RSV infection modulates IL-15 production and MICA levels in respiratory epithelial cells.

The cytokine interleukin (IL)-15, major histocompatibility complex (MHC) class I molecules and MHC class I chain-related proteins (MIC) A and B are involved in cellular immune responses to virus infections but their role in respiratory syncytial virus (RSV) infection has not been studied. We aimed to determine how RSV infection modulates IL-15 production, MHC class I and MICA expression in respiratory epithelial cells, the molecular pathways implicated in virus-induced IL-15 production and how interferon (IFN)-γ alters RSV-induced IL-15 production and MHC class I and MICA expression. We infected respiratory epithelial cell lines (A549 and BEAS-2B cells) and primary bronchial epithelial cells with RSV and measured production of IL-15, expression of MHC I and MICA and the role of the transcription factor nuclear factor (NF)-κB. We report here that RSV increases IL-15 in respiratory epithelial cells via virus replication and NF-κB-dependent mechanisms. Furthermore, RSV infection of epithelial cells upregulated cell surface expression of MICA and levels of soluble MICA. IFN-γ upregulated RSV induction of soluble IL-15 but inhibited induction of MICA. Upregulation of IL-15, MHC I and MICA are likely to be important mechanisms in activating immune responses to RSV by epithelial cells.

Evidence for extrathymic changes in the T cell receptor gamma/delta repertoire.

The germline repertoire of variable genes for the TCR-gamma/delta is limited. This, together with the availability of several V delta-specific and a C delta-specific mAbs, has made it possible to assess differences in the TCR-gamma/delta repertoire in man. TCR-gamma/delta cells expressing particular V gene segments have been previously shown to be localized in different anatomical sites. In this study, analysis of TCR-gamma/delta V gene segment usage performed on subjects from the time of birth through adulthood revealed striking age-related changes in the TCR-gamma/delta repertoire in peripheral blood. V delta 1+ gamma/delta T cells predominated in thymus as well as in peripheral blood at birth and then persisted as a relatively constant proportion of CD3+ PBL. However, V delta 2+ gamma/delta T cells that constitute a small proportion of the CD3+ cells in thymus and in peripheral blood at birth, then expand and account for the major population of gamma/delta T cells in PBL in adults. No parallel postnatal expansion of V delta 2+ cells in the thymus was observed, even when paired thymus-peripheral blood specimens were obtained on subjects between the ages of 3 d and 8 yr. The subset of V delta 2+ lymphocytes that was expanded in peripheral blood expressed high levels of CD45RO suggesting prior activation of these cells, consistent with the possibility that their expansion might have resulted from exposure to foreign antigens or superantigens. In contrast, V delta 1+ T cells in PBL showed no comparable increase in relative numbers and were either negative or expressed only low levels of CD45RO. Consistent with evidence for extrathymic peripheral expansion of selective TCR-gamma/delta subsets, no link between MHC haplotype and differences in the TCR-gamma/delta V gene usage between individuals was apparent, and identical twins displayed TCR-gamma/delta variable gene segment phenotypes that were strikingly different from one another. The elements that determine the TCR-gamma/delta repertoire in individuals are not known. It is possible that both thymic selection and extrathymic factors may influence the peripheral repertoire. Recently, TCR-gamma/delta+ lymphocytes have been shown to expand markedly in peripheral lymphoid tissues and infectious lesions in response to mycobacterial antigens, and a correlation between mycobacterial responses and TCR-gamma/delta V gene usage has been shown in mice. The data presented here demonstrated peripheral age-related changes in the gamma/delta repertoire and point to the importance of extrathymic expansion of specific gamma/delta subsets in generating the human TCR-gamma/delta repertoire.

Human lymphocytes bearing T cell receptor gamma/delta are phenotypically diverse and evenly distributed throughout the lymphoid system.

