Characterization of lymphoma-derived cell lines: comparison of cell lines positive and negative for Epstein-Barr virus nuclear antigen. I. Physical, cytogenetic, and growth characteristics.

Sixteen lymphoid cell lines were derived from patients with undifferentiated lymphoma of Burkitt's or non-Burkitt's type. They were obtained directly from tumor biopsies, from serous effusions, or from bone marrow. In 10 of the cell lines, the Epstein-Barr virus (EBV) nuclear antigen (EBNA) was undetectable; the remaining 6 lines were EBNA-positive (EB-pos). Of the 16 lines, 15 were aneuploid, with detectable chromosome "14q+ markers (11 had +8;14 translocations). These 15 lines, which included the EBNA-negative (EB-neg) lines, were believed to be of tumor cell origin. The remaining line consisted predominantly of diploid cells derived from normal lymphocytes, but some cells of tumor origin were present. Four EB-pos cell lines derived from EB-neg tumors had an aneuploid karyotype consistent with an origin from tumor cells (including no.8;14 translocation in two), which suggested that either tumor cells were infected with EBV in vitro or a tiny fraction of EB-pos tumor cells (or potential tumor cells) present in vivo gave rise to the predominant cell of the line. EB-neg B-cell lines and EB-pos cell lines established from undifferentiated lymphomas differed greatly. EB-neg lines had consistently smaller electronic mean cell volumes and narrow-angle light scatter than did EB-pos lines. This finding correlated with a lower nuclear:cytoplasmic ratio in EB-pos lines. EB-neg lines also had higher saturation cell densities than did EB-pos lines under standard culture conditions. The data indicate either that EBV influences the morphologic and physiologic characteristics of lymphoid cell lines or that EB-neg B-cell lines and EB-pos cell lines are derived ultimately from different lymphocyte subpopulations or that both may apply.

Characterization of the Epstein-Barr virus isolated from a cell line derived from a patient with American Burkitt's lymphoma.

Epstein-Barr viral (EBV) DNA is nearly always detectable in African Burkitt's lymphoma (BL) but is infrequently found in the histologically indistinguishable American BL. We have derived a tumor cell line from a patient with American BL which produces EBV, and we have compared this virus isolate [JLP(c)] with African BL EBV. The American JLP(c) virus immortalizes human umbilical cord lymphocytes in vitro, and its DNA is indistinguishable from African BL EBV DNA by nucleic acid hybridization and preliminary restriction endonuclease cleavage analysis.

Examination of Epstein-Barr virus and C-type proviral sequences in American and African lymphomas and derivative cell lines.

While Epstein-Barr viral (EBV) DNA is nearly always detectable in African Burkitt's lymphoma (BL), the relatively low frequency of BL in EBV-positive African children and the infrequent finding of EBV in American BL suggest that other cofactors may contribute to the malignant transformation. Among these possible cofactors are type C oncornaviruses. To evaluate this possibility, we screened the cellular DNA from 16 lymphomas (2 African, 14 American) and the DNA from 20 lymphoma-derived cell lines (4 African, 16 American) with a radiolabeled viral DNA probe from EBV and two oncornaviral probes (murine amphotropic 1504A virus and simian sarcoma virus). The radiolabeled EBV DNA probe hybridized with 18 of 36 tumor or cell line DNA's. Only 2 of 11 American BL tumors contained detectable EBV sequences. However, the cell lines derived from three EBV-negative tumors converted in vitro to EBV positivity, suggesting that some of the tumor cells could be infected with EBV. In contrast, none of the tumors or the cell lines derived therefrom hybridized with either the 1504A or the simian sarcoma virus probes, decreasing the likelihood that type C viruses are cofactors with EBV.

Controlled clinical trials of nutritional intervention as an adjunct to chemotherapy, with a comment on nutrition and drug resistance.

