Multiplex assay for detection of strain-specific antibodies against the two variable regions of the G protein of respiratory syncytial virus

Bead-Based Multiplex Assay for the Simultaneous Detection of Antibodies to African Swine Fever Virus and Classical Swine Fever Virus

African swine fever (ASF) and Classical swine fever (CSF) are both highly contagious diseases of domestic pigs and wild boar. In the last years, several cases of both diseases have been reported in the Caucasus, Russian Federation and Eastern Europe. Thus, the probability of encountering these two viruses in the same area is increasing. Since differentiation by clinical or post-mortem examination is not possible, laboratory tools for differential diagnosis are required. In the present work, we have developed a triplex bead-based assay using some of the most immunogenic antigens of each virus, for the simultaneous detection of antibodies; i.e. the VP72 and VP30 of ASF virus (ASFV) and the E2 protein of CSF virus (CSFV). The assay was firstly set up and optimized using well characterized reference serum samples specific for each pathogen. Then, a panel of 352 sera from experimentally infected animals with either ASFV or CSFV were analyzed in the multiplex assay. A collection of 253 field negative sera was also included in the study. The results of the multiplex analysis were compared to those obtained by two commercially available ELISAs for detection of antibodies against ASFV or CSFV, and considered in this study as the reference techniques. The data obtained showed values of 97.3% sensitivity and 98.3% specificity for detection of antibodies to ASFV and 95.7% of sensitivity and 99.8% specificity for detection of antibodies to CSFV. This multiplex assay allows the simultaneous and differential detection of antibodies against ASFV and CSFV, providing a valuable tool for surveillance studies. Moreover, this method is rather versatile, offering the possibility of increasing the panel of antigens from other swine diseases that could be of interest for a differential diagnosis along with ASF and CSF.

Analysis of liquid bead microarray antibody assay data for epidemiologic studies of pathogen-cancer associations

BACKGROUND

Liquid bead microarray antibody (LBMA) assays are used to assess pathogen-cancer associations. However, studies analyze LBMA data differently, limiting comparability.

METHODS

We generated 10,000 Monte Carlo-type simulations of log-normal antibody distributions (exposure) with 200 cases and 200 controls (outcome). We estimated type I error rates, statistical power, and bias associated with t-tests, logistic regression with a linear exposure and with the exposure dichotomized at 200 units, 400 units, the mean among controls plus two standard deviations, and the value corresponding to the optimal sensitivity and specificity. We also applied these models, and data visualizations (kernel density plots, receiver operating characteristic (ROC) curves, predicted probability plots, and Q-Q plots), to two empirical datasets to assess the consistency of the exposure-outcome relationship.

RESULTS

All strategies had acceptable type I error rates (0.03 ≤ P ≤ 0.048), except for the dichotomization according to optimal sensitivity and specificity, which had a type I error rate of 0.27. Among the remaining methods, logistic regression with a linear predictor (Power=1.00) and t-tests (Power=1.00) had the highest power to detect a mean difference of 1.0 MFI (median fluorescence intensity) on the log scale and were unbiased. Dichotomization methods upwardly biased the risk estimates.

CONCLUSION

These results indicate that logistic regression with linear predictors and unpaired t-tests are superior to logistic regression with dichotomized predictors for assessing disease associations with LBMA data. Logistic regression with continuous linear predictors and t-tests are preferable to commonly used LBMA dichotomization methods.

Epidemiological changes of respiratory syncytial virus (RSV) infections in Israel

RSV is the leading cause of lower respiratory-tract infections in infants and therefore demands in-depth epidemiological characterization. We investigated here the distribution of RSV types in Israel between the years 2005–2012. Clinical samples were collected from 11,018 patients hospitalized due to respiratory illnesses and were evaluated for the presence of various respiratory viruses, including RSV A and RSV B. Until 2008, each year was characterized by the presence of one dominant type of RSV. However, from 2008, both RSV A and B types were detected at significant levels, particularly among infants aged 0–2 years. Furthermore, significant changes in the RSV A and RSV B subtypes circulating in Israel since 2008 were observed. Finally, we demonstrate that, irrespectively of the changes observed in RSV epidemiology, when the pandemic H1N1pdm09 influenza virus appeared in 2009, RSV infections were delayed and were detected when infection with H1N1pdm09 had declined.

