Human immunodeficiency virus type 1 infection in homosexual men who remain seronegative for prolonged periods

Course of HIV-I infection in a cohort of homosexual and bisexual men: an 11 year follow up study

OBJECTIVE--To characterise the natural history of sexually transmitted HIV-I infection in homosexual and bisexual men. DESIGN--Cohort study. SETTING--San Francisco municipal sexually transmitted disease clinic. PATIENTS--Cohort included 6705 homosexual and bisexual men originally recruited from 1978 to 1980 for studies of sexually transmitted hepatitis B. This analysis is of 489 cohort members who were either HIV-I seropositive on entry into the cohort (n = 312) or seroconverted during the study period and had less than or equal to 24 months between the dates of their last seronegative and first seropositive specimens (n = 177). A subset of 442 of these men was examined in 1988 or 1989 or had been reported to have developed AIDS. MAIN OUTCOME MEASURES--Development of clinical signs and symptoms of HIV-I infection, including AIDS, AIDS related complex, asymptomatic generalised lymphadenopathy, and no signs or symptoms of infection. MEASUREMENTS AND MAIN RESULTS--Of the 422 men examined in 1988 or 1989 or reported as having AIDS, 341 had been infected from 1977 to 1980; 49% (167) of these men had died of AIDS, 10% (34) were alive with AIDS, 19% (65) had AIDS related complex, 3% (10) had asymptomatic generalised lymphadenopathy, and 19% (34) had no clinical signs or symptoms of HIV-I infection. Cumulative risk of AIDS by duration of HIV-I infection was analysed for all 489 men by the Kaplan-Meier method. Of these 489 men, 226 (46%) had been diagnosed as having AIDS. We estimated that 13% of cohort members will have developed AIDS within five years of seroconversion, 51% within 10 years, and 54% within 11.1 years. CONCLUSION--Our analysis confirming the importance of duration of infection to clinical state and the high risk of AIDS after infection underscores the importance of continuing efforts both to prevent transmission of HIV-I and to develop further treatments to slow or stall the progression of HIV-I infection to AIDS.

Screening of selected male blood donors for p24 antigen of human immunodeficiency virus type 1. The Transfusion Safety Study Group

BACKGROUND

The p24 antigen of human immunodeficiency virus type 1 (HIV-1) is sometimes detected before antibody (anti-HIV-1) is detectable in the serum of recently infected persons. This has led to the consideration of p24-antigen testing for routine screening of blood donors.

METHODS

To estimate how many HIV-infected seronegative donors would be identified if p24-antigen screening was introduced, we tested selected donations from a repository of 200,000 serum samples from voluntary donors that was established in late 1984 and early 1985. The 8597 serum samples selected for p24-antigen screening were chosen because their donors had demographic characteristics known to be associated with a high prevalence of seropositivity.

RESULTS

The prevalence of anti-HIV-1 antibodies in the 1984-1985 serum samples selected for p24-antigen screening was 1.54 percent--more than 100 times the 0.012 percent prevalence in present-day donations in the United States. The antigen was detected in 15 of 132 serum samples (11.4 percent) from donors who had already been confirmed as seropositive. No instance of confirmed positivity for p24 antigen was found among the 8465 seronegative serum samples.

CONCLUSIONS

These data indicate that the yield of screening for p24 antigen in volunteer donors to identify HIV-1 carriers would be negligible. We therefore recommend against routine screening with currently available p24-antigen assays.

A surgeon's risk of AIDS

A probabilistic model is used to estimate the cumulative risk to surgeons from human immunodeficiency virus (HIV). Recent data suggest that the probability of infection following percutaneous inoculation is about 1 in 250 cases. Several studies suggest that the frequency of percutaneous injury in surgery is at least 1 in 40 cases, for some as high as 1 in 20 cases. Assuming that on the average a surgeon will perform 350 operations per year and will practice for 30 years, the cumulative risk of HIV infection will depend on the prevalence of HIV infection in the surgical population. For HIV prevalences of 1 in 100 to 1 in 10, the cumulative risk per surgeon ranges from 1 in 100 to 1 in 5, respectively. Based on these risk estimates, it is crucial to decrease the frequency of percutaneous injury. The case is made for substantial improvements in barrier protection and modification of surgical technique.

Rapid and quantitative detection of enzymatically amplified HIV-1 DNA using chemiluminescent oligonucleotide probes

A hybridization protection assay (HPA) that uses acridinium ester (AE) labeled oligonucleotide probes which are specific for a conserved gag gene region of human immunodeficiency virus type 1 (HIV-1) was developed to measure the amount of HIV-1 nucleic acid. Hybridization of the single-stranded probes with their target HIV-1 sequences protected the chemiluminescent AE group from subsequent alkaline hydrolysis. The chemiluminescence from the residual AE could be easily quantitated in a luminometer. The entire process comprising template dissociation, hybridization, alkaline hydrolysis, and chemiluminescence measurement can be completed in less than one hour and does not require the separation of hybridized probe from unhybridized probe. We demonstrated that HPA could quantitatively measure the amount of DNA amplified by polymerase chain reaction. A comparative study using amplified DNA from the peripheral blood mononuclear cells (PBMC) of HIV seropositive and seronegative persons showed that HPA was as sensitive as the previous methods using 32P-labeled DNA probes.

