Identification and molecular characterization of Wolbachia strains in natural populations of Aedes albopictus in China

Background Aedes albopictus is naturally infected with Wolbachia spp., maternally transmitted bacteria that influence the reproduction of hosts. However, little is known regarding the prevalence of infection, multiple infection status, and the relationship between Wolbachia density and dengue outbreaks in different regions. Here, we assessed Wolbachia infection in natural populations of Ae. albopictus in China and compared Wolbachia density between regions with similar climates, without dengue and with either imported or local dengue. Results To explore the prevalence of Wolbachia infection, Wolbachia DNA was detected in mosquito samples via PCR amplification of the 16S rRNA gene and the surface protein gene wsp. We found that 93.36% of Ae. albopictus in China were positive for Wolbachia. After sequencing gatB, coxA, hcpA, ftsZ, fbpA and wsp genes of Wolbachia strains, we identified a new sequence type (ST) of wAlbB (464/465). Phylogenetic analysis indicated that wAlbA and wAlbB strains formed a cluster with strains from other mosquitoes in a wsp-based maximum likelihood (ML) tree. However, in a ML tree based on multilocus sequence typing (MLST), wAlbB STs (464/465) did not form a cluster with Wolbachia strains from other mosquitoes. To better understand the association between Wolbachia spp. and dengue infection, the prevalence of Wolbachia in Ae. albopictus from different regions (containing local dengue cases, imported dengue cases and no dengue cases) was determined. We found that the prevalence of Wolbachia was lower in regions with only imported dengue cases. Conclusions The natural prevalence of Wolbachia infections in China was much lower than in other countries or regions. The phylogenetic relationships among Wolbachia spp. isolated from field-collected Ae. albopictus reflected the presence of dominant and stable strains. However, wAlbB (464/465) and Wolbachia strains did not form a clade with Wolbachia strains from other mosquitoes. Moreover, lower densities of Wolbachia in regions with only imported dengue cases suggest a relationship between fluctuations in Wolbachia density in field-collected Ae. albopictus and the potential for dengue invasion into these regions.

RibonucleaseH1-targeted R-loops in surface antigen gene expression sites can direct trypanosome immune evasion

Switching of the Variant Surface Glycoprotein (VSG) inTrypanosoma bruceiprovides a crucial host immune evasion strategy that is catalysed both by transcription and recombination reactions, each operating within specialised telomeric VSG expression sites (ES). VSG switching is likely triggered by events focused on the single actively transcribed ES, from a repertoire of around 15, but the nature of such events is unclear. Here we show that RNA-DNA hybrids, called R-loops, form preferentially within sequences termed the 70 bp repeats in the actively transcribed ES, but spread throughout the active and inactive ES in the absence of RNase H1, which degrades R-loops. Loss of RNase H1 also leads to increased levels of VSG coat switching and replication-associated genome damage, some of which accumulates within the active ES. This work indicates VSG ES architecture elicits R-loop formation, and that these RNA-DNA hybrids connectT. bruceiimmune evasion by transcription and recombination.Author summaryAll pathogens must survive eradication by the host immune response in order to continue infections and be passed on to a new host. Changes in the proteins expressed on the surface of the pathogen, or on the surface of the cells the pathogen infects, is a widely used strategy to escape immune elimination. Understanding how this survival strategy, termed antigenic variation, operates in any pathogen is critical, both to understand interaction between the pathogen and host and disease progression. A key event in antigenic variation is the initiation of the change in expression of the surface protein gene, though how this occurs has been detailed in very few pathogens. Here we examine how changes in expression of the surface coat of the African trypanosome, which causes sleeping sickness disease, are initiated. We reveal that specialised nucleic acid structures, termed R-loops, form around the expressed trypanosome surface protein gene and increase in abundance after mutation of an enzyme that removes them, leading to increased changes in the surface coat in trypanosome cells that are dividing. We therefore shed light on the earliest acting events in trypanosome antigenic variation.

Incremental Contributions of FbaA and Other Impetigo-Associated Surface Proteins to Fitness and Virulence of a Classical Group A Streptococcal Skin Strain

ABSTRACT Group A streptococci (GAS) are highly prevalent human pathogens whose primary ecological niche is the superficial epithelial layers of the throat and/or skin. Many GAS strains with a strong tendency to cause pharyngitis are distinct from strains that tend to cause impetigo; thus, genetic differences between them may confer host tissue-specific virulence. In this study, the FbaA surface protein gene was found to be present in most skin specialist strains but largely absent from a genetically related subset of pharyngitis isolates. In an ΔfbaA mutant constructed in the impetigo strain Alab49, loss of FbaA resulted in a slight but significant decrease in GAS fitness in a humanized mouse model of impetigo; the ΔfbaA mutant also exhibited decreased survival in whole human blood due to phagocytosis. In assays with highly sensitive outcome measures, Alab49ΔfbaA was compared to other isogenic mutants lacking virulence genes known to be disproportionately associated with classical skin strains. FbaA and PAM (i.e., the M53 protein) had additive effects in promoting GAS survival in whole blood. The pilus adhesin tip protein Cpa promoted Alab49 survival in whole blood and appears to fully account for the antiphagocytic effect attributable to pili. The finding that numerous skin strain-associated virulence factors make slight but significant contributions to virulence underscores the incremental contributions to fitness of individual surface protein genes and the multifactorial nature of GAS-host interactions.

Three strains of Wolbachia pipientis and high rates of infection in Iranian sandfly species

Individual wild-caught sandflies from Iran were examined for infections of Wolbachia pipientis by targeting the major surface protein gene wsp of this intracellular α-proteobacterium. In total, 638 male and female sandflies were screened, of which 241 were found to be positive for one of three wsp haplotypes. Regardless of geographical origins and habitats, Phlebotomus (Phlebotomus) papatasi and other sandfly species were found to be infected with one common, widespread strain of A-group W. pipientis (Turk 54, GenBank accession EU780683; AY288297). In addition, a new A-group haplotype (Turk07, GenBank accession KC576916) was isolated from Phlebotomus (Paraphlebotomus) mongolensis and Phlebotomus (Pa.) caucasicus, and a new B-group haplotype (AZ2331, GenBank accession JX488735) was isolated from Phlebotomus (Larroussius) perfiliewi. Therefore, Wolbachia was found to occur in at least three of the incriminated vectors of zoonotic cutaneous leishmaniasis and zoonotic visceral leishmaniasis in different geographical regions of Iran. It may provide a new tool for the future control of leishmaniasis.

Serotype and surface protein gene distribution of colonizing group B streptococcus in women in Egypt

SUMMARYGroup B streptococcus (GBS) is a leading cause of neonatal sepsis and meningitis. We determined the distribution of serotypes and surface protein encoding genes of GBS strains from pregnant and non-pregnant women in Egypt. Vaginal swabs from 364 women were screened by culture and 100 (27·4%) yielded GBS. Serotype V was the most predominant (33%), followed by serotypes II (17%), III (15%), Ia (14%), VI (12%), Ib (8%) and IV (1%). The most common surface protein genes were epsilon (27%), alp3 (26%), bca (18%), rib (16%) and alp2 (10%). Two isolates were negative for surface protein genes. The distribution of serotypes and surface proteins was similar to reports from other parts of the world but the relatively high frequency of serotype VI was a notable feature of the strains from women in Egypt.