A Retrospective Multicenter Italian Analysis of Epidemiological, Clinical and Histopathological Features in a Sample of Patients with Acinic Cell Carcinoma of the Parotid Gland

BACKGROUND

The acinic cell carcinoma (AciCC) of the parotid gland is a rare tumor with an indolent behavior; however, a subgroup of this tumor presents an aggressive behavior with a tendency to recur. The aim of this multicenter study was to identify and stratify those patients with AciCC at high risk of tumor recurrence.

METHODS

A retrospective study was carried out involving 77 patients treated with surgery between January 2000 and September 2022, in different Italian referral centers. Data about tumor characteristics and its recurrence were collected. The histological specimens and slides were independently reviewed by a senior pathologist coordinator (L.C.) and the institution's local head and neck pathologist.

RESULTS

The patients' age average was 53.6 years, with a female prevalence in the group. The mean follow-up was 67.4 months (1-258, SD 59.39). The five-year overall survival (OS) was 83.2%. The 5-year disease-free survival (DFS) was 60% (95% CI 58.2-61.7). A high incidence of necrosis, extraglandular spread, lymphovascular invasion (LVI), atypical mitosis, and cellular pleomorphism was observed in the high-risk tumors compared to the low-risk ones.

CONCLUSION

AciCC generally had an indolent behavior, optimal OS, DFS with few cervical node metastases, and rare distant relapses. This multicenter retrospective case series provides evidence of the need for clinical-epidemiological-histological stratification for patients at risk of poor outcomes. Our results suggest that the correct definition of high-risk AciCC should include tumor size, the presence of necrosis, extraglandular spread, LVI, atypical mitosis, and cellular pleomorphism.

Parapharyngeal space tumors: a twenty-year single-center retrospective analysis on the effectiveness of transcervical and transoral approaches on local control and disease-specific survival

INTRODUCTION

To retrospectively analyzed our twenty-years single-center experience in the treatment of PPS tumors, focusing on the selection of surgical approach and the survival outcome.

METHODS

Tumors involving the PPS between January 2000 and February 2022 were retrospectively included. The surgical approach was dictated by the localization of the tumor, its dimensions, the relation to anatomic structures and its etiology.

RESULTS

34 patients were included in the study. The median age was 50.5 yr, with a gender female prevalence. Most tumors were benign and non recurrent. 20 tumors were treated through lateral approach (transcervical or transcervical-transparotid), 11 through medial approach (transoral), and only 3 tumors were approached by multiple corridors. The 5 years disease free survival (DFS) was 78.8 % (CI 78-79.3 %).

CONCLUSIONS

In our experience, the transcervical and transoral approaches can be considered the ideal surgical approach to manage tumors of PPS, especially in cases of benign neoplasms.

Bilateral Post-Traumatic Facial Palsy: A Case Report and Literature Review

INTRODUCTION

Bilateral facial nerve (FN) palsy due to temporal bone fracture is a rare clinical entity, with few cases reported. The choice between conservative and surgical treatment is more complex than in unilateral cases.

MATERIALS AND METHODS

A thorough search of the available literature on trauma-related bilateral FN palsy revealed 22 reports. Our own experience is also described.

RESULTS

All bilateral delayed- and unknown-onset cases were treated conservatively, with a good recovery rate (70.5%). Surgery was performed on 6 sides within the immediate-onset group, with a good recovery rate (83.3%).

CONCLUSIONS

In the management of traumatic FN palsy, the main controversial issue focusses on indications for surgery as well as timing and type of approach. In bilateral cases, it is more challenging to make the right choice, due to lack of facial asymmetry and/or state of unconsciousness following severe trauma. Electro-diagnostic tests and high-resolution computed tomography are essential for decision-making.

A surgical challenge: resection of giant follicular thyroid carcinoma in a 92-year-old woman. Case report and considerations on thyroid surgery in geriatric population

The aim of this paper is to present the clinical features and the diagnostic and surgical management of a 92-year-old patient with giant goiter. She was admitted to our Emergency Department for evaluation of a cervical mass increased in volume over the past five years. She complained of mild dyspnea pressure symptoms in the neck. Neck and mediastinal noncontrast computed tomography showed a huge goiter with a clear prominent right thyroid lobe, with external compression of the trachea. Consequently, she underwent a right thyroid lobectomy. Patient followed up closely; she is asymptomatic with no evidence of recurrence on RAI scan at the end of six months follow-up. In conclusion, the treatment choice for elderly patients with FTC should be based on medical assessments; in these patients, especially those with larger goiter and compressive symptoms, surgery is the first choice. KEY WORDS: Elderly, Emergency Surgery, Follow up, Thyroid carcinoma, Thyroid lobectomy.