Absence of HIV DNA sequences in seronegative polytransfused thalassemic patients

The risk of infection with human immunodeficiency virus (HIV) by transfusion is not totally eliminated, since contaminated blood given before seroconversion to HIV is not detected on the actual biological screening. We used the polymerase chain reaction (PCR) assay (with one primer pair in the gag region and two in the pol region) to detect HIV DNA sequences in 30 seronegative polytransfused thalassemic patients and in 60 seropositive individuals (used as positive controls). We did not observe PCR-positive HIV-antibody-negative results in seronegative polytransfused patients.

Is immune oversuppression the direct cause of AIDS?

AIDS is presumably caused by HIV, a retrovirus. The main support for this view comes from the consistent epidemiological correlation between AIDS and the presence of antibody against HIV. Several HIV-associated mechanisms have been described to explain the cytopathic effects on helper-T-lymphocytes observed in vitro but so far, none of these mechanisms has been confirmed in vivo. On the other hand, there is virtually no free virus and HIV RNA synthesis is very low both in AIDS patients and in asymptomatic carriers. Thus it is unlikely that HIV causes AIDS by acting as a conventional cytocidal virus. Here it is proposed, on the basis of current experimental evidence, that an active immune suppression mediated by T8+ cells is the direct culprit for a gradual decline of helper-T-lymphocyte numbers leading to an immunocompromised state in AIDS. The role of HIV in triggering and perpetuating a state of immune oversuppression is discussed.

Productive human immunodeficiency virus infection levels correlate with AIDS-related manifestations in the patient

Mononuclear cells were obtained from 71 human immunodeficiency virus type 1 (HIV-1) seropositive subjects presenting and first visit either as asymptomatic or with minor symptoms and with CD4 lymphocytes greater than 550 per mm3 (group A, 35 patients) or as patients with AIDS, AIDS-related illnesses, or CD4 lymphocytes less than 400 per mm3 (group B, 36 patients). After 1-5 years of follow-up, 13 patients of group A had essentially retained their initial status (asymptomatics); the 22 others had suffered clinical or immunological deterioration (progressors). Frozen cells were thawed and submitted to lethal gamma-irradiation in vitro (4500 rads; 1 rad = 0.01 Gy) before they were cultured with normal phytohemagglutinin-stimulated lymphocytes to determine radiation-resistant HIV expression ex vivo (R-HEV). HIV antigenemia correlated with R-HEV values in 142 samples (r = 0.92, P less than 0.001) but was a less sensitive predictor of disease than R-HEV. R-HEV was detected in all specimens from patients with major AIDS-related illnesses or HIV-associated CD4 lymphopenia. In 77% of the progressors from group A, R-HEV detection preceded the onset of AIDS-associated disease or CD4 lymphopenia by 1 year (average). Conversely, R-HEV was low or was not detected in 36 sequential specimens from the 13 patients who remained asymptomatic over the following 2-5 years. Thus, persistently low HIV expression in vivo predicted a nondiseased state, whereas higher HIV expression levels seemed necessary for disease to occur. These data indicate that R-HEV is related to productive HIV infection in vivo, the latter acting as a determinant of AIDS-related illnesses. In view of this, measurement of HIV expression levels in the patient should be useful in antiviral efficacy trials.

Transmission of human immunodeficiency virus type 1 by dry-heated clotting factor concentrates. Transfusion Safety Study Group

The Transfusion Safety Study monitored susceptible persons for human immunodeficiency virus type 1 (HIV-1) infections transmitted by plasma products and blood components. Through December, 1988, 6 subjects without antibody to HIV-1 (anti-HIV-1) became seropositive after receiving dry-heated factor VIII concentrate. The preparations implicated in 3 cases were derived entirely from anti-HIV-1-screened donors. In all instances, HIV-1 infection could be explained by concentrates heated at 60 degrees C for 24-30 h. Limiting consideration to concentrates and components administered after study entry showed that 4 of the seroconversions occurred among 122 subjects given 10 million units of factor VIII concentrates. No seroconversions occurred among 84 subjects given 5 million units of factor IX concentrates, or 83 who received components from over 26,000 unpaid donations. Serologic surveillance of anti-HIV-1-negative subjects provides important information, and should be routine in the management of persons receiving clotting factor concentrates.