Nutritional intervention in the cancer patient [e.g., total parenteral nutrition (TPN)] might improve durable survival because of increased tolerance to aggressive tumor therapy. To determine whether this assumption is correct, 42 patients with diffuse histiocytic lymphoma were induced with prednisone, high-dose methotrexate, Adriamycin, cyclophosphamide, and VP-16 (ProMACE). Nitrogen mustard-vincristine-procarbazine-prednisone (MOPP) consolidation was then used, followed by late intensification with ProMACE. Patients were selected randomly to receive adjuvant TPN or a standard diet during ProMACE-MOPP treatment. While TPN patients had a greater median weight gain than did control patients, lean body mass and degree of myelosuppression did not improved as a consequence of TPN. There was no significant difference in tumor response or survival between TPN and control patients, whether or not the patients were initially malnourished. In a second trial, 32 young patients with metastatic or other poor-prognosis sarcomas were randomly allocated to receive TP or a standard diet as an adjunct to one very intensive course of combination chemotherapy or chemotherapy plus total body irradiation; autologous marrow transplantation was used with gain than did controls but remained in a negative nitrogen balance. Response rates and median durable survival did not differ between the two groups. In both trials, the maximum nutritional support permitted by currently available technology was offered. Thus, the limiting factor may not be nutritional status but rather the intrinsic biology of the tumors and the limitations of their response to current therapy. In in vitro studies of the possible influence of nutrition on cancer treatment, we have compared sublines of P388 murine leukemia cells which are sensitive or resistant to Adriamycin. The difference in drug sensitivity correlated with differences in lipid composition, with more intracellular lipid, and with greater membrane rigidity in the resistant cells. Resistant cells have a relatively poor transport of drug into the cell; moreover, intracellular Adriamycin is sequestered in lipid depots away from DNA. These results suggest one possible relationship between nutritional phenomena and drug sensitivity.

Randomized trial of recombinant human granulocyte-macrophage colony-stimulating factor in pediatric patients receiving intensive myelosuppressive chemotherapy.

PURPOSE: To evaluate whether recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF) reduces the hematologic toxicities and supportive care requirements of an intensive combination chemoradiotherapy regimen in pediatric and young adult sarcoma patients. PATIENTS AND METHODS: Thirty-seven newly diagnosed patients age 1 to 25 years were randomized to receive 18 cycles of chemotherapy alone or with GM-CSF beginning in cycle 3. GM-CSF (5 to 15 micrograms/kg/d subcutaneously) was begun 24 hours after the completion of chemotherapy and continued through day 19 of each cycle or until the absolute granulocyte count (AGC) was > or = 500/microliter on 2 consecutive days. RESULTS: GM-CSF reduced the median duration of grade 4 granulocytopenia from 9.0 days (range, 2 to 24) to 7.0 days (range, 1 to 21) (P < .0001), but did not significantly affect the grade of granulocyte nadir. No differences were seen in the incidence or types of infectious complications, incidence or duration of hospitalization and antimicrobial therapy, response to chemotherapy, or event-free or overall survival. GM-CSF was associated with more severe and protracted thrombocytopenia (median platelet nadir, 29,500/microliter [range, 3,000 to 288,000] v 59,000/microliter [range, 3,000 to 309,000], P < .0001; median time to recovery > 75,000/microliter, 16.0 days [range, 0 to 61] v 14.0 days [range, 0 to 38], P < .0001). CONCLUSION: GM-CSF does not produce clinically meaningful reductions in the degree or duration of severe granulocytopenia following intensive multiagent chemotherapy, but is associated with worsened thrombocytopenia. GM-CSF also does not reduce the need for hospitalization or the incidence of febrile neutropenia and infectious complications. We conclude that the costs and increased toxicities associated with the use of this agent are not justified by its minimal clinical benefit for regimens of this level of intensity.

A prospective randomized trial comparing the infectious and noninfectious complications of an externalized catheter versus a subcutaneously implanted device in cancer patients.

