Development of Respiratory Syncytial Virus Vaccine Candidates for the Elderly

Respiratory syncytial virus (RSV) is a significant threat to elderly populations and repeated infections that occur throughout life are poorly protective. To assess the role of prior RSV infections as well as elderly immune senescence on vaccine efficacy, we compared immune responses after virus-like particle (VLP) immunization of elderly cotton rats and young cotton rats, both previously RSV infected, in order to mimic the human population. We show that immunization of RSV-experienced young or elderly animals resulted in the same levels of anti-pre-F IgG, anti-G IgG, neutralizing antibody titers, and protection from challenge indicating that the delivery of F and G proteins in a VLP is equally effective in activation of protective responses in both elderly and young populations. Our results suggest that F and G protein-containing VLPs induce anti-RSV memory established in prior RSV infections equally well in both young and elderly animals and thus can be an effective vaccine for the elderly.

Correlative outcomes of maternal immunization against RSV in cotton rats

Maternal anti-respiratory syncytial virus (RSV) antibodies protect neonates from RSV disease throughout first weeks of life. Previous studies of maternal immunization in cotton rats showed that a single immunization during pregnancy of RSV-primed dams with virus-like particles (VLPs) assembled with pre-fusion F protein and the wild type G protein boosted their RSV serum antibody concentration and protected pups early in life against RSV challenge. We extended these findings by evaluating responses to RSV infection in litters from two consecutive pregnancies of immunized dams. Using an RSV-primed population of VLP-vaccinated and unvaccinated dams, we defined correlations between dams' and litters' RSV neutralizing antibodies (NA); between litters' NA and protection; and between litter's NA and their lung expression of selected cytokines, of a first or of a second pregnancy. Lung pathology was also evaluated. We found positive correlation between the NA titers in the dams at delivery and the NA in their first and second litters and negative correlations between the litters' NA and protection from RSV challenge. Vaccination of dams modulated the mRNA expression for IFNγ and IL-6 and lung pathology in the first and in the second litter at different times after birth, even in the absence of detectable NA. Maternal RSV vaccination enhanced the levels of antibodies transferred to offspring and their protection from challenge. Importantly, maternal vaccination also impacted the immunological and inflammatory response of the offspring's lungs well into maturity, and after the antiviral effect of maternally transferred NA waned or was no longer detectable.

Evolution of protection after maternal immunization for respiratory syncytial virus in cotton rats

Maternal anti-respiratory syncytial virus (RSV) antibodies acquired by the fetus through the placenta protect neonates from RSV disease through the first weeks of life. In the cotton rat model of RSV infections, we previously reported that immunization of dams during pregnancy with virus-like particles assembled with mutation stabilized pre-fusion F protein as well as the wild type G protein resulted in robust protection of their offspring from RSV challenge. Here we describe the durability of those protective responses in dams, the durability of protection in offspring, and the transfer of that protection to offspring of two consecutive pregnancies without a second boost immunization. We report that four weeks after birth, offspring of the first pregnancy were significantly protected from RSV replication in both lungs and nasal tissues after RSV challenge, but protection was reduced in pups at 6 weeks after birth. However, the overall protection of offspring of the second pregnancy was considerably reduced, even at four weeks of age. This drop in protection occurred even though the levels of total anti-pre-F IgG and neutralizing antibody titers in dams remained at similar, high levels before and after the second pregnancy. The results are consistent with an evolution of antibody properties in dams to populations less efficiently transferred to offspring or the less efficient transfer of antibodies in elderly dams.

Comparison of Immune Responses to Different Versions of VLP Associated Stabilized RSV Pre-Fusion F Protein

Efforts to develop a vaccine for respiratory syncytial virus (RSV) have primarily focused on the RSV fusion protein. The pre-fusion conformation of this protein induces the most potent neutralizing antibodies and is the focus of recent efforts in vaccine development. Following the first identification of mutations in the RSV F protein (DS-Cav1 mutant protein) that stabilized the pre-fusion conformation, other mutant stabilized pre-fusion F proteins have been described. To determine if there are differences in alternate versions of stabilized pre-fusion F proteins, we explored the use, as vaccine candidates, of virus-like particles (VLPs) containing five different pre-fusion F proteins, including the DS-Cav1 protein. The expression of these five pre-F proteins, their assembly into VLPs, their pre-fusion conformation stability in VLPs, their reactivity with anti-F monoclonal antibodies, and their induction of immune responses after the immunization of mice, were characterized, comparing VLPs containing the DS-Cav1 pre-F protein with VLPs containing four alternative pre-fusion F proteins. The concentrations of anti-F IgG induced by each VLP that blocked the binding of prototype monoclonal antibodies using two different soluble pre-fusion F proteins as targets were measured. Our results indicate that both the conformation and immunogenicity of alternative VLP associated stabilized pre-fusion RSV F proteins are different from those of DS-Cav1 VLPs.