The ethical conduct of clinical trials of HIV vaccines

Clinical trials of candidate HIV vaccines pose virtually all of the problems possible in vaccine trials. Resolving them consistently with accepted ethical principles is likely to make trials logistically more difficult, longer, and more expensive than usual. Yet few of these problems are unique to HIV vaccines. What is unique are the social risks that research subjects may face. The major obstacles to testing vaccine candidates in human beings are the same ones that have hindered vaccine development-insufficient knowledge about the virus and the human immune response. The necessarily urgent search for a vaccine to prevent HIV infection does not require subjecting people to unnecessary risks. This article outlines key ethical obstacles to identifying candidate vaccines to test, with special attention to clarifying the benefits and risks of testing experimental vaccines in healthy research subjects. Assuming that such obstacles can be overcome, the article examines how ethical principles governing biomedical research may apply to the design and conduct of clinical trials to ensure independent review of proposed research, identify measures of vaccine effectiveness, identify and monitor suitable research subjects, provide adequate counseling, protect confidential information, and assure compensation for injury and access to any successful vaccine.

Diagnosis of Chlamydia trachomatis cervical infection by detection of amplified DNA with an enzyme immunoassay

A sensitive and specific system for detection of amplified Chlamydia trachomatis DNA from cervical specimens by fluorometric quantitation in an enzyme immunoassay (EIA) format (polymerase chain reaction [PCR]-EIA) is described. The primers selected for PCR-amplified DNA were from the 15 serovars of C. trachomatis and two strains of Chlamydia pneumoniae (TWAR). One strain of Chlamydia psittaci (Borg) was not amplified. One hundred four previously cultured cervical specimens were evaluated. Forty-six culture-positive specimens containing from 1+ to 4+ inclusion bodies were all positive by PCR-EIA. Of 58 culture-negative specimens, 2 were repeatedly positive and were nonreactive with control probes. This assay system represents a sensitive and specific combination of technologies for the quantitative detection of C. trachomatis DNA directly from a body fluid.

Operating on HIV-positive patients. What are the risks to healthcare workers? To patients?

Is the degree of risk involved in providing health care to people infected with human immunodeficiency virus (HIV) acceptable? Every health care worker, even if only for a few anxious minutes, has certainly worried about this risk. Drs Wilson, Williams, and Robinson discuss these concerns and summarize the indications and prognoses for surgery to treat some common AIDS-related syndromes.

A synthetic protein corresponding to the entire vpr gene product from the human immunodeficiency virus HIV-1 is recognized by antibodies from HIV-infected patients

The 95 amino acid-protein encoded by the non-structural vpr gene of the human immunodeficiency virus type 1 (LAV-1BRU isolate) was chemically synthesized by solid phase methodology. The synthetic vpr protein was characterized by amino acid analysis, sequence analysis, RP-HPLC, and urea-SDS PAGE. Using a radioimmunoassay, antibodies to the synthetic protein were detected in sera of 25% of HIV 1-seropositive patients tested. Western blot analysis suggested that the antibodies preferentially recognize the dimeric form of vpr.

Human immunodeficiency virus infection and the intestine

HIV is a retrovirus infecting CD4-positive cells causing profound immunosuppression, eventually clinically manifest as AIDS. The cells principally infected by HIV are T4 lymphocytes (helper) and macrophages. The eventual loss of helper cell function is the prime reason for immunodeficiency which renders the individual susceptible to opportunistic infections. HIV infection was first described in male homosexuals. However, the trend now is for seroprevalence to rise rapidly in intravenous drug abusers in the West. In addition, African AIDS is thought to be almost exclusively heterosexual in nature, a paradox which is not yet fully explained in comparison with the relatively low but increasing incidence in heterosexuals in the Western world. Virtually every organ system in the body can be affected clinically during the course of HIV infection. The gastrointestinal tract is a major target, and the physiological sequelae are an important cause of morbidity and mortality. The pathophysiology of intestinal infection is not yet fully understood, however two main mechanisms have been postulated. The first is reduced intestinal immunity resulting in chronic opportunistic infections, which themselves caused altered intestinal function. The second is that HIV itself affects the intestinal mucosa, causing malfunction. The mechanisms by which the latter occurs are controversial but may result from either direct infection of mucosal epithelial cells or macrophages within the mucosa. Reports have documented the presence of HIV genome in both epithelial argentachromaffin cells and macrophages. In addition, profound degeneration of intrinsic jejunal autonomic neurones has been demonstrated, but the functional significance of such denervation is as yet unknown. The clinical stage of HIV infection at which intestinal mucosal immunity fails is by definition when opportunistic infection occurs (that is, clinical progression to stage IV disease), namely AIDS, however a detailed knowledge of the mechanisms of intestinal immune failure are lacking.

