Identification of promoter polymorphisms in the cytochrome P450 CYP6AY1 linked with insecticide resistance in the brown planthopper, Nilaparvata lugens

Imidacloprid resistance in the brown planthopper, Nilaparvata lugens, is primarily the result of the over-expression of cytochrome P450 monooxygenases. Here, a field-collected strain of N. lugens was shown to be highly resistant to both imidacloprid and buprofezin. Insecticide exposure and quantitative real-time PCR revealed that its resistance was mainly associated with a cytochrome P450 gene, CYP6AY1. CYP6AY1 is known to metabolize imidacloprid but its effect on buprofezin is unclear. In the 5'-untranslated region of CYP6AY1, a novel alternative splicing was detected. After a 1990-bp promoter region was cloned, its basal luciferase activity was assessed. Furthermore, genotyping studies identified 12 variations in the promoter region that discriminated between the field-collected and control strain. Finally, survival bioassays revealed a single nucleotide polymorphism and an insertion-deletion polymorphism linked to buprofezin and imidacloprid resistance. Mutagenesis of these sites enhanced the promoter activity of CYP6AY1. These results suggest that promoter polymorphisms may affect P450-mediated multiple insecticide resistance of pests.

Brain-derived neurotrophic factor accelerates gut motility in slow-transit constipation

BACKGROUND & AIMS

Brain-derived neurotrophic factor (BDNF) may play a critical role in gut motility. We aimed to investigate BDNF's physiologic effects on gut motility in slow-transit constipation (STC) and to explore the underlying molecular mechanisms.

METHODS

BDNF expression and alterations of colonic nerve fibre density in STC patients were first investigated. BDNF's effects on gastrointestinal motility of both BDNF(+/-) mice and loperamide-induced constipation mice were then examined in vivo and in vitro. Smooth muscle α-actin (α-SMA) expression, and nerve fibre, neuromuscular junction (NMJ) and smooth muscle cell (SMC) alterations were investigated. Finally, the effects of BDNF-induced TrkB-phospholipase C/inositol trisphosphate (TrkB-PLC/IP3) pathway activation on gut motility were investigated.

RESULTS

In STC patients, BDNF expression and nerve fibre density were decreased, and mucosal nerve fibre ultrastructural degenerations were demonstrated. Gut motility was decreased in vivo and in vitro in BDNF(+/-) and constipation mice, with BDNF dose-dependently increasing gut motility. In BDNF(+/-) mice, α-SMA expression and nerve fibre density were decreased, and nerve fibre, NMJ and SMC ultrastructural degenerations were observed. Finally, TrkB-PLC/IP3 pathway antagonists dramatically attenuated BDNF's excitatory effect on gut motility, and exogenous BDNF induced an obvious increase in IP3 expression.

CONCLUSIONS

BDNF plays an important regulatory role in gut motility in STC. It was mediated by altering the intestinal innervation structure, as well as smooth muscle secondary degeneration through a mechanism involving TrkB-PLC/IP3 pathway activation.

Stimulated release of a hyperpolarizing factor (ADHF) from mesenteric artery perivascular adipose tissue: involvement of myocyte BKCa channels and adiponectin

BACKGROUND AND PURPOSE

Perivascular adipose tissue (PVAT) releases adipocyte-derived hyperpolarizing factors (ADHFs) that may partly act by opening myocyte K(+) channels. The present study in rat and mouse mesenteric arteries aimed to identify the myocyte K(+) channel activated by PVAT and to determine whether adiponectin contributed to the hyperpolarizing effects of PVAT.

EXPERIMENTAL APPROACH

Myocyte membrane potential was recorded from de-endothelialized, non-contracted rat and mouse mesenteric arteries in the presence and absence of PVAT.

KEY RESULTS

The β3 -adrenoceptor agonist, CL-316,243 (10 μM), generated PVAT-dependent, iberiotoxin-sensitive myocyte hyperpolarizations resulting from BKCa channel opening and which were partially blocked by L-NMMA (100 μM). Adiponectin (5 μg·mL(-1) ) also produced iberiotoxin-sensitive hyperpolarizations in PVAT-denuded arterioles. Activation of myocyte AMP-activated protein kinase (AMPK) using 5 μM A-769662 also induced BKCa -mediated hyperpolarizations. Dorsomorphin abolished hyperpolarizations to CL-316,243, adiponectin and A-769662. In vessels from Adipo(-/-) mice, hyperpolarizations to CL-316,243 were absent whereas those to A-769662 and adiponectin were normal. In rat vessels, adipocyte-dependent hyperpolarizations were blocked by glibenclamide and clotrimazole but those to NS1619 (33 μM) were unaltered.

