A randomized study of the utility of human immunodeficiency virus RNA measurement for the management of antiretroviral therapy.

To compare frequent measurement with infrequent measurement of human immunodeficiency virus (HIV) RNA levels in the management of antiretroviral therapy, we conducted a clinical strategy study of 206 HIV-infected patients who had <500 CD4 cells/mm(3). Patients were randomized (1.5:1) to undergo frequent monitoring (at baseline and every 2 months) or infrequent monitoring (at baseline and twice yearly), with CD4 cell counts determined every 2 months. Patients received unrestricted antiretroviral therapy. In the primary analysis (at month 6), the frequent group had a mean HIV RNA reduction (+/- standard deviation) of 0.93+/-0.79 log(10) copies/mL, versus 0.48+/-0.83 log(10) copies/mL for the infrequent group (P=.0002). A trend (P=.1) toward improved survival was seen in the frequent group. Given this improved virological response, more frequent HIV RNA measurement than is recommended in published guidelines (every 3-4 months) may be appropriate.

Antibody from patients with acute human immunodeficiency virus (HIV) infection inhibits primary strains of HIV type 1 in the presence of natural-killer effector cells.

The partial control of viremia during acute human immunodeficiency virus type 1 (HIV-1) infection is accompanied by an HIV-1-specific cytotoxic T-lymphocyte (CTL) response and an absent or infrequent neutralizing antibody response. The control of HIV-1 viremia has thus been attributed primarily, if not exclusively, to CTL activity. In this study, the role of antibody in controlling viremia was investigated by measuring the ability of plasma or immunoglobulin G from acutely infected patients to inhibit primary strains of HIV-1 in the presence of natural-killer (NK) effector cells. Antibody that inhibits virus when combined with effector cells was present in the majority of patients within days or weeks after onset of symptoms of acute infection. Furthermore, the magnitude of this effector cell-mediated antiviral antibody response was inversely associated with plasma viremia level, and both autologous and heterologous HIV-1 strains were inhibited. Finally, antibody from acutely infected patients likely reduced HIV-1 yield in vitro both by mediating effector cell lysis of target cells expressing HIV-1 glycoproteins and by augmenting the release of beta-chemokines from NK cells. HIV-1-specific antibody may be an important contributor to the early control of HIV viremia.

Osteoclasts formed by measles virus-infected osteoclast precursors from hCD46 transgenic mice express characteristics of pagetic osteoclasts.

Pagetic osteoclasts (OCLs) are abnormal in size and contain paramyxoviral-like nuclear inclusions that cross-react with antibodies to measles virus (MV). However, the role that MV infection plays in Paget's disease is unknown, because no animal model of Paget's disease is available. Therefore, we targeted a cellular MV receptor, human CD46 (hCD46), to cells in the OCL lineage in transgenic mice using the mouse tartrate-resistant acid phosphatase (TRAP) gene promoter. In vitro infection of OCL precursors from hCD46 transgenic mice with MV significantly increased OCL formation in bone marrow cultures. The numbers of TRAP-positive mononuclear cells and CFU-GM, the earliest identifiable OCL precursor, were also significantly increased. MV-infected OCLs formed from hCD46 marrow were increased in size, contained markedly increased numbers of nuclei, and had increased bone-resorbing capacity per OCL compared with OCLs formed from marrow of nontransgenic littermates. Furthermore, IL-6 and 24-hydroxylase messenger RNA expression levels were increased in MV-infected hCD46 transgenic mouse bone marrow cultures. Treatment of MV-infected hCD46 marrow cultures with a neutralizing antibody to IL-6 blocked the increased OCL formation seen in these cultures. These data demonstrate that MV infection of OCL precursors results in OCLs that have many features of pagetic OCLs, that the enhanced OCL formation is in part mediated by increased IL-6 expression induced by MV infection, and suggest that the hCD46 transgenic mouse may be a useful model for examining the effects of MV infection on OCL formation in vivo.

