Evaluation of Concomitant Facial Fracture in Traumatic Brain Injury Patients-Simplification and External Validation of a Prediction Model

BACKGROUND

Patients with traumatic brain injuries (TBIs) often experience concurrent facial bone fractures. In 2021, a prediction model with 10 variables was published and precisely predicted concomitant facial fractures in TBI patients. Herein, external validation and simplification of this model was performed.

METHODS

Traumatic brain injury patients treated at a major referral trauma center were retrospectively reviewed for 1 year. The original prediction model (published in 2021), which was developed from a rural level II trauma center, was applied for external validation. A new and simplified model from our level I trauma center was developed and backwardly validated by rural level II trauma center data.

RESULTS

In total, 313 TBI patients were enrolled; 101 (32.3%) had concomitant facial fractures. When the previous prediction model was applied to the validation cohort, it achieved acceptable discrimination, with an area under the receiver operating characteristic curve (AUC) of 0.713 and good precision, with a Brier score of 0.083. A new and simplified model with 6 variables (age, tooth rupture, epistaxis, facial lesion, eye injury, and intracranial hemorrhage) was created with excellent discrimination (AUC = 0.836) and good precision (Brier score of 0.055). The backward validation of this new model also showed excellent discrimination in the cohort used to develop the original model (AUC = 0.875).

CONCLUSION

The original model provides an acceptable and reproducible prediction of concomitant facial fractures among TBI patients. A simplified model with fewer variables and the same accuracy could be applied in the emergency department and at higher- and lower-level trauma centers.

The Role of Open Cardiopulmonary Resuscitation in Chest Trauma Patients with No Sign of Life: A National Trauma Data Bank Study

PURPOSE

The effectiveness of open cardiopulmonary resuscitation (OCPR) remains controversial for trauma patients. In this current study, the role of OCPR in managing chest trauma patients is evaluated using nationwide real-world data.

METHODS

From 2014 to 2015, the National Trauma Data Bank was retrospectively queried for chest trauma patients with out-of-hospital cardiac arrest status. The emergency department (ED) and overall survival of patients without signs of life were analyzed. Multivariate logistic regression (MLR) analysis was performed to evaluate independent factors of mortality for the target group. Furthermore, a subset group of patients who survived after the ED were studied, focusing on the duration of survival after leaving the ED.

RESULTS

A total of 911 patients were enrolled in this study (OCPR vs. non-OCPR: 161 patients vs. 750 patients). The average overall mortality rate was 98.6% (N = 898). Among penetrating chest trauma patients, non-survivors in the ED had significantly higher proportions of gunshot injuries (83.9% vs. 69.7%, p = 0.001) and lower proportions of OCPR (20.7% vs. 44.4%, p < 0.001). MLR analysis showed that gunshot injuries and non-OCPR were significantly related to ED mortality in penetrating trauma patients without signs of life (odds ratio = 2.039, p = 0.006 and odds ratio = 2.900, p < 0.001, respectively). However, the overall survival rate of patients after ED survival (n = 99) was 9.9%, and only 21.2% (n = 21) of them survived more than 1 day after leaving the ED.

CONCLUSION

OCPR could be considered in situations where appropriate indications exist. The survival benefit was observed in critically ill patients with penetrating chest trauma who show no signs of life. By enhancing ED survival, OCPR may also contribute to overall survival improvement.

Validation of the Twenty-Four-Hour Threshold for Bladder Repair: Impact on Infection Rates Using the National Trauma Data Bank

PURPOSE

This study aimed to validate the previously reported association between delayed bladder repair and increased infection rates using the National Trauma Data Bank (NTDB).

METHODS

Bladder injury patients with bladder repair in the NTDB from 2013 to 2015 were included. Propensity score matching (PSM) was used to compare mortality, infection rates, and hospital length of stay (LOS) between patients who underwent bladder repair within 24 h and those who underwent repair after 24 h. Linear regression and multivariate logistic regression analyses were also performed.