HIV-1 infection in HIV-1 enzyme-linked immunoassay seronegative patients in Kinshasa, Zaire

Serum samples of 62 African patients who had clinical manifestations of HIV-1 infection but were seronegative for HIV-1 by ELISA (Organon) were subsequently further tested by another HIV-1 ELISA test (Wellcozyme), HIV-1 IgG Western blot, HIV-1 antigen detection and HIV-2 ELISA. Patients' lymphocytes were cultured for HIV-1 and 2. Because of limited quantities of serum available all tests were not performed on all samples. Seven (26%) of 27 sera of patients meeting the WHO clinical case definition of AIDS were Western-blot-positive. In contrast, of 35 patients' sera with possible HIV related disease, only one (3%) was Western blot positive (P = 0.02) and none of 75 sera from HIV-1 ELISA (Organon) seronegative blood donors (P less than 0.01) were Western blot positive. Of 30 HIV-1 ELISA (Organon) seronegative patients tested with the HIV-1 ELISA Wellcozyme assay only one was seropositive (this patient's serum was also Western blot positive). Of 17 HIV-1 ELISA (Organon) seronegative patients tested, HIV-1 antigen was found in 1 case (6%) (this patient's serum was Western blot negative). None of the 34 patients tested by HIV-2 serology was HIV-2 seropositive. HIV-1 was isolated by culture in 3 (21%) of 14 HIV-1 ELISA seronegative patients (sera of the 3 patients were Western blot negative). In total, 12 (19%) of 62 HIV-1 ELISA (Organon) seronegative patients were found to be positive for HIV, either by Western blot HIV antigen testing or viral culture.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitation of human immunodeficiency virus DNA by using the polymerase chain reaction

The polymerase chain reaction was used to measure the DNA copy number of human immunodeficiency virus (HIV). Differences in polymerase chain reaction amplification efficiency were controlled by amplifying known amounts of HIV DNA in parallel with samples. This technique is a sensitive, accurate, and reproducible method for the quantitation of HIV DNA.

The technique of polymerase chain reaction--a new diagnostic tool in microbiology and other scientific fields (review)

The polymerase chain reaction, a method of so far unknown sensitivity and specificity, is about to become an important diagnostic tool in microbiology. Practically even a single bacterium, virus particle, or parasite can be detected by it. Furthermore, this technique has been used with highly promising results in other scientific fields like genetics, forensic medicine and archeology. This article reviews technical aspects and variations of this new technique.

Antibodies to HIV-1 nef(p27): prevalence, significance, and relationship to seroconversion

A sensitive and specific enzyme-linked immunoassay for antibodies to the human immunodeficiency virus type 1 (HIV-1) nef gene product, p27, has been developed using recombinant Escherichia coli-derived protein from the LAV-1-Bru sequence. Of 92 HIV-1 infected hemophiliacs, 72 (78%) produced anti-nef antibodies in this assay; the early appearance of anti-nef prior to full seroconversion was a rare event in this population, occurring in only one subject (approximately 1%). Anti-nef antibodies were not detected in any of 500 sera from 98 repeatedly HIV seronegative subjects who had been exposed to sexually transmitted modes of HIV infection (45 subjects) or through blood products (53 subjects). There was no significant association of titer or anti-nef antibody with protection from disease in HIV infection (p = 0.1). Although the nef protein is relatively immunogenic in natural infection, this study cannot confirm the previously reported high prevalence of anti-nef antibodies prior to seroconversion, nor the finding of anti-nef antibodies in HIV seronegative but exposed subjects.

Elevated levels of CD4 antigen in sera of human immunodeficiency virus-infected populations

CD4 antigen levels in sera from asymptomatic intravenous drug users and homosexuals and patients with lymphadenopathy, acquired immunodeficiency syndrome-related complex, or acquired immunodeficiency syndrome were quantitated. Like soluble CD8, CD4 antigen levels were elevated in human immunodeficiency virus-seronegative asymptomatic intravenous drug users and homosexuals, probably reflecting infections such as cytomegalovirus, Epstein-Barr virus, and hepatitis B virus infections. The sera from human immunodeficiency virus-seropositive groups of patients with human immunodeficiency virus infection also had elevated levels of CD4 antigen, presumably reflecting infections like cytomegalovirus and human immunodeficiency virus infections.

Nucleic acid hybridization in viral diagnosis

Since 1982, numerous studies have been published utilizing a variety of hybridization techniques to detect viral nucleic acid directly in clinical specimens and in tissue sections. However, hybridization techniques are still not widely used in the clinical laboratory. Other recent advances, such as the development of monoclonal antibodies for virus identification and ELISA kits for virus detection, and the introduction of centrifugation cultures for rapid diagnosis, have postponed the clinical application of hybridization techniques. Furthermore, the use of hybridization for diagnosis has been limited by its insensitivity when compared to cell culture, the need for radioisotopes to increase sensitivity, and the difficulties inherent in transferring a basic research tool to the clinical laboratory. Nevertheless, with recently developed amplification techniques and further advances in nonradioactive labelling of probes, it can be expected that nucleic acid hybridization will be an established technique in diagnostic laboratories in the near future.