Relationship between antibody-dependent cellular cytotoxicity, plasma HIV type 1 RNA, and CD4+ lymphocyte count.

To explore the role of antibody-dependent cellular cytotoxicity (ADCC) in controlling HIV-1 infection, ADCC was compared with plasma RNA and CD4+ cell count in 40 patients not receiving antiretroviral therapy and in seven patients after the initiation of treatment. Among untreated patients, ADCC effector cell function of peripheral blood mononuclear cells, measured by (51)Cr release assay, correlated inversely with viral load (R = -0.42, p = 0.007) and directly with CD4+ cell count (R = 0.52, p = 0.001). On the other hand, HIV-1-specific ADCC antibody level correlated directly with viral load, but only among patients with high CD4+ cell counts. Therapy-induced changes in ADCC effector cell function correlated strongly with changes in CD4+ cell count (R = 0.86, p = 0.014), whereas there was no consistent pattern of change in ADCC antibody with therapy. In a novel assay, ADCC reduced virus yield from CD4+ lymphocytes infected with a primary HIV isolate. ADCC may contribute to control of viremia, and CD4+ lymphocytes likely play a role in ADCC effector and antibody functions.

Sequencing of protease inhibitor therapy: insights from an analysis of HIV phenotypic resistance in patients failing protease inhibitors.

OBJECTIVE: To characterize the pattern of HIV-1 susceptibility to protease inhibitors in patients failing an initial protease inhibitor-containing regimen. DESIGN: A cross-sectional analysis of antiretroviral susceptibility. SETTING: HIV clinics in six metropolitan areas. PATIENTS: Eighty-eight HIV-infected adults with HIV RNA > 400 copies/ml after > or = 6 months of antiretroviral therapy, including the use of one protease inhibitor for > or = 3 months. MEASUREMENTS: The frequency and magnitude of decreased susceptibility, measured with a phenotypic assay using recombinant constructs, to five protease inhibitors. Decreased susceptibility was defined as > 2.5-fold increase in the 50% inhibitory concentration (IC50) compared with drug sensitive control virus. RESULTS: At study entry, patients were being treated with nelfinavir (63%), indinavir (25%), or another protease inhibitor (11%). HIV isolates from these patients were susceptible (fold change < 2.5) to all five protease inhibitors in 18% of patients and to none in 8%. Isolates from patients receiving nelfinavir were less likely to have reduced susceptibility to other protease inhibitors than isolates from patients treated with indinavir (P < 0.001) or one of the other three agents (P < 0.001), even after adjustment for the duration of prior protease inhibitor use. Reduced susceptibility to saquinavir and amprenavir was observed significantly less frequently than for the other protease inhibitors. CONCLUSION: The frequency of protease inhibitor cross-resistance and the magnitude of changes in susceptibility varied according to the initial protease inhibitor used in the failing treatment regimen. Significantly less protease inhibitor cross-resistance was demonstrated for isolates from patients failing a nelfinavir-containing regimen compared with those from patients receiving other protease inhibitors.

Antibody inhibition of cytomegalovirus: the role of natural killer and macrophage effector cells.

To explore mechanisms by which antibody might inhibit cytomegalovirus (CMV), we measured the ability of intravenous CMV-IgG (CytoGam) to reduce viral yield in the presence of effector cells. Foreskin fibroblasts were infected with a clinical strain of CMV, and CytoGam was added along with effector cells consisting of either unfractionated peripheral blood mononuclear cells (PBMCs), natural killer (NK) cells, or macrophages. The combination of CytoGam and either of the effector cell types markedly inhibited established CMV infection in vitro. In addition, CytoGam combined with effector cells protected the monolayer from CMV-induced cytopathic effects. Antibody-dependent, effector cell-mediated functions may underlie the ability of CytoGam to prevent or modulate CMV infection in vivo.

Sex-associated differences in the antibody-dependent cellular cytotoxicity antibody response to measles vaccines.