RESULTS

A total of 1658 patients were included in the study. Patients who underwent bladder repair after 24 h had significantly higher infection rates (5.4% vs. 1.2%, p = 0.032) and longer hospital LOS (17.1 vs. 14.0 days, p = 0.032) compared to those who underwent repair within 24 h after a well-balanced 1:1 PSM (N = 166). Linear regression analysis showed a positive correlation between time to bladder repair and hospital LOS for patients who underwent repair after 24 h (B-value = 0.093, p = 0.034). Multivariate logistic regression analysis indicated that bladder repair after 24 h increased the risk of infection (odds = 3.162, p = 0.018). Subset analyses were performed on patients who underwent bladder repairs within 24 h and were used as a control group. These analyses showed that the time to bladder repair did not significantly worsen outcomes.

CONCLUSIONS

Delayed bladder repair beyond 24 h increases the risk of infection and prolongs hospital stays. Timely diagnosis and surgical intervention remain crucial for minimizing complications in bladder injury patients.

The Role of Diagnostic Laparoscopy in the Evaluation of Abdominal Trauma Patients: A Trauma Quality Improvement Program Study

PURPOSE

We aimed to identify factors related to delayed intervention in abdominal trauma patients who underwent diagnostic laparoscopy using a nationwide databank.

METHODS

From 2017 to 2019, abdominal trauma patients who underwent diagnostic laparoscopy were retrospectively evaluated using the Trauma Quality Improvement Program. Patients who underwent delayed interventions after a primary diagnostic laparoscopy were compared with those who did not. Factors associated with poor outcomes that are usually correlated with overlooked injuries and delayed interventions were also analyzed.

RESULTS

Of the 5221 studied patients, 4682 (89.7%) underwent inspection without any intervention. Only 48 (0.9%) patients underwent delayed interventions after primary laparoscopy. Compared with patients receiving immediate interventions during primary diagnostic laparoscopy, patients receiving delayed interventions were more likely to have small intestine injuries (58.3% vs. 28.3%, p < 0.001). Among patients with hollow viscus injuries, a significantly higher probability of overlooked injuries that required delayed intervention was observed in patients with small intestine injuries (small intestine injury: 16.8%; gastric injury: 2.5%; large intestine injury: 5.2%). However, delayed small intestine repair did not significantly affect the risk of surgical site infection (SSI) (p = 0.249), acute kidney injury (AKI) (p = 0.998), or hospital length of stay (LOS) (p = 0.053). In contrast, significantly positive relationships between delayed large intestine repair and poor outcomes were observed (SSI, odds ratio = 19.544, p = 0.021; AKI, odds ratio = 27.368, p < 0.001; LOS, β = 13.541, p < 0.001).

CONCLUSIONS

Most examinations and interventions (near 90%) were successful during primary laparoscopy for abdominal trauma patients. Small intestine injuries were easily overlooked. Delayed small intestine repair-related poor outcomes were not observed.

Does a time threshold exist for bladder repair after which outcomes worsen? A Trauma Quality Improvement Program study

BACKGROUND

The appropriate timing of surgical intervention for bladder injuries is not well-defined. The effect of time to surgery on the outcomes of patients with a bladder injury was assessed using data from the Trauma Quality Improvement Program.

METHODS

Patients with dominant or isolated bladder injuries who underwent surgical repair from 2017 to 2019 were studied. Mortality, infection (surgical site infection or sepsis), acute kidney injury, overall length of stay, and length of stay after surgery were compared between patients who underwent bladder repair within and after 24 hours of arrival at the emergency department. The role of time to surgical repair in the outcomes of patients with a bladder injury was evaluated.

RESULTS

A total of 1,507 patients with a mean time to bladder repair of 14.0 hours were studied. In total, 233 (15.5%) patients with a bladder injury underwent bladder repair more than 1 day after emergency department arrival. These patients had significantly more infections (5.6% vs 2.5%, P = .011), more acute kidney injuries (7.8% vs 1.8%, P < .001), and a longer length of stay after surgery (16.0 vs 12.3 days, P = .001) than patients who underwent bladder repair within 1 day. A time to bladder repair longer than 24 hours after emergency department arrival did not significantly affect mortality (P = .075) but significantly increased the risk of infection/acute kidney injury (odds = 1.823, P = .040). However, the infection/acute kidney injury risk did not increase with increasing time to surgery in patients who underwent bladder repair within 24 hours (P = .120).

