Development of adjuvanted recombinant zoster vaccine and its implications for shingles prevention

INTRODUCTION

GSK has developed a two-dose adjuvanted recombinant zoster vaccine (Shingrix, RZV) to protect people aged ≥50 years (50+) against herpes zoster (HZ) and its complications. RZV showed >90% efficacy against HZ, sustained over 4 years of follow-up, in all studied age groups.

AREAS COVERED

This article reviews the scientific rationale underlying the design of RZV; the clinical evidence demonstrating immunogenicity, safety, and efficacy in persons 50+; and the public health implications and cost-effectiveness.

EXPERT COMMENTARY

A decline in varicella zoster virus (VZV) immunity is associated with increased risk of HZ in adults 50+ and immunocompromised individuals. RZV was designed to restore levels of anti-VZV cellular and humoral immunity to prevent VZV reactivation. RZV includes the recombinant gE glycoprotein antigen, and Adjuvant System AS01_B which promotes cellular and antibody responses. In two Phase III studies in subjects aged 50+ and 70+ years, RZV efficacy against HZ compared to placebo was >90% and ≥89% against post-herpetic neuralgia (PHN). RZV is expected to dramatically impact HZ morbidity including its complications, and associated health-care costs. In the US population aged 50+ years, vaccination with RZV can be cost-effective compared to no vaccination and cost-saving compared to the currently available live-attenuated HZ vaccine (Zostavax, Merck).

A randomized, controlled dose-finding Phase II study of the M72/AS01 candidate tuberculosis vaccine in healthy PPD-positive adults

Purpose

In this dose-finding Phase II study (NCT00621322), we evaluated the safety and immunogenicity of different formulations of the candidate tuberculosis vaccine containing the M72 antigen (10/20/40 μg doses) and the liposome-based AS01 Adjuvant System. We aimed to select the lowest-dose combination of M72 and AS01 that was clinically well tolerated with immunogenicity comparable to that of the previously tested M72/AS01_B (40 μg) candidate vaccine.

Methods

Healthy PPD-positive (induration 3–10 mm) adults (18–45 years) in The Philippines were randomized (4:4:4:4:1:1) to receive 2 injections, 1 month apart, of M72/AS01_B (40 μg), M72/AS01_E (10 μg), M72/AS01_E (20 μg), M72/AS02_D (10 μg), M72/Saline (40 μg) or AS01_B alone, and were followed up for 6 months. AS01_E and AS02_D contain half the quantities of the immunostimulants present in AS01_B. AS02_D is an oil-in-water emulsion. Vaccine selection was based on the CD4⁺ T-cell responses at 1 month post vaccination.

Results

All formulations had a clinically acceptable safety profile with no vaccine-related serious adverse events reported. Two vaccinations of each adjuvanted M72 vaccine induced M72-specific CD4⁺ T-cell and humoral responses persisting at 6 months post vaccination. No responses were observed with AS01_B alone. One month post second vaccination, CD4⁺ T-cell responses induced by each of the three M72/AS01 vaccine formulations were of comparable magnitudes, and all were significantly higher than those induced by M72/AS02_D (10 μg) and M72/Saline.

Conclusions

The formulation with the lowest antigen and adjuvant dose, M72/AS01_E (10 μg), fulfilled our pre-defined selection criteria and has been selected for further clinical development.

The human rotavirus vaccine Rotarix™ in infants: an integrated analysis of safety and reactogenicity

An integrated analysis of safety and reactogenicity data was undertaken for 28 randomized, placebo-controlled, double-blind Phase II and III trials (DBRCTs) of the oral live-attenuated human rotavirus vaccine, Rotarix™ (GlaxoSmithKline Vaccines). Healthy infants aged 6-20 wk received 2 or 3 doses of vaccine (n=56562) or placebo (n=45512) at 4- to 8-wk intervals. Solicited adverse events (AEs) were recorded for 8 d after each dose of vaccine or placebo. Unsolicited AEs, serious AEs (SAEs), and deaths were evaluated over 31-d post-vaccination follow-up periods. 95% confidence intervals (CIs) for the relative risk (RR) across studies excluding "1.0" signified potential imbalances between the 2 groups. The incidence of each solicited AE of any or Grade 3 severity was similar between groups. The incidence of all unsolicited AEs of any (RR=0.99 [95% CI: 0.94-1.04]; P=0.72) or Grade 3 severity (RR=0.91 [95% CI: 0.77-1.08]; P=0.31) was similar between groups. A significantly higher proportion of SAEs were reported in the placebo group compared with the vaccine group (RR=0.9 [95% CI: 0.82-0.98]; P=0.01). The incidence of death was low and similar between the 2 groups (0.13% in the vaccine group and 0.11% in the placebo group; RR=1.14 [95% CI: 0.78-1.68]; P=0.54). Very few cases of intussusception were reported (11 and 7 in the vaccine and placebo groups, respectively; RR=1.39 [95% CI: 0.49-4.27]; P=0.66). In conclusion, results of this analysis of DBRCTs show that the human rotavirus vaccine Rotarix™ has a reactogenicity and safety profile similar to placebo.

