Effect of zidovudine on serum human immunodeficiency virus antigen levels in symptom-free subjects

Zidovudine treatment for anti-HIV positive haemophiliacs

Twenty haemophiliacs (17 CDC group IV and 3 CDC group II) were treated with zidovudine for a median of 37 weeks (range 10-66). Eight (40%) tolerated zidovudine without a dose change. Two patients died and five patients (29%) developed opportunist infections. Haematological toxicity occurred in ten CDC IV patients (59%) but only one case of sepsis occurred in 101 episodes of documented granulocytopenia. Thrombocytopenia responded to treatment with zidovudine in four of five patients. It is concluded that zidovudine is beneficial for symptomatic haemophiliacs and although the haematological toxicity is high, it is mostly asymptomatic, reversible and well tolerated. Two of the three CDC II patients treated with zidovudine progressed to CDC IV, but had low initial T4 lymphocyte counts and were P24 antigen positive.

New methods for the detection of HIV

In the past few years, several strides have been made in the ability to detect the presence of HIV-1 and HIV-2. This article discusses recent advances in serologic testing, including routine ELISA and Western blot tests, rapid HIV tests, home collection kits, and HIV tests using nonserum samples. The clinical application of nucleic acid-based tests also is discussed. Finally, appropriate use of these tests in both acute HIV-1 infection and in infants is reviewed.

Carrier rate of zidovudine-resistant HIV-1: the impact of failing therapy on transmission of resistant strains

OBJECTIVE

Because maintenance of treatment success in HIV-1 infection requires viruses to remain therapy sensitive in drug-naive seropositive persons, we looked at the primary infections caused by drug-resistant HIV-1 over time. Furthermore, to study the coverage rate of therapy and therapy failure in relation to the transmission of resistant viruses a mathematical model was developed.

DESIGN

The reverse transcriptase and protease genes of viruses were analysed in newly infected people in the period 1990-1998 in the Amsterdam Cohort Study on HIV infection and AIDS in homosexual men.

METHODS

The mathematical model was based on the coverage of drug regimens selecting zidovudine (ZDV) resistance, the lag time in which resistance is gained or lost, the death rate of people infected with resistant virus, and the replacement of resistance-selecting regimens by more potent treatments that substantially reduce viral load and mortality.

RESULTS

Of 43 individuals with a primary HIV-infection, three (7%) harboured ZDV-resistant viruses. The first of the ZDV-resistant strains was transmitted in 1995, the last two in 1996. The build-up of ZDV resistance was described by the mathematical model indicating that the equilibrium level of resistance due to treatment depends only on the treatment rate and the outflow rate of patients with resistance virus.

CONCLUSIONS

Our model indicates that the frequency of viral resistance in a population is determined largely by the number of individuals on insufficient or failing therapy and is influenced only modestly by secondary transmission of ZDV-resistant strains.

A comparative trial of zidovudine administered every four versus every twelve hours for the treatment of advanced HIV disease

Zidovudine is approved for administration in doses given every 4 hours. Less frequent dosing has been used in many clinical trials, but the toxicity and efficacy of such regimens have not been formally compared with the approved regimen. In this multicenter, randomized, double-blind, controlled trial, the safety, tolerance and efficacy of 600 mg of zidovudine given daily in two or six divided doses were compared. Three hundred and twenty patients with a CD4 lymphocyte count < 250 cells/mm3 (mean, 104 cells/mm3) or a prior AIDS-defining illness were treated with zidovudine 100 mg every 4 hours (regimen A) or 300 mg every 12 hours (regimen B). Eighty-eight patients (56%) and 94 patients (58%), assigned to regimens A and B, respectively, completed the planned 48 weeks of treatment. Serious anemia (hemoglobin < or = 7.5 g/dl) occurred in 13% and 7% of patients treated with regimens A and B, respectively (difference, 6%, 95% confidence interval [CI], 2, 12%; p = .13). The mean duration of treatment and the frequency of neutropenia and symptomatic complaints including nausea and headache were similar in the two treatment groups. The number of patients experiencing a new opportunistic infection (18% versus 20% for regimens A and B, respectively), and the number of deaths (five in each group) did not differ significantly between groups. The effect of treatment on CD4 lymphocyte counts and HIV p24 antigenemia also was similar for both regimens. Zidovudine given at the more convenient dose of 300 mg twice daily has similar safety, and tolerance and appears to have similar efficacy to the currently approved regimen. Use of this regimen should help simplify the treatment of HIV disease.

Host-parasite dynamics and outgrowth of virus containing a single K70R amino acid change in reverse transcriptase are responsible for the loss of human immunodeficiency virus type 1 RNA load suppression by zidovudine

The association between human immunodeficiency virus type I (HIV-1) RNA load changes and the emergence of resistant virus variants was investigated in 24 HIV-1-infected asymptomatic persons during 2 years of treatment with zidovudine by sequentially measuring serum HIV-1 RNA load and the relative amounts of HIV-1 RNA containing mutations at reverse transcriptase (RT) codons 70 (K-->R), 41 (M-->L), and 215 (T-->Y/F). A mean maximum decline in RNA load occurred during the first month, followed by a resurgence between 1 and 3 months, which appeared independent of drug-resistance. Mathematical modeling suggests that this resurgence is caused by host-parasite dynamics, and thus reflects infection of the transiently increased numbers of CD4+ lymphocytes. Between 3 and 6 months of treatment, the RNA load returned to baseline values, which was associated with the emergence of virus containing a single lysine to arginine amino acid change at RT codon 70, only conferring an 8-fold reduction in susceptibility. Despite the relative loss of RNA load suppression, selection toward mutations at RT codons 215 and 41 continued. Identical patterns were observed in the mathematical model. While host-parasite dynamics and outgrowth of low-level resistant virus thus appear responsible for the loss of HIV-1 RNA load suppression, zidovudine continues to select for alternative mutations, conferring increasing levels of resistance.

