Variability in immune response to pathogens: using measles vaccine to probe immunogenetic determinants of response

Determinants of effective vaccine coverage in low and middle-income countries: a systematic review and interpretive synthesis

BACKGROUND

Many children in low and middle-income countries remain unvaccinated, and vaccines do not always produce immunity. Extensive research has sought to understand why, but most studies have been limited in breadth and depth. This study documents existing evidence on determinants of vaccination and immunization and presents a conceptual framework of determinants.

METHODS

We used systematic review, content analysis, thematic analysis and interpretive synthesis to document and analyze the existing evidence on determinants of childhood vaccination and immunization.

RESULTS

We documented 1609 articles, including content analysis of 78 articles. Three major thematic models were described in the context of one another. Interpretive synthesis identified similarities and differences between studies, resulting in a conceptual framework with three principal vaccine utilization determinants: 1) Intent to Vaccinate, 2) Community Access and 3) Health Facility Readiness.

CONCLUSION

This study presents the most comprehensive systematic review of vaccine determinants to date. The conceptual framework represents a synthesis of multiple existing frameworks, is applicable in low and middle-income countries, and is quantitatively testable. Future researchers can use these results to develop competing conceptual frameworks, or to analyze data in a theoretically-grounded way. This review enables better research in the future, further understanding of immunization determinants, and greater progress against vaccine preventable diseases around the world.

MicroRNAs and Their Targets Are Differentially Regulated in Adult and Neonatal Mouse CD8+ T Cells

Immunological memory, which protects organisms from re-infection, is a hallmark of the mammalian adaptive immune system and the underlying principle of vaccination. In early life, however, mice and other mammals are deficient at generating memory CD8+ T cells, which protect organisms from intracellular pathogens. The molecular basis that differentiates adult and neonatal CD8+ T cells is unknown. MicroRNAs (miRNAs) are both developmentally regulated and required for normal adult CD8+ T cell functions. We used next-generation sequencing to identify mouse miRNAs that are differentially regulated in adult and neonatal CD8+ T cells, which may contribute to the impaired development of neonatal memory cells. The miRNA profiles of adult and neonatal cells were surprisingly similar during infection; however, we observed large differences prior to infection. In particular, miR-29 and miR-130 have significant differential expression between adult and neonatal cells before infection. Importantly, using RNA-Seq, we detected reciprocal changes in expression of messenger RNA targets for both miR-29 and miR-130. Moreover, targets that we validated include Eomes and Tbx21, key genes that regulate the formation of memory CD8+ T cells. Notably, age-dependent changes in miR-29 and miR-130 are conserved in human CD8+ T cells, further suggesting that these developmental differences are biologically relevant. Together, these results demonstrate that miR-29 and miR-130 are likely important regulators of memory CD8+ T cell formation and suggest that neonatal cells are committed to a short-lived effector cell fate prior to infection.

Genetics and vaccines in the era of personalized medicine

Vaccines represent the most successful and sustainable tactic to prevent and counteract infection. A vaccine generally improves immunity to a particular disease upon administration by inducing specific protective and efficient immune responses in all of the receiving population. The main known factors influencing the observed heterogeneity for immune re-sponses induced by vaccines are gender, age, co-morbidity, immune system, and genetic background. This review is mainly focused on the genetic status effect to vaccine immune responses and how this could contribute to the development of novel vaccine candidates that could be better directed and predicted relative to the genetic history of an individual and/or population. The text offers a brief history of vaccinology as a field, a description of the genetic status of the most relevant and studied genes and their functionality and correlation with exposure to specific vaccines; followed by an inside look into autoimmunity as a concern when designing vaccines as well as perspectives and conclusions looking towards an era of personalized and predictive vaccinology instead of a one size fits all approach.

Hunting for immune response regulatory genes: vaccination studies in infant twins

The contribution of twin studies towards unraveling the complex mechanisms of multifactorial diseases is increasingly recognized. Recent twin studies using infant vaccination as a model for infectious diseases have confirmed the importance of host genetic factors as major regulators of the immune response. A combination of twin-based family studies and population-based association studies should lead to the identification of the specific genes involved. These genes and their products have the potential to be developed as targets for novel therapeutic and prophylactic agents against infectious diseases.