CONCLUSIONS AND IMPLICATIONS

Under basal, non-contracted conditions, β3 -adrenoceptor stimulation of PVAT releases an ADHF, which is probably adiponectin. This activates AMPK to open myocyte BKCa channels indirectly and additionally liberates NO, which also contributes to the observed PVAT-dependent myocyte hyperpolarizations. Clotrimazole and glibenclamide each reversed hyperpolarizations to adiponectin and A-769662, suggesting the involvement of myocyte TRPM4 channels in the ADHF-induced myocyte electrical changes mediated via the opening of BKCa channels.

Temporal dynamics and population genetic structure of Fusarium graminearum in the upper Midwestern United States

Fusarium graminearum sensu stricto causes Fusarium head blight (FHB) in wheat and barley, and contaminates grains with several trichothecene mycotoxins, causing destructive yield losses and economic impact in the United States. Recently, a F. graminearum strain collected from Minnesota (MN) was determined to produce a novel trichothecene toxin, called NX-2. In order to determine the spatial and temporal dynamics of NX-2 producing strains in MN, North Dakota (ND) and South Dakota (SD), a total of 463 F. graminearum strains were collected from three sampling periods, 1999-2000, 2006-2007 and 2011-2013. A PCR-RFLP based diagnostic test was developed and validated for NX-2 producing strains based on polymorphisms in the Tri1 gene. Trichothecene biosynthesis gene (Tri gene)-based polymerase chain reaction (PCR) assays and ten PCR-restriction fragment length polymorphism (RFLP) markers were used to genotype all strains. NX-2 strains were detected in each sampling period but with a very low overall frequency (2.8%) and were mainly collected near the borders of MN, ND and SD. Strains with the 3ADON chemotype were relatively infrequent in 1999-2000 (4.5%) but increased to 29.4% in 2006-2007 and 17.2% in 2011-2013. The distribution of 3ADON producing strains also expanded from a few border counties between ND and MN in 1999-2000, southward toward the border between SD and MN in 2006-2007 and westward in 2011-2013. Genetic differentiation between 2006-2007 and 2011-2013 populations (3%) was much lower than that between 1999-2000 and 2006-2007 (22%) or 1999-2000 and 2011-2013 (20%) suggesting that most change to population genetic structure of F. graminearum occurred between 1999-2000 and 2006-2007. This change was associated with the emergence of a new population consisting largely of individuals with a 3ADON chemotype. A Bayesian clustering analysis suggested that NX-2 chemotype strains are part of a previously described Upper Midwestern population. However, these analyses also suggest that the NX-2 isolates could represent a distinct population, but that interpretations of population assignment are influenced by the small number of NX-2 strains available for analysis.

microRNA-221 and microRNA-18a identification in stool as potential biomarkers for the non-invasive diagnosis of colorectal carcinoma

BACKGROUND

The detection of microRNA (miRNA) dysregulation in stool is a novel approach for the diagnosis of colorectal carcinoma (CRC). The aim of this study is to investigate the use of miR-221 and miR-18a in stool samples as non-invasive biomarkers for CRC diagnosis.

METHODS

A miRNA expression array containing 667 miRNAs was performed to identify miRNA dysregulation in CRC tissues. We focused on miR-221 and miR-18a, two significantly upregulated miRNAs which were subsequently verified in 40 pairs of CRC tissues and 595 stool samples (198 CRCs, 199 polyps and 198 normal controls).

RESULTS

miR-221 and miR-18a were upregulated in the miRNA expression array. miR-221 and miR-18a levels were also significantly higher in 40 CRC tumours compared with their respective adjacent normal tissues. In stool samples, miR-221 and miR-18a showed a significant increasing trend from normal controls to late stages of CRC (P<0.0001). The levels of stool miR-221 and miR-18a were both significantly higher in subjects with stages I+II (miR-221: P<0.0001, miR-18a: P<0.0001) and stages III+IV of CRC (miR-221: P=0.0004, miR-18a: P<0.0001) compared with normal controls. The AUC of stool miR-221 and miR-18a were 0.73 and 0.67 for CRC patients as compared with normal controls, respectively. No significant differences in stool miR-221 and miR-18a levels were found between patients with proximal and distal CRCs. The use of antibiotics did not influence stool miRNA-221 and miRNA-18a levels.

