Arginine modifications by methylglyoxal: discovery in a recombinant monoclonal antibody and contribution to acidic species

Heterogeneity is common among protein therapeutics. For example, the so-called acidic species (charge variants) are typically observed when recombinant monoclonal antibodies (mAbs) are analyzed by weak-cation exchange chromatography (WCX). Several protein post-translational modifications have been established as contributors but still cannot completely account for all heterogeneity. As reported herein, an unexpected modification by methylglyoxal (MGO) was identified, for the first time, in a recombinant monoclonal antibody expressed in Chinese hamster ovary (CHO) cells. Modifications of arginine residues by methylglyoxal lead to two adducts (dihydroxyimidazolidine and hydroimidazolone) with increases of molecular weights of 72 and 54 Da, respectively. In addition, the modification by methylglyoxal causes the antibody to elute earlier in the weak cation exchange chromatogram. Consequently, the extent to which an antibody was modified at multiple sites corresponds to the degree of shift in elution time. Furthermore, cell culture parameters also affected the extent of modifications by methylglyoxal, a highly reactive metabolite that can be generated from glucose or lipids or other metabolic pathways. Our findings again highlight the impact that cell culture conditions can have on the product quality of recombinant protein pharmaceuticals.

SU-E-T-215: A Technique for Treating Patients outside the Mosaiq R&V System for TrueBeam Users (or 4DTC)

PURPOSE

When the record and verify (R&V) system (Mosaiq, Elekta Medical Systems) is unavailable to send information to the treatment console of the linear accelerator (Varian Clinac, Varian Medical Systems), treatment is manually delivered by entering parameters into the treatment console and loading backed up MLC files. The new linear accelerator, the TrueBeam (Varian Medical Systems) lacks the ability to manually deliver treatment by entering machine parameters into the treatment console.

METHODS

The TrueBeam can only deliver treatments using the R&V system or loading DICOM RT plan files directly in File Mode. Every time a prescription site is sent from the R&V system to the accelerator, a DICOM RT plan file is created by the R&V system. A script was created that reads the headers of these files, copies them to the treatment console and renames them in an identifiable form. At the end of each treatment day, the script is executed transferring only the DICOM RT plan files created that treatment day. A contingency report is then generated from the R&V system, which contains machine parameters for all fields for all patients under treatment. When the R&V system is unavailable the RT plan files are opened in file mode, and the machine parameters are verified using the contingency report before delivery. This system was tested on a cohort of patients. Each patient's plan was opened in file mode and the machine parameters were verified against the patient's planned treatment in the R&V system.

RESULTS

All files opened in file mode were identical to the information stored in the R&V system. This was tested both on the TrueBeam and accelerators having the 4DTC.

CONCLUSIONS

Our technique was validated and is an alternative method for delivering treatment when the R&V system is unavailable.

SU-E-T-186: An Automated Quality Assurance Tool for HDR Treatment Planning

PURPOSE

Treatment planning for high dose rate (HDR) brachytherapy requires many user inputs, all of which are potential sources of error. The goal of quality assurance (QA) is to ensure that errors are not made. In this study, we developed a software program to analyze the treatment printout from the HDR treatment planning computer and flag any suspected errors.

METHODS

The treatment printout from the HDR planning computer is imported by the software. The software then performs the following checks: (1) verifies that the correct source was chosen (we have multiple in our database), (2) performs an independent decay of the Ir-192 source, (3) verifies source step size, (4) verifies the offsets and indexer lengths in the catheter definitions based upon expected values for the applicator used, (4) performs an independent 2nd check of dose to a cloud of dose points surrounding the treatment region, (5) verifies that the dose per fraction and the number of fractions were entered correctly in the planning computer, and (6) verifies that the dose volume histogram (DVH) metrics were within acceptable tolerances. The software then prints this information to a PDF file, which is appended to the original treatment printout and placed in the patient's medical record.

RESULTS

This QA tool has now been implemented for six months in our clinic, and is a critical QA tool in our HDR program. Although each plan is checked by an independent 2nd physicist, this tool provides an additional independent check on the treatment plan.

CONCLUSIONS

A simple series of automatic 2nd checks helps reduce the risk of errors occurring in the treatment planning portion of HDR brachytherapy and can easily be implemented.

Transplant surgery fellow perceptions about training and the ensuing job market-are the right number of surgeons being trained?