In some countries, excessive non-measles-related mortality has been observed among female recipients of high-titer measles vaccines. We determined if differences in the immune response to measles vaccines underlie the excessive female mortality by measuring the measles virus (MV)-specific antibody-dependent cellular cytotoxicity (ADCC) antibody response in 65 3-year-old Gambian children immunized with Edmonston-Zagreb medium-titer (EZ) or Schwarz standard vaccines during infancy. Among the 20 females and 22 males with undetectable anti-MV antibodies at the time of immunization, females had significantly lower ADCC than males (median cytotoxicities of 1/100 serum dilutions = 8.4 and 12%, respectively; P = 0.04). This sex-associated difference was present only among the six female and seven male recipients of EZ vaccine (median cytotoxicities = 5.1 and 19.0%, respectively; P = 0.02). There were no significant sex-associated differences in neutralizing antibody activity. Decreased ADCC antibody activity may contribute to the lower survival rate observed in females receiving high-titer measles vaccination.

Clinical isolates of measles virus use CD46 as a cellular receptor.

Laboratory strains of measles viruses (MV), such as Edmonston and Halle, use the complement regulatory protein CD46 as a cell surface receptor. The receptor usage of clinical isolates of MV, however, remains unclear. Receptor usage by primary patient isolates of MV was compared to isolates that had been passaged on a variety of tissue culture cell lines. All of the isolates could infect cells in a CD46-dependent manner, but their tropism was restricted according to cell type (e.g., lymphocytes versus fibroblasts). The results indicate that patient isolates that have not been adapted to tissue culture cell lines use CD46 as a receptor. In addition, passaging primary MV patient isolates in B95-8 cells selected variants that had alternate receptor usage compared to the original isolate. Thus, changes in receptor usage by MV are dependent upon the cell type used for isolation. Furthermore, our results confirm the relevance of the CD46 receptor to natural measles infection.

Antibody-dependent cellular cytotoxicity independently predicts survival in severely immunocompromised human immunodeficiency virus-infected patients.

The exact immune defects leading to human immunodeficiency virus (HIV)-associated opportunistic infections, malignancies, and death are unknown. In this study, the relationship between survival and 2 immune functions, cytomegalovirus-specific antibody-dependent cellular cytotoxicity (ADCC) and natural killer (NK) activity, was determined by using peripheral blood mononuclear cells from 39 severely immunocompromised patients (median CD4 count, 7). Median follow-up was 414 days; 15 subjects died and 24 remained alive. In a Kaplan-Meier analysis, high baseline ADCC (>median) was associated with improved survival (P=.05). A similar trend was observed for NK activity (P=.1). In a multivariate model controlling for baseline CD4 cell count, HIV RNA, and use of protease inhibitors during follow-up, high ADCC, but not high NK activity, remained significantly associated with a lower risk of death (relative risk, 0.18; 95% confidence interval, 0.05-0.75). ADCC may be an important determinant of disease progression independently of anti-retroviral therapy, CD4 cell count, and HIV RNA.

Efficacy of azithromycin in prevention of Pneumocystis carinii pneumonia: a randomised trial. California Collaborative Treatment Group.

BACKGROUND: Azithromycin in combination with sulphonamides is active against Pneumocystis carinii pneumonia (PCP) in animals. We assessed the clinical efficacy of azithromycin for PCP prophylaxis in human beings. METHODS: We identified HIV-1-infected patients with PCP during a prospective randomised trial comparing azithromycin, rifabutin, and the two drugs in combination for prevention of disseminated Mycobacterim avium infection. Patients had CD4-cell counts less than 100/microL at entry and received PCP prophylaxis according to the standard practice of their clinician. Analysis was by intention to treat. FINDINGS: Patients receiving azithromycin, either alone (n=233) or in combination with rifabutin (n=224), had a 45% lower risk of developing PCP than those receiving rifabutin alone (n=236; p=0.008). Compared with rifabutin alone, hazard ratio for azithromycin was 0.54 (95% CI 0.32-0.94), for azithromycin plus rifabutin was 0.55 (0.32-0.94), and for regimens containing azithromycin was 0.55 (0.35-0.86). The most common side-effects involved the gastrointestinal tract with dose-limiting toxicities, and were mainly seen in patients receiving combination therapy. INTERPRETATION: Azithromycin as prophylaxis for M. avium complex disease provides additional protection against P. carinii over and above that of standard PCP prophylaxis. Use of azithromycin is beneficial only as primary prophylaxis.