Recombinant DNA and surgery

We have the ability to isolate DNA from tissue, determine its base-pair sequence, and ask if a gene of interest is present. DNA strands can be isolated from one type of cell or organism, cleaved, and inserted (recombined) with DNA from another cell or organism. Recombinant DNA techniques have already improved health care by providing clinically useful quantities of pure human protein hormones such as erythropoietin, insulin, and growth hormone. Furthermore these techniques may increase our understanding of cellular growth control mechanisms to a level that was previously unattainable. They will also increase our knowledge of the development of major diseases and provide a means of specific nontoxic therapies for these diseases. Surgeons will need to understand basic DNA research terminology to keep up with the revolution in medical therapies that these techniques will cause. Our purpose is to begin the process of linking surgery to DNA.

Longitudinal predictors of reductions in unprotected anal intercourse among gay men in San Francisco: the AIDS Behavioral Research Project

Predictors of unprotected anal intercourse were examined among 508 gay men in San Francisco. The cohort was recruited in 1983-84 at which time 49.8 percent of non-monogamous men (N = 435) and 71.2 percent of monogamous men (N = 73) reported practicing unprotected anal intercourse. Only 12 percent of non-monogamous and 27.4 percent of monogamous men reported these practices in 1988. The non-monogamous men who practiced unprotected anal intercourse in 1984 were more likely to be younger, to report that unprotected anal intercourse was their favorite sexual activity, to be low in perceived efficacy to change sexual behavior, to report that friends were more likely to engage in high-risk behaviors, to have less knowledge of health guidelines, and to be less depressed at that time. Non-monogamous individuals who in 1984 reported that unprotected anal intercourse was their favorite sexual activity were more likely to practice that behavior in 1988. Those who knew their serostatus as positive were less likely to report unprotected anal intercourse in 1988. These data infer that in order to modify AIDS-related high-risk behaviors, community risk-reduction programs be differentially aimed at young persons so as to increase personal efficacy about risk reduction, challenge peer norms, promote antibody testing, and eroticize safer sexual activities.

[Interviews with HIV seropositive subjects identified at the time of blood donation: consequences for pre-donation interviews]

This study is based upon an interview with 31 individuals recently detected human immunodeficiency virus (HIV) seropositive through the systematic screening of blood donations. The location of the blood donation, the type of blood donor, the risk of HIV infection, were established. Questions dealt with the use of blood donation as a diagnosis test and on the notion of an oral or written self-exclusion before the blood donation. The majority of the individuals had a classical risk factor of HIV infection and had given blood for serological testing. This data can allow an adaptation of the medical interview preceding the blood donation to the present epidemiological context of HIV infection.

Detection of human immunodeficiency virus-1 by polymerase chain reaction and virus cultivation

Peripheral blood of 57 patients with antibodies to human immunodeficiency virus 1 (HIV-1) and of five HIV-1 seronegative subjects at risk for HIV-1 infection were analysed by polymerase chain reaction (PCR) and virus isolation. The virus was recovered from peripheral blood cells in 89% and from plasma in 75% of the HIV-1 seropositive cases. In contrast, proviral HIV-1 DNA was detected in all HIV-1 seropositive patients by dot blot hybridization of the amplified fragments. The intensities of the dot blot reactions were less pronounced in asymptomatic HIV-1 seropositive individuals than in patients with acquired immunodeficiency syndrome (AIDS) or AIDS-related complex (ARC), suggesting an increase in proviral DNA with advancing disease. Three of five seronegative patients with signs or symptoms suggesting HIV-1 infection, but none of the controls, were positive for HIV-1 DNA by one or two primer pairs. These results show a high sensitivity of the PCR for detecting HIV-1 DNA in patients of all stages of HIV-1 infection. Proviral DNA can also be detected in some individuals without detectable antibodies to the virus. The virus load in peripheral blood, as determined by virus cultivation and PCR, seems to increase with progression of the infection.

Simple, sensitive, and specific detection of human immunodeficiency virus type 1 in clinical specimens by polymerase chain reaction with nested primers

