Human alveolar macrophage cytophilic immunoglobulin G-mediated phagocytosis of protein A-positive staphylococci.

Human alveolar macrophages (AM) have recently been reported to ingest and kill a strain of Staphylococcus (502A) in the absence of opsonins. To further investigate the mechanism of non-opsonic recognition, we studied phagocytosis of 23 clinical and laboratory strains of S. aureus and Staphylococcus epidermidis by AM, and by blood polymorphonuclear leukocytes (PMN) and monocytes (MN). In the absence of opsonins, AM phagocytized 18 protein A-positive but not 5 protein A-negative strains of staphylococci, and the efficiency of phagocytosis directly correlated with the amount of protein A present in the bacterial cell wall (r = 0.86, P less than 0.001). Furthermore, AM rosetted around protein A-coated Sepharose beads, but not around beads without protein A. In contrast, PMN did not phagocytize nonopsonized staphylococci, and did not rosette around either type of Sepharose. MN phagocytized protein A-positive staphylococci, but much less efficiently than AM, and showed some rosetting around protein A-coated Sepharose. The nature of the AM receptor for protein A-positive staphylococci was studied. The surface of AM was positively stained with fluorescein-conjugated antibody to human IgG, but not with IgA- or IgM-specific conjugates. No such surface-immunoglobulins were detected on PMN, and MN were only weakly positive for surface IgG. Pretreatment of AM with F(ab')2 fragments specific for human IgG (anti-Fc) inhibited subsequent phagocytosis of protein A-positive staphylococci. There was no evidence that the AM surface IgG was aggregated or immunecomplexed. From these studies we conclude that human AM possess cytophilic IgG antibodies, which can function as receptors for phagocytosis of protein A-positive staphylococci.

Pilot study of the immunologic effects of recombinant human growth hormone and recombinant insulin-like growth factor in HIV-infected patients.

OBJECTIVE: To study the immunologic effects of recombinant human growth hormone (rhGH), recombinant human insulin-like growth factor type 1 (rhIGF-1), or the combination, in patients with moderately advanced HIV infection. DESIGN: Randomized but not blinded trial. SETTING: Government medical research center. PATIENTS: Twenty-four HIV-infected patients with CD4 cell counts of 100-400 x 10(6)/l who were receiving nucleoside antiretroviral therapy. INTERVENTIONS: Either rhGH, rhIGF-1, or the combination was administered subcutaneously for 12 weeks. MAIN OUTCOME MEASURES: Immunologic parameters, including T-cell subsets and assays of in vitro interleukin (IL)-2 production in response to antigens and mitogens, and safety profile. RESULTS: Plasma IGF-1 levels were low or low-normal prior to treatment and increased with all three therapies. There were no significant changes in CD4 cell counts, RA/RO CD4 cell subsets, natural killer cell function, immunoglobulin levels, or in vitro IL-2 production in response to mitogen or alloantigens. However, there was an upward trend (and for p18IIIB a statistically significant increase) in the in vitro IL-2 production in response to each of five HIV envelope peptides. Potential toxic effects included fatigue, arthralgia, edema, myalgia, and headache. Patients also were noted to have weight gain averaging 4 kg early in the course of treatment. CONCLUSIONS: These results suggest that treatment with rhGH/rhIGF-1 was reasonably well tolerated and that modest improvement in HIV-specific immune function was attained. Further studies will help clarify the therapeutic potential of rhGH/rhIGF-1 as an immunostimulator in the setting of HIV infection.

Comparative studies of two-times-daily versus three-times-daily indinavir in combination with zidovudine and lamivudine.

OBJECTIVES: To compare the efficacy and safety of two-times-daily versus three-times-daily indinavir in combination with zidovudine and lamivudine. DESIGN: Two multicenter, open-label, randomized 24-week studies. METHODS: Adults HIV-1 infection, HIV-1 RNA greater than 10000 copies/ml, and no prior lamivudine or protease inhibitor therapy were eligible. In a pilot study (Study A), patients received indinavir at 800 mg every 8 h, 1000 mg every 12 h, or 1200 mg every 12 h. In a subsequent study (Study B), patients received indinavir at 800 mg every 8 h or 1200 mg every 12 h. All subjects received zidovudine (300 mg) and lamivudine (150 mg) every 12 h. An intent-to-treat analysis was used. RESULTS: In Study A, which enrolled 88 patients, neither HIV-1 RNA nor CD4 cell responses differed significantly between treatment groups at 24 weeks when corrected for multiple comparisons. Study B enrolled 433 patients, but was prematurely discontinued when interim analysis suggested greater efficacy of three-times-daily indinavir. Of the first 87 patients reaching week 24, HIV-1 RNA was less than 400 copies/ml in 91% receiving three-times-daily versus 64% receiving two-times-daily indinavir (P < 0.01). CONCLUSION: Three-times-daily indinavir appears more efficacious than two-times-daily dosing when administered with zidovudine and lamivudine. Two-times-daily indinavir dosing should only be considered in situations characterized by favorable pharmacokinetic drug-drug interactions.