Using in silico transcriptomics to search for tumor-associated antigens for immunotherapy

Immunotherapy approaches to fight cancer are based on the principle of mounting an immune response against a self-antigen expressed by the tumor cells. In order to reduce potential autoimmunity side-effects, the antigens used should be as tumor-specific as possible. A complementary approach to experimental tumor antigen discovery is to screen the human genome in silico, particularly the databases of "Expressed Sequence Tags" (ESTs), in search of tumor-specific and tumor-associated antigens. The public databases currently provide a massive amount of ESTs from several hundreds of cDNA tissue libraries, including tumoral tissues from various types. We describe a novel method of EST database screening that allows new potential tumor-associated genes to be efficiently selected. The resulting list of candidates is enriched in known genes, described as being expressed in tumor cells.

Applied genome research in the field of human vaccines

Prophylactic vaccination has made an essential contribution to the improvement of human health over the 20th century. However, we still lack efficient vaccines against major human diseases such as malaria or tuberculosis. Today, the design of therapeutic vaccines referred to as 'pharmaccines' is actively investigated in order to treat diseases such as cancer. In that context, novel ways to rationalize and accelerate vaccine discovery are needed. A series of advances in the fields of molecular biology and computer science, have greatly accelerated the rate at which candidate vaccine antigens can be discovered. In this review, we will present and discuss how applied genome research may facilitate antigen discovery and the design of new prophylactic and therapeutic vaccines.

Topology prediction of Brucella abortus Omp2b and Omp2a porins after critical assessment of transmembrane beta strands prediction by several secondary structure prediction methods

In order to propose a reliable model for Brucella porin topology, several structure prediction methods were evaluated in their ability to predict porin topology. Four porins of known structure were selected as test-cases and their secondary structure delineated. The specificity and sensitivity of 11 methods were separately evaluated. Our critical assessment shows that some secondary structure prediction methods (PHD, Dsc, Sopma) originally designed to predict globular protein structure are useful on porin topology prediction. The overall best prediction is obtained by combining these three "generalist" methods with a transmembrane beta strand prediction technique. This "consensus" method was applied to Brucella porins Omp2b and Omp2a, sharing no sequence homology with any other porin. The predicted topology is a 16-stranded antiparallel beta barrel with Omp2a showing a higher number of negatively charged residue in the exposed loops than Omp2b. Experiments are in progress to validate the proposed topology and the functional hypotheses. The ability of the proposed consensus method to predict topology of complex outer membrane protein is briefly discussed.

Structure and function prediction of the Brucella abortus P39 protein by comparative modeling with marginal sequence similarities

A methodology is proposed to solve a difficult modeling problem related to the recently sequenced P39 protein. This sequence shares no similarity with any known 3D structure, but a fold is proposed by several threading tools. The difficulty in aligning the target sequence on one of the proposed template structures is overcome by combining the results of several available prediction methods and by refining a rational consensus between them. In silico validation of the obtained model and a preliminary cross-check with experimental features allow us to state that this borderline prediction is at least reasonable. This model raises relevant hypotheses on the main structural features of the protein and allows the design of site-directed mutations. Knowing the genetic context of the P39 reading frame, we are now able to suggest a function for the P39 protein: it would act as a periplasmic substrate-binding protein.

Comparative analysis of seven multiple protein sequence alignment servers: clues to enhance reliability of predictions

MOTIVATION

The prediction reliability of seven multiple alignment servers currently available on the Internet (ClustalW, MAP, PIMA, Block Maker, MSA, MEME and Match-Box) has been evaluated in terms of power (sensitivity) and confidence (selectivity). Therefore, the alignments obtained have been respectively compared to refined structural alignments for 20 families of related proteins with low levels of identity.

RESULTS

Results clearly show that any powerful method remains reliable when the rate of identity falls. For some methods, power and confidence decrease linearly with the rate of identity, while other methods emphasize reliability at the cost of a lower power. Increasing the number of related sequences included in the alignment may either improve or decrease the quality of the predictions substantially. For some methods, the gain in power or in confidence is quite systematic; for others, the effect of the addition of homologous sequences is highly unpredictable. Extracting the consensus between two different methods may increase the overall confidence of the predictions tremendously. Our conclusions induce users of sequence alignment methods on the Internet to select the most suitable technique according to their requirements in terms of selectivity and sensitivity.

AVAILABILITY

The aligned sequences of the 20 alignments of structure can be obtained automatically by sending the message 'send: cabios_tests.txt' by e-mail to 'matchbox@biq.fundp.ac.be'.

CONTACT

eric.depiereux@fundp.ac.be

Match-Box_server: a multiple sequence alignment tool placing emphasis on reliability

MOTIVATION

The Match-Box software comprises protein sequence alignment tools based on strict statistical thresholds of similarity between protein segments. The method circumvents the gap penalty requirement: gaps being the result of the alignment and not a governing parameter of the procedure. The reliable conserved regions outlined by Match-Box are particularly relevant for homology modelling of protein structures, prediction of essential residues for site-directed mutagenesis and oligonucleotide design for cloning homologous genes by polymerase chain reaction (PCR).

