A vaccine to prevent herpes zoster and postherpetic neuralgia in older adults

BACKGROUND

The incidence and severity of herpes zoster and postherpetic neuralgia increase with age in association with a progressive decline in cell-mediated immunity to varicella-zoster virus (VZV). We tested the hypothesis that vaccination against VZV would decrease the incidence, severity, or both of herpes zoster and postherpetic neuralgia among older adults.

METHODS

We enrolled 38,546 adults 60 years of age or older in a randomized, double-blind, placebo-controlled trial of an investigational live attenuated Oka/Merck VZV vaccine ("zoster vaccine"). Herpes zoster was diagnosed according to clinical and laboratory criteria. The pain and discomfort associated with herpes zoster were measured repeatedly for six months. The primary end point was the burden of illness due to herpes zoster, a measure affected by the incidence, severity, and duration of the associated pain and discomfort. The secondary end point was the incidence of postherpetic neuralgia.

RESULTS

More than 95 percent of the subjects continued in the study to its completion, with a median of 3.12 years of surveillance for herpes zoster. A total of 957 confirmed cases of herpes zoster (315 among vaccine recipients and 642 among placebo recipients) and 107 cases of postherpetic neuralgia (27 among vaccine recipients and 80 among placebo recipients) were included in the efficacy analysis. The use of the zoster vaccine reduced the burden of illness due to herpes zoster by 61.1 percent (P<0.001), reduced the incidence of postherpetic neuralgia by 66.5 percent (P<0.001), and reduced the incidence of herpes zoster by 51.3 percent (P<0.001). Reactions at the injection site were more frequent among vaccine recipients but were generally mild.

CONCLUSIONS

The zoster vaccine markedly reduced morbidity from herpes zoster and postherpetic neuralgia among older adults.

Repression of enzymes of the pentose phosphate pathway by glucose in fission yeast

We examine here the effect of carbon sources on the synthesis of the shunt pathway enzymes in the fission yeast Schizosaccharomyces pombe growing on a mixture of ethanol and glycerol. Delta-gluconolactone induces practically every one of these enzymes. Glucose in contrast tends to attenuate the synthesis of the majority of them. RNA analysis confirms that their induction and repression reflect changes in the levels of their transcripts.

Std1, a gene involved in glucose transport in Schizosaccharomyces pombe

A wild-type strain, Sp972 h-, of Schizosaccharomyces pombe was mutagenized with ethylmethanesulfonate (EMS), and 2-deoxyglucose (2-DOG)-resistant mutants were isolated. Out of 300 independent 2-DOG-resistant mutants, 2 failed to grow on glucose and fructose (mutants 3/8 and 3/23); however, their hexokinase activity was normal. They have been characterized as defective in their sugar transport properties, and the mutations have been designated as std1-8 and std1-23 (sugar transport defective). The mutations are allelic and segregate as part of a single gene when the mutants carrying them are crossed to a wild-type strain. We confirmed the transport deficiency of these mutants by [14C]glucose uptake. They also fail to grow on other monosaccharides, such as fructose, mannose, and xylulose, as well as disaccharides, such as sucrose and maltose, unlike the wild-type strain. Lack of growth of the glucose transport-deficient mutants on maltose revealed the extracellular breakdown of maltose in S. pombe, unlike in Saccharomyces cerevisiae. Both of the mutants are unable to grow on low concentrations of glucose (10 to 20 mM), while one of them, 3/23, grows on high concentrations (50 to 100 mM) as if altered in its affinity for glucose. This mutant (3/23) shows a lag period of 12 to 18 h when grown on high concentrations of glucose. The lag disappears when the culture is transferred from the log phase of its growth on high concentrations. These mutants complement phenotypically similar sugar transport mutants (YGS4 and YGS5) reported earlier by Milbradt and Hoefer (Microbiology 140:2617-2623, 1994), and the clone complementing YGS4 and YGS5 was identified as the only glucose transporter in fission yeast having 12 transmembrane domains. These mutants also demonstrate two other defects: lack of induction and repression of shunt pathway enzymes and defective mating.