Multicentre study on resection margins in carcinoma of the oral cavity, oro-hypopharynx and larynx

Objective

The prognostic significance of the resection margins is still subject of conflicting opinions. The purpose of this paper is to report the results of a study on the margins in carcinoma of the oral cavity, oro-hypopharynx and larynx.

Methods

A multicentre prospective study was carried out between 2015 and 2018 with the participation of 10 Italian reference hospitals. The primary objective was to evaluate local control in patients with well-defined clinical characteristics and comprehensive histopathological information.

Results

During the study period, 455 patients were enrolled; the minimum follow-up was 2 years. Previous treatment, grading and fresh specimen examination were identified as risk factors for local control in multivariate analysis. On the basis of these results, it seems possible to delineate “risk profiles” for different oncological outcomes.

Discussion

The prognostic significance of the margins is reduced, and other risk factors emerge, which require diversified treatment and follow-up.

Conclusions

Multidisciplinary treatment with adjuvant therapy, if indicated, reduces the prognostic importance of margins. Collaboration with a pathologist is an additional favourable prognostic factor and quality indicator.

An appendix with literature review is present in the online version.

Acinic cell carcinoma of the parotid gland: Timeo Danaos et dona ferentes? A multicenter retrospective analysis focusing on survival outcome

OBJECTIVES

To analyze the demographic data, surgical and adjuvant treatment data and the survival outcomes in adult patients affected by acinic cell carcinoma of the parotid gland (AciCC).

METHODS

A retrospective multicenter analysis of patients treated for AciCC of the parotid gland from 2000 to 2021 was performed. Exclusion criteria were pediatric (0-18 years) patients, the absence of follow-up and patients with secondary metastatic disease to the parotid gland. Multivariable logistic regression was used to determine factors associated with survival.

RESULTS

The study included 81 adult patients with AciCC of the parotid gland. The median age was 46.3 years (SD 15.81, range 19-84 years), with a gender female prevalence (F = 48, M = 33). The mean follow-up was 77.7 months (min 4-max 361, SD 72.46). The 5 years overall survival (OS) was 97.5%. The 5 years disease-free survival (DFS) was 60%. No statistical differences have been found in prognosis for age (< 65 or ≥ 65 years), sex, surgery type (superficial vs profound parotid surgery), radicality (R0 vs R1 + Rclose), neck dissection, early pathologic T and N stages and adjuvant therapy (p > 0.05).

CONCLUSION

This study did not find prognostic factor for poorest outcome. In contrast with the existing literature, our results showed how also high-grade tumours cannot be considered predictive of recurrence or aggressive behaviour.

Health-Related Quality of Life in Patients With ANCA-Associated Vasculitis and Sinonasal Involvement: A Single-Center Cross-Sectional Study

BACKGROUND/OBJECTIVE

The aim of this study was to assess the impact of sinonasal morbidity on quality of life (QoL) in antineutrophil cytoplasmic antibody-associated vasculitis (AAV).

METHODS

This cross-sectional case-control study enrolled 71 patients-44 AAV cases with (ear, nose, and throat [ENT]-AAV) or without ENT involvement (non-ENT-AAV) undergoing multidisciplinary evaluations and 27 chronic rhinosinusitis (CRS) cases. Three validated QoL questionnaires (Sino-Nasal Outcomes Test-22 [SNOT-22], Nasal Obstruction Symptom Evaluation [NOSE], and Short-Form 36) were administered, and the 3 groups were compared.

