Fatal Community-acquired Pneumonia in Children Caused by Re-emergent Human Adenovirus 7d Associated with Higher Severity of Illness and Fatality Rate.

Human adenoviruses (HAdVs) are highly contagious pathogens causing acute respiratory disease (ARD), such as community-acquired pneumonia. HAdV-7d, a re-emergent genomic variant, has been recently reported in Asia and the United States after a several-decade absence. However, whether HAdV-7d is associated with higher severity than other types is currently unclear. In this study, the clinical and epidemiological investigation showed that fever, cough, and sore throat were the three most common respiratory symptoms of HAdV infections. HAdV-7 caused longer duration of fever, higher morbidity of tachypnea/dyspnea, pleural effusion, diarrhea, hepatosplenomegaly, consciousness alteration, as well as higher rates of pneumonia, mechanical ventilation and higher fatality rate (28.6%) than other types, particularly HAdV-3 and HAdV-2. The genomes of seven HAdV-7d isolates from mild, severe, and fatal cases were sequenced and highly similar with each other. Surprisingly, two isolates (2011, 2012) had 100% identical genomes with an earlier strain from a fatal ARD outbreak in China (2009), which elucidates the virus origin and confirms the unexpected HAdV genomic conservation and stability. Phylogenetic analysis indicated that L1 52/55-kDa DNA packaging protein may be associated with the higher severity of illness and fatality rate of HAdV-7. Clinicians need to be aware of HAdVs in children with ARD.

Changes in enterovirus serotype constituent ratios altered the clinical features of infected children in Guangdong Province, China, from 2010 to 2013.

BACKGROUND: Enterovirus (EV)-related hand, foot, and mouth disease/herpangina (HFMD/HA) has been prevalent in Guangdong Province, China, since 2010. METHODS: Clinical data for EV-related HFMD/HA inpatients admitted to the Department of Paediatrics of Zhujiang Hospital from 2010 to 2013 were retrospectively reviewed. The corresponding EV serotypes were also determined by reverse transcription-polymerase chain reaction or BLAST analysis of the sequenced partial lengths of the viral protein1/5'-untranslated region. RESULTS: A total of 867 eligible inpatients admitted during 2010-2013 were included in the study. Of these, the serotype of the responsible EV was successfully identified in 824 cases. The incidence of enterovirus 71 (EV71) infection amongst pediatric HFMD/HA inpatients decreased dramatically from 55.5 % in 2010 to 8.1 % in 2013, with a similar decrease recorded for coxsackievirus A16 (CVA16). However, the incidence of non-EV71/CVA16 infection increased from 30.0 % in 2010 to 83.8 % in 2013. We noted that the types of infection caused by different EV serotypes varied: EV71 was responsible for 100 % of the paralysis cases (26/26), 84.6 % of the deaths (11/13), and 84.1 % of cases with severe central nervous system involvement (SCNSI) (74/88); echovirus contributed to 16.4 % of the deaths (2/13) and 4.4 % of the SCNSI cases; and coxsackievirus accounted for only 2.2 % of the SCNSI cases (2/90). The clinical features of HFMD/HA cases varied greatly during the time period examined, with drastic changes in the hospitalization rates (45.1, 63.7, 36.4, and 19.1 % for 2010, 2011, 2012, and 21013, respectively), mortality rates (2.3, 0.9, 2.5, and 0.0 %, respectively), paralysis (5.1, 1.2, 5.4, and 0.0 %, respectively), SCNSI (16.8, 7.1, 12.7, and 2.2 %, respectively), and acute respiratory infection (21.1, 22.0, 45.9, and 59.0 %, respectively). CONCLUSIONS: The incidences of infection caused by different EV serotypes, along with the clinical features of HFMD/HA cases, changed drastically in Guangdong Province, China, from 2010 to 2013, with the biggest changes observed in 2013. The changed constituent ratios of the different EV serotypes might therefore be responsible for the differences in the observed clinical features of HFMD/HA during this period.