Genetic variants within the MHC region are associated with immune responsiveness to childhood vaccinations

The influence of genetic variability within the major histocompatibility complex (MHC) region on variations in immune responses to childhood vaccination was investigated. The study group consisted of 135 healthy infants who had been immunized with hepatitis B (HBV), 7-valent pneumococcal conjugate (PCV7), and diphtheria, tetanus, acellular pertussis (DTaP) vaccines according to standard childhood immunization schedules. Genotype analysis was performed on genomic DNA using Illumina Goldengate MHC panels (Mapping and Exon Centric). At the 1 year post vaccination check-up total, isotypic, and antigen-specific serum antibody levels were measured using multiplex immunoassays. A number of single nucleotide polymorphisms (SNPs) within MHC Class I and II genes were found to be associated with variations in the vaccine specific antibody responses and serum levels of immunoglobulins (IgG, IgM) and IgG isotypes (IgG1, IgG4) (all at p<0.001). Linkage disequilibrium patterns and functional annotations showed that significant SNPs were strongly correlated with other functional regulatory SNPs. These SNPs were found to regulate the expression of a group of genes involved in antigen processing and presentation including HLA-A, HLA-C, HLA-G, HLA-H, HLA-DRA, HLA-DRB1, HLA-DRB5, HLA-DQA1, HLA-DQB1, HLA-DOB, and TAP-2. The results suggest that genetic variations within particular MHC genes can influence immune response to common childhood vaccinations, which in turn may influence vaccine efficacy.

Genomic correlates of variability in immune response to an oral cholera vaccine

Cholera is endemic to many countries. Recent major outbreaks of cholera have prompted World Health Organization to recommend oral cholera vaccination as a public-health strategy. Variation in percentage of seroconversion upon cholera vaccination has been recorded across populations. Vaccine-induced responses are influenced by host genetic differences. We have investigated association between single-nucleotide polymorphic (SNP) loci in and around 296 immunologically relevant genes and total anti-lipopolysaccharide (LPS) antibody response to a killed whole-cell vaccine, comprising LPS from multiple strains of Vibrio cholerae. Titers derived from standard vibriocidal assays were also analyzed to gain further insights on validated SNP associations. Vaccination was administered to 1000 individuals drawn from India. Data on two independent random subsets, each comprising ∼500 vaccinees, were used for discovery of genomic associations and validation, respectively. Significant associations of four SNPs and haplotypes in three genes (MARCO, TNFAIP3 and CXCL12) with AR were discovered and validated, of which two in TNFAIP3 and CXCL12 were also significantly associated with immunity (fourfold increase in vibriocidal titers). CXCL12 is a neutrophil and lymphocyte chemoattractant that is upregulated in response to V. cholerae infection. LPS in the vaccine possibly provides signals that mimic those of the live bacterium. TNFAIP3 promotes intestinal epithelial barrier integrity and provides tight junction protein regulation; possible requirements for adequate response to the vaccine. LPS is a potent activator of innate immune responses and a ligand of MARCO. Variants in this gene have been found to be associated with LPS response, but not with high vibriocidal titer level.

Toxicogenomic profiles in relation to maternal immunotoxic exposure and immune functionality in newborns

A crucial period for the development of the immune system occurs in utero. This results in a high fetal vulnerability to immunotoxic exposure, and indeed, immunotoxic effects have been reported, demonstrating negative effects on immune-related health outcomes and immune functionality. Within the NewGeneris cohort BraMat, a subcohort of the Norwegian Mother and Child Cohort Study (MoBa), immunotoxicity was demonstrated for polychlorinated biphenyls and dioxins, showing associations between estimated maternal intake levels and reduced measles vaccination responses in the offspring at the age of 3. The present study aimed to investigate this link at the transcriptomic level within the same BraMat cohort. To this end, whole-genome gene expression in cord blood was investigated and found to be associated with maternal Food Frequency Questionnaires-derived exposure estimates and with vaccination responses in children at 3 years of age. Because the literature reports gender specificity in the innate, humoral, and cell-mediated responses to viral vaccines, separate analysis for males and females was conducted. Separate gene sets for male and female neonates were identified, comprising genes significantly correlating with both 2,3,7,8-tetrachlorodibenzodioxin (TCDD) and polychlorinated biphenyls (PCB) exposure and with measles vaccination response. Noteworthy, genes correlating negatively with exposure in general show positive correlations with antibody levels and vice versa. For both sexes, these included immune-related genes, suggesting immunosuppressive effects of maternal exposure to TCDD and PCB at the transcriptomic level in neonates in relation to measles vaccination response 3 years later.