Naturally occurring IgG antibody levels to the Staphylococcus aureus protein IsdB in humans

Staphylococcus aureus is a well-recognized, clinically important cause of nosocomial infections, and as such, a vaccine to prevent S. aureus infections would be an important achievement. A Phase IIB/III study of V710, a vaccine containing iron-regulated surface determinant B (IsdB), demonstrated significant sero-conversion rates in cardiovascular surgery patients following a single pre-surgery immunization. However, the vaccine was not efficacious in preventing bacteremia or deep sternal wound infection post-surgery, thus raising the possibility that IsdB might not be available for immune recognition during infection. The purpose of the work described herein was to evaluate and quantify the naturally occurring anti-IsdB levels at baseline and over time during infection, to understand whether IsdB is expressed during a S. aureus infection in hospitalized non-vaccinated patients. We evaluated baseline and follow-up titers in 3 populations: (1) healthy subjects, (2) hospitalized patients with non-S. aureus infections, and (3) hospitalized patients with S. aureus infections. Baseline anti-IsdB levels generally overlapped between the 3 groups, but were highly variable within each group. In healthy subjects, baseline and follow-up levels were highly correlated (Spearman's rho = 0.93), and the geometric mean fold-rise (GMFR) in anti-IsdB levels between study entry and last value was 0.9-fold (95% confidence interval (CI): 0.8 to 1.0 ; p = 0.09), showing no trend over time. The convalescent GMFR in anti-IsdB levels from baseline was 1.7-fold (95% CI: 1.3 to 2.2, p = 0.0008) during S. aureus infection, significantly different from the 1.0-fold GMFR (95% CI: 0.9-1.2, p = 0.60) in non-S. aureus infection, p = 0.005. Additionally, S. aureus isolates (51) obtained from the hospitalized patient group expressed the IsdB protein in vitro. Collectively, these data suggest that IsdB expression levels rise substantially following infection with S. aureus, but not with other pathogens, and IsdB is likely well-conserved across S. aureus strains.

Influence of respiratory syncytial virus strain differences on pathogenesis and immunity

Molecular epidemiology studies have provided convincing evidence of antigenic and sequence variability among respiratory syncytial virus (RSV) isolates. Circulating viruses have been classified into two antigenic groups (A and B) that correlate with well-delineated genetic groups. Most sequence and antigenic differences (both inter- and intra-groups) accumulate in two hypervariable segments of the G-protein gene. Sequences of the G gene have been used for phylogenetic analyses. These studies have shown a worldwide distribution of RSV strains with both local and global replacement of dominant viruses with time. Although data are still limited, there is evidence that strain variation may contribute to differences in pathogenicity. In addition, there is some but limited evidence that RSV variation may be, at least partially, immune (antibody) driven. However, there is the paradox in RSV that, in contrast to other viruses (e.g., influenza viruses) the epitopes recognized by the most effective RSV-neutralizing antibodies are highly conserved. In contrast, antibodies that recognize strain-specific epitopes are poorly neutralizing. It is likely that this apparent contradiction is due to the lack of a comprehensive knowledge of the duration and specificities of the human antibody response against RSV antigens. Since there are some data supporting a group- (or clade-) specific antibody response after a primary infection in humans, it may be wise to consider the incorporation of strains representative of groups A and B (or their antigens) in future RSV vaccine development.