A direct quantitative and phenotypic cytofluorographic analysis of TCR-gamma/delta+ lymphocytes as well as an immunohistologic study of their tissue distribution and microanatomy was made possible by the availability of two mAbs (anti-TCR-delta 1 and anti-C gamma M1) specific for framework determinants on human TCR gamma and delta chains, respectively. TCR-gamma/delta+ lymphocytes, ranging between greater than 0.5 and 16% of CD3+ cells, were found in fetal and postnatal thymus, fetal and adult peripheral lymphoid organs, and adult peripheral blood. While TCR-gamma/delta+ lymphocytes comprised a small subpopulation of T cells (mean, approximately 4%) occasionally greater than 10-16% of CD3+ cells expressed TCR-gamma/delta. Virtually all TCR-gamma/delta+ thymocytes/lymphocytes expressed CD7, CD2, and CD5 but were heterogeneous with respect to their expression of CD1, CD4, CD8, CD28, CD11b, CD16, and Leu-7. Human TCR-gamma/delta+ cells populate both organized lymphoid tissues (thymus, tonsil, lymphnode, and spleen) as well as the gut- and skin-associated lymphoid systems at similar frequencies without obvious tropism for epithelial microenvironments. TCR-gamma/delta+ lymphocytes tend to be located within a given organ wherever TCR-alpha/beta+ lymphocytes are found. This study shows that TCR-gamma/delta+ lymphocytes constitute a small but numerically important, phenotypically diverse T cell population distributed throughout the body. These results support the concept that TCR-gamma/delta+ cells comprise a distinct, functionally heterogeneous, mature T cell sublineage that may substantially broaden the T cell repertoire at all immunologically relevant sites.

Recognition of stress-induced MHC molecules by intestinal epithelial gammadelta T cells.

T cells with variable region Vdelta1 gammadelta T cell receptors (TCRs) are distributed throughout the human intestinal epithelium and may function as sentinels that respond to self antigens. The expression of a major histocompatibility complex (MHC) class I-related molecule, MICA, matches this localization. MICA and the closely related MICB were recognized by intestinal epithelial T cells expressing diverse Vdelta1 gammadelta TCRs. These interactions involved the alpha1alpha2 domains of MICA and MICB but were independent of antigen processing. With intestinal epithelial cell lines, the expression and recognition of MICA and MICB could be stress-induced. Thus, these molecules may broadly regulate protective responses by the Vdelta1 gammadelta T cells in the epithelium of the intestinal tract.

Activation of NK cells and T cells by NKG2D, a receptor for stress-inducible MICA.

Stress-inducible MICA, a distant homolog of major histocompatibility complex (MHC) class I, functions as an antigen for gammadelta T cells and is frequently expressed in epithelial tumors. A receptor for MICA was detected on most gammadelta T cells, CD8+ alphabeta T cells, and natural killer (NK) cells and was identified as NKG2D. Effector cells from all these subsets could be stimulated by ligation of NKG2D. Engagement of NKG2D activated cytolytic responses of gammadelta T cells and NK cells against transfectants and epithelial tumor cells expressing MICA. These results define an activating immunoreceptor-MHC ligand interaction that may promote antitumor NK and T cell responses.

Immunobiology of human NKG2D and its ligands.

The NKG2D-DAP10 receptor complex activates natural killer (NK) cells and costimulates effector T cell subsets upon engagement of ligands that can be conditionally expressed under physiologically harmful conditions such as microbial infections and malignancies. These characteristics have given rise to the widely embraced concept of immunorecognition of "induced or damaged self," complementing the "missing self" paradigm that is represented by MHC class I allotypes and their interactions with inhibitory receptors on NK cells. However, this notion may only be partially sustainable, as various patterns of constitutive tissue distributions have become apparent among members of one NKG2D ligand family. This review summarizes the biological properties of NKG2D and its ligands and discusses the interactions and regulation of these molecules with emphasis of their significance in microbial infections, tumor immunology, and autoimmune disease.

Differential expression of class II alloantigens by keratinocytes in disease.

The purpose of this study was to determine whether keratinocytes in certain disease states such as cutaneous T-cell lymphoma and lichen planus, express HLA-DR antigens (corresponding to the murine I-E antigens) only or whether they are also capable of expressing HLA-DQ antigens (analogues of the murine I-A antigens). Cryostat sections from 11 biopsies from cutaneous T-cell lymphoma and from 11 lichen planus biopsy specimens were submitted to indirect immunofluorescence and a 4-step immunoperoxidase method. This consists of applying monoclonal antibodies recognizing HLA-DR and HLA-DQ molecules and the intracytoplasmic invariant chain of the class II molecules. In 8 of the 11 cutaneous T-cell lymphoma specimens and in 3 of the 11 lichen planus biopsies concomitant expression of HLA-DR and HLA-DQ molecules by keratinocytes was detectable with the immunoperoxidase method. However, with the indirect immunofluorescence technique HLA-DQ antigens on keratinocytes could not be detected. The simultaneous expression of surface-bound HLA-DR antigens and intracytoplasmic gamma-chains was demonstrable in all cases investigated and with both the immunohistologic methods applied.