RESULTS

The ENT-AAV patients were significantly younger (p = 0.01), with less antineutrophil cytoplasmic antibody positivity frequency (p = 0.035) and lower renal involvement (p = 0.003) than the non-ENT-AAV patients.The SNOT-22 questionnaire demonstrated significantly greater sinonasal morbidity in ENT-AAV patients compared with CRS patients (p < 0.001). The NOSE score of ENT-AAV patients was comparable to those of CRS patients, but higher than that of non-ENT-AAV patients (p < 0.001). The SNOT-22 and NOSE scores positively correlated with disease activity (p = 0.037; p = 0.004, respectively). Short-Form 36 domain-by-domain analysis revealed a significantly poorer QoL in ENT-AAV patients, especially with physical functioning being progressively impaired in CRS, non-ENT-AAV, and ENT-AAV patients (p < 0.001). No significant differences in QoL came to light when AAV patients were stratified according to current systemic o local treatments.

CONCLUSIONS

The QoL in AAV patients is significantly reduced, especially in the presence of ENT involvement. The AAV-related nasal morbidity is consistent and comparable to that reported by CRS patients. It significantly affects patients' QoL and in particular social functioning, leading to limitation in daily/work activities. Organ-focused questionnaires and multidisciplinary management are warranted to pursue a treat-to-target approach in these patients.

Prognostic indicators in clinically node-negative malignant primary salivary tumours of the parotid: A multicentre experience

OBJECTIVES

Nodal metastasis is an important prognosticator in primary parotid cancers. The management of the clinically node-negative neck is an area lacking consensus. This study investigates the occult nodal metastasis rate, and prognostic indicators in primary parotid cancers.

MATERIALS AND METHODS

We performed a multicentre retrospective case note review of patients diagnosed and treated surgically with curative intent between 1997 and 2020. Demographic, clinic-pathological and follow-up data was recorded.

RESULTS

After exclusions, 334 patients were included for analysis, with a median follow-up of 48 months. The overall rate of occult lymph node metastasis amongst patients undergoing elective neck dissection was 22.4%, with older age, high-grade and more advanced primary tumours being associated with higher rates. On multivariable analysis, age ≥ 60 years (HR = 2.69, p = 0.004), high-grade tumours (HR = 2.70, p = 0.005) and advanced primary tumours (pT3-4, HR = 2.06, p = 0.038) were associated with worse overall survival. Occult nodal metastasis on final pathology was associated with a close-to-significant reduction in regional recurrence free survival (HR = 3.18, p = 0.076).

CONCLUSION

This large series confirms the significant occult lymph node metastasis rate in primary parotid cancer, and demonstrates the importance of primary histology, tumour grade and stage in predicting survival outcome. This data supports the use of elective neck dissection in patients with high-risk tumours.

Clivus Chordoma: Case Report and Current Considerations on Treatment Strategies

Chordomas are the rare malignant bone lesions derived from the embryonic notochord. They are slow-growing tumors with a locally aggressive behavior. The clival chordomas are extradural, exophytic, and lytic lesions centered on the clivus, and are managed differently from those arising elsewhere because of the emphasis on preserving the neurological function. The gold standard for therapy is the complete resection followed by radiation therapy for a better local control of the tumor. This case report concerns a 20-year old girl with an incidental diagnosis of the clival chordoma, which was first treated via an endoscopic anterior approach to remove the exophytic portion of the tumor. The adjuvant radiation therapy was not feasible because of the macroscopic intradural residual tumor being at the level of jugular foramen. The girl was referred to our institute for the removal of the intradural residual tumor via a petro-occipital trans-sigmoid (POTS) approach followed by adjuvant proton beam therapy. The choice of the surgical approach depends on the size of the tumor, its location, and its anatomical distribution, but should also be balanced against the morbidity, considering the patient's age, and the feasibility of postoperative rehabilitation.

Seborrheic Keratosis or Squamous Carcinoma? Clinical Examination versus Biopsy: The Importance of Criticism

We compare the results of clinical observation and histopathology analysis for developing a differential diagnosis of seborrheic keratosis (SK) of the external auditory canal (EAC). A 46-year-old man with a history of a recurrent lesion in the EAC underwent clinical observation of the skin lesion's appearance, computed tomography (CT) scan, magnetic resonance imaging (MRI), and several biopsies. Initially, a benign form of SK was diagnosed based on several biopsies performed over a 10-year period. The lesion's appearance was consistent with a malignant disease, which led the clinician to perform a CT scan and an MRI scan. The patient underwent partial petrosectomy to completely remove the lesion as CT and MRI scans showed an infiltrative process. Squamous carcinoma was the final histological diagnosis. The patient was disease free at 1 year of follow-up after petrosectomy. In conclusion, if there are inconsistencies between clinical observation and histological report, additional tests should be performed to exclude the malignity of a lesion.

