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

Variation in virological parameters and antibody responses in macaques after atraumatic vaginal exposure to a pathogenic primary isolate of SIVmac251

We developed an animal model for the male-to-female transmission of human immunodeficiency virus, consisting of an atraumatic vaginal application of simian immunodeficiency virus onto the intact vaginal mucosa of cynomolgus macaques. Different doses of a pathogenic isolate of SIVmac251, with or without seminal plasma, were infused into the vaginas of female macaques. Infection of macaques could be achieved after a single exposure to the virus. Two patterns of infection were underscored with no relation to the virus dose inoculated: in 50% of the monkeys, SIV was persistently recovered and a strong antibody response to SIV was evidenced in blood and vaginal secretions. In the other infected animals, SIV infection was only transiently evidenced and a weak systemic antibody response was detected. It appeared that the presence of seminal plasma may be implicated in this variability only when low doses of virus are inoculated. Sequence analysis of the env gene of SIV revealed that most of the persistently viraemic animals were infected with a viral variant different from that of transiently viraemic macaques.

Biosensor technology and surface plasmon resonance for real-time detection of HIV-1 genomic sequences amplified by polymerase chain reaction

BACKGROUND

The recent development of biosensor technologies for biospecific interaction analysis enables the monitoring of a variety of molecular reactions in real time by surface plasmon resonance (SPR). If the ligand is a biotinylated single stranded DNA, this technology could monitor DNA-DNA hybridization. This approach could be of great interest in virology, since the hybridization step is oftenly required to confirm specificity of molecular diagnosis.

OBJECTIVES

To determine whether real-time molecular diagnosis of human immunodeficiency virus type I (HIV-1) could be performed using biosensors and SPR technology.

STUDY DESIGN

Specific hybridization of a biotinylated HIV-1 oligonucleotide probe immobilized on a sensor chip to single stranded DNA obtained by asymmetric polymerase-chain reaction (PCR) was determined using the BIAcore biosensor.

RESULTS

Direct injection of asymmetric PCR to a sensor chip carrying an internal HIV-1 oligonucleotide probe allows detection of hybridization by SPR using biosensor technology. This enabled us to apply a real-time, one-step, non-radioactive protocol to demonstrate the specificity of amplification of HIV-1 genomic sequences by PCR.

CONCLUSION

The procedure described in this study for HIV-1 detection is simple, fast (PCR and SPR analyses take 30 min), reproducible and could be proposed as an integral part of automated diagnostic systems based on the use of laboratory workstations and biosensors for DNA isolation, preparation of PCR reactions and analysis of PCR products.

Whose blood is safer? The effect of the stage of the epidemic on screening for HIV

BACKGROUND

With improvements in HIV antibody test (ELISA) performance, the window of time between infection and seroconversion becomes a major source of error in HIV screening. The authors examined its impact on the false-reassurance rate (FRR).

METHODS

Test sensitivity was modeled as the product of two factors: the inherent sensitivity (sensitivity when antibody is present) and the probability that antibody is present in infected blood. A model of HIV and AIDS incidence was used to derive an estimate of the probability of remaining in the seronegative window (pw) among those who are infected. With plausible assumptions, this probability approaches 0.03. The FRR was then estimated as a function of the probability of remaining in the seronegative window, the prevalence of HIV, and the inherent sensitivity of the ELISA test were estimated.

RESULTS

The FRRs for two blood donor groups, one with an HIV prevalence of 0.004 and a typical probability of remaining in the seronegative window (pw = 0.03) and the other with a higher prevalence of 0.017 but fewer donors in the window (pw = 0.003), are equal (140 per million donors) if the blood is negative on a single ELISA test. After two negative tests or a single test that can detect antibody more reliably, however, the FRR is much higher in the group with the higher pw (= 120 per million compared with 50 per million), because the greater numbers of donors in the window more than offsets the lower prevalence.

CONCLUSION

With improvements in inherent sensitivity of ELISA by virtue of technical progress or retesting, the prevalence of HIV infection may no longer play the critical role in degrading the results of blood screening. As inherent test performance improves, tests are increasingly likely to miss infected blood because of the seronegative-window error rather than because of measurement error. Window error plays a proportionally greater role during the early stages of HIV dissemination in a population where the incidence of new HIV infection is high relative to the incidence of AIDS. These findings may explain, in part, the recent observation that cases of transfusion of contaminated blood often take place in areas where AIDS epidemics have started recently. They also suggest that the traditional strategy of soliciting blood donors from low-prevalence populations may not always be optimal, unless such populations are truly low-risk.