Effect of serum heat-inactivation and dilution on detection of anti-WNV antibodies in mice by West Nile virus E-protein microsphere immunoassay

Immunopathogenesis studies employing West Nile virus (WNV) mice model are important for the development of antivirals and vaccines against WNV. Since antibodies produced in mice early during WNV infection are essential for clearing virus from the periphery, it is important to detect early and persistent anti-WNV antibodies. ELISA and plaque reduction neutralization tests are traditionally used for detection of anti-WNV antibodies and WNV-neutralizing antibodies, respectively. Although these assays are sensitive and specific, they are expensive and time consuming. Microsphere immunoassays (MIA) are sensitive, specific, allow for high throughput, are cost effective, require less time to perform than other methods, and require low serum volumes. Several assay parameters such as serum heat-inactivation (HI) and dilution can alter WNV MIA sensitivity. We examined the effect of these parameters on WNV E-protein MIA (WNV E-MIA) for the enhanced detection of anti-WNV IgM and IgG antibodies. WNV E-MIA was conducted using serial dilutions of HI and non-HI (NHI) serum collected at various time points from mice inoculated with WNV. HI significantly enhanced detection of IgM and IgG antibodies as compared to NHI serum. WNV IgM and IgG antibodies in HI sera were detected earlier at day 3 and IgM antibodies persisted up to day 24 after infection. HI serum at 1∶20 dilution was found to be optimal for detection of both IgM and IgG antibodies as compared to higher-serum dilutions. Further, addition of exogenous complement to the HI serum decreased the WNV E-MIA sensitivity. These results suggest that serum-HI and optimal dilution enhance WNV E-MIA sensitivity by eliminating the complement interference, thereby detecting low-titer anti-WNV antibodies during early and late phases of infection. This improved MIA can also be readily employed for detection of low-titer antibodies for detection of other infectious agents and host proteins.

Antibody response to the central unglycosylated region of the respiratory syncytial virus attachment protein in mice

We examined the humoral immune response to the unglycosylated central region of the respiratory syncytial virus (RSV) attachment (G) protein in mice following intranasal challenge at day 0 (primary) and day 21 (secondary) with subtype A (A2 strain) or B (B1 strain) RSV preparations. Our serological screening reagents included bacterially derived glutathione S-transferase (GST) fusion proteins, each bearing a portion of the RSV G central core (CC; residues 151-190), proximal central core (PCC; residues 151-172), and the distal central core (DCC; residues 173-190) and purified RSV G proteins from subtype A and B viruses. Convalescent sera collected on day 21 following primary RSV infection bore robust IgG response primarily against the homosubtypic RSV G DCC with relatively modest antigen affinity/avidity as demonstrated by brief incubation with 6M urea. In contrast, sera collected on day 42 following secondary homosubtypic RSV infection bore IgG titers of higher magnitudes and antigen affinity/avidity against the homosubtypic RSV G CC, PCC, and/or the DCC regions and full-length RSV G protein but not against the heterosubtypic RSV G protein or recombinant CC subdomains. In contrast, heterosubtypic secondary RSV infection elicits a broad array of IgG responses with titers of varying magnitudes to homo- and heterosubtypic RSV G CC regions as well as to purified F, Ga, and Gb proteins with the notable exception of minimal response to the RSV G DCC domain associated with the secondary RSV challenge. Our results have implications for RSV G-based serological assays as well as prophylactic immunotherapy and RSV vaccine development.

Fast, antigen-saving multiplex immunoassay to determine levels and avidity of mouse serum antibodies to pertussis, diphtheria, and tetanus antigens

To enhance preclinical evaluation of serological immune responses to the individual diphtheria, tetanus, and pertussis (DTP) components of DTP combination vaccines, a fast hexavalent bead-based method was developed. This multiplex immunoassay (MIA) can simultaneously determine levels of specific mouse serum IgG antibodies to P antigens P.69 pertactin (P.69 Prn), filamentous hemagglutinin (FHA), pertussis toxin (Ptx), and combined fimbria type 2 and 3 antigens (Fim2/3) and to diphtheria toxin (Dtx) and tetanus toxin (TT) in a single well. The mouse DTP MIA was shown to be specific and sensitive and to correlate with the six single in-house enzyme-linked immunosorbent assays (ELISAs) for all antigens. Moreover, the MIA was expanded to include avidity measurements of DTP antigens in a multivalent manner. The sensitivities of the mouse DTP avidity MIA per antigen were comparable to those of the six individual in-house avidity ELISAs, and good correlations between IgG concentrations obtained by both methods for all antigens tested were shown. The regular and avidity mouse DTP MIAs were reproducible, with good intra- and interassay coefficients of variability (CV) for all antigens. Finally, the usefulness of the assay was demonstrated in a longitudinal study of the development and avidity maturation of specific IgG antibodies in mice having received different DTP vaccines. We conclude that the hexaplex mouse DTP MIA is a specific, sensitive, and high-throughput alternative for ELISA to investigate the quantity and quality of serological responses to DTP antigens in preclinical vaccine studies.

