Virulence difference between the prototypic Schu S4 strain (A1a) and Francisella tularensisA1a, A1b, A2 and type B strains in a murine model of infection

BACKGROUND: The use of prototypic strains is common among laboratories studying infectious agents as it promotes consistency for data comparability among and between laboratories. Schu S(4) is the prototypic virulent strain of Francisella tularensis and has been used extensively as such over the past six decades. Studies have demonstrated virulence differences among the two clinically relevant subspecies of F. tularensis, tularensis (type A) and holarctica (type B) and more recently between type A subpopulations (A1a, A1b and A2). Schu S(4) belongs to the most virulent subspecies of F. tularensis, subspecies tularensis. METHODS: In this study, we investigated the relative virulence of Schu S(4) in comparison to A1a, A1b, A2 and type B strains using a temperature-based murine model of infection. Mice were inoculated intradermally and a hypothermic drop point was used as a surrogate for death. Survival curves and the length of temperature phases were compared for all infections. Bacterial burdens were also compared between the most virulent type A subpopulation, A1b, and Schu S(4) at drop point. RESULTS: Survival curve comparisons demonstrate that the Schu S(4) strain used in this study resembles the virulence of type B strains, and is significantly less virulent than all other type A (A1a, A1b and A2) strains tested. Additionally, when bacterial burdens were compared between mice infected with Schu S(4) or MA00-2987 (A1b) significantly higher burdens were present in the blood and spleen of mice infected with MA00-2987. CONCLUSIONS: The knowledge gained from using Schu S(4) as a prototypic virulent strain has unquestionably advanced the field of tularemia research. The findings of this study, however, indicate that careful consideration of F. tularensis strain selection must occur when the overall virulence of the strain used could impact the outcome and interpretation of results

Humoral Immune Responses of Dengue Fever Patients Using Epitope-Specific Serotype-2 Virus-Like Particle Antigens

Dengue virus (DENV) is a serious mosquito-borne pathogen causing significant global disease burden, either as classic dengue fever (DF) or in its most severe manifestation dengue hemorrhagic fever (DHF). Nearly half of the world's population is at risk of dengue disease and there are estimated to be millions of infections annually; a situation which will continue to worsen with increasing expansion of the mosquito vectors and epidemic DF/DHF. Currently there are no available licensed vaccines or antivirals for dengue, although significant effort has been directed toward the development of safe and efficacious dengue vaccines for over 30 years. Promising vaccine candidates are in development and testing phases, but a better understanding of immune responses to DENV infection and vaccination is needed. Humoral immune responses to DENV infection are complex and may exacerbate pathogenicity, yet are essential for immune protection. In this report, we develop DENV-2 envelope (E) protein epitope-specific antigens and measure immunoglobulin responses to three distinct epitopes in DENV-2 infected human serum samples. Immunoglobulin responses to DENV-2 infection exhibited significant levels of individual variation. Antibody populations targeting broadly cross-reactive epitopes centered on the fusion peptide in structural domain II were large, highly variable, and greater in primary than in secondary DENV-2 infected sera. E protein domain III cross-reactive immunoglobulin populations were similarly variable and much larger in IgM than in IgG. DENV-2 specific domain III IgG formed a very small proportion of the antibody response yet was significantly correlated with DENV-2 neutralization, suggesting that the highly protective IgG recognizing this epitope in murine studies plays a role in humans as well. This report begins to tease apart complex humoral immune responses to DENV infection and is thus important for improving our understanding of dengue disease and immunological correlates of protection, relevant to DENV vaccine development and testing

The pathophysiology of restricted repetitive behavior

Restricted, repetitive behaviors (RRBs) are heterogeneous ranging from stereotypic body movements to rituals to restricted interests. RRBs are most strongly associated with autism but occur in a number of other clinical disorders as well as in typical development. There does not seem to be a category of RRB that is unique or specific to autism and RRB does not seem to be robustly correlated with specific cognitive, sensory or motor abnormalities in autism. Despite its clinical significance, little is known about the pathophysiology of RRB. Both clinical and animal models studies link repetitive behaviors to genetic mutations and a number of specific genetic syndromes have RRBs as part of the clinical phenotype. Genetic risk factors may interact with experiential factors resulting in the extremes in repetitive behavior phenotypic expression that characterize autism. Few studies of individuals with autism have correlated MRI findings and RRBs and no attempt has been made to associate RRB and post-mortem tissue findings. Available clinical and animal models data indicate functional and structural alterations in cortical-basal ganglia circuitry in the expression of RRB, however. Our own studies point to reduced activity of the indirect basal ganglia pathway being associated with high levels of repetitive behavior in an animal model. These findings, if generalizable, suggest specific therapeutic targets. These, and perhaps other, perturbations to cortical basal ganglia circuitry are mediated by specific molecular mechanisms (e.g., altered gene expression) that result in long-term, experience-dependent neuroadaptations that initiate and maintain repetitive behavior. A great deal more research is needed to uncover such mechanisms. Work in areas such as substance abuse, OCD, Tourette syndrome, Parkinson’s disease, and dementias promise to provide findings critical for identifying neurobiological mechanisms relevant to RRB in autism. Moreover, basic research in areas such as birdsong, habit formation, and procedural learning may provide additional, much needed clues. Understanding the pathophysioloy of repetitive behavior will be critical to identifying novel therapeutic targets and strategies for individuals with autism

Guillain–Barré syndrome risk among individuals infected with Zika virus: a multi-country assessment

