Clinical uptake of antimicrobial stewardship recommendations following Nanosphere Verigene Blood Culture Gram-negative reporting

We performed a retrospective chart review of patients to determine if the Verigene Gram-negative blood culture (BC-GN) results would lead to earlier deescalation of empiric therapy for inpatients with GN bacteremia with Citrobacter spp., Enterobacter spp., Klebsiella spp., and Escherichia coli to appropriate targeted coverage. A total of 899 records were reviewed from April 2014 to February 2016 from three institutions within the Baylor Scott & White Health network. The cases were reviewed for initial antibiotic coverage, timing of Verigene results, change in antibiotic coverage, and how these changes related to the timing of Verigene results. The lab reported the BC-GN results and final conventional susceptibility results within 2.5 ± 1.3 and 73.6 ± 40.0 hours from the Gram stain, respectively. Overall, 29.1% of patients were transitioned from empiric to targeted therapy at 12.2 ± 13.5 hours in response to BC-GN results, which was significantly earlier (P < 0.001) than results by conventional methods. After accounting for patients already on targeted therapy, polymicrobial infections, and patients deceased or lost to follow-up, we identified antibiotic stewardship opportunities in ∼28% of GN infections. Further subanalysis demonstrated site-specific differences in the uptake of stewardship recommendations, whereby 32.4%, 50.5%, and 15.0% of cases at different hospitals demonstrated the expected change in antibiotics. These results suggest that Verigene had the expected impact in a third of the cases and the results reporting algorithm minimized the real-time involvement of the pharmacist while maintaining optimal patient management. However, this impact varied substantially by clinical site and was tempered by variable initial antibiotic coverage and clinician response.

Does supplemental interphase FISH analysis to standard chromosom analysis improve the detection of myelodysplastic syndrome?

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Background: Our objective was to evaluate whether the addition of interphase FISH analysis to standard chromosome analysis (CA) improves the detection of chromosomal abnormalities in patients with work up for myelodysplastic syndromes (MDS), acute myeloid leukemia, and myelodysplastic/myeloproliferative disorders and thereby increases diagnostic and prognostic information. We performed a retrospective data review of all MDS orders between January and September 2015 at our institution and evaluated concurrent tests for discrepancies between CA and FISH results. Our aim was to evaluate best practices with regard to diagnostic test utilization, specifically to assess the diagnostic and prognostic value of FISH in addition to CA for patients with potential and known MDS. Methods: Retrospective data review of concurrent test orders of CA and myelodysplastic FISH panel were reviewed. The myelodysplastic FISH panel consists of screening for monosomy 5/deletion 5q, monosomy 7/deletion 7q, CEP7, trisomy 8, and D20S108 (20q12). The results of CA and FISH results were analyzed using a chi-square test to evaluate statistical significance. Results: A total of 1121 samples were queried, of which 55 were excluded due to inability to perform CA and limited diagnostic value of accompanying standalone FISH data on the 4 markers tested in this study. Analysis of the eligible 1066 samples showed that the standalone CA had significantly higher sensitivity (p < 0.0001) in detecting abnormal cases (N = 247, 23.17%) as compared to standalone FISH analysis (N = 180, 16.89%). Overall, 173 (16.23%) cases were determined to be abnormal by both methods. CA correctly interpreted 1059 of 1066 cases (99.34%).Only 7 samples were interpreted as normal by CA but were found to be abnormal by FISH. This results in overall 0.66% (2.76% of the abnormal cases) of abnormalities that would have been missed by CA only. Conclusions: These findings suggest that FISH studies with 4 markers used in this study provide limited additional utility in cases with a complete CA.

Myroides odoratimimus bacteremia in a diabetic patient

Myroides species are a rare source of human infection. Though not part of the human microbiota, Myroides species are commonly found in the environment. Myroides infections are typically attributed to contact with contaminated water; the most common presentation is in immunocompromised patients. We present a patient with a diabetic foot ulcer who subsequently developed Myroides odoratimimus bacteremia and bone abscess.

Antibiotic utilization improvement with the Nanosphere Verigene Gram-Positive Blood Culture assay

New technologies offer rapid identification of organisms and antimicrobial resistance markers in blood cultures several hours faster than conventional methods. We sought to determine whether implementation of the Verigene® Gram-Positive Blood Culture (BC-GP) assay paired with a well-defined results reporting algorithm would lead to earlier deescalation of empiric therapy for inpatients with methicillin-sensitive Staphylococcus aureus (MSSA) and vancomycin-resistant Enterococcus (VRE) bacteremia. The algorithm design focused on lessening the demand for pharmacist time by using electronic communications where possible. Our study compared inpatients with MSSA and VRE bacteremia from the time period before (pre-BC-GP) and after (post-BC-GP) implementation of the assay on June 25, 2013. The time from blood draw to identification and susceptibility results was decreased by 36.4 hours (P < 0.001) in the post-BC-GP group. The mean time from collection to the first dose of optimal antibiotics was reduced in the post-BC-GP group by 18.9 hours (P = 0.004) overall, with a 20.6-hour reduction (P = 0.009) for patients with MSSA and a 20.7-hour reduction (P = 0.077) for patients with VRE. Additionally, the percent of patients on empiric therapy who were placed on optimal antibiotics at any time after the Gram stain result was available increased from 64% (45/70) pre-BC-GP to 80% (43/54) post-BC-GP. The BC-GP led to an increased rate of deescalation of empiric antibiotics and a reduction in the time to optimal antibiotics for patients with MSSA and VRE bacteremia.

The SUCCESS model for laboratory performance and execution of rapid molecular diagnostics in patients with sepsis

Successful performance and execution of rapid diagnostics in a clinical laboratory hinges heavily on careful validation, accurate and timely communication of results, and real-time quality monitoring. Laboratories must develop strategies to integrate diagnostics with stewardship and evidence-based clinical practice guidelines. We present a collaborative SUCCESS model for execution and monitoring of rapid sepsis diagnostics to facilitate timely treatment. Six months after execution of the Verigene Gram-Positive Blood Culture (BC-GP) and the AdvanDx PNA-FISH assays, data were collected on 579 and 28 episodes of bacteremia and fungemia, respectively. Clinical testing was executed using a SUCCESS model comprising the following components: stewardship, utilization of resources, core strategies, concierge services, education, support, and surveillance. Stewardship needs were identified by evaluating the specialty services benefiting from new testing. Utilization of resources was optimized by reviewing current treatment strategies and antibiogram and formulary options. Core strategies consisted of input from infectious disease leadership, pharmacy, and laboratory staff. Concierge services included automated Micro-eUpdate and physician-friendly actionable reports. Education modules were user-specific, and support was provided through a dedicated 24/7 microbiology hotline. Surveillance was performed by daily audit by the director. Using the SUCCESS model, the turnaround time for the detailed report with actionable guidelines to the physician was ∼3 hours from the time of culture positivity. The overall correlation between rapid methods and culture was 94% (546/579). Discrepant results were predominantly contaminants such as a coagulase-negative staphylococci or viridans streptococci in mixed cultures. SUCCESS is a cost-effective and easily adaptable model for clinical laboratories with limited stewardship resources.

High-dimensional gene expression profiling studies in high and low responders to primary smallpox vaccination

BACKGROUND

The mechanisms underlying smallpox vaccine-induced variations in immune responses are not well understood, but are of considerable interest to a deeper understanding of poxvirus immunity and correlates of protection.

METHODS

We assessed transcriptional messenger RNA expression changes in 197 recipients of primary smallpox vaccination representing the extremes of humoral and cellular immune responses.