PURPOSE: To compare the frequency of infectious episodes or other problems occurring with an externalized catheter (Hickman) versus a subcutaneously implanted device (Port-a-Cath, Pharmacia, Piscataway, NJ) in cancer patients, we performed a prospective, randomized study in 100 cancer patients (age range, 5 to 74 years). PATIENTS AND METHODS: Patients who were chemotherapy candidates and required an indwelling catheter were monitored prospectively and evaluated during the 180 days after the insertion of the catheter and again at time of study closure. The frequency of catheter use, reason for access, and any problems that might have been related to catheter use were noted. All data were collected prospectively and included the patient's age, sex, underlying malignancy, temperature, and leukocyte and absolute granulocyte counts at the time of catheter insertion and when complications occurred. The time to and reason for removal of the catheter, as well as any intercurrent infectious or mechanical problems, were also determined. RESULTS: Most of the infections that occurred were caused by gram-positive organisms, especially staphylococci or streptococci. A total of 22 complications (11 in each group) resulted in removal of the central line. Only one infection in the Hickman catheter group and four in the Port-a-Cath group led to removal of the central line. All other infectious episodes were successfully treated without removal of the catheters. The mean device life was 230 days for the Hickman catheter and 318 days for the Port-a-Cath (not significant). CONCLUSION: There were no differences between the two study groups regarding incidence of documented infections or mechanical or thrombotic complications.

A prospective randomized trial evaluating prophylactic antibiotics to prevent triple-lumen catheter-related sepsis in patients treated with immunotherapy.

During a 15-month period, 92 patients undergoing 129 treatment episodes of immunotherapy with interleukin-2 (IL-2) alone or with immune cells underwent insertion of central venous catheters (CVCs) in the Surgery Branch, National Cancer Institute. Before each catheter insertion patients were prospectively randomized into one of three treatment groups; therapy with intravenous (IV) placebo using D5W, IV oxacillin, or change of the catheter to a new site every 72 hours. The mean duration of catheterization was 3.8 +/- 1.1 days. No patient in the oxacillin arm developed catheter-related sepsis, while eight patients in the control arms (five, line change, three, placebo) developed catheter-related sepsis (P2 = .050). Seven episodes of catheter-related sepsis were due to Staphylococcus aureus and one was due to Staphylococcus epidermidis. Catheter colonization was reduced significantly in the oxacillin arm versus control arms (P = .0001). Staphylococcus aureus, Staphylococcus epidermidis, and other coagulase-negative Staphylococci were sensitive to oxacillin in 89%, 60%, and 50% of cultures, respectively. No evidence of bacterial overgrowth, candida colonization, or candidemia was observed in these patients. Thus this trial demonstrates that treatment with prophylactic oxacillin can decrease the incidence of catheter-related sepsis in patients undergoing immunotherapy with interleukin-2 (IL-2). To our knowledge this is the first prospective randomized trial to evaluate the prophylactic use of systemic antibiotics in the prophylaxis of CVC sepsis.

Effects of granulocyte colony-stimulating factor and interferon-gamma on antifungal activity of human polymorphonuclear neutrophils against pseudohyphae of different medically important Candida species.

Polymorphonuclear neutrophils (PMNs) are the major host defense against pseudohyphae, the invasive form of Candida species. We studied the effects of granulocyte colony-stimulating factor (G-CSF) and interferon-gamma (IFN-gamma) on the PMN-induced damage of pseudo-hyphae of Candida albicans, Candida tropicalis, and Candida parapsilosis in vitro by using two antifungal assays: a modified limiting dilution assay and a colorimetric metabolic 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. PMNs from healthy volunteers were incubated with either G-CSF (100-10,000 U/ml) or IFN-gamma (10-5000 U/ml) or buffer at 37 degrees C for 90 min and their capacity to damage nonopsonized pseudohyphae was then measured. C. tropicalis appeared to be the most susceptible species, whereas C. parapsilosis showed the highest rate of resistance to PMN damage. G-CSF (500-10,000 U/ml) and IFN-gamma (100-1000 U/ml) enhanced the antifungal activity of PMNs against C. albicans pseudo-hyphae (P < .01 and P < .05). Among the others, G-CSF enhanced PMN-induced damage of C. parapsilosis at concentrations 500-10,000 U/ml (P < .05), whereas it enhanced damage of C. tropicalis only at 10,000 U/ml (P < .01). IFN-gamma (100-1000 U/ml)-primed PMNs also caused augmented damage of C. parapsilosis (P < .05) but not of C. tropicalis at the same concentrations. Species-dependent differences exist in the responses of PMNs to Candida pseudohyphae and G-CSF as well as IFN-gamma are important immunomodulators of phagocytic host defenses against them.

