Resident perception of fundamental endoscopic skills exam: a single institution's experience

BACKGROUND

Graduating general surgery residents are required to pass the FES exam for ABS certification. Trainees and surgery educators are interested in defining the most effective methods of exam preparation. Our aim is to define trainee perceptions, performance, and the most effective preparation methods regarding the FES exam.

METHODS

General surgery residents from a single institution who completed the FES exam were identified. All participated in a flexible endoscopy rotation, and all had access to an endoscopy simulator. Residents were surveyed regarding preparation methods and exam difficulty. Descriptive statistics and a Kruskal-Wallis test were used.

RESULTS

A total of 26 trainees took the FES exam with a first-time pass rate of 96.2%. Of 26 surveys administered, 21 were completed. Twenty trainees (76.9%) participated in a dedicated endoscopy curriculum. Scores were not different among those who received dedicated curricular instruction compared to those who did not (547 [IQR 539-562.5] vs. 516 [484.5-547], p = 0.1484; 535.5 [468.5-571] vs. 519 [464.75-575], p = 0.9514). Written exam difficulty was rated as 5.5 on a 10-point Likert scale, and 85.7% felt it was a fair assessment of endoscopy knowledge; skills exam difficulty was rated as 7, and 71% felt it was a fair assessment of endoscopy skills. Online FES modules, the endoscopy clinical rotation, and an exam preparation session with a faculty member were most effective for written exam preparation. The most effective skills exam preparation methods were independent simulator practice, the endoscopy clinical rotation, and a preparation session with a faculty member. The most difficult skills were loop reduction and retroflexion. Skill decay did not appear to be significant.

CONCLUSIONS

A clinical endoscopy rotation, a method for independent skills practice, and faculty-mediated exam instruction appear to be effective exam preparation methods. When these are present, trainees report minimal need for dedicated exam preparation time prior to taking the FES exam.

Influence of clerkship sites on National Board of Medical Examiners surgery subject examination performance

BACKGROUND

As one measure of comparability of student experiences on a 2-month surgery clerkship, scores on the National Board of Medical Examiners Surgery Subject Examination (NSSE) were evaluated against a number of variables.

METHODS

NSSE scores for 701 students completing the surgery clerkship over 3.5 years were analyzed. Students rotated at academic, VA, and community hospitals with 1 month of general surgery paired with 1 month of a surgical subspecialty. The effect of 15 rotation site pairings on NSSE performance was analyzed by analysis of variance. The relationship of site-specific student evaluation variables and NSSE scores was examined by stepwise multivariate linear regression.

RESULTS

No statistical differences were demonstrated between NSSE scores and site-specific parameters of duty hours, resident participation, or type of hospital, nor between NSSE scores and paired sites constituting the overall clerkship experience.

CONCLUSION

Performance on the NSSE was not impacted by any assigned paired sites, supporting comparability of overall clerkship experiences.

Does the surgical clerkship meet the needs of practicing primary care physicians?

INTRODUCTION

A substantial amount of medical students enter primary care (PC) specialty careers. With the interest in reforming the curriculum to align the needs of our students to practice in their chosen specialties, an evaluation of our current surgical clerkship was done with the needs of PC practitioners in mind. We explored the needs of selected PC physicians in Wisconsin in relationship to the surgical clerkship curriculum.

METHODS

A survey was mailed to 186 PC physicians practicing in Wisconsin. Included in this group were internal medicine, family medicine, and pediatric physicians. One follow-up mailing and an e-mail were sent to all non-respondents. Respondents rated the importance of 10 curricular areas, including the specialties of general, orthopaedic, plastic, transplant, vascular, cardiothoracic, and pediatric surgery, as well as otolaryngology, neurosurgery, and urology. Respondents also rated the importance of exposure to 24 surgical diagnoses and identified office procedures important to PC physicians.

RESULTS

A total of 84 PC physicians responded to the survey. The highest-ranked curricular areas were general surgery, orthopaedic surgery, and otolaryngology. The 5 diagnoses that received the highest ranking from the PC physicians surveyed were abdominal pain, gastrointestinal bleeding, gastroesophageal reflux disease (GERD), biliary tract/gallbladder disorders, and breast disease, all of which are included in the general surgery curriculum. The 5 most common office procedures important to PC physicians were suturing, local anesthetic administration, dressing/wound management, wound debridement, and insertion of intravenous cannula.