CONCLUSION

Patients with dominant or isolated bladder injuries may have a poor outcome (ie, increased infection rate, acute kidney injury, longer overall length of stay, and longer length of stay after bladder repair) if they undergo surgical repair more than 24 hours after arrival at the emergency department.

Does Thoracic Endovascular Aortic Repair for Blunt Thoracic Aortic Injury Increase the Probability of Delayed Intra-abdominal Hemorrhage in Patients With Concomitant Blunt Abdominal Trauma?

PURPOSE

Most blunt thoracic aortic injuries (BTAIs) may be treated using thoracic endovascular aortic repair (TEVAR), and most blunt abdominal traumas (BATs) are managed conservatively. We hypothesized that severe trauma that needs TEVAR may increase the risk of delayed intra-abdominal hemorrhage in patients with concomitant BTAI and BAT because of the potential hemorrhagic shock, disseminated intravascular coagulopathy, blood loss, consequent need for blood transfusion, and procedure-associated heparinization.

MATERIALS AND METHODS

From 2015 to 2019, blunt trauma patients with concomitant severe chest trauma and abdominal trauma who could be managed conservatively were studied. The probability of delayed intra-abdominal hemorrhage was compared between patients with concomitant BTAI who received or did not undergo TEVAR. Propensity score matching (PSM), inverse probability of treatment weighting (IPTW), and multivariate logistic regression (MLR) were used to eliminate discrepancies between these 2 groups.

RESULTS

Among the 341 studied patients, there were 26 patients with BTAI, and 19 of them underwent TEVAR. Delayed intra-abdominal hemorrhage was observed in 4 patients (21.1%, 4/19) who underwent TEVAR. Both PSM and IPTW showed that patients who underwent TEVAR for concomitant BTAI had a greater delayed need for blood transfusions and a larger proportion of delayed intra-abdominal hemorrhage than patients who did not undergo the procedure. The MLR analysis showed that TEVAR for BTAI was an independent risk factor for delayed intra-abdominal hemorrhage (odds ratio: 10.534, 95%, p<0.001).

CONCLUSION

An increased probability of delayed intra-abdominal hemorrhage in patients with BAT (who could be managed conservatively) was observed in patients who underwent TEVAR for concomitant BTAI.

CLINICAL IMPACT

More attention should be give in patients with high grade aortic injuries and concomitant abdominal trauma.

The application of the WSES classification system for open pelvic fractures-validation and supplement from a nationwide data bank

Background

Open pelvic fractures are rare but complex injuries. Concomitant external and internal hemorrhage and wound infection-related sepsis result in a high mortality rate and treatment challenges. Here, we validated the World Society Emergency Society (WSES) classification system for pelvic injuries in open pelvic fractures, which are quite different from closed fractures, using the National Trauma Data Bank (NTDB).

Methods

Open pelvic fracture patients in the NTDB 2015 dataset were retrospectively queried. The mortality rates associated with WSES minor, moderate and severe injuries were compared. A multivariate logistic regression model (MLR) was used to evaluate independent factors of mortality. Patients with and without sepsis were compared. The performance of the WSES classification in the prediction of mortality was evaluated by determining the discrimination and calibration.

Results

A total of 830 open pelvic fracture patients were studied. The mortality rates of the mild, moderate and severe WSES classes were 3.5%, 11.2% and 23.8%, respectively (p < 0.001). The MLR analysis showed that the presence of sepsis was an independent factor of mortality (odds of mortality 9.740, p < 0.001). Compared with patients without sepsis, those with sepsis had significantly higher mortality rates in all WSES classes (minor: 40.0% vs. 3.1%, p < 0.001; moderate: 50.0% vs. 9.1%, p < 0.001; severe: 66.7% vs. 22.2%, p < 0.001). The receiver operating characteristic (ROC) curve showed an acceptable discrimination of the WSES classification alone for evaluating the mortality of open pelvic fracture patients [area under curve (AUC) = 0.717]. Improved discrimination with an increased AUC was observed using the WSES classification plus sepsis (AUC = 0.767).