Modeling the long-term outcomes and costs of HIV antiretroviral therapy using HIV RNA levels: application to a clinical trial.

A model was developed to gain insight into the potential clinical and economic impact of antiretroviral therapy for HIV-infected patients. Observed HIV RNA levels and CD4 cell counts are used in the model to estimate the probability that an individual progresses from asymptomatic infection to the first AIDS-defining illness and death and to estimate the total net cost of care and long-term cost-effectiveness of antiretroviral therapy. The model was applied to patients in a clinical trial (Merck protocol 035) that compared the surrogate marker response to triple therapy with indinavir (IDV; 800 mg every 8 hr) plus zidovudine (ZDV; 200 mg every 8 hr) plus lamivudine (3TC; 150 mg twice a day) to double therapy with ZDV+3TC. The model projected that for an individual without AIDS who received triple therapy the progression to AIDS and death would be delayed more than for a patient who received double therapy with ZDV+3TC if no other treatment options were offered. Because of this delay in disease progression, the total discounted cost over the initial 5-year period was projected to be $5100 lower for patients who received triple therapy compared with double therapy if suppression with triple therapy lasts up to 3 years. If suppression with triple therapy lasts up to 5 years, costs were projected to be higher with the triple combination, but 81% of the cost is offset by lower disease costs as a result of fewer patients progressing to AIDS. Over 20 years, total discounted cost was projected to be higher for the triple-therapy regimen primarily because of a longer estimated survival time. At 20 years, the incremental cost per life-year gained by adding IDV to a ZDV+3TC regimen was estimated at $13,229, which is well within the range of other widely accepted medical interventions.

A phase I trial of the pharmacokinetics, toxicity, and activity of KNI-272, an inhibitor of HIV-1 protease, in patients with AIDS or symptomatic HIV infection.

The pharmacokinetics, toxicity, and activity of KNI-272, a transition state inhibitor of HIV-1 protease, was assessed in a phase I trial. After an initial phase in which the pharmacokinetics were assessed, 37 patients with AIDS or symptomatic HIV infection and 100-400 CD4 cells/mm3 were entered in an escalating dose study. KNI-272 was administered four times daily for up to 12 weeks. Oral bioavailability ranged from 22 to 55% and was not appreciably different in the fasting and post-prandial state. The dose limiting toxicity was hepatic transaminase elevation; this could be reduced by escalating the dose over 4 weeks. When administered this way, the maximum tolerated oral dose was 40 mg/kg per day. At the highest two tolerated doses (26.4 and 40 mg/kg per day), there was some evidence of an anti-HIV effect with median decreases of 0.2-0.3 log10 copies/ml plasma HIV RNA; these decreases persisted through 7-8 weeks of treatment. There was an upward trend in the CD4 count at the 40 mg/kg per day dose but not at other doses. Additional studies focused on approaches to improve the therapeutic index of KNI-272 may be warranted.

Impact of alternate definitions of fever resolution on the composite endpoint in clinical trials of empirical antifungal therapy for neutropenic patients with persistent fever: analysis of results from the Caspofungin Empirical Therapy Study.