CONCLUSIONS

Our survey confirmed the importance of core knowledge of general surgery and common general surgical disease processes to PC physicians. The need for additional exposure to otolaryngology and orthopaedic surgery was identified, as was as the importance of basic procedures. This information may be valuable to students interested in PC and inform the surgical clerkship curriculum in order to optimally prepare students for their chosen careers.

Multiple variables influence the educational value of surgical clerkship sites

BACKGROUND

Students' satisfaction with the educational quality of a surgical clerkship is influenced by their experiences at assigned clinical sites. We sought to identify key variables perceived by students to be associated with educationally valued clerkship sites.

METHODS

Between 1998 and 2002, third-year medical students completed a surgery site survey for each of the 2 sites on which they rotated during their required 2-month surgery rotation, representing a total of 16 sites. Students rated each site using a Likert scale on 8 educational variables as well as the overall educational value of the site. Students recorded the hours per week of direct instructional contact with attendings and, in the 2001/2002 academic year, provided narrative comments regarding site-specific strengths and weaknesses. The relationship between site variables and overall educational value across all sites was examined by stepwise multiple regression analysis. Content analysis of narrative responses was performed to surface major strengths and weaknesses associated with site-specific educational value.

RESULTS

From 1,377 completed surveys, representing an 87% completion rate, a statistically significant relationship was identified between sites' overall educational value and 6 variables. The most significant variables were as follows: "direct instructional contact with attendings in the operating room" and "quality of house staff teaching" (accounted for 33% and 13% of the total variance in educational value, respectively). Content analysis from 359 narrative responses, representing a 92% response rate, revealed 5 major categories, with operating room experience receiving the most "strength" comments (28.8%).

CONCLUSIONS

Specific variables influencing the perceived educational quality of clerkship sites can be identified. The single largest influence emerging independently from both the quantitative and qualitative analyses was the students' experiences in the operating room. Emphasis on the educational experience in the operating room should be a priority when seeking to improve the educational value of clerkship sites.

Feasibility of breast duct lavage performed by a physician extender

BACKGROUND

The safety and feasibility of ductal lavage (DL), a risk-assessment tool utilizing a minimally invasive technique that permits sampling of breast duct epithelium, performed primarily by a nurse practitioner (NP), was studied prospectively.

METHODS

Women at high risk for breast cancer with a normal clinical breast exam and mammogram were enrolled. Nipple aspirate fluid (NAF)-yielding ducts were identified, cannulated, and lavaged primarily by an NP in collaboration with a breast surgeon. Samples with sufficient cellularity were categorized as benign, mild atypia, marked atypia, or malignant. Pain and adverse events were recorded.

RESULTS

Thirty-seven women, with a mean age of 51.7 years, were enrolled. Thirty-one (83.8%) women yielded NAF and, of those, 28 (90.3%) had one or more ducts successfully cannulated. Of 65 lavaged ducts in these 28 women, cellularity was adequate for diagnosis in 44 (67.7%) samples. Cytologic findings were as follows: 24 benign, 15 mild atypia, 4 marked atypia, and 1 malignant. The procedure was well tolerated with a mean pain score of 3.2 (SD +/- 1.81). The most frequent adverse event was breast fullness, reported by 44.8% of the women. Two women with marked atypia were evaluated further and found to have intraductal papillomata. The woman with malignant cytology had ductal carcinoma in situ.

CONCLUSION

DL is a safe, generally well-tolerated procedure that can be performed successfully by a trained NP.

Sequelae of cryotherapy in breast tissue

Cryotherapy is a novel treatment for benign and malignant breast lesions that is under evaluation. We assessed the acute and subacute outcomes of breast cryotherapy in normal goat teats using physical, microscopic, and imaging modalities. Eight goats were subjected to two freeze-thaw cycles of breast tissue producing a 2cm iceball and sacrificed either 2 or 7 weeks later. Acute skin changes were minimal unless obvious tissue injury occurred during cryotherapy; however, depigmentation developed over several weeks in dark-skinned goats despite the presence of melanocytes. By histology, breast epithelial elements could not be identified at cryotherapy sites. There was no cystic degeneration, which is common at surgical excision sites. Neither calcifications nor prominent scarring could be attributed to cryotherapy on imaging studies after 2 or 7 weeks. When compared to standard breast surgery, the sequelae of cryotherapy using histologic, radiographic, and sonographic criteria were decreased. Our study suggests that cryotherapy, with technical modifications, is feasible within breast tissue and warrants further study.