CONCLUSIONS

Stool-based miR-221 can be used as a non-invasive biomarker for the detection of CRC.

Modulation of interhemispheric functional coordination in electroconvulsive therapy for depression

Considerable evidence suggests that depression is related to interhemispheric functional coordination deficits. For depression, electroconvulsive therapy (ECT) is the most rapid and effective therapy, but its underlying mechanism remains unknown. The aim of this study was to explore the impact of ECT on the interhemispheric functional coordination in depression patients. We used resting-state functional magnetic resonance imaging to observe the change of interhemispheric functional coordination with the method of voxel-mirrored homotopic connectivity (VMHC) in 11 depressed patients before and after ECT, compared with 15 healthy controls. The results showed that, compared with depression patients before ECT, VMHC was significantly increased in superior frontal gyri (BA 8), middle frontal gyri (two clusters: BA 8/9 and BA 10) and angular gyri (BA 39) in depression patients after ECT. Compared with healthy controls, VMHC in those areas was significantly lower in the middle frontal gyri (BA 8/9) and angular gyri (BA 39) in depression patients before ECT, but no significant difference was observed in the superior frontal gyri (BA 8) and middle frontal gyri (BA 10). There was no significant correlation between the changes of Hamilton Depression Rating Scale scores and changed VMHC values in those four areas in depression patients. The results suggest that ECT selectively modulated interhemispheric functional coordination in depression patients. Such may play an important mechanistic role in the treatment of depression, and may afford a useful avenue for optimizing treatment.

Early assessment of chronic kidney dysfunction using contrast-enhanced ultrasound: a pilot study

OBJECTIVE

We performed a prospective study to evaluate the value of contrast-enhanced (CE) ultrasound in quantitative evaluation of renal cortex perfusion in patients with chronic kidney dysfunction (CKD Stage I-II).

METHODS

The present study was approved by the institutional ethics committee. The study focused on 41 consecutive patients (males, 32; females, 9; mean age, 55.0 ± 5.0 years) with clinical suspicion of CKD (Stages I-II). For both kidneys, CE ultrasound was performed after intravenous bolus injection of 1.0 ml SonoVue® (Bracco Imaging S.p.A., Milan, Italy). Time-intensity curves (TICs) and quantitative indexes were created with Qlab software (Philips, Bothell, WA). 45 healthy volunteers were included as control group. All statistical analyses were performed with SPSS® v. 15.0 software package (SPSS, Chicago, IL). A difference was considered statistically significant with p < 0.05.

RESULTS

Patients with CKD (Stages I-II) had no obvious change in the shape of TICs. Among all quantitative indexes, the changes of area under the curve (AUC), derived peak intensity (DPI) and slope rate of elevation curve (A) were statistically significant (p < 0.05). DPI <12 dB, A >2 and AUC >1300 dB s had high utility in the evaluation of CKD, with 81%, 73% and 78% specificities and 76%, 73% and 77% sensitivities.

CONCLUSION

CE ultrasound might be valuable in the early evaluation of CKD. AUC, A and DPI might be valuable quantitative indexes.

ADVANCES IN KNOWLEDGE

Quantitative CE ultrasound analysis can be used for the standardized and early evaluation of renal dysfunction.

Detection of fetal sex chromosome aneuploidy by massively parallel sequencing of maternal plasma DNA: initial experience in a Chinese hospital

OBJECTIVES

To evaluate the performance of a massively parallel sequencing (MPS)-based test in detecting fetal sex chromosome aneuploidy (SCA) and to present a comprehensive clinical counseling protocol for SCA-positive patients.

METHODS

This was a retrospective study in a large patient cohort of 5950 singleton pregnancies which underwent MPS-based testing as a prenatal screening test for trisomies 21, 18 and 13, with X and Y chromosomes as secondary findings, in Southwest Hospital in China. MPS-based SCA-positive women were offered the choice of knowing whether their SCA results were positive and those who did commenced a two-stage post-test clinical counseling protocol. In Stage 1, general information about SCA was given, and women were given the option of invasive testing for confirmation of findings; in Stage 2, those who had chosen to undergo invasive testing were informed about the specific SCA affecting their fetus and their management options.