The value of patient-reported adherence to antiretroviral therapy in predicting virologic and immunologic response. California Collaborative Treatment Group.

OBJECTIVE: To correlate self-reported antiretroviral adherence with virologic suppression. DESIGN: Prospective observational study of adherence to therapy nested in a randomized comparative trial of frequent versus infrequent monitoring of plasma HIV RNA. SETTING: Five university-affiliated HIV clinics. PATIENTS: A group of 173 HIV-infected patients with a mean baseline CD4 count of 142 x 10(6) cells/l (range 3-515) of whom 164 and 119 completed adherence questionnaires at 2 and 6 months, respectively. INTERVENTION: Individualized, unrestricted antiretroviral therapy. MEASUREMENTS: Patients were classified into four groups by adherence to therapy in the previous 4 weeks (< 80%, 80-95%, 95-99%, 100%). Plasma HIV RNA levels and CD4 lymphocyte counts were measured bimonthly. RESULTS: Recreational drug or alcohol use was associated with decreased adherence, whereas frequency of HIV RNA monitoring, demographic variables, (age, gender, education, and risk group) and stage of disease had no effect. Greater HIV suppression at 6 months was seen across four categories of increasing adherence (P = 0.009 for linear trend). Patients reporting < 80% adherence at 6 months had a 0.2 log10 copies/ml increase in HIV RNA and a loss of 19 x 10(6) CD4 cells/l compared with a 1.1 log10 copies/ml decrease in HIV RNA and an increase of 72 x 10(6) CD4 cells/l in those reporting 100% adherence (P = 0.02). CONCLUSION: Self-reported poor adherence (< 80%) and drug or alcohol use predicted non-response of HIV RNA at 6 months of antiretroviral therapy.

Prophylaxis with weekly versus daily fluconazole for fungal infections in patients with AIDS.

We compared the efficacy of a 400-mg once-weekly dosage versus a 200-mg daily dosage of fluconazole for the prevention of deep fungal infections in a multicenter, randomized, double-blind trial of 636 human immunodeficiency virus-infected patients to determine if a less intensive fluconazole regimen could prevent these serious but relatively infrequent complications of AIDS. In the intent-to-treat analysis, a deep fungal infection developed in 17 subjects (5.5%) randomly assigned to daily fluconazole treatment and in 24 (7.7%) given weekly fluconazole during 74 weeks of follow-up (risk difference, 2.2%; 95% confidence interval [CI], -1.7% to 6.1%). Thrush occurred twice as frequently in the weekly versus daily fluconazole recipients (hazard ratio, 0.59; 95% CI, 0.40-0.89), and in a subset of patients evaluated, fluconazole resistance was infrequent. Fluconazole administered once weekly is effective in reducing deep fungal infections in patients with AIDS, but this dosage is less effective than the 200-mg-daily dosage in preventing thrush.

In vitro reduction of virus infectivity by antibody-dependent cell-mediated immunity.

Antibody-dependent cellular cytotoxicity (ADCC), an important defense against viral infections, is generally measured in 51Cr-release assays. However, the effect of ADCC on viral burden is more relevant in vivo. An assay was developed to determine the impact of antibody and cytotoxic cells on reducing the amount of measles virus cultured from infected cells. Although the components of this assay are the same as those involved in ADCC, the endpoint is a reduction in virus infectivity rather than cytotoxicity. The immune function measured in the assay has therefore been termed antibody-dependent cell-mediated immunity (ADCMI). Measles virus-infected Raji cells and blood mononuclear cells served as target and effector cells, respectively. Effector cells were incubated with antibody-labeled or unlabeled target cells for 24 h, and virus infectivity determined. Adding effector cells to unlabeled target cells reduced virus titer by 81.8%. Labeling target cells with measles-seronegative serum had little further effect. However, labeling target cells with measles-seropositive serum reduced infectivity an additional 96.5%. By allowing serum to remain in the supernatant fluid after labeling target cells, neutralizing and cell-mediated antibody functions were simultaneously measured. Finally, arming cytokine-activated effector cells with measles-seropositive serum also reduced virus infectivity. This novel assay provides an important tool for evaluating the anti-viral effects mediated by antibody and effector cells.