Efficacy of AZT therapy in reducing p24 antigen burden in a modified SCID mouse model of HIV infection

A modified severe combined immunodeficient (SCID) mouse model of HIV infection which utilized multiple reconstitutions with human lymphocytes and a large inoculum of HIV was investigated. This mouse model yielded splenic HIV p24 antigen concentrations detectable by standard clinical means. The concentration of p24 exceeded 600 pg/g of spleen through 4 weeks postinfection. A 1-week course of AZT therapy initiated after infection produced a dose responsive reduction in p24 antigen burden. Up to a 95% reduction in p24 antigen burden was observed following AZT therapy at 50 mg/kg/day, while AZT therapy at 5 and 0.5 mg/kg/day produced 52 and 18% reductions. In vitro and pharmacokinetic evaluations correlated potency and tissue concentrations of AZT with treatment efficacy. Active HIV replication in the SCID mice was suggested by both the recovery of viable virus from SCID spleens, and by the efficacy of a brief course of AZT therapy. This SCID mouse model of HIV infection was more quantitative than previous mouse models that utilize PCR-based techniques for detection of HIV. The high HIV burden in this SCID mouse model allowed reductions in p24 concentration to be monitored in response to AZT therapy. A dose response to AZT therapy was demonstrated, even when the first dose was administered after infection. This result suggests greater sensitivity than in previous models in which pretreatment with AZT was required to produce a protective response. This SCID mouse model may be useful for determining efficacy of experimental HIV therapeutics prior to clinical use. An effective animal model could result in a reduction in cost and more rapid development of effective HIV therapeutics.

Distinct changes in HIV type 1 RNA versus p24 antigen levels in serum during short-term zidovudine therapy in asymptomatic individuals with and without progression to AIDS

Serum HIV-1 RNA and p24 antigen levels were examined in 28 seropositive asymptomatic individuals participating in a trial on the efficacy of zidovudine. Sixteen individuals remained asymptomatic until 4 years after the onset of the trial, whereas 12 individuals were diagnosed with an AIDS-defining event. The serum HIV-1 RNA load and p24 antigen levels were determined before the onset of therapy and during the first 8 weeks of therapy to establish whether the patterns of change were predictive of clinical outcome. Among the 28 participants 43% had measurable pretreatment concentrations of p24 antigen. Initiation of zidovudine therapy was followed by a similar decline of p24 antigen levels in nonprogressors as well as progressors and, therefore, these groups could not be distinguished on the basis of this parameter. HIV-1 RNA was detected in the pretreatment samples of 82% of the individuals and could be detected in p24 antigen-positive as well as p24 antigen-negative individuals. Similar changes in HIV-1 RNA load during zidovudine therapy were observed in p24 antigen-positive and -negative individuals. Analysis of the HIV-1 RNA response according to clinical outcome demonstrated that HIV-1 RNA copy numbers had declined significantly after 4 weeks of therapy in both nonprogressors and progressors, but the decline in RNA load was much stronger in the nonprogressors. Our data show that the HIV-1 RNA load in serum can be used to monitor the response to antiviral therapy in p24 antigen-positive as well as -negative individuals. Posttreatment changes in p24 antigen levels are not indicative for clinical outcome, whereas RNA copy numbers are.(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebrospinal fluid human immunodeficiency virus type 1 (HIV-1) p24 antigen levels in HIV-1-related dementia

Human immunodeficiency virus type 1 (HIV-1) p24 antigen, a putative marker of virus load, was assayed in 79 blood and 83 cerebrospinal fluid (CSF) samples from 90 HIV-1-seropositive individuals with or without dementia. Twenty-eight subjects had no evidence of neuropsychological impairment, 17 had mild impairment without objective evidence of dementia, and 45 were demented. HIV-1 p24 antigen was detected more frequently in CSF samples from demented (19/40) than normal (1/26) or mildly impaired (1/17) subjects and in 67% of individuals with significant dementia (MSK stages 2-4). p24 Antigen was detected less frequently in CSF from demented subjects on antiretroviral drugs than untreated demented individuals. Overall, the sensitivity of the antigen capture assay in CSF among demented individuals was 47.5%; the specificity, 95.0%; positive predictive value, 90.4%; negative predictive value, 66.1%; and the efficiency, 72.2%. A direct relationship was also noted between the degree of cognitive impairment and blood p24 antigen detection frequency and antigen concentration. CD4+ blood lymphocyte counts were lower for demented individuals, and HIV-1 p24 antigen was detected more frequently and p24 antigen concentration was higher in blood and CSF from individuals with low CD4+ blood lymphocyte counts. beta 2-Microglobulin levels were higher in CSF from demented subjects and correlated directly with CSF p24 antigen concentration. However, in contrast to CD4+ blood lymphocyte counts and beta 2-microglobulin levels, only p24 antigen concentration correlated with dementia severity. Therefore, p24 antigen can be a useful marker for dementia related to HIV-1 infection.

AZT-induction of micronuclei in human lymphocyte subpopulations

Micronucleus (MN) induction by azidothymidine (AZT) in B and T lymphocytes was analyzed by a recently developed MAC (morphology-antibody-chromosome) method which allows the immunologic identification of different cell lineages. An increased frequency of MN in AZT-treated cultures compared with controls was observed. CD4 cells were found to be more sensitive to AZT damage. AZT-treated cultures showed a significant decrease in the proportion of CD4 interphasic cells. Furthermore, higher MN frequencies in isolated lymphocytes than in whole blood in both control and AZT-treated cultures were observed.

Randomized double-blind, placebo-controlled trial of twice-daily zidovudine in asymptomatic haemophiliacs infected with the human immunodeficiency virus type 1. European-Australian Haemophilia Collaborative Study Group

In this double-blind, placebo-controlled trial of HIV-infected asymptomatic haemophiliacs, the efficacy of 2-year zidovudine therapy (1000 mg daily in two divided doses) in preventing progress of HIV infection was prospectively evaluated. Drug tolerance was also studied. 143 haemophiliacs from five European countries and Australia with p24 antigenaemia and/or CD4 cell counts of 0.1-0.4 x 10(9)/l were enrolled. The main measures of outcome were progression to AIDS, CDC group IV disease, symptomatic HIV-related disease, and a decrease in CD4+ T-lymphocyte count to fewer than 0.2 x 10(9)/l. There were no significant treatment differences in the proportion of patients progressing to AIDS, CDC group IV or symptomatic disease. Analysis of time to CD4+ counts less than 0.2 x 10(9)/l showed a non-significant trend in favour of zidovudine. Haemoglobin concentrations were less than 8 g/dl in 4% of zidovudine recipients; neutropenia was less than 0.75 x 10(9) cells/l in 5% of zidovudine recipients; alanine aminotransferase levels were greater than 10 times the upper normal limit in 3% of zidovudine recipients, but also in 4% of placebo recipients. Hence there was a very low prevalence of side-effects in haemophiliacs, despite the use of a higher zidovudine dosage than is currently widely used.