A Unique Collision Tumor in Breast

We report an extraordinary case of a collision tumor consisting of invasive ductal carcinoma with adjacent malignant lymphoma presenting as a single mass in the breast. A 79-year-old woman presented with a breast mass. A core biopsy performed at an outside hospital was interpreted as medullary carcinoma. On review of the breast core biopsy, a diagnosis of a synchronous malignant lymphoma and invasive ductal carcinoma was rendered. The patient underwent lumpectomy and axillary dissection. The excised specimen revealed a 2.1-cm, moderately differentiated invasive ductal carcinoma, partially surrounded by malignant lymphoma with areas where both tumors were intermixed. All 27 axillary lymph nodes were extensively involved by lymphoma, and 1 lymph node demonstrated metastatic carcinoma. The morphology and results of immunohistochemistry, flow cytometry, and cytogenetic analysis were consistent with extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue.

Does breast tumor location influence success of sentinel lymph node biopsy?

BACKGROUND

Controversy exists regarding the influence of sentinel lymph node (SLN) mapping technique or patient variables on the success rate of SLN mapping. We undertook a prospective study in a single institution series to evaluate multiple variables that could adversely affect SLN identification rates.

STUDY DESIGN

Data were collected on 174 patients who underwent 177 SLN mapping procedures followed by axillary dissection from October 1996 through January 2000. Patient demographics, body mass index (BMI), biopsy method, tumor size, palpability, and location were recorded. SLNs were identified by blue dye only (n = 31), Tc-99m sulfur colloid only (n = 34), or combined techniques (n = 112). Data were analyzed by logistic regression analysis and expressed as the probability of failure to map the SLN.

RESULTS

SLNs were identified successfully in 150 of 177 procedures (85%) with a false negative rate of 3.7%. Mapping success reached 93% using combination blue dye and isotope. Variables found to adversely affect SLN mapping success and the odds ratio of failure (OR) included lower inner quadrant (LIQ) location (OR 35.6), blue dye only (OR 42.4), BMI >30 and upper outer quadrant (UOQ) location (OR 14.6), and nonpalpable UIQ location (OR 25). LIQ location adversely affects mapping success independent of technique, tumor size, or obesity. Obesity and nonpalpability were adverse factors when tumors were located in the UOQ and UIQ, respectively. Age, biopsy technique, and tumor diameter did not affect SLN mapping success.

CONCLUSIONS

SLN mapping success is influenced by technique and tumor location, with best results achieved using combined techniques and for lesions located in quadrants other than the LIQ. Obesity and tumor palpability influence success in the context of tumor location.

Mapping of IFN-beta epitopes important for receptor binding and biologic activation: comparison of results achieved using antibody-based methods and alanine substitution mutagenesis

The epitopes important for receptor binding and activation of human interferon-beta1a (IFN-beta1a) were mapped with monoclonal antibodies (mAb), grouped on the basis of their specificity and ability to neutralize biologic activity, and alanine scanning mutagenesis (ASM). The binding properties of nine mAb were defined, using ASM-IFN-beta mutants having alanine substituted at targeted, surface-exposed residues. The results were correlated with the mAb neutralizing potency. Of six mAb that bound either at or adjacent to the IFNAR-2 receptor chain binding site defined by the ASM epitopes, only three had measurable neutralizing activity. Two of these inhibited IFN-beta/IFNAR-2 complex formation, suggesting that steric hindrance of receptor binding constitutes their mechanism of neutralization. However, two mAb that bound to sites remote from the IFNAR-2 binding site on IFN-beta also inhibited IFN-beta/IFNAR-2 complex formation and demonstrated potent neutralizing activity. Thus, neutralizing mAb may employ mechanisms other than steric blockade to inhibit directly the binding of receptor by cytokine, limiting their usefulness as tools to define precise receptor-ligand interaction sites.