Polymorphisms in Toll-like receptor genes influence antibody responses to cytomegalovirus glycoprotein B vaccine

Background

Congenital Cytomegalovirus (CMV) infection is an important medical problem that has yet no current solution. A clinical trial of CMV glycoprotein B (gB) vaccine in young women showed promising efficacy. Improved understanding of the basis for prevention of CMV infection is essential for developing improved vaccines.

Results

We genotyped 142 women previously vaccinated with three doses of CMV gB for single nucleotide polymorphisms (SNPs) in TLR 1-4, 6, 7, 9, and 10, and their associated intracellular signaling genes. SNPs in the platelet-derived growth factor receptor (PDGFRA) and integrins were also selected based on their role in binding gB. Specific SNPs in TLR7 and IKBKE (inhibitor of nuclear factor kappa-B kinase subunit epsilon) were associated with antibody responses to gB vaccine. Homozygous carriers of the minor allele at four SNPs in TLR7 showed higher vaccination-induced antibody responses to gB compared to heterozygotes or homozygotes for the common allele. SNP rs1953090 in IKBKE was associated with changes in antibody level from second to third dose of vaccine; homozygotes for the minor allele exhibited lower antibody responses while homozygotes for the major allele showed increased responses over time.

Conclusions

These data contribute to our understanding of the immunogenetic mechanisms underlying variations in the immune response to CMV vaccine.

Genetic determinants of immune-response to a polysaccharide vaccine for typhoid

Differences in immunological response among vaccine recipients are determined both by their genetic differences and environmental factors. Knowledge of genetic determinants of immunological response to a vaccine can be used to design a vaccine that circumvents immunogenetic restrictions. The currently available vaccine for typhoid is a pure polysaccharide vaccine, immune response to which is T-cell independent. Little is known about whether genetic variation among vaccinees associates with variation in their antibody response to a polysaccharide vaccine. We conducted a study on 1,000 individuals resident in an area at high-risk for typhoid; vaccinated them with the typhoid vaccine, measured their antibody response to the vaccine, assayed >2,000 curated SNPs chosen from 283 genes that are known to participate in immune-response; and analyzed these data using a strategy to (a) minimize the statistical problems associated with testing of multiple hypotheses, and (b) internally cross-validate inferences, using a half-sample design, with little loss of statistical power. The first stage analysis, using the first half-sample, identified 54 SNPs in 43 genes to be significantly associated with immune response. In the second-stage, these inferences were cross-validated using the second half-sample. First-stage results of only 8 SNPs (out of 54) in 7 genes (out of 43) were cross-validated. We tested additional SNPs in these 7 genes, and found 8 more SNPs to be significantly associated. Haplotypes constructed with these SNPs in these 7 genes also showed significant association. These 7 genes are DEFB1, TLR1, IL1RL1, CTLA4, MAPK8, CD86 and IL17D. The overall picture that has emerged from this study is that (a) immune response to polysaccharide antigens is qualitatively different from that to protein antigens, and (b) polymorphisms in genes involved in polysaccharide recognition, signal transduction, inhibition of T-cell proliferation, pro-inflammatory signaling and eventual production of antimicrobial peptides are associated with antibody response to the polysaccharide vaccine for typhoid.

ELECTRONIC SUPPLEMENTARY MATERIAL

The online version of this article (doi:10.1007/s11568-010-9134-1) contains supplementary material, which is available to authorized users.

Application of pharmacogenomics to vaccines

The field of pharmacogenomics and pharmacogenetics provides a promising science base for vaccine research and development. A broad range of phenotype/genotype data combined with high-throughput genetic sequencing and bioinformatics are increasingly being integrated into this emerging field of vaccinomics. This paper discusses the hypothesis of the 'immune response gene network' and genetic (and bioinformatic) strategies to study associations between immune response gene polymorphisms and variations in humoral and cellular immune responses to prophylactic viral vaccines, such as measles-mumps-rubella, influenza, HIV, hepatitis B and smallpox. Immunogenetic studies reveal promising new vaccine targets by providing a better understanding of the mechanisms by which gene polymorphisms may influence innate and adaptive immune responses to vaccines, including vaccine failure and vaccine-associated adverse events. Additional benefits from vaccinomic studies include the development of personalized vaccines, the development of novel vaccines and the development of novel vaccine adjuvants.