Conclusions

The WSES guidelines can be applied to evaluate patients with open pelvic fracture with accurate evaluation of outcomes. The presence of sepsis is recommended as a supplement to the WSES classification for open pelvic fractures.

Modeling assembly, aggregation, and chaperoning of immunoglobulin G production in insect cells

A model for immunoglobulin G (IgG) production in the baculovirus-insect cell system was developed that incorporates polypeptide synthesis, oligomer assembly, protein aggregation, and protein secretion. In addition, the capacity of a chaperone to protect heavy and light chain polypeptides from protein aggregation was considered by including in vitro chaperone-peptide binding and dissociation kinetic constants from the literature. Model predictions were then compared to experiments in which the chaperone immunoglobulin heavy chain binding protein, BiP, was coexpressed by coinfecting insect cells with BiP-containing baculovirus. The model predicted a nearly twofold increase in intracellular and secreted IgG that was similar to the behavior observed experimentally after approximately 3 days of coexpressing heterologous IgG and BiP. However, immunoglobulin aggregation was still significant in both the model simulation and experiments, so the model was then used to predict the effect of strategies for improving IgG production even further. Increasing expression of the chaperone BiP by 10-fold over current experimental levels provided a 2.5-fold increase in secreted IgG production over IgG assembly without BiP. Alternatively, the expression of BiP earlier in the baculovirus infection cycle achieved a twofold increase in protein secretion without requiring excessive BiP production. The potential effect of cochaperones on BiP activity was considered by varying the BiP binding and release constants. The utilization of lower binding and release kinetic constants led to a severalfold increase in IgG secretion because the polypeptides were protected from aggregation for greater periods. An optimized strategy for chaperone action would include the rapid peptide binding of a BiP-ATP conformation along with the slow peptide release of a BiP-ligand conformation. However, even with an optimized chaperoning system, limitations in the secretion kinetics can result in the accumulation of intracellular IgG. Thus, the entire secretory pathway must be considered when enhanced secretion of heterologous proteins is desired.

A baculovirus superinfection system: efficient vehicle for gene transfer into Drosophila S2 cells

The baculovirus expression vector system is considered to be a safe, powerful, but cell-lytic heterologous protein expression system in insect cells. We show here that there is a new baculovirus system for efficient gene transfer and expression using the popular and genetically well-understood Drosophila S2 cells. The recombinant baculovirus was constructed to carry an enhanced green fluorescent protein under the control of polyhedrin promoter as a fluorescent selection marker in the Sf21 cell line. Recombinant baculoviruses were then used to transduce S2 cells with target gene expression cassettes containing a Drosophila heat shock protein 70, an actin 5C, or a metallothionein promoter. Nearly 100% of the S2 cells showed evidence of gene expression after infection. The time course for the optimal protein expression peaked at 24 to 36 h postinfection, which is significantly earlier than a polyhedrin-driven protein expression in Sf21 cells. Importantly, S2 cells did not appear to be lysed after infection, and the protein expression levels are comparable to those of proteins under the control of polyhedrin promoter in several lepidopteran cell lines. Most surprisingly, S2 cells permit repetitive infections of multiple baculoviruses over time. These findings clearly suggest that this baculovirus-S2 system may effect the efficient gene transfer and expression system of the well-characterized Drosophila S2 cells.

Formulation, stability, and delivery of live attenuated vaccines for human use

The successful use of live attenuated viral and bacterial vaccines depends not only on the proper choice and delivery of the microorganisms, but also on maintaining the sufficient potency required for an immune response. The inherent lability of live organisms presents a particular formulation challenge in terms of stabilizing and preserving vaccine viability during manufacturing, storage, and administration. This review examines pharmaceutical approaches to the stabilization, formulation, and lyophilization of biological macromolecules in general, as well as the specific applicability of these principles to live attenuated viral and bacterial vaccines. Several formulation development case studies with live vaccines are presented. In addition, comparative stability data are summarized for many other live viral and bacterial preparations. Various pharmaceutical issues with conventional and novel delivery systems for administration of parenteral and oral live vaccines are also discussed.