Quantitative liquid-phase chemiluminescence ELISA: detection of subtle epitope differences in HuIFN-beta

We have developed a new liquid-phase, chemiluminescence-enhanced, inhibition ELISA (LP-CEI-ELISA) to explore the binding sites recognized by two neutralizing monoclonal antibodies (mAb) against recombinant human IFN-(beta)ser (rHuIFN-(beta)ser). In this assay, the initial antigen-antibody reaction occurs in solution under more physiologic conditions than in a standard solid-phase ELISA. Subsequently, the reaction mixture is applied to a membrane that is exposed to a second, peroxidase-labeled mAb, chemiluminescent reagents are added, and the membrane is photographically recorded. Competitive inhibition of binding of a second, labeled mAb by the first mAb decreases the signal detected. Two well-characterized mAb A1 and A7, have been shown to recognize distinct epitopes on rHuIFN-(beta)ser and to neutralize its antiviral and antiproliferative activity (Proc. Natl. Acad. Sci. USA 88, 4040-4044, 1991). In conventional solid-phase ELISA, mAb A1 does not inhibit the binding of A7 to rHuIFN-(beta)ser, but we observed partial inhibition in the new liquid-phase assay. In contrast, A7 did not inhibit the binding of A1, consistent with the solid-phase ELISA results. This observation suggests that in the LP-CEI-ELISA, A1 and A7 may recognize epitopes differently than in solid-phase assays. Thus, the LP-CEI-ELISA, which is simple, sensitive, and quantifiable, appears also to be able to detect subtle, conformational differences of epitopes not evident in a standard solid-phase ELISA.

Acquisition of surgical skills: a randomized trial of didactic, videotape, and computer-based training

BACKGROUND

Although computer-based training (CBT) can enhance didactic instruction, few studies have assessed the efficacy of CBT for basic surgical skills training. This study compares CBT with traditional methods of basic surgical skills training.

METHODS

Sixty-nine naive medical students were randomized into 3 treatment groups for basic surgical skills instruction: didactic, videotape, or CBT. All instructional material contained the same pictures, text, and audio. With use of a multiple-choice question examination and a series of performance stations, students were objectively assessed before, immediately after, and 1 month after skills instruction. Raters were blinded to treatment modality during the follow-up evaluation.

RESULTS

There were no significant differences among the groups before treatment. After treatment, the didactic group scored higher on the multiple-choice question examination. In contrast, the videotape and CBT groups demonstrated statistically significant (P < .01) enhancement of technical skills compared with the didactic group. After 1 month, a calculated performance quotient revealed statistically significant (P < .01) improvement only in the CBT group. The amount of time students spent practicing their skills was not significantly different among the groups.

CONCLUSIONS

CBT is as effective as, and possibly more efficient, than traditional methods of basic surgical skills training for medical students.

Molecular metastases in stage I pancreatic cancer: improved survival with adjuvant chemoradiation

BACKGROUND

Reports of improved survival rates for patients with resected adenocarcinoma of the pancreas coincide with the adoption of adjuvant chemoradiation protocols. The impact of nodal micrometastases demonstrated by molecular assays and adjuvant therapy on survival of patients with stage I pancreatic cancer has not been adequately assessed.

METHODS

A retrospective analysis of postoperative chemoradiation on survival in 61 patients undergoing resection of pancreatic adenocarcinomas from 1984 to 1997 was performed. Archival tumors and regional nodes from 25 patients with stage I cancers were tested for a Kiras oncogene mutation using polymerase chain reaction and analysis for restriction fragment length polymorphisms (PCR/RFLP).

RESULTS

Adjuvant chemoradiation was associated with improved survival for stage I (P < .01), but not stage III, disease. Seventeen (68%) of 25 patients with stage I disease tested had evidence of mutant Kiras in one or more regional nodes. Survival did not differ for patients with molecular micrometastases. Six of 17 (35%) patients with micrometastases received adjuvant chemoradiation and had improved survival (P < .05).

CONCLUSIONS

The majority of patients with stage I pancreatic cancer have PCR/RFLP evidence of lymph node micrometastases. Adjuvant chemoradiation improves survival in these patients by treating micrometastases not detected by histology. Adjuvant chemoradiation should be used for patients with stage I pancreatic cancers.

Carcinoma of the breast in males: a multiinstitutional survey

BACKGROUND

Breast carcinoma in males is infrequent, and information regarding the results of modern treatment is limited. Cases of breast carcinoma in males were accrued from multiple hospitals in one region to determine treatment, survival, and prognostic factors.