Successful surgical management of neutropenic enterocolitis in two patients with severe aplastic anemia. Case reports and review of the literature.

We describe two patients with severe aplastic anemia in whom neutropenic enterocolitis developed while they were undergoing treatment at the National Institutes of Health. Both patients had progressive symptoms while receiving optimal medical management and both underwent and survived surgical intervention despite continued prolonged neutropenia in the perioperative period. This experience contrasts with six cases reported in the literature and suggests that surgery can be employed even in patients with profound neutropenia. Thus, in patients who remain persistently septic or who develop clinical deterioration despite medical management or who have other indications for surgical intervention, neutropenia should not be a contraindication to the appropriate or necessary procedure.

Relation between stage of disease and neurobehavioral measures in children with symptomatic HIV disease.

OBJECTIVE: To study the relationships between stage of HIV disease, reflected by CD4+ lymphocyte percentages and p24 antigen levels, and HIV-associated central nervous system (CNS) abnormalities, measured by computed tomography (CT) brain-scan ratings and neurobehavioral tests. DESIGN: Consecutive case series. SETTING: Government medical research center. PATIENTS: Eighty-six previously untreated children with symptomatic HIV-1 disease. RESULTS: CD4% measures correlated significantly with overall CT brain-scan severity ratings (r = -0.45; P < 0.001) as well as with its component parts (cortical atrophy, white matter abnormalities, and intracerebral calcifications); they were of comparable magnitude for vertically and transfusion-infected children. CD4% measures were also associated with the general level of cognitive function (r = 0.32; P < 0.005). Furthermore, patients with detectable serum p24 antigen levels (n = 39) had CT brain scans that were more abnormal than patients with undetectable p24 levels (n = 20; CT abnormality ratings of 21.3 versus 35.9; P < 0.02); similar differences were found for the cortical atrophy and calcification ratings. p24 levels also correlated with the overall CT brain-scan severity rating (r = 0.34; P < 0.01). CONCLUSIONS: Degree of CT brain-scan abnormality and level of cognitive dysfunction were significantly associated with the stage of HIV-1 disease, as reflected by either CD4 leukocyte measures or elevations of p24 antigen. The relation between the CT brain-scan lesions and markers of HIV disease (both CD4 and p24) suggest that these CNS abnormalities are most likely associated with HIV-1 infection, and further support the hypothesis that the interaction between systemic disease progression and CNS manifestations is continuous rather than discrete.

Individual prognoses of long-term responses to antiretroviral treatment based on virological, immunological and pharmacological parameters measured during the first week under therapy.

OBJECTIVE: To predict long-term (12 weeks or longer) virological responses to antiretroviral treatment from measurements made during the first few days on therapy. METHODS: Forty-one HIV-1-infected children were treated with ritonavir for 12 weeks followed by triple drug combination treatment, and the kinetics of virus decay in plasma, ritonavir concentration and CD4 cell counts were measured. A robust multivariate pattern recognition method was used for prediction of the longterm virological responses. RESULTS: The virus decay rate constants calculated from measurements of plasma viral RNA concentrations on the first, second, third, fourth and seventh day on therapy, the drug concentrations in the plasma on day seven, and the pretreatment levels of viral RNA and CD4 cell counts, correlated with long-term levels of plasma HIV-1 RNA. The combination of these parameters contained sufficient information for correct and robust prediction of the long-term response in 88% of the treated children. The predictions of individual responses were stable as demonstrated by a cross-validation analysis, which was highly statistically significant (r=0.87) and specific. CONCLUSION: These results demonstrate that multiple parameters determine the response to antiretroviral therapy and offer a very early measure of individual long-term responses, suggesting that treatment could be optimized after few days of therapy.

Protease inhibitor and triple-drug therapy: cellular immune parameters are not restored in pediatric AIDS patients after 6 months of treatment.

