Assessing production variability in empty and filled adeno-associated viruses by single molecule mass analyses

Adeno-associated viruses (AAVs) are useful vehicles for gene therapy because of their stability, low immunogenicity. and non-pathogenicity. However, disparity in AAV sample preparations (e.g., in capsid composition, DNA packaging, and impurities) gives rise to product heterogeneity, with possibly undesired effects on gene delivery. Ideally, AAV production should be with full control of AAV structure and genetic payload. Therefore, robust, efficient, and low material consuming methods are essential to characterize AAVs. Here, we use two emerging single-molecule techniques, mass photometry and Orbitrap-based charge-detection mass spectrometry, and show how they may efficiently and accurately characterize AAVs. We were able to resolve heterogeneous pools of particles, evaluating AAVs from two different serotypes (AAV8 and AAV2), produced by three independent production platforms, either lacking a genome or packed with a transgene. Together our data confirm that the different AAV production methods result in rather different and diverse AAV particle distributions. Especially for the packed AAVs, frequently additional subspecies were observed, next to the expected packed genome, mostly resulting from under- or overpackaging of genome material and/or residual empty particles. This work further establishes that both these single-particle techniques may become valuable tools in characterizing AAVs before they are used in gene therapy

Absence of Donor-Specific Anti-HLA Antibodies After ABO-Incompatible Heart Transplantation in Infancy: Altered Immunity or Age?

Specific B-cell tolerance toward donor blood group antigens develops in infants after ABO-incompatible heart transplantation, whereas their immune response toward protein antigens such as HLA has not been investigated. We assessed de novo HLA-antibodies in 122 patients after pediatric thoracic transplantation (28 ABO-incompatible) and 36 controls. Median age at transplantation was 1.7 years (1 day to 17.8 year) and samples were collected at median 3.48 years after transplantation. Antibodies were detected against HLA-class I in 21 patients (17.2%), class II in 18 (14.8%) and against both classes in 10 (8.2%). Using single-antigen beads, donor-specific antibodies (DSAs) were identified in six patients (all class II, one additional class I). Patients with DSAs were significantly older at time of transplantation. In patients who had undergone pretransplant cardiac surgeries, class II antibodies were more frequent, although use of homografts or mechanical heart support had no influence. DSAs were absent in ABO-incompatible recipients and class II antibodies were significantly less frequent than in children with ABO-compatible transplants. This difference was present also when comparing only children transplanted below 2 years of age. Therefore, tolerance toward the donor blood group appears to be associated with an altered response to HLA beyond age-related effects.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78721/1/j.1600-6143.2009.02877.x.pd

Wall teichoic acid structure governs horizontal gene transfer between major bacterial pathogens

Mobile genetic elements (MGEs) encoding virulence and resistance genes are widespread in bacterial pathogens, but it has remained unclear how they occasionally jump to new host species. Staphylococcus aureus clones exchange MGEs such as S. aureus pathogenicity islands (SaPIs) with high frequency via helper phages. Here we report that the S. aureus ST395 lineage is refractory to horizontal gene transfer (HGT) with typical S. aureus but exchanges SaPIs with other species and genera including Staphylococcus epidermidis and Listeria monocytogenes. ST395 produces an unusual wall teichoic acid (WTA) resembling that of its HGT partner species. Notably, distantly related bacterial species and genera undergo efficient HGT with typical S. aureus upon ectopic expression of S. aureus WTA. Combined with genomic analyses, these results indicate that a ‘glycocode’ of WTA structures and WTA-binding helper phages permits HGT even across long phylogenetic distances thereby shaping the evolution of Gram-positive pathogens

Inhibition of Rac1 signaling by lovastatin protects against anthracycline-induced cardiac toxicity

Normal tissue damage limits the efficacy of anticancer therapy. For anthracyclines, the clinically most relevant adverse effect is cardiotoxicity. The mechanisms involved are poorly understood and putative cardioprotectants are controversially discussed. Here, we show that the lipid-lowering drug lovastatin protects rat H9c2 cardiomyoblasts from doxorubicin in vitro. Protection by lovastatin is related to inhibition of the Ras-homologous GTPase Rac1. It rests on a reduced formation of DNA double-strand breaks, resulting from the inhibition of topoisomerase II by doxorubicin. Doxorubicin transport and reactive oxygen species are not involved. Protection by lovastatin was confirmed in vivo. In mice, lovastatin mitigated acute doxorubicin-induced heart and liver damage as indicated by reduced mRNA levels of the pro-fibrotic cytokine connective tissue growth factor (CTGF) and pro-inflammatory cytokines, respectively. Lovastatin also protected from doxorubicin-provoked subacute cardiac damage as shown by lowered mRNA levels of CTGF and atrial natriuretic peptide. Increase in the serum concentration of troponin I and cardiac fibrosis following doxorubicin treatment were also reduced by lovastatin. Whereas protecting the heart from harmful doxorubicin effects, lovastatin augmented its anticancer efficacy in a mouse xenograft model with human sarcoma cells. These data show that statins lower the incidence of cardiac tissue injury after anthracycline treatment in a Rac1-dependent manner, without impairing the therapeutic efficacy

Assessing production variability in empty and filled adeno-associated viruses by single molecule mass analyses

Adeno-associated viruses (AAVs) are useful vehicles for gene therapy because of their stability, low immunogenicity. and non-pathogenicity. However, disparity in AAV sample preparations (e.g., in capsid composition, DNA packaging, and impurities) gives rise to product heterogeneity, with possibly undesired effects on gene delivery. Ideally, AAV production should be with full control of AAV structure and genetic payload. Therefore, robust, efficient, and low material consuming methods are essential to characterize AAVs. Here, we use two emerging single-molecule techniques, mass photometry and Orbitrap-based charge-detection mass spectrometry, and show how they may efficiently and accurately characterize AAVs. We were able to resolve heterogeneous pools of particles, evaluating AAVs from two different serotypes (AAV8 and AAV2), produced by three independent production platforms, either lacking a genome or packed with a transgene. Together our data confirm that the different AAV production methods result in rather different and diverse AAV particle distributions. Especially for the packed AAVs, frequently additional subspecies were observed, next to the expected packed genome, mostly resulting from under- or overpackaging of genome material and/or residual empty particles. This work further establishes that both these single-particle techniques may become valuable tools in characterizing AAVs before they are used in gene therapy