METHODS

A retrospective review was performed of 217 cases of breast carcinoma in males accessioned at tumor registries of 18 health care institutions in eastern Wisconsin between 1953 and 1995.

RESULTS

Of the 217 cases, 215 (99.1%) were carcinomas. The majority of carcinomas were of invasive ductal type and presented as masses. Carcinoma in situ accounted for 5.5% of cases. The 5- and 10-year observed survivals for men were 50.6% and 23.7%, respectively. A high rate of post-treatment mortality from comorbid disease was found. Stage, axillary lymph node status, number of lymph nodes with metastases, and tumor hormone receptors were significant indicators of prognosis. Adjuvant systemic chemotherapy and hormone therapy improved the prognosis of patients with axillary lymph node metastases and hormone receptor positive tumors. Earlier stage at presentation and improved 5-year survival were found in cases occurring between 1986-1995 compared with those occurring in earlier years. Use of modified radical mastectomy and systemic adjuvant therapy also increased since 1986.

CONCLUSIONS

The clinical, pathologic, and prognostic features of breast carcinoma in men are similar to those reported for women. The poorer prognosis of men is related to older age at diagnosis, more advanced stage of disease at presentation, and high mortality from comorbid disease. Earlier diagnosis, less radical surgery, and use of systemic adjuvant therapy are coincident with an improved prognosis for men.

Surgical management of colorectal metastases to the liver: role of resection and cryosurgery

Long-term results of 41 patients who underwent hepatic resection and early experience with 21 patients treated by hepatic cryosurgery alone or combined with resection for colorectal metastases are presented. Patients treated by resection had three or fewer metastases, no perioperative mortality, and a mean follow-up of 43.5 months. The five-year overall survival is 34% with a median survival of 48 months. By multivariate analysis, only transfusions correlated significantly with survival, but in a negative manner (p = 0.05). A mean of 4.3 units were transfused per patient, though only 25 patients actually received transfusions.

Breast cancer in men

Aside from its much lower frequency, breast cancer in men is remarkably similar to the disease in women. The cause remains equally obscure; the clinical presentation, pathology, and natural history are similar; and men are probably as curable in similar circumstances. Men are generally older and in more advanced stages than women when diagnosed, the tumors are located more often beneath the nipple and are more often responsive to hormonal therapy, but otherwise differences are negligible. Stage and axillary node status are strong prognostic indicators. Modified radical mastectomy has replaced radical mastectomy for surgical treatment of early states, and systemic adjuvant therapy appears to improve the prognosis for cases with involvement of lymph nodes.

Primary squamous cell carcinoma of the breast: sensitivity to cisplatinum-based chemotherapy

Primary squamous cell carcinoma (SCC) of the breast is a rare malignancy whose optimal treatment and prognosis are unknown. A patient with SCC whose tumor responded dramatically to chemotherapy as part of multimodal treatment is presented. A 61-year-old woman had a palpable 5.5-cm tender left breast mass with overlying skin edema and erythema and irregular margins by mammography. Fine needle aspiration revealed malignant squamous cells with keratinization; incisional biopsy confirmed SCC. Extensive evaluation for an extramammary primary site of disease was negative. Neoadjuvant cisplatinum and 5-fluorouracil (5-FU) led to tumor shrinkage and complete resolution of pain and erythema. Modified radical mastectomy with post-operative chest wall radiation were performed. Neither residual invasive carcinoma nor metastatic nodal disease was found, though intraductal carcinoma with marked squamous features was identified. The patient remains disease-free 2.5 years after diagnosis. Cisplatinum-based chemotherapy should be considered in the treatment regimen of this disease.

Clostridium difficile toxin A therapy for HCT 116 human colon cancer in nude mice

Clostridium difficile toxin A was evaluated for an antitumor effect in vivo on HCT 116 human colon carcinoma cells growing subcutaneously in nude mice. A mean reduction in tumor volume of at least 65%, by measurement in three dimensions, was observed in mice who received two 9- to 13-day courses of daily intraperitoneal injections of toxin A as compared to mice receiving diluent alone. Reversible adverse effects of toxin A were noted in some animals, consisting primarily of liver toxicity and skin rash. HCT 116 cells in toxin A-treated mice grew as flattened tumors with ulcerated centers compared to rounded tumors without ulceration in controls. Histologic examination of tumors from representative mice revealed that two thirds of the tumor in a treated mouse was necrotic compared to only one third in a control, suggesting greater antitumor efficacy of toxin A than estimated by tumor measurements alone.

