Two Chikungunya isolates from the outbreak of La Reunion (Indian Ocean) exhibit different patterns of infection in the mosquito, Aedes albopictus

Background

A Chikungunya (CHIK) outbreak hit La Réunion Island in 2005–2006. The implicated vector was Aedes albopictus. Here, we present the first study on the susceptibility of Ae. albopictus populations to sympatric CHIKV isolates from La Réunion Island and compare it to other virus/vector combinations.

Methodology and Findings

We orally infected 8 Ae. albopictus collections from La Réunion and 3 from Mayotte collected in March 2006 with two Chikungunya virus (CHIKV) from La Réunion: (i) strain 05.115 collected in June 2005 with an Alanine at the position 226 of the glycoprotein E1 and (ii) strain 06.21 collected in November 2005 with a substitution A226V. Two other CHIKV isolates and four additional mosquito strains/species were also tested. The viral titer of the infectious blood-meal was 10⁷ plaque forming units (pfu)/mL. Dissemination rates were assessed by immunofluorescent staining on head squashes of surviving females 14 days after infection. Rates were at least two times higher with CHIKV 06.21 compared to CHIKV 05.115. In addition, 10 individuals were analyzed every day by quantitative RT-PCR. Viral RNA was quantified on (i) whole females and (ii) midguts and salivary glands of infected females. When comparing profiles, CHIKV 06.21 produced nearly 2 log more viral RNA copies than CHIKV 05.115. Furthermore, females infected with CHIKV 05.115 could be divided in two categories: weakly susceptible or strongly susceptible, comparable to those infected by CHIKV 06.21. Histological analysis detected the presence of CHIKV in salivary glands two days after infection. In addition, Ae. albopictus from La Réunion was as efficient vector as Ae. aegypti and Ae. albopictus from Vietnam when infected with the CHIKV 06.21.

Conclusions

Our findings support the hypothesis that the CHIK outbreak in La Réunion Island was due to a highly competent vector Ae. albopictus which allowed an efficient replication and dissemination of CHIKV 06.21.     

The hemopexin and O-glycosylated domains tune gelatinase B/MMP-9 bioavailability via inhibition and binding to cargo receptors

Gelatinase B/matrix metalloproteinase-9 (MMP-9), a key regulator and effector of immunity, contains a C-terminal hemopexin domain preceded by a unique linker sequence of approximately 64 amino acid residues. This linker sequence is demonstrated to be an extensively O-glycosylated (OG) domain with a compact three-dimensional structure. The OG and hemopexin domains have no influence on the cleavage efficiency of MMP-9 substrates. In contrast, the hemopexin domain contains a binding site for the cargo receptor low density lipoprotein receptor-related protein-1 (LRP-1). Furthermore, megalin/LRP-2 is identified as a new functional receptor for the hemopexin domain of MMP-9, able to mediate the endocytosis and catabolism of the enzyme. The OG domain is required to correctly orient the hemopexin domain for inhibition by TIMP-1 and internalization by LRP-1 and megalin. Therefore, the OG and hemopexin domains down-regulate the bioavailability of active MMP-9 and the interactions with the cargo receptors are proposed to be the original function of hemopexin domains in MMPs.     

The crustacean hyperglycemic hormones from an euryhaline crab Pachygrapsus marmoratus and a fresh water crab Potamon ibericum: eyestalk and pericardial isoforms

The structures of crustacean hyperglycemic hormones (CHH) were investigated in two crabs, the coastal euryhaline crab Pachygrapsus marmoratus and the fresh water crab Potamon ibericum. The neuropeptide mRNAs were extracted from pericardial and X-organs (PO and XO), and the sequences of the cDNA encoding the hormones' precursors were determined. The X-organ preprohormones are composed of 29 and 28 amino acid signal peptides in P. marmoratus and P. ibericum respectively, followed by 43 and 41 amino acid crustacean hyperglycemic hormone precursor related peptide (CPRP) flanking the 72 amino acid crustacean hyperglycemic hormones. A similar organization is reported for pericardial preprohormones with identical sequences for the signal peptide, the CPRP and the N-terminal sequences of CHH (1-40), but remaining sequences (41-72 and 41-71) differing considerably. In P. marmoratus two CHH cDNAs were characterized from XO and evidences were obtained for the existence of at least two forms in the PO. From our results and by comparison with other known sequences, a consensus pattern for crab pericardial CHH could be pointed out. Analysis of the data presented in this article using phylogenetic methods reveals that the two crab species studied are much closer than previously predicted.     

Effects of various alcoholic supplements on the growth rate of Clostridium acetobutylicum ATCC 824

Summary The inhibitory effect of various alkanols, benzyl alcohol and phenethyl alcohol on the growth rate of Clostridium acetobutylicum ATCC 824 was investigated. Inhibition of cell growth was studied by treating cultures with varied concentrations of alcohols. There was a threshold concentration above which growth inhibition occurred. The degree of inhibition was a linear function of the alcohol concentration used. The natural logarithm of the inhibition constant was shown to be: (1) a linear function of the chain length of the alkanols, (2) a linear function of the natural logarithm of the octanol/water partition coefficient for both aliphatic and cyclic alcohols.     

