Molecular characterization of novel Adeno-associated virus variants infecting human tissues

Despite the many advantages with Adeno-associated virus (AAV) based vectors for gene therapy, certain barriers related to host permissivity and immune response precludes their widespread application in humans. A comprehensive study of the distribution and complexity of naturally occurring AAV in human tissues should facilitate their optimal utilization for gene therapy and tissue targeting in humans. A total of 205 samples, comprising 198 tissue samples from individuals of Indian origin and 7 different cell lines were investigated. A panel of 8 primate samples was used as controls. DNA from these samples was screened for the AAV capsid specific signature regions by a modified PCR and DNA sequencing approach. Further, we generated a single point mutation (S224A) in AAV3 vector, analogous to the mutation identified in a novel AAV3 sequence variant isolated from a peripheral blood stem cell (PBSC) sample. We further studied the infectivity of these vectors in HeLa and HS5 cells in vitro. Of the 205 samples analyzed, an AAV specific signature DNA sequence was detected in 92 samples (45%), including 85 out of 198 human tissues and in all the 7 human cell lines investigated. DNA sequencing analysis showed that AAV6(34%) was the most common serotype and identified predominantly in PBSCs. Interestingly, a comparative genotypic analysis in primate samples identified AAV3 specific DNA in most of the bone marrow or liver tissue analyzed (n = 7/8) suggesting species-specific differences in AAV infectivity. Further characterization of an AAV3 serotype variant isolated from the PBSCs was non-infectious in vitro, possibly due to altered receptor affinity. Our data outlines the genetic diversity and the distribution of AAV serotypes infecting humans and provides a basis for their further characterization to generate efficient gene delivery vectors.

Pelvic fractures: experience of pelvic ring fractures at a major trauma centre

In this review, we discuss the imaging classification of pelvic ring fractures in the context of our experience of reporting trauma computed tomography (CT) in a major trauma centre. Pelvic ring fractures are potentially significant injuries with risk of significant haemorrhage and morbidity. This review details the use of classification systems in determining the mechanism and severity of injury, with discussion of the features of the Young and Burgess classification system. We demonstrate the different types of pelvic ring fracture with examples from trauma CT, and with reference to the distribution and frequency of these injuries in trauma patients. This review will allow the reader to assess trauma CT for significant pelvic ring injury and identify features of instability.

Bitter sweet tympani

During cholesteatoma surgery, the chorda tympani nerve must often be divided. We present an interesting case of a patient whose severe dysgeusia due to cholesteatoma resolved following section of the chorda tympani nerve.