Functional properties of DENV EDIII­reactive antibodies in human DENV­1­infected sera and rabbit antiserum to EDIII.

The envelope domain III (EDIII) of the dengue virus (DENV) has been confirmed to be involved in receptor binding. It is the target of specific neutralizing antibodies, and is considered to be a promising subunit dengue vaccine candidate. However, several recent studies have shown that anti­EDIII antibodies contribute little to the neutralizing or enhancing ability of human DENV­infected serum. The present study involved an analysis of the neutralization and antibody­dependent enhancement (ADE) activities of EDIII­reactive antibodies in human convalescent sera from patients with primary DENV­1 infection and rabbit antiserum immunized with recombinant DENV­1 EDIII protein. The results indicated that serum neutralization was not associated with titres of EDIII­binding antibodies in the human DENV­1­infected sera. The depletion of anti­EDIII antibodies from these serum samples revealed that the anti­EDIII antibodies of the patients contributed little to neutralization and ADE. However, the EDIII­reactive antibodies from the rabbit antiserum exhibited protective abilities of neutralization at a high dilution (~1:50,000) and ADE at a low dilution (~1:5,000) for the homotypic DENV infection. Notably, the rabbit antiserum displayed ADE activity only at a dilution of 1:40 for the heterotypic virus infection, which suggests that EDIII­reactive antibodies may be safe in secondary infection with heterotypic viruses. These results suggest that DENV EDIII is not the predominant antigen of the DENV infection process; however, purified or recombinant DENV EDIII may be used as a subunit vaccine to provoke an effective and safe antibody response.

Enterovirus-related diarrhoea in Guangdong, China: clinical features and implications in hand, foot and mouth disease and herpangina.

BACKGROUND: A series of complications caused by enteroviruses, including meningitis, encephalitis, acute flaccid paralysis, acute cardiopulmonary failure, respiratory infection, and myocardial injury have been reported in hand, foot and mouth disease/herpangina (HFMD/HA). However, the complication of diarrhoea caused by enteroviruses has been neglected, and a summary of its clinical features and impact on HFMD/HA is unavailable. METHODS: We included inpatients with HFMD/HA admitted to the Paediatric Department of Zhujiang Hospital during 2009-2012. We summarised and compared clinical data for cases with and without diarrhoea, and determined enterovirus serotypes by reverse transcriptase polymerase chain reaction and genotyping based on a partial-length fragment of viral protein 1 or the 5'-untranslated region. RESULTS: There were 804 inpatients with HFMD/HA and 28 (3.5%) presented with diarrhoea. Gastrointestinal symptoms were mild in most cases of diarrhoea (82.1%), with high prevalence of no dehydration (82.1%), short duration of diarrhoea (78.6%) and watery stools (75.0%). The prevalence of multi-organ dysfunction syndrome (10.7 vs 0.40%) (p = 0.001), hepatic injury (14.3 vs 3.4%) (p = 0.019), myocardial injury (21.4 vs 6.1%) (p = 0.002) and convulsion (21.4 vs 7.2%) (p = 0.016) was significantly higher in the diarrhoea than no diarrhoea group. There was no significant difference between the two groups regarding prevalence of death, altered consciousness, paralysis, central nervous system involvement, or acute respiratory infection. CONCLUSIONS: Most patients with diarrhoea caused by enteroviruses circulating in Guangdong Province in 2009-2012 had mild or moderate gastrointestinal symptoms. Although enterovirus-related diarrhoea caused additional multi-organ dysfunction syndrome, hepatic injury and myocardial injury in children with HFMD/HA, timely intervention efficiently reduced disease severity and improved outcome.

[Mapping of the B Cell Neutralizing Epitopes on ED III of Envelope Protein from Dengue Virus].

