The Cross-Border Biotech Blog

Host-Cell Nucleolin, A Helping Hand for RSV

University of British Columbia ♦ University of Toronto ♦ Published in Nature Medicine, August 14th, 2011

Human respiratory syncytial virus (RSV), a Pneumovirus that is widely responsible for respiratory tract infections worldwide, appears to use host-cell nucleolin for viral entry. After making the discovery, researchers corroborated their finding with several experiments to show the importance that nucleolin plays in RSV infection. Neutralization experiments with nucleolin antibodies in vitro decreased RSV infection, while competition experiments with soluble nucleolin placed in cell culture medium also inhibited the virus from passing into cells. Interestingly, insect cells that are typically immune to the virus could be made susceptible through the transfection of human nucleolin. Mice given a prophylactic dose of RNAi, knocking down nucleolin in the lung, exhibited significant reduction in RSV infection. RSV interacts with host-cell nucleolin with a glycoprotein found in the viral envelope. There is currently no effective therapeutic or vaccination for the virus. Palivizumab (manufactured by MedImmune) is available for patients considered to be at high risk, but remains expensive.

Calpain-Mediated Degradation Spurs Autoimmune Disease

University of Toronto ♦ Samuel Lunenfeld Research Institute ♦ Toronto General Research Institute ♦ Princess Margaret Hospital ♦ Others..

Published in Nature Genetics, August 14th, 2011

The human Lyp protein tyrosine phosphatase (Lyp620W) plays a critical role in immune homeostasis by regulating T-cell antigen receptor signaling. A mutant of Lyp620W, Pep619W, is associated with increased risk of autoimmune disease. The mechanism by which this mutation promotes autoimmune disease is largely unknown. Recent findings suggest that degradation of Lyp protein is at the root of immune dysfunction. When analyzing Lyp transcripts in both wild-type mice and mice containing mutant alleles of the gene encoding Lyp620W, researchers found that transcript levels remained the same despite mutation. However, in the case of mice homozygous for the mutant allele, there was a drastic reduction in Pep619W protein. It appears that the enzyme calpain-1 degrades mutant versions of the protein, preventing Lyp protein from regulating the immune system. In the absence of functioning Lyp620W, lymphocyte and dendritic cell hyperresponsiveness ensues, leading to deleterious disease conditions.

Also see this review (written by U of T researchers and published in Trends in Biotechnology) on the use of biomaterials to create supportive micro-environments for the transplantation of neural stem/progenitor cells into the central nervous system..

Acquisition of Animal Gene by Horizontal Transfer

University of Ottawa ♦ University of British Columbia ♦ University of Illinois ♦ Albert Einstein College of Medicine

Published in Current Biology (Cell Press), August 9, 2011

Researchers have recently made a rather surprising discovery — an animal gene that appears to have been taken up by the microsporidian Encephalitozoon romaleae. This is the first time that an animal gene has been documented in a microsporidian genome. Microsporidians often parasitise arthropods, and have been known to take up foreign DNA from bacteria through a process known as horizontal gene transfer. New DNA allows microsporidians to gain new functions that promote survival. After carrying out a screen of the microsporidian genome they found but one candidate animal gene, which was identified as a purine nucleotide phosphorylase (PNP). Phylogenetic analysis later revealed that the gene was likely of arthropod origin and could have been taken up by E. romaleae after it parasitised an insect.

Genetics Underpinning ALS

University of Montreal ♦ Published in PLoS Genetics, August 4, 2011

Using the zebrafish as a model, researchers have elucidated the connection between some of the common mutations associated with amyotrophic lateral sclerosis (ALS). Mutations in the genes SOD1 and TARDBP have been known to cause ALS, as has a mutation in the Fused in sarcoma gene (FUS). In this study researchers show that mutations in the FUS gene cause a loss of function; they cannot rescue the motor phenotype caused by a knockdown of the zebrafish Fus gene. It seems that the FUS and TARDBP mutations share a common pathogenic mechanism, as there co-expression did not exacerbate the phenotype observed when either were expressed alone. Findings indicate that SOD1 works through a second distinct mechanism however, as wildtype SOD1 was unable to rescue the phenotype observed after overexpression of FUS and TARDBP mutations.

Balancing Host Defense and Wound Repair

University of Toronto ♦ Hospital for Sick Children ♦ Benaroya Research Institute ♦ University Hospital Erlangen

Published in Immunity (Cell Press), August 3, 2011

Tak Mak’s lab provides some new insights into the mechanism by which thymic stromal lymphopoietin (TSLP) modulates the immune system in order to curb inflammation and launch the healing process in the colon. Using a knockout mouse model researchers illustrate that the absence of TSLP does not increase the severity of colitis, but instead prevents healing and recovery from the disease. Mice without the TSLP gene exhibited increased concentrations of an enzyme known as neutrophil elastase and decreased expression of secretory leukocyte peptidase inhibitor (SLPI). Typically SLPI serves to stomp out some of the immune response following insult to the colon by acting as a serine protease inhibitor and inhibitor of NF-κB. In the absence of TLSP signaling, however, it seems SLPI is downregulated, preventing mucosal healing.

High-Throughput Platform for Single-Cell qPCR

University of British Columbia ♦ BC Cancer Agency ♦ Centre for Translational and Applied Genomics

Published in PNAS, August 1st, 2011

An achievement in microfluidics this week as researchers from the University of British Columbia report on the development of an integrated microfluidics device that performs high-throughput mRNA analysis on a chip. The platform is capable of analyzing hundreds of single cells per run, and operates on a nanolitre scale, offering very high sensitivity. The goal of advanced microfluidics systems for single cell analysis has been to incorporate each step of the process into seamless automation. Although current devices provide the necessary high-throughput qPCR readout, they require micropipettes or cell-sorting to trap cells for analysis on the front-end. This novel device does it all, and is the first example of a fully integrated platform for single-cell qPCR on a chip. Among the other advantages of this platform are improved performance, reduced cost, and scalability.

Melarsoprol Exacerbates HIV-1 Infection

Laval University ♦ Sherbrooke University ♦ Published in Journal of Molecular Biology, July 29th, 2011

Recent findings suggest that melarsoprol, a drug commonly used to treat sleeping sickness in Africa, improves the HIV virus’ ability to replicate in human cells. Due to the fact that Trypanosoma brucei infections are often seen along with HIV-1 infection, researchers were curious to investigate potential interactions between the two pathogens. In doing so they found that melarsoprol can stimulate the replication of several strains of HIV-1 in dendritic cells. These findings raise concerns for patients receiving the drug because it can exacerbate disease conditions and may have implications on disease transmission. Melarsoprol seems to boost HIV replication by inhibiting a certain cellular restriction factor, which under normal circumstances exerts a slightly antagonistic effect on the HIV reverse transcription process.

Recombinant BCL-X Enhances Pre-Implantation Embryo Development

University of Toronto ♦ Mount Sinai Hospital ♦ Washington University in St. Louis

Published in PLoS ONE, July 20th, 2011

More automation this week with the introduction of a fully-automated robotic system for high-throughput microinjection of pre-implantation embryos. Infertility is on the rise, and as more and more couples require the services of IVF doctors, there is more demand for treatment options that can continue to increase the success of IVF in the clinic. This new system combines motion control, computer vision microscopy, and micro device technology to accurately and efficiently deliver small quantities of recombinant material. Researchers injected the anti-apoptic agent BCL-X into mouse zygotes, and found that they could enhance the viability and pre-implantation development of mouse embryos grown in sub-optimal in vitro conditions. The system could offer a new treatment paradigm for couples experiencing difficulty with IVF.