BACKGROUND: Sensitivity analyses were incorporated in a Phase III study of caspofungin vs. liposomal amphotericin B as empirical antifungal therapy for febrile neutropenic patients to determine the impact of varying definitions of fever resolution on response rates. METHODS: The primary analysis used a 5-part composite endpoint: resolution of any baseline invasive fungal infection, no breakthrough invasive fungal infection, survival, no premature discontinuation of study drug, and fever resolution for 48 h during the period of neutropenia. Pre-specified analyses used 3 other definitions for fever resolution: afebrile for 24 h during the period of neutropenia, afebrile at 7 days post therapy, and eliminating fever resolution altogether from the composite endpoint. Patients were stratified on entry by use of antifungal prophylaxis and risk of infection. Allogeneic hematopoietic stem cell transplants or relapsed acute leukemia defined high-risk patients. RESULTS: In the primary analysis, 41% of patients in each treatment group met the fever-resolution criteria. Low-risk patients had shorter durations of neutropenia but failed fever-resolution criteria more often than high-risk patients. In each exploratory analysis, response rates increased in both treatment groups compared to the primary analysis, particularly in low-risk patients. CONCLUSIONS: Response rates for the primary composite endpoint for both treatment groups in this study were driven by low rates of fever resolution. Requiring fever resolution during neutropenia in a composite endpoint can mask more clinically relevant outcomes.

A case of hyperdynamic shock caused by trimethoprim-sulfamethoxazole in which no tumor necrosis factor or features of anaphylaxis were detected.

An unusual acute hypotensive syndrome has been observed in association with administration of trimethoprim-sulfamethoxazole (TMP-SMZ) to patients with human immunodeficiency virus (HIV) infection. In the 11 cases that have been reported, the syndrome differs from classic anaphylaxis and resembles septic shock. Mediation by tumor necrosis factor (TNF) has been hypothesized, but the mechanism has not been characterized with cytokine assays, and no invasive hemodynamic measurements have been reported. We describe a case of recurrent hyperdynamic shock--without classic features of anaphylaxis, without detectable IgE antibodies against TMP or SMZ, and without detectable levels of TNF--involving an HIV-infected patient rechallenged with TMP-SMZ.

Opsonization of encapsulated Staphylococcus aureus: the role of specific antibody and complement.

Previous studies of encapsulated Staphylococcus aureus have shown that the opsonins of normal, nonimmune human serum (complement factor C3 and IgG) bind beneath the capsule, i.e., on the cell wall, and when bound at this site these opsonins are not effective in promoting phagocytosis of the bacteria by polymorphonuclear leukocytes (PMN). In this investigation immune antibody was added to human serum to effect opsonization of encapsulated S. aureus. Opsonization was assessed by quantitating the uptake of 3H-labeled staphylococci by human PMN, and the amount of C3 fixation to bacteria was measured in a quantitative fluorescent immunoassay. Low levels of immune antibody (IgG) effectively opsonized encapsulated S. aureus when added to fresh but not to heated serum; phagocytosis of the staphylococci was mediated via pronase-sensitive membrane receptors (presumably C3b receptors) of PMN. Experiments with C2-, C3-, or C5-deficient human sera revealed that C3 was required for opsonization and that activation of C3 was mediated via the alternative complement pathway. Encapsulated S. aureus bound significantly less C3 than unencapsulated strains in diluted normal serum; addition of immune antibody, however, increased C3 fixation 4.7-fold (p less than 0.005). Immunoelectron microscopy localized C3 throughout the capsule as well as on the staphylococcal cell wall when bacteria had been opsonized in human serum with immune antibody. Without immune antibody, C3 binding was restricted to the cell wall. At approximately 10-fold higher levels of immune antibody, opsonization and phagocytosis of encapsulated S. aureus was independent of complement and pronase-sensitive receptors on PMN. These studies show that, in addition to immune antibody, the alternative pathway of complement plays an important role in the opsonization of encapsulated S. aureus strains and suggest that complement may be crucial to the in vivo clearance of these organisms.

Safety and tolerability of caspofungin acetate in the treatment of fungal infections.

Caspofungin acetate is the first member of the novel echinocandin class of antifungal drugs to be marketed in the United States. It has recently been approved for use in patients with invasive aspergillosis who are refractory to or intolerant of conventional therapy. Accordingly, its safety profile is particularly important to review. The safety and tolerability of caspofungin have been examined in 623 persons, including 295 patients who received >/= 50 mg/day for at least one week in clinical studies. In the 263 patients, given caspofungin in randomized double-blind active-control trials to date, there have been no serious clinical or laboratory drug-related adverse events; caspofungin was discontinued in only 2% of these patients because of drug-related adverse experiences. Caspofungin may have potentially important drug interactions with cyclosporine and tacrolimus.

Five-year follow-up of a phase I study of didanosine in patients with advanced human immunodeficiency virus infection.

