines for treating hepatitis B

The hepatitis B virus (HBV) is a global cause of liver disease. The preventive HBV vaccine has effectively reduced the disease burden. However, an estimated 340 million chronic HBV cases are in need of treatment. Current standard therapy for chronic HBV blocks reverse transcription. As this therapy blocks viral maturation and not viral protein expression, any immune inhibition exerted by these proteins will remain throughout therapy. This may help to explain why these drugs rarely induce off-therapy responses. Albeit some restoration of immune function occurs during therapy, this is clearly insufficient to control replication. Central questions when considering therapeutic DNA vaccination as an addition to blocking virus production are as follows: what does one hope to achieve? What do we think is wrong and how can the vaccination correct this? We here discuss different scenarios with respect to the lack of success of tested DNA vaccines, and suggest strategies for improvement.

Enhancement of plasmid-mediated transgene expression

A large number of studies aimed at the treatment of cancer, autoimmune and metabolic diseases, neurodegenerative disorders, allergic diseases, as well as muscle disorders strengthen the fact that gene therapy could represent an alternative method to treat human diseases where conventional approaches are less effective. To improve transgene expression from plasmid vectors, DNA nuclear targeting sequences (DTSs) can be introduced in a vector backbone to increase in vivo expression up to 20-fold using electroporation (EP) delivery in muscle tissue. The purpose of this chapter is to represent a step-by-step strategy for the construction of a plasmid vector with enhanced efficiency of nuclear plasmid uptake and the methodic for the in vivo efficiency evaluation of the obtained expression vector.

DNA vaccines: developing new strategies against cancer

Due to their rapid and widespread development, DNA vaccines have entered into a variety of human clinical trials for vaccines against various diseases including cancer. Evidence that DNA vaccines are well tolerated and have an excellent safety profile proved to be of advantage as many clinical trials combines the first phase with the second, saving both time and money. It is clear from the results obtained in clinical trials that such DNA vaccines require much improvement in antigen expression and delivery methods to make them sufficiently effective in the clinic. Similarly, it is clear that additional strategies are required to activate effective immunity against poorly immunogenic tumor antigens. Engineering vaccine design for manipulating antigen presentation and processing pathways is one of the most important aspects that can be easily handled in the DNA vaccine technology. Several approaches have been investigated including DNA vaccine engineering, co-delivery of immunomodulatory molecules, safe routes of administration, prime-boost regimen and strategies to break the immunosuppressive networks mechanisms adopted by malignant cells to prevent immune cell function. Combined or single strategies to enhance the efficacy and immunogenicity of DNA vaccines are applied in completed and ongoing clinical trials, where the safety and tolerability of the DNA platform are substantiated. In this review on DNA vaccines, salient aspects on this topic going from basic research to the clinic are evaluated. Some representative DNA cancer vaccine studies are also discussed.

Strategies for Successful Vaccination against Hepatocellular Carcinoma

Current therapies against hepatocellular carcinoma (HCC) are not curative in the majority of patients. In the past, immunotherapy approaches aimed to non-specifically stimulate immune response were quite ineffective. New treatments based on stimulation of specific anti-tumor immune response are currently proposed and appear more promising. Tumor-specific antigens identified in HCC demonstrated immunogenicity both in preclinical and clinical trials. Effectiveness in animal studies raised interest in the clinical applicability of non-specific adoptive immunotherapy that prevented disease recurrence after tumor resection. Dendritic cell (DC)-based tumor vaccines achieved encouraging results, and cellular vaccines based on DCs have already entered clinical trials. Preventive and therapeutic DNA vaccination have been proposed, all based on tumor-associated antigens (TAAs), either modified or not, an example being alpha-fetoprotein (AFP). The concomitant expression of co-stimulatory molecules and cytokines was used to increase tumor immunogenicity. Syngeneic or nude mice models indicated that immunotherapy for HCC could stimulate an anti-tumor T-cell response leading to clinical benefit devoid of significant toxicity. The use of DNA-based vaccination raises exciting possibilities in preventing HCC in high-risk individuals such as those with cirrhosis. Novel immunotherapy strategies may contribute in the future to prevention and treatment of HCC.