Dengue virus (DENV) envelope [E] protein is the major surface protein of the virions that indued neutralizing antibodies. The domain III of envelope protein (EDIII) is an immunogenic region that holds potential for the development of vaccines; however, the epitopes of DENV EDIII, especially neutralizing B-cell linear epitopes, have not been comprehensively mapped. We mapped neutralizing B-cell linear epitopes on DENV-1 EDIII using 27 monoclonal antibodies against DENV-1 EDIII proteins from mice immunized with the DENV-1 EDIII. Epitope recognition analysis was performed using two set of sequential overlapping peptides (16m and 12m) that spanned the entire EDIII protein from DENV-1, respectively. This strategy identified a DENV-1 type- specific and a group-specific neutralizing epitope, which were highly conserved among isolates of DENV-1 and the four DENV serotypes and located at two regions from DENV-1 E, namely amino acid residues 309-320 and 381-392(aa 309-320 and 381-392), respectively. aa310 -319(310KEVAETQHGT319)was similar among the four DENV serotypes and contact residues on aa 309 -320 from E protein were defined and found that substitution of residues E309 , V312, A313 and V320 in DENV-2, -3, -4 isolates were antigenically silent. We also identified a DENV-1 type-specific strain-restricted neutralizing epitope, which was located at the region from DENV-1 E, namely amino acid residues 329-348 . These novel type- and group-specific B-cell epitopes of DENV EDIII may aid help us elucidate the dengue pathogenesis and accelerate vaccine design.

The absence of exanthema is related with death and illness severity in acute enterovirus infection.

OBJECTIVE: To clarify whether exanthema is related to illness severity in acute enterovirus infection in children. METHODS: The data of pediatric inpatients at Zhujiang Hospital during 2009-2012 with an acute enterovirus infection were reviewed retrospectively. Enterovirus infection was determined by real-time reverse transcription PCR. Clinical data were summarized and compared between cases with and without exanthema. RESULTS: A total of 780 pediatric inpatients with an acute enterovirus infection were included in this study, of whom 83 (10.6%) presented no exanthema. The percentage of deaths in the group of patients without exanthema was significantly higher than that in the group with exanthema (7.2% vs. 1.1%; p = 0.002). Central nervous system involvement (41.0% vs. 30.0%; p = 0.041), severe central nervous system (CNS) involvement (21.7% vs. 11.0%; p = 0.005), severe CNS involvement with cardiopulmonary failure (9.6% vs. 2.3%; p = 0.002), an altered level of consciousness (15.7% vs. 7.6%; p = 0.013), and convulsions (14.4% vs. 6.3%; p = 0.007) occurred significantly more frequently in the group without exanthema. CONCLUSIONS: A considerable proportion of children with an acute enterovirus infection in Guangdong Province, China during 2009-2012 presented no exanthema, and the absence of exanthema was found to be related to death and illness severity for these acute enterovirus infections. Clinicians in China should consider enterovirus as the possible pathogen when treating children with an acute pathogen infection without exanthema.

[Establishment and evaluation of a double antibody sandwich ELISA to detect Csa2 protein of Candida albicans].

OBJECTIVE: To establish a double antibody sandwich ELISA for detecting Csa2 protein in Candida albicans infection and evaluate its specificity and sensitivity. METHODS: A recombinant expression vector pPIC9K-Csa2 was constructed and transformed into Pichia pastoris GS115. A large-scale expression of recombinant Csa2 protein (rCsa2) was optimized using methanol, and the protein was purified in P. pastoris expression system. New Zealand Rabbits and guinea pigs were respectively immunized with the purified rCsa2 to prepare polyclonal antisera. The double antibody sandwich ELISA was established by choosing the optimal dilution of coating antisera and detecting antisera. Different concentrations of rCsa2 and culture supernatants of C. albicans collected at different time points were used to evaluate the sensitivity of detection. The specificity of the sandwich ELISA was evaluated by detecting culture supernatants of other three Candida spp, five Aspergillus spp, Cryptococcus neoformans and Penicillium marneffei. RESULTS: The rCsa2 protein was successfully expressed and purified. SDS-PAGE showed that its Mr was 13 300. Western blotting demonstrated that the protein bound to specific antibody. The sensitivity of the sandwich ELISA we established using the high-titer antisera was about 240 pg/mL of rCsa2, and could detect Csa2 protein in the culture supernatant of C. albicans when cultured for as early as 18 hours. There was no cross-reactivity between the culture supernatants of other 10 clinically important fungi and C. albicans. CONCLUSION: The double antibody sandwich ELISA for detecting Csa2 protein has been established with good sensitivity and specificity. Csa2 protein could be used as a new diagnostic marker of C. albicans infection.