RESULTS

Thirty-three cases were classified as SCA-positive by MPS-based testing. After Stage 1 of the two-stage post-test clinical counseling session, 33 (100%) of these pregnant women chose to know the screening test results, and 25 (75.76%) underwent an invasive diagnostic procedure and karyotype analysis, in one of whom karyotyping failed. In thirteen cases, karyotyping confirmed the MPS-based test results (two X0 cases, seven XXX cases, three XXY cases and one XYY case), giving a positive predictive value of 54.17% (13/24 cases confirmed by karyotyping). After post-test clinical counseling session Stage 2, seven women chose to terminate the pregnancy: one X0 case, two XXX cases, the three XXY cases and the single XYY case. Six women decided to continue with pregnancy: one X0 case and five XXX cases.

CONCLUSION

Our study showed the feasibility of clinical application of the MPS-based test in the non-invasive detection of fetal SCA. Together with a two-stage post-test clinical counseling protocol, it leads to a well-informed decision-making procedure.

Birth of a healthy child by a woman with inherited Xq duplications who had experienced stillbirths

A 23-year-old woman who had experienced repeated stillbirths, was found to carry an additional segment on the long arm of the X chromosome. Array comparative genomic hybridization (aCGH) confirmed the origin of the 2 duplications (about 17.11 Mb). Thus, her karyotype was 46, X, dup (X) (q13.2-q21.1), dup(X) (q21.32-q22.1). We demonstrate that aCGH is a useful complementary tool to cytogenetic analysis for accurately determining banding. To our knowledge, this is the first case with normal apparently phenotype who inherited 2 duplications on Xq. Notably, after 2 stillbirths, she bore a healthy, normal female infant via natural pregnancy. Thus, a carrier of this karyotype can birth a phenotypically normal child.

Effects of monochromatic light stimuli on the development and Muc2 expression of goblet cells in broiler small intestines during embryogenesis

The effects of monochromatic light on the ontogeny, differentiation, and Muc2 expression level in goblet cells were studied in the small intestines of late-stage broiler embryos. The embryos were exposed to blue light (B group), green light (G group), red light (R group), or darkness (D group) throughout the incubation period. On d 15 of incubation (E15), a few acidic goblet cells (only the sulfated subtype) were observed, and Muc2 mRNA expression was detected. On E18, however, neutral, acidic, and intermediate types, as well as the sulfated subtype, were observed in the small intestine, and a decreasing gradient of goblet cell density was found along the duodenum to ileum axis. Up to E21, 3 types of goblet cells and 3 acidic cell subtypes were found in all the small intestines. The goblet cell density increased along the duodenum to ileum axis. Monochromatic light stimulation resulted in no significant differences in the density and types of goblet cells between the different treatment groups on E15 and E18, but an increased Muc2 mRNA expression level was detected on E18 in the G group compared with the other treatment groups. On E21, the goblet cell density, proportion of acidic goblet cells, and Muc2 mRNA expression level increased in the G group compared with other treatment groups. These results suggest that the ontogeny and differentiation of goblet cells in broiler embryos display temporal and spatial differences. Green monochromatic light may have the potential to promote the proliferation and maturation of as well as the expression of Muc2 mRNA in goblet cells of broiler embryos.

Sevoflurane inhibits neurogenesis and the Wnt-catenin signaling pathway in mouse neural progenitor cells

Recent population studies suggest that children who receive anesthesia and surgery could be at an increased risk for developing learning disabilities. The underlying reason for this clinical observation is largely unknown. Whether undergoing anesthesia contributes to learning disability development, or if the need for anesthesia and surgery is a marker for other unidentified factors that contribute to the development of learning disabilities, remains to be determined. Neurogenesis, regulated by the Wnt-catenin signaling pathway, has been shown to be involved in learning and memory, and sevoflurane is the most commonly used inhalation anesthetic in children. We therefore set out to determine the effects of sevoflurane on neurogenesis and the Wnt-catenin signaling pathway in mouse neural progenitor cells (NPCs) using immunofluorescence and Western blot analysis. Here we show for the first time that 4.1%, but not 2.0%, sevoflurane reduced mouse NPC proliferation, increased Glycogen synthase kinase-3β(GSK-3β) levels, and decreased levels of β-Catenin in mouse NPCs. The GSK-3β inhibitor Lithium attenuated the sevoflurane-induced reduction in mouse NPC proliferation. The data suggest that sevoflurane may reduce neurogenesis through the Wnt-catenin signaling pathway. These findings would promote further studies to investigate the effects of anesthesia on neurogenesis and function of learning and memory, as well as the underlying mechanisms in vitro and in vivo. Ultimately these efforts would lead to safer anesthesia care and better postoperative outcomes in children.