Abstract Background Countries with ongoing outbreaks of Zika virus have observed a notable rise in reported cases of Guillain–Barré syndrome (GBS), with mounting evidence of a causal link between Zika virus infection and the neurological syndrome. However, the risk of GBS following a Zika virus infection is not well characterized. In this work, we used data from 11 locations with publicly available data to estimate the risk of GBS following an infection with Zika virus, as well as the location-specific incidence of infection and the number of suspect GBS cases reported per infection. Methods We built a mathematical inference framework utilizing data from 11 locations that had reported suspect Zika and GBS cases, two with completed outbreaks prior to 2015 (French Polynesia and Yap) and nine others in the Americas covering partial outbreaks and where transmission was ongoing as of early 2017. Results We estimated that 2.0 (95% credible interval 0.5–4.5) reported GBS cases may occur per 10,000 Zika virus infections. The frequency of reported suspect Zika cases varied substantially and was highly uncertain, with a mean of 0.11 (95% credible interval 0.01–0.24) suspect cases reported per infection. Conclusions These estimates can help efforts to prepare for the GBS cases that may occur during Zika epidemics and highlight the need to better understand the relationship between infection and the reported incidence of clinical disease

Envelope protein structural domain III (EDIII) alignment of representative strains of the four dengue virus (DENV) serotypes and Japanese encephalitis virus (JEV).

<p>Single letter amino acid abbreviations are shown for EDIII of DENV-2 using DENV-2 numbering (the last digit of the residue number lies directly above the numbered residue). Amino acids conserved relative to DENV-2 in the other serotypes are shown as dots, alignment gaps are depicted with dashes, and single letter abbreviations for non-conserved amino acids are shown. Colored residues in the DENV-2 sequence depict epitope-specific determinates as determined in this report and previously published reports. DENV complex and subcomplex cross-reactive epitopes are highlighted in yellow, DENV-2 specific residues are highlighted in red, and residues from the region of overlap between these epitopes (hence affecting DENV complex and DENV-2 virus specific epitopes) are highlighted green <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004991#pone.0004991-SukupolviPetty1" target="_blank">[22]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004991#pone.0004991-Gromowski1" target="_blank">[23]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004991#pone.0004991-Gromowski2" target="_blank">[24]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004991#pone.0004991-Lok1" target="_blank">[47]</a>. The substituted EDIII residues incorporated into mutant antigens in this study are marked in black for the non DENV-2 viruses: DENV EDIII complex cross-reactive knock out mutants incorporated K310D, E311R, P364R, and K388D; K305E was utilized to determine EDIII DENV-2 specific immunoglobulin responses.</p

Envelope protein domain III DENV-2 specific (EDIII_TS) IgG is positively and significantly correlated with DENV-2 neutralization.

<p>Log10 EDIII_TS IgM and IgG regressed on Log10 DENV-2 specific 90% neutralization endpoint titers. (A) EDIII_TS IgM titer is not associated with DENV-2 specific 90% neutralization titers (m = −0.163, p = 0.656), P value was determined by performing an analysis of variance on the slope of the regression. (B) EDIII_TS IgG is positively and significantly associated with increasing DENV-2 specific 90% Neutralization titers (m = 1.036, p = 0.0149), P value determined as in A.</p

Nucleotide sequences of mutagenic primers used and % VLP secretion from resultant plasmids relative to wild-type (100%).

1<p>Mutated nucleotides are shown in bold.</p>2<p>Average of triplicate experiments of mutant VLP secretion from transiently transformed COS-1 cells, standardized against the wild-type DENV-2 plasmid VLP secretion.</p

Virus neutralization titers for primary DENV-2 infected serum samples from dengue fever patients.

1<p>days post onset of symptoms.</p>2<p>Last positive titer in 90% Focus-reduction micro-neutralization (FRμNT) assay.</p>3<p>Calculated actual 90% neutralization titers based on a nonlinear regression of the FRμNT data using a variable slope sigmoidal dose-response model.</p

Structural locations of envelope (E) protein epitope-specific knock-out substitutions.

<p>(A) Crystal structure of the DENV-2 E protein dimer <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004991#pone.0004991-Modis1" target="_blank">[15]</a> as it appears from above in mature virions and depicted as a ribbon diagram. The structural domains are colored red (EDI), yellow (EDII), and blue (EDIII). The highly conserved fusion peptide, located at the distal end of EDII is colored green and the glycans in EDI (N153) and EDII (N67) are depicted as ball and stick representation and colored brown. Epitope specific knock-out substitutions in the fusion peptide and in EDIII are depicted as space filling representations. (B) Side view of the same representation of the E protein dimer in mature virions with all structural depictions and colors the same as in panel A. (C) An enlarged view from panel B of the interface between the EDII fusion peptide of one E monomer and EDIII of the alternate monomer of the E dimer. EDII fusion peptide (EDII_FP), EDIII cross-reactive (EDIII_CR), and EDIII DENV-2 serotype specific (EDIII_TS) antigenic regions are noted and encircled. Residues locations of epitope-specific knock out substitutions utilized in this study are depicted as ball and stick representations. Substitutions of Gly106 and Leu107 in the EDII fusion peptide knock out the binding of broadly cross-reactive immunoglobulins, those recognizing viruses in the DENV complex and other flavivirus complexes. Substitutions of Lys310, Glu311, Pro364, and Lys388 in EDIII knock out the binding of immunoglobulins recognizing all or subsets of the four serotypes of DENV, but do not interfere with DENV-2 specific immunoglobulin recognition. Substitutions of Lys305 knock out the binding of DENV-2 serotype specific MAbs.</p