Personalized vaccines: the emerging field of vaccinomics

The next 'golden age' in vaccinology will be ushered in by the new science of vaccinomics. In turn, this will inform and allow the development of personalized vaccines, based on our increasing understanding of immune response phenotype: genotype information. Rapid advances in developing such data are already occurring for hepatitis B, influenza, measles, mumps, rubella, anthrax and smallpox vaccines. In addition, newly available data suggest that some vaccine-related adverse events may also be genetically determined and, therefore, predictable. This paper reviews the basis and logic of personalized vaccines, and describes recent advances in the field.

Vaccine immunogenetics: bedside to bench to population

The immunogenetic basis for variations in immune response to vaccines in humans remains largely unknown. Many factors can contribute to the heterogeneity of vaccine-induced immune responses, including polymorphisms of immune response genes. It is important to identify those genes involved directly or indirectly in the generation of the immune response to vaccines. Our previous work with measles reveals the impact of immune response gene polymorphisms on measles vaccine-induced humoral and cellular immune responses. We demonstrate associations between genetic variations (single nucleotide polymorphisms, SNPs) in HLA class I and class II genes, cytokine, cell surface receptor, and toll-like receptor genes and variations in immune responses to measles vaccine. Such information may provide further understanding of genetic restrictions that influence the generation of protective immune responses to vaccines, and eventually the development of new vaccines.

Genetic studies of African populations: an overview on disease susceptibility and response to vaccines and therapeutics

Africa is the ultimate source of modern humans and as such harbors more genetic variation than any other continent. For this reason, studies of the patterns of genetic variation in African populations are crucial to understanding how genes affect phenotypic variation, including disease predisposition. In addition, the patterns of extant genetic variation in Africa are important for understanding how genetic variation affects infectious diseases that are a major problem in Africa, such as malaria, tuberculosis, schistosomiasis, and HIV/AIDS. Therefore, elucidating the role that genetic susceptibility to infectious diseases plays is critical to improving the health of people in Africa. It is also of note that recent and ongoing social and cultural changes in sub-Saharan Africa have increased the prevalence of non-communicable diseases that will also require genetic analyses to improve disease prevention and treatment. In this review we give special attention to many of the past and ongoing studies, emphasizing those in Sub-Saharan Africans that address the role of genetic variation in human disease.

Genetic variation in the response to vaccination

Vaccines are the most powerful means to prevent and diminish the burden of infectious disease. However, there are limitations to their use: vaccines are not yet available for all infectious diseases (including human immunodeficiency virus and respiratory syncytial virus), they sometimes lack efficacy, the response to vaccination is limited by maternal antibodies in very young infants, and the response to vaccination is variable or may even be absent in some individuals. This review focuses on genetic factors that determine the variable response to vaccination. The highly polymorphic human leukocyte antigen system, which is involved in antigen presentation, has been researched most in this aspect, and clearly affects the response to vaccination. Other, but less polymorphic pathways involved are the Toll-like receptor pathway, which is involved in antigen recognition and stimulation of the immune system, and the cytokine immunoregulatory network. The heritability, or the proportion of total variance that is due to additive genetic factors, appears to be particularly large for vaccine-induced antibody responses in young infants compared with cell-mediated responses and antibody responses in older, immunologically more mature individuals. Both antibody and cell-mediated responses are not only affected by loci within, but also strongly by loci outside the human leukocyte antigen system. Because most genes that are important in influencing immune responses to vaccination are still unknown, clearly more work is required. A better understanding of the factors that determine an effective response to vaccination may lead to the identification of specific genes and pathways as targets for the development of novel more uniformly effective vaccines.