RESULTS

The 20 most significant differentially expressed genes include a tumor necrosis factor-receptor superfamily member, an interferon (IFN) gene, a chemokine gene, zinc finger protein genes, nuclear factors, and histones (P ≤ 1.06E(-20), q ≤ 2.64E(-17)). A pathway analysis identified 4 enriched pathways with cytokine production by the T-helper 17 subset of CD4+ T cells being the most significant pathway (P = 3.42E(-05)). Two pathways (antiviral actions of IFNs, P = 8.95E(-05); and IFN-α/β signaling pathway, P = 2.92E(-04)), integral to innate immunity, were enriched when comparing high with low antibody responders (false discovery rate, < 0.05). Genes related to immune function and transcription (TLR8, P = .0002; DAPP1, P = .0003; LAMP3, P = 9.96E(-05); NR4A2, P ≤ .0002; EGR3, P = 4.52E(-05)), and other genes with a possible impact on immunity (LNPEP, P = 3.72E(-05); CAPRIN1, P = .0001; XRN1, P = .0001), were found to be expressed differentially in high versus low antibody responders.

CONCLUSION

We identified novel and known immunity-related genes and pathways that may account for differences in immune response to smallpox vaccination.

Effectiveness of patient-collected swabs for influenza testing

OBJECTIVE

To compare the effectiveness of self-collected and health care worker (HCW)-collected nasal swabs for detection of influenza viruses and determine the patients' preference for type of collection.

PATIENTS AND METHODS

We enrolled adult patients presenting with influenzalike illness to the Emergency Department at Mayo Clinic, Rochester, Minnesota, from January 28, 2011, through April 30, 2011. Patients self-collected a midturbinate nasal flocked swab from their right nostril following written instructions. A second swab was then collected by an HCW from the left nostril. Swabs were tested for influenza A and B viruses by real-time reverse transcription-polymerase chain reaction, and percent concordance between collection methods was determined.

RESULTS

Of the 72 paired specimens analyzed, 25 were positive for influenza A or B RNA by at least one of the collection methods (34.7% positivity rate). When the 14 patients who had prior health care training were excluded, the qualitative agreement between collection methods was 94.8% (55 of 58). Two of the 58 specimens (3.4%) from patients without health care training were positive only by HCW collection, and 1 of 58 (1.7%) was positive only by patient self-collection. A total of 53.4% of patients (31 of 58) preferred the self-collection method over the HCW collection, and 25.9% (15 of 58) had no preference.

CONCLUSION

Self-collected midturbinate nasal swabs provide a reliable alternative to HCW collection for influenza A and B virus real-time reverse transcription-polymerase chain reaction.

Common SNPs/haplotypes in IL18R1 and IL18 genes are associated with variations in humoral immunity to smallpox vaccination in Caucasians and African Americans

BACKGROUND

Identifying genetic factors that influence poxvirus immunity across races may assist in the development of better vaccines and approaches for vaccine development.

METHODS

We performed an extensive candidate-gene genetic screen (across 32 cytokine and cytokine receptor genes) in a racially diverse cohort of 1056 healthy adults after a single dose of smallpox vaccine. Associations between single-nucleotide polymorphisms (SNPs)/haplotypes and vaccinia virus-specific neutralizing antibodies were assessed using linear regression methodologies.

RESULTS

The combined analysis identified 63 associations between candidate SNPs and antibody levels after smallpox vaccination with P < .05. Thirty-one of these were within the IL18R1 and IL18 genes. Five IL18R1 SNPs, including a coding synonymous polymorphism rs1035130 (Phe251Phe) and 2 promoter SNPs (rs6710885, rs2287037), all in linkage disequilibrium, were associated with significant variations in antibody levels in both Caucasians (P ≤ .016) and African Americans (P ≤ .025). Similarly, associations with 2 intronic IL18 SNPs (rs2043055 and rs5744280) were consistent in the Caucasian (P ≤ .023) and African American samples (P ≤ .014). Haplotype analysis revealed highly significant associations between IL18R1 haplotypes and vaccinia virus-specific antibody levels (P < .001, by combined analysis) that were consistent across races.

CONCLUSIONS

Our study provides evidence for IL18 and IL18R1 genes as plausible genes regulating the humoral immune response to smallpox vaccine in both Caucasians and African Americans.

SNPPicker: high quality tag SNP selection across multiple populations

Background

Linkage Disequilibrium (LD) bin-tagging algorithms identify a reduced set of tag SNPs that can capture the genetic variation in a population without genotyping every single SNP. However, existing tag SNP selection algorithms for designing custom genotyping panels do not take into account all platform dependent factors affecting the likelihood of a tag SNP to be successfully genotyped and many of the constraints that can be imposed by the user.

Results

SNPPicker optimizes the selection of tag SNPs from common bin-tagging programs to design custom genotyping panels. The application uses a multi-step search strategy in combination with a statistical model to maximize the genotyping success of the selected tag SNPs. User preference toward functional SNPs can also be taken into account as secondary criteria. SNPPicker can also optimize tag SNP selection for a panel tagging multiple populations. SNPPicker can optimize custom genotyping panels including all the assay-specific constraints of Illumina's GoldenGate and Infinium assays.

Conclusions

A new application has been developed to maximize the success of custom multi-population genotyping panels. SNPPicker also takes into account user constraints including options for controlling runtime. Perl Scripts, Java source code and executables are available under an open source license for download at http://mayoresearch.mayo.edu/mayo/research/biostat/software.cfm

Differential cellular immune responses to wild-type and attenuated edmonston tag measles virus strains are primarily defined by the viral phosphoprotein gene

The measles virus phosphoprotein (P) gene encodes the P, V, and C proteins, which have multiple functions including type I interferon (IFN) inhibition. With a focus on viral immune modulation, we conducted a study on healthy vaccinees (n=179) to compare cytokine secretion patterns/cell frequencies and gene expression after in vitro encounter with a highly attenuated strain of measles virus (MVEdmtag), wild-type MV (MVwt) or recombinant MVEdmtag expressing the wild-type P gene (MVwtP). Cytokines were quantified by ELISA and Elispot. Gene expression profiling was performed using real-time PCR. We found differential MV-specific cytokine responses to all detected cytokines characterized by significantly higher cytokine levels (P<0.001) and higher frequencies (P<0.0001) of cytokine-producing cells after stimulation with the highly attenuated MVEdmtag strain in comparison with MVwt or MVwtP. Furthermore, gene expression profiling revealed significant cytokine suppression at the transcriptional level for viruses encoding the functional wt P gene, compared to attenuated MVEdmtag (P<0.05). Using lentivirus-mediated stable expression of P gene-encoded proteins in human cell lines, we demonstrated that the expression of the functional wt V protein significantly down-modulated the induction of IFNs type I, II, and III in lymphocytes and monocytes. Taken together our results indicate that Th1, Th2, and innate/inflammatory cytokine responses in vaccinees are suppressed both at the protein and transcriptional level by viruses expressing the functional wt P gene products. The functional P gene-encoded viral proteins (particularly V proteins) emerge as crucial immune evasion factors for modulating and shaping the measles virus-specific cytokine responses in humans.

Optimizing high dimensional gene expression studies for immune response following smallpox vaccination using Taqman® low density immune arrays

INTRODUCTION

We sought to determine the time and vaccinia virus dose combination that would maximize the number of acute immune response changes in response to vaccinia stimulation in preparation for a large gene expression microarray experiment.

METHODS

PBMCs from ten subjects were exposed to five vaccinia virus doses for three lengths of time. Gene expression was measured for 90 immune response genes via Taqman® Low Density Immune Arrays. Expression data were normalized via model-based non-linear normalization. Linear mixed effects model results were used to standardize changes across genes and determine the time/multiplicity of infection (MOI) combination with the largest number of changes.