Improved detection of HIV p24 antigen in serum after acid pretreatment

HIV-1 p24 antigen was detected in 554 sera (509 from HIV-1 seropositive individuals and 45 sera from seronegative controls) using a conventional method with acid pretreatment of the sample in order to separate the p24 antigen/anti-p24 antibody immune complexes. In asymptomatic individuals there was a substantial increase in antigen detection (48.2% vs 8.4%). Similar results were also observed in ARC (59.1% vs 12.2%) and AIDS patients (85.7% vs 37.1%). It can be concluded that the acid treatment improves the sensitivity of conventional techniques to detect HIV-1 p24 antigen.

A survey of zidovudine use in pregnant women with human immunodeficiency virus infection

BACKGROUND AND METHODS

The expanding indications for zidovudine treatment make it important to elucidate the safety and toxicity of this drug for pregnant women and their fetuses. We asked pediatricians and obstetricians at the AIDS (acquired immunodeficiency syndrome) Clinical Trials Units to report information about pregnant women infected with the human immunodeficiency virus (HIV) who were continuing their pregnancies and had received, or were receiving, zidovudine during gestation.

RESULTS

Reports of 43 women were received from 17 institutions. Doses of zidovudine ranged from 300 to 1200 mg per day, and 24 women took the drug for at least two trimesters. There were two reported instances of maternal toxicity (one gastrointestinal and one hematologic). No teratogenic abnormalities occurred in the 12 infants with first-trimester exposure to zidovudine. All the infants, including two sets of twins, were born alive. The 38 singleton infants born at term for whom birth weights were reported had a mean birth weight of 3287 +/- 670 g; two cases of intrauterine growth retardation were reported among the infants delivered at term. Hemoglobin values, which were available for 31 newborns, ranged from 7.0 to 12.4 mmol per liter (11.2 to 20 g per deciliter); 3 of the 7 newborns with hemoglobin values of less than 8.4 mmol per liter (13.5 g per deciliter) were born prematurely.

CONCLUSIONS

Zidovudine was well tolerated by the pregnant women and was apparently not associated with malformations in the newborns, premature birth, or fetal distress. No pattern of hematologic toxicity was observed in the newborns, but the anemia and growth retardation seen in a minority of the infants could, in part, have resulted from their mothers' treatment with zidovudine.

An improved method for monitoring efficacy of anti-retroviral therapy in HIV-infected individuals: a highly sensitive HIV p24 antigen assay

Circulating human immunodeficiency virus (HIV) p24 antigen levels were measured by a highly sensitive HIV p24 antigen-capture enzyme-linked immunosorbent assay (ELISA) in patients with acquired immunodeficiency syndrome (AIDS) and AIDS-related complex (ARC) otherwise negative for HIV p24 antigen measured by a commercial antigen-capture ELISA. The assays were performed at baseline and at several intervals during treatment with either zidovudine (ZDV) or dideoxyinosine (ddl). To further enhance the rate of antigen detection, serum was pretreated with hydrochloric acid to denature antibody in immune complexes. Utilizing this assay system, we monitored these patients for drug efficacy. HIV p24 antigen levels obtained by using this sensitive assay decreased in 3 of 8 patients receiving ZDV during 8 weeks of ZDV treatment. Similarly, ddl administration was associated with a decrease of HIV p24 antigen levels in 3 of 5 patients. Thus, the use of the highly sensitive HIV p24 antigen assay permitted the monitoring of surrogate HIV p24 antigen as a measure of efficacy of anti-retroviral therapy in all of these patients who were otherwise HIV p24 antigen-negative at the onset of anti-retroviral therapy.

Molecular specificity of two commercial enzyme linked immunosorbent assays for human immunodeficiency virus antigens

Only "fair" agreement has been shown between the Abbott and DuPont enzyme linked immunosorbent assays when used for the detection of human immunodeficiency virus (HIV) antigen in serum samples from asymptomatic HIV antibody positive homosexual men. To investigate the discrepancies between the two ELISA results, further experiments were performed. The rabbit detector antibody solutions of both tests were western blotted and showed that the DuPont test was specific for p24; the Abbott detector antibody had bands for p18, p41-43, gp120 as well as p24. By using dilutions of a known amount of HIV antigen, the Abbott test could detect 20 pg/ml p24; the DuPont test could detect 30 pg/ml p24. The DuPont test was also more sensitive than the Abbott test at detecting a synthetic 104mer peptide of p24. Within the 104mer sequence two regions (294-318, 334-348 amino acids) inhibited the binding of the DuPont detector antibody, but no blocking was observed with the Abbott antibody. Although the Abbott test was slightly more sensitive at detecting HIV protein than the DuPont test, the major difference between the tests was in the molecular specificity, in that the Abbott test detected proteins other than p24. This may not be important for detecting antigen in cell culture, but it may affect the detection of antigenaemia in patients' sera.

Serum beta 2-microglobulin levels in asymptomatic HIV-1-infected subjects during long-term zidovudine treatment

beta 2-microglobulin levels were determined in the serum of 18 initially asymptomatic HIV-1 p24 antigenaemic subjects who were treated with zidovudine (+/- acyclovir) and who were followed for 2 1/2 years. The median serum beta 2-microglobulin level at week 0 was 2.5 mg/l and decreased to 2.3 mg/l after 12 weeks of treatment (p = 0.001). A correlation was found between individual changes in serum beta 2-microglobulin levels and individual changes in serum p24 antigen levels during the first 48 weeks of treatment (p less than 0.05). Six out of 18 subjects progressed to AIDS after 60-126 weeks of treatment. In this group during a period of more than one year before disease progression median serum beta 2-microglobulin levels increased from 2.5 mg/l to 3.3 mg/l (p = 0.03) and median CD4+ cell counts decreased from 0.3 x 10(9)/l to 0.08 x 10(9)/l (p = 0.03), while in that period the pattern of serum p24 antigen levels was inconsistent. Although the variability in serum beta 2-microglobulin levels appeared to make this marker unsuitable for management decisions in individuals, a decline in beta 2-microglobulin levels was found to parallel a decline in p24 antigen levels during the early phase of zidovudine treatment. Moreover, after prolonged treatment, rising beta 2-microglobulin levels--in contrast to p24 antigen levels--were shown to have predictive value for disease progression.

The effects of twice and four times daily zidovudine on p24 antigenaemia in CDC stage II/III patients

Reduction of HIV p24 antigenaemia by zidovudine was investigated in 34 HIV antibody-positive, asymptomatic patients in a randomised, double-blind, placebo-controlled trial. Zidovudine was shown to lower p24 antigen levels as effectively when administered twice daily as when administered four times daily. Serum levels of p24 antigen varied little over 18 weeks in patients taking placebo.

