Stephen Coates

Safety and Immunogenicity of HCV E1E2 Vaccine Adjuvanted with MF59 Administered to Healthy Adults

BACKGROUND Hepatitis C virus (HCV) causes chronic liver disease that often leads to cirrhosis and hepatocellular carcinoma. In animal studies, chimpanzees were protected against chronic infection following experimental challenge with either homologous or heterologous HCV genotype 1a strains which predominate in the USA and Canada. We describe the first in humans clinical trial of this prophylactic HCV vaccine. METHODS HCV E1E2 adjuvanted with MF59C.1 (an oil-in-water emulsion) was given at 3 different dosages on day 0 and weeks 4, 24 and 48 in a phase 1, placebo-controlled, dose escalation trial to healthy HCV-negative adults. RESULTS There was no significant difference in the proportion of subjects reporting adverse events across the groups. Following vaccination subjects developed antibodies detectable by ELISA, CD81 neutralization and VSV/HCV pseudotype neutralization. There were no significant differences between vaccine groups in the number of responders and geometric mean titers for each of the three assays. All subjects developed lymphocyte proliferation responses to E1E2 and an inverse response to increasing amounts of antigen was noted. CONCLUSIONS The vaccine was safe and generally well-tolerated at each of the 3 dosage levels and induced antibody and lymphoproliferative responses. A larger study to further evaluate safety and immunogenicity is warranted.

Purification and Characterization of Oligomeric Envelope Glycoprotein from a Primary R5 Subtype B Human Immunodeficiency Virus

ABSTRACT Human immunodeficiency virus (HIV) continues to be a major public health problem throughout the world, with high levels of mortality and morbidity associated with AIDS. Considerable efforts to develop an effective vaccine for HIV have been directed towards the generation of cellular, humoral, and mucosal immune responses. A major emphasis of our work has been toward the evaluation of oligomeric (o-gp140) forms of the HIV type 1 (HIV-1) envelope protein for their ability to induce neutralizing antibody responses. We have derived stable CHO cell lines expressing o-gp140 envelope protein from the primary non-syncytium-inducing (R5) subtype B strain HIV-1US4. We have developed an efficient purification strategy to purify oligomers to near homogeneity. Using a combination of three detectors measuring intrinsic viscosity, light scattering, and refractive index, we calculated the molecular mass of the oligomer to be 474 kDa, consistent with either a trimer or a tetramer. The hydrodynamic radius (Rh ) of o-gp140 was determined to be 8.40 nm, compared with 5.07 nm for the monomer. The relatively smaller Rh of the oligomer suggests that there are indeed differences between the foldings of o-gp140 and gp120. To assess the structural integrity of the purified trimers, we performed a detailed characterization of the glycosylation profile of o-gp140, its ability to bind soluble CD4, and also its ability to bind to a panel of monoclonal antibodies with known epitope specificities for the CD4 binding site, the CD4 inducible site, the V3 loop, and gp41. Immunogenicity studies with rabbits indicated that the purified o-gp140 protein was highly immunogenic and induced high-titer, high-avidity antibodies directed predominantly against conformational epitopes. These observations confirm the structural integrity of purified o-gp140 and its potential as a vaccine antigen.

Priming of CD4+ and CD8+ T cell responses using a HCV core ISCOMATRIX vaccine: a phase I study in healthy volunteers.

The disease burden and public health impact of chronic HCV infection continues to be a major problem globally. Current treatment for chronic HCV infection is not effective in all patients and is frequently associated with unacceptable side effects. Clearly a need exists for improved treatments and one such strategy is the use of therapeutic vaccines. Although still not completely understood, emerging data indicate that the generation of CD4+ and CD8+ T cells are important for the clearance of HCV. We have developed a prototype vaccine with the HCV Core protein and ISCOMATRIX™ adjuvant (HCV Core ISCOMATRIX™ vaccine). ISCOMATRIX™ vaccines have been shown to induce CD4+ and CD8+ T cell responses to a range of antigens in both animal models and in human studies. Additionally, ISCOMATRIX™ vaccines have been shown to be safe and generally well tolerated in several clinical trials. Preliminary studies demonstrated that the prototype HCV Core ISCOMATRIX™ vaccine induced strong CD4+ and CD8+ T cell responses in monkeys following immunisation. Here we show the results of a Phase I placebo controlled, dose escalation clinical study designed to evaluate the safety, tolerability and immunogenicity of the HCV Core ISCOMATRIX™ vaccine in healthy individuals. The 30 subjects received 3 immunisations of HCV Core ISCOMATRIX™ vaccines or placebo vaccine on days 0, 28 and 56. The HCV Core ISCOMATRIX™ vaccines contained 5, 20 or 50 μg HCV Core protein with 120 μg ISCOMATRIX™ adjuvant. The adverse events reported were generally mild to moderate in severity, of short duration and self-limiting. The most common adverse events were injection site reactions such as pain and redness as well as myalgia. Antibody responses were detected in all but one of the participants receiving the HCV Core ISCOMATRIX™ vaccine and there was no indication of a dose response. CD8+ T cell responses were only detected in 2 of the 8 participants receiving the highest dose. T cell cytokines were detected in 7 of the 8 participants in the highest dose group. The results of this study support the further evaluation of this prototype HCV Core ISCOMATRIX™ vaccine in HCV infected subjects.