RESULTS

The greatest number of changes occurred with a MOI of 5.0 and exposure time of 48 h. Further inspection revealed that most changes had occurred earlier and faded at this combination. The second highest number of changes was found at a MOI of 0.5 PFU/cell and time of 18 h.

CONCLUSIONS

We conclude a time of 18 h with a MOI of 0.5 PFU/cell is the optimal time/MOI combination for the full scale gene expression study. The strategy described herein is a general and resource efficient way to make critical decisions regarding experimental parameters for studies utilizing expensive assays that interrogate a large number of variables.

Detection of IgG-class antibodies to measles, mumps, rubella, and varicella-zoster virus using a multiplex bead immunoassay

Serologic testing for measles, mumps, rubella, and varicella (MMRV) IgG is traditionally performed by immunofluorescence assay or enzyme immunoassay (EIA). Although sensitive and specific, these methods are labor intensive, time consuming, and require separate assays for each analyte. This study evaluated the performance of the MMRV IgG AtheNA Multi-Lyte assay using nonclinically characterized serum specimens submitted to our laboratory for routine MMRV IgG testing. Mumps (n = 492) or rubella (n = 500) IgG were initially tested by enzyme-linked fluorescent antibody (ELFA), whereas measles (n = 494) or varicella (n = 497) were analyzed by EIA. Each sample was also tested by the AtheNA Multi-Lyte assay. Discordant results were retested by the predicate method and the multiplex assay, with further discrepancies being arbitrated by a third test. Compared to EIA/ELFA for MMRV IgG, the AtheNA assay demonstrated an overall agreement of 97.4%, 98.2%, 97.6%, and 100%, respectively. Use of this multiplex assay allows for the simultaneous detection of MMRV IgG, potentially decreasing cost, sample volume requirements, aliquot errors, and hands-on testing time.

SNP/haplotype associations in cytokine and cytokine receptor genes and immunity to rubella vaccine

An effective immune response to vaccination is, in part, a complex interaction of alleles of multiple genes regulating cytokine networks. We conducted a genotyping study of Th1/Th2/inflammatory cytokines/cytokine receptors in healthy children (n = 738, 11-19 years) to determine associations between individual single-nucleotide polymorphisms (SNPs)/haplotypes and immune outcomes after two doses of rubella vaccine. SNPs (n = 501) were selected using the ldSelect-approach and genotyped using Illumina GoldenGate and TaqMan assays. Rubella-IgG levels were measured by immunoassay and secreted cytokines by ELISA. Linear regression and post hoc haplotype analyses were used to determine associations between single SNPs/haplotypes and immune outcomes. Increased carriage of minor alleles for the promoter SNPs (rs2844482 and rs2857708) of the TNFA gene were associated with dose-related increases in rubella antibodies. IL-6 secretion was co-directionally associated (p < or = 0.01) with five intronic SNPs in the TNFRSF1B gene in an allele dose-related manner, while five promoter/intronic SNPs in the IL12B gene were associated with variations in IL-6 secretion. TNFA haplotype AAACGGGGC (t-statistic = 3.32) and IL12B promoter haplotype TAG (t-statistic = 2.66) were associated with higher levels of (p < or = 0.01) rubella-IgG and IL-6 secretion, respectively. We identified individual SNPs/haplotypes in TNFA/TNFRSF1B and IL12B genes that appear to modulate immunity to rubella vaccination. Identification of such "genetic fingerprints" may predict the outcome of vaccine response and inform new vaccine strategies.

Predominant inflammatory cytokine secretion pattern in response to two doses of live rubella vaccine in healthy vaccinees

We conducted a population-based study on 738 schoolchildren who received two doses of rubella vaccine in order to determine cytokine secretion patterns and their associations with demographic and clinical variables. The results showed a robust rubella-specific inflammatory cytokine response characterized by high median [inter-quartile range (IQR)] secretion levels (in pg/mL) of IL-6 [3681.0 (3160.0, 4052.0)], GM-CSF [28.0 (23.6, 32.6)], and TNF-alpha [29.7 (-7.0, 89.2)]. We also detected modest levels of rubella-specific secretion of Th1 cytokines IL-2 and IFN-gamma, while IL-12p40 was undetectable. In contrast, rubella-specific Th2 responses were hardly detectable. Age at vaccination, enrollment, and time elapsed between last vaccination and enrollment was significantly associated with the outcome of IL-2, IL-6, and IFN-gamma secretion. These results suggest an immune-deviation or "skewing" from Th1/Th2 cytokine patterns towards a predominant inflammatory response upon in vitro rubella virus stimulation.

Rubella vaccine-induced cellular immunity: evidence of associations with polymorphisms in the Toll-like, vitamin A and D receptors, and innate immune response genes

Toll-like, vitamin A and D receptors and other innate proteins participate in various immune functions. We determined whether innate gene-sequence variations are associated with rubella vaccine-induced cytokine immune responses. We genotyped 714 healthy children (11-19 years of age) after two doses of rubella-containing vaccine for 148 candidate SNP markers. Rubella virus-induced cytokines were measured by ELISA. Twenty-two significant associations (range of P values 0.002-0.048) were found between SNPs in the vitamin A receptor family (RARA, RARB, TOP2B and RARG), vitamin D receptor and downstream mediator of vitamin D signaling (RXRA) genes and rubella virus-specific (IFN-gamma, IL-2, IL-10, TNF-alpha, and GM-CSF) cytokine immune responses. A TLR3 gene promoter region SNP (rs5743305, -8441A > T) was associated with rubella-specific GM-CSF secretion. Importantly, SNPs in the TRIM5 gene coding regions, rs3740996 (His43Tyr) and rs10838525 (Gln136Arg), were associated with an allele dose-related secretion of rubella virus-specific TNF-alpha and IL-2/GM-CSF, respectively, and have been previously shown to have functional consequences regarding the antiviral activity and susceptibility to HIV-1 infection. We identified associations between individual SNPs and haplotypes in, or involving, the RIG-I (DDX58) gene and rubella-specific TNF-alpha secretion. This is the first paper to present evidence that polymorphisms in the TLR, vitamin A, vitamin D receptor, and innate immunity genes can influence adaptive cytokine responses to rubella vaccination.

2'-5'-Oligoadenylate synthetase single-nucleotide polymorphisms and haplotypes are associated with variations in immune responses to rubella vaccine

Interferon-induced antiviral genes are crucial players in innate antiviral defense and potential determinants of immune response heterogeneity. We selected 114 candidate single-nucleotide polymorphisms (SNPs) from 12 antiviral genes using an LD tagSNP selection approach and genotyped them in a cohort of 738 school children immunized with two doses of rubella vaccine. Associations between SNPs/haplotypes and rubella virus-specific immune measures were assessed using linear regression methodologies. We identified 23 significant associations (p < 0.05) between polymorphisms within the 2'-5'-oligoadenylate synthetase (OAS) gene cluster, and rubella virus-specific IL-2, IL-10, IL-6 secretion, and antibody levels. The minor allele variants of three OAS1 SNPs (rs3741981/Ser162Gly, rs1051042/Thr361Arg, rs2660), located in a linkage disequilibrium block of functional importance, were significantly associated with an increase in rubella virus-specific IL-2/T(h)1 response (p <or = 0.024). Seven OAS1 and OAS3 promoter/regulatory SNPs were similarly associated with IL-2 secretion. Importantly, two SNPs (rs3741981 and rs10774670) independently cross-regulated rubella virus-specific IL-10 secretion levels (p < or = 0.031). Furthermore, both global tests and individual haplotype analyses revealed significant associations between OAS1 haplotypes and rubella virus-specific cytokine secretion. Our results suggest that innate immunity and OAS genetic variations are likely involved in modulating the magnitude and quality of the adaptive immune responses to live attenuated rubella vaccine.

