Aspectos moleculares de la respuesta antiviral contra el virus de la hepatitis C importantes para el desarrollo de vacunas / Molecular aspects of the antiviral response against hepatitis C virus implicated in vaccines development

La hepatitis C es una enfermedad viral hepática causada por un hepacivirus de la familia Flaviviridae, el cual posee un genoma de molécula única de ARN altamente variable. Codifica 10 proteínas necesarias para infectar las células y multiplicarse dentro de ellas. Su replicación se da únicamente en los hepatocitos. Debido a su gran variabilidad genómica y a la ausencia de síntomas de la enfermedad, se dificulta realizar un tratamiento temprano y acertado. En este trabajo se analiza el mecanismo molecular mediante el cual el virus infecta los hepatocitos y desarrolla la enfermedad. Particularmente, analizamos las alternativas terapéuticas, discutiendo la posibilidad de mejorar el tratamiento con el uso de nuevas vacunas específicas. Destacamos el uso de nuevas terapias basadas en ácidos nucleicos, principalmente vectores de ADN. Durante los próximos años, una vez que este tipo de tratamiento sea evaluado adecuadamente en ensayos clínicos y se equilibren los costos, constituirá una alternativa a los métodos convencionales muy beneficiosa

Hepatitis C is a contagious liver disease caused by hepacivirus of the Flaviviridae family. It has a RNA genome, a unique highly variable molecule. It encodes ten proteins which are necessary to infect cells and multiply. Replication occurs only in hepatocytes. Because of its wide genomic variability and the absence of symptoms, it is difficult to make an early diagnosis and successful treatment. In this review we analyze the molecular mechanism by which the virus infects the hepatocytes and causes the disease. We focused the analysis on different therapies, with the possibility of improving treatment with the use of new specific vaccines. We highlight the use of new therapies based on nucleic acids, mainly DNA vectors. In the near future, once this treatment is adequately evaluated in clinical trials, and the costs are calculated, it could be a very beneficial alternative to conventional methods

Toxicology and biodistribution study of CIGB-230, a DNA vaccine against hepatitis C virus.

CIGB-230, a mixture of a DNA plasmid expressing hepatitis C virus (HCV) structural antigens and a HCV recombinant capsid protein, has demonstrated to elicit strong immune responses in animals. The present study evaluated the plasmid biodistribution after the administration of CIGB-230 in mice, as well as toxicity of this vaccine candidate in rats. In the biodistribution study, mice received single or repeated intramuscular injections of CIGB-230, 50 microg of plasmid DNA mixed with 5 microg of Co.120 protein. Plasmid presence was assessed in ovaries, kidney, liver, pancreas, mesenteric ganglion, blood, and muscle of the injection site by a qualitative polymerase chain reaction. The toxicology evaluation included treatment groups receiving doses 5, 15, or 50 times higher, according to the body weight, than the expected therapeutic clinical dose. During the first hour after repeated inoculation, a promiscuous distribution was observed. However, 3 months later, plasmid could not be detected in any tissue. There was an absence of detectable adverse effects on key toxicology parameters and no damage evidenced in inspected organs and tissues. These results indicate that CIGB-230 is nontoxic at local and systemic levels and no concerns about persistence are observed, which support clinical testing of this vaccine candidate against HCV.

Safety and immunogenicity of subcutaneous hepatitis A vaccine in children with haemophilia.