Leu-3/T4 expression on epidermal Langerhans cells in normal and diseased skin.

Recent evidence exists that the expression of the Leu-3/T4 antigen is not restricted to thymus-derived lymphocytes but can also be detected on mononuclear phagocytes and epidermal Langerhans cells (LC). When searching for the presence of Leu-3/T4 antigen-bearing cells in tissue sections of a variety of inflammatory and neoplastic skin disorders, we observed quantitative and qualitative differences in the intensity of anti-Leu-3a labeling of epidermal dendritic cells. Reasoning that Leu-3/T4 expression by these cells might be a dynamic event, we compared the anti-Leu-3a LC staining pattern in clinically normal-appearing skin (CNAS) with the expression of this antigen on epidermal dendritic cells in a variety of skin disorders. For this purpose, 4-microns cryostat sections were exposed to the monoclonal anti-Leu-3a reagent and antibody binding was visualized by a sensitive 4-step immunoperoxidase technique. Within CNAS, Leu-3a+ dendritic epidermal cells were visualized at the threshold of detectability. Immunoelectron microscopic studies confirmed the LC nature of these cells. In sharp contrast to CNAS, strong and prominent anti-Leu-3a LC labeling was almost invariably encountered in biopsy specimens from patients with cutaneous T-cell lymphoma and various inflammatory conditions but not in proliferative disorders of resident skin cells. Whereas in CNAS the density of T6+ epidermal dendritic cells greatly exceeded that of anti-Leu-3a-reactive dendritic cells, these differences were less pronounced in diseased skin. Our results: confirm earlier observations that epidermal LC may bear Leu-3/T4 antigens; and in addition, suggest that the degree of Leu-3/T4 expression is regulated by signals from inflammatory cells. The induction of class II alloantigen receptors on class II alloantigen-bearing LC may represent an important regulation mechanism of antigen-presenting cell function.

The phenotypic spectrum of histiocytosis X cells.

Proliferating cells in histiocytosis X (histiocytosis X cells) share many structural and immunophenotypic features with Langerhans cells, leading to the assumption that histiocytosis X represents a proliferative disorder of Langerhans cells. Because, depending on their state of activation and/or differentiation, Langerhans cells exhibit a varying immunophenotype, we investigated whether histiocytosis X cells display a similar phenotypic heterogeneity and, if so, whether the heterogenous biological behavior of histiocytosis X is reflected by differences in the immunophenotype of the proliferating cells. In 21 patients suffering from different clinical manifestations of histiocytosis X, proliferating cells uniformly expressed class I and II alloantigens, T200, CD1, CD4, and S100 protein. In 12 of 21 cases, histiocytosis X cells additionally exhibited immunocytochemically detectable amounts of C3b and C3bi receptors and certain monocyte/macrophage antigens (CDw14, Ki-M1, Ki-M6). This immunophenotypic heterogeneity of histiocytosis X cells could not be correlated with clinical course, prognosis, and final outcome of the disease in a given patient. The capacity of histiocytosis X cells to immunophenotypically mimic various states of Langerhans cell activation and/or differentiation, however, underscores the concept of histiocytosis X as a proliferative disorder of Langerhans cell origin.

Epidermal Langerhans cells--a target for HTLV-III/LAV infection.

Langerhans cells (LC) are bone marrow-derived, Ia+, CD1+, CD4+, ATPase+ dendritic antigen-presenting cells within the human epidermis. Since the CD4 molecule has been implicated as a receptor structure for HTLV-III/LAV (human T-cell leukemia virus/lymphadenopathy-associated virus), we asked whether LC from HTLV-III/LAV-seropositive individuals display signs of HTLV-III/LAV infection. In skin biopsies from 7/40 HTLV-III/LAV-infected persons (1 asymptomatic carrier, 2 patients with acquired immunodeficiency syndrome (AIDS)-related complex and 4 patients with AIDS), LC were the only epidermal cells to react with a monoclonal antibody specific for the HTLV-III core protein p17. A varying percentage of p17+ LC were morphologically altered with blunt dendrites and poorly demarcated cellular contours. In one of these biopsies, the presence of LC-associated viral particles characteristic of HTLV-III/LAV as well as cytopathic changes in approximately one-third of the LC population were demonstrated by electron microscopy. These results strongly suggest that LC may harbor HTLV-III/LAV. The infection of LC with this retrovirus may have deleterious consequences for the immunologic functions of this cell system and may thus contribute to both the acquisition of immunodeficiency and the infectious and neoplastic complications of AIDS.