Polymorphisms in the vitamin A receptor and innate immunity genes influence the antibody response to rubella vaccination

BACKGROUND

Genetic polymorphisms play an important role in rubella vaccine-induced immunity.

METHODS

We genotyped 714 healthy children after 2 age-appropriate doses of rubella-containing vaccine for 142 potential single-nucleotide polymorphisms (SNPs).

RESULTS

Specific polymorphisms in the vitamin A receptor, retinoic acid-inducible gene I (RIG-I), and tripartite motif 5 and 22 (TRIM5 and TRIM22) genes were significantly associated with rubella vaccine humoral immunity. The minor allele of the rs4416353 in the vitamin A receptor gene was associated with an allele dose-related decrease (P = .019) in rubella antibody response. The minor allele of rs6793694, in the vitamin A receptor gene, was associated with an allele dose-related antibody decrease (p = .039). The minor variant of nonsynonymous SNP rs10813831 (Arg7Cys) in the RIG-I gene was associated with an allele dose-related decrease in rubella antibody level from 37.4 to 28.0 IU/mL (P = .035), whereas increased representation of the minor allele of the 5'UTR SNP (rs3824949, P = .015) in the antiretroviral TRIM5 gene was associated with an allele dose-related increase in rubella antibody. It is of particular interest that the nonsynonymous SNP rs3740996 (His43Tyr) in the TRIM5 gene was associated with variations in rubella antibody response (P = .016) after having been previously found to play a significant functional role.

CONCLUSIONS

These findings further expand our immunogenetic understanding of mechanisms of rubella vaccine-induced immunity.

Response surface methodology to determine optimal cytokine responses in human peripheral blood mononuclear cells after smallpox vaccination

Feasibility, amount of sample aliquots, processing time and cost are critical considerations for optimizing and conducting assays for large-population based studies. Well designed statistical approaches that quickly identify optimal conditions for a given assay could assist efficient completion of the laboratory assays for such studies. For example, assessment of the profile of secreted cytokines is important in understanding the immune response after vaccination. To characterize the cytokine immune response following smallpox vaccination, PBMC obtained from recently vaccinated subjects were stimulated with varying doses of live or UV-inactivated vaccinia virus and cultured for up to 8 days. In this paper, we describe a novel statistical method to identify optimal operating conditions for length in culture and virus MOI in order to measure a panel of secreted Th1, Th2, and inflammatory cytokines. This statistical method is comprised of two components. It first identifies a subset of the possible time in culture by virus MOI combinations to be studied. It then utilizes response surface analysis techniques to predict the optimal operating conditions for the measurement of each secreted cytokine. This method was applied, and the predicted optimal combinations of length in culture and virus MOI for maximum vaccinia-specific cytokine secretion were identified. The use of the response surface methodology can be applied to the optimization of other laboratory assays; especially when the number of PBMC available limits the testing of all possible combinations of parameters.

Associations between cytokine/cytokine receptor single nucleotide polymorphisms and humoral immunity to measles, mumps and rubella in a Somali population

We genotyped a Somali population (n = 85; age < or =30 years) for 617 cytokine and cytokine receptor single nucleotide polymorphisms (SNPs) using Illumina GoldenGate genotyping to determine associations with measles, mumps and rubella immunity. Overall, 61 significant associations (P < or = 0.01) were found between SNPs belonging to cytokine receptor genes regulating T helper (Th)1 (IL12RB2, IL2RA and B) and Th2 (IL4R and IL10RB) immunity, and cytokine (IL1B, TNFA, IL6 and IFNB1) and cytokine receptor (IL1RA, IFNAR2, IL18R1, TNFRSF1A and B) genes regulating innate immunity and variations in antibody levels to measles, mumps and/or rubella. SNPs within two major inflammatory cytokine genes, TNFA and interleukin (IL) 6, showed associations with measles-specific antibodies. Specifically, the minor allele variant of rs1799964 (TNFA -1211 C>T) was associated with primarily seronegative values (median enzyme immunoassay index values < or =0.87; P = 0.002; q = 0.23) in response to measles disease and/or vaccination. A heterozygous variant CT for rs2069849 (IL6 +4272C>T; Phe201Phe) was also associated with seronegative values and a lower median level of antibody response to measles disease and/or vaccination (P = 0.004; q = 0.36) or measles vaccination alone (P = 0.008). Several SNPs within the coding and regulatory regions of cytokine and cytokine receptor genes showed associations with mumps and rubella antibody levels but were less informative as strong linkage disequilibrium patterns and lower frequencies for minor alleles were observed among these SNPs. Our study identifies specific SNPs in innate immune response genes that may play a role in modulating antibody responses to measles vaccination and/or infection in Somali subjects.

Human leukocyte antigen and cytokine receptor gene polymorphisms associated with heterogeneous immune responses to mumps viral vaccine

OBJECTIVES

Mumps outbreaks continue to occur throughout the world, including in highly vaccinated populations. Vaccination against mumps has been successful; however, humoral and cellular immune responses to mumps vaccines vary significantly from person to person. We set out to assess whether HLA and cytokine gene polymorphisms are associated with variations in the immune response to mumps viral vaccine.

METHODS

To identify genetic factors that might contribute to variations in mumps vaccine-induced immune responses, we performed HLA genotyping in a group of 346 healthy schoolchildren (12-18 years of age) who previously received 2 doses of live mumps vaccine. Single-nucleotide polymorphisms (minor allele frequency of >5%) in cytokine and cytokine receptor genes were genotyped for a subset of 118 children.

RESULTS

Median values for mumps-specific antibody titers and lymphoproliferative stimulation indices were 729 IU/mL and 4.8, respectively. Girls demonstrated significantly higher mumps antibody titers than boys, indicating gender-linked genetic differences in humoral immune response. Significant associations were found between the HLA-DQB1*0303 alleles and lower mumps-specific antibody titers. An interesting finding was the association of several HLA class II alleles with mumps-specific lymphoproliferation. Alleles of the DRB1 (*0101, *0301, *0801, *1001, *1201, and *1302), DQA1 (*0101, *0105, *0401, and *0501), and DQB1 (*0201, *0402, and *0501) loci were associated with significant variations in lymphoproliferative immune responses to mumps vaccine. Additional associations were observed with single-nucleotide polymorphisms in the interleukin-10RA, interleukin-12RB1, and interleukin-12RB2 cytokine receptor genes. Minor alleles for 4 single-nucleotide polymorphisms within interleukin-10RA and interleukin-12RB genes were associated with variations in humoral and cellular immune responses to mumps vaccination.

CONCLUSIONS

These data suggest the important role of HLA and immunoregulatory cytokine receptor gene polymorphisms in explaining variations in mumps vaccine-induced immune responses.

Associations between SNPs in toll-like receptors and related intracellular signaling molecules and immune responses to measles vaccine: preliminary results

Toll-like receptors (TLRs) represent the critical "bridge" between innate and adaptive immunity to viral pathogens. We hypothesized that single nucleotide polymorphisms (SNPs) that potentially influence the expression/function of TLRs and their associated intracellular signaling molecules contribute to variations in humoral and cellular immunity to measles vaccine. We genotyped 190 randomly selected subjects (12-18 years old), previously vaccinated with two doses of measles, for known SNPs in TLR 2, 3, 4, 5, 6, 7, 8 and 9, and their associated intracellular signaling genes. Specific SNPs in the TLR 2, 3, 4, 5, 6, MyD88 and MD2 genes were associated with measles-specific humoral and cellular immunity. Heterozygous variants for rs3775291 (Phe412Leu) and rs5743305 (-926 bp in promoter region) of the TLR3 gene were associated with low antibody and lymphoproliferative responses (p <or= 0.02) to measles vaccination. Heterozygous variants for rs4986790 (Gly299Asp) and rs4986791 (Ile399Thr) in the TLR4 gene demonstrated higher levels of (p <or= 0.02) IL-4 secretion. Heterozygous variants for SNPs in TLR5 (rs5744174) and TLR6 (rs5743818) were associated with higher levels of (p <or= 0.02) IFN-gamma secretion. In addition, SNPs in MyD88 and MD2, intracellular molecules that associate with TLRs, also demonstrated associations with variations in antibody and IL-10 production (p <or= 0.03). Thus, we identified specific SNP associations between TLRs and their associated signaling molecules that have a known role in viral immunity and variations in both humoral and cellular immunity following measles vaccination. These data contribute to understanding the immunogenetic mechanisms underlying variations in the immune response to measles vaccine.