Individuals with Haemophilia are at risk from hepatitis A virus (HAV) infection through exposure to blood products. Havrix(R), an intramuscular hepatitis A vaccine, is currently recommended for the prevention of disease caused by hepatitis A virus. Because bleeding may complicate intramuscular injections in those with bleeding disorders, we conducted a randomized, Phase IV clinical trial to compare the safety and immunogenicity of Havrix(R) given by the subcutaneous (s.c) vs. intramuscular (i.m.) route. A total of 45 children with Haemophilia were vaccinated subcutaneously, while their 41 nonhaemophlic siblings were vaccinated intramuscularly, at a dose of 720 Elisa units (EL.U.) at time 0 and 6 months. All children were anti-HAV and anti-HIV negative at baseline, and the haemophilic group did not differ from their siblings in alanine aminotransferase (ALT; 25 IU L-1 vs. 22 IU L-1), or in age; 8.5 years vs. 8.7 years. The vaccine was well tolerated, with minor adverse events being similar between groups; 21 (47%) vs. 24 (58%), P > 0.05. Local symptoms included soreness in 39 (45%), erythema in 25 (29%), swelling in 21 (24%), and bruising in six (7%), with no differences between groups. The proportion seroconverting to anti-HAV IgG positive did not differ between groups; 98% vs. 97% at month 1; 82% vs. 93% at month 6; and 100% vs. 100% at month 8, respectively. The HAV geometric mean titre was lower in those with Haemophilia, 185 vs. 233 mIU mL-1 at month 1; 68 vs. 94 mIU mL-1 at month 6; and 584 vs. 1082 mIU mL-1 at month 8, respectively. We conclude that Havrix(R) is safe and immunogenic when administered s. c. in children with Haemophilia.

IRIV-adjuvanted hepatitis A vaccine: in vivo absorption and biophysical characterization.

Immunopotentiating reconstituted influenza virosomes (IRIV) are 150-nm proteoliposomes composed of influenza surface glycoproteins and a mixture of natural and synthetic phospholipids. Due to size, structure and composition of the IRIVs, they serve as an antigen carrier system for efficacious vaccination, as was demonstrated for hepatitis A and influenza. This paper reviews the unique properties of IRIVs and describes the in vivo biodistribution of model antigens using 14C-labeled IRIVs and 125I-labeled streptavidin. IRIV formulated streptavidin induced a strong depot effect after intra muscular (i.m.) vaccination of mice, whereas soluble streptavidin was soon eliminated via the kidney of the animals. A mixture of antigen and IRIVs yielded higher antibody titers after i.m. inoculation than streptavidin alone. The highest immunostimulation was achieved by the binding of the antigen to the investigated adjuvant. The potential penetration of inactivated hepatitis A virions into lipid membranes was assessed by measuring the area increase of a lipid monolayer kept at a constant surface pressure corresponding to that of lipid bilayer vesicles. The monolayers were composed of phosphatidylcholine (POPC) and phosphatidylethanolamine (POPE) (75/25 mol/mol), thus resembling the lipid composition of the IRIV. The results suggested that the hepatitis A antigen may spontaneously bind to the reconstituted IRIV membranes.

Consideraciones sobre la vacunación contra la hepatitis A / Considerations about hepatitis A vaccination

Hepatitis A is endemic in Chile with rates of 100 cases per 100.000 inhabitants/years, figure that triplicates in school age children. Its social impact justifies educational and other public work measures to control it. Vaccines are an effective but expensive control resourse. The vaccine elaborated with the inactive HM 175 strain, recently licensed in Chile, is immunogenic, effective and well tolerated in adults and children over 3 years old. Its main indication is for voyagers to endemic areas and patients with chronic liver diseases. In Chile, its individual prescription requires the assessment of patient's individual risk and basal immunological status. Its massive application requires a better knowledge of hepatitis A geographical distribution, age of infection and cost benefit ratios

Safety, immunogenicity, and kinetics of the immune response to a single dose of virosome-formulated hepatitis A vaccine in Thais.

The safety and immunogenicity of a single dose of virosome-formulated hepatitis A vaccine was evaluated in healthy seronegative Thai volunteers. Immunization elicited primarily mild transient reactions which did not interfere with normal activities. All subjects possessed > 20 mIU of anti-hepatitis A virus antibody per ml of serum one month after immunization. Such a prolonged rise in antibody titre is characteristic of virosome-formulated vaccines. Protective titres (> 20 mIU ml-1) were maintained by all subjects over the one-year observation period.

Engerix-B hepatitis B vaccine (recombinant)/Smith, Kline & French.

Engerix-B [Hepatitis B Vaccine (Recombinant)], a product by SmithKline Biologicals, is a noninfectious recombinant DNA hepatitis B vaccine for immunization against infection caused by all known subtypes of hepatitis B virus. It provides a safe and well-tolerated vaccination regimen shown to confer immunity on the basis of anti-HBs antibody responses comparable with those of plasma-derived vaccines.