Characterization of antibodies induced by vaccination with Hepatitis C virus envelope glycoproteins

Abstract Hepatitis C virus (HCV) envelope glycoproteins E1 and E2 were used with MF59 adjuvant as a candidate vaccine for a phase 1 safety and immunogenicity trial. Ten of 41 vaccinee serum samples displayed a neutralization titer of ⩾1:20 against vesicular stomatitis virus (VSV)-HCV pseudotype, 15 of 36 serum samples tested had a neutralization titer of ⩾1:400 against human immunodeficiency virus (HIV)-HCV pseudotype, and 10 of 36 serum samples tested had a neutralization titer of ⩾1:20 against cell culture-grown HCV genotype 1a. Neutralizing serum samples had increased affinity levels and displayed >2-fold higher specific activity levels to well-characterized epitopes on E1/E2, especially to the hypervariable region 1 of E2.

Synthesis and Characterization of a Native, Oligomeric Form of Recombinant Severe Acute Respiratory Syndrome Coronavirus Spike Glycoprotein

ABSTRACT We have expressed and characterized the severe acute respiratory syndrome coronavirus (SARS-CoV) spike protein in cDNA-transfected mammalian cells. The full-length spike protein (S) was newly synthesized as an endoglycosidase H (endo H)-sensitive glycoprotein (gp170) that is further modified into an endo H-resistant glycoprotein (gp180) in the Golgi apparatus. No substantial proteolytic cleavage of S was observed, suggesting that S is not processed into head (S1) and stalk (S2) domains as observed for certain other coronaviruses. While the expressed full-length S glycoprotein was exclusively cell associated, a truncation of S by excluding the C-terminal transmembrane and cytoplasmic tail domains resulted in the expression of an endoplasmic reticulum-localized glycoprotein (gp160) as well as a Golgi-specific form (gp170) which was ultimately secreted into the cell culture medium. Chemical cross-linking, thermal denaturation, and size fractionation analyses suggested that the full-length S glycoprotein of SARS-CoV forms a higher order structure of ∼500 kDa, which is consistent with it being an S homotrimer. The latter was also observed in purified virions. The intracellular form of the C-terminally truncated S protein (but not the secreted form) also forms trimers, but with much less efficiency than full-length S. Deglycosylation of the full-length homotrimer with peptide N-glycosidase-F under native conditions abolished recognition of the protein by virus-neutralizing antisera raised against purified virions, suggesting the importance of the carbohydrate in the correct folding of the S protein. These data should aid in the design of recombinant vaccine antigens to prevent the spread of this emerging pathogen.

Induction of Broad CD4+ and CD8+ T-Cell Responses and Cross- Neutralizing Antibodies against Hepatitis C Virus by Vaccination with Th1-Adjuvanted Polypeptides Followed by Defective Alphaviral Particles Expressing Envelope Glycoproteins gpE1 and gpE2 and Nonstructural Proteins 3, 4, and 5