Variations in measles vaccine–specific humoral immunity by polymorphisms in SLAM and CD46 measles virus receptors

BACKGROUND

Measles infection requires 2 cellular receptors, signaling lymphocyte activation molecule (SLAM) and CD46. Known and novel single nucleotide polymorphisms (SNPs) in SLAM and CD46 genes might influence the immune response to measles vaccine.

OBJECTIVE

We sought to identify SNP associations in SLAM and CD46 genes with variations in measles antibody response.

METHODS

We genotyped known SNPs in SLAM and CD46 genes in 339 subjects vaccinated with 2 doses of measles-mumps-rubella vaccine. We also sequenced the measles virus-binding domains of SLAM and CD46 to identify novel SNPs.

RESULTS

Increased representation of minor alleles for rs3796504 and rs164288 in the SLAM gene was associated with an allele dose-related decrease (4-fold) in measles-specific antibodies. Heterozygous genotype TC for rs12076998 located in the untranslated region 33 bp upstream of the measles virus-binding domain of the SLAM gene was associated with higher median antibody levels (1991 vs 1467 IU/L, P = .01) compared with wild-type TT. Within the CD46 gene, the minor allele C for intronic SNP (rs11118580) was associated with an allele dose-related decrease in measles antibodies (1072 vs 1795 IU/L, P < .01). Decreases in minor allele counts for rs3796504, rs164288, and rs1118580 demonstrated a significant (P < .001) additive effect on measles-specific antibodies.

CONCLUSION

Our data suggest that specific SNPs present in both the SLAM and CD46 genes are associated with measurable and significant variations in antibody response after measles vaccination.

CLINICAL IMPLICATIONS

Understanding the immunogenetics of measles vaccine receptors is important to better understand variations in immune responses to vaccines and to design better vaccines.

Assessing participation bias in a population-based study of measles-mumps-rubella vaccine immunity in children and adolescents aged 12-18

The purpose of our study was to determine whether specific characteristics were associated with study participation in a group of children residing in Olmsted County, MN. We compared 346 participants and 848 non-participants from a study examining associations between human leukocyte antigen gene variants and immunity following measles-mumps-rubella (MMR) vaccination by demographic characteristics, MMR vaccination history and length of time in the Olmsted County health care system. We also compared the frequency and reasons for health care visits between participants and non-participants by comparing diagnostic codes for all visits that had occurred between 1999 and 2001. Characteristics were compared using chi-square and t-tests, followed by multivariable logistic regression. Study participants were more likely to be white/Caucasian, to have received their first MMR vaccination at a younger age, and to have had more health care visits (especially for acute respiratory illnesses, vaccinations, or other acute conditions such as fainting and headaches) than study non-participants. These results suggest that frequent use of local health care systems by children and parents may increase comfort levels with local physicians and physician researchers, thereby improving participation rates in research studies among these populations. However, special efforts may be necessary to improve research participation among children who are infrequent users of the health care systems of interest.

Relationship between HLA polymorphisms and gamma interferon and interleukin-10 cytokine production in healthy individuals after rubella vaccination

We studied the association between HLA alleles and rubella-specific gamma interferon (IFN-gamma) (Th1) and interleukin-10 (IL-10) (Th2) cytokine responses among 106 healthy children (ages, 14 to 17 years) previously immunized with two doses of rubella vaccine. Antibody titers and cytokine responses to rubella vaccination were not sex or age dependent. Several class I HLA-A (*0201, *2402, *6801) alleles were significantly associated with rubella vaccine-induced IFN-gamma secretion. Several class II HLA-DRB1 (*0101) and HLA-DQB1 (*0501) alleles were also suggestive of an association with IFN-gamma secretion. Alleles with potential associations with rubella-specific IL-10 production included HLA-A (*0201, *6801), HLA-B (*4901), and HLA-DRB1 (*1302). The class I A*0201 and A*6801 alleles were associated with both IFN-gamma and IL-10 secretion. These tentative associations need to be validated in larger studies with subjects of differing ethnicities. These results provide additional evidence that HLA genes may influence Th1- and Th2-specific cytokine response(s) following rubella immunization, which in turn can influence both cellular and humoral immune responses to rubella vaccination.

Associations between Measles Vaccine Immunity and Single‐Nucleotide Polymorphisms in Cytokine and Cytokine Receptor Genes

BACKGROUND

Cytokines are key regulators of measles vaccine humoral and cellular immunity. Single-nucleotide polymorphisms (SNPs) that are associated with differences in cytokine levels should also influence measles vaccine-induced immunity.

METHODS

We genotyped 118 measles-mumps-rubella-vaccinated subjects for SNPs from 6 cytokine genes (interleukin [IL]-2, IL-4, IL-10, IL-12A, IL-12B, and interferon [IFN]-gamma) and their receptors (IL-2RA, IL-2RB, IL-4RA, IL-10RA, IL-10RB, IL-12RB1, IL-12RB2, and IFN-gamma R). Associations of SNPs with measles-specific antibodies, lymphoproliferation, and secreted cytokines were determined using chi2 tests and analyses of covariance.

RESULTS

We found significant associations (P<.05) between SNPs in the IL-2, IL-10, and IL-12RB genes and measles vaccine-induced immunity. The IVS1-100G (rs2069762) and the Ex2-34G (rs2069763) SNPs within the IL-2 gene were associated with high antibody and high lymphoproliferative responses, whereas SNPs within the IL-10 and IL-12R genes were associated with low antibody and lymphoproliferative responses to measles. SNPs within the IL-4RA and IL-12B genes varied significantly (P<.05) across immune response measures. Significant associations were also found between SNPs and secreted cytokine levels.

CONCLUSIONS

Specific SNPs in the cytokine and cytokine receptor genes are significantly associated with variations in measures of the immune response to measles vaccination. These results need to be further validated in a larger cohort.

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.

Inter-operator variation in ELISPOT analysis of measles virus-specific IFN-gamma-secreting T cells

The ELISPOT assay is a highly sensitive technique used for the detection of individual cytokine releasing cells. We have developed an IFN-gamma ELISPOT assay utilizing unfractionated frozen peripheral blood mononuclear cells (PBMC) to quantify the frequency of measles virus (MV)-specific IFN-gamma-secreting T cells in 117 healthy children who had been previously immunized with two doses of the measles-mumps-rubella vaccine. We have also estimated the variability associated with the quantification of ELISPOT plates and compared the number of MV-specific IFN-gamma-secreting T cells for each subject as determined by two different operators of an ELISPOT reader. The median frequency of MV-specific IFN-gamma-producing memory T cells detected by this assay was 0.005 % and 0.01 % as determined by an in-house and commercial operator, respectively. Although we found a significant correlation (r = 0.83, p<0.0001) between the number of spots counted by the commercial and in-house operators of an ELISPOT reader, the median number of spots counted by the commercial operator was twice the number of spots counted by an in-house operator (p<0.001). This demonstrates the importance of using a common ELISPOT reader and operator, among other parameters, to quantify the number of spots when a large volume of plates are being scanned and analyzed.