Pharmacokinetic interaction of antimicrobial agents with levomethadon in drug-addicted AIDS patients

Morphine and its derivatives are metabolized by the liver microsomal enzyme system with a high first-pass effect after oral application. In four of 44 HIV-infected i.v. drug abusers who participated in a levomethadon maintenance program, we observed sustained symptoms of under-dosage and loss of effect of there to fore well-tolerated substitution therapy during rifampin treatment or therapy with zidovudine or fucidic acid. As a pharmacological model substance for cytochrome p 450 enzymes, measurement of antipyrine in serum by high pressure liquid chromatography revealed induction of cytochrome p 450 isoenzymes. The half-life of antipyrine decreased (patient 1 from 11.3 to 8.4 h and patient 2 from 10.7 to 7.6 h after rifampin, patient 3 from 12.2 to 8.6 h after fucidic acid, and patient 4 from 10.6 to 8.6 h after zidovudine). In i.v. drug abusers on levomethadon maintenance programs, adjustment of the levomethadon dosage may be necessary when specific therapy for HIV infection and associated diseases requires the use of drugs known to be potent inducers of the liver microsomal enzyme system.

Monocytotropic human immunodeficiency virus type 1 (HIV-1) variants detectable in all stages of HIV-1 infection lack T-cell line tropism and syncytium-inducing ability in primary T-cell culture

We previously demonstrated a correlation between the presence of syncytium-inducing (SI) human immunodeficiency virus type 1 (HIV-1) variants showing tropism for cell line H9 and the occurrence of rapid CD4 cell decline and progression to AIDS. In contrast, in stable asymptomatic individuals, we detected only isolates with low replication rates that were non-syncytium-inducing (NSI) and nontropic for the H9 cell line. Here, we investigated the monocytotropism of established HIV-1 isolates with a panel of isolates and with biological HIV-1 clones with distinct phenotypes. Moreover, the prevalence and biological phenotypes of monocytotropic HIV-1 variants in the course of HIV-1 infection were analyzed in comparative primary isolation studies on peripheral blood lymphocytes (PBL) and monocyte-derived macrophages (MDM). In cell-free infection studies with MDM from eight blood donors, 13 of 17 NSI isolates but only 4 of 14 SI isolates were able to infect MDM. NSI isolates also infected significantly more different donors than SI variants (median, 3 of 8 versus 0 of 8). This enhanced monocytotropism of NSI isolates was confirmed in experiments with biological HIV-1 clones with distinct phenotypes recovered from the same donor. To investigate the prevalence and biological phenotypes of monocytotropic variants in different stages of HIV-1 infection, sequential isolates from peripheral blood mononuclear cell samples from nine asymptomatic individuals, five of whom progressed to AIDS and seven of whom had a known time of seroconversion, were recovered by cocultivation with both PBL and MDM. Monocytotropic variants were obtained from 37 of 42 time points. All monocytotropic variants were NSI in PBL culture and non-T-cell-line tropic, even when SI, T-cell-line-tropic HIV-1 variants could be recovered from the same patient sample by cocultivation with PBL. We conclude that monocytotropic HIV-1 variants mostly have an NSI phenotype in PBL and, in contrast to SI variants, are present at all stages of HIV-1 infection. These results suggest an important role for monocytotropic variants in the persistence of HIV-1 infection.

A pilot study of low-dose zidovudine in human immunodeficiency virus infection

BACKGROUND

Zidovudine delays the progression of human immunodeficiency virus (HIV) infection but is associated with hematologic toxicity at high doses. Regimens are needed that preserve or enhance efficacy and reduce toxicity. Acyclovir has been reported to potentiate the effect of zidovudine on HIV in vitro.

METHODS

We conducted a Phase II open-label, dose-escalating trial to evaluate the clinical and antiviral effects of zidovudine at low (300 mg daily, 28 subjects), medium (600 mg, 24 subjects), and high (1500 mg, 15 subjects) doses, either with or without acyclovir (4.8 g) by random assignment. The subjects had the acquired immunodeficiency syndrome (AIDS)-related complex, but not AIDS. All of them had either HIV p24 antigenemia or plasma viremia and CD4-lymphocyte counts of 200 to 500 per cubic millimeter when they began treatment.

RESULTS

Performance scores and fatigue improved the most in the low- and medium-dose zidovudine groups (both P less than or equal to 0.025). Those assigned to low-dose zidovudine gained the most weight and had the greatest improvement in the mean CD4-lymphocyte count (from 321 per cubic millimeter at base line to 412 per cubic millimeter after 12 weeks, P = 0.01). The proportion of subjects in whom HIV antigenemia resolved, the decrease in the level of antigenemia, and the reduction in the plasma virus titers were similar at all three doses. Subjects assigned to receive the low or medium dose who subsequently crossed over to the 1500-mg dose (n = 19) did not have an increase in CD4-cell counts or a decline in levels of HIV antigen, but they did have dose-related toxicity. The addition of acyclovir to zidovudine was well tolerated, but it did not enhance any of zidovudine's antiretroviral effects.

CONCLUSIONS

In this pilot study a very low dose of zidovudine (300 mg) had clinical and virologic effects similar to those of higher daily doses (600 and 1500 mg). The minimal effective dose of zidovudine for the treatment of HIV infection has yet to be determined, and further studies of very low daily doses are warranted.

Zidovudine sensitivity of human immunodeficiency viruses from high-risk, symptom-free individuals during therapy

Human immunodeficiency type 1 isolates from 18 initially symptom-free men who were treated with zidovudine for 2 years were investigated for drug sensitivity. At the start all the men had persistent core antigenaemia; the acquired immunodeficiency syndrome developed in 6 during the study. The polymerase chain reaction was used to detect mutations at residue 215 of reverse transcriptase, a mutation associated with reduced drug sensitivity. After 2 years 16/18 isolates were mutant. However, after about 6 months of treatment the mutation was detected in only 7 isolates, 4 from individuals who subsequently had AIDS. Limited direct virus sensitivity data correlated with the genetic data. The rate of appearance of the 215 mutation seemed to correlate with CD4 counts and viral virulence.