Surgery of the lateral skull base: a 50-year endeavour

Disregarding the widely used division of skull base into anterior and lateral, since the skull base should be conceived as a single anatomic structure, it was to our convenience to group all those approaches that run from the antero-lateral, pure lateral and postero-lateral side of the skull base as “Surgery of the lateral skull base”. “50 years of endeavour” points to the great effort which has been made over the last decades, when more and more difficult surgeries were performed by reducing morbidity. The principle of lateral skull base surgery, “remove skull base bone to approach the base itself and the adjacent sites of the endo-esocranium”, was then combined with function preservation and with tailoring surgery to the pathology. The concept that histology dictates the extent of resection, balancing the intrinsic morbidity of each approach was the object of the first section of the present report. The main surgical approaches were described in the second section and were conceived not as a step-by-step description of technique, but as the highlighthening of the surgical principles. The third section was centered on open issues related to the tumor and its treatment. The topic of vestibular schwannoma was investigated with the current debate on observation, hearing preservation surgery, hearing rehabilitation, radiotherapy and the recent efforts to detect biological markers able to predict tumor growth. Jugular foramen paragangliomas were treated in the frame of radical or partial surgery, radiotherapy, partial “tailored” surgery and observation. Surgery on meningioma was debated from the point of view of the neurosurgeon and of the otologist. Endolymphatic sac tumors and malignant tumors of the external auditory canal were also treated, as well as chordomas, chondrosarcomas and petrous bone cholesteatomas. Finally, the fourth section focused on free-choice topics which were assigned to aknowledged experts. The aim of this work was attempting to report the state of the art of the lateral skull base surgery after 50 years of hard work and, above all, to raise questions on those issues which still need an answer, as to allow progress in knowledge through sharing of various experiences. At the end of the reading, if more doubts remain rather than certainties, the aim of this work will probably be achieved.

The diagnostic value of cytology in parotid Warthin's tumors: international multicenter series

INTRODUCTION

Warthin's tumor (WT) is a common benign salivary gland neoplasm with a negligible risk of malignant transformation. However, there is a risk of malignant tumors being misdiagnosed as WT on cytology and inappropriately managed conservatively.

METHODS

Patients from nine centers in Italy and the United Kingdom undergoing parotid surgery for cytologically diagnosed WT were included in this multicenter retrospective series. Definitive histology was compared with preoperative cytological diagnoses. Surgical complications were recorded.

RESULTS

A total of 496 tumors were identified. In 88.9%, the final histological diagnosis was WT. In 21 cases (4.2%) a malignant neoplasm was diagnosed, which had been incorrectly labeled as WT on cytology.

CONCLUSIONS

The risk of undiagnosed malignancy should be balanced against surgical risks when considering the management of WT. Although nonsurgical management remains an appropriate option, there may be a rationale for serial clinical or radiological evaluation if surgical excision is not performed.

Can unilateral, progressive or sudden hearing loss be immune-mediated in origin?

OBJECTIVE

The aim of the present study was to demonstrate that the positivity of nonspecific immunological tests could be found not only in bilateral hearing loss but also in unilateral cases, either sudden or progressive.

METHOD

An observational case series study included subjects suffering from unilateral or bilateral, sudden or progressive, symmetric or asymmetric sensorineural hearing loss (SNHL). All the patients underwent pure tone audiometry and the following battery of blood exams: anti-nuclear antibody (ANA), extractable nuclear antigen (ENA) antibody screening, anti-thyroperoxidase (anti-TPO), anti-thyroglobulin and anti-smooth muscle antibody (ASMA).

RESULTS

The positivity to nonspecific immunological test was found in nearly 70% of the study groups. ASMA and ANA were found to be present in both bilateral and unilateral cases, without statistical difference. Considering the correlation between positivity/negativity and systemic autoimmune pathologies, in the bilateral forms of hearing loss, a high incidence of thyroid pathologies has been identified, with a higher percentage of systemic autoimmune diseases in respect to the normal population.