Correlations among measles virus-specific antibody, lymphoproliferation and Th1/Th2 cytokine responses following measles-mumps-rubella-II (MMR-II) vaccination

Immunity to measles is conferred by the interplay of humoral and cellular immune responses, the latter being critical in maintaining long-term recall response. Therefore, it is important to evaluate measles-specific humoral and cellular immunity in populations several years after vaccination and understand the correlations among these measures of immunity. We examined measles-specific antibodies, lymphoproliferation and the Th1/Th2 signature cytokines, interferon (IFN)-gamma and interleukin (IL)-4, in a population-based cohort of healthy children from Olmsted County, Minnesota after two doses of measles-mumps-rubella-II (MMR-II) vaccine. We detected positive measures of measles-specific cellular and humoral immunity in the majority of our study population. However, a small proportion of subjects demonstrated an immune response skewed towards the Th2 type, characterized by the presence of either IL-4 and/or measles-specific antibodies and a lack of IFN-gamma production. Further, we observed a significant positive correlation between lymphoproliferation and secretion of IFN-gamma (r = 0.20, P = 0.0002) and IL-4 (r = 0.15, P = 0.005). Measles antibody levels were correlated with lymphoproliferation (r = 0.12, P = 0.03), but lacked correlation to either cytokine type. In conclusion, we demonstrated the presence of both long-term cellular and humoral responses after MMR-II vaccination in a significant proportion of study subjects. Further, a positive correlation between lymphoproliferation and IL-4 and IFN-gamma suggests that immunity to measles may be maintained by both Th1 and Th2 cells. We speculate that the Th2 biased response observed in a subset of our subjects may be insufficient to provide long-term immunity against measles. Further examination of the determinants of Th1 versus Th2 skewing of the immune response and long-term follow-up is needed.

Immune activation at effector and gene expression levels after measles vaccination in healthy individuals: a pilot study

Cellular immunity to measles vaccination is not fully understood at the effector response and gene expression levels. We enrolled 15 healthy individuals (15-25 years old) previously vaccinated with two doses of measles-mumps-rubella-II vaccine to characterize their cellular immunity. We detected a spectrum of lymphoproliferative response (median stimulation indices of 3.4), low precursor frequencies of interferon-gamma (median 0.11%) and interleukin-4 (median 0.05%) by Elispot, and cosecretion of Th1 and Th2 cytokines after measles virus stimulation. Further, global gene expression was examined in five subjects from this cohort after vaccination with an additional dose of measles vaccine (Attenuax, Merck) to identify the genes involved in measles immunity. Linear mixed effect models were used to identify genes significantly up or downregulated in vivo between baseline and Days 7 and 14 after measles vaccination. Measles vaccination induced upregulation of a set of 80 genes, which play a role in measles immunity, signal transduction, apoptosis, cell proliferation, and metabolic pathways. Among the 34 genes that were downregulated, only interferon-alpha is known to have a direct role in measles immunity. This study suggests that measles vaccination leads to activation of multiple cellular mechanisms that can override the immunosuppressant effects of the measles virus and induce immunity.

Extinction of the human leukocyte antigen homozygosity effect after two doses of the measles-mumps-rubella vaccine

We have reported associations between human leukocyte antigen (HLA) homozygosity and low measles antibody levels after one dose of the measles, mumps, and rubella (MMR) vaccine. Here, we examined associations between HLA homozygosity and immune responses to MMR after two doses of vaccine. We examined associations between HLA homozygosity and measles antibody levels in a group of 178 children (cohort 1) as well as associations between homozygosity and antibody levels and lymphoproliferative responses to MMR in 346 children (cohort 2). In cohort 1, HLA homozygotes and heterozygotes had similar increases in measles antibody levels after a second dose of measles vaccine. In cohort 2, HLA homozygosity was not associated with measles immune measures after two doses of vaccine. Homozygosity at the DPB locus was associated with increased rubella antibody levels, and homozygosity at the class IA alleles was associated with lower mumps lymphoproliferative response. Homozygosity at increasing numbers of loci was also associated with lower mumps antibody levels and lymphoproliferative response. Therefore, two doses of the MMR vaccine appear to induce sufficient antibody levels and lymphoproliferative responses against measles and rubella, regardless of HLA homozygosity status. However, children who are HLA homozygous may be less protected against mumps compared with children who are heterozygous.

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.

Induction of CD4 T cell proliferation and in vitro Th1-like cytokine responses to measles virus

Mechanisms that lead to induction of life-long immunity to measles virus (MV) are poorly understood. In the present study, we have assessed the activation, proliferation and cytokine secreting function of peripheral blood T cells from MV immune individuals. Expression of cell blastogenesis markers, such as increased forward light scatter and CD38 expression, peaked 5-7 days after infection of peripheral blood mononuclear cells (PBMC) with the live attenuated Edmonston strain of MV. Subset analysis revealed that both CD3- and CD3+ cells expressed activation markers but that the CD3+ T cells predominated late in the culture period corresponding to maximal proliferation and cell recovery. The majority of CD3+ T cells consisted of CD4+CD8- cells. IFN-gamma and IL-4 production similarly showed optimal production late in culture. Depletion of CD4 cells prior to culture and MV stimulation completely abrogated both IFN-gamma and IL-4 production, whereas depletion of CD8 cells did not diminish production, suggesting that CD4+CD8- T cells were principally involved in production of these cytokines. Finally, optimal IFN-gamma production was elicited at high MV doses and IL-4 at much lower doses. These results suggest that among MV immune individuals, in vitro responses to measles are dominated by CD4+ T cells that, depending on antigen dose, primarily produce a Th1-like and, to a lesser extent, a Th1/Th2-mixed pattern of cytokine release.

Measles virus receptors: SLAM and CD46

The success of vaccination against measles in developed countries has significantly reduced the incidence of measles-related morbidity and mortality. However, measles is still the leading cause of mortality in children from underdeveloped countries due to low vaccination coverage, high transmissibility of the measles virus as well as primary and secondary vaccine failure. As with any viral disease, the identification of the host molecule to which the measles virus binds and gains entry into the host cell is a major step in understanding the molecular pathology of the disease. Two cell surface receptors, CD46 and signaling lymphocyte-activation molecule (SLAM), have been identified as measles virus receptors. CD46 is ubiquitously expressed on all nucleated cells and acts as a receptor for the Edmonston strain and all vaccine strains derived from it. SLAM is selectively expressed on some T and B cells and is utilised by the Edmonston strain and wild-type strains that cannot use CD46 for cell entry. Understanding the structural and functional variations in measles virus receptors with regard to host response can facilitate the development of new vaccines as well as provide new insights into measles virus tropism and pathogenesis and, importantly, into possible mechanisms for vaccine non-response. Our review focuses on the structure of measles virus receptors, measles virus receptor function, isoforms and polymorphic forms.

Interleukin-4 induced by measles virus and measles-derived peptides as measured by IL-4 receptor-blocking ELISA

Interleukin-4 (IL-4) is a signature cytokine for T-helper 2 (Th2) type immune responses in humans. However, data on antigen-specific secretion of IL-4 is limited due to difficulties detecting IL-4. We evaluated an IL-4 receptor-blocking assay for the detection of secreted IL-4 in peripheral blood mononuclear cells (PBMC) stimulated in vitro with measles virus (MV) and MV-derived nucleoprotein (N) and phosphoprotein (P) peptides. We recruited 20 healthy subjects, previously immunized with two doses of measles-mumps-rubella-II (MMR-II) vaccine. We evaluated the cellular and humoral immune status of these study subjects by an in vitro lymphoproliferation assay and an enzyme-linked immunosorbent assay (ELISA), respectively. We analyzed the MV-induced and N and P peptide-induced IL-4 levels in PBMC culture supernatants. Using the IL-4 receptor blocking assay, 50% of the subjects were positive for secreted IL-4 in response to MV stimulation, and 5% and 23.1% of study subjects were positive for secreted IL-4 in response to MV-derived N and P peptides, respectively. In contrast, we did not find any positive secreted IL-4 response to MV using conventional ELISA without IL-4 receptor-blocking antibody in our optimization study. Further, we found very low frequencies of IL-4 secreting cells using an alternate ELISpot technique, accounting for only a 5% positive response to MV and no response to P peptide. We propose that the IL-4 receptor-blocking assay is an easy-to-adapt technique for screening antigen-specific immune responses in large-scale population-based studies.