Phenotypic and genomic characterization of human coxsackievirus A16 strains with distinct virulence in mice.

Human coxsackievirus A16 (CA16) infection results in hand, foot, and mouth disease (HFMD) along with other severe neurological diseases in children and poses an important public health threat in Asian countries. During an HFMD epidemic in 2009 in Guangdong, China, two CA16 strains (GD09/119 and GD09/24) were isolated and characterized. Although both strains were similar in plaque morphology and growth properties in vitro, the two isolates exhibited distinct pathogenicity in neonatal mice upon intraperitoneal or intracranial injection. Complete genome sequences of both CA16 strains were determined, and the possible virulence determinants were analyzed and predicted. Phylogenetic analysis revealed that these CA16 isolates from Guangdong belonged to the B1b genotype and were closely related to other recent CA16 strains isolated in mainland China. Similarity and bootscanning analyses of these CA16 strains detected homologous recombination with the EV71 prototype strain BrCr in the non-structural gene regions and the 3'-untranslated regions. Together, the phenotypic and genomic characterizations of the two clinical CA16 isolates circulating in China were compared in detail, and the potential amino acid residues responsible for CA16 virulence in mice were predicted. These findings will help explain the evolutionary relationship of the CA16 strains circulating in China, warranting future studies investigating enterovirus virulence.

Dengue virus envelope domain III immunization elicits predominantly cross-reactive, poorly neutralizing antibodies localized to the AB loop: implications for dengue vaccine design.

Dengue virus (DENV) is a mosquito-borne virus that causes severe health problems. An effective tetravalent dengue vaccine candidate that can provide life-long protection simultaneously against all four DENV serotypes is highly anticipated. A better understanding of the antibody response to DENV envelope protein domain III (EDIII) may offer insights into vaccine development. Here, we identified 25 DENV cross-reactive mAbs from immunization with Pichia pastoris-expressed EDIII of a single or all four serotype(s) using a prime-boost protocol, and through pepscan analysis found that 60 % of them (15/25) specifically recognized the same highly conserved linear epitope aa 309-320 of EDIII. All 15 complex-reactive mAbs exhibited significant cross-reactivity with recombinant EDIII from all DENV serotypes and also with C6/36 cells infected with DENV-1, -2, -3 and -4. However, neutralization assays indicated that the majority of these 15 mAbs were either moderately or weakly neutralizing. Through further epitope mapping by yeast surface display, two residues in the AB loop, Q316 and H317, were discovered to be critical. Three-dimensional modelling analysis suggests that this epitope is surface exposed on EDIII but less accessible on the surface of the E protein dimer and trimer, especially on the surface of the mature virion. It is concluded that EDIII as an immunogen may elicit cross-reactive mAbs toward an epitope that is not exposed on the virion surface, therefore contributing inefficiently to the mAbs neutralization potency. Therefore, the prime-boost strategy of EDIII from a single serotype or four serotypes mainly elicited a poorly neutralizing, cross-reactive antibody response to the conserved AB loop of EDIII.

Evaluation and analysis of dengue virus enhancing and neutralizing activities using simple high-throughput assays.

The risk of antibody-dependent enhancement (ADE) of dengue virus (DENV) infection is a major obstacle for the development of dengue vaccine candidates. Here, we described a novel approach for assessment of ADE by measuring DENV nonstructural protein 1 (NS1) production in culture supernatants with Fcγ receptor-expressing K562 cells in ELISA format (ELISA-ADE). Enhancing activities quantified by measurement of kinetics of NS1 production were in a good agreement with the results of the virus titration assay. In conjunction with the previously established enzyme-linked immunospot-based micro-neutralization test (ELISPOT-MNT) in 96-well format, the observable dose-response profiles of enhancing and neutralizing activities against all four DENV serotypes were produced with two flaviviral envelope cross-reactive monoclonal antibodies and four primary DENV-1-infected human sera. The simple high-throughput ELISA-ADE assay offers advantages for quantitative measurement of infection enhancement that can potentially be applied to large-scale seroepidemiological studies of DENV infection and vaccination.

