Detection of avian retroviruses in vaccines by amplification on DF-1 cells with immunostaining and fluorescent product-enhanced reverse transcriptase endpoint methods.

In order to ensure the safety of vaccines produced on avian cells, rigorous testing for the absence of avian retroviruses must be performed. Current methods used to detect avian retroviruses often exhibit a high invalid-test/false-positive rate, rely on hard-to-secure reagents, and/or have readouts that are difficult to standardize. Herein, we describe the development and validation of two consistent and sensitive methods for the detection of avian retroviruses in vaccines: viral amplification on DF-1 cells followed by immunostaining for the detection of avian leukosis virus (ALV) and viral amplification on DF-1 cells followed by fluorescent product-enhanced reverse transcriptase (F-PERT) for the detection of all avian retroviruses. Both assays share an infectivity stage on DF-1 cells followed by a different endpoint readout depending on the retrovirus to be detected. Validation studies demonstrated a limit of detection of one 50% cell culture infectious dose (CCID(50))/ml for retrovirus in a 30-ml test inoculum volume for both methods, which was as sensitive as a classical method used in the vaccine industry, namely, viral amplification on primary chicken embryo fibroblasts followed by the complement fixation test for avian leukosis virus (COFAL). Furthermore, viral amplification on DF-1 cells followed by either immunostaining or F-PERT demonstrated a sensitivity that exceeds the regulatory requirements for detection of ALV strains. A head-to-head comparison of the two endpoint methods showed that viral amplification on DF-1 cells followed by F-PERT is a suitable method to be used as a stand-alone test to ensure that vaccine preparations are free from infectious avian retroviruses.

Short communication: evaluating the level of expressed HIV type 1 gp120 and gag proteins in the vCP1521 vector by two immunoplaque methods.

Over the past few years, several recombinant ALVAC constructs have been used as delivery systems in various vaccine research studies and trials. The ALVAC-HIV vCP1521 vector has been used as a vaccine delivery system in the RV144 study, a phase III HIV study that displayed over 31% protective efficacy. One of the important parameters for evaluating the potency of an ALVAC construct is the stable expression of proteins encoded by the inserted genes. Herein, the expression of inserted gp120 and gag genes in two manufactured ALVAC-HIV vCP1521 lots have been determined by two immunoplaque methods (dish and plaque lift). Both methods were specific and robust and demonstrated that the ALVAC-HIV vCP1521 lots were able to express gp120 and gag proteins in over 99% of the infectious plaques.

The ATTCT repeats of spinocerebellar ataxia type 10 display strong nucleosome assembly which is enhanced by repeat interruptions.

Nucleosome packaging influences many aspects of DNA metabolism such as replication, repair and transcription, and via this link likely has further downstream effects on genome stability. The instability and expansion of repetitive sequences is associated with at least 42 human diseases, yet the molecular conditions contributing to repeat instability have remained largely undetermined. Previously we showed strong nucleosome formation on CAG repeats associated with spinocerebellar ataxia type 1 and very weak formation on CGG repeats associated with fragile X syndrome, and that interruption of these repeat tracts made the DNA behave more like random sequences. In this study, we determined nucleosome formation on pure and interrupted ATTCT pentanucleotides associated with spinocerebellar ataxia type 10 (SCA10). We report strong nucleosome formation on ATTCT repeats, like CAG tracts. Surprisingly, in contrast to the effect of interruptions on other repeat sequences, interruptions in the expanded ATTCT tracts further strengthened assembly with hyperacetylated histones under physiological conditions with NAP-1. These differences may contribute to phenotypic variation seen between families having pure and interrupted SCA10 repeats, as well as the overall genetic instability at the SCA10 locus.