Suppression of pdc2 regulating pyruvate decarboxylase synthesis in yeast

Mutants lacking pyruvate decarboxylase cannot grow on glucose. We have isolated three different complementation groups of extragenic suppressors that suppress mutations in pdc2, a regulatory locus required for the synthesis of the glycolytic enzyme pyruvate decarboxylase. The most frequent of these is a recessive mutation in the structural gene PFK1 of the soluble phosphofructokinase. The other class XSP18 (extragenic suppressor of pdc2) is a dominant temperature-sensitive suppressor that allows the cells to grow on glucose only at 30 degrees but not at 36 degrees. It also affects the normal induction of the glucose-inducible enolase 2, which can be rescued by providing a copy of wild-type xsp18 in trans-heterozygotes. The pyruvate decarboxylase activity in the triple mutant pdc2 pfk1 XSP18 is nearly equal to the sum of the activities in the two double mutants pdc2 pfk1 and pdc2 XSP18, respectively. This implies that the two suppressors act through independent pathways or that there is no cooperativity between them. In the pdc2 pfk1 XSP18, strain, pfk1 suppresses the loss of induction of glucose-inducible enolase 2 brought about by XSP18 but fails to rescue temperature sensitivity. The third class (xsp37) supports the growth of the pdc2 mutant on glucose but fails to support growth on gluconeogenic carbon sources. All the three suppressors suppress pdc2 delta as well and act on PDC1 at the level of transcription.

Analysis of PFK3--a gene involved in particulate phosphofructokinase synthesis reveals additional functions of TPS2 in Saccharomyces cerevisiae

The pfk3 mutation of Saccharomyces cerevisiae causes glucose-negativity in a pfk1 genetic background, the mutant is temperature-sensitive for growth and homozygous diploids do not sporulate. It fails to accumulate trehalose, and has an altered glycogen accumulation profile under glucose-starvation conditions. pfk3-6, one of the alleles of pfk3, has an altered morphology, forming long chain-like structures at 36 degrees C. The PFK3 gene was cloned by complementation of the mutant phenotypes. Integrative transformation demonstrated that the complementing fragment encoded the authentic PFK3 gene. The disruption of the gene does not affect viability. Like the EMS-induced pfk3 mutant, the disruptants are temperature-sensitive and in a pfk1 genetic background are also glucose-negative. The PFK3 transcript is induced by heat-shock. Partial DNA sequence shows that PFK3 is identical to TPS2 (De Virgilio et al., 1993). We demonstrate that, apart from being a structural determinant of trehalose 6-phosphate phosphatase, PFK3 (TPS2) is required for PFKII synthesis and normal regulation of S. cerevisiae response to nutrient and thermal stresses.

Expression of the Escherichia coli xylose isomerase gene in Saccharomyces cerevisiae

Transformation of Saccharomyces cerevisiae by yeast expression plasmids bearing the Escherichia coli xylose isomerase gene leads to production of the protein. Western blotting (immunoblotting) experiments show that immunoreactive protein chains which comigrate with the E. coli enzyme are made in the transformant strains and that the amount produced parallels the copy number of the plasmid. When comparable amounts of immunologically cross-reactive xylose isomerase protein made in E. coli or S. cerevisiae were assayed for enzymatic activity, however, the yeast protein was at least 10(3)-fold less active.

Multiple genes control particulate phosphofructokinase of yeast

Mutants of Saccharomyces cerevisiae lacking the particulate phosphofructokinase define at least four unlinked genes, PFK2, PFK3, PFK4 and PFK5. A structural role of PFK2 is indicated. Mutations in the other three have pleiotropic effects.

Saccharomyces cerevisiae aldolase mutants

Six mutants lacking the glycolytic enzyme fructose 1,6-bisphosphate aldolase have been isolated in the yeast Saccharomyces cerevisiae by inositol starvation. The mutants grown on gluconeogenic substrates, such as glycerol or alcohol, and show growth inhibition by glucose and related sugars. The mutations are recessive, segregate as one gene in crosses, and fall in a single complementation group. All of the mutants synthesize an antigen cross-reacting to the antibody raised against yeast aldolase. The aldolase activity in various mutant alleles measured as fructose 1,6-bisphosphate cleavage is between 1 to 2% and as condensation of triose phosphates to fructose 1,6-bisphosphate is 2 to 5% that of the wild-type. The mutants accumulate fructose 1,6-bisphosphate from glucose during glycolysis and dihydroxyacetone phosphate during gluconeogenesis. This suggests that the aldolase activity is absent in vivo.

Mutations in the regulatory subunit of soluble phosphofructokinase from yeast

Mutant alleles of the gene PFK2 have been obtained that alter the sensitivity to ATP inhibition of the soluble yeast phosphofructokinase. One of the alleles makes the enzyme sensitive to micromolar concentrations of ATP. Intragenic revertants of PFK2 mutants confirm that the PFK2 gene determines not only the regulatory properties of the soluble enzyme but also the catalytic activity of particulate phosphofructokinase.