A simple, sensitive, and specific polymerase chain reaction (PCR) protocol for the detection of human immunodeficiency virus type 1 (HIV-1) is described. We have improved all three PCR steps: sample preparation, DNA amplification, and detection of the amplified product. Some of the improvements have been described previously, but they have never been combined into a complete PCR protocol. Peripheral blood mononuclear cells were lysed directly in a buffer containing sodium dodecyl sulfate, Triton X-100, and proteinase K. This crude cell lysate was amplified in a two-step PCR, first with outer primers and then with inner primers nested within the first primers. The PCR product was visualized by agarose gel electrophoresis and ethidium bromide staining. Thus, we avoided conventional DNA extraction as well as hybridization for the detection of the PCR product. The samples were analyzed with four sets of nested primers (JA4 through JA7, JA9 through JA12, JA13 through JA16, and JA17 through JA20) designed to amplify HIV-1 gag, env gp120, env gp41, and pol sequences, respectively. We were able to amplify HIV-1 sequences in all samples from 90 HIV-1-seropositive individuals with mostly mild symptoms. Of these individuals, 24 were negative in HIV-1 isolation and 9 were selected because they were infected by African and Haitian HIV-1 strains. Eighty-five (94%) individuals were positive with at least three of four primer sets. Samples from 26 healthy blood donors, as well as cells infected in vitro with human immunodeficiency virus type 2 and human T-cell leukemia virus type I, were negative in PCR, thus demonstrating the specificity of the amplification.

AIDS: practising safe endoscopy

The emergence of HIV has provoked a widespread reappraisal of infection control practices in endoscopy units. Infection control practices should be applied to all patients alike without recourse to selection or screening. Although there has only been one reported instance of viral transmission at endoscopy, HIV could in theory be transmitted by a contaminated endoscope. Experience suggests that this is more likely to occur from damaged endoscopes, if an unsuitable disinfectant is used or endoscopes are not precleaned. In-use studies have shown that HIV contaminates endoscopes used on patients with AIDS, but in amounts too small to cause infection in tissue cultures. Cleaning in neutral detergent is extremely effective in removing contaminating micro-organisms, including HIV, from endoscopes. Aldehydes are the disinfectants of choice, but any disinfectant may fail if organic material is not removed by cleaning. After thorough cleaning, short disinfection times (e.g. four minutes) ensure inactivation of all relevant micro-organisms except Cryptosporidium and mycobacteria, although in practice even these organisms are likely to be reduced to non-pathogenic levels. Accidental needlestick injuries are the greatest hazard in the endoscopy suite; needles should not be resheathed and biopsy forceps must be handled with great care. The wearing of gloves should become second nature.

Enzyme immunoassay for detection of hybrids between PCR-amplified HIV-1 DNA and a RNA probe: PCR-EIA

An enzyme immunoassay was developed to detect human immunodeficiency virus type 1 (HIV-1) DNA amplified by polymerase chain reaction (PCR-EIA). A set of primers (outer set) was used in PCR to amplify a segment of the HIV-1 gag gene from peripheral blood mononuclear cells. Hybrids between the amplified DNA and a RNA probe were measured in a microtiter plate immunoassay using a beta-D-galactosidase-conjugated monoclonal antibody to DNA-RNA hybrids and a fluorescent substrate. A second set of primers (nested set) located within the outer set was used in PCR with a known template to prepare the probe. One primer of the nested set included the T7 RNA polymerase promoter at its 5' end allowing transcription of a single-stranded RNA probe. Ten copies of HIV-1 DNA could be detected by PCR-EIA (42 fluorescent units with a background of 18 fluorescent units) compared with a detection limit of 1000 copies by ethidium bromide-stained agarose gel. HIV-1 DNA was detected by PCR-EIA in peripheral blood mononuclear cells from 32 of 33 seropositive patients (range 54-810 fluorescent units), and 0 of 25 seronegative patients (range 20-40 fluorescent units) (sensitivity 97%; specificity 100%). PCR-EIA offers a practical and nonisotopic method to objectively measure PCR-amplified HIV-1 DNA and has the potential for the measurement of other microbial pathogens in human body fluids.

Asymptomatic patients with HIV infection. Keeping them well

Primary care physicians need to be prepared to counsel and manage patients with human immunodeficiency virus (HIV) infection. Asymptomatic seropositive patients should be seen quarterly, and T4 lymphocyte counts should be followed. Other serologic markers that may detect disease progression are p24 antigen and beta 2 microglobulin. Abnormalities in the levels of these markers may influence the decision to initiate early antiretroviral therapy. Therapeutic regimens are now available for delaying progression of HIV disease and for preventing Pneumocystis carinii pneumonia, the most common opportunistic infection to develop in patients with HIV infection. Whether antiretroviral therapy should be initiated in all asymptomatic HIV-positive patients remains to be seen. Physicians can do their part by educating themselves about HIV infection so they can provide competent, nonjudgmental care to patients and by supporting legislation to protect the rights of HIV-infected persons.

Affinity-based collection of amplified viral DNA: application to the detection of human immunodeficiency virus type 1, human cytomegalovirus and human papillomavirus type 16

We have devised a sensitive and convenient hybridization technique by combining the polymerase chain reaction (PCR) with affinity-based hybrid collection. In this method 5'-biotinylated primers are used to introduce biotin residues into the DNA fragments during the amplification. The amplified DNA fragments are detected by liquid hybridization using a 32P- or 35S-labelled oligonucleotide as probe. For measurement the hybrids are collected on polystyrene microparticles or onto microtitre wells taking advantage of the biotinavidin interaction. The method is highly sensitive allowing the detection of 30 molecules of DNA. It involves few and simple operations, and is thus suitable for routine diagnostics. The applicability of the method to the detection of HIV-1 DNA from blood, HCMV DNA from urine and HPV-16 DNA from cervical scrapes was evaluated.