The importance of RSV F protein conformation in VLPs in stimulation of neutralizing antibody titers in mice previously infected with RSV

Respiratory syncytial virus (RSV) is a significant respiratory pathogen but no vaccine is available. RSV infections present 2 major, unique problems. First, humans can experience repeated infections caused by the same virus sero-group indicating that protective memory responses to RSV infection are defective. Second, most people have been infected with RSV by age 5. Immune responses to these infections, while poorly protective, could impact the effectiveness of a vaccine. The goal of this study was to assess the generation of protective immune responses in mice previously infected with RSV by virus-like particle (VLP) vaccine candidates containing a stabilized pre-fusion form of the RSV F protein or a stabilized post-fusion F protein. We report that a single immunization of RSV-experienced animals with a stabilized pre-fusion F protein VLP stimulated high titers of neutralizing antibody while a single injection of a post-fusion F protein VLP or a second RSV infection only weakly stimulated neutralizing antibody titers. These results suggest that prior RSV infection can induce neutralizing antibody memory responses, which can be activated by pre-F protein VLPs but not by post-F protein VLPs or a subsequent infection. Thus the F protein conformation has a major impact on enhancing production of neutralizing antibodies in RSV-experienced animals. Furthermore, although both VLPs contained the same RSV G protein, the pre-F VLP stimulated significantly higher titers of total anti-G protein IgG than the post-F VLP in both naïve and RSV-experienced animals. Thus the F protein conformation also influences anti-G protein responses.

Genetic variation in the promoter and 5' UTR of the copper transporter, ATP7B, in patients with Wilson disease

ATP7B is a copper-transporting P-type ATPase defective in the copper transport disorder, Wilson disease (WND). We have sequenced the 5' UTR and promoter region of ATP7B in 37 unrelated WND patients in whom partial sequencing of the coding region and intron/exon boundaries of the gene had failed to identify one or both disease-causing mutations. Three patients were found to be heterozygous for a 15 bp deletion between nucleotides -424 and -441. This deletion had been previously identified as the most common mutation in Sardinian WND patients. Two novel single-nucleotide changes were also identified within the 5' UTR and promoter of ATP7B; however, these were found at a similar frequency in control chromosomes and are apparently normal variants. These results suggest that mutations in regulatory elements of ATP7B are uncommon in patients of European ancestry, except in Sardinia.

Localization, expression and genomic structure of the gene encoding the human serine protease testisin

Testisin is a recently identified human serine protease expressed by premeiotic testicular germ cells and is a candidate tumor suppressor for testicular cancer. Here, we report the characterization of the gene encoding testisin, designated PRSS21, and its localization on the short arm of human chromosome 16 (16p13.3) between the microsatellite marker D16S246 and the radiation hybrid breakpoint CY23HA. We have further refined the localization to cosmid 406D6 in this interval and have established that the gene is approximately 4. 5 kb in length, and contains six exons and five intervening introns. The structure of PRSS21 is very similar to the human prostasin gene (PRSS8) which maps nearby on 16p11.2, suggesting that these genes may have evolved through gene duplication. Sequence analysis showed that the two known isoforms of testisin are generated by alternative pre-mRNA splicing. A major transcription initiation site was identified 97 nucleotides upstream of the testisin translation start and conforms to a consensus initiator element. The region surrounding the transcription initiation site lacks a TATA consensus sequence, but contains a CCAAT sequence and includes a CpG island. The 5'-flanking region contains several consensus response elements including Sp1, AP1 and several testis-specific elements. Analysis of testisin gene expression in tumor cell lines shows that testisin is not expressed in testicular tumor cells but is aberrantly expressed in some tumor cell lines of non-testis origin. These data provide the basis for identifying potential genetic alterations of PRSS21 that may underlie both testicular abnormalities and tumorigenesis.