Genetics of yeast glucokinase

Mutants of Saccharomyces cerevisiae lacking glucokinase (EC 2.7.1.2) have no discernible phenotypic difference from the wild-type strain; in a hexokinaseless background, however, they are unable to grow on any sugar except galactose. Reversion studies with glucokinase mutants indicate that the yeast S. cerevisiae has no other enzyme for phosphorylating glucose except the two hexokinases, P1 and P2, and glucokinase. Spontaneous revertants of hxk1 hxk2 glk1 strains collected on glucose regain any one of these three enzymes. The majority of glucokinase revertants synthesize species of enzyme activity that are kinetically or otherwise indistinguishable from the wild-type enzyme. In a few cases the reverted enzyme is very perceptibly altered in properties with a Km for glucose two orders of magnitude higher than that of the enzyme from the wild-type parent. These recessive, noncomplementing mutants, thus, define a single structural gene GLK1 of glucokinase. Yeast diploids lacking all of the three enzymes for glucose phosphorylation fail to sporulate. Heterozygosity of either of the hexokinase genes HXK1 or HXK2, but not GLK1, restores sporulation. The location of GLK1 on chromosome III was indicated by loss of this chromosome when hexokinaseless diploids heterozygous for glk1 were selected for resistance to 2-deoxyglucose; the homologue of chromosome III carrying GLK1, the mating-type allele and other nutritional markers on this chromosome was lost. Meiotic mapping of glucokinase executed with heterozygosity of one of the hexokinases indicated that the gene GLK1 defining the structure of glucokinase protein is located on the left arm of chromosome III 24 cM to the left of his4 in the order: leu2--his4--glk1. --Only two of 206 independent glucokinase mutants are nonsense ochre, both of which map at one end of the gene. In hxk1 only one of 130 isolates is a nonsense mutation, whereas in hxk2 none has been found among 220 independent mutants. These results raise the possibility that the protein products of these genes have some other essential function. --An earlier mapping result for hxk2 has been corrected. The new location is on the left arm of chromosome VII, 17 cM distal to ade5 in the order: lys5--ade5--hxk2.

Phosphofructokinase mutants of yeast. Biochemistry and genetics

Mutants of Saccharomyces cerevisiae completely lacking the soluble glycolytic enzyme fructose-6-P kinase are described. The mutations are semidominant, do not complement one another, and define a gene PFK1 located 28-cm distal to rna1 on the extended right arm of chromosome XIII. Of 10 independent mutants, 3 can be suppressed by ochre suppressors. All mutants examined synthesize proteins that cross-react to the antibody against the purified yeast P-fructokinase. The enzyme in spontaneous revertants is distinguishable from the wild type enzyme with respect to thermolability and ATP inhibition. The locus PFK1 thus defines the structural gene of the enzyme. The pfk1 mutants are not leaky in vivo. All the glucose consumed by a double mutant lacking both P-fructokinase and 6-P-gluconate dehydrogenase ends up as 6-P-gluconate, yet the pfk1 mutants can glycolyze and grow on glucose in air. The cell mass produced per unit of glucose also remains unchanged. Anaerobically, however, growth does not take place, nor does glycolysis. P-fructokinase is thus a dispensable enzyme for aerobic growth, but indispensable for anaerobic growth. The properties of pfk1 mutants suggest that yeast has an alternative mechanism for the aerobic metabolism of fructose-6-P, presumably through the recently reported particulate P-fructokinase (Lobo, Z., and Maitra, P. K. (1982) FEBS Lett. 137, 279-282).

Pentose phosphate pathway mutants of yeast

A glucose-negative mutant of Saccharomyces cerevisiae lacking 6-phosphogluconate dehydrogenase, the second enzyme of the pentose phosphate pathway, has been obtained by inositol starvation. Suppression of this mutant for growth on glucose takes place by the loss of glucose 6-phosphate dehydrogenase. A lesion in the latter enzyme alone leaves growth practically unaffected. The mutations define the respective structural genes.

Resistance to 2-deoxyglucose in yeast: a direct selection of mutants lacking glucose-phosphorylating enzymes

When strains of Saccharomyces cerevisiae carrying a single glucose-phosphorylating enzyme such as hexokinase Pl or hexokinase P2 or glucokinase, are subjected to the selection pressure against the toxic sugar 2-deoxyglucose, the majority of survivors are mutants lacking the respective enzymes. All the 2-deoxyglucose-resistant segregants recovered from backcrosses of these mutants to a wild type strain are glucose-negative and all the sensitive ones are glucose-positive. The hexokinase mutations are located in the same complementation groups as defined by the structural genes of hexokinase P1 and hexokinase P2. No interallelic complementation has been observed either in hexokinase P1 or in hexokinase P2 amongst a total of 4 X 64, and 5 X 60 different combinations of independent mutants at the hxk1 and hxk2 loci respectively. There appears to be neither a common genetic regulator controlling two or more of these glucose-phosphorylating enzymes nor a sugar carrier that can be dispensed with.