ABSTRACT Broad, multispecific CD4+ and CD8+ T-cell responses to the hepatitis C virus (HCV), as well as virus-cross-neutralizing antibodies, are associated with recovery from acute infection and may also be associated in chronic HCV patients with a favorable response to antiviral treatment. In order to recapitulate all of these responses in an ideal vaccine regimen, we have explored the use of recombinant HCV polypeptides combined with various Th1-type adjuvants and replication-defective alphaviral particles encoding HCV proteins in various prime/boost modalities in BALB/c mice. Defective chimeric alphaviral particles derived from the Sindbis and Venezuelan equine encephalitis viruses encoding either the HCV envelope glycoprotein gpE1/gpE2 heterodimer (E1E2) or nonstructural proteins 3, 4, and 5 (NS345) elicited strong CD8+ T-cell responses but low CD4+ T helper responses to these HCV gene products. In contrast, recombinant E1E2 glycoproteins adjuvanted with MF59 containing a CpG oligonucleotide elicited strong CD4+ T helper responses but no CD8+ T-cell responses. A recombinant NS345 polyprotein also stimulated strong CD4+ T helper responses but no CD8+ T-cell responses when adjuvanted with Iscomatrix containing CpG. Optimal elicitation of broad CD4+ and CD8+ T-cell responses to E1E2 and NS345 was obtained by first priming with Th1-adjuvanted proteins and then boosting with chimeric, defective alphaviruses expressing these HCV genes. In addition, this prime/boost regimen resulted in the induction of anti-E1E2 antibodies capable of cross-neutralizing heterologous HCV isolates in vitro. This vaccine formulation and regimen may therefore be optimal in humans for protection against this highly heterogeneous global pathogen.

Immunization of Human Volunteers With Hepatitis C Virus Envelope Glycoproteins Elicits Antibodies That Cross-Neutralize Heterologous Virus Strains

TO THE EDITOR—Ray and colleagues recently demonstrated hepatitis C virus (HCV) glycoprotein-specific neutralizing responses against homologous HCV-1 and the closely related genotype 1a HCV strain H77 [1]. Using well-characterized pseudoparticle (HCVpp) and cell culture replicating virus systems (HCVcc) [2], we set out to further investigate the breadth of the neutralizing responses elicited by vaccination. We tested serum samples from 8 of the volunteers reported in the study by Ray et al [1], selecting representative samples that had low, intermediate, and high anti-E1E2 antibody titers as measured by enzyme immunoassay (Novartis Vaccines and Diagnostics, Emeryville, CA). Generation of cross-reactive neutralizing antibodies (nAb) in response to vaccination has been a major hurdle for RNA viruses such as human immunodeficiency virus (reviewed in [3]). We reported that immunizing rodents with HCV E1E2 heterodimer or truncated soluble E2 derived from the genotype 1a HCV-1 strain elicited high titer cross-reactive nAb [2]. Here we report that immunization of healthy human volunteers with the same recombinant HCV-1 E1E2 glycoproteins can induce a cross-reactive neutralizing antibody response. Serum samples from 8 healthy immunized volunteers were assessed for their ability to neutralize a panel of HCVpp strains. Briefly, pre- and postimmune serum samples at a final dilution of 1/100 were preincubated with HCVpp encoding a luciferase reporter for 1 hour at 37°C prior to infecting Huh-7.5 cells for 6 hours at 37°C. Infection was quantified after 72 hours by monitoring luciferase activity (Figure 1). All immune serum samples neutralized HCVpp expressing the closely related genotype 1a H77 glycoproteins, the heterologous genotype 1b glycoproteins CON1 and OH8, and the more distantly related genotype 2a strain J6, albeit with reduced efficiency. Preimmune and postimmune serum samples had no effect on murine leukemia virus pseudoparticle infection (Figure 1). Figure 1. Recombinant hepatitis C virus type 1 (HCV-1) genotype 1a E1E2 glycoproteins elicit cross-neutralizing activity in vaccinated humans. Eight healthy adult volunteers were immunized with 4–100 μg of E1E2 with adjuvant MF59 at 0, 1, and 6 ... To ascertain the ability of immune serum samples to neutralize HCVcc, we tested the sensitivity of chimeric JFH-1 viruses expressing H77 and J6 structural proteins to inhibition by immune serum samples. All serum samples were clearly capable of neutralizing both heterologous HCVcc viruses, although less efficiently in the case of the 2a virus (Figure 1). Our experiments demonstrate that immunization of human volunteers with recombinant E1E2 glycoproteins derived from the genotype 1a strain elicits antibodies that can cross-neutralize the in vitro infectivity of heterologous strains derived from genotypes 1a, 1b, and 2a. Despite indications that HCV can transmit in vitro in the presence of antibodies targeting the viral encoded glycoproteins via direct transfer between adjacent contacting cells [4], recent studies with chimeric SCID-uPA mice have yielded encouraging results for a protective role of nAb to prevent or ameliorate virus infection in vivo [5, 6]. Our studies using HCVpp and matching HCVcc strains expand upon the work of Ray et al [1] and demonstrate that vaccination of human volunteers elicits antibody responses with significant cross-neutralizing activity against heterologous 1a, 1b, and 2a HCV genotypes, warranting the continued clinical development of recombinant glycoprotein vaccine preparations.