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.

Lack of association between transporter associated with antigen processing (TAP) and HLA-DM gene polymorphisms and antibody levels following measles vaccination

The transporter associated with antigen processing (TAP) and human leukocyte antigen-DM (HLA-DM) genes are involved in the antigen-processing pathway of both HLA class I and class II-restricted antigen presentation. We hypothesized that polymorphisms within the TAP and DM genes may influence antibody levels following measles vaccination. We examined TAP and DM polymorphisms in 242 school children from Olmsted County, Minnesota, USA who received one dose of measles-mumps-rubella-II (MMR-II) vaccine at the age of 15 months. Based on the level of serum measles-specific immunoglobulin G (IgG) antibodies, subjects were classified as seronegatives (n = 72) or seropositives (n = 170). We determined TAP1 and TAP2 allele types by polymerase chain reaction (PCR) amplification of specific alleles (PASA) and determined DM allele type by PCR amplification followed by direct sequencing of the polymorphic sites. We analysed the data for any TAP or DM allelic association with antibody levels post measles vaccination using the chi-square test and univariate linear regression analysis. We found no trend in the overall distribution of TAP and DM genotype frequencies between seronegative and seropositive subjects, suggesting that TAP and DM polymorphism and antibody levels following measles vaccination are not directly associated. In addition, we did not find an association between TAP (TAP1, P = 0.71; TAP2, P = 0.87) or DM (DMA, P = 0.42; DMB, P = 0.71) homozygosity and seronegativity to measles vaccine in this study group. Our study suggests that TAP and DM gene polymorphisms do not influence antibody levels post measles vaccination.

Frequency of measles virus-specific CD4+ and CD8+ T cells in subjects seronegative or highly seropositive for measles vaccine

The protective effect of measles immunization is due to humoral and cell-mediated immune responses. Little is known about cell-mediated immunity (CMI) to measles vaccine virus, the relative contribution of CD4(+) and CD8(+) T cells to variability in such immune responses, and the immunologic longevity of the CMI after measles vaccination in humans. Our study characterizes cellular immune response in subjects seronegative or highly seropositive for measles vaccine immunoglobulin G-specific antibody, aged 15 to 25 years, previously immunized with two doses of measles-mumps-rubella II vaccine. We evaluated the ability of subjects to respond to measles vaccine virus by measuring measles virus-specific T-cell proliferation. We examined the frequencies of measles virus-specific memory Th1 and Th2 cells by an ELISPOT assay. Our results demonstrated that proliferation of T cells in seronegative subjects was significantly lower than that for highly seropositive subjects (P = 0.003). Gamma interferon (IFN-gamma) secretion predominated over interleukin 4 (IL-4) secretion in response to measles virus in both groups. The median frequency of measles virus-reactive CD8(+) T cells secreting IFN-gamma was 0.09% in seronegative subjects and 0.43% in highly seropositive subjects (P = 0.04). The median frequency of CD4(+) T cells secreting IL-4 in response to measles virus was 0.03% in seronegative subjects and 0.09% in highly seropositive subjects (P = 0.005). These data confirm the presence of measles virus-specific cellular immune responses post-measles vaccine immunization in humans. The detection of measles virus-induced IFN-gamma and IL-4 production by ELISPOT can be used to identify measles virus-specific low-frequency memory T cells in subjects immunized with measles vaccine. These differences agree in directionality with the observed antibody response phenotype.

Gene expression microarrays: a 21st century tool for directed vaccine design

DNA microarray technology is a new and powerful tool that allows the simultaneous analysis of a large number of nucleic acid hybridization experiments in a rapid and efficient fashion. The development of the DNA microarray chip has been driven by modern techniques of microelectronic fabrication, miniaturization and integration to produce what is referred to as "laboratory-on-chip" devices. The application of DNA chip technology includes the comprehensive analysis of multiple gene mutations and expressed sequences with regard to newer drug designs, host-pathogen interactions and the design of new vaccines. An advantage of microarray technology is that it can assist researchers to better define and understand the expression profile of a given genotype associated with disease, adverse effects from exposure to certain stimuli, or the ability to understand or predict immune responses to specific antigens. This paper briefly reviews DNA microarray technology and its implications with special reference to vaccine design. The technical aspects comprising array manufacturing and design, array hybridization, formatting, scanning and data handling are also briefly discussed.

Secreted products of a nonmucoid Pseudomonas aeruginosa strain induce two modes of macrophage killing: external-ATP-dependent, P2Z-receptor-mediated necrosis and ATP-independent, caspase-mediated apoptosis

A nonmucoid clinical isolate of Pseudomonas aeruginosa, strain 808, elaborated ATP-dependent and ATP-independent types of cytotoxic factors in the growth medium. These cytotoxic factors, active against macrophages, were secreted during the exponential phase of growth in a complex medium. Commensurate with the appearance of the cytotoxic activities in the cell-free growth medium, several ATP-utilizing enzymic activities, such as adenylate kinase, nucleoside diphosphate kinase and 5'-nucleotidase (ATPase and/or phosphatase), were detected in the medium. These ATP-utilizing enzymes are believed to convert external ATP, presumably effluxed from macrophages, to various adenine nucleotides, which then activate purinergic receptors such as P2Z, leading to enhanced macrophage cell death. Pretreatment of macrophages with periodate-oxidized ATP (oATP), which is an irreversible inhibitor of P2Z receptor activation, prevented subsequent ATP-induced macrophage cell death. A second type of cytotoxic factor(s) operated in an ATP-independent manner such that it triggered activation of apoptotic processes in macrophages, leading to proteolytic conversion of procaspase-3 to active caspase-3. This cytotoxic factor(s) did not appear to act on procaspase-3 present in macrophage cytosolic extracts. Intact macrophages, when exposed to the cytotoxic factor(s) for 6-16 h, underwent apoptosis and demonstrated the presence of active caspase-3 in their cytosolic extracts. Interestingly, two redox proteins, azurin and cytochrome c(551), were detected in the cytotoxic preparation. When cell-line-derived or peritoneal macrophages or mast cells were incubated overnight with Q-Sepharose column flow-through fraction or with a mixture of azurin and cytochrome c(551), they underwent extensive cell death due to induction of apoptosis.