Group B Streptococcus: global incidence and vaccine development

An ongoing public health challenge is to develop vaccines that are effective against infectious diseases that have global relevance. Vaccines against serotypes of group B Streptococcus (GBS) that are prevalent in the United States and Europe are not optimally efficacious against serotypes common to other parts of the world. New technologies and innovative approaches are being used to identify GBS antigens that overcome serotype-specificity and that could form the basis of a globally effective vaccine against this opportunistic pathogen. This Review highlights efforts towards this goal and describes a template that can be followed to develop vaccines against other bacterial pathogens.     

Double telomeric signals on single chromatids revealed by FISH and PRINS

FISH probes for all human telomeres and specific telomeric probes that hybridize to unique sequences on individual chromosomes have been used to characterize the telomeric hybridization pattern of human peripheral blood lymphocytes and bone-marrow cells in interphase and metaphase chromosomes. We have identified the existence of double hybridization signals on chromatids both with the (TTAGGG)n telomere repeat arrays and on non chromosome-specific subtelomeric regions as well as on chromosome-specific sequences located several kilobases from the end of chromosomes. Preliminary results using cosmid or YAC probes that hybridize to regions rich in GC sequences also revealed double fluorescent spots on a single chromatid. Double spots were detected by PRINS on terminal and interstitial telomeric sequences in avian cells. The significance of this phenomenon is discussed based on some models of chromatid and DNA organization such as uninemy, looped chromatid organization and quartet DNA structures. The occurrence of double spots should be taken into consideration for the clinical cytogenetic diagnosis of duplications.     

Dissection of the unusual structural and functional properties of the variant H2A.Bbd nucleosome

The histone variant H2A.Bbd appeared to be associated with active chromatin, but how it functions is unknown. We have dissected the properties of nucleosome containing H2A.Bbd. Atomic force microscopy (AFM) and electron cryo-microscopy (cryo-EM) showed that the H2A.Bbd histone octamer organizes only approximately 130 bp of DNA, suggesting that 10 bp of each end of nucleosomal DNA are released from the octamer. In agreement with this, the entry/exit angle of the nucleosomal DNA ends formed an angle close to 180 degrees and the physico-chemical analysis pointed to a lower stability of the variant particle. Reconstitution of nucleosomes with swapped-tail mutants demonstrated that the N-terminus of H2A.Bbd has no impact on the nucleosome properties. AFM, cryo-EM and chromatin remodeling experiments showed that the overall structure and stability of the particle, but not its property to interfere with the SWI/SNF induced remodeling, were determined to a considerable extent by the H2A.Bbd docking domain. These data show that the whole H2A.Bbd histone fold domain is responsible for the unusual properties of the H2A.Bbd nucleosome.     

Involvement of pyruvate oxidase activity and acetate production in the survival of Lactobacillus plantarum during the stationary phase of aerobic growth

In addition to the previously characterized pyruvate oxidase PoxB, the Lactobacillus plantarum genome encodes four predicted pyruvate oxidases (PoxC, PoxD, PoxE, and PoxF). Each pyruvate oxidase gene was individually inactivated, and only the knockout of poxF resulted in a decrease in pyruvate oxidase activity under the tested conditions. We show here that L. plantarum has two major pyruvate oxidases: PoxB and PoxF. Both are involved in lactate-to-acetate conversion in the early stationary phase of aerobic growth and are regulated by carbon catabolite repression. A strain devoid of pyruvate oxidase activity was constructed by knocking out the poxB and poxF genes. In this mutant, acetate production was strongly affected, with lactate remaining the major end product of either glucose or maltose fermentation. Notably, survival during the stationary phase appeared to be dramatically improved in the poxB poxF double mutant.     

Molecular evolution and circulation patterns of human respiratory syncytial virus subgroup a: positively selected sites in the attachment g glycoprotein

Human respiratory syncytial virus (HRSV) is the most common etiological agent of acute lower respiratory tract disease in infants and can cause repeated infections throughout life. In this study, we have analyzed nucleotide sequences encompassing 629 bp at the carboxy terminus of the G glycoprotein gene for HRSV subgroup A strains isolated over 47 years, including 112 Belgian strains isolated over 19 consecutive years (1984 to 2002). By using a maximum likelihood method, we have tested the presence of diversifying selection and identified 13 positively selected sites with a posterior probability above 0.5. The sites under positive selection correspond to sites of O glycosylation or to amino acids that were previously described as monoclonal antibody-induced in vitro escape mutants. Our findings suggest that the evolution of subgroup A HRSV G glycoprotein is driven by immune pressure operating in certain codon positions located mainly in the second hypervariable region of the ectodomain. Phylogenetic analysis revealed the prolonged cocirculation of two subgroup A lineages among the Belgian population and the possible extinction of three other lineages. The evolutionary rate of HRSV subgroup A isolates was estimated to be 1.83 x 10(-3) nucleotide substitutions/site/year, projecting the most recent common ancestor back to the early 1940s.