OBJECTIVE: To assess whether treatment of HIV-positive children by antiretroviral drugs for a 6-month period would improve immune function significantly. DESIGN AND METHODS: Immunological assessment of 89 HIV-positive children who received protease inhibitor monotherapy for 12-16 weeks as part of phase I/II studies, followed by triple antiretroviral therapy for an additional 12 weeks, was conducted. Immunological parameters were assessed in vitro at four time points (at enrollment, at weeks 2-4, at weeks 12-16, and at weeks 24-28). Assessments included: cytokine production by monocytes, T-cell proliferation to mitogen or recall antigens (including an HIV antigen) and apoptotic cell death. Plasma levels of tumor necrosis factor (TNF)-alpha and soluble TNF receptor (sTNF-R) were also measured, in addition to CD4+ T-lymphocyte counts and viral load. In addition, limited analyses were performed on samples from 17 children after 120 weeks of therapy, including 104 weeks of triple therapy. RESULTS: At enrollment, the 89 children exhibited severe immune defects. Antiretroviral therapy raised CD4+ T-lymphocyte counts significantly and decreased viral loads. In contrast, the in vitro immune parameters studied were not improved, except for plasma levels of sTNF-RII which decreased in parallel with the decrease in viral load. In addition, there was a trend towards increased skin test reactivity for the ritonavir-treated children. No differences were seen in the immune parameters whether the patients were treated with mono- or triple therapy. Results obtained after 120 weeks of therapy demonstrated that defective interleukin-12 production was not restored by long-term therapy. CONCLUSIONS: After 6 months of therapy, with the exception of decreased sTNF-RII levels, and a trend towards increased skin test reactivity, restoration of several defective cellular immune responses did not occur despite significantly decreased viral loads and increased CD4+ T-lymphocyte counts.

Patterns of infection in patients with aplastic anemia and the emergence of Aspergillus as a major cause of death.

Patterns of infection were studied in 150 patients with aplastic anemia who were admitted to the Clinical Hematology Branch, National Institutes of Health, between January 1978 and December 1989 for immunosuppressive therapy. Sixty percent of the patients were males, 71% were white, their mean age was 33.6 years (median, 27.5; range, 1-75), and 83% had severe aplastic anemia. One hundred three patients developed 1 or more febrile episodes during the study period. The risk factors for developing a febrile episode included a low Absolute Neutrophil Count (ANC) and Absolute Monocyte Count (AMC) at admission and the presence of an indwelling central venous catheter (Hickman-Broviack or Port-A-Cath). A total of 289 febrile events were studied, including unexplained fever (FUO) in 89 (31%), microbiologically documented infection (MBDI) in 137 (47%), and clinically documented infection (CDI) in 63 patients (22%). Compared to documented infections (MBDI) or CDI), FUO events were associated with a higher frequency of rigors, signs and symptoms of serum sickness, and treatment regimens known to cause fevers. None of the FUO events had a fatal outcome, even if the antibiotic therapy was discontinued before day 7. Among CDI events, bacteria were the most commonly defined etiologic agent (67%), followed by fungi (23%), viruses (7%), and parasites (3%). The patterns of bacterial infections in patients with aplastic anemia were similar to those observed in patients with cancer-related neutropenia. Twenty-one patients (15%) developed invasive fungal infections (aspergillus, 11; candida, 7; and both, 3), which were fatal in 19 (90%). Fungal infections accounted for 30% of the secondary infectious events and for 55% of fatal infectious events. The only identifiable risk factors for developing a fungal infection were the degree of neutropenia and monocytopenia at initial admission or final evaluation. Invasive pulmonary aspergillosis developed despite empirical amphotericin B therapy and was associated with a high incidence of fatal pulmonary hemorrhage (10 of 13 patients [77%]). Infection was responsible for 36 (62%) of the deaths observed during the study period and hemorrhage alone for 4 (7%). However, 20 of the patients who died of infection had concomitant hemorrhage. No significant drop in ANC, AMC, or platelet count could be demonstrated during a fatal infectious event as compared to a nonfatal infectious event. Invasive fungal infections, predominantly with aspergillus and candida, emerged in our study as the major causes of mortality in patients with aplastic anemia. Without bone marrow recovery the prognosis associated with invasive mycoses was grave.