Effects of HFE C282Y and H63D polymorphisms and polygenic background on iron stores in a large community sample of twins

The aim of this study was to assess and to compare the role of HFE polymorphisms and other genetic factors in variation in iron stores. Blood samples were obtained from 3,375 adult male and female twins (age range 29-82 years) recruited from the Australian Twin Registry. There were 1,233 complete pairs (562 monozygotic and 571 dizygotic twins). Serum iron, transferrin, transferrin saturation with iron, and ferritin were measured, and the HFE C282Y and H63D genotypes were determined. The frequency of the C282Y allele was.072, and that of the H63D allele was.141. Significant sources of variation in the indices of iron status included age, sex, age-sex interaction, body-mass index, and both the C282Y and H63D genotypes. The iron, transferrin, and saturation values of CC and CY subjects differed significantly, but the ferritin values did not. After correction for age and body-mass index, 23% and 31% of the variance in iron, 66% and 49% of the variance in transferrin, 33% and 47% of the variance in transferrin saturation, and 47% and 47% of the variance in ferritin could be explained by additive genetic factors, for men and women, respectively. HFE C282Y and H63D variation accounted for <5% of the corrected phenotypic variance, except for saturation (12% in women and 5% in men). We conclude that HFE CY and HD heterozygotes differ in iron status from the CC and HH homozygotes and that serum transferrin saturation is more affected than is serum ferritin. There are highly significant effects of other as-yet-unidentified genes on iron stores, in addition to HFE genotype.

Isolation and characterisation of cosmids to intervals within a 4.5Mb region at 6p21.3

The gene responsible for hereditary haemochromatosis (HH) has recently been identified. One mutation in this gene, termed HFE, has been found in all Australian HH patients. We previously identified a predominant HH ancestral haplotype covering 4.5Mb at 6p21.3, and showed that patients with two copies of this haplotype express a more severe form of the disorder. One key question to now be resolved is why haplotype related variation in phenotypic expression of HH is present if all patients tested have the same HFE mutation. A cosmid resource covering the 4.5Mb HH ancestral haplo type region was obtained. These cosmids provide the material for the completion of a transcript map of this region, and will assist the identification of candidate modifiers of HFE expression.

Genetics of hemochromatosis

Hereditary hemochromatosis (HHC) is a common autosomal recessive disorder of iron metabolism that results in progressive iron overload and can be fatal if untreated. The hemochromatosis gene (HFE) was identified by positional cloning in 1996. Two missense mutations have been described in HFE. The majority of HHC patients are homozygous for a cysteine-to-tyrosine substitution (C282Y); however, a small number are homozygous for a histidine-to-aspartic-acid substitution (H63D) or are heterozygous for both of these mutations. Mechanisms by which C282Y and H63D may disrupt the normal functioning of HFE have been suggested, but the role of HFE in the process of normal iron metabolism has yet to be clearly defined.

Generation of a transcription map distal to HLA-F

We have constructed a transcription map covering a 2 Mb region beginning approximately 1 Mb distal to HLA-F. Cosmids isolated from a chromsome 6 library were positioned by YAC hybridisation, STS and fingerprint analysis. Using direct cDNA selection, exon trapping, and direct genomic sequence analysis, we identified 42 potential exonic fragments in this region. Six fragments corresponded to previously characterised genes, four previously broadly mapped to this region. Five fragments were similar to known genes, eight fragments matched ESTs and 10 of the remaining 23 novel fragments, gave a positive signal on northern analysis. All cDNA fragments were mapped to the YAC and cosmid contig covering the region and with respect to other known genes and STS in this area. The distribution of the cDNA fragments indicated their organisation in three clusters around CpG islands.

The hemochromatosis 845 G-->A and 187 C-->G mutations: prevalence in non-Caucasian populations

Hemochromatosis, the inherited disorder of iron metabolism, leads, if untreated, to progressive iron overload and premature death. The hemochromatosis gene, HFE, recently has been identified, and characterization of this gene has shown that it contains two mutations that result in amino acid substitutions-cDNA nucleotides 845 G-->A (C282Y) and 187 C-->G (H63D). Although hemochromatosis is common in Caucasians, affecting >=1/300 individuals of northern European origin, it has not been recognized in other populations. The present study used PCR and restriction-enzyme digestion to analyze the frequency of the 845 G-->A and 187 C-->G mutations in HLA-typed samples from non-Caucasian populations, comprising Australian Aboriginal, Chinese, and Pacific Islanders. Results showed that the 845 G-->A mutation was present in these populations (allele frequency 0.32%), and, furthermore, it was always seen in conjunction with HLA haplotypes common in Caucasians, suggesting that 845 G-->A may have been introduced into these populations by Caucasian admixture. 187 C-->G was present at an allele frequency of 2.68% in the two populations analyzed (Australian Aboriginal and Chinese). In the Australian Aboriginal samples, 187 C-->G was found to be associated with HLA haplotypes common in Caucasians, suggesting that it was introduced by recent admixture. In the Chinese samples analyzed, 187 C-->G was present in association with a wide variety of HLA haplotypes, showing this mutation to be widespread and likely to predate the more genetically restricted 845 G-->A mutation.