RESULTS

The method produces reliable results, as assessed by tests performed on protein families of known structures and of low sequence similarity. A reliability score is computed in relation to a threshold of similarity progressively raised to extend the aligned regions to their maximal length, up to the significance limit of matching segments. The score obtained at each position is printed below the sequences and allows a discriminant reading of each aligned region.

AVAILABILITY

Sequences may be submitted to a Web server at http://www.fundp.ac.be/sciences/biologie/bms/+ ++matchbox_submit.html or sent by e-mail to matchbox/biq.fundp.ac.be (help available by just mailing help).

Bivalent cations stabilize yeast alcohol dehydrogenase I

The thermostability of yeast alcohol dehydrogenase (ADH) I is strongly dependent on the presence of NaCl, a salt that is almost neutral on the Hofmeister scale, which suggests that solvent-accessible electrostatic repulsion might play a role in the inactivation of the enzyme. Moreover, CaCl2 and MgCl2 are able to stabilize the enzyme at millimolar concentrations. Ca2+ stabilizes yeast ADH I by preventing the dissociation of the reduced form of the enzyme and by preventing the unfolding of the oxidized form of the enzyme. An analysis of several chimaeric ADHs suggests that Ca2+ is fixed by the Asp-236 and Glu-101 side chains in yeast ADH I, but that Ca2+ can be displaced by replacing Met-168 by an Arg residue, as suggested by a three-dimensional model of the enzyme structure. These results indicate that electrostatic repulsion can cause protein unfolding and/or dissociation. It is proposed that yeast ADH I binds Mg2+ in vivo.

Identification of residues potentially involved in the interactions between subunits in yeast alcohol dehydrogenases

The lack of crystal structure for tetrameric yeast alcohol dehydrogenases (ADHs) has precluded, until now, the identification of the residues involved in subunit contacts. In order to address this question, we have characterized the thermal stability and dissociation propensity of native ADH I and ADH II isozymes as well as of several chimeric (ADH I-ADH II) enzymes. Three groups of substitutions affecting the thermostability have been identified among the 24 substitutions observed between isozymes I and II. The first group contains a Cys277-->Ser substitution, located at the interface between subunits in a three-dimensional model of ADH I, based on the crystallographic structure of the dimeric horse liver ADH. In the second group, the Asp236-->Asn substitution is located in the same interaction zone on the model. The stabilizing effect of this substitution can result from the removal of a charge repulsion between subunits. It is shown that the effect of these two groups of substitutions correlates with changes in dissociation propensities. The third group contains the Met168-->Arg substitution that increases the thermal stability, probably by the formation of an additional salt bridge between subunits through the putative interface. These data suggest that at least part of the subunit contacts observed in horse liver ADH are located at homologous positions in yeast ADHs.

Knowledge-based modeling of the D-lactate dehydrogenase three-dimensional structure

A three-dimensional structure of the NAD-dependent D-lactate dehydrogenase of Lactobacillus bulgaricus is modeled using the structure of the formate dehydrogenase of Pseudomonas sp. as template. Both sequences share only 22% of identical residues. Regions for knowledge-based modeling are defined from the structurally conserved regions predicted by multiple alignment of a set of related protein sequences with low homology. The model of the D-LDH subunit shows, as for the formate dehydrogenase, an alpha/beta structure, with a catalytic domain and a coenzyme binding domain. It points out the catalytic histidine (His-296) and supports the hypothetical catalytic mechanism. It also suggests that the other residues involved in the active site are Arg-235, possibly involved in the binding of the carboxyl group of the pyruvate, and Phe-299, a candidate for stabilizing the methyl group of the substrate.

Prediction of structurally conserved regions of D-specific hydroxy acid dehydrogenases by multiple alignment with formate dehydrogenase

We propose a multiple alignment of the sequence of formate dehydrogenase with the D-specific 2-hydroxy acid dehydrogenases family. Structurally conserved regions are predicted for those sequences corresponding to important regions of the catalytic and the coenzyme binding domains defined from the known three-dimensional structure of the formate dehydrogenase, namely the nicotinamide binding site (beta D to beta F) and the beta A-loop-alpha B region containing the typical glycine pattern of the adenosine binding site, the catalytic histidine/aspartic acid pair and an arginine probably involved in the interaction with the carboxyl group of the substrate.

Effect of bilateral stimulation on spinal evoked potentials in dogs

We compared the effects of bilateral vs unilateral tibial nerve stimulation of percutaneously recorded spinal evoked potentials (SEP) in the lumbar and caudal thoracic area in dogs. The overall amplitude of the SEP is increased by this means. Use of this method could improve legibility of the recordings. Amplitudes of root and interneuronal components of the SEP are doubled as are cranially transmitted depolarizations. However, the amplitude of the SEP component arising from the primary afferents' depolarization was less than doubled. Latencies of the components were unaffected by bilateral stimulation. Careful observation of the latencies disclosed a 0.9-ms delay in transmission of the fastest component in the midlumbar area. This delay was consistent with results of previous cordotomy experiments, and could influence precision of conduction velocity measurement.