ApoE gene delivery inhibits severe hypercholesterolemia in newborn ApoE-KO mice

Apolipoprotein E, a key regulator in cholesterol-rich lipoprotein metabolism, is considered a strong candidate for treating hypercholesterolemia and cardiovascular disease. Inherited deficiency of this protein results in type III hyperlipoproteinemia in humans. ApoE-knockout mice, which develop spontaneous hypercholesterolemia, are an excellent model of human atherosclerosis. Here we investigated the therapeutic effects of a plasmid vector encoding human APOE3 sequence intramuscularly injected in hypercholesterolemic newborn mice at the ages of 5 and 14 days. We further explored the possibility of inducing tolerance in newborns when injected early. Our data show that direct i.m. naked DNA injection reduces severe hypercholesterolemia in newborn mice. Moreover, when naked DNA is administrated early, no immune response is generated against the human APOE, allowing repeated administrations. Neonatal therapies are important for the treatment of many genetic childhood diseases where early administration is required to prevent developmental damage. We propose the use of direct i.m. naked gene transfer in newborns to prevent long-term damages arising from hypercholesterolemic conditions.

A single HBsAg DNA vaccination in combination with electroporation elicits long-term antibody responses in sheep

Vaccines continue to be the most cost effective method to reduce the burden of disease in both human and animal health. However, there is a need to improve the duration of immunity following vaccination, since maintenance of protective levels of antibody in serum or the ability to rapidly respond upon re-exposure (memory) is critical if vaccines are to provide long-term protective immunity. The purpose of this experiment was to test the duration of antibody responses and the ability to generate anamnestic responses following a single immunization with a DNA vaccine encoding hepatitis B surface antigen (HBsAg) delivered by a variety of routes. Sheep immunized with the conventional HBsAg subunit vaccine (Engerix-B) as well as sheep immunized with a HBsAg DNA vaccine, combined with electroporation, generated significant antibody responses that were sustained for 25 weeks after primary immunization. At 25 weeks, all experimental groups received a secondary immunization with the HBsAg subunit vaccine. Sheep that received a primary DNA immunization, in combination with electroporation, mounted an anamnestic response similar to the cohort immunized with the HBsAg subunit vaccine. In contrast, animals immunized with DNA vaccines administered without electroporation elicited no detectable memory response. The presence of immune memory was significantly correlated with the induction of a prolonged primary immune response. Thus, a single DNA vaccination, in combination with electroporation, approached the efficacy of the commercial subunit vaccine in the maintenance of long-term protective serum antibody titres and immune memory.

Feasibilty of in utero DNA vaccination following naked gene transfer into pig fetal muscle: Transgene expression, immunity and safety

The high toll of death among first-week infants is due to infections occurring at the end of pregnancy, during birth or by breastfeeding. This problem significantly concerns industrialized countries also. To prevent the typical "first-week infections", a vaccine would be protective as early as at the birth. In utero DNA immunization has demonstrated the effectiveness in inducing specific immunity in newborns. We have already published results of a 2-year follow-up showing long-term safety, protective antibody titers at birth and long-term immune memory, following intramuscular in utero anti-HBV DNA immunization in 90-days pig fetuses. We have now analyzed further parameters of short-term safety. Two different reporter genes were injected in the thigh muscles of 90-days fetuses. At 8 days following DNA injection, we found high-level of transgenes expression in all injected fetuses. A step gradient of expression from the area of injection was observed with both reporter genes. CMV promoter/enhancer produced higher levels of expression compared to SV40 promoter/enhancer. Moreover, no evidence of local or systemic flogistic alterations or fetal malformations, mortality or haemorrhage following intramuscular injection were observed. A single anti-HBV s-antigen DNA immunization in 90-days fetuses supported protective antibody levels in all immunized newborns, lasting at least up to 4 months after birth. Our report further sustains safety and efficacy of intramuscular in utero naked gene transfer and immunization. This approach may support therapeutic or prophylactic procedure in many early life-threatening pathologic conditions.