Molecular properties of yeast glucokinase

Glucokinase from baker's yeast has been purified to homogeneity. The molecular weight of the subunit is 51,000. The native enzyme sediments with S20,w values in the range of 19 to nearly 4S. The presence of glucose and phosphate favors the heavier species while ATP causes depolymerization. Titration experiments with the Ellman reagent support this view. The enzyme subunit has four sulfhydryl residues of which one is more reactive than the other three. However, it does not seem to be directly responsible for the catalytic activity. The amino acid composition of the enzyme is similar to those of the hexokinases P1 and P2 but for aspartic acid and histidine.

Genetic studies with a phosphoglucose isomerase mutant of Saccharomyces cerevisiae

A mutation pgi1 in the yeast Saccharomyces cerevisiae conferring deficiency of the glycolytic enzyme glucose 6-phosphate isomerase is characterised genetically. The mutation segregates 2+:2- in tetrads from diploids heterozygous for the mutant phenotype. The mutation is semi-dominant and is located on the right arm of chromosome II in the order: tsm134--lys2--pgi1--tyr1 approximately 15 map units from tyr1. The mutation pgi1 defines the structural gene of glucose 6-phosphate isomerase and can be suqpressed intragenically giving revertants that have an unstable enzyme. In one temperature-sensitive revertant no enzyme activity in excess of the mutant level could be detected although fructose 6-phosphate was converted to glucose 6-phosphate in vivo. The suppressor locus in this revertant is dominant and is unlinked to the pgi1 locus.

Yeast pyruvate kinase: a mutant from catalytically insensitive to fructose 1,6-bisphosphate

The paper describes some of the characteristic properties of an altered form of pyruvate kinase from a mutant of Saccharomyces cerevisiae. The partially purified enzyme does not require fructose 1,6-bisphosphate for activity but is stabilised in its presence both at low and at high temperatures. The enzyme displays in the absence of fructose 1,6-bisphosphate hyperbolic kinetics with phosphoenolpyruvate (Km, 0.11 mM), ADP (Km, 0.12 mM) and K+ (Km, 11 mM). Sedimentation velocity experiments indicate that the mutated enzyme and the wild type enzyme have S20,w values of 8.9 and 8.6 S respectively. The mutant with the pyruvate insensitive to fructose 1.6-bisphosphate is capable of growing on synthetic media with alcohol or malate as the sole carbon source. The steady-state intracellular levels of phosphoenolpyruvate in the mutant suggest mechanisms that prevent depletion of this metabolite despite an active pyruvate kinase. Spontaneous reversion of this mutant yields clones with normal enzyme activated by fructose 1,6-bisphosphate.

GENETICS OF YEAST HEXOKINASE

Two independent isolates of Saccharomyces cerevisiae lacking hexokinase activity (EC 2.7.1.1) are described. Both mutant strains grow on glucose but are unable to grow on fructose, and contain two mutant genes h×k1 and h×k2 each. The mutations are recessive and noncomplementing. Genetic analysis suggests that these two unlinked genes h×k1 and h×k2 determine, independently of each other, the synthesis of hexokinase isozymes P1 and P2, respectively. h×k1 is located on chromosome VIR distal to met10, and h×k2 is on chromosome IIIR distal to MAL2. Of four hexokinase-positive spontaneous reversions, one is very tightly linked to h×k1 and the other three to the h×k2 locus. The reverted enzymes are considerably more thermolabile than the respective wild-type enzymes, and in one case show altered immunological properties. Data are presented which suggest that the h×k1 and h×k2 mutations are missense mutations in the structural genes of hexokinase P1 and hexokinase P2, respectively. These are presumably the only enzymes that allow S. cerevisiae to grow on fructose.

Pyruvate kinase mutants of Saccharomyces cerevisiae: biochemical and genetic characterisation

Mutants of Saccharomyces cerevisiae lacking pyruvate kinase (EC 2.7.1.40) are described. These have less than 0.5% of the pyruvate kinase activity of the wild type. All the other glycolytic enzymes are present in normal amounts in these mutants. The mutation is recessive and segregates in diploids as a single gene. Five alleles examined fail to complement one another. Tetrad analysis and mitotic recombination data place the mutation on the left arm of chromosome I distal to cys 1. The majority of single-step spontaneous revertants on glucose regain the enzyme activity fully and this activity appears, by a number of criteria, to be due to the same enzyme present in the wild type. Some of these revertants become nuclear petites. The mutants do neither grow on nor ferment sugars but do grow on ethyl alcohol or pyruvate. Glucose addition to cultures growing on alcohol arrests growth until glucose is exhausted. The steady state rate of glucose utilization is slower than in the wild type. This is associated with the accumulation of as much as 5 micronmoles P-enolpyruvate per g wet weight of cells and proportional amounts of 2-P-glyceric and 3-P glyceric acids. The mutation is believed to involve some regulatory element in the synthesis of pyruvate kinase.