Cloning and characterization of glial cell line-derived neurotrophic factor receptor-B: a novel receptor for members of glial cell line-derived neurotrophic factor family of neurotrophic factors

Glial cell line-derived neurotrophic factor (GDNF) is a potent neurotrophic factor with diverse biological functions. Signal transduction of GDNF is mediated by binding to a glycosyl-phosphatidylinositol (GPI)-linked receptor GDNFR-alpha and activation of c-RET tyrosine kinase. The recent discovery of a new GDNF homolog neurturin raises the possibility that multiple receptors exist for the members in the GDNF family. Here we report isolation of the gene encoding a new receptor called GDNFR-beta. Sequence analysis indicated that GDNFR-beta is also a GPI-linked protein, with 47% identity to GDNFR-alpha. The GDNFR-beta transcript was preferentially expressed in the brain, spleen and lung, but moderate levels of GDNFR-beta mRNA were also found in kidney and the entire gastrointestinal track. In situ hybridization revealed high expression levels in the entorhinal cortex and olfactory bulb, followed by cortex, septum, inferior and superior colliculus, and zona inserta. A laminar pattern of expression was detected in layer III of the cortex. Treatment with GDNF of PC12 cells transfected with the GDNFR-beta gene activated mitogen-activated protein kinase (MAPK) and elicited neurite outgrowth. GDNFR-alpha and GDNFR-beta together form a new family of GPI-linked receptors for GDNF-like molecules.

Thioredoxin domain non-equivalence and anti-chaperone activity of protein disulfide isomerase mutants in vivo

Coexpression of the enzyme, protein disulfide isomerase (PDI), has been shown to increase soluble and secreted IgG levels from baculovirus-infected insect cells (Hsu, T.-A., Watson, S., Eiden, J. J., and Betenbaugh, M. J. (1996) Protein Expression Purif. 7, 281-288). PDI is known to include catalytic active sites in two separate thioredoxin-like domains, one near the amino terminus and another near the carboxyl terminus. To examine the role of these catalytic active sites in enhancing immunoglobulin solubility, baculovirus constructs were utilized with cysteine to serine mutations at the first cysteine of one or both of the CGHC active site sequences. Trichoplusia ni insect cells were coinfected with a baculovirus vector coding for IgG in concert with either the wild-type human PDI virus, amino-terminal mutant (PDI-N), carboxyl-terminal mutant (PDI-C), or mutant with both active sites altered (PDI-NC). Western blot analysis revealed that both immunoglobulins and PDI protein were expressed in the coinfected cells. To evaluate the effect of the PDI variants on immunoglobulin solubility and secretion, the infected cells were labeled with 35S-amino-acids for different periods, and the soluble immunoglobulins were immunoprecipitated from clarified cell lysates and culture medium using anti-IgG antibodies. Only coinfections with the wild-type PDI and PDI-N mutant led to increased immunoglobulin solubility and higher IgG secretion. In contrast, infection with the PDI-C and PDI-NC variants actually lowered immunoglobulin solubility levels below those achieved with a negative control virus. Immunoprecipitation with anti-PDI antibody revealed that heterologous PDI-C and PDI-NC were insoluble, even though PDI-N and wild-type PDI protein were detected in soluble form. The capacity for PDI-N to increase immunoglobulin solubility whereas the PDI-C mutant lowered solubility indicates that the amino- and carboxyl-terminal thioredoxin domains of PDI are functionally distinct in vivo following mutations to the active site. Furthermore, mutations at the active site of the carboxyl-terminal thioredoxin domain result in PDI variants that can act as anti-chaperones of immunoglobulin solubility in vivo as has been observed in vitro for lysozyme aggregation by wild-type PDI and PDI mutants (Puig, A., and Gilbert, H. F. (1994) J. Biol. Chem. 269, 7764-7771).

