A new DNA binding protein highly conserved in diverse crenarchaeal viruses

Sulfolobus turreted icosahedral virus (STIV) infects Sulfolobus species found in the hot springs of Yellowstone National Park. Its 37 open reading frames (ORFs) generally lack sequence similarity to other genes. One exception, however, is ORF B116. While its function is unknown, orthologs are found in three additional crenarchaeal viral families. Due to the central importance of this protein family to crenarchaeal viruses, we have undertaken structural and biochemical studies of B116. The structure reveals a previously unobserved fold consisting of a five-stranded beta-sheet flanked on one side by three alpha helices. Two subunits come together to form a homodimer with a 10-stranded mixed beta-sheet, where the topology of the central strands resembles an unclosed beta-barrel. Highly conserved loops rise above the surface of the saddle-shaped protein and suggest an interaction with the major groove of DNA. The predicted B116-DNA interaction is confirmed by electrophoretic mobility shift assays.     

A winged-helix protein from Sulfolobus turreted icosahedral virus points toward stabilizing disulfide bonds in the intracellular proteins of a hyperthermophilic virus

Sulfolobus turreted icosahedral virus (STIV) was the first non-tailed icosahedral virus to be isolated from an archaeal host. Like other archaeal viruses, its 37 open reading frames generally lack sequence similarity to genes with known function. The roles of the gene products in this and other archaeal viruses are thus largely unknown. However, a protein's three-dimensional structure may provide functional and evolutionary insight in cases of minimal sequence similarity. In this vein, the structure of STIV F93 reveals a homodimer with strong similarity to the winged-helix family of DNA-binding proteins. Importantly, an interchain disulfide bond is found at the dimer interface, prompting analysis of the cysteine distribution in the putative intracellular proteins of the viral proteome. The analysis suggests that intracellular disulfide bonds are common in cellular STIV proteins, where they enhance the thermostability of the viral proteome.     

Evaluation of a loop-mediated isothermal amplification assay for rapid diagnosis of soft-shelled turtle iridovirus

Softshelled turtle iridovirus (STIV) is the first Asian iridovirus isolated from reptiles, which infects soft-shelled turtles severely and leads to “Red neck disease” associated with high mortality. A set of four specific primers was designed by targeting the STIV Thymidine kinase (TK) gene and amplified STIV DNA specifically under optimized amplification conditions at 63 °C for 60 min. The sensitivity of the loop-mediated isothermal amplification (LAMP) assay was found to be 20 copies/μl of STIV DNA. To evaluate the application of the LAMP assay for detection of STIV in clinical samples, 223 samples suspected of STIV infection from turtle tissues were tested by the LAMP assay and by cell-based virus isolation. A 78.5% concordance was observed between the results of the two methods. In this study, a robust and simple LAMP assay for rapid detection of STIV was developed and evaluated, which is the first suitable for potential diagnosis and helping to monitor STIV infections in the aquaculture industry.     

Development of a genetic system for the archaeal virus Sulfolobus turreted icosahedral virus (STIV)

Our understanding of archaeal viruses has been limited by the lack of genetic systems for examining viral function. We describe the construction of an infectious clone for the archaeal virus Sulfolobus turreted icosahedral virus (STIV). STIV was isolated from a high temperature (82 °C) acidic (pH 2.2) hot spring in Yellowstone National Park and replicates in the archaeal model organism Sulfolobus solfataricus (Rice et al., 2004). While STIV is one of most studied archaeal viruses, little is known about its replication cycle. The development of an STIV infectious clone allows for directed gene disruptions and detailed genetic analysis of the virus. The utility of the STIV infectious clone was demonstrated by gene disruption of STIV open reading frame (ORF) B116 which resulted in crippled virus replication, while disruption of ORFs A197, C381 and B345 was lethal for virus replication.     

Parental perspectives of vaccine safety and experience of adverse events following immunisation

Introduction

We aimed to determine demographic predictors of parental vaccine safety and risk perceptions, and assess the relationship between the occurrence of children's perceived adverse events following immunisation (AEFI) on parents’ opinions.

Methods

Computer-assisted telephone interviews (CATI) were conducted in 2011 with a cross-sectional, random general population sample of rural and metropolitan residents in South Australia. Multivariate ordinal logistic regression analyses examined associations between parental vaccine safety attitudes and socio-demographic factors, adjusting for whether children had ever experienced a previous suspected AEFI.

Results

Of 469 parents interviewed, 95% were confident in vaccine safety in general, but almost half expressed concern for pre-licensure testing of vaccines. Of all parents, 41% responded that at least one of their children had experienced an AEFI. Almost one third of the AEFI parent group indicated they reported their children's symptoms to either a healthcare professional or the Department of Health. Parental acceptability of the risks of febrile convulsion and anaphylaxis were 73% and 76% respectively. Ordinal logistic regression analyses showed parents of children who had experienced a suspected AEFI were associated with greater concern for vaccine safety (OR:0.53, p ≤ 0.01) and more were likely to expect either a mild or a serious AEFI. After adjusting for demographics, parental confidence in vaccine safety was significantly associated with higher levels of education (OR:2.58, p = 0.01) and being born in Australia OR:2.30, p = 0.004. Mothers, when compared with fathers, were less accepting of the two vaccine risks presented: febrile convulsion (OR:0.57, p = 0.04) and anaphylaxis, (OR:0.55, p = 0.04).

Conclusions

Parents commonly perceive and report that their child has experienced an AEFI. In this group of parents the subsequent expectation of an AEFI and vaccine safety concerns may be heightened. Further research should investigate parental understandings of differentiating an expected event from an adverse event as this could inform immunization risk communication and consumer AEFI reporting strategies.     

Salmonella Typhi outer membrane protein STIV is a potential candidate for vaccine development against typhoid and paratyphoid fever

Enteric fever, caused by Salmonella enterica serovars, Typhi (S. Typhi) and Paratyphi (S. Paratyphi) is a major public health challenge for the developing nations. Globally, the disease affects ˜15-30 million individuals every year, resulting in >200,000 deaths. Multidrug-resistant S. Typhi H58 strain has emerged as the dominant circulating strain in a large part of the world and an extensively drug-resistant (XDR) subclade of the strain was recently reported. Many believe that vaccination of the susceptible populations is urgently needed and the best option to control the infection. However, the commercial live attenuated (Ty21a) vaccine is not recommended for children below six years of age while the Vi-polysaccharide-based vaccine has poor long-term efficacy against typhoid fever. Moreover, no vaccines are available against S. Paratyphi infection. Thus, a new formulation capable of providing long term protection against both the pathogens and safe for all age groups is immediately required. We show that recombinant, S. Typhi outer membrane protein STIV (rSTIV) is immunogenic in mice and elicits high serum titers of different immunoglobulin subtypes. STIV antibodies opsonize S. Typhi and S. Paratyphi A to promote antibody-dependent cellular cytotoxicity and complement-mediated lysis. Immunization with rSTIV also induces robust cell-mediated immunity, including antigen-specific T cell proliferation and cytotoxic T lymphocyte response. Finally, mice immunized with rSTIV are significantly protected against S. Typhi and S. Paratyphi A challenge, with reduced visceral bacterial load. Our results underscore the potential of rSTIV as a novel vaccine candidate for enteric fever.