Comparison of surface plasmon resonance, resonant waveguide grating biosensing and enzyme linked immunosorbent assay (ELISA) in the evaluation of a dengue virus immunoassay.

Two label-free biosensor platforms, Resonance Waveguide Grating (RWG) and Surface Plasmon Resonance (SPR), were used to rank a large panel of anti-dengue virus NS1 antibodies. Dengue non-structural 1 (NS1) protein is an established serological marker for the early detection of dengue infection. A variety of commercial dengue NS1 antigen capture immunoassays are available in both ELISA and lateral flow format. However, there is a significant scope to improve both the sensitivity and the specificity of those tests. The interactions of antibody (Ab)-antigen (Ag) were profiled, with weak interactions (KD = 1-0.1 µM) able to be detected under static equilibrium conditions by RWG, but not observed to under more rigorous flow conditions using SPR. There were significant differences in the absolute affinities determined by the two technologies, and there was a poor correlation between antibodies best ranked by RWG and the lower limit of detection (LLOD) found by ELISA. Hence, whilst high-throughput RWG can be useful as preliminary screening for higher affinity antibodies, care should be exercised in the assignation of quantitative values for affinity between different assay formats.

Evaluation of human enterovirus 71 and coxsackievirus A16 specific immunoglobulin M antibodies for diagnosis of hand-foot-and-mouth disease.

BACKGROUND: Hand-foot-and-mouth disease (HFMD) is caused mainly by the human enterovirus type 71 (HEV71) and the Coxsackievirus A group type 16 (CVA16). Large outbreaks of disease have occurred frequently in the Asia-Pacific region. Reliable methods are needed for diagnosis of HFMD in children. IgM-capture ELISA, with its notable advantages of convenience and low cost, provides a potentially frontline assay. We aimed to evaluate the newly developed IgM-capture ELISAs for HEV71 and CVA16 in the diagnosis of HFMD, and to measure the kinetics of IgM over the course of HEV71 or CVA16 infections. RESULTS: We mapped, for the first time, the kinetics of IgM in HEV71 and CVA16 infection. HEV71- and CVA16-IgM were both detectable in some patients on day 1 of illness, and in 100% of patients by day 5 (HEV71) and day 8 (CVA16) respectively; both IgMs persisted for several weeks. The IgM detection rates were 90.2% (138 of 153 sera) and 68.0% (66 of 97 sera) for HEV71 and CVA16 infections, respectively, during the first 7 days of diseases. During the first 90 days after onset these values were 93.6% (233 of 249 sera) and 72.8% (91 of 125 sera) for HEV71 and CVA16 infections, respectively. Some cross-reactivity was observed between HEV71- and CVA16-IgM ELISAs. HEV71-IgM was positive in 38 of 122 (31.1%) CVA16 infections, 14 of 49 (28.6%) other enteroviral infections and 2 of 105 (1.9%) for other respiratory virus infected sera. Similarly, CVA16-IgM was apparently positive in 58 of 211 (27.5%) HEV71 infections, 16 of 48 (33.3%) other enterovirus infections and 3 of 105 (2.9%) other respiratory virus infected sera. Nevertheless, the ELISA yielded the higher OD450 value of main antibody than that of cross-reaction antibody, successfully identifying the enteroviral infection in 96.6% (HEV71) and 91.7% (CVA16) cases. When blood and rectal swabs were collected on the same day, the data showed that the agreement between IgM-capture ELISA and real-time RT-PCR in HEV71 was high (Kappa value = 0.729) while CVA16 somewhat lower (Kappa value = 0.300). CONCLUSIONS: HEV71- and CVA16-IgM ELISAs can be deployed successfully as a convenient and cost-effective diagnostic tool for HFMD in clinical laboratories.