Heterogeneity in vaccine immune response: the role of immunogenetics and the emerging field of vaccinomics

Recent advances in the fields of immunology, genetics, molecular biology, bioinformatics, and the Human Genome Project have allowed for the emergence of the field of vaccinomics. Vaccinomics encompasses the fields of immunogenetics and immunogenomics as applied to understanding the mechanisms of heterogeneity in immune responses to vaccines. In this study, we examine the role of HLA genes, cytokine genes, and cell surface receptor genes as examples of how genetic polymorphism leads to individual and population variations in immune responses to vaccines. In turn, this data, in concert with new high-throughput technology, inform the immune-response network theory to vaccine response. Such information can be used in the directed and rational development of new vaccines, and this new golden age of vaccinology has been termed "predictive vaccinology", which will predict the likelihood of a vaccine response or an adverse response to a vaccine, the number of doses needed and even whether a vaccine is likely to be of benefit (i.e., is the individual at risk for the outcome for which the vaccine is being administered?).

Subacute sclerosing panencephalitis: is there something different in the younger children?

Subacute sclerosing panencephalitis is a rare, slow viral infection caused by a defective measles virus. Although it is a rare disease, it is still important in developing countries. The onset is generally between the ages of 5-15 years. We reported the clinical and laboratory profile and nature of 9 patients under the age of 4 years with SSPE. Although it is known that a few patients with SSPE have an acute and rapidly fulminating course, in this study rate of progression was rapidly progressive in 6 patients and progressive in 3 of them on admission. Unfortunately, 4 of them were lost to follow up because of address and/or telephone number alterations. Although the number of patients in this study is not sufficient, we suggest that SSPE patients under the age of 4 years have a poor prognosis as a result of progressive or rapidly progressive course despite medical treatment.

Human leukocyte antigen polymorphisms: variable humoral immune responses to viral vaccines

Antibody formation in response to antigen stimulation remains the basis for measuring an individual's response and protection for most viral vaccines. A significant proportion of the variation in individual humoral immune response to vaccination appears to be genetic. The collection of genes found on chromosome 6 forming the human leukocyte antigen system provides one of the greatest sources of genetic variation in individuals with respect to their immunological responses. Recent research has demonstrated significant associations between vaccine response and human leukocyte antigen alleles. These associations not only explain why vaccine-induced humoral immune responses vary among individuals and between populations, but these variations may also hold the key to the development of future generations of vaccines.

Immunologic significance of HLA class I genes in measles virus-specific IFN-gamma and IL-4 cytokine immune responses

The variability of immune responses modulated by human leukocyte antigen (HLA) genes and secreted cytokines is a significant factor in the development of a protective effect of measles vaccine. We studied the association between type 1 helper T cells (Th1)- and Th2-like cytokine immune responses and HLA class I alleles among 339 schoolchildren who previously received two doses of the measles vaccine. Median values for measles-specific interferon gamma (IFN-gamma) and interleukin-4 (IL-4) cytokines were 40.7 pg/ml [interquartile range (IQR) 8.1-176.7] and 9.7 pg/ml (IQR 2.8-24.3), respectively. Class I HLA-A (*0101 and *3101) and HLA-Cw (*0303 and *0501) alleles were significantly associated with measles-virus-induced IFN-gamma secretion. HLA-A*3101 and Cw*0303 were associated with a higher median IFN-gamma response, while A*0101 and Cw*0501 were associated with lower measles-specific IFN-gamma response. We found limited associations between HLA class I gene polymorphisms and Th2-like (IL-4) immune responses after measles vaccination, indicating that HLA class I molecules may have a limited effect on measles-vaccine-induced IL-4 secretion. Understanding the genetic factors that influence variations in cytokine secretion following measles vaccination will provide insight into the factors that influence both cell-mediated and humoral immunity to measles.

Correlates of lymphoproliferative responses to measles, mumps, and rubella (MMR) virus vaccines following MMR-II vaccination in healthy children

Cell-mediated immunity (CMI) to measles, mumps, and rubella viral antigens plays a critical role in providing long-term protection against these infectious diseases. We examined CMI by measuring lymphoproliferative response induced in response to stimulation with the above three antigens following two doses of measles, mumps, and rubella-II (MMR-II) vaccine in a randomly selected, population-based cohort of healthy children. We determined if a correlative and predictive intraclass relationship exists between CMI to the three components of MMR-II. We detected positive lymphoproliferative responses to measles, mumps, and rubella vaccines. Mumps vaccine used as an antigen had the highest median stimulation index followed by measles and rubella vaccines. The overall intraclass correlation value for lymphoproliferative response to measles, mumps, and rubella using Pearson's correlation was 0.61 (95% confidence interval = 0.56, 0.66). We observed a significant pairwise association to individual vaccine components between subjects in the upper and lower 10th percentile of immune response. This study demonstrates recall CMI post-MMR-II vaccination with significant intraclass correlation among the CMI responses to the three vaccine components.