Differential N-glycan patterns of secreted and intracellular IgG produced in Trichoplusia ni cells

Structures of the N-linked oligosaccharide attached to the heavy chain of a heterologous murine IgG2a produced from Trichoplusia ni (TN-5B1-4, High Five) insect cells were characterized. Coexpression of the chaperone immunoglobulin heavy chain-binding protein (BiP) in the baculovirus-infected insect cells increased the soluble intracellular and secreted IgG level. This facilitated the detailed analysis of N-glycans from both intracellular and secreted IgG. Following purification of the immunoglobulins using Protein A-Sepharose, glycopeptides, prepared by trypsin-chymotrypsin digestion, were further digested with glycoamidase from sweet almond emulsin to obtain the oligosaccharide moieties. The resulting oligosaccharides were then reductively aminated with 2-aminopyridine and the structures identified by two-dimensional high performance liquid chromatography mapping (Tomiya, N., Awaya, J., Kurono, M., Endo, S., Arata, Y., and Takahashi, N. (1988) Anal. Biochem. 171, 73-90). The N-glycans obtained from the secreted IgG contain 35% complex type, some with terminal galactose residues at either alpha1, 3-Man or alpha1,6-Man branches of the Man3GlcNAc2 core. The remaining oligosaccharides detected in the secreted IgG were principally hybrid (30%) and paucimannosidic (35%) type N-glycans. Most (84%) of these secreted glycoforms contained fucose alpha1, 6-linked to the innermost GlcNAc residue and the presence of a potentially allergenic fucose alpha1,3-linked to the innermost GlcNAc residue was also detected. In contrast, the intracellular immunoglobulins included 50% high mannose-type N-glycans with lower levels of complex, hybrid, and paucimannosidic-type structures. Reverse phase one-dimensional high performance liquid chromatography analysis of the IgG N-glycans in the absence of heterologous BiP exhibited a similar distribution of intracellular and secreted glycoforms. These studies indicate that Trichoplusia ni TN-5B1-4 cells are capable of terminal galactosylation. However, the processing pathways in these cell lines appear to diverge from mammalian cells in the formation of paucimannosidic structures, in the presence of alpha1,3-fucose linkages, and in the absence of sialylation.

Coexpression of molecular chaperone BiP improves immunoglobulin solubility and IgG secretion from Trichoplusia ni insect cells

Infection of Trichoplusia ni (BTI-TN5B1-4) insect cells with a baculovirus coding for immunoglobulin G resulted in significant intracellular insolubility of the immunoglobulin chains. In order to increase the immunoglobulin solubility, the chaperone BiP was coexpressed in the insect cells using a separate baculovirus vector. This heterologous BiP was observed to associate with immunoglobulin chains in vivo and enhance the level of soluble intracellular and secreted IgG obtained from T.ni. Pulse chase studies indicated that the heterologous BiP increased the level of soluble nascent immunoglobulin chains and assembly intermediates to suggest that BiP is acting as a true molecular chaperone. The effect of heterologous BiP became more significant with time post-infection as secreted IgG levels increased by 90% after 3.4 days of baculovirus infection. Even following the treatment of cells with tunicamycin, BiP coexpression still enhanced immunoglobulin solubility and secretion to indicate that BiP does not function specifically to retain unglycosylated proteins in the endoplasmic reticulum. Thus, coexpression of a molecular chaperone may be used to enhance cellular productivity and protein secretion provided that the chaperone is involved with post-translational processing and significant protein aggregation is observed.

Rescue of immunoglobulins from insolubility is facilitated by PDI in the baculovirus expression system

A substantial fraction of immunoglobulin heavy and light chain polypeptides were insoluble when expressed in the baculovirus-insect cell expression system. In the presence of coexpressed heterologous protein disulfide isomerase (PDI), however, the solubility of the immunoglobulins was enhanced and IgG was secreted at higher levels from baculovirus-infected Trichoplusia ni insect cells. Pulse-chase experiments indicated that some immunoglobulin polypeptides were initially insoluble in the presence of PDI but subsequently were rescued in a soluble form competent for IgG assembly and secretion. Recovery of the insoluble immunoglobulins was not observed in the absence of coexpressed PDI. Even after treatment of insect cells with tunicamycin to inhibit N-glycosylation of immunoglobulin heavy chains, coexpressed PDI was able to salvage insoluble immunoglobulins and secrete these modified glycoforms. The capacity for PDI to rescue immunoglobulins was also demonstrated in vitro where immunoglobulin heavy chains and light chain dimers were salvaged from aggregates of denatured IgG. PDI-mediated rescue of proteins, perhaps assisted by chaperones and other foldases, may be important in vivo where insolubility is a common occurrence for newly synthesized polypeptides.