Starting in 1988, 72 patients with advanced human immunodeficiency virus (HIV) infection were enrolled in a phase I study of didanosine at the National Cancer Institute. Beginning in 1992, patients with decreases in CD4 cell counts could switch to a combination of zidovudine and didanosine. The estimated median survival for all patients was 28 months (95% confidence interval, 23-46). However, for patients whose entry CD4 cell counts were 100-300/mm3, the estimated 4-year survival was 80%. Baseline CD4 and CD8 cell counts, hemoglobin, lymphocytes, sedimentation rates, diagnosis of AIDS, and fever were significant predictors of overall survival. Principal toxicities were pancreatitis and peripheral neuropathy; no new toxicities were seen with extended didanosine treatment that had not been observed in shorter-term studies. This 5-year follow-up shows that didanosine can be tolerated for > 4 years in some patients with advanced HIV infection and may have particular long-term utility in patients with moderately advanced immunosuppression.

Size heterogeneity among antigenically related Giardia lamblia variant-specific surface proteins is due to differences in tandem repeat copy number.

Giardia lamblia undergoes antigenic variation by modulating the expression of the different genes that comprise the trophozoite's variant-specific surface protein (VSP) repertoire. We studied an epitope that is conserved among VSPs expressed by cloned trophozoite lines derived from the independent G. lamblia isolates WB, G3M, Be-2, and CAT. The epitope recognized by monoclonal antibody 6E7 lies entirely within the region of tandemly repeated 65-amino-acid units that is characteristic of these size-variant VSPs. Northern (RNA) hybridization, cDNA cloning, and DNA sequence analysis indicate that size heterogeneity among these VSPs is due to differences in the number of repetitive units.

Differences in phagocytosis and killing by alveolar macrophages from humans, rabbits, rats, and hamsters.

Phagocytosis and killing by alveolar macrophages from humans, rabbits, rats, and hamsters, were compared in vitro. In the absence of serum opsonins, human alveolar macrophages could phagocytize Staphylococcus aureus Cowan I (protein A positive), but not S. aureus EMS (protein A negative) or Pseudomonas aeruginosa MN. In contrast, rabbit, rat, and hamster alveolar macrophages did not phagocytize S. aureus Cowan I or other nonopsonized bacteria. Human alveolar macrophages, but not other species, stained positively with fluorescein isothiocyanate-conjugated protein A. When opsonized bacterial were studied, phagocytosis by human, rabbit, and hamster alveolar macrophages was found to be mediated by both Fc and C3 receptors. However, only Fc receptor-mediated phagocytosis of bacteria was demonstrated for rat alveolar macrophages. Differences were also found in the kinetics of bacterial killing by alveolar macrophages from different species. Human and rabbit alveolar macrophages rapidly killed opsonized S. aureus Cowan I. However, bacterial killing by hamster alveolar macrophages proceeded at a slower rate, and rat alveolar macrophages completely failed to kill S. aureus. These significant differences in the function of alveolar macrophages from four different species emphasize the need to document the appropriateness of animal models before using them to predict the biological activities of human alveolar macrophages.

Human fibronectin binding to staphylococcal surface protein and its relative inefficiency in promoting phagocytosis by human polymorphonuclear leukocytes, monocytes, and alveolar macrophages.

The interaction between human fibronectin and 17 strains of staphylococci was studied in an attempt to elucidate the staphylococcal cell wall component(s) involved in fibronectin binding and to determine the influence of fibronectin upon phagocytosis by three types of phagocytic cells. Purified, radiolabeled fibronectin bound to a similar degree to six laboratory strains and three fresh clinical isolates of Staphylococcus aureus; similar binding of fibronectin was found with S. aureus strains deficient in cell wall teichoic acid or clumping factor and coagulase, as well as with three strains of S. epidermidis. There was minimal binding of fibronectin to encapsulated S. aureus and to Escherichia coli. Fibronectin bound to intact cells and to a crude cell wall preparation of S. aureus H, but not to purified cell walls or peptidoglycan. Trypsinization of staphylococci prevented subsequent fibronectin binding, but binding did not correlate well with the protein A content in S. aureus cell walls. At physiological concentrations, fibronectin binding to staphylococci did not promote phagocytosis of bacteria by human polymorphonuclear leukocytes, monocytes, or alveolar macrophages. Also, depletion of fibronectin from normal human serum did not result in a measurable loss of opsonic activity for staphylococci. It is concluded that fibronectin binding to staphylococci involves a surface protein shared among strains of S. aureus and S. epidermidis, and that in comparison to C3b and IgG, fibronectin plays a relatively minor role as an opsonin for staphylococci.