Usage of cancer associated autoantibodies in the detection of disease

Efforts toward deciphering the complexity of the tumor specific proteome by profiling immune responses generated against tumor associated antigens (TAAs) holds great promise for predicting the presence of cancer long before the development of clinical symptoms. The immune system is capable of sensing aberrant expression of certain cellular components involved in tumorigenesis and the resultant autoantibody response provides insights to the targets that are responsible for eliciting immunogenicity to these cellular components. Analysis of the cancer-specific humoral immune response has led to panels of biomarkers that are specific and sensitive biomarkers of disease. Using multianalyte-based in vitro analytical discovery platforms which can be easily adapted into clinical diagnostic screening tests, body fluids such as serum, plasma saliva, or urine can be interrogated to detect autoantibodies against natural or recombinant antigens, which may possess etiologic significance to cancer. Non-invasive screening tests exhibiting high specificity and sensitivity to detect early stage cancer in the heterogeneous population of cancer patients potentially have the greatest impact in decreasing mortality rates. Overall, this review summarizes different experimental approaches in the development of diagnostic screening tests for the early detection of cancer and their implementation in the development of clinical multianalyte biomarker assays.

Humoral response to the central unglycosylated region of the respiratory syncytial virus attachment protein

To characterize the humoral response to the unglycosylated central region of the respiratory syncytial virus (RSV) attachment (G) protein, we generated glutathione S-transferase (GST)-RSV G subdomains (central core (CC), residues 151-190; proximal central core (PCC), 151-172; and distal central core (DCC), 173-190) to screen paired sera from RSV subtype A- or B-infected adults in hospitalized or outpatient settings. Following RSV infection, a >or=4-fold increase in homo- and heterosubtypic IgG response was noted in most subjects against the RSV G CC and PCC regions; in contrast, such titer increases against the RSV G DCC was only noted in a homosubtypic manner. Our results have implications for RSV G-based serological diagnostics and vaccine development.

A microsphere-based immunoassay for rapid and sensitive detection of bovine viral diarrhoea virus antibodies

This study describes a novel blocking microsphere-based immunoassay for highly sensitive and specific detection of antibodies against bovine viral diarrhoea virus (BVDV). The intra- and inter-assay variability are 4.9% and less than 7%, respectively, and variability of bead conjugations is less than 6.6%. The diagnostic performance of the assay was evaluated by testing a total of 509 serum samples. Based on a negative/positive cut-off value of 30.3%, the assay has a sensitivity of 99.4% and a specificity of 98.3% relative to ELISA. The new microsphere immunoassay provides an alternative to conventional ELISA systems and can be used for high-throughput screening in the BVD control programmes.

Vaccination to induce antibodies blocking the CX3C-CX3CR1 interaction of respiratory syncytial virus G protein reduces pulmonary inflammation and virus replication in mice

Respiratory syncytial virus (RSV) infection causes substantial morbidity and some deaths in the young and elderly worldwide. There is no safe and effective vaccine available, although it is possible to reduce the hospitalization rate for high-risk children by anti-RSV antibody prophylaxis. RSV has been shown to modify the immune response to infection, a feature linked in part to RSV G protein CX3C chemokine mimicry. This study determined if vaccination with G protein polypeptides or peptides spanning the central conserved region of the G protein could induce antibodies that blocked G protein CX3C-CX3CR1 interaction and disease pathogenesis mediated by RSV infection. The results show that mice vaccinated with G protein peptides or polypeptides containing the CX3C motif generate antibodies that inhibit G protein CX3C-CX3CR1 binding and chemotaxis, reduce lung virus titers, and prevent body weight loss and pulmonary inflammation. The results suggest that RSV vaccines that induce antibodies that block G protein CX3C-CX3CR1 interaction may offer a new, safe, and efficacious RSV vaccine strategy.