Isoflurane induces endoplasmic reticulum stress and caspase activation through ryanodine receptors

BACKGROUND

Isoflurane has been reported to induce caspase-3 activation, which may induce neurotoxicity and contribute to the pathogenesis of Alzheimer's disease. However, the underlying mechanism is largely unknown, especially whether or not isoflurane can induce ryanodine receptors (RyRs)-associated endoplasmic reticulum (ER) stress, leading to caspase-3 activation. We therefore assessed the effects of isoflurane on RyRs-associated ER stress.

METHODS

We treated primary neurones from wild-type (C57BL/6J) mice with 1% and 2% isoflurane for 1, 3, or 6 h. We then measured levels of C/EBP homologous protein (CHOP) and caspase-12, two ER stress markers, using immunocytochemistry staining and western blotting analysis. Dantrolene (5 μM), the antagonist of RyRs, was used to investigate the role of RyRs in the isoflurane-induced ER stress and caspase-3 activation.

RESULTS

Isoflurane 2% for 6 h treatment increased the levels of CHOP (876% vs 100%, P=0.00009) and caspase-12 (276% vs 100%, P=0.006), and induced caspase-3 activation in the neurones. The administration of 2% isoflurane for 3 h (shorter duration), however, only increased the levels of CHOP (309% vs 100%, P=0.003) and caspase-12 (266% vs 100%, P=0.001), without causing caspase-3 activation. The isoflurane-induced ER stress (CHOP: F=16.64, P=0.0022; caspase-12: F=6.13, P=0.0383) and caspase-3 activation (F=32.06, P=0.0005) were attenuated by the dantrolene treatment.

CONCLUSIONS

These data imply that isoflurane might induce caspase-3 activation by causing ER stress through RyRs, and dantrolene could attenuate the isoflurane-induced ER stress and caspase-3 activation. Further investigations of the potential neurotoxicity of isoflurane are needed.

Sperm retrieval from patients with nonmosaic Klinefelter's syndrome by semen cytology examination

Successful sperm retrieval from ejaculates of nonmosaic Klinefelter's syndrome (KS) patients by using semen cytology examination was described in this report. The clinical parameters of KS patients with sperm compared to patients without sperm were described. One hundred and fifty-one patients were proven to suffer from KS by chromosomal analysis using G-banding. Spermatozoa were obtained from 10 patients (10/151, 6.6%) using semen analysis. After semen cytology examination, 32 patients (32/151, 21.2%) were found to have sperm or germ cell in their ejaculate. The patients with successful sperm retrieval were significantly younger (27.1 ± 3.7 years) than the patients for whom sperm retrieval failed (28.9 ± 4.2 years). The mean serum testosterone level and the mean T/LH ratio of KS patients with successful sperm retrieval were significantly higher in men with sperm than in men without sperm (testosterone: 3.2 ± 2.1 ng/mL vs 2.7 ± 1.5 ng/mL; T/LH ratio: 0.2 ± 0.3 vs 0.1 ± 0.1). In conclusion, semen cytology examination should be performed to identify sperm and germ cells in the ejaculate of KS patients if no sperm can be detected by traditional semen analysis. The serum testosterone level and T/LH ratio revealed an association between impaired Leydig cell function and impaired spermatogenesis in KS males. KS patients should receive earlier diagnosis and treatment.

Reproductive outcomes in recurrent pregnancy loss associated with a parental carrier of chromosome abnormalities or polymorphisms

The subsequent reproductive outcomes in couples with a history of recurrent pregnancy loss (RPL) associated with chromosome abnormalities or polymorphisms are generally not reported in China. Many RPL carrier couples have decided not to have children. The present study recorded the subsequent delivery, miscarriage, and unpregnancy outcomes of 113 RPL carrier couples and 226 non-carrier couples, and compared differences in reproductive outcomes between couples with different types of chromosome abnormalities or polymorphisms and chromosome normal couples. Our results showed that couples with RPL associated with parental chromosome abnormalities or polymorphisms did not have significantly lower live birth rates than non-carrier couples in China. These results suggest the current guidance given to Chinese RPL couples.