Enzyme-linked immunosorbent assay-format tissue culture infectious dose-50 test for titrating dengue virus.

A dengue nonstructural protein 1 (NS1) antigen capture enzyme-linked immunosorbent assay (ELISA)-based tissue culture infectious dose-50 (TCID(50)) test (TCID(50)-ELISA) was developed as an alternative to the standard plaque assay for titrating dengue virus. Virus titers obtained by TCID(50)-ELISA were comparable to those obtained by the plaque assay and by the traditional TCID(50)-cytopathic effect (CPE) test (TCID(50)-CPE), with a better reproducibility and a lower coefficient of variation. Quantitative comparison of TCID(50)-ELISA and TCID(50)-CPE resulted in a correlation coefficient of 0.976. Moreover, this new method showed a wider application to C6/36, Vero E6, BHK-21, and Vero cells compared with other titration methods. In summary, the novel TCID(50)-ELISA method described here provides a more reliable and more accurate alternative compared to the plaque assay and TCID(50)-CPE for titration of dengue virus.

Cross-reactivity of anti-EV71 IgM and neutralizing antibody in series sera of patients infected with Enterovirus 71 and Coxsackievirus A 16.

OBJECTIVES: To evaluate the cross-reactivity of anti-EV71 IgM and neutralizing antibody in series sera of patients infected with EV71 and CA16. METHODS: Real-time RT-PCR, virus isolation, ELISA and neutralization test were used to detect enteroviruses from clinical specimens and series sera of 79 HFMD patients. RESULTS: 27 EV71, 37 CA16, and 11 other enterovirus-infected patients were identified by RT-PCR. Among EV71 infected patients, anti-EV71 IgM positive ratios were 87.5% during 1-3 days after onset and 100% over 4 days after onset. In CA16 infected patients, the positive ratios were 7.4%, 26.4%, and 62.5% during 1-3 days, 4-6 days, and over 6 days after onset, respectively. Meanwhile, the results of neutralization test showed 18.9% of CA16 infected patients and 11.1% of EV71 infected patients present high cross-neutralization antibody against each other. CONCLUSIONS: Cross-reactivity of anti-EV71 IgM in patients infected with EV71 and CA16 becomes stronger with the progress of disease. Moreover, high cross-neutralization antibody existing in part of patients suggests that the immune reactivity to EV71 infection can be recalled by CA16, and the immune reactivity to CA16 infection can be recalled by EV71. Therefore, identifying enteroviruses by neutralization test may not be an ideal selection.

Kinetics of non-structural protein 1, IgM and IgG antibodies in dengue type 1 primary infection.

BACKGROUND: Early and accurate diagnosis of dengue infection is essential for control of disease outbreaks. Recently, the dengue virus non-structural antigen 1 (NS1), a conserved and secreted glycoprotein, has been used as a marker for early diagnosis of dengue with convenience and cost-effectiveness. Serological tests of dengue IgM and IgG antibodies are still the most widely used for diagnosis of dengue. In order to assess combined diagnostic value of these tests, we study the kinetic profiles of circulating NS1, dengue IgM and IgG antibodies over the course of the disease by using an in-house dengue type 1 (DENV1) specific NS1 capture ELISA and the commercial Panbio Dengue IgM and IgG capture ELISAs. RESULTS: A panel of 313 acute-and early convalescent-phase serum specimens from 140 DENV1 primary infected patients during an outbreak of dengue in Guangzhou, China, in 2006 were studied. Dengue NS1 presented high levels in acute-phase serum samples. It was detectable as early as day 1 of illness, and up to 14 day after onset. The sensitivity of NS1 detection was ranged from 81.8% to 91.1% with samples taken during the first 7 days. Anti-dengue IgM antibody was detectable on the third day of onset with the positive rate of 42.9%, and rapidly increasing to 100% by day 8 of illness. Anti-dengue IgG antibody was detectable on the fifth day of onset with low level at the first week of onset, and slowly increasing to 100% by day 15 of illness. Combining the results of NS1 and IgM antibody detection allowed positive diagnosis in 96.9%-100% for samples taken after day 3 of onset. CONCLUSIONS: Dengue NS1 detection might shorten the window period by first few days of illness. A combination of dengue NS1 antigen and IgM antibody testing facilitates enhanced diagnosis rates. The procedures should be suitable for developing countries where dengue is endemic.