Brain growth and cognitive improvement in children with human immunodeficiency virus-induced encephalopathy after 6 months of continuous infusion zidovudine therapy.

The ventricular area at the level of the foramen of Monro was measured from axial x-ray computed tomography (CT) scans obtained prior to and 6 months after the initiation of continuous infusion of zidovudine (ZDV) in eight children with human immunodeficiency virus-induced encephalopathy. Evidence of moderate to severe central atrophy was present on initial CT scans (p less than 0.05). Ventricular area and ventricular brain area ratio (VBR) decreased after ZDV therapy in seven of eight children (mean decrease of 21.5 and 20%, respectively, p less than 0.05). The degree of decrease in VBR correlated with reductions in cerebrospinal fluid (CSF) protein concentration (r = 0.93, p less than 0.01), but not lymphocyte T4 or T8 counts. Intelligence quotients (IQs) improved in all seven children tested (mean improvement of 17.7%, p less than 0.01) and correlated significantly with reductions in CSF protein concentration (r = -0.85, p = 0.003). The magnitude of IQ changes was not significantly correlated with the magnitude of changes in ventricular area. We conclude that the cognitive improvement of HIV encephalopathy seen after 6 months of continuous infusion of ZDV is accompanied by reduction in brain atrophy and decreased CSF protein, suggesting an ameliorating effect of ZDV on the pathogenesis of AIDS encephalopathy in children.

Infectious complications of patients undergoing therapy for acute leukemia: current status and future prospects.

The success of managing the infectious complications of acute leukemia has permitted oncologists to develop new approaches to induction and high-dose therapy. The single most important risk factor for infection is the duration of absolute neutropenia. Historically, most attention was directed towards gram negative aerobes, especially Pseudomonas aeruginosa, but in recent years gram positive bacteria, generally considered to be less virulent, have become the most frequent isolates in most centers. A recent disturbing trend is the isolation of vancomycin-resistant enterococci. A recent controversy has been whether to use empirical vancomycin; the Centers for Disease Control has issued a formal recommendation discouraging empirical vancomycin in the febrile neutropenic patient. Empirical monotherapy has replaced combination therapy in many institutions except where there has been an increase in resistant isolates. In patients who remain profoundly neutropenic, fungal infections represent a serious source of secondary infection, especially species of Candida and Aspergillus. Recently lipid-based formulations of amphotericin B have offered reduced nephrotoxicity. Less toxic antifungals, the azoles, which include fluconazole and itraconazole, offer an attractive alternative to amphotericin B. New patterns of invasive mycoses have emerged, as for example hepatosplenic candidiasis, presenting new problems in diagnosis and therapy. The successful management of virus infections with herpes simplex, cytomegalovirus, varicella zoster, and Epstein Barr virus is based on early recognition and careful attention to prevention.

Fungal infections in the pediatric cancer patient.

Chemotherapy, while undeniably effective in controlling or eradicating a variety of neoplasms, is also accompanied by a number of toxicities. Foremost among these is neutropenia, which places the pediatric cancer patient at risk for serious fungal infections. The fungal organisms most commonly responsible for infection in neutropenic children are Candida, Aspergillus, Mucor, and the Phycomycetes. Common sites of infection include the oral cavity, sinuses, lung, and bloodstream. Recently, candidal infection of the liver was recognized as a growing problem. Diagnosis of deep-seated fungal infections, such as pneumonia and hepatic candidiasis, is extremely difficult, often requiring open-lung or liver biopsy, which a patient's hematologic status may not permit. Because early treatment significantly improves prognosis, empirical antifungal therapy may be indicated in selected patients. Amphotericin B is currently the antifungal agent of choice against most fungal organisms. Antifungal efficacy studies based on animal models of disseminated candidal infection suggest that amphotericin B combined with 5-fluorocytosine (5-FC) is more effective than amphotericin B alone against most deep-seated Candida infections. The investigational drug, fluconazole, appears as effective as amphotericin B plus 5-FC in the prevention and early treatment of disseminated candidiasis, and clinical trials to assess this potentially important role for the new antifungal agent are now being initiated.