Risks, options, and informed consent for blood transfusion in elective surgery

Blood banking is undergoing a period of significant change as a result of several concurrent issues. Blood-transmitted diseases such as human immunodeficiency virus (HIV) and the alternatives to community-derived (homologous) blood such as autologous (patient's own) and designated (blood donor known to transfusion recipient) blood have had an impact on surgical transfusion practice. Many of these issues comprise the medicolegal elements of informed consent for elective blood transfusion, so that increasingly the need for a dialogue incorporating these issues between the transfusing physician and the potential transfusion recipient is recognized. If the process is to be effective, then early involvement of the patient in a dialogue concerning informed consent is necessary. An overview of the medical elements and content of informed consent for elective blood transfusion is presented.

Antigenic epitopes of NEF proteins from different HIV-1 strains as recognized by sera from patients with manifest and latent HIV infection

Human immunodeficiency virus (HIV) infection that generally causes a strong antibody response toward HIV may sometimes occur in a latent form, characterized by seronegativity in assays based on structural HIV proteins. Latently infected individuals, however, often have an antibody response against the nonstructural regulatory HIV-1 protein NEF, a factor implicated in down-regulation of viral expression. In order to define the specificity of NEF antibodies, we looked for antibody response against more than 600 overlapping nonapeptides representing the total NEF sequence of three different HIV-1 isolates BRU, SF2, and MAL. Nine distinct homologous antigenic epitopes were recognized by sera from seropositive HIV-1-infected individuals by the peptide ELISA. We further demonstrated that sera from "at risk" individuals, with no antibodies to HIV structural proteins but reacting with the recombinant NEF protein in Western blot, recognize the same epitopes. Immunological assays based on the defined NEF epitopes can therefore be used to diagnose early or latent HIV Infection.

AIDS-related B-cell non-Hodgkin's lymphomas in direct blood-stream HIV-infected patients: pathogenesis and differentiation features

Six AIDS-related NHLs from direct blood-stream HIV-infected patients were characterized for clonality, maturation cell characteristics, activation of c-myc proto-oncogene and presence of HIV and EBV genomes. Four out of the 6 AIDS-related NHLs were of immature B-cell origin, contrasting with the lower frequency (2 out of 31) of immature B-cell NHLs occurring in HIV-negative patients. Moreover, 3 out of the 4 AIDS-related pre-B-NHLs were extranodal lymphomas. C-myc translocations or rearrangements were not found in Italian AIDS-related NHLs, unlike c-myc activation which had a high prevalence in the American series of AIDS-related NHLs. HIV and EBV are not, or only occasionally, directly involved in AIDS-related NHL pathogenesis since HIV genome has never been found in the neoplastic clones and EBV genome was detected in only 1 out of the 6 lymphomas analyzed.

Polyclonal B-cell activation reveals antibodies against human immunodeficiency virus type 1 (HIV-1) in HIV-1-seronegative individuals

Identification of human immunodeficiency virus type 1 (HIV-1)-infected individuals is of paramount importance for the control of the spread of AIDS worldwide. Currently, the vast majority of screening centers throughout the world rely on serological techniques. As such, clinically asymptomatic but HIV-infected, seronegative individuals are rarely identified. In this report we show that 18% (30/165) of seronegative individuals who were considered to be a unique cohort of patients at high risk for HIV infection had circulating B cells that, upon in vitro polyclonal activation with pokeweed mitogen, produced antibodies reactive with HIV. Furthermore, polymerase chain reaction analysis of DNA obtained from aliquots of the peripheral blood mononuclear cells from these seronegative but pokeweed mitogen assay-positive individuals tested revealed the presence of HIV-specific sequences in a significant number of samples. In addition, depletion of CD8+ T cells from peripheral blood mononuclear cells of HIV-1-seronegative individuals prior to in vitro culture with pokeweed mitogen resulted in increased sensitivity for detecting HIV-reactive antibodies. This assay has obvious epidemiological implications, especially in the case of high-risk groups, and also provides a simple technique to enhance detection of HIV-infected individuals. Of further interest is the determination of the mechanisms related to the lack of HIV-specific antibodies in the serum of these infected individuals.