CONCLUSIONS

The nonspecific autoimmune tests are worth to be performed also when SNHL is not bilateral and progressive, since an immunological mechanism could also underlie unilateral and sudden SNHL cases.

Immunological characterization of antigens encoded by the RD1 region of the Mycobacterium tuberculosis genome

Development of immunoassays specific for the diagnosis of tuberculosis requires antigens unique to Mycobacterium tuberculosis. In a search for such antigens we tested six proteins encoded by RD1, a region present in M. tuberculosis and virulent M. bovis genomes but missing from the DNA of all substrains of M. bovis Bacillus Calmette-Guerin (BCG). The six proteins (Rv3871, Rv3872, Rv3873, MTSA-10, ESAT-6 and Rv3878) were purified to near-homogeneity from recombinant Escherichia coli. When tested for the ability to elicit antibody responses and delayed type hypersensitivity in tuberculous guinea pigs, only two of six antigens, ESAT-6 and MTSA-10, elicited strong skin reactions, while vigorous antibody responses were observed to all six proteins. When antibody responses to RD1 antigens were evaluated in sera from patients having pulmonary tuberculosis and from control subjects (patients having mycobacterioses other than tuberculosis, and healthy persons), a sizeable proportion (25%) of tuberculosis patients but none of the control subjects, had antibodies against MTSA-10 and/or ESAT-6. We conclude that MTSA-10 and ESAT-6 are promising candidates for immunodiagnostic assays specific for tuberculosis.

A multi-antigen print immunoassay for the development of serological diagnosis of infectious diseases

Serological diagnosis of infectious diseases that generate a highly heterogeneous antibody repertoire, such as tuberculosis, requires tests based on cocktails of antigens. We describe a new method called multi-antigen print immunoassay (MAPIA) for cocktail-based serological diagnosis. The assay entails the application of antigen to nitrocellulose membranes by micro-aerosolization (printing), followed by antibody detection using standard chromogenic immunodevelopment. Cocktails of protein antigens of Mycobacterium tuberculosis tested by MAPIA were found to maintain the serological activity of each of their components. In contrast, the same cocktails tested by enzyme-linked immunosorbent assay (ELISA) had a serological activity that was lower than the sum of the activities of their components. Consequently, cocktail-based MAPIA attained the diagnostic sensitivity expected on the basis of single antigen results, while a significant loss of diagnostic sensitivity was observed with cocktail-based ELISA. Thus, the MAPIA format is superior to conventional ELISA for the serological diagnosis of infectious diseases characterized by heterogeneous antibody responses.

MTSA-10, the product of the Rv3874 gene of Mycobacterium tuberculosis, elicits tuberculosis-specific, delayed-type hypersensitivity in guinea pigs

In a search for new skin test reagents specific for tuberculosis, we found that the antigen encoded by gene Rv3874 of Mycobacterium tuberculosis elicited delayed-type hypersensitivity in M. tuberculosis-infected guinea pigs but not in control animals immunized with Mycobacterium bovis bacillus Calmette-Guérin (BCG) or Mycobacterium avium. The antigen, which was named MTSA-10 (for M. tuberculosis-specific antigen 10), is a prime candidate for a component of a new tuberculin that will allow discrimination by a skin test of latent M. tuberculosis infection from vaccination with BCG or from sensitization with environmental, nontuberculous mycobacteria.

Humoral immune responses to multiple antigens of Mycobacterium tuberculosis in tuberculosis patients co-infected with the human immunodeficiency virus

A panel of ten protein antigens of Mycobacterium tuberculosis was used to evaluate serum antibody responses to tuberculosis in patients co-infected with the human immunodeficiency virus (HIV) and in HIV-infected control individuals without tuberculosis. Most (70%) of the tuberculosis patients had serum reactivity to at least one antigen and maintained the diverse antibody repertoire previously observed in HIV-negative tuberculosis patients.