A case of adult-onset Still's disease presenting with multifocal central serous chorioretinopathy

Adult-onset Still's disease (AOSD) is a rare systemic inflammatory disorder of unknown etiology with no specific histological features. In this study, we reported a 43-year-old woman who developed AOSD with multifocal central serous chorioretinopathy (CSC). Up to now, the patient is still on close follow-up. Besides, we reviewed the literature emphasized on the ophthalmological features of AOSD.

First Report of Meloidogyne javanica on Sacha Inchi (Plukenetia volubilis) in China

Sacha inchi (Plukenetia volubilis L.) is a plant native to the rain forest of the Peruvian Amazon region. Because of its high protein and oil content as well as general nutritional quality, it is regarded as a promising new crop. Successfully introduced from South America in 2006, Sacha inchi has been cultivated in Xishuangbanna, in the southwestern region of Yunnan Province, China. During an investigation from August to October of 2012, severely stunted and withered Sacha inchi plants with rotted and galled root were observed in fields. Dissection of galled root tissue revealed mature root-knot nematode (Meloidogyne sp) females with body cavity filled with red color contents. The population was extracted and quantified from soil and root samples and identified to species by morphology, esterase (EST) isozyme phenotypes, and molecular characterization (3). Mean populations of 774 ± 251 Meloidogyne second stage juveniles (J2) per 100 cm³ of soil were extracted from the rhizosphere of symptomatic plants. These juveniles (n = 20) were characterized by length (410 to 480 μm) and hyaline tail terminus length (11 to 17 μm). Females (n = 20) were characterized by stylet length (14.1 to 17.3 μm) and the perineal pattern (rounded with fine striae, low to moderately high dorsal arch, and a distinct lateral field clearly demarcated from striae by parallel lines). The distinct lateral lines of the perineal pattern are diagnostic for this species (3). Gravid females were used for esterase (Est) isoenzyme analysis, and showed the J3 phenotype (relative migration rate [Rm] = 1.0, 1.25, and 1.4), typical of M. javanica, a species-specific phenotype used to differentiate this species from other members of Meloidogyne (1). Additionally, three single egg masses associated with red body females were extracted from the field-collected Sacha inchi roots and inoculated onto three potted tomato plants (Solanum lycopersicum 'Rutgers') and maintained in the greenhouse for 8 weeks until root galls and egg masses were visible. The observation of root-knot nematodes from tomato roots showed that all females' bodies were normal white, and the nematode species was also identified as M. javanica based on the esterase phenotype and the perineal pattern. It is suggested that the red body contents associated with females on Sacha inchi is the result of an unknown chemical compound acquired from that host. Although undetermined to species, Meloidogyne has been reported on Sacha inchi in Peru (2). To our knowledge, this is the first detection of M. javanica on this plant. Since M. javanica is widely distributed throughout the tropics, this root-knot nematode could be an important threat to the commercial cultivation of Sacha inchi. References: (1) R. M. Carneiro et al. Nematol. 2:645, 2000. (2) P. D. P. de Bienes. Sacha inchi (Plukenetia volubilis L.). Base de datos, 2010. (3) R. N. Perry et al. Root-Knot Nematodes. CABI. Wallingford, UK, 2009.

Kinetics of serological responses in influenza A(H7N9)-infected patients correlate with clinical outcome in China, 2013

The novel avian influenza A(H7N9) infection has recently emerged to cause severe respiratory illness in China. The objectives of this study were to define the kinetics of the antibody responses in patients with influenza A(H7N9) disease and to correlate these kinetics with clinical outcome. Serial serum samples were obtained at intervals of three to four days from 18 patients with virologically confirmed A(H7N9) disease in Shanghai. We determined the kinetics of the haemagglutination inhibition (HI) and A(H7H9) pseudotype neutralisation antibody (Nab) responses and correlated these with clinical outcomes. Most patients had robust serological responses by both HI and Nab tests. Taking into account censoring due to time of testing and death, the median time from onset of illness to Nab titre ≥1:40 was 14 days (95% confidence interval (CI): 11–18 days) in the fatal cases and 10.5 days (95% CI: 7–12) in the survivors (p=0.003). The two groups did not differ in initial Nab titres, but the rate of increase in Nab titres was significantly faster for survivors by approximately 10-fold per 15 days (p=0.007). Early and rapid induction of Nab was correlated significantly with better clinical outcome.