Multianalyte tests for the early detection of cancer: speedbumps and barriers

It has become very clear that a single molecular event is inadequate to accurately predict the biology (or pathophysiology) of cancer. Furthermore, using any single molecular event as a biomarker for the early detection of malignancy may not comprehensively identify the majority of individuals with that disease. Therefore, the fact that technologies have arisen that can simultaneously detect several, possibly hundreds, of biomarkers has propelled the field towards the development of multianalyte-based in vitro diagnostic early detection tests for cancer using body fluids such as serum, plasma, sputum, saliva, or urine. These multianalyte tests may be based on the detection of serum autoantibodies to tumor antigens, the presence of cancer-related proteins in serum, or the presence of tumor-specific genomic changes that appear in plasma as free DNA. The implementation of non-invasive diagnostic approaches to detect early stage cancer may provide the physician with evidence of cancer, but the question arises as to how the information will affect the pathway of clinical intervention. The confirmation of a positive result from an in vitro diagnostic cancer test may involve relatively invasive procedures to establish a true cancer diagnosis. If in vitro diagnostic tests are proven to be both specific, i.e. rarely produce false positive results due to unrelated conditions, and sufficiently sensitive, i.e. rarely produce false negative results, then such screening tests offer the potential for early detection and personalized therapeutics using multiple disease-related targets with convenient and non-invasive means. Here we discuss the technical and regulatory barriers inherent in development of clinical multianalyte biomarker assays.

Pathogen Detection in the Genomic Era

In the 21st century, one of the greatest challenges to public health and clinical microbiologists is the rapid detection and identification of emerging and reemerging pathogens. Complex factors such as genetic variation in the host and pathogen, environmental changes, population pressures, and global travel can all influence the emergence of infectious diseases. The SARS epidemic of 2003 highlighted the potential of an emerging pathogen to spread globally in a very short time frame (Peruski and Peruski, 2003). The diagnostics of such infectious diseases has been greatly affected in the past 20 years. No longer is cultivation and microscopy the only means of detecting infectious agents. With the introduction of molecular diagnostics, the ability to detect minute amounts of microbial nucleic acids in clinical specimens has revolutionized clinical microbiology. In particular, the utility of PCR allows the detection and quantitation of specific agents in a matter of hours. PCR sequencing of specific segments of nucleic acid allows for the determination of specific drug resistance that now aids in guiding viral therapies.

Multiplex human papillomavirus serology based on in situ-purified glutathione s-transferase fusion proteins

BACKGROUND

More than 100 different human papillomaviruses (HPVs) can cause proliferative diseases, many of which are malignant, such as cervical cancer. HPV serology is complex because infection and disease lead to distinct type-specific antibody responses. Using bead-based technology, we have developed an assay platform that allows the simultaneous detection of antibodies against up to 100 in situ affinity-purified recombinant HPV proteins.

METHODS

Twenty-seven HPV proteins were expressed as glutathione S-transferase fusion proteins and affinity-purified in one step by incubation of glutathione-displaying beads in bacterial lysate. Spectrally distinct bead sets, each carrying one particular antigen, were mixed, incubated with serum, and differentiated in a flow cytometer-like analyzer (xMAP; Luminex Corp). Antibodies bound to the antigens were detected via fluorescent secondary reagents. We studied 756 sera from 2 case-control studies of cervical cancer.

RESULTS

Glutathione S-transferase fusion proteins bound with high affinity to glutathione-displaying beads (Kd = 6.9 x 10(-9) mol/L). The dynamic range of multiplex serology covered 1.5 orders of magnitude, and antibodies were detected at serum dilutions >1:1,000,000. Imprecision (median CV) was < or = 5.4%, and assay reproducibility was high (R2 = 0.97). Results on clinical samples showed high concordance with ELISA (kappa = 0.846), but multiplex serology exhibited increased detection of weak antibody responses. Antibodies to the E6 oncoproteins of the rare HPV types 52 and 58 were associated with cervical cancer (P < 0.001).