Phagocytic cell killing mediated by secreted cytotoxic factors of Vibrio cholerae

Vibrio cholerae strain VB1 secretes a number of enzymes into the outside medium that utilize ATP as a substrate. Such enzymes are found in the outside medium during the mid-log phase of growth, when the optical density at 650 nm is about 0.4, and they demonstrate nucleoside diphosphate kinase (Ndk), 5' nucleotidase, and adenylate kinase (Ak) activities. We report that the filtered growth medium of V. cholerae, as well as the flowthrough fraction of a green Sepharose column during fractionation of the growth medium, had very little cytotoxicity by itself towards macrophages and mast cells but exhibited significant cytotoxicity in the presence of exogenous ATP. Such fractions, harboring 5' nucleotidase, Ndk, and presumably other ATP-utilizing enzymes, demonstrated enhanced macrophage and mast cell death; periodate-oxidized-ATP (oATP)-treated macrophage and mast cells or such cells exposed to 0.1 mM Mg(2+), where surface-associated P2Z receptors could not be activated, were not susceptible to subsequent ATP addition. Microscopic visualization of mast cells clearly demonstrated cell morphological changes such as swelling, vacuolization, and nuclear fragmentation following treatment with ATP and the growth medium of V. cholerae; however, these effects were suppressed if the mast cells were pretreated with oATP. These results strongly imply that the secreted ATP-utilizing enzymes of V. cholerae modulate the external ATP levels of the macrophage and mast cells, leading to their accelerated death, presumably through activation of P2Z receptors. Thus, development of inhibitors for such enzymes may reduce the level of V. cholerae infection; alternatively, mutations in such genes may eliminate V. cholerae survival in the gut and contribute to a safer live vaccine.

Poly (DL-lactide-co-glycolide) based delivery systems for vaccines and drugs

Current vaccination and drug delivery strategies emphasize on the development of controlled release techniques for persistent and sustained effects. In the recent years, polymer based systems for the delivery of bioactive agents have gained considerable attention due to their marked adjuvanticity, established biodegradability and biocompatibility, excellent mechanical strength and controlled release profiles. This review deals with the potential applications of synthetic polymers mainly PLG polymers in delivery of vaccines and drugs.

Clinical and environmental isolates of Burkholderia cepacia exhibit differential cytotoxicity towards macrophages and mast cells

Burkholderia cepacia is an emerging opportunistic pathogen that causes fatal infections in patients suffering from cystic fibrosis (CF) and chronic granulomatous disease. Various environmental isolates of B. cepacia are, however, capable of degrading environmental pollutants, such as trichloroethylene, 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), etc., and are also highly effective in controlling plant diseases caused by nematodes and fungi. Such strains have therefore been proposed for environmental release to clean up toxic dump sites or as biopesticides. Various efforts to distinguish between clinical and environmental isolates of B. cepacia with regard to their virulence characteristics have produced ambiguous results, suggesting that newer methods are needed to test for the presence or absence of pathogenic potential in B. cepacia strains proposed for environmental release. We now report that several clinical strains of B. cepacia secrete cytotoxic factors that allow macrophage and mast cell death in the presence of external ATP. Several environmental strains had reduced activity in this regard. We also demonstrate that, while all the strains secrete enzymes that have nucleoside diphosphate kinase (Ndk), adenylate kinase (Ak) and 5'-nucleotidase activity, the level of secretion of the 5'-nucleotidase (and/or ATPase/phosphatase) appears to be lower in the environmental strains than in the clinical strains. The secretion of these enzymes is specifically activated in the presence of eukaryotic proteins such as alpha2-macroglobulin. As macrophage-or mast cell surface-associated P2Z receptors promote their cell death in the presence of mM concentrations of ATP, and as the secreted ATP-using enzymes generate various phosphorylated or non-phosphorylated adenine nucleotides that may even be better agonists than ATP in activating the P2Z receptors or may act through the activation of additional purinergic receptors, such enzymes may play an important role in allowing B. cepacia to evade host defence.

Immunoreactivity of peptides generated by limited proteolysis of 71-kDa cell wall protein of Mycobacterium tuberculosis H37Ra using PLG-microparticles

Peptide mapping by limited proteolysis of a highly protective 71-kDa cell wall-associated protein of Mycobacterium tuberculosis H37Ra was carried out in order to identify key protective determinants within the native protein. The 71-kDa protein, which had an isoelectric point of 4.25, was digested into eight major bands at 48 h using trypsin and pepsin at equal enzyme to protein ratios (pH 5.5). The in vitro lymphocyte reactivity of individual peptides suggested P1, P2 and P5 to be significantly immunoreactive in mice immunized with native 71-kDa-polylactide-coglyeolide (PLG); however, the reactivity was significantly lower than that of the native 71-kDa protein. Immunization of mice with a pooled fraction (upper fraction-71 kDa) of more immunoreactive peptides (consisting of P1 and P2) did not further boost their immunoreactivity. However, P1 and P2 exhibited comparable or even higher lymphocyte proliferation in human tuberculous and control subjects. These data suggest distinct antigenic specificities in humans and mice and further substantiate the use of the 71-kDa protein or its peptides P1 and P2 as potential vaccine candidates for tuberculosis.

Mycobacterial proteins--immune targets for antituberculous subunit vaccine

Cellular and humoral immunity induced by Mycobacterium tuberculosis has led to identification of newer vaccine candidates, but despite this, many questions concerning the protection against tuberculosis remain unanswered. Recent progress in this field has centered on T cell subset responses and cytokines that these cells secrete. There has been a steady progress in identification and characterization of several classes of major mycobacterial proteins which includes secretory/export proteins, cell wall associated proteins, heat shock proteins and cytoplasmic proteins. The protein antigens are now believed to represent the key protective immunity inducing antigens in the bacillus. In this review, various mycobacterial protein antigens of vaccination potential are compared for their efficacy in light of current immunological knowledge.

Mechanism and specificity of immunoprotection induced by mycobacterial proteins against experimental tuberculosis in mice

Mechanism of immunoprotection and specificity of two highly immunoprotective mycobacterial proteins, viz. 71 and 30 kDa were investigated. The adoptive transfer studies indicated that immunoprotection was mainly mediated by cooperative effect of CD4+ and CD8+ (66.7-73.3% on the basis of percent survival) which was further enhanced marginally by supplementation of B cells, natural killer cells, dendritic cells, macrophages and other immune cells. The specificity studies indicated that both the proteins did not cross react with the unrelated intracellular pathogens i.e. Aspergillus fumigatus, Salmonella typhi and Leishmania donovani as seen by T cell proliferation assay. The protection imparted by these mycobacterial proteins was also specific as the 71 and 30 kDa primed mice did not exhibit any cross protection against sublethal challenge of S typhi. The results indicate 71 and 30 kDa mycobacterial proteins to contain T cell specific epitopes responsible for specific immunoprotection, thus indicating their potential role as antituberculous vaccine candidates.

Protective efficacy of mycobacterial 71-kDa cell wall associated protein using poly (DL-lactide-co-glycolide) microparticles as carrier vehicles

Microparticles composed of poly (DL-lactide-co-glycolide) (DL-PLG) were used as delivery vehicles for evaluating the immunoreactive and immunoprotective properties of 71-kDa cell wall associated protein of Mycobacterium tuberculosis H37Ra. Mice immunized with 71-kDa microparticles entrapped in DL-PLG (PLG-MPs) exhibited significantly higher T-cell stimulation and cytokine release in comparison to 71-kDa emulsified in Freund's incomplete adjuvant (FIA) as well as a BCG vaccinated group throughout the post-immunization (p.im.) period. Further, the protective efficacy of 71-kDa was evaluated on the basis of survival rates and viable bacilli load in different organs at 30 days post challenge (p.c.), with the median lethal dose (LD50) of M. tuberculosis H37Rv at weeks 8 and 16 p.im. Both 71-kDa-PLG and 71-kDa-FIA immunized groups exhibited a comparable protection (90%) which was significantly higher (P < 0.5) than in the BCG group (70%) at week 8 p.im. and it was consistent with the decreased bacterial load in the target organs. However, on increasing the interval of challenge to 16 weeks p.im., the protective efficacy of 71-kDa-PLG was sustained (85%) while that of 71-kDa-FIA began to wane (70%). Further. the 71-kDa-PLG immunized group exhibited a significantly higher (P < 0.001) clearance of bacterial load from the lungs and livers in comparison to the 71-kDa-FIA immunized group. The results suggest the long-term protective potential of a PLG-microparticle based antigen delivery system for tuberculosis.