Molecular Characterisation of Chikungunya Virus Infections in Trinidad and Comparison of Clinical and Laboratory Features with Dengue and Other Acute Febrile Cases

Local transmission of Chikungunya virus (CHIKV) was first documented in Trinidad and Tobago (T&T) in July 2014 preceding a large epidemic. At initial presentation, it is difficult to distinguish chikungunya fever (CHIKF) from other acute undifferentiated febrile illnesses (AUFIs), including life-threatening dengue disease. We characterised and compared dengue virus (DENV) and CHIKV infections in 158 patients presenting with suspected dengue fever (DF) and CHIKF at a major hospital in T&T, and performed phylogenetic analyses on CHIKV genomic sequences recovered from 8 individuals. The characteristics of patients with and without PCR-confirmed CHIKV were compared using Pearson’s χ² and student’s t-tests, and adjusted odds ratios (aORs) and 95% confidence intervals (CIs) were determined using logistic regression. We then compared signs and symptoms of people with RT-qPCR-confirmed CHIKV and DENV infections using the Mann-Whitney U, Pearson’s χ² and Fisher’s exact tests. Among the 158 persons there were 8 (6%) RT-qPCR-confirmed DENV and 30 (22%) RT-qPCR-confirmed CHIKV infections. Phylogenetic analyses showed that the CHIKV strains belonged to the Asian genotype and were most closely related to a British Virgin Islands strain isolated at the beginning of the 2013/14 outbreak in the Americas. Compared to persons who were RT-qPCR-negative for CHIKV, RT-qPCR-positive individuals were significantly more likely to have joint pain (aOR: 4.52 [95% CI: 1.28–16.00]), less likely to be interviewed at a later stage of illness (days post onset of fever—aOR: 0.56 [0.40–0.78]) and had a lower white blood cell count (aOR: 0.83 [0.71–0.96]). Among the 38 patients with RT-qPCR-confirmed CHIKV or DENV, there were no significant differences in symptomatic presentation. However when individuals with serological evidence of recent DENV or CHIKV infection were included in the analyses, there were key differences in clinical presentation between CHIKF and other AUFIs including DF, which can be used to triage patients for appropriate care in the clinical setting.     

Extended Preclinical Safety,Efficacy and Stability Testing of a Live-attenuated Chikungunya Vaccine Candidate

We recently described a new, live-attenuated vaccine candidate for chikungunya (CHIK) fever, CHIKV/IRES. This vaccine was shown to be well attenuated, immunogenic and efficacious in protecting against CHIK virus (CHIKV) challenge of mice and nonhuman primates. To further evaluate its preclinical safety, we compared CHIKV/IRES distribution and viral loads in interferon-α/β receptor-incompetent A129 mice to another CHIK vaccine candidate, 181/clone25, which proved highly immunogenic but mildly reactive in human Phase I/II clinical trials. Compared to wild-type CHIK virus, (wt-CHIKV), both vaccines generated lower viral loads in a wide variety of tissues and organs, including the brain and leg muscle, but CHIKV/IRES exhibited marked restrictions in dissemination and viral loads compared to 181/clone25, and was never found outside the blood, spleen and muscle. Unlike wt-CHIKV, which caused disrupted splenic architecture and hepatic lesions, histopathological lesions were not observed in animals infected with either vaccine strain. To examine the stability of attenuation, both vaccines were passaged 5 times intracranially in infant A129 mice, then assessed for changes in virulence by comparing parental and passaged viruses for footpad swelling, weight stability and survival after subcutaneous infection. Whereas strain 181/clone25 p5 underwent a significant increase in virulence as measured by weight loss (from <10% to >30%) and mortality (from 0 to 100%), CHIKV/IRES underwent no detectible change in any measure of virulence (no significant weight loss and no mortality). These data indicate greater nonclinical safety of the CHIKV/IRES vaccine candidate compared to 181/clone25, further supporting its eligibility for human testing.     