Differential T cell responses to Mycobacterium tuberculosis ESAT6 in tuberculosis patients and healthy donors

Vaccination against and diagnosis of tuberculosis are still insufficient. Proteins secreted by Mycobacterium tuberculosis induce strong immune responses in tuberculosis and constitute prime candidates for development of novel vaccines against tuberculosis as well as for immunodiagnostic assays. We investigated the role of the secreted proteins MPT63, MPT64 and ESAT6 from M. tuberculosis in healthy individuals and tuberculosis patients. None of the secreted proteins stimulated peripheral blood mononuclear cells from healthy donors. In contrast, CD4+ T cells from many tuberculosis patients were stimulated in an MHC class II-restricted fashion by ESAT6, but not by MPT63 or MPT64. T cell reactivities of tuberculosis patients were focused on the N-terminal region of ESAT6. The ESAT6 T cell epitopes were presented by different HLA-DR phenotypes. Cell cultures responding to either ESAT6 or synthetic peptides thereof showed mRNA transcripts for macrophage inflammatory protein (MIP)-1alpha, monocyte chemotactic protein (MCP)-1 or IL-8 and production of IFN-gamma and MIP-1alpha. Our results suggest that the secreted M. tuberculosis proteins MPT63, MPT64 or ESAT6 do not stimulate unprimed T cells, and that ESAT6 may be a potential candidate antigen for detection of clinical disease.

Diversity of antigen recognition by serum antibodies in experimental bovine tuberculosis

Tuberculosis in cattle remains a major zoonotic and economic problem in many countries. The standard diagnostic assay for bovine tuberculosis, the intradermal tuberculin test, has low accuracy. Therefore, alternative immunodiagnostic methods, such as serological assays, are needed for detection of infected animals. Development of an accurate serodiagnostic test requires a detailed understanding of the humoral immune responses during bovine tuberculosis and, in particular, identification of the key antigens of Mycobacterium bovis involved in antibody production. In this study, we characterized antibody responses in cattle experimentally infected with M. bovis. Sequential serum samples were collected every 3 to 4 weeks for up to 27 months postinfection. Circulating immunoglobulin G antibody levels were measured by an enzyme-linked immunosorbent assay using 12 highly purified recombinant proteins of M. bovis. Six proteins, ESAT-6, 14-kDa protein, MPT63, MPT70, MPT51, and MPT32, were identified as major seroreactive antigens in bovine tuberculosis. A remarkable animal-to-animal variation of antigen recognition by serum antibodies was observed. Kinetic analyses of the antibody production to individual antigens during infection revealed that the heterogeneous antigen recognition profile changed markedly in a given infected animal as disease progressed.

Three-step purification of lipopolysaccharide-free, polyhistidine-tagged recombinant antigens of Mycobacterium tuberculosis

Previous work has shown that the study of host immune responses against Mycobacterium tuberculosis, the causative agent of tuberculosis, requires the availability of multiple mycobacterial antigens. Since purification of protein from M. tuberculosis cells is extremely cumbersome, we developed a protocol for purifying milligram amounts of ten recombinant antigens of M. tuberculosis from E. coli cells. Purified proteins were immunologically active and free of contaminants that confound interpretation of cell-based immunological assays. The method utilizes a three-step purification protocol consisting of immobilized metal-chelate affinity chromatography, size exclusion chromatography and anion-exchange chromatography. The first two chromatographic steps yielded recombinant protein free of protein contaminants, while the third step (anion-exchange chromatography) efficiently removed E. coli lipopolysaccharide, a potent polyclonal activator of lymphoid cells. The recombinant proteins were immunologically indistinguishable from their native (i.e., purified from M. tuberculosis) counterparts. Thus the method provides a way to utilize recombinant proteins for immunological analyses that require highly purified antigens.

Use of Mycobacterium tuberculosis complex-specific antigen cocktails for a skin test specific for tuberculosis

The tuberculin skin test currently used to diagnose infection with Mycobacterium tuberculosis has poor diagnostic value, especially in geographic areas where the prevalence of tuberculosis is low or where the environmental burden of saprophytic, nontuberculous mycobacteria is high. Inaccuracy of the tuberculin skin test often reflects a low diagnostic specificity due to the presence in tuberculin of antigens shared by many mycobacterial species. Thus, a skin test specific for tuberculosis requires the development of new tuberculins consisting of antigens specific to M. tuberculosis. We have formulated cocktails of two to eight antigens of M. tuberculosis purified from recombinant Escherichia coli. Multiantigen cocktails were evaluated by skin testing guinea pigs sensitized with M. bovis BCG. Reactivity of multiantigen cocktails was greater than that of any single antigen. Cocktail activity increased with the number of antigens in the cocktail even when the same amount of total protein was used for cocktails and for each single antigen. A cocktail of four purified antigens specific for the M. tuberculosis complex elicited skin test responses only in BCG-immunized guinea pigs, not in control animals immunized with M. avium. These findings open the way to designing a multiantigen formulation for a skin test specific for tuberculosis.