A pilot study of sequential therapy with zidovudine plus acyclovir, dideoxyinosine, and dideoxycytidine in patients with severe human immunodeficiency virus infection.

A pilot study was initiated to explore a sequential combination antiretroviral regimen in 21 patients with AIDS or advanced human immunodeficiency virus (HIV) infection, who had received little or no prior anti-HIV therapy. The mean entry CD4 cell count was 184/mm3. Patients received 3-week cycles consisting of zidovudine plus acyclovir, dideoxyinosine, and dideoxycytidine for 1 week each. Overall, the regimen was well tolerated for up to 3 years. The principal toxicities were anemia, nausea, and vomiting; 1 patient developed retinal lesions. The mean CD4 cell count reached a peak of 64 cells/mm3 above baseline at week 8 (P = .005 compared to baseline) and remained above baseline for > 40 weeks. Patients also gained weight and had decreases in serum HIV p24 antigen. Eight patients developed opportunistic infections or tumors. Only 4 patients died during 3 years of follow-up. This regimen appears to be generally tolerable and to have anti-HIV activity. Additional studies will be needed, however, to learn how to best combine the available agents in patients with HIV infection.

Pharmacokinetics of indinavir combined with low-dose ritonavir in human immunodeficiency virus type 1-infected children.

So far, no pediatric doses for indinavir combined with ritonavir have been defined. This study evaluated the pharmacokinetics of 400 mg of indinavir/m(2) combined with 125 mg of ritonavir/m(2) every 12 h (q12h) in 14 human immunodeficiency virus type 1-infected children. The area under the concentration-time curve from 0 to 24 h and the minimum concentration of drug in serum for indinavir were similar to those for 800 mg of indinavir-100 mg of ritonavir q12h in adults, while the maximum concentration of drug in serum was slightly decreased, with geometric mean ratios (90% confidence intervals in parentheses) of 1.1 (0.87 to 1.3), 0.96 (0.60 to 1.5), and 0.80 (0.68 to 0.94), respectively.

A randomized pilot study of alternating or simultaneous zidovudine and didanosine therapy in patients with symptomatic human immunodeficiency virus infection.

A randomized pilot study comparing alternating and simultaneous regimens of zidovudine and didanosine (ddl) was conducted in 41 patients with AIDS or symptomatic human immunodeficiency virus (HIV) infection. Patients on each regimen received the same overall amounts of zidovudine and didanosine over time. CD4 cell counts in patients on the simultaneous regimen reached a maximum (mean +/- SE) of 108 +/- 16/mm3 above baseline (two-tailed P < or = .0001) and were significantly higher than in patients on the alternating regimen at all time points during weeks 6-45. At 54 weeks, the CD4 cell counts in the patients on the simultaneous regimen were still 40 +/- 19/mm3 above baseline. Patients on the simultaneous regimen also had significantly greater weight gain. While toxicities were generally mild and comparable between the regimens, 1 patient on the simultaneous regimen died of pancreatitis and lactic acidosis. Thus, simultaneous therapy provided more sustained elevations in CD4 cells than alternating therapy over 1 year and may be worth exploring in larger controlled trials.

Long-term virologic and immunologic responses in human immunodeficiency virus type 1-infected children treated with indinavir, zidovudine, and lamivudine.

Virologic and immunologic responses were examined for 33 human immunodeficiency virus (HIV)-infected children who participated for > or = 96 weeks in a phase 1/2 protocol of 16 weeks of indinavir monotherapy, followed by the addition of zidovudine and lamivudine. At week 96, a median increase of 199 CD4+ T cells/microL and a median decrease of 0.74 log(10) HIV RNA copies/mL were observed. The relationship between control of viral replication and CD4) T cell count was examined. Patients were categorized into 3 response groups on the basis of duration and extent of control of viral replication. Of 21 children with a transient decrease in virus load of > or = 0.7 log(10) HIV RNA copies/mL from baseline, 7 experienced sustained increases in CD4+, CD4+ CD45RA+, and CD4+ CD45RO+ T cell counts. CD4+ CD45RA+ (naive) T cells were the major contributor to CD4+ T cell expansion. Continued long-term immunologic benefit may be experienced by a subset of children, despite only transient virologic suppression.