Regulatory aspects of quality and safety for live recombinant viral vaccines against infectious diseases in Japan.

Recombinant viral vaccines expressing antigens of pathogenic microbes (e.g., HIV, Ebola virus, and malaria) have been designed to overcome the insufficient immune responses induced by the conventional vaccines. Our knowledge of and clinical experience with the new recombinant viral vaccines are insufficient, and a clear regulatory pathway is needed for the further development and evaluation of recombinant viral vaccines. In 2018, the research group supported by the Ministry of Health, Labour and Welfare, Japan (MHLW) published a concept paper to address the development of recombinant viral vaccines against infectious diseases. Herein we summarize the concept paper-which explains the Japanese regulatory concerns about recombinant viral vaccines-and provide a focus of discussion about the development of recombinant viral vaccines.

GI-5005, a yeast vector vaccine expressing an NS3-core fusion protein for chronic HCV infection.

The HCV nonstructural protein 3 (NS3) and core protein are highly conserved among various HCV genotypes, and several B- and T-cell epitopes have been characterized with these antigens. The immunotherapeutic vaccine GI-5005, being developed by GlobeImmune Inc, is a Tarmogen (targeted molecular immunogen) consisting of recombinant Saccharomyces cerevisiae yeast expressing an HCV NS3-core fusion protein designed to elicit antigen-specific host CD4+ and CD8+ T-cell responses for the treatment of chronic HCV infection. GI-5005 has demonstrated robust immunogenicity in preclinical in vitro and in vivo models. In a phase Ib clinical trial, GI-5005 monotherapy was well tolerated and displayed efficacy in patients with chronic HCV infection. At the time of publication, interim data were available from a completed phase II trial that evaluated a triple therapy of GI-5005 in combination with the standard-of-care (SOC; PEGylated-IFNalpha and ribavirin) regimen, compared with the SOC regimen alone. Triple therapy resulted in improved early virological responses in all treatment-naïve patients. End-of-trial results, including data of sustained virological responses, are required to better evaluate the efficacy of GI-5005 for the improvement of viral clearance and to compare the efficacy of the agent with other approaches such as NS3 protease inhibitors.

Biodistribution and toxicological safety of adenovirus type 5 and type 35 vectored vaccines against human immunodeficiency virus-1 (HIV-1), Ebola, or Marburg are similar despite differing adenovirus serotype vector, manufacturer's construct, or gene inserts.

The Vaccine Research Center has developed vaccine candidates for different diseases/infectious agents (including HIV-1, Ebola, and Marburg viruses) built on an adenovirus vector platform, based on adenovirus type 5 or 35. To support clinical development of each vaccine candidate, pre-clinical studies were performed in rabbits to determine where in the body they biodistribute and how rapidly they clear, and to screen for potential toxicities (intrinsic and immunotoxicities). The vaccines biodistribute only to spleen, liver (Ad5 only), and/or iliac lymph node (Ad35 only) and otherwise remain in the site of injection muscle and overlying subcutis. Though approximately 10(11) viral particles were inoculated, already by Day 9, all but 10(3) to 10(5) genome copies per mu g of DNA had cleared from the injection site muscle. By three months, the adenovector was cleared with, at most, a few animals retaining a small number of copies in the injection site, spleen (Ad5), or iliac lymph node (Ad35). This pattern of limited biodistribution and extensive clearance is consistent regardless of differences in adenovector type (Ad5 or 35), manufacturer's construct and production methods, or gene-insert. Repeated dose toxicology studies identified treatment-related toxicities confined primarily to the sites of injection, in certain clinical pathology parameters, and in body temperatures (Ad5 vectors) and food consumption immediately post-inoculation. Systemic reactogenicity and reactogenicity at the sites of injection demonstrated reversibility. These data demonstrate the safety and suitability for investigational human use of Ad5 or Ad35 adenovector-based vaccine candidates at doses of up to 2 x 10(11) given intramuscularly to prevent various infectious diseases.

Liver-directed viral therapy for cancer p53-targeted adenoviruses and beyond.