Heterogeneous antibody responses in tuberculosis

Antibody responses during tuberculosis were analyzed by an enzyme-linked immunosorbent assay with a panel of 10 protein antigens of Mycobacterium tuberculosis. It was shown that serum immunoglobulin G antibodies were produced against a variety of M. tuberculosis antigens and that the vast majority of sera from tuberculosis patients contained antibodies against one or more M. tuberculosis antigens. The number and the species of serologically reactive antigens varied greatly from individual to individual. In a given serum, the level of specific antibodies also varied with the antigen irrespective of the total number of antigens recognized by that particular serum. These findings indicate that person-to-person heterogeneity of antigen recognition, rather than recognition of particular antigens, is a key attribute of the antibody response in tuberculosis.

MTC28, a novel 28-kilodalton proline-rich secreted antigen specific for the Mycobacterium tuberculosis complex

Proteins that are actively secreted by Mycobacterium tuberculosis serve as major targets of immune responses in the infected host. To identify and purify novel proteins in the filtrates of M. tuberculosis cultures, a bacteriophage lambda library of M. tuberculosis H37Rv DNA was immunoscreened by using an anti-culture filtrate rabbit antiserum. Of 20 positive clones isolated, 6 were analyzed and found to express the genes for two known components of the early culture filtrate, the secreted 45/47-kDa antigen complex and the KatG protein, and two novel genes. Here we report the molecular cloning and nucleotide sequence of one of the new genes encoding a culture filtrate protein of 310 amino acid (aa) residues. We called this gene mtc28. The deduced polypeptide sequence contained an NH2-terminal, highly hydrophobic 32-aa region having properties of a secretion signal peptide. The putative 278-aa mature MTC28 protein was characterized at its NH2 and COOH termini by a high content of proline and alanine residues organized in an (AP)n motif. Thus, MTC28 is a new member of a group of proline-rich antigens found in M. tuberculosis and Mycobacterium leprae. As shown by DNA hybridization experiments, the mtc28 gene was present only in species of the M. tuberculosis complex. Purified recombinant MTC28 antigen evoked strong delayed-type hypersensitivity and antibody responses in guinea pigs immunized with Mycobacterium bovis BCG, but not in guinea pigs immunized with Mycobacterium avium. The strong immunological activity of MTC28 and the absence of B- and T-cell epitopes cross-reactive with a common environmental mycobacterial species, such as M. avium, make this novel antigen an attractive reagent for immunodiagnosis of tuberculosis.

Binding of a novel host factor to the pT181 plasmid replication enhancer

Replication enhancers are cis-acting genetic elements that stimulate the activity of origins of DNA replication. The enhancer found in plasmid pT181 of Staphylococcus aureus, called cmp, functions at a distance of 1 kb from the origin of DNA replication to stimulate the interaction between the replication initiation protein and the origin. DNA encoding cmp-binding activity was isolated by screening an expression library of S. aureus DNA in Escherichia coli, and a novel gene, designated cbf1, was identified. The cbf1 locus codes for a polypeptide of 313 amino acid residues (cmp-binding factor 1 [CBF1]; Mr = 35,778). In its COOH-terminal region, the protein sequence contains the helix-turn-helix motif common to many DNA binding proteins that usually bend DNA. The specificity of CBF1 binding for cmp was demonstrated by affinity chromatography using cmp DNA and by competition binding studies. DNase I footprinting analysis of the CBF1-cmp complexes revealed DNase I-hypersensitive sites in phase with the helical periodicity of DNA, implying that CBF1 increases distortion of the intrinsically bent cmp DNA.