CONCLUSION

Multiplex serology enables antibody analyses of large numbers of sera against up to 100 antigens in parallel and has the potential to replace ELISA technology.

Validation and comparison of luminex multiplex cytokine analysis kits with ELISA: determinations of a panel of nine cytokines in clinical sample culture supernatants

PROBLEM

Analyses of the expression pattern of multiple cytokines are frequently required for characterization of the status of the immune system as it pertains to Th type bias and intrinsic levels of inflammation. Classically, analysis of cytokine expression patterns has been performed by enzyme-linked immunosorbent assays (ELISA) for each separate analyte. A new technology, Luminex MAP, facilitates the simultaneous evaluation of multiple immune mediators with advantages of higher throughput, smaller sample volume, and lower cost. Validation of this technology has been limited to small sample sets, limited use of clinical study specimens, and use of non-commercial reagents.

METHODS

Ninety-six specimens from women over the course of their respective pregnancies were evaluated for cytokine concentrations using commercially available ELISA kits and commercially available Luminex MAP kits according to the manufacturers' directions. Correlations between data sets were evaluated using Pearson's correlation coefficient (r).

RESULTS

Excellent correlations were demonstrated for IL-1 beta, IL-4, IL-5, IL-6, IL-10, IFN gamma, and TNF alpha, in contrast to IL-12 p 70 and IL-13.

CONCLUSIONS

Luminex multiplex technology has distinct advantages and is a valid alternative method to ELISA for the evaluation of the majority of cytokines tested and for the characterization of immune system status.

Determination of serum IgG antibodies to Bacillus anthracis protective antigen in environmental sampling workers using a fluorescent covalent microsphere immunoassay

AIMS

To evaluate potential exposure to Bacillis anthracis (Ba) spores in sampling/decontamination workers in the aftermath of an anthrax terror attack.

METHODS

Fifty six serum samples were obtained from workers involved in environmental sampling for Ba spores at the American Media, Inc. (AMI) building in Boca Raton, FL after the anthrax attack there in October 2001. Nineteen sera were drawn from individuals both pre-entry and several weeks after entrance into the building. Nine sera each were drawn from unique individuals at the pre-entry and follow up blood draws. Thirteen donor control sera were also evaluated. Individuals were surveyed for Ba exposure by measurement of serum Ba anti-protective antigen (PA) specific IgG antibodies using a newly developed fluorescent covalent microsphere immunoassay (FCMIA).

RESULTS

Four sera gave positive anti-PA IgG results (defined as anti-PA IgG concentrations > or = the mean microg/ml anti-PA IgG from donor control sera (n = 13 plus 2 SD which were also inhibited > or = 85% when the serum was pre-adsorbed with PA). The positive sera were the pre-entry and follow up samples of two workers who had received their last dose of anthrax vaccine in 2000.

CONCLUSION

It appears that the sampling/decontamination workers of the present study either had insufficient exposure to Ba spores to cause the production of anti-PA IgG antibodies or they were exposed to anthrax spores without producing antibody. The FCMIA appears to be a fast, sensitive, accurate, and precise method for the measurement of anti-PA IgG antibodies.

Use of a recombinant envelope protein subunit antigen for specific serological diagnosis of West Nile virus infection

Serological diagnosis of West Nile virus (WNV) infection is complicated by extensive antigenic cross-reactivity with other closely related flaviviruses, such as St. Louis encephalitis virus. Here we describe a recombinant, bacterially expressed antigen equivalent to structural domain III of the WNV envelope protein that has allowed clear discrimination of antibody responses to WNV from those against other related flaviviruses in indirect enzyme-linked immunosorbent assays using standardized control antisera and field-collected samples.