The value of protective isolation in preventing nosocomial infections in high risk patients.

Since infection is a major cause of death in the patient whose immune responses have been compromised (immunocompromised patient), considerable attention has been focused on developing methods for the prevention of infection. This has primarily been directed at suppressing or eliminating the host's endogenous microbial burden and in decreasing the acquisition of new organisms. The prevention techniques which have been employed vary in complexity from single-room isolation to elaborate systems utilizing air-filtration and decontamination. The most sophisticated of these regimens is the total protected environment (TPE) consisting of a high-efficiency-particulate-air (HEPA)-filtered laminar air flow room which is surface disinfected and in which the patient is fully decontaminated with oral nonabsorbable antibiotics, cutaneous antisepsis, orificial antibiotics and a semisterile diet. The cumulative data to data have shown that the TPE affords a significant (albeit incomplete) reduction in the incidence of serious infections in severely compromised patients. Such protection from infection permits the delivery of novel therapies which might have been precluded because of consequent hematologic or immunologic toxicity. Nonetheless, the TPE is also elaborate, cumbersome and expensive, and its utilization for patients with immunodeficiency syndromes, bone marrow failure states and cancer depends heavily on the success of available therapy (e.g., immunoreconstitution, transplantation, intensive chemotherapy) for the patient's underlying disorder. Critical evaluation of the TPE and alternative prevention strategies are imperative to assure the effective and appropriate utilization of limited hospital resources.

Treatment of human immunodeficiency virus-infected infants and young children with dideoxynucleosides.

The safety and activity of several antiretroviral agents are being evaluated for treatment of acquired immunodeficiency syndrome (AIDS) in infants and children. Intermittent oral and intravenous regimens and continuous intravenous infusion of the dideoxynucleoside, 3'-azido-3'-deoxythymidine (zidovudine, AZT), have been shown to be beneficial in improving neuro-developmental function and growth velocity in pediatric patients with AIDS. AZT, however, is limited by the associated development of neutropenia and anemia, which frequently necessitates transfusions. Another dideoxynucleoside, 2',3'-dideoxycytidine (ddC), also shows theoretical promise in the treatment of the pediatric AIDS population. This agent is not associated with the hematologic toxicity induced by AZT but does produce a painful sensory peripheral neuropathy. Sequential therapy with AZT and ddC may limit the toxic effects associated with the use of these drugs individually. Dideoxyinosine and soluble recombinant CD4 are two newer antiretroviral agents that are under investigation for the management of AIDS in infants and children. The activity of recombinant CD4 in preventing the transplacental transmission of human immunodeficiency virus is also being evaluated.

Limitations of current antimicrobial therapy in the immunosuppressed host: looking at both sides of the coin.

During the last twenty years there have been considerable advances in the antimicrobial management of the immunosuppressed host. These include the development of antibiotics with broad-spectrum and high bactericidal activity along with the appreciation of the importance of promptly initiating empiric antibiotic therapy when the granulocytopenic patient becomes febrile and continuing them (in some cases with empiric antifungal therapy) until the resolution of granulocytopenia. Nonetheless, infection still remains a major cause of death in compromised hosts and a number of limitations of therapy persist. Included are a limited repertoire of drugs active against fungi (particularly Aspergillus) as well as certain viruses (for example, cytomegalovirus) and the inability to eradicate certain sites of infection (for example, Pseudomonas pneumonia) even with effective agents. Current investigations are focused on developing new antimicrobial agents as well as methods to improve the altered host defenses of immunosuppressed patients, both as adjuvants to therapy and, eventually, as a means to prevent infectious complications.

Emergence of Clostridium tertium as a pathogen in neutropenic patients.

Although usually considered a non-pathogen, Clostridium tertium was isolated from 10 immunosuppressed patients including seven patients with bacteremia. This organism can grow aerobically and can be easily disregarded as a contaminant. It also has a somewhat unusual susceptibility pattern, with significant resistance to the penicillins, cephalosporins, and clindamycin, possibly explaining its emergence in immunocompromised patients already receiving multiple antibiotics.