[HIV-1 antigenemia and T-cell activation in HIV-1 infected patients]

In order to study a supposed association between T-cell activation in vivo and HIV-1-antigenemia in HIV-1-infected patients, the detection of p24-antigen in sera was correlated to serum levels of beta-2-microglobulin and C1q-binding immune complexes. Anti-p24-antibodies and the urinary excretion of neopterin were also analysed. In 24 of 80 patients (30%) p24-antigen could be detected, and in 15 of 59 (25.4%) there was a loss of anti-p24-antibodies. Tests revealed elevated serum levels of beta-2-microglobulin in 58 of 80 patients (72.5%), elevated levels of C1q-binding immune complexes in 15 of 66 (22.7%), and increased excretion of neopterin in 52 of 60 (86.7%). Detection of p24-antigen, loss of anti-p24-antibodies, serum levels of beta-2-microglobulin, and urinary excretion of neopterin were significantly correlated to advanced stages of HIV-1 infection. Patients with p24-antigen in the serum showed significantly more frequently elevated serum levels of beta-2-microglobulin and no significant association with increased urinary excretion of neopterin. Because of the high proportion of patients with elevated serum levels of beta-2-microglobulin and increased excretion of urinary neopterin in the absence of detectable p24-antigen in serum, we could not correlate HIV-1-antigenemia to T-cell activation in vivo.

Alpha interferon (2b) in combination with zidovudine for the treatment of presymptomatic feline leukemia virus-induced immunodeficiency syndrome

The therapeutic efficacies of human recombinant alpha interferon (IFN-alpha), IFN-alpha plus zidovudine (AZT), and AZT alone were evaluated in presymptomatic cats with established feline leukemia virus (FeLV)-acquired immunodeficiency syndrome (FAIDS) infection and high levels of persistent antigenemia. Subcutaneous injection of 1.6 x 10(6) U of human recombinant IFN-alpha 2b per kg delivered peak concentrations in plasma of 3,600 U/ml at 2 h postadministration with a half-life of elimination of 2.9 h. This dosage of IFN-alpha could be delivered to cats for up to 12 weeks without significant clinical toxicity. Oral administration of AZT (20 mg/kg three times daily) resulted in peak concentrations in plasma of 3 micrograms/ml at 2 h with a half-life of elimination of approximately 1.60 h. Treatment of FeLV-FAIDS-infected cats with IFN-alpha, either alone or in combination with orally administered AZT, resulted in significant decreases in circulating p27 core antigen beginning 2 weeks after the initiation of therapy. AZT alone had no effect on circulating virus antigen. Depending upon whether high (1.6 x 10(6) U/kg)- or low (1.6 x 10(4) to 1.6 x 10(5) U/kg)-dosage IFN-alpha was used, cats became refractory to therapy 3 or 7 weeks after the beginning of treatment. At these times, IFN-alpha-treated animals developed antibodies to IFN-alpha that were neutralizing, specific for human recombinant IFN-alpha, and dose dependent in magnitude. The results of this study indicate that human recombinant IFN-alpha is effective in reducing circulating virus antigenic load in cats persistently infected with FeLV-FAIDS. However, the continued efficacy of IFN-alpha therapy appeared to be limited by the formation of cytokine-specific neutralizing antibodies.

Needlestick injuries among resident physicians

OBJECTIVE

To assess the frequency and causes of needlestick injuries in medical and surgical housestaff.

DESIGN

A retrospective survey.

SETTING

Urban university teaching hospital.

PARTICIPANTS

386 housestaff; 221 responded.

INTERVENTION

Survey questionnaire.

MAIN RESULTS

1) Frequency of needlestick: Of 221 respondents, 57 (26%) reported never having had a needlestick, while 164 (74%) reported at least one needlestick injury with a suture or hollow-bore needle. The average frequencies were 0.63 per resident-year among 149 non-surgical residents and 3.8 per resident-year among 72 surgical residents. Among residents in internal medicine, 12 of 78 needlestick injuries (15%) sustained were from patients documented to be HIV-positive. 2) Causes of needlestick: The causes of injury were assessed in detail in a sample of the 157 most recent needlestick injuries. Suturing was the cause in 35 of 61 (57%) surgical residents, while recapping needles was the cause in 36 of 96 (38%) non-surgical residents. Inexperience was not the cause of injury; in 94% of cases the residents felt comfortable performing the procedure, and in 74% of cases the residents had performed the procedure more than 50 times before. 3) Reporting of injury: Only 30 (19%) of 157 injuries were reported to the personnel health service, thus compromising documentation for potential workmen's compensation.

CONCLUSIONS

Needlestick injuries are common among medical and surgical housestaff. Efforts should be made to prevent needlestick injuries and to report those that occur.

Antiviral therapy against HIV infection

The replication of human immunodeficiency virus (HIV) can be suppressed in vivo by drugs chosen on the basis of their selective in vitro antiviral activity. Such suppression can confer prolonged survival and improved quality of life in patients with already established HIV infection. The clinical benefits indicate that targeted therapy for acquired immunodeficiency syndrome based on the emerging knowledge of replicative cycle of HIV is an attainable goal.

Safety and tolerance of dideoxycytidine as a single agent. Results of early-phase studies in patients with acquired immunodeficiency syndrome (AIDS) or advanced AIDS-related complex. Study Group of the AIDS Clinical Trials Group of the National Institute of Allergy and Infectious Diseases

Phase I and II clinical studies have been conducted to test the safety and potential activity of the reverse transcriptase inhibitor, dideoxycytidine (ddC), in treating human immunodeficiency virus-1-infected patients. Although ddC appears to be active in combating viral infection, as judged by its ability to decrease human immunodeficiency virus-1 p24 antigen titers and increase the number of CD4+ lymphocytes, it is also capable of causing severe peripheral neuropathy in a dose-dependent manner. The studies discussed here indicate that low-dose ddC treatment regimens substantially reduce the toxic side effects of this drug, and yet retain the ability to affect p24 antigen and CD4+ lymphocyte levels. These studies also define the window of therapeutic usefulness for ddC, and suggest that both safety and activity can be maintained during long-term, low-dose use of ddC.

Blind comparison of Abbott and Dupont HIV antigen ELISA tests for detecting antigenaemia in asymptomatic human immunodeficiency virus antibody positive homosexual men

Three hundred and ninety eight serum samples from 270 human immunodeficiency virus (HIV) antibody positive asymptomatic homosexual men were tested in the Abbott and Dupont HIV antigen ELISA tests. In the Abbott test 62 (16%) of the sera were positive, according to the manufacturer's instructions, compared with 55 (14%) in the Dupont test. Twenty six sera were positive with the Abbott test but negative with the Dupont test and 19 sera were positive only by the Dupont test. Only 36 (9%) of the sera were positive in both tests. The Abbott confirmatory neutralisation test gave excellent agreement with the initial Abbott HIV antigen ELISA test; the Dupont confirmatory test was only in agreement with the initial positive Dupont antigen ELISA test in one third of the sera tested. Although the overall sensitivity of each of the two commercial assays tested was similar, the Abbott method may be preferable for clinical purposes if confirmation of an initial ELISA positive test result by neutralisation assay is required.