Antigenic and genetic variability of human metapneumoviruses

Human metapneumovirus (HMPV) is a member of the subfamily Pneumovirinae within the family Paramyxoviridae. Other members of this subfamily, respiratory syncytial virus and avian pneumovirus, can be divided into subgroups based on genetic or antigenic differences or both. For HMPV, the existence of different genetic lineages has been described on the basis of variation in a limited set of available sequences. We address the antigenic relationship between genetic lineages in virus neutralization assays. In addition, we analyzed the genetic diversity of HMPV by phylogenetic analysis of sequences obtained for part of the fusion protein (n = 84) and the complete attachment protein open reading frames (n = 35). On the basis of sequence diversity between attachment protein genes and the differences in virus neutralization titers, two HMPV serotypes were defined. Each serotype could be divided into two genetic lineages, but these did not reflect major antigenic differences.

Nucleotide and predicted amino acid sequence-based analysis of the avian metapneumovirus type C cell attachment glycoprotein gene: phylogenetic analysis and molecular epidemiology of U.S. pneumoviruses

A serologically distinct avian metapneumovirus (aMPV) was isolated in the United States after an outbreak of turkey rhinotracheitis (TRT) in February 1997. The newly recognized U.S. virus was subsequently demonstrated to be genetically distinct from European subtypes and was designated aMPV serotype C (aMPV/C). We have determined the nucleotide sequence of the gene encoding the cell attachment glycoprotein (G) of aMPV/C (Colorado strain and three Minnesota isolates) and predicted amino acid sequence by sequencing cloned cDNAs synthesized from intracellular RNA of aMPV/C-infected cells. The nucleotide sequence comprised 1,321 nucleotides with only one predicted open reading frame encoding a protein of 435 amino acids, with a predicted M(r) of 48,840. The structural characteristics of the predicted G protein of aMPV/C were similar to those of the human respiratory syncytial virus (hRSV) attachment G protein, including two mucin-like regions (heparin-binding domains) flanking both sides of a CX3C chemokine motif present in a conserved hydrophobic pocket. Comparison of the deduced G-protein amino acid sequence of aMPV/C with those of aMPV serotypes A, B, and D, as well as hRSV revealed overall predicted amino acid sequence identities ranging from 4 to 16.5%, suggesting a distant relationship. However, G-protein sequence identities ranged from 72 to 97% when aMPV/C was compared to other members within the aMPV/C subtype or 21% for the recently identified human MPV (hMPV) G protein. Ratios of nonsynonymous to synonymous nucleotide changes were greater than one in the G gene when comparing the more recent Minnesota isolates to the original Colorado isolate. Epidemiologically, this indicates positive selection among U.S. isolates since the first outbreak of TRT in the United States.

Simultaneous detection of 15 human cytokines in a single sample of stimulated peripheral blood mononuclear cells

Cytokines secreted by cells of the immune system can alter the behavior and properties of immune or other cells. At a site of inflammation, sets of cytokines interact with immune cells, and their combined effect is often more important than the function of one isolated component. Conventional techniques, such as enzyme-linked immunosorbent assays, generally require large quantities of cells to characterize a complete cytokine profile of activated lymphocytes. The Bio-Plex system from Bio-Rad Laboratories combines the principle of a sandwich immunoassay with the Luminex fluorescent-bead-based technology. We developed a multiplex cytokine assay to detect different cytokines simultaneously in culture supernatant of human peripheral blood mononuclear cells stimulated with antigen and with mitogen. Fifteen human cytokines (interleukin 1alpha [IL-1alpha], IL-1beta, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12p70, IL-13, IL-15, IL-17, IL-18, gamma interferon, and tumor necrosis factor alpha) were validated with a panel of healthy individuals, rheumatoid arthritis patients, and juvenile idiopathic arthritis patients. Comparing the multiplex assay with a regular enzyme-linked immunosorbent assay technique with this donor panel resulted in correlation coefficients for all cytokines ranging from 0.75 to 0.99. Intra-assay variance proved to be less then 10%, whereas interassay variability ranged between 10 and 22%. This multiplex system proved to be a powerful tool in the quantitation of cytokines. It will provide a more complete picture in differences between activated lymphocyte cytokine profiles from healthy individuals and those from patients with chronic inflammatory diseases.