Expression of HLA-linked hemochromatosis in subjects homozygous or heterozygous for the C282Y mutation

BACKGROUND & AIMS

In the absence of a genetic test, diagnostic criteria for hereditary hemochromatosis have been imprecise. The identification of the HFE gene and the C282Y mutation allow definition of expression of this disease and reassessment of diagnostic criteria. The aim of this study was to analyze the concordance between the genetic diagnosis and the previous clinical diagnosis in families with hemochromatosis.

METHODS

Three hundred subjects were tested for the C282Y mutation and were grouped as homozygous, heterozygous, or homozygous normal.

RESULTS

All adults previously diagnosed as homozygous or heterozygous for HLA-linked hereditary hemochromatosis carried at least one C282Y mutation. Two adolescents, previously thought to be homozygous, had no C282Y mutation. Of 127 subjects homozygous for the mutation, 105 met criteria for diagnosis. Iron overload was not expressed in 6.7% of homozygous men and 32.7% of homozygous women. The iron indices in 8 of 171 subjects heterozygous for the C282Y mutation were within the range previously regarded as indicative of homozygosity. Seven of these 8 carried the H63D mutation.

CONCLUSIONS

In Australia, 17.3% of subjects homozygous for the C282Y mutation do not express iron overload to meet current diagnostic criteria of hemochromatosis. In subjects heterozygous for the mutation, 4.8% have iron overload in the range previously diagnosed as homozygous. Nonexpression is common, particularly in women.

Genetic variation in the COL6A1 region is associated with congenital heart defects in trisomy 21 (Down's syndrome)

Genetic variation in the COL6A1-COL6A2 gene cluster on chromosome 21 was studied in 113 controls and 58 European families (including control and family subgroups of British/Irish origin) having a child with trisomy 21. There were statistically significant differences among subgroups of trisomic children with and without congenital heart defects (CHD) in distributions of definitive, 3-RFLP haplotype classes received from their nondisjoining and disjoining parents. Haplotypes received by trisomic children with CHD from their disjoining parents were not a random sample of controls' haplotypes. Analysis of parental single-RFLP genotypes and linkage disequilibrium patterns confirmed this parent subgroup differed from a random sample of controls. There were no significant differences in parent subgroup genotype distribution at any of nine control loci distributed along chromosome 21q. This sample showed an association between genetic variation in the COL6A1 gene region and congenital heart defects in trisomy 21.

Unusual genotypes in the COL6A1 gene in parents of children with trisomy 21 and major congenital heart defects

Collagen type VI is a candidate for a role in the pathogenesis of congenital heart defects (CHD) in Down's syndrome. Three restriction fragment length polymorphisms of the COL6A1 gene were used to determine COL6A1 genotypes in 50 families of affected children with trisomy 21 (29 with congenital heart defects and 21 without) and 37 unrelated volunteers. We found seven unusual genotypes in the parents of affected children with Down's syndrome, five being unique to the parents of children with trisomy 21 and CHD. There were no unusual genotypes associated with other chromosome 21 loci. No single COL6A1 genotype was associated with CHD. Thus, the unusual genotypes unique to parents of affected children suggest that genetic variation in the COL6A1 gene region contributes to the pathogenesis of CHD in Down's syndrome.

Meiotic crossing-over in nondisjoined chromosomes of children with trisomy 21 and a congenital heart defect

We have used DNA polymorphisms to study meiotic crossovers of chromosome 21q in 27 nuclear families. Each family had a child with Down syndrome and a congenital heart defect. Twenty DNA polymorphisms on chromosome 21 were used to determine parental and meiotic origin of nondisjunction and to identify crossovers. Twenty-four cases were of maternal origin, and three were of paternal origin. Twenty-two unequivocal crossover events were identified. Sixteen crossovers were observed in 22 chromosome pairs nondisjoining at the second meiotic division. Fifty percent of crossover events in MI nondisjunction are detectable by molecular genetic means. Thus, the results suggest that, in this sample, each nondisjoined chromosome 21 pair has been involved in at least one crossover event.