Molecular cloning, purification, and serological characterization of MPT63, a novel antigen secreted by Mycobacterium tuberculosis

Proteins that are actively secreted by Mycobacterium tuberculosis generate immune responses in the infected host. This has prompted the characterization of protein components of mycobacterial culture filtrates to develop subunit vaccines and immunodiagnostic reagents. Fractionation of filtrates of M. tuberculosis cultures has yielded an abundant protein called MPT63, which has an apparent molecular mass of 18 kDa. We report the molecular cloning and nucleotide sequence of the mpt63 gene, purification of recombinant MPT63 antigen from Escherichia coli cells, and serological characterization of MPT63. Nucleotide sequence analysis of mpt63 identified an open reading frame encoding a protein of 159 amino acids (aa) consisting of a 29-aa secretion signal peptide and a 130-aa mature MPT63 protein. Recombinant MPT63 protein, purified from E. coli cells, and native MPT63, purified from M. tuberculosis culture filtrates, were indistinguishable in serological assays. Thus, the recombinant protein constitutes a valuable reagent for immunological studies. MPT63 evoked humoral immune responses in guinea pigs infected with virulent M. tuberculosis by the aerosol route. The mpt63 gene is found only in species of the M. tuberculosis complex, as shown by DNA hybridization experiments. Moreover, polyclonal antibody against MPT63 does not cross-react with proteins of a common environmental mycobacterial species, Mycobacterium avium. The absence of cross-reactive epitopes makes MPT63 an attractive candidate as an M. tuberculosis complex-specific diagnostic reagent. In particular, evaluation of MPT63 as an M. tuberculosis complex-specific reagent for diagnostic skin testing is under way.

Monoclonal antibodies to detect capsular diversity among Bacteroides fragilis isolates

The capsular polysaccharide complex (CPC) of Bacteroides fragilis is composed of two distinct polysaccharides, designated PS A and PS B, and is a major virulence factor of this microorganism. In order to investigate the antigenic diversity of the CPCs of B. fragilis strains, we generated and characterized 10 monoclonal antibodies (MAbs) directed to the CPCs of three reference strains. The specificities of the MAbs were determined by enzyme-linked immunosorbent assay and dot-immunobinding assay. At least one MAb was specific for each PS A and PS B of the three strains. The MAbs were used to detect capsular antigens on the surface of 231 B. fragilis isolates from different geographical areas by a whole-cell dot-immunobinding assay. Over half of the strains, regardless of the country of origin, reacted with at least one MAb. Clinical extraintestinal infection isolates were significantly more reactive than fecal isolates, suggesting an association between capsular composition and the propensity to cause clinical infections. The patterns of reactivity of the isolates with the 10 MAbs were very different and sometimes extremely complex and indicated a sharing of epitopes among different capsular polysaccharides. The reactive strains could be grouped according to 32 different patterns; some patterns were relatively common, while others were rarer and were shown by only one or two strains. These results show that B. fragilis capsular polysaccharides are antigenically extremely diverse. This complexity and the large number of nonreactive strains indicate that a typing system based on B. fragilis capsular antigens will be difficult to establish.

Detection of intestinal and extra-intestinal strains of enterotoxigenic Bacteroides fragilis by the HT-29 cytotoxicity assay

Bacteroides fragilis strains with enterotoxic activity can be isolated from the faeces of newborn farm animals with diarrhoea and are called enterotoxigenic B. fragilis (ETBF). These strains can now be detected in an in-vitro cytotoxicity assay with HT-29 cells. In this study, 146 B. fragilis strains (95 faecal and 40 extra-intestinal isolates) and 64 Bacteroides isolates belonging to species other than B. fragilis were tested for their ability to produce enterotoxin. Sixteen strains of ETBF were identified; all belonged to the fragilis species and represented 11% of all B. fragilis examined. The prevalence was similar among extraintestinal and faecal strains, 11.5% and 10%, respectively. The production of enterotoxin in clinical isolates appeared to be associated with infections where tissue destruction was more prominent. Enterotoxigenicity was not associated with the presence of a plasmid and the plasmid profiles of ETBF strains that harboured plasmids were different. These results show that enterotoxin production by human isolates of B. fragilis is not uncommon and could represent a new virulence factor of B. fragilis.