Anti-Whole Serum polyclonal antibody

One of the key parameters for a successful treatment with any drug is the use of an optimal dose regimen. Bisphosphonates (BPs) have been in clinical use for over five decades and during this period clinical pharmacokinetic (PK) and pharmacodynamic (PD) evaluations have been instrumental for the identification of optimal dose regimens in patients. Ideal clinical PK and PD studies help drug developers explain variability in responses and enable the identification of a dose regimen with an optimal effect. PK and PD studies of the unique and rather complex pharmacological properties of BPs also help determine to a significant extent ideal dosing for these drugs. Clinical PK and PD evaluations of BPs preferably use study designs and assays that enable the assessment of both short- (days) and long-term (years) presence and effect of these drugs in patients. BPs are mainly used for metabolic bone diseases because they inhibit osteoclast-mediated bone resorption and the best way to quantify their effects in humans is therefore by measuring biochemical markers of bone resorption in serum and urine. In these very same samples BP concentrations can also be measured. Short-term serum and urine data after both intravenous (IV) and oral administration enable the assessment of oral bioavailability as well as the amount of BP delivered to the skeleton. Longer-term data provide information on the anti-resorptive effect as well as the elimination of the BP from the skeleton. Using PK-PD models to mathematically link the anti-resorptive action of the BPs to the amount of BP at the skeleton provides a mechanism-based explanation of the pattern of bone resorption during treatment. These models have been used successfully during the clinical development of BPs. Newer versions of such models, which include systems pharmacology and disease progression models, are more comprehensive and include additional PD parameters such as BMD and fracture risk. Clinical PK and PD studies of BPs have been useful for the identification of optimal dose regimens for metabolic bone diseases. These analyses will also continue to be important for newer research directions, such as BP use in the delivery of other drugs to the bone to better treat bone metastases and bone infections, as well as the potential benefit of BPs at non-skeletal targets for the prevention and treatments of soft tissue cancers, various fibroses, and other cardiovascular and neurodegenerative diseases, and reduction in mortality and extension of lifespan.

Many bacterial cell surface glycans, such as the O antigen component of lipopolysaccharide (LPS), are produced via the so-called Wzx/Wzy- or ABC transporter-dependent pathways. O antigens are highly diverse polysaccharides that protect bacteria from their environment and engage in important host-pathogen interactions. The specific structure and composition of O antigens are the basis of classifying bacteria into O serotypes. In the opportunistic pathogen Pseudomonas aeruginosa, there are currently 20 known O-specific antigen (OSA) structures. The clusters of genes responsible for 18 of these O antigens have been identified, all of which follow the Wzx/Wzy-dependent pathway and are located at a common locus. In this study, we located the two unidentified O antigen biosynthesis clusters responsible for the synthesis of the O15 and the O17 OSA structures by analyzing published whole-genome sequence data. Intriguingly, these clusters were found outside the conserved OSA biosynthesis locus and were likely acquired through multiple horizontal gene transfer events. Based on data from knockout and overexpression studies, we determined that the synthesis of these O antigens follows an ABC transporter-dependent rather than a Wzx/Wzy-dependent pathway. In addition, we collected evidence to show that the O15 and O17 polysaccharide chain lengths are regulated by molecular rulers with distinct and variable domain architectures. The findings in this report are critical for a comprehensive understanding of O antigen biosynthesis in P. aeruginosa and provide a framework for future studies. IMPORTANCE P. aeruginosa is a problematic opportunistic pathogen that causes diseases in those with compromised host defenses, such as those suffering from cystic fibrosis. This bacterium produces a number of virulence factors, including a serotype-specific O antigen. Here, we identified and characterized the gene clusters that produce the O15 and O17 O antigens and show that they utilize a pathway for synthesis that is distinct from that of the 18 other known serotypes. We also provide evidence that these clusters have acquired mutations in specific biosynthesis genes and have undergone extensive horizontal gene transfer within the P. aeruginosa population. These findings expand on our understanding of O antigen biosynthesis in Gram-negative bacteria and the mechanisms that drive O antigen diversity.