Autoimmunity in Lyme disease: molecular cloning of antigens recognized by antibodies in the cerebrospinal fluid.

In inflammatory disease of the central nervous system (CNS), oligoclonal bands of immunoglobulin with restricted heterogeneity can often be observed in cerebrospinal fluid (CSF) samples. These antibodies can be directed against the disease inducing pathogen or might be autoreactive and involved in the process of brain inflammation and demyelination. We used a molecular biology approach to characterize these antibody responses in patients with Lyme disease. This disorder is caused by infections with the spirochete Borrelia burgdorferi which is transmitted by ticks. Lyme disease can be associated with neurological symptoms due to inflammation of the central and peripheral nervous system. Phage lambda gtll expression libraries from B. burgdorferi and human brain were screened with cerebrospinal fluid antibody probes from patients with Lyme disease. We obtained recombinant phage clones encoding antigenic proteins from both B. burgdorferi and human CNS libraries. Thus, in this study two patients with chronic Lyme disease produced antibodies against recombinant B. burgdorferi as well as against CNS proteins, and the generation of this transient autoimmune response might be essential to the development of demyelinating disease.

Persistent intrathecal secretion of oligoclonal, Borrelia burgdorferi-specific IgG in chronic meningoradiculomyelitis.

In the cerebrospinal fluid IgG of five patients with lymphomeningoradiculitis (Bannwarth's syndrome) and radiculomyelitis studied by immunoblot technique an oligoclonal pattern was found. Most of these oligoclonal bands were specific for Borrelia burgdorferi. In patients suffering from chronic meningoradiculomyelitis, repeated CSF examination by this technique showed persistent secretion of identical IgG bands. Thus, the specific humoral immune response and the disease activity could be documented over the course of the disease.

Anti-tuberculosis drug resistance surveillance in Uganda 1996-1997.

SETTING: Drug resistance surveillance conducted by the National Tuberculosis and Leprosy Control Programme (NTLP) Uganda from 1996-1997 in collaboration with the Armauer Hansen Institute/German Leprosy Relief Association (GLRA), Germany, for the WHO/IUATLD Global Project on Anti-Tuberculosis Drug Resistance Surveillance. OBJECTIVE: To determine the prevalence of primary and acquired anti-tuberculosis drug resistance in Uganda. DESIGN: The survey area covered three GLRA-supported operational NTLP zones, corresponding to 50% of the Ugandan population. A representative random sampling of individual patients was chosen as sampling procedure. Altogether 586 smear-positive TB patients (537 new cases and 49 previously treated cases) were included in the survey. RESULTS: For primary resistance the results were as follows: isoniazid (H) 6.7%, rifampicin (R) 0.8%, ethambutol (E) 6.1%, streptomycin (S) 13.4%, thioacetazone (T) 3.2%, pyrazinamide (Z) 0%, multidrug resistance (MDR) 0.5%; for acquired resistance they were: H 37.8%, R 4.4%, S 22.2%, E 11.1%, T 20.0%, Z 0%, and MDR 4.4%. CONCLUSION: According to these data the NTLP Uganda has been effective in preventing high levels of primary drug resistance. If it is assumed that the sampling process reflects the distribution of new patients and previously treated patients in the study areas, the amount of acquired resistance (any resistance) in the community of smear-positive patients is approximately 5%. To further monitor programme performance the NTLP will embark on a nationwide survey in 1998/1999.

Universal pattern of RpoB gene mutations among multidrug-resistant isolates of Mycobacterium tuberculosis complex from Africa.