Proviral sequences detection of human immunodeficiency virus in seronegative subjects by polymerase chain reaction

Human immunodeficiency virus type 1 (HIV-1) can be isolated from lymphocytes and tissues of symptomatic and asymptomatic seropositive subjects. However, in some individuals, virus isolation is not always positive, especially in asymptomatics. In this paper we report the results of HIV-1 DNA detection by means of polymerase chain reaction (PCR), a new technique that permits the amplification of specific DNA sequences. PCR was carried out to amplify two highly conserved env regions on samples from 20 normal individuals used as controls, 20 seropositive patients at different stages of HIV disease and 25 seronegative individuals at high risk for infection, such as sexual partners of seropositive patients and intravenous drug addicts. Eighteen out of 20 seropositive subjects were positive by PCR while among seronegatives HIV DNA was detected in 7/25 individuals. Virus isolation was positive only in 2/7. These subjects, followed for HIV antibody production for a period of 10-12 months, remained seronegative except one case who seroconverted after a few weeks. Long latency of HIV infection without detectable antibodies seems prevalent in these subjects. PCR assay represents a useful technique for identifying proviral sequences in seronegative high-risk individuals, to confirm the infection during its early phases and during the follow-up of patients with HIV disease.

Mechanisms of infectivity and replication of HIV-1 and implications for therapy

Human immunodeficiency virus type 1 (HIV-1), a retrovirus, is the etiologic agent of AIDS. Like all retroviruses, the viral genes are carried in the viral particle in the form of single-stranded RNA. Once inside a susceptible host cell, this RNA template is reverse-transcribed by virally supplied enzyme functions into a DNA copy, which becomes integrated permanently into the host's own genetic material. The genome of HIV-1, comprising approximately 10,000 bases, is much more complex than those of classic retroviruses, encoding a minimum of six gene products in addition to the gag, pol, and env genes characteristic of all retroviruses. These genes encode regulatory functions that act at diverse points in the virus life cycle. Together, they provide HIV-1 with an exceptional ability to modulate its replication depending on its host environment. This characteristic is reflected in the different stages presented by the disease and the diverse behaviors of the virus in different types of host cells. A greater understanding of the mechanics of this regulation and the factors that influence it may someday permit therapeutic intervention in the disease process that will halt virus replication and the progression of pathology in infected individuals.

Determination of the spread of HIV from the AIDS incidence history

The relation between the incidence of HIV in the general population, the number of AIDS cases, and the incubation period for the disease is examined. The number of AIDS cases can be expressed in terms of a convolution integral over the incubation period distribution and the temporal history of HIV incidence. In order to determine the level of HIV incidence it is necessary to invert the convolution. In this manner, it is possible to determine the spread of HIV up to the present time from knowledge of the AIDS incidence history and the incubation period. We describe the inversion of the convolution in terms of a Laplace transform technique that is applicable for any given incubation period distribution. Substantial simplifications in the technique are found in the case of an Erlang distribution for the probability density. The spread of HIV infections in the United States is charted through 1988 using AIDS incidence data that are corrected for both the revised AIDS case definition and reporting time delays. The results are consistent with current estimates of the HIV incidence in the United States and show no evidence of saturation in the rate of new infections. Indeed, the rate of new infections still appears to be climbing as of that date. While the technique is unable to predict the future course of the epidemic, it may provide a useful benchmark for comparison with mathematical models of the epidemic. The techniques are conceptually applicable to diseases other than AIDS.

Human immunodeficiency virus and the gastrointestinal tract

Human immunodeficiency virus (HIV) is a retrovirus infecting CD4 positive cells, causing profound immunosuppression and eventually manifesting clinically as the acquired immunodeficiency syndrome (AIDS). The cells principally infected by HIV are T4 (helper) lymphocytes and macrophages. The eventual loss of helper cell function is the prime reason for immunodeficiency, which renders the individual susceptible to opportunistic infections. Virtually every organ system in the body can be affected clinically during the course of HIV infection. The gastrointestinal tract is a major target and the physiological sequelae are an important cause of morbidity and mortality. The pathophysiology of intestinal infection is not yet fully understood but two main mechanisms have been postulated. The first is reduced intestinal immunity resulting in chronic opportunistic infections, which themselves cause altered intestinal function. The second is that HIV per se affects the intestinal mucosa, causing malfunction. The mechanisms by which the latter occurs are controversial but may result from either direct infection of mucosal epithelial cells or from macrophages within the mucosa. Reports have documented the presence of the HIV genome in both epithelial argentochromaffin cells and macrophages. In addition, profound degeneration of intrinsic jejunal autonomic neurones has been demonstrated but the functional significance of such denervation is as yet unknown. The clinical stage of HIV infection at which intestinal mucosal immunity fails is, by definition, when opportunistic infection occurs (that is, clinical progression to stage 4 disease, namely AIDS) but detailed knowledge of the aetiology of intestinal immune failure is lacking. However, protection of intestinal mucosal surfaces with antibodies against HIV, induced by vaccination using the oral or rectal route, is an area of great interest. The major site of entry of HIV is thought to be via the intestinal tract and thus protection of its surfaces may be crucial in preventing infection.