Improved guanide compounds which bind the CXCR4 co-receptor and inhibit HIV-1 infection

The G-protein coupled receptor CXCR4 is a co-receptor for HIV-1 infection and is involved in signaling cell migration and proliferation. In a previous study of non-peptide, guanide-based CXCR4-binding compounds, spermine and spermidine phenylguanides inhibited HIV-1 entry at low micromolar concentrations. Subsequently, crystal structures of CXCR4 were used to dock a series of naphthylguanide derivatives of the polyamines spermidine and spermine. Synthesis and evaluation of the naphthylguanide compounds identified our best compound, spermine tris-1-naphthylguanide, which bound CXCR4 with an IC₅₀ of 40 nM and inhibited the infection of TZM-bl cells with X4, but not R5, strains of HIV-1 with an IC₅₀ of 50–100 nM.     

Incomplete convergence of gliding mammal skeletons*

Ecology and biomechanics play central roles in the generation of phenotypic diversity. When unrelated taxa invade a similar ecological niche, biomechanical demands can drive convergent morphological transformations. Thus, examining convergence helps to elucidate the key catalysts of phenotypic change. Gliding mammals are often presented as a classic case of convergent evolution because they independently evolved in numerous clades, each possessing patagia (“wing” membranes) that generate lift during gliding. We use phylogenetic comparative methods to test whether the skeletal morphologies of the six clades of extant gliding mammals demonstrate convergence. Our results indicate that glider skeletons are convergent, with glider groups consistently evolving proportionally longer, more gracile limbs than arborealists, likely to increase patagial surface area. Nonetheless, we interpret gliders to represent incomplete convergence because (1) evolutionary model-fitting analyses do not indicate strong selective pressures for glider trait optima, (2) the three marsupial glider groups diverge rather than converge, and (3) the gliding groups remain separated in morphospace (rather than converging on a single morphotype), which is reflected by an unexpectedly high level of morphological disparity. That glider skeletons are morphologically diverse is further demonstrated by fossil gliders from the Mesozoic Era, which possess unique skeletal characteristics that are absent in extant gliders. Glider morphologies may be strongly influenced by factors such as body size and attachment location of patagia on the forelimb, which can vary among clades. Thus, convergence in gliders appears to be driven by a simple lengthening of the limbs, whereas additional skeletal traits reflect nuances of the gliding apparatus that are distinct among different evolutionary lineages. Our unexpected results add to growing evidence that incomplete convergence is prevalent in vertebrate clades, even among classic cases of convergence, and they highlight the importance of examining form-function relationships in light of phylogeny, biomechanics, and the fossil record.     

Effect of non-target cells on the sensitivity of the PCR for Escherichia coli O157 : H7

The fatty acid composition from mycelia of Streptomyces hygroscopicus strains was studied. A significant proportion of C_{18 : 2} was found in cultures. High levels of C_{16 : 0}, iso-C_{16 : 0} and C_{18 : 1} were also detected in all S. hygroscopicus strains. The different representatives of S. hygroscopicus had almost the same proportion of unsaturated fatty acids. Certain shifts in the amount of iso, anteiso and straight-chain fatty acids in some cultures were revealed. This might be explained by the adaptation capability of strains belonging to one species to form a variety of available fatty acids determined by particular cell membrane composition favouring certain antibiotic biosynthesis.     

Mode of action of colicin ib: formation of ion-permeable membrane channels

Addition of purified colicin Ib to whole Escherichia coli cells or cytoplasmic membrane vesicles inhibits their subsequent ability to generate a membrane potential. In addition, this colicin is shown to bring about a voltage-dependent increase in the conductance of an artificial planar bilayer membrane prepared from soybean phospholipids. This results from the formation of ion-permeable channels. These data provide strong evidence that the depolarization of Escherichia coli cells by this colicin results from an Ib-induced increase in membrane permeability to ions.