SETTING: Multidrug-resistant tuberculosis (MDR-TB) presents an increasing burden in Southern Africa. Rapid diagnostic tests for drug resistance to rifampicin have been developed based on mutation analysis of the rpoB gene. However, geographic differences of underlying mutations have recently been suggested. OBJECTIVE: Drug-resistant strains of Mycobacterium tuberculosis complex from Africa were analysed for geographic differences in frequency and location of rpoB mutations. DESIGN: A random sample of rifampicin-resistant strains was collected from 87 patients with pulmonary MDR-TB treated in 12 hospitals from six different regions of South Africa. In addition, 18 isolates of M. tuberculosis complex from Namibia, Sierra Leone, and Uganda, including 13 isolates of M. africanum, were analyzed. Point mutations were detected by direct sequence analysis of the rpoB gene. RESULTS: Missense mutations were identified for 91 isolates (87%). Double mutations were present in eight (8%) MDR-TB isolates, two of which carried one mutation outside a previously described diagnostic region. We found no geographic differences regarding the frequency and pattern of single rpoB gene mutations. CONCLUSION: Our results confirm that molecular genetic analysis of rifampicin resistance based on a core region within the rpoB gene is universally applicable to strains of M. tuberculosis complex from different geographic regions.

Afferent projections of the rat major occipital nerve studied by transganglionic transport of HRP.

The central projection fields of cutaneous neurons of the rat's major occipital nerve have been investigated using the method of transganglionic transport of horseradish peroxidase (HRP), with tetramethylbenzidine according to Mesulam (1978) as the chromogen. Furthermore, the course of the nerve, diameter distribution of myelinated axons, and diameter distribution of HRP-labeled perikarya of spinal ganglion cells belonging to this nerve, diameter distribution of myelinated axons, and diameter distribution of HRP-labeled perikarya of spinal ganglion cells belonging to this nerve have been studied. Following HRP application to the proximal stump of the cut nerve, labeled structures were found ipsilaterally in the cervical spinal cord and in the medulla oblongata. In the spinal cord, reaction product was mainly concentrated in the lateral parts of laminae I-III of the dorsal horn in segments C2 and C3. In C1, primary afferent terminals were more sparsely distributed and restricted to laminae I and II. Reaction product was also seen in the tract of Lissauer in segments C1-C4. In the medulla oblongata HRP labeled structures were observed in the medial cuneate nucleus, in the rostral part of the external cuneate nucleus, and in the nucleus of the spinal tract of the trigeminal nerve. A possible somatotopic arrangement of central terminals of cutaneous neurons within the cervical dorsal horn, as well as differences between the projection fields of muscle and skin afferents within the upper cervical cord and caudal medulla are discussed.

Histochemical tracing of lysosomal enzymes. Improved preparation technique for acid phosphatase, beta-glucuronidase, acid-beta-galactosidase, and arylesterase in rat liver.

The efficiency of the membrane methods of Meijer (1972) and Lojda (1973) in histochemical lysosome tracing was studied and compared with the results of a preparation technique developed by us, employing fresh-frozen celloidin-coated sections; in addition, these methods were compared with results obtained with conventional formalin-sucrose-fixed livers. The lysosomes were traced by reactions for ACPase, beta-glucuronidase, arylesterase and acid-beta-galactosidase activity in rat livers systematically harvested at different time points of occurence of their maximal and minimal activities during the 24-h period, thus indicating a heterogeneity of lysosomes. 3. Optimal results with respect to the morphological appearance of lysosomes were obtained in fresh-frozen celloidin coated sections. This preparation method also caused no enzyme inhibition or loss, thus delivering comparatively the strongest reactions in livers and in enzyme models. 4. Day-time-dependent extralysosomal enzyme activities regularly occur in hepatocytes. Extralysosomal localizations however, are not a consequence of technically induced enzyme diffusion; they are best visualized in celloidin-coated sections; the membrane method produces less satisfactory results, and formalin-sucrose-fixed livers were least satisfactory.

Adenovirus type 19 keratoconjunctivitis in Canada.

We describe an outbreak of epidemic keratoconjunctivitis occurring in Montreal during the winter of 1974. Adenovirus type 19 was the only virus isolated. We confirm the presence of type 19 adenovirus in Canada; it produces severe keratoconjunctivitis. The incubation period, method of spread and clinical findings resemble those seen in outbreaks of type 8 EKC. The prevalence of adenovirus type 19 in the population of Canada is unknown. Although some object to the use of the term EKC for infection caused by adenoviruses other than type 8, we believe that EKC should be regarded as an entity requiring virus isolation and antibody determination to identify the adenovirus type responsible for it.