The contribution of HLA class I antigens in immune status following two doses of rubella vaccination

The variability of humoral and cellular immune responses modulated by human leukocyte antigen (HLA) genes is a significant factor in the protective effect of rubella vaccines. We performed HLA class I typing in a group of 346 healthy schoolchildren and young adults who previously received two doses of measles-mumps-rubella-II vaccine. Rubella virus-specific humoral (serum antibody) immunity and cell-mediated immunity (lymphocyte proliferation) were assessed. Median values for antibody levels and stimulation indices (SI) were 38.63 IU/ml and 2.29 IU/ml, respectively. The alleles that provided suggestive, but not conclusive, evidence of HLA association with rubella seropositivity were HLA-B*2705 (median, 24.68 IU/ml; p = 0.160), B*4501 (median, 61.22 IU/ml; p = 0.098), Cw*0303 (median, 30.34 IU/ml; p = 0.102) and Cw*0704 (median, 26.58 IU/ml; p = 0.144). These alleles approach, but do not achieve, statistical significance. Of all the alleles analyzed, HLA-B*3503 (median SI, 3.00; p = 0.031) and HLA-Cw*1502 (median SI, 3.19; p = 0.035) were positively associated with lymphoproliferative responses to rubella virus antigens, whereas the HLA-B*3901 (SI, 1.34; p = 0.066) allele was negatively associated. This suggests that class I HLA alleles may have limited associations with humoral and cellular immune responses to rubella vaccine. These data may facilitate our understanding of immune response variation in a genetically outbred heterogeneous population.

Identification of HLA-DRB1-bound self-peptides following measles virus infection

We developed a B-lymphocyte cell line derived from a measles seropositive individual who was homozygous for the HLA-DRB1*0301 allele. Peptides associated with the HLA-DRB1*0301 protein were purified from this lymphoblastoid cell line after infection with the Attenuvax measles vaccine virus (Merck Research Laboratories, West Point, PA) and with "sham" infection. More than 40 peptide sequences were obtained by nano-scale reversed phase-high performance liquid chromatography coupled to tandem mass spectrometry (nano-LC/MS/MS). These peptides originated from 21 different source proteins--the majority from membrane-bound proteins. Most of the peptides (>73%) bound to HLA-DRB1*0301 appeared to be in lower abundance on measles-infected cells compared to the "sham-infected" cells. However, 26% of the identified peptides seem to have increased expression after measles infection. Measles vaccine virus infection did not change the level of HLA-DR expression. We demonstrate the power of nano-LC/MS/MS in the rapid determination of changes in the spectrum and expression of HLA-DRB1*0301-bound peptides after infection with measles virus. This provides further knowledge of the changes in peptide expression after viral infection and provides a powerful tool for identifying HLA-presented host and viral epitopes in the context of class II HLA molecules.

Genetic regulation of immune responses to vaccines in early life

Infant immunization is the most cost-effective strategy to prevent infectious diseases in childhood, but is limited by immaturity of the immune system. To define strategies to improve vaccine immunogenicity in early life, the role of genetic and environmental factors in the control of vaccine responses in infant twins was studied. Immune responses to BCG, polio, hepatitis B, diphtheria, pertussis and tetanus vaccines were measured at 5 months of age in 207 Gambian twin pairs recruited at birth. Intrapair correlations for monozygous and dizygous pairs were compared to estimate the environmental and genetic components of variation in responses. High heritability was observed for antibody (Ab) responses to hepatitis B (77%), oral polio (60%), tetanus (44%) and diphtheria (49%) vaccines. Significant heritability was also observed for interferon-gamma and interleukin-13 responses to tetanus, pertussis and some BCG vaccine antigens (39-65%). Non-HLA genes played a dominant role in responses to Ab-inducing vaccines, whereas responses to BCG were predominantly controlled by genes within the HLA class II locus. Genetic factors, particularly non-HLA genes, significantly modulate immune responses to infant vaccination. The identification of the specific genes involved will provide new targets for the development of vaccines and adjuvants for young infants that work independently of HLA.