Long-term zidovudine treatment of asymptomatic HIV-1-infected subjects

Eighteen asymptomatic men with persistent human immunodeficiency virus type 1 (HIV-1) p24 antigenemia were treated with zidovudine 250-500 mg (+/- acyclovir 800 mg) 6-hourly for 4-12 weeks, and thereafter with zidovudine 500 mg (+/- acyclovir 1600 mg) 12-hourly for 92 weeks. Six additional HIV-1 p24 antigenemic subjects were treated with zidovudine 500 mg 12-hourly for 76 weeks. Disease progression occurred in 4 subjects, despite sustained reduction of serum HIV-1 p24 antigen levels: Pneumocystis carinii pneumonia was diagnosed after 60, 80, 90 and 93 weeks, respectively. The median CD4+ cell count of these 4 men at study entry was 0.2 x 10(9)/l, and it declined to 0.07 x 10(9)/l at the moment AIDS was diagnosed. In 20 subjects no disease progression occurred. The median CD4+ cell count of these 20 men at study entry was 0.4 x 10(9)/l and it was 0.45 x 10(9)/l at the end of the study period. Median serum HIV-1 p24 antigen levels at the end of the study period were 42% lower than at study entry in these 20 subjects. In 5/20 men, an initial decline was followed by a rise in antigen levels to above pretreatment value. Treatment with zidovudine was well tolerated. Anemia caused symptoms in 3/24 men, but prolonged leucopenia or neutropenia did not occur. None developed clinical or convincing biochemical evidence of zidovudine-associated myopathy.

Phase I study of low-dose zidovudine and acyclovir in asymptomatic human immunodeficiency virus seropositive individuals

PURPOSE

The combination of zidovudine and acyclovir has shown in vitro antiretroviral activity and led to short-term improvement in patients with symptomatic human immunodeficiency disease (HIV) disease. We performed a phase I study of zidovudine (500 mg/day) plus acyclovir (2 or 4 g/day) in asymptomatic HIV-seropositive men to investigate pharmacokinetics, safety, tolerance, and immunologic effects of the combination.

SUBJECTS AND METHODS

Fifty HIV-seropositive homosexual or bisexual men from the San Francisco City Clinic Cohort Study were recruited for the study; of these, 20 met the eligibility criteria. Treatment with zidovudine and acyclovir was open label. Pharmacokinetic, virologic, immunologic, and clinical data were collected periodically over a 24-week period.

RESULTS

Pharmacokinetic analysis showed no drug interaction. The combination was generally well tolerated, and hematologic parameters remained stable through 24 weeks. There were no significant changes in total lymphocytes, T4 lymphocytes, overall skin test reactivity, or ability to culture virus from peripheral blood.

CONCLUSION

This combination of agents is safe in this population for at least six months. Conclusions about long-term tolerance and efficacy await the results of larger trials with longer follow-up.

Declining incidence of AIDS dementia complex after introduction of zidovudine treatment

OBJECTIVE

To assess the incidence of the AIDS dementia complex and the presence of HIV I p24 antigen in cerebrospinal fluid in relation to zidovudine treatment.

DESIGN

Retrospective study of a consecutive series of patients with AIDS from 1982 to 1988.

SETTING

An academic centre for AIDS.

PATIENTS

196 Patients with AIDS and neurological symptoms examined from 1982 to 1988.

INTERVENTIONS

Zidovudine treatment, which was introduced to The Netherlands on 1 May 1987 for patients with severe symptoms of HIV infection (Centers for Disease Control groups IVA, B, C, and D).

MAIN OUTCOME MEASURES

Diagnosis of AIDS dementia complex and presence of HIV I p24 antigen in cerebrospinal fluid.

RESULTS

The AIDS dementia complex was diagnosed in 40 of the 196 (20%) patients with AIDS. Thirty eight of 107 patients with AIDS (36%) not taking zidovudine developed the AIDS dementia complex compared with two of the 89 (2%) taking the drug (p less than 0.00001). The incidence of the AIDS dementia complex increased to 53% in the first half of 1987, after the introduction of zidovudine in May 1987, decreasing to 10% in the second half of 1987 and to 3% in 1988. Dementia was diagnosed before definition of the AIDS dementia complex (1986) according to DSM-III criteria and there was good agreement between diagnosis before and after 1986. Sixteen of 61 samples of cerebrospinal fluid (26%) from patients with AIDS (10 with the AIDS dementia complex) not taking zidovudine were positive for HIV I p24 antigen, whereas none of 37 cerebrospinal fluid samples from patients with AIDS (two with the AIDS dementia complex) taking zidovudine were positive.

CONCLUSIONS

The incidence of AIDS dementia complex in patients with AIDS declined after the introduction of systematic treatment with zidovudine; the AIDS dementia complex might be prevented by inhibiting viral replication in the central nervous system.

Quantitative western immunoblotting analysis in survey of human immunodeficiency virus-seropositive patients

Identifying criteria for the early prediction of progression to acquired immunodeficiency syndrome in asymptomatic human immunodeficiency virus-seropositive patients have become necessary in order to widen the indications for antiviral treatment by azidothymidine and to increase its efficiency. With this aim in mind, we studied a cohort of seropositive homosexual men in the southwest region of France (Midi-Pyrénées). Of all the factors analyzed, the decline in p24 antibodies, assayed by second-generation enzyme-linked immunosorbent assay, was found to be the most reliable. On the basis of the work of Blomberg and Schmidt, we developed a quantitative approach to Western blotting (immunoblotting) for use in the follow-up of human immunodeficiency virus-infected patients. Our technique of quantitative Western blotting is unique because it uses a densitometric reading which, through a computerized system, gives a curve allowing the exact quantification of each stained Western blotting band. The results are expressed as integrals. This technique confirms the decrease in p24 and p17 antibodies as the criterion giving the earliest prediction of the progression to acquired immunodeficiency syndrome.