Loss of p53 function is one of the most frequent genetic alterations in human cancers. Both replication-incompetent (rAd.p53, or SCH58500) and replication-selective (dl1520, or Onyx-015) adenoviruses are being developed for the treatment of p53-deficient cancers. Hepatic arterial infusion (HAI) has historically been used to selectively target colorectal tumors within the liver; consequently, regional therapy with adenovirus in this setting is an attractive approach. This article reviews Phase I and I/II HAI trial results with these adenovirus constructs.

Adsorption of colostral antibodies against classical swine fever, persistence of maternal antibodies, and effect on response to vaccination in baby pigs.

OBJECTIVE: To determine kinetics of antibody absorption, persistence of antibody concentrations, and influence of titers on vaccination of baby pigs with a vaccine against classical swine fever (CSF). ANIMALS: 15 sows and their litters. PROCEDURE: Farrowings were supervised. Initial time of suckling was recorded. In the first experiment, blood samples were collected at farrowing, 2 and 4 hours after suckling, and hourly until 10 hours after initial suckling. Samples were assayed for CSF antibodies, using a serum neutralizing (SN) test. A second experiment included 33 baby pigs vaccinated as follows: 10 prior to ingestion of colostrum, 18 between 1 and 4 hours after ingestion of colostrum, and 5 at 12 hours after ingestion of colostrum. Fourteen pigs were vaccinated when 7 weeks old, and 15 pigs were not vaccinated. At 10 weeks of age, pigs were challenge-exposed with virulent CSF virus. Blood samples were collected and assayed for CSF antibodies and p125 antigen and p125 antibodies. RESULTS: CSF antibodies were detected in pigs beginning 2 hours after suckling. Colostral antibodies persisted for > 7 weeks (half-life, 79 days). Vaccination of pigs before suckling provided effective protection from severe disease after challenge-exposure. However, vaccination of neonates with antibody titers was not effective, because 19 of 23 (82%) pigs succumbed after challenge-exposure. All pigs vaccinated when 7 weeks old resisted challenge-exposure, whereas all unvaccinated control pigs succumbed. CONCLUSIONS AND CLINICAL RELEVANCE: Vaccination before ingestion of colostrum conferred good protection against CSF in baby pigs. Vaccination of 7-week-old pigs that had decreasing concentrations of passively acquired antibodies was efficacious.

Transport of an influenza virus vaccine formulation (iscom) in Caco-2 cells.

The influenza virus envelope glycoproteins hemagglutinin and neuraminidase were administered to the apical or basolateral sides of Caco-2 monolayers either as native protein micelles (mic-ag) or after incorporation into the orally active adjuvant formulation, immune stimulating complexes (iscoms) (isc-ag). Biotin-conjugated isc-ag were localized in intracellular vesicles as early as 2 min after administration to the apical side at 37 degrees C. Ten minutes after administration, both intracellular vesicles and intercellular spaces were labeled, and extracellular labeling was observed on the basolateral side of the cells, indicating that isc-ag were transported across the epithelium within 10 min of exposure. Transport of 125I-labeled isc-ag and mic-ag in the apical-to-basolateral and basolateral-to-apical directions across Caco-2 monolayers was comparable at 37 degrees C. Gel chromatography analysis revealed that only 0.55-3.1% of transported isc-ag and mic-ag had a molecular weight of > 5,000, while 21.0-42.3% was eluted at a position corresponding to peptides of approximately 10 amino acids. Although isc-ag and mic-ag were transported and degraded by Caco-2 monolayers in comparable amounts, only transported isc-ag induced a dose-dependent proliferative response in vitro of T cells primed with influenza virus antigen. High-performance gel chromatography and reverse-phase high-performance liquid chromatography indicated that transported antigenic isc-ag consisted of hydrophobic peptides with a molecular weight of < or = 3,000. These results indicate that antigens incorporated into the orally active adjuvant formulation iscom are degraded to antigenic peptides during transport across the intestinal epithelium.