Associations between human leukocyte antigen (HLA) alleles and very high levels of measles antibody following vaccination

Associations between human leukocyte antigen (HLA) genes and very high levels of antibodies (or hyperseroresponsiveness) to measles antigens in a genetically heterogeneous human population are poorly understood. We studied the association between antibody levels after measles vaccination and HLA class I and II alleles among 170 US schoolchildren who received one dose of measles-mumps-rubella II vaccine. Vaccine recipients were divided into two groups: 93 recipients who were seropositive and 77 recipients who were hyperseropositive (the upper 10th percentile of antibody levels of all subjects). Out of all the alleles analyzed, HLA-B(*)7 (odds ratio (OR) 1.9; P = 0.05), DQA1(*)0104 (OR 4.6; P = 0.02) and DPA1(*)0202 (OR 4.8; P = 0.04) alleles were positively associated with hyperseropositivity, whereas HLA-B(*)44 (OR 0.4; P = 0.02), DRB1(*)01 (OR 0.6; P = 0.09), DRB1(*)08 (OR 0.3; P = 0.04), DQB1(*)0301 (OR 0.5; P = 0.04), and DPB1(*)0401 (OR 0.6; P = 0.03) alleles were negatively associated with hyperseropositivity. The alleles B(*)44, DRB1(*)01, DRB1(*)08 and DQA1(*)0104 remained statistically significant after accounting for the effects of other alleles. The results suggest that HLA alleles have important associations with measles antibody hyperseropositivity. These data increase our understanding of measles vaccine-induced immune response and will be useful for future mechanistic work on measles virus antigen processing and presentation in seronegative and hyperseropositive individuals.

Differential HLA gene expression in measles vaccine seropositive and seronegative subjects: a pilot study

This is the first study using GeneChip technology to elucidate genetic determinants of the measles vaccine response. A comparative gene expression study was conducted using Affymetrix's Human GeneChip U-95A in 5 human subjects immunized with a 'booster' dose of measles vaccine (Attenuax, Merck) to determine whether serologically distinct subjects exhibit differential expression of human leukocyte antigen (HLA) genes. Healthy individuals aged 15-25 y, previously immunized with 2 doses of measles-mumps-rubella-II (MMR-II) vaccine, were classified as measles vaccine immunoglobulin G-specific antibody seronegatives (n = 2) and seropositives (n = 3). Changes in expression of HLA genes in seronegatives and seropositives were studied on days 7 and 14 post-measles vaccination using Microarray Suite 5.0 (MAS 5.0). There was increased expression of the HLA class I-B (p = 0.0002), HLA class II cluster of DMA, DMB, TAP1, TAP2 (p = 0.0007) and HLA-DR (p = 0.0001) genes, and decreased expression of HLA class I MICB molecule (p = 1), HLA class I-A (p = 0.9999) and major histocompatibility complex class III HSP 70 (p = 0.9999) genes on day 7 or day 14 postvaccination in seropositives compared with seronegatives. These results suggest an association between antibody response and differential HLA gene activation and may explain one potential mechanism underlying measles vaccine non-response.

Frequencies of TAP1 and TAP2 gene polymorphisms in the Anatolian population

Anatolia has a long and complex record of immigration from various regions. Here, we have used TAP1 and TAP2 gene polymorphisms as genetic markers to study the relationship between the Anatolian population and other populations. A neighbour-joining tree was constructed indicating the relatedness of European populations and the Anatolian population with respect to TAP1 and TAP2 allele frequencies.

Identification of an association between HLA class II alleles and low antibody levels after measles immunization

This is the first large cohort study to report a genetic association between humoral antibody level after measles vaccine and the HLA class II genes. The WHO goal to eradicate measles world-wide magnifies the importance of data relating to the influence of immunogenetics on measles vaccine-induced antibody responses. We present here the analysis of 242 individuals who received one dose of measles-mumps-rubella-II (MMR-II) vaccine at the age of 15 months and were genotyped for HLA class II alleles. These subjects fit into one of three categories; 72 were classified as seronegative, 93 were seropositive and 77 were serohyperpositive. HLA-DRB1*03 (odds ratio (OR), 2.22) and HLA-DPA1*0201 (OR, 1.71) were significantly associated with measles vaccine seronegativity, while additional alleles provided suggestive evidence of association with seronegativity: DQA1*0201, DQB1*0201, and DQA1*0501. The alleles DRB1*03 and DQA1*0201 remained statistically significant after accounting for the effects of other alleles. These findings are crucial in designing both measles eradication by the use of vaccine, and future vaccines to be used in genetically heterozygous populations.