Antigen detection for human immunodeficiency virus

The recent development of enzyme immunoassay procedures for the direct determination of human immunodeficiency virus (HIV) antigens has been of significant benefit in both clinical and research applications. The historical development of HIV antigen assays as well as their current and future applications for use in the clinical microbiology laboratory are reviewed. A detailed description of selected commercially available assays is presented, and a comparison is made of various parameters, including sensitivity, specificity, and cost. The use of the HIV antigen assay as an alternative to the reverse transcriptase assay in virus culture applications is also discussed. In addition, the diagnostic and prognostic utility of the HIV antigen assay is considered for various patient groups, including neonatal, high-risk asymptomatic, seronegative, and seropositive patient populations. The use of the HIV antigen assay as an adjunct to anti-HIV antibody testing, as well as its utility in assessing the therapeutic efficacy of antiviral drug therapy, is discussed. The biology of HIV antigen expression and modulation of anti-HIV antibody titers during infection are also discussed in terms of two possible models.

Evaluation of three enzyme immunoassays for HIV-1 antigen detection

Three enzyme immunoassay (EIA) methods for the detection of human immunodeficiency virus (HIV-1) were evaluated. Serum or plasma samples from 22 individuals seropositive for HIV-1 antibodies were tested with the Abbott, Coulter, and DuPont kits for presence of HIV-1 p24 antigen. Another 12 samples were tested with two kits only. Discordant results were obtained with 9 of 34 (26%) HIV-1-antibody-positive patient samples tested. Most of these discrepancies were found in samples containing less than 30 pg/ml of HIV-1 p24 core antigen. A sampling of sera from normal blood donors and patients with infectious or autoimmune diseases revealed a low level of false positive reactions, especially with sera containing antinuclear antibodies or rheumatoid factor. Noteworthy is the frequency of false positive reactions seen with the DuPont EIA for HIV-1 p24 antigen. 18/111 sera (16.2%) containing auto-antibodies tested positively with the DuPont HIV-1 p24 antigen EIA. The nonspecific nature of the test reactivity for 9/10 of these samples was confirmed using an HIV-1 p24 antigen inhibition assay. These findings are discussed in light of the need for HIV-1 antigen detection in the clinical laboratory and of other methods for HIV-1 detection: the polymerase chain reaction and measurements of reverse transcriptase activity.

A randomized, placebo-controlled trial of oral acyclovir for the prevention of cytomegalovirus disease in recipients of renal allografts

Cytomegalovirus is a major viral pathogen in patients who undergo renal transplantation, and cytomegalovirus disease is difficult to treat. We therefore conducted a randomized, placebo-controlled, double-blind trial of acyclovir for the prevention of cytomegalovirus disease in recipients of renal allografts from cadavers. Acyclovir was given orally in doses of 800 to 3200 mg per day, according to the patients' estimated level of renal function. Patients took the first dose of either acyclovir or placebo six hours before transplantation and continued to take the assigned medication for 12 weeks. Of 118 patients enrolled in the study, 104 completed at least 30 days on the study medication and were included in our analysis of the results. During the first year after transplantation, 4 of 53 patients (7.5 percent) in the acyclovir group had symptomatic cytomegalovirus disease, as compared with 15 of 51 (29 percent) in the placebo group (P = 0.002). There was a single case of cytomegalovirus pneumonia in the acyclovir group, as compared with nine in the placebo group. The greatest prophylactic benefit of acyclovir was observed among seronegative patients who had received a kidney from a seropositive donor; only one of six such patients in the acyclovir group had cytomegalovirus disease, as compared with all seven in the placebo group. Acyclovir decreased the incidence of documented cytomegalovirus infection (with or without symptomatic disease) to 36 percent from 61 percent among the patients who received the placebo (P = 0.011). Among the patients who received acyclovir, the rates of recovery of virus from the blood and urine were significantly reduced, but the rate of viral shedding from the pharynx was not significantly different from that in the placebo group. There were no differences between the groups in the frequency of adverse events or in the rate of survival of either grafts or patients. We conclude that the oral administration of acyclovir, beginning before the transplantation of a renal allograft from a cadaver, reduces the rate of cytomegalovirus infection and disease without affecting the survival rate of either grafts or patients.

Association of human immunodeficiency virus (HIV) p24 antigenemia with decrease in CD4+ lymphocytes and onset of acquired immunodeficiency syndrome during the early phase of HIV infection

Human immunodeficiency virus (HIV) p24 antigenemia was assessed in a longitudinal study of 52 homosexual men who developed serum antibody to HIV. Antibody seroconversion to HIV as defined by a positive HIV enzyme immunoassay (EIA) confirmed by Western (immuno-) blot was associated with three major patterns of HIV antigenemia. In the first pattern, a transient antigenemia was noted 6 (six subjects) and 12 (one subject) months prior to detection of antibody by HIV EIA and Western blot in 7 (13.5%) of the 52 men. Use of an EIA employing a recombinant envelope protein (ENV9) was able to detect antibody in four of these seven men at the time of this early antigenemia. In the second pattern, HIV p24 antigenemia occurred in 8 (15.4%) of the 52 subjects within the first 12 months after HIV antibody seroconversion. No p24 antigen was detected in the 37 (71.1%) remaining subjects. CD4+ cell numbers were lower in antigen-positive men before and after antibody seroconversion. Development of acquired immunodeficiency syndrome (AIDS) or AIDS-related complex was strongly associated with evidence of persistent p24 antigenemia during the early, postseroconversion period. HIV p24 antigenemia may be of value in determining appropriate cohorts for drug therapy trials for subjects with early-phase HIV infection.

Zidovudine. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy

Zidovudine (azidothymidine) is a thymidine analogue antiretroviral drug active against human immunodeficiency virus (HIV). In acquired immunodeficiency syndrome (AIDS) and AIDS-related complex (ARC) patients, orally and intravenously administered zidovudine is effective in reducing the incidence of opportunistic infections and neoplasms, increasing helper T lymphocyte numbers, and improving survival rates and quality of life. Adverse effects include serious haematological abnormalities and severe headache, abdominal discomfort, nausea, myalgia and insomnia. In addition, neutropenia and other anaemias frequently limit zidovudine therapy and may result in a need for multiple blood transfusions, dose reductions or withdrawal of the drug. However, despite these problems and the lack of information about some aspects of zidovudine use, zidovudine provides a major hope for HIV-infected patients, and it has rapidly become the standard therapy for improving the quality and duration of the lives of AIDS and ARC patients.

Predictive value of the presence of P24 antigen in persons with antibodies to human immunodeficiency virus in Spain

In a prospective study of 37 individuals in Spain who did not have AIDS or AIDS-related complex but were positive for antibody to HIV, 164 sequentially taken serum samples were tested for the presence of the p24 antigen of HIV. Six of the subjects were antigenemic at entry to the study and five of the remaining 31 subjects seroconverted for HIV antigen during follow-up. Six (55%) of the 11 antigenemic patients but none of those without antigenemia developed AIDS. The interval from the time of first detection of HIV antigen to the diagnosis of AIDS varied greatly. The results confirm that individuals with HIV antigenemia run a significantly higher risk of developing AIDS.