Human immunodeficiency virus replication in AIDS patients with Mycobacterium avium complex bacteremia: a case control study. California Collaborative Treatment Group.

The development of opportunistic infections and the administration of vaccines have been associated with transient increases of human immunodeficiency virus (HIV) RNA plasma levels in HIV-infected patients. To determine the relationship between Mycobacterium avium complex (MAC) bacteremia and HIV RNA levels, HIV RNA levels in patients who developed MAC bacteremia (cases) were compared with levels in patients who remained free of MAC disease (controls). Cases and controls were matched for CD4 cell count, prophylaxis against MAC disease, antiretroviral therapy, and duration of follow-up. Mean baseline HIV RNA levels were 4.8 log10 copies/mL in cases and 4.6 log10 copies/mL in controls (P = 0.22). HIV RNA levels increased by a median of 0.4 log in cases but not controls at the time of MAC bacteremia (P = 0.01). In AIDS patients, the onset of MAC bacteremia is associated with a modest but significant increase in serum HIV RNA levels. Increased HIV replication may contribute to the higher mortality associated with MAC bacteremia.

Lymphokine-activated cytotoxicity in peripheral blood mononuclear cells of severely immunocompromised HIV-infected patients.

The authors determined the natural killer (NK) and lymphokine-activated killer (LAK) activities of peripheral blood mononuclear cells (PBMCs) from a severely immunocompromised (CD4 cell counts < 100/mm3) group of AIDS patients, using K562 and U937 target cells. An increase in cytotoxicity was observed in the PBMCs of all 17 patients following a 48 h incubation with the combination of 400 U/ml of recombinant gamma interferon plus 20 U/ml of natural interleukin-2. Although NK and LAK activities were significantly higher in healthy controls than in patients, patients' LAK activity was higher than the NK activity of controls. The authors also demonstrated that the use of medium containing fetal bovine serum, when compared with medium containing autologous serum, increases NK activity without affecting LAK activity. Lymphokine augmentation of cytotoxicity is achievable in severely immunocompromised AIDS patients and might be of benefit in delaying opportunistic infections and malignancies.

Predominance of detrimental humoral immune responses to HIV-1 in AIDS patients with CD4 lymphocyte counts less than 400/mm3.

The humoral immune response to human immunodeficiency virus type 1 (HIV-1) was studied in 25 AIDS patients with CD4 lymphocyte counts of less than 400/mm3. Humoral immune responses against tissue culture adapted strains of HIV-1, and two limited-passage patient isolates were investigated. Total anti-HIV antibody levels were not significantly different between different individuals. Neutralizing titres against HIVLA1 and HIVSF2 were 10- to 100-fold higher than against clinical isolates. The complement-mediated, antibody-dependent enhancement of HIV-1 infection titre was high (mean 1:14,000). Antibody-complement mediated cytotoxicity of both HIVLA1 and HIVSF2 was ineffective using human complement as a complement source. The antibody-dependent, cell-mediated cytotoxicity (ADCC) activity varied against the four isolates with tissue culture-adapted strains being more susceptible than clinical isolates. Finally, an ADCC effector cell function, natural killer or NK activity, was measured for all 25 patients, and NK activity of patients was decreased by nearly 75% compared to uninfected individuals. In summary, beneficial humoral immune responses are low in HIV-1 infected individuals with CD4 counts of less than 400/mm3 if the in vitro assay system is constructed to best mimic the in vivo situation. These results suggest that the lack of functional antibody responses to HIV may play an important role in viral pathogenesis.