Full serotype- and group-specific NS1 capture enzyme-linked immunosorbent assay for rapid differential diagnosis of dengue virus infection.

Dengue virus (DENV), a member of the Flavivirus family, has four distinct serotypes (DENV serotype 1 [DENV1], DENV2, DENV3, and DENV4) that require differentiation for the effective prevention of morbid disease. Early and rapid differentiation between flaviviruses remains challenging. Full assays combining four individual, serotype-specific and one group-specific nonstructural protein 1 (NS1) antigen capture enzyme-linked immunosorbent assays (ELISAs) based on monoclonal antibodies (MAbs) against DENV NS1 were developed and validated. The sensitivities and specificities of the full NS1 ELISAs were evaluated with viral cultures and dengue acute-phase sera. Four serotype-specific NS1 ELISAs displayed high specificities for the detection and differentiation of appropriate serotypes. The group-specific NS1 ELISA was broadly reactive with the four dengue virus serotypes. None of the NS1 ELISAs displayed cross-reactivity with the other flaviviruses or samples from febrile patients with non-dengue virus infections. The full serotype- and group-specific MAb-based NS1 capture ELISAs may provide tools for the early detection and typing of dengue infection, which is preferable to reverse transcriptase PCR (RT-PCR) for the rapid differential diagnosis of dengue virus infection in the field.

Comprehensive mapping of immunodominant and conserved serotype- and group-specific B-cell epitopes of nonstructural protein 1 from dengue virus type 1.

The dengue virus (DENV) nonstructural protein 1 (NS1) is an immunogenic protein that holds potential for the development of vaccines and diagnostic reagents; however, the epitopes of NS1 have not been comprehensively mapped. We mapped B-cell linear epitopes on NS1 using 149 monoclonal antibodies with DENV serotype specificity and cross-reactivity as well as antisera from 27 mice immunized with the four DENV serotypes. Epitope recognition analysis was performed using a set of 15-mer sequential overlapping peptides that spanned the entire NS1 protein from DENV-1. This strategy identified three regions of NS1 that are DENV-1 serotype-specific epitopes, namely amino acid residues 1-15, 71-85, and 338-352. We also identified five group-specific B-cell epitopes that were highly conserved among isolates of the four DENV serotypes. These novel immunodominant serotype- and group-specific B-cell epitopes of DENV NS1 may aid the development of new dengue vaccines and diagnostic assays.

[To evaluate the neutralizing abilities of anti-dengue virus antibodies with nonstructural protein 1 antigen capture enzyme-linked immunosorbent assay].

OBJECTIVE: To produce neutralizing antibodies against envelope protein domain III (EDIII) of dengue virus serotype I (DENV-1) and evaluate the nonstructural protein 1 (NS1) antigen capture enzyme-linked immunosorbent assay (ELISA) for identification of antibody neutralizing abilities. METHODS: Five BALB/c mice and one New Zealand Rabbit were immunized with recombinant EDIII protein of DENV-1 for the production of hybridomas and hyperimmune sera. Indirect ELISA, immunofluorescence assay (IFA) and Western Blot analyses were applied to identify specificity of antibodies. Comparing to plaque reduction neutralization test (PRNT), the new established DENV-1 specific NS1 antigen capture ELISA was used for detecting the neutralizing abilities of these antibody. RESULTS: Four strains of monoclonal antibodies (mAbs) named 1A1, 1B3, 3D3 and 9D6 and one hyperimmune serum of rabbit were obtained, all of which were approved to have neutralizing abilities to DENV-1 with the PRNT titer of 1:1024, 1:512, 1:256, 1:4096 and 1:4096. MAb 3D3 with the lowest neutralization titer in PRNT had not shown neutralizing ability to DENV-1 in NS1 antigen capture ELISA, while MAbs 1A1, 1B3 and 9D6 and the rabbit hyperimmune serum could protect the C6/36 from being infected by DENV-1 with the neutralization titer of 1:32, 1:32, 1:128 and 1:128 in this assay. CONCLUSION: NS1 antigen capture ELISA could be used to identify antibody neutralizing abilities to DENV, it was a faster and more convenient way to screen antibodies with high neutralization titer and might also be used as one of the methods to evaluate the effects of vaccines.