The American Society of Transplant Surgeons (ASTS) sought whether the right number of abdominal organ transplant surgeons are being trained in the United States. Data regarding fellowship training and the ensuing job market were obtained by surveying program directors and fellowship graduates from 2003 to 2005. Sixty-four ASTS-approved programs were surveyed, representing 139 fellowship positions in kidney, pancreas and/or liver transplantation. One-quarter of programs did not fill their positions. Forty-five fellows graduated annually. Most were male (86%), aged 31-35 years (57%), married (75%) and parents (62%). Upon graduation, 12% did not find transplant jobs (including 8% of Americans/Canadians), 14% did not get jobs for transplanting their preferred organ(s), 11% wished they focused more on transplantation and 27% changed jobs early. Half fellows were international medical graduates; 45% found US/Canadian transplant jobs, particularly 73% with US/Canadian residency training. Fellows reported adequate exposure to training volume, candidate selection, pre/postoperative care and organ procurement, but not to donor management/selection, outpatient care and core didactics. One-sixth noted insufficient 'mentoring/preparation for a transplantation career'. Currently, there seem to be enough trainees to fill entry-level positions. One-third program directors believe that there are too many trainees, given the current and foreseeable job market. ASTS is assessing the total workforce of transplant surgeons and evolving manpower needs.

A high-throughput proteo-genomics method to identify antibody targets associated with malignant disease

Identification of antibody targets associated with malignant disease is indispensable to developing passive and active antibody-based therapeutics or diagnostic agents. We have developed a novel technique combining Western blotting, genetic profiling, and mass spectroscopy that allows for the rapid and unambiguous identification of such antigens in a high-throughput manner. Herein, we demonstrate this technique, designated Ab SCAN, by deducing the known target of a monoclonal antibody and by identifying a new antigen that was observed to be the frequent target of humoral immune responses in prostate cancer patients. In both instances, a specific antigen emerged as the sole protein candidate. The newly identified antigen, mannose-6-phosphate/IGF II receptor, may be an important naturally immunogenic antigen involved in prostate cancer. The Ab SCAN technique is uniquely suited to the analysis of longitudinal serum samples from clinical studies and could be a powerful tool to correlate humoral immune responses directed against discreet antigens with clinical events.

Jaundice in the healthy newborn infant: a new approach to an old problem

We measured the serum bilirubin concentrations in 2,416 consecutive infants admitted to our well baby nursery. The maximal serum bilirubin concentration exceeded 12.9 mg/dL (221 mumol/L) in 147 infants (6.1%), and these infants were compared with 147 randomly selected control infants with maximal serum bilirubin levels less than or equal to 12.9 mg/dL. A serum bilirubin concentration greater than 12.9 mg/dL was associated strongly with breast-feeding (P = .0000) and percentage of weight loss after birth (P = .0001), as well as with maternal diabetes, oriental race, decreased gestational age, male sex, bruising, and induction of labor with oxytocin. Risk ratios and the risk of jaundice were calculated for hypothetical infants in the presence and absence of these variables. These calculations show that, in certain infants, "nonphysiologic" jaundice is likely to develop and its presence in such infants might not require laboratory investigations. In others, a modest degree of hyperbilirubinemia could be cause for concern. An awareness of these factors and their potential contribution to serum bilirubin levels permits a more rational approach to the action levels used for the investigation of jaundice in the newborn. We need a new definition of physiologic jaundice.

Normal serum bilirubin levels in the newborn and the effect of breast-feeding

We measured the serum bilirubin concentrations in 2,416 consecutive infants admitted to our well-baby nursery. The maximum serum bilirubin concentration exceeded 12.9 mg/dL (221 mumol/L) in 147 infants (6.1%), and these infants were compared with 147 randomly selected control infants with maximum serum bilirubin levels less than or equal to 12.9 mg/dL. In 66 infants (44.9%), we identified an apparent cause for the jaundice, but in 81 (55%), no cause was found. Of infants for whom no cause for hyperbilirubinemia was found, 82.7% were breast-fed v 46.9% in the control group (P less than .0001). Breast-feeding was significantly associated with hyperbilirubinemia, even in the first three days of life. The 95th percentile for bottle-fed infants is a serum bilirubin level of 11.4 mg/dL v 14.5 mg/dL for the breast-fed population, and the 97th percentiles are 12.4 and 14.8 mg/dL, respectively. Of the formula-fed infants, 2.24% had serum bilirubin levels greater than 12.9 mg/dL v 8.97% of breast-fed infants (P less than .000001). When compared with previous large studies, the incidence of "readily visible" jaundice (serum bilirubin level greater than 8 mg/dL) appears to be increasing. The dramatic increase in breast-feeding in the United States in the last 25 years may explain this observation. There is a strong association between breast-feeding and jaundice in the healthy newborn infant. Investigations for the cause of hyperbilirubinemia in healthy breast-fed infants may not be indicated unless the serum bilirubin level exceeds approximately 15 mg/dL, whereas in the bottle-fed infant, such investigations may be indicated if the serum bilirubin exceeds approximately 12 mg/dL.(ABSTRACT TRUNCATED AT 250 WORDS)

Care of low-birthweight and sick newborn infants in community hospitals. Effect of an education program

We studied the effect of an education program on newborn care practices, documented by chart review, in nine community hospitals in central Pennsylvania. Following a visit to each hospital, specific recommendations were made and courses were offered at the regional center. A follow-up review of newborn charts showed significant improvement in newborn care. This kind of educational program, particularly if directed at identified problems in individual hospitals, appears to be effective. In addition, chart reviews can provide the information necessary for assessing both care practices and the effect of an educational program.