Global survey of genetic variation in CCR5, RANTES, and MIP-1alpha: impact on the epidemiology of the HIV-1 pandemic

Expression of CC chemokine receptor 5 (CCR5), the major coreceptor for HIV-1 cell entry, and its ligands (e.g., RANTES and MIP-1alpha) is widely regarded as central to the pathogenesis of HIV-1 infection. By surveying nearly 3,000 HIV+ and HIV- individuals from worldwide populations for polymorphisms in the genes encoding RANTES, MIP-1alpha, and CCR5, we show that the evolutionary histories of human populations have had a significant impact on the distribution of variation in these genes, and that this may be responsible, in part, for the heterogeneous nature of the epidemiology of the HIV-1 pandemic. The varied distribution of RANTES haplotypes (AC, GC, and AG) associated with population-specific HIV-1 transmission- and disease-modifying effects is a striking example. Homozygosity for the AC haplotype was associated with an increased risk of acquiring HIV-1 as well as accelerated disease progression in European Americans, but not in African Americans. Yet, the prevalence of the ancestral AC haplotype is high in individuals of African origin, but substantially lower in non-Africans. In a Japanese cohort, AG-containing RANTES haplotype pairs were associated with a delay in disease progression; however, we now show that their contribution to HIV-1 pathogenesis and epidemiology in other parts of the world is negligible because the AG haplotype is infrequent in non-Far East Asians. Thus, the varied distribution of RANTES, MIP-1alpha, and CCR5 haplotype pairs and their population-specific phenotypic effects on HIV-1 susceptibility and disease progression results in a complex pattern of biological determinants of HIV-1 epidemiology. These findings have important implications for the design, assessment, and implementation of effective HIV-1 intervention and prevention strategies.

The burden of pneumococcal disease: the role of conjugate vaccines

The pneumococcus remains a major cause of morbidity and mortality in both underdeveloped and developed countries. Although there are licensed, safe vaccines against invasive pneumococcal disease currently available in the US and Europe, several major dilemmas are apparent. First, the efficacy of these vaccines in high risk immunocompetent adults is only moderate, with limited or no immunogenicity in very high risk, immunocompromised adults. Secondly, efficacy of the vaccine against pneumococcal pneumonia in adults is controversial. Thirdly, the current vaccines are not efficacious in children < 2 years of age, which is problematic given the high rate of invasive disease among this age group. The solution to these dilemmas may lie in the development of protein conjugate-polysaccharide vaccines. This paper briefly reviews the role of conjugate pneumococcal vaccines.

Immunogenetic mechanisms of antibody response to measles vaccine: the role of the HLA genes

Measles is the most transmissible human disease known to date. In the prevaccine era, virtually every member of each birth cohort was infected with this virus, leading to substantial morbidity and mortality, with millions of deaths on a global scale. At the current time, measles causes an estimated 1 to 1.5 million deaths per year world-wide. Since the advent of live, attenuated measles vaccines measles has been controlled, but not eradicated. Central to the goal of measles eradication are data relating to the influence of immunogenetics on vaccine immunogenicity. In this paper, the results of studies are reviewed executed in my laboratory examining the role of the class I and II HLA genes on the antibody response to measles vaccine.

The future of genetic epidemiology

Genetic epidemiology is a hybrid discipline whose ultimate aim is to identify and to characterize population-level factors that contribute to disease. Genetic epidemiologists often pursue this aim through the design and implementation of studies that simultaneously invoke principles in population genetics, epidemiology, molecular biology and biostatistics. However, traditional (and much contemporary) research in genetic epidemiology has barely tapped the potential that these disciplines have to work together. It is our view that future genetic epidemiology inquiry will benefit greatly from stronger integration of these disciplines and is likely to converge on themes in fields as diverse as demography, classical population and evolutionary genetics, pharmacoepidemiology, and ecology. The ultimate focus of this research will be evolution and maintenance of disease within and across populations.