Prophylaxis against disseminated Mycobacterium avium complex with weekly azithromycin, daily rifabutin, or both. California Collaborative Treatment Group.

BACKGROUND: Azithromycin is active in treating Mycobacterium avium complex disease, but it has not been evaluated as primary prophylaxis in patients with human immunodeficiency virus (HIV) infection. Because the drug is concentrated in macrophages and has a long half-life in tissue, there is a rationale for once-weekly dosing. METHODS: We compared three prophylactic regimens in a multicenter, double-blind, randomized trial involving 693 HIV-infected patients with fewer than 100 CD4 cells per cubic millimeter. The patients were assigned to receive rifabutin (300 mg daily), azithromycin (1200 mg weekly), or both drugs. They were monitored monthly with blood cultures for M. avium complex. RESULTS: In an intention-to-treat analysis, the incidence of disseminated M. avium complex infection at one year was 15.3 percent with rifabutin, 7.6 percent with azithromycin, and 2.8 percent with both drugs. The risk of the infection in the azithromycin group was half that in the rifabutin group (hazard ratio, 0.53; P = 0.008). The risk was even lower when two-drug prophylaxis was compared with rifabutin alone (hazard ratio, 0.28; P<0.001) or azithromycin alone (hazard ratio, 0.53; P = 0.03). Among the patients in whom azithromycin prophylaxis was not successful, 11 percent of M. avium complex isolates were resistant to azithromycin. Dose-limiting toxic effects were more common with the two-drug combination than with azithromycin alone (hazard ratio, 1.67; P=0.03). Survival was similar in all three groups. CONCLUSIONS: For protection against disseminated M. avium complex infection, once-weekly azithromycin is more effective than daily rifabutin and infrequently selects for resistant isolates. Rifabutin plus azithromycin is even more effective but is not as well tolerated.

Age, sex, and household exposure are associated with the acute measles-specific antibody-dependent cellular cytotoxicity antibody response.

To determine whether functional antibody responses correlate with factors associated with severe measles, measles-specific antibody-dependent cellular cytotoxicity (ADCC) and neutralizing antibodies were measured in 114 Filipino children with measles. Children > 24 months old were more likely to have ADCC antibody in acute sera than were those < or = 24 months (odds ratio = 3.6, 95% confidence interval = 1.7-7.8). This age-related difference in ADCC prevalence was most apparent between younger and older girls. Among children < or = 24 months, a higher prevalence of ADCC antibody was associated with male sex, absence of lymphopenia, and household exposure to measles. The presence of ADCC antibody was not associated with malnutrition or diarrhea. Neutralizing antibody titers were lower in children with lymphopenia but showed no relationship with the other variables. Thus, the ADCC antibody response is associated with some risk factors related to measles severity. Attenuation of this response may contribute to the severity of infection.

Functional activities of 20 human immunodeficiency virus type 1 (HIV-1)-specific human monoclonal antibodies.

Antibodies that are useful in the treatment of HIV infection should result in virus neutralization or lysis of infected cells but should not enhance infection. In this study, the potential clinical use of 20 HIV-1-specific human monoclonal antibodies (HuMAbs) was determined by measuring their enhancing (C-ADE) activities using HIVLAI as the target virus. Two HuMAbs mediated both C-ADE and ADCC, two exclusively neutralized, and five exclusively mediated ADCC. Ten HuMAbs demonstrated no activity in any of the three assays. Three antibodies that neutralized HIVLAI were tested against HIVSF2; all three also neutralized HIVSF2. Four of five HuMAbs mediating ADCC against HIVLAI that were also tested against HIVSF2 had ADCC activity against HIVSF2. These results demonstrate that many HuMAbs have unique functions, allowing the separation of potentially beneficial and harmful activities. Combinations of HuMAbs with ADCC and neutralizing functions may have therapeutic utility.