[Initial clinical experiences in a large Austrian patient sample with immunodeficiency syndrome (AIDS): I. Type and course of encountered infections]. / Erste klinische Erfahrungen bei einem grösseren österreichischen Patientenkollektiv mit erworbenem Immunmangelsyndrom (AIDS): I. Art und Verlauf der aufgetretenen Infektionen.

This study presents a report on the first clinical experiences gained in 68 hospitalized HIV antibody-positive patients from Austria, covering a period of twelve months. 36 patients (52.9%) belonged to risk group I or Ib (homo- or bisexual), whereas 26 (38.2%) patients were i.v. drug abusers (risk group II). 5 (7.4%) patients fulfilled the criteria of stage II of the CDC classification of HIV-associated clinical symptoms, 10 (14.7%) were classified as stage III and the remaining 53 patients (78%) as stage IV. The most frequent and also the most serious problem was the development of opportunistic infections. Multiple infections were found in 45.7% of all cases. Kaposi's sarcoma was found in 9 patients who all belonged to risk group I. During the entire observation period 10 patients died as a consequence of HIV-1-induced immunodeficiency and the resulting opportunistic infections and/or neoplasms.

Campylobacter in healthy slaughter pigs: a possible source of infection for man.

Campylobacter were isolated from 103 of 173 (59 per cent) specimens of healthy slaughter pig faeces, washed intestines and water samples collected from a slaughterhouse and butcher's shop in West Germany. As most cases of human campylobacter enteritis are caused by Campylobacter jejuni, an attempt was made to find this organism among the isolates. Twenty-five out of the 103 strains (24 per cent) were identified as C jejuni. C jejuni was also isolated from salted water samples after overnight bowel storage in the butcher's shop, indicating that the customary salt preparation of the intestines did not eliminate all organisms present.

Tuberculosis chemotherapy and sputum conversion among HIV-seropositive and HIV-seronegative patients in south-eastern Uganda.

OBJECTIVE: To investigate if there is a difference in response to tuberculosis treatment between HIV seronegative and HIV seropositive patients following two months of intensive phase tuberculosis treatment. DESIGN: Prospective cohort study. SETTING: St. Francis Leprosy Centre, south-east Uganda. SUBJECTS: Four hundred fifty seven patients with never previously treated sputum smear-positive tuberculosis admitted during a two-year period in 1991/1993. INTERVENTION: Intensive phase treatment with streptomycin, isoniazid, rifampicin and pyrazinamide. MAIN OUTCOME MEASURES: Sputum conversion from a positive to a negative smear at eight weeks of treatment. RESULTS: HIV seropositivity prevalence was 28%. Among HIV seronegative patients, conversion to a negative smear status occurred in 76% persons compared to 78% in HIV seropositive patients. This difference was not statistically significant (OR = 0.9; 95% CI, 0.6-1.5). HIV seropositive patients, however, were more likely to die (p = 0.017). A high prevalence of resistance to isoniazid and streptomycin was found. Isoniazid resistance was more likely in HIV seronegative patients with M. tuberculosis strains compared to HIV seropositive persons (p < 0.005). Initial resistance to antituberculosis drugs did not have a significant effect on smear conversion. CONCLUSION: This study demonstrates that HIV-seropositive status is not a principal factor in delaying sputum conversion among patients receiving intensive phase tuberculosis treatment.

PIP: A prospective cohort study was undertaken to investigate the response of HIV-seropositive and -seronegative patients at St. Francis Leprosy Center, southeastern Uganda, to tuberculosis chemotherapy. The study population included 457 patients without a history of prior tuberculosis therapy between 1991 and 1993. The subjects were exposed to an intensive phase therapy of rifampicin, streptomycin, isoniazid, and pyrazinamide. After the treatment, sputum culture and sensitivity tests were conducted. Findings showed that 77% of the patients who never received tuberculosis treatment in the past converted to a negative smear status after the 8-week treatment. There was no significant difference in sputum conversion rates between HIV-seropositive and -seronegative patients. The study also revealed that HIV seropositivity prevalence was 28%. Among HIV-seronegative patients, conversion to a negative smear status occurred in 76% compared to 78% HIV-seropositive patients. Moreover, a significant number of HIV-seronegative patients died during the initial course of the therapy. Also, a high prevalence of isoniazid and streptomycin resistance was noted; however, this result never affected the conversions of smears. In conclusion, the study clearly demonstrates that other factors outside the seropositive status may be the principal causes of the delay in sputum conversion among patients receiving intensive tuberculosis chemotherapy.