Effects of co-expressing chaperone BiP on functional antibody production in the baculovirus system

The assembly pathway of the insect cell Spodoptera frugiperda (Sf-9) was engineered to include expression of the murine chaperone immunoglobulin heavy chain binding protein (BiP) using the baculovirus vector. The impact of BiP coexpression on the production and secretion of functional and soluble recombinant immunoglobulin IgG levels was evaluated. Recombinant BiP was found to associate specifically with immunoglobulins in immunoprecipitation studies. Coinfection of insect cells with a BiP-containing baculovirus and baculoviruses coding for two different murine IgG proteins increased intracellular functional antibody activity levels substantially above the levels observed in the absence of BiP. Soluble intracellular immunoglobulin levels were found to increase as well. However, secreted functional antibody levels did not increase significantly. Also, degradation of heavy chain immunoglobulin in insect cells was indicated by the accumulation of lower molecular weight immunoglobulins at 4 days postinfection. Coexpression of light chains reduced the level of these lower molecular weight immunoglobulins while BiP coexpression led to enhanced levels. These findings suggest that coexpressed BiP can increase intracellular soluble and functional antibody yields but that secretion in the baculovirus-insect cell system must be limited at some post-translational step.

Borna disease virus p24 and p38/40 synthesized in a baculovirus expression system: virus protein interactions in insect and mammalian cells

To facilitate studies of the individual viral proteins, two Borna disease virus proteins, p24 and p38/40, were synthesized in vitro by means of a baculovirus expression system and examined for antigenic identity to viral proteins from BDV-infected cells. Recombinant proteins p24 and p38/40 were nearly identical in size to the viral proteins from BDV-infected cells. Immunoblot and immunocytochemistry analysis of BDV proteins from infected tissue culture cells and rat brain showed binding of antisera directed against the recombinant proteins. Specific recognition of the recombinant proteins by Borna disease virus-specific convalescent antisera and monoclonal antibodies further demonstrated that the antigenic characters of the p24 and p38/40 had been conserved. Polyclonal antibody directed against either of the recombinant proteins recognized only the protein used as immunogen, without cross reactivity with the other recombinant protein, indicating no common epitopes. Moreover, these data confirmed the proposed gene coding assignments of ORF I and II of BDV p38/40 and p24, respectively. Both of the recombinant proteins were secreted into the media of insect cells in tissue culture, but secretion of recombinant p24 was evident only as a dimeric form and not with the monomeric form. Immunoprecipitation studies performed with monoclonal antibodies and BDV proteins from infected rat brain suggested that a heterodimer forms via binding of p40 to the p24.

Engineering the assembly pathway of the baculovirus-insect cell expression system

The synthesis of complex biological structures such as antibodies using recombinant DNA technology is a major biotechnological advance. Active murine antibody (IgG) oligomers, composed of two heavy (H) and two light (L) polypeptide chains, have been expressed and secreted by the baculovirus-insect cell expression system. Unfortunately, expression of the functional antibodies is accompanied by the formation of abnormal protein complexes and aggregates in which the polypeptide chains are bound together into incorrect associations. The formation of these abnormal complexes or protein aggregates in insect cells may be caused by insufficient intracellular levels of two catalytic proteins, immunoglobulin binding protein (BiP or GRP78), and protein disulfide isomerase (PDI). Consequently, we obtained the genes coding for murine BiP and PDI and cloned the genes into the baculovirus vector (Autographa californica nuclear polyhedrosis virus) to obtain AcBB-BiP and AcBB-PDI. Infection of Spodoptera frugiperda (Sf-9) insect cells with these two baculoviruses yielded recombinant proteins of the correct size that were recognized by antibodies to these proteins. Cloning these genes into the baculovirus vector is one approach to engineering the assembly pathway in order to lower aggregation and increase production of functionally active proteins and oligomers.

Convenient method for studying enzyme kinetics

A convenient method for enzyme kinetic studies is introduced. The method includes identification of reaction mechanism and estimation of the associated kinetic constants with a minimum number of experiments. The application of the method is illustrated by using literature data. Factors limiting the application of this method are also discussed.