The pathogenesis of dengue in infants is poorly understood. We postulated that dengue severity in infants would be positively associated with markers of viral burden and that maternally derived, neutralizing anti-dengue antibody would have decayed before the age at which infants with dengue presented to the hospital. In 75 Vietnamese infants with primary dengue, we found significant heterogeneity in viremia and NS1 antigenemia at hospital presentation, and these factors were independent of disease grade or continuous measures of disease severity. Neutralizing antibody titers, predicted in each infant at the time of their illness, suggested that the majority of infants (65%) experienced dengue hemorrhagic fever when the maternally derived neutralizing antibody titer had declined to <1 : 20. Collectively, these data have important implications for dengue vaccine research because they suggest that viral burden may not solely explain severe dengue in infants and that neutralizing antibody is a reasonable but not absolute marker of protective immunity in infants.

BackgroundSerological tests for IgM and IgG are routinely used in clinical laboratories for the rapid diagnosis of dengue and can differentiate between primary and secondary infections. Dengue virus non-structural protein 1 (NS1) has been identified as an early marker for acute dengue, and is typically present between days 1–9 post-onset of illness but following seroconversion it can be difficult to detect in serum.AimsTo evaluate the performance of a newly developed Panbio® Dengue Early Rapid test for NS1 and determine if it can improve diagnostic sensitivity when used in combination with a commercial IgM/IgG rapid test.MethodologyThe clinical performance of the Dengue Early Rapid was evaluated in a retrospective study in Vietnam with 198 acute laboratory-confirmed positive and 100 negative samples. The performance of the Dengue Early Rapid in combination with the IgM/IgG Rapid test was also evaluated in Malaysia with 263 laboratory-confirmed positive and 30 negative samples.Key ResultsIn Vietnam the sensitivity and specificity of the test was 69.2% (95% CI: 62.8% to 75.6%) and 96% (95% CI: 92.2% to 99.8) respectively. In Malaysia the performance was similar with 68.9% sensitivity (95% CI: 61.8% to 76.1%) and 96.7% specificity (95% CI: 82.8% to 99.9%) compared to RT-PCR. Importantly, when the Dengue Early Rapid test was used in combination with the IgM/IgG test the sensitivity increased to 93.0%. When the two tests were compared at each day post-onset of illness there was clear differentiation between the antigen and antibody markers.ConclusionsThis study highlights that using dengue NS1 antigen detection in combination with anti-glycoprotein E IgM and IgG serology can significantly increase the sensitivity of acute dengue diagnosis and extends the possible window of detection to include very early acute samples and enhances the clinical utility of rapid immunochromatographic testing for dengue.

Recovery of complex neural function after injury to the adult CNS is limited by minimal spontaneous axonal regeneration and/or sprouting from remaining pathways. In contrast, the developing CNS displays spontaneous reorganization following lesion, in which uninjured axons can develop new projections to appropriate target neurons and provide partial recovery of complex behaviours. Similar pathways can be induced in the mature CNS, providing models to optimize post-injury recovery of complex neural functions. After unilateral transection of a developing olivocerebellar path (pedunculotomy), remaining inferior olivary axons topographically reinnervate the denervated hemicerebellum and compensate functional deficits. Brain-derived neurotrophic factor (BDNF) partly recreates such reinnervation in the mature cerebellum. However the function of this incomplete reinnervation and any unwanted behavioural effects of BDNF remain unknown. We measured olivocerebellar reinnervation and tested rotarod and navigation skills in Wistar rats treated with BDNF/vehicle and pedunculotomized on day 3 (Px3; with reinnervation) or 11 (Px11; without spontaneous reinnervation). BDNF treatment did not affect motor or spatial behaviour in normal (control) animals. Px11-BDNF animals equalled controls on the rotarod, outperforming Px11-vehicle animals. Moreover, Px3-BDNF and Px11-BDNF animals achieved spatial learning and memory tasks as well as controls, with Px11-BDNF animals showing better spatial orientation than Px11-vehicle counterparts. BDNF slightly increased olivocerebellar reinnervation in Px3 animals and induced sparse (22% Purkinje cells) yet widespread reinnervation in Px11 animals. As reinnervation correlated with spatial function, these data imply that after injury even a small amount of reinnervation that is homotypic to correct target neurons compensates deficits in appropriate complex motor and spatial skills. As there was no effect in control animals, BDNF effectively induces this axon collateralisation without interfering with normal neuronal circuits.

A haemagglutination inhibition assay was used to detect antibody to psittacine beak and feather disease virus in sera from wild sulphur crested cockatoos (Cacatua galerita), galahs (Eolophus roseicapillus), short-billed corellas (Cacatua sanguinea), eastern long-billed corellas (Cacatua tenuirostris) and other psittacine birds in New South Wales. The seroprevalence of psittacine beak and feather disease ranged from 41% to 94% in different flocks, indicating infection with the virus is widespread in wild populations.