Neonatal jaundice in full-term infants. Role of breast-feeding and other causes

Serum bilirubin determinations were performed on 264 term infants who were consecutively delivered via the vaginal route. Forty-one infants (15.5%) had serum bilirubin concentrations greater than 12 mg/dL. No cause for this was found, initially, in 23 (56%) of these infants. On the third hospital day, the mean (+/- SD) serum bilirubin level was 6.9 +/- 3.6 mg/dL in breast-fed infants and 6.5 +/- 3.2 mg/dL in bottle-fed infants. Of the 23 infants without obvious cause for hyperbilirubinemia, eight (four bottle-fed and four breast-fed infants) had serum bilirubin concentrations greater than 12 mg/dL on the third hospital day, whereas in 15 (14 breast-fed infants and one bottle-fed infant), the elevated serum bilirubin level occurred on day 4 or 5. Breast-feeding does not seem to affect the total serum bilirubin level in the first three days of life but may be associated with an increased incidence of hyperbilirubinemia subsequently. In a normal full-term population, routine investigations do not disclose a cause for hyperbilirubinemia in about half of the patients.

Infants weighing 1,000 grams or less at birth: developmental outcome for ventilated and nonventilated infants

The neurodevelopmental outcome at a mean age of 40 months was investigated in 23/25 surviving infants of birth weights less than or equal to 1,000 gm. Eight infants required intubation and assisted ventilation and 17 were not ventilated. One ventilated infant was lost to follow-up and one nonventilated infant was a victim of sudden infant death syndrome at age 6 months. Fifteen (65%) had a good outcome but the differences between ventilated and nonventilated infants were striking. Thirteen (81%) of the nonventilated group were normal, but only two ventilated survivors (28%) were normal (P less than 0.05). Cicatricial retrolental fibroplasia occurred in three (43%) of the ventilated survivors and in none of the nonventilated infants (P less than .02). The requirement for assisted ventilation in these very low-birth-weight infants is associated with significant morbidity. Improvement in outcome may depend as much upon better understanding and management of prenatal events as upon improvements in neonatal care.

Outcome for survivors of mechanical ventilation weighing less than 1,250 gm at birth

We investigated the outcome in 28 survivors of mechanical ventilation weighing less than 1,250 gm at birth. Fifteen infants (54%) had neurodevelopmental sequelae, of whom eight had major handicaps. These eight infants differed significantly from the rest of the infants studied in the following manner: lower mean birth weight and gestational age, delay in transportation to our Neonatal Intensive Care Unit, and high incidence of bacterial sepsis. The remaining seven infants with NDS were functionally normal or minimally impaired at the time of the study, although significant problems may yet emerge with continued follow-up. Retrolental fibroplasia was diagnosed in 11 infants (39%) and resolved in two. The development of RLF was associated with prolonged oxygen exposure and the presence of bacterial sepsis. However, since major handicap, RLF, and sepsis were all problems observed in the smallest infants, a cause-and-effect relationship between sepsis and these sequelae remains speculative.

Head growth in sick premature infants--a longitudinal study

Serial weekly measurements of somatic growth and head circumference were made for ten weeks on 41 appropriately grown sick preterm infants (gestational age 28 to 32 weeks) with severe neonatal problems. Twenty-seven (66%) required prolonged assisted ventilation. During the period of acute illness, the velocity of growth for the sick infants was below that of the normal fetus, with deviation away from and below the normal fetal growth curve. During recovery, head growth paralleled that of normal fetal growth, and subsequently rapid "catch-up" growth in head circumference occurred. By comparison, six similar infants, whose head circumference followed the intrauterine growth curve, proved to have hydrocephalus. These results suggest that: (1) the brain participates in the growth retardation associated with being sick and premature and that apparently normal head growth under comparable circumstances may be associated with hydrocephalus; (2) in spite of an energy intake ranging from 80 to 120 kcal/kg/day by the end of the second postpartum week, normal growth in the sick low-birth-weight infant does not occur until their acute illness has resolved.