Trends in the stage of cancer at the time of diagnosis

The stage of cancers at the time of diagnosis for 10 major sites of disease from patients treated at two Medical College of Wisconsin teaching hospitals was analyzed from tumor registry data and compared from the years 1983, 1987, and 1991. A trend toward earlier stages of cancer of major sites was noted, with patients having in situ or localized disease increasing from 35% in 1983 to 48% in 1991. Patients with breast cancer demonstrated the strongest trend, with 44% of the cases representing in situ or localized disease in 1983 compared to 61% in 1991 (p = 0.03). A shift toward earlier stage of cancer at diagnosis was also noted for other major sites including: lung, trachea and bronchus; colon and rectum; and prostate cancers. Trends toward an earlier stage of cancer may result from patient and physician education, local practice patterns, as well as proper use of screening programs. Information on such trends from hospital tumor registries may be helpful in the appropriate and efficient allocation of local health care resources.

Cytotoxicity of Clostridium difficile toxin A for human colonic and pancreatic carcinoma cell lines

The use of bacterial exotoxins may constitute novel adjuncts to treatment of gastrointestinal tract malignancies. Clostridium difficile toxin A was evaluated for its cytotoxic effect in vitro on 24 human cell lines and strains including carcinomas of the colon, pancreas, prostate, lung, breast, and lymphoid malignancies, as well as nonmalignant tissues. All nine colon and five pancreas cell lines were extraordinarily sensitive to the cytotoxic effect of Clostridium difficile toxin A at very low concentrations. This effect, which occurred rapidly and was dose dependent, was observed in all cells of seven colon and two pancreas cell lines at concentrations as low as 1-5 ng/ml (10(-12) to 10(-11) M), whereas cells derived from other sites required 60 to greater than 500 ng/ml to achieve an equivalent effect. The data suggest that Clostridium difficile toxin A may have potential therapeutic value in the treatment of some gastrointestinal tract cancers.

Antibodies that neutralize human beta interferon biologic activity recognize a linear epitope: analysis by synthetic peptide mapping

The location of biologically relevant epitopes on recombinant human beta interferon in which Ser-17 replaces Cys-17 (rh[Ser17]IFN-beta) was evaluated by testing the immunoreactivity of antibodies against 159 sequential, overlapping octamer peptides. Three monoclonal antibodies (mAbs) that neutralize rh[Ser17]IFN-beta biologic activity, designated A1, A5, and A7, bound to peptides spanning only residues 39-48, whereas nonneutralizing mAb bound less specifically at multiple sites near the amino terminus. The immunoreactivity of peptides spanning residues 40-47 that contained a series of single amino acid substitutions suggested that residues 41-43 (Pro-Glu-Glu) and 46 (Gln) are important for the binding of neutralizing mAbs. The reactivity of mAbs to larger synthetic peptides containing rh[Ser17]IFN-beta sequences from residue 32 through residue 56 was evaluated. All mAbs except A7 reacted with synthetic peptides representing rh[Ser17]IFN-beta residues 32-47, 40-56, and 32-56, but only mAbs A1 and A5 bound to the core peptide composed of residues 40-47. Peptide 32-56 effectively blocked the binding of mAbs A1 and A5 to rh[Ser17]IFN-beta and markedly inhibited their neutralizing activity. Biologic activity of the peptides was undetectable. Rabbit antisera raised against peptides 32-47 and 40-56 recognized rh[Ser17]IFN-beta but did not neutralize its antiviral activity. Thus, structure-function analysis by peptide mapping has permitted the identification of a linear epitope recognized by neutralizing antibody on a biologically active cytokine. We conclude that the region spanning residues 32-56 is of major importance in the expression of the biologic activity of human IFN-beta.