Beginning in 1994, farms in northern Australia experienced a higher than normal mortality rate in 12 to 15 g prawns from growout ponds. The farmers named this problem mid-crop mortality syndrome (MCMS). Intramuscular injection of filtered (450 nm), cell-free extracts of moribund prawns from these ponds killed healthy prawns between 5 to 30 d post-injection. A 20 nm virus was visualized by electron microscopy from a 1.4 g ml-l band recovered from caesium chloride gradients of extracts from the moribund prawns. DNA was extracted from this band, restriction enzyme digested and ligated into pGEM?zf(+) vector. A digoxigenin-labelled polymerase chain reaction (PCR)-generated, gene probe was subsequently prepared by amplifying an inserted sequence (approximately 2 kb) of one selected clone specific for the virus Specimens of the moribund prawns stained positively by in situ DNA hybridization in endodermal tissues, including the apical ends of hepatopancreatic tubules, the midgut and hindgut caecae, the midgut, and the hindgut folds. In prawns that showed haemocytic enteritis, some haemocytes in the affected midgut showed limited staining. The positivelystaining cells showed no cytolysis. In prawns injected with cell-free viral extracts, additional tissues were positive by probe analysis, including strong staining in the male reproductive tract, specifically in the terminal ampoule and the medial vas deferens. Limited staining also occurred in the ovary and in both the strornal matrix and spheroid cells of the lymphoid organ. It was evident that the infection was enteric by natural pathways and systemic by injection. Historical specimens of Penaeus monodon experimentally infected with spawner-isolated mortality virus (SMV) were probe-positive in exactly the same pattern as the naturally and experimental MCMS prawns. Altogether, the evidence suggested that the MCMS agent was a parvo-like virus very similar or identical to SMV.

PCR-dot blot detection of C psittaci in birds appears to be more sensitive than cell culture isolation in this study. C psittaci infection of birds may occur in clinically normal captive birds.

Cytokine mRNA levels were assessed in Burkholderia pseudomallei-susceptible BALB/c mice and B. pseudomallei-resistant C57BL/6 mice following administration of a sublethal dose of less virulent (LV) B. pseudomallei, a candidate immunogen tested for protection against a highly virulent (HV) challenge. Compared on the basis of the bacterial loads, the cytokine patterns induced by HV and LV B. pseudomallei were similar, involving gamma interferon, interleukin-10, and other cytokines. Partial cross-protection between B. pseudomallei strains is shown to be associated with cytokine profiles involving both type 1 and type 2 cytokines.Melioidosis is a potentially acute fulminating disease of humans and animals caused by the gram-negative intracellular bacterium Burkholderia pseudomallei (36). Infection occurs by subcutaneous inoculation of contaminated soil or surface water and can result in latent infection or a diverse range of clinical presentations (6). As recently reported by Currie et al. (8), recrudescence of disease may occur years after initial exposure, which suggests that the immune responses induced may not be effective for clearance of the organism. Differences in host and pathogen virulence factors are known to be important in determining disease severity (33). Gamma interferon (IFN-␥) plays a critical role in innate host resistance during primary infection (26), but mechanisms of adaptive immunity have not been widely studied. BALB/c mice are susceptible to infection with highly virulent (HV) B. pseudomallei, whereas C57BL/6 mice are relatively resistant (17). Cytokine responses following an HV B. pseudomallei challenge (34) are unlike those seen in other models of intracellular infection, and resistance and susceptibility do not correlate with divergent cytokine profiles commonly associated with development of distinct T helper cell subsets. Instead, early cytokine profiles are similar in BALB/c and C57BL/6 mice, with the only demonstrated difference being in the magnitude of the cytokine response (34). Responses involving a similar range of cytokines have been reported in patients (4,11,31).Characterization of less virulent (LV) strains of B. pseudomallei (12,13,35) allows us to determine their potential as candidate immunogens for induction of adaptive immunity against HV B. pseudomallei. In models of infection with other intracellular pathogens (3,5,22,27,28,29), cytokine responses are dependent upon the level of virulence of the challenge strain. The present study investigated the influence of B. pseudomallei virulence on disease progression and cytokine responses in melioidosis. Cytokine profiling of the spleen and liver was carried out by reverse transcription-PCR, and bacterial growth in the blood, liver, and spleen was determined. Immunization experiments were performed by using LV B. pseudomallei as a candidate immunogen for protection against an HV challenge to analyze the relationship between cytokine responses and immunity to B. pseudomallei.The B. pseudomallei strains used were NCTC 13178 (H...

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.