Changes in sexual behaviour and the fall in incidence of HIV infection among homosexual men

To investigate the epidemiology and normal course of infection with HIV the prevalence and incidence of the infection were studied among two cohorts of homosexual men in Amsterdam in 1980-7. The cumulative incidence of infection increased from a weighted 2.2% in 1980 to 39.0% in 1987. The estimated yearly incidence of HIV was 3.0% in 1981, rose to 8.8% in 1984, and fell gradually to 0% in 1987. During the study the sexual behaviour of the cohorts was examined. The number of men with whom anopenetrative intercourse was practised fell from a mean of 10.6 to 1.4 for those positive for HIV antibody, whereas the number with whom anoreceptive intercourse was practised fell from a mean of 3.7 to 0.5 for those negative for the antibody. In addition, there was a reduction in the number of cases of hepatitis B and syphilis among men in general. The decline in infection with HIV was assumed to be linked to changes in sexual behaviour. Such changes practised early in the course of the epidemic probably had a strong effect on the number of cases of AIDS among homosexual men in Amsterdam.

Effect of azidothymidine (AZT) on P24 antigen levels in patients with AIDS-related complex and AIDS

Circulating HIV P24 antigen levels at baseline and following AZT therapy were measured in 9 patients with ARC and 11 patients with AIDS. Eight of these patients had no detectable levels of P24. The P24 antigen levels in the remaining 12 patients decreased significantly after AZT treatment. Following discontinuation of AZT treatment in 2 patients, the P24 antigen levels went up. These results clearly demonstrate the efficacy of AZT in reducing P24 antigen levels in circulation.

Markers for progression to acquired immune deficiency syndrome and zidovudine treatment of asymptomatic patients

Eighteen asymptomatic men with persistent human immunodeficiency virus type I (HIV-I) p24 antigenaemia were treated with zidovudine 250-500 mg (+/- acyclovir 800 mg) 6-hourly for 4-12 weeks, and subsequently with zidovudine 500 mg (+/- acyclovir 1600 mg) 12-hourly for 36 weeks. After 24 weeks six additional HIV antigenaemic subjects were entered and treated directly with zidovudine 500 mg 12-hourly. Over the treatment period serum HIV-I p24 (HIV-Ag) levels declined in all 24 subjects; significantly so in 17, and to below cut-off values in five. Mean serum HIV-Ag levels in different treatment groups declined in 68-78%. Initial increases in CD4+ cell counts were not sustained. Over 48 weeks serum HIV-Ag levels rose in three out of five non-treated men with persistent HIV antigenaemia, and they slightly declined in two; the mean serum HIV-Ag level in this group rose 67%. Regression of enlarged lymph nodes was seen in 19 out of 19 of the zidovudine-treated subjects. In the 24 zidovudine-treated subjects no disease progression occurred during follow-up, whereas two out of five non-treated men went on to develop CDC group IV A, and IV C-2 disease, respectively. Adverse reactions to the study drugs were infrequent and mild. Anaemia caused symptoms in two, but serious leucopenia or neutropenia was not observed. An initial positive effect on thrombocyte numbers was not sustained. These data demonstrate that in asymptomatic HIV-infected subjects zidovudine 500 mg 12-hourly is well tolerated and has a persistent inhibitory effect on viral replication.

Effects of zidovudine in 365 consecutive patients with AIDS or AIDS-related complex

Zidovudine (AZT) is of some benefit for selected patients with AIDS-related complex (ARC) or AIDS treated for up to 24 weeks. The activity and toxicity of oral AZT, 200 mg 4-hourly when possible, was evaluated in 365 consecutive patients with ARC (80) or AIDS (285) followed up for a mean of 31 weeks (range 2-52). A transient increase in body weight, Karnofsky index, and CD4 cell count was observed during the first months of therapy. However, by 6 months, these values had returned to their pretreatment levels and several opportunistic infections, malignancies, and deaths occurred. These disappointing results were partly related to the haematological toxicity of the drug, which led to interruption of treatment in many patients. Thus the benefits of AZT are limited to a few months for ARC and AIDS patients. At least for the most severely affected patients, reduced dosage of AZT may increase the therapeutic index.

Human retroviruses

After many unsuccessful years of searching, the first pathogenic human retrovirus, the human T-cell leukaemia lymphoma virus (HTLV-I), was reported as recently as 1980 and since that time has been causally linked to the adult T-cell leukaemia lymphoma syndrome. A second HTLV (HTLV-II) isolated shortly afterwards is less clearly linked to some leukaemic and chronic lymphoid malignancies. The second major family of human retroviruses are the human immunodeficiency viruses (HIV) the first group of isolates (HIV-I) of which cause the acquired deficiency syndrome (AIDS). A second group of these viruses (HIV-II), have recently been identified in West Africa. They appear to be less clearly associated with disease and more similar in molecular structure to the Simian immunodeficiency viruses. AIDS has now become a major global pandemic, and vaccine and therapeutic strategies are urgently being investigated in an effort to control the disease. Unfortunately, current results are not very encouraging. In the meantime, preventative and educational measures are of utmost priority in order to prevent further spread. It is not unlikely that new human retroviruses will be discovered over the next few years.

Effects of passive immunization in patients with the acquired immunodeficiency syndrome-related complex and acquired immunodeficiency syndrome

Infection with the human immunodeficiency virus type 1 (HIV-1) is usually followed by a vigorous immune response that temporarily protects against disease progression. After a variable asymptomatic period, acquired immunodeficiency syndrome (AIDS)-related complex (ARC) and AIDS develop in most infected individuals. We have demonstrated that healthy HIV-1-infected individuals have neutralizing antibodies and a high titer of antiviral antibodies. In contrast, AIDS patients have undetectable levels of neutralizing antibodies, low titers of antiviral antibodies, and, frequently, HIV p24 antigenemia. These observations prompted us to attempt passive immunization in ARC and AIDS patients. Ten consistently viral-antigen-positive patients (mean, greater than 6 months) were treated, resulting in sustained clearance of p24 antigen. Patients either maintained or increased their antiviral antibody titers. The raised titers result from increased antibody synthesis by the recipients. Circulating CD4+ cell counts were unchanged after 2 months. By the third month none of these patients remained in hospital. As this treatment was of minimal toxicity, it merits wider evaluation in ARC and AIDS patients.