Development of an antigen capture immunoassay based on monoclonal antibodies specific for dengue virus serotype 2 nonstructural protein 1 for early and rapid identification of dengue virus serotype 2 infections.

The dengue virus (DENV) has four distinct serotypes (DENV1, DENV2, DENV3, and DENV4) that require differentiation for effective prevention of morbid diseases. The recently developed DENV1-specific NS1 antigen capture enzyme-linked immunosorbent assay (ELISA) based on the monoclonal antibodies (MAbs) that recognize distinct epitopes on nonstructural protein 1 (NS1) of a specific DENV serotype is convenient and cost-effective, but assays have not yet been developed for DENV serotypes 2 to 4. This paper describes the development and validation of a DENV2-specific NS1 antigen capture ELISA by selection and optimization of the pair of well-characterized MAbs that recognized epitopes specific for DENV2 NS1 from a large panel of MAbs. The DENV2 NS1 ELISA displayed exclusive sensitivity with the DENV2 serotype and did not cross-react with the other three DENV serotypes. The sensitivity and specificity of the DENV2 NS1 ELISA were 83.3% (25/30) and 100% (504/504) when used to test 30 acute-phase serum samples from patients infected with DENV2 identified by virus isolation or reverse transcription-PCR serotyping and 504 serum samples from healthy individuals, respectively. The specificity of this assay was also evaluated using a panel of serum samples which were positive for DENV1, other flaviviruses, and nonflaviviruses; no cross-reactions were observed in these clinical samples. The DENV2 NS1 ELISA was eightfold more sensitive than a commercially available serotype-cross-reactive NS1 ELISA (Panbio Diagnostics, Brisbane, Australia) when the two assays were used to test the DENV2-infected cell culture supernatants in parallel. The Panbio NS1 ELISA displayed variation in sensitivity between DENV serotypes. The DENV2-specific NS1 antigen capture ELISA can be used as a tool for the rapid identification of DENV2 infections.

Well-characterized monoclonal antibodies against cell wall antigen of Aspergillus species improve immunoassay specificity and sensitivity.

The diagnosis of invasive aspergillosis (IA) based on the detection of Aspergillus galactomannan (GM) is complicated by the presence of cross-reactive GM epitopes in patient specimens. We have developed a novel and specific Aspergillus antigen-capture enzyme-linked immunosorbent assay (ELISA) by the selection of two well-characterized monoclonal antibodies from 17 candidate antibodies. The epitopes recognized by the monoclonal antibodies were present on the cell walls of the hyphae and the conidia of Aspergillus species, which were circulating or excreted as immunodominant antigens during the acute phase of IA established in the animal models. The detection of experimental Aspergillus-mediated antigenemia was suitably sensitive, and the sensitivity was comparable to that of a commercial GM detection ELISA kit (the Platelia Aspergillus assay). Moreover, the specificity of this assay was 100% when it was used to test 382 serum specimens and 120 urine specimens from healthy individuals. Cross-reactivity with other common opportunistic fungi, such as Penicillium and Candida species, and with purified GM protein derived from Aspergillus was not evident. Therefore, the chemical nature of the epitopes captured in this assay is most likely not associated with the GM structure, indicating that this newly developed Aspergillus antigen-capture ELISA is a promising tool for the diagnosis of IA without the risk of the false-positive results that are problematic with current GM antigen assays.