Immunochemical characterization of antigenic domains on human interferon-beta: spatially distinct epitopes are associated with both antiviral and antiproliferative activities

The use of a panel of monoclonal antibodies (mAb) raised against recombinant (serine-17) human interferon-beta (rHuIFN-beta ser) has permitted the identification of three epitopes on HuIFN-beta, designated as sites I, II and III, based solely on functional differences, i.e., the neutralization of antiviral and antiproliferative activities of natural and recombinant HuIFN-beta (Redlich, P.N. and Grossberg, S. E., J. Immunol. 1989. 143: 1887). Site I- and II-directed mAb possessed neutralizing activity whereas none was noted by mAb recognizing site III. To characterize further these epitopes by immunochemical means, we studied their (a) spatial relationship by competitive binding assays, (b) antigenic structure by Western blotting, and (c) sensitivity to chemical modification by the measurement of mAb reactivity after radioiodination. Competitive antibody binding studies revealed site II to be spatially distinct from sites I and III. Furthermore, site I- and II-directed mAb could easily recognize rHuIFN-beta ser on a Western blot, suggesting that both these epitopes are primarily sequential in structure or denaturation resistant. Chemical modification by radioiodination, which did not alter the biologic activity of rHuIFN-beta ser, had likewise little effect on mAb reactivity to site I; however, reactivity to site II was diminished and reactivity to site III was minimal following the radioiodination process. Both site I- and II-directed mAb inhibited the binding of 125I-rHuIFN-beta ser to intact Daudi cells, suggesting that inhibition of receptor binding is their mechanism of neutralization. Thus, we conclude that epitopes I and II, which are associated with both antiviral and antiproliferative activities of rHuIFN-beta, are spatially and immunochemically distinct.

Analysis of antigenic domains on natural and recombinant human IFN-beta by the inhibition of biologic activities with monoclonal antibodies

Human IFN-beta (HuIFN-beta) is a biologically potent protein with both antiviral and antiproliferative activities. To understand better its mode of action, a number of murine mAb were developed against a recombinant (serine-17) HuIFN-beta (rHuIFN-beta ser) and screened by ELISA and neutralization of antiviral activity. The panel of antibodies, composed of both IgA and IgG immunoglobulins, were specific for HuIFN-beta and did not crossreact with HuIFN-alpha or gamma. Furthermore, three functionally distinct epitopes (designated as sites I, II, and III) were identified based on mAb neutralization of antiviral and antiproliferative activities of recombinant and natural HuIFN-beta. Antibodies directed to sites I and II neutralized the antiviral and antiproliferative activities of rHuIFN-beta ser, though the antiviral neutralization potency of the mAb to site II was approximately 10-fold less than mAb to site I. Antibodies directed to site I neutralized both recombinant and natural HuIFN-beta, although the antiviral neutralization potency was approximately 10-fold higher against rHuIFN-beta ser than the native protein. The mAb directed to site II did not demonstrate any significant neutralization of the antiviral or antiproliferative activity of natural HuIFN-beta but neutralized a recombinant HuIFN-beta containing the native sequence. Antibodies recognizing site III did not neutralize the biologic activity of either recombinant or natural HuIFN-beta. Thus, three epitopes on HuIFN-beta have been identified, two of which are associated with both antiviral and antiproliferative activities.

Analysis of antigenic domains on natural and recombinant human IFN-beta by the inhibition of biologic activities with monoclonal antibodies

Human IFN-beta (HuIFN-beta) is a biologically potent protein with both antiviral and antiproliferative activities. To understand better its mode of action, a number of murine mAb were developed against a recombinant (serine-17) HuIFN-beta (rHuIFN-beta ser) and screened by ELISA and neutralization of antiviral activity. The panel of antibodies, composed of both IgA and IgG immunoglobulins, were specific for HuIFN-beta and did not crossreact with HuIFN-alpha or gamma. Furthermore, three functionally distinct epitopes (designated as sites I, II, and III) were identified based on mAb neutralization of antiviral and antiproliferative activities of recombinant and natural HuIFN-beta. Antibodies directed to sites I and II neutralized the antiviral and antiproliferative activities of rHuIFN-beta ser, though the antiviral neutralization potency of the mAb to site II was approximately 10-fold less than mAb to site I. Antibodies directed to site I neutralized both recombinant and natural HuIFN-beta, although the antiviral neutralization potency was approximately 10-fold higher against rHuIFN-beta ser than the native protein. The mAb directed to site II did not demonstrate any significant neutralization of the antiviral or antiproliferative activity of natural HuIFN-beta but neutralized a recombinant HuIFN-beta containing the native sequence. Antibodies recognizing site III did not neutralize the biologic activity of either recombinant or natural HuIFN-beta. Thus, three epitopes on HuIFN-beta have been identified, two of which are associated with both antiviral and antiproliferative activities.