Laboratory diagnostic tests for retrovirus infections of small ruminants

The most practical and reliable approach to confirming a diagnosis of OPPV or CAEV infection is a combination of serology and clinical evaluation. Although serology represents the most cost effective method of diagnosing persistently infected, clinically normal animals, testing errors occur; the frequency of error depends on the performance data of the particular serologic assay being used. When PCR detection of OPPV and CAEV becomes routinely available, this detection method can be used in rigorous eradication programs to determine the infection status of animals that cannot be definitively diagnosed by serology. The important aspects of OPPV and CAEV infection that must be considered in designing programs to prevent transmission are (1) OPPV and CAEV persist for life in the infected host, (2) a major route of transmission is to lambs and kids via colostrum and milk during nursing, (3) contact transmission among adults can occur, and (4) time variability can exist among individual sheep and goats from infection to the appearance of detectable antibodies.

Resistance to HIV-1 infection among persistently seronegative prostitutes in Nairobi, Kenya

BACKGROUND

There is indirect evidence that HIV-1 exposure does not inevitably lead to persistent infection. Heterogeneity in susceptibility to infection could be due to protective immunity. The objective of this study was to find out whether in highly HIV-1-exposed populations some individuals are resistant to infection.

METHODS

We did an observational cohort study of incident HIV-1 infection-among 424 initially HIV-1-seronegative prostitutes in Nairobi, Kenya, between 1985 and 1994. 239 women seroconverted to HIV-1 during the study period. Exponential, Weibull, and mixture survival models were used to examine the effect of the duration of follow-up on incidence of HIV-1 infection. The influence of the duration of exposure to HIV-1 through prostitution on seroconversion risk was examined by Cox proportional hazards modelling, with control for other known or suspected risk factors for incident HIV-1 infection. HIV-1 PCR with env, nef, and vif gene primers was done on 43 persistently seronegative prostitutes who remained seronegative after 3 or more years of follow-up.

FINDINGS

Modelling of the time to HIV-1 seroconversion showed that the incidence of HIV-1 seroconversion decreased with increasing duration of exposure, which indicates that there is heterogeneity in HIV-1 susceptibility or acquired immunity to HIV-1. Each weighted year of exposure through prostitution resulted in a 1.2-fold reduction in HIV-1 seroconversion risk (hazard ratio 0.83 [95% CI 0.79-0.88], p < 0.0001). Analyses of epidemiological and laboratory data, show that persistent seronegativity is not explained by seronegative HIV-1 infection or by differences in risk factors for HIV-1 infection such as safer sexual behaviours or the incidence of other sexually transmitted infections.

INTERPRETATION

We conclude that a small proportion of highly exposed individuals, who may have natural protective immunity to HIV-1, are resistant to HIV-1.

Rapid, non-radioactive detection of virus infection by polymerase chain reaction

BACKGROUND

Polymerase chain reaction (PCR) diagnosis of infectious diseases, especially virus diseases, offers a very sensitive and specific technique for clinical diagnosis. However, detection systems for amplified DNA requiring radioactive probe hybridization or signal development using blot transfer or nucleotide capture require overnight incubation or specially labeled probe molecules for analysis of amplified DNA.

OBJECTIVES

To place this technology in the clinical laboratory, rapid and sensitive methods are needed for the detection of amplified DNA which are applicable to the assay of multiple specimens representing many different organisms and requiring a minimum of manipulation.

STUDY DESIGN

Electrophoretic separation of amplified DNA fragments, stained with the fluorescent dye SYBR Green I, and laser scanning of the gels for detection of virus-specific PCR products was compared with detection of amplified DNA by liquid hybridization with radioactive probes and gel retardation analysis of labeled probe molecules.

RESULTS

Fluorescent scanning methodology was applied to the detection of cytomegalovirus (CMV), herpes simplex virus (HSV) and the human immunodeficiency virus (HIV). This method was at least 10 times more sensitive than radioactive probe hybridization in the detection of CMV-specific PCR products. This method also required less time and avoided the use of radioactivity.

CONCLUSIONS

Clinical diagnosis of virus infections can be conveniently and rapidly accomplished, while avoiding the dangers of radioactive probe handling, by fluorescence staining and laser scanning of specifically amplified gene fragments. This technology is applicable to the detection of genes from many different organisms, without specially synthesized and/or labeled oligonucleotide primer or probe sequences.

Persistently seronegative men from whom HIV-1 has been isolated are genetically and immunologically distinct

Studies in both monkeys and humans have suggested that transient infection with HIV-1 can occur without provoking a measurable humoral immune response. The objective of this study was to look for genetic and immunologic correlates of transient HIV-1 infection in antibody-negative men from whom HIV-1 had been isolated. The distributions of MHC class I, class II, and TAP (transporter protein associated with antigen processing) region genes were compared between 23 persistently seronegative men from whom HIV-1 was isolated at least once (isol+/Ab-) and 137 men who seroconverted. A subset of 13 of the 23 isol+/Ab- men were compared to 27 seronegative men for distribution of CD25+CD4+ and CD25+CD8+ cells in the absence of exogenous immunologic stimulation. The prevalences of the TAP1.4, and a combination of TAP1.4, and TAP2.3 variants were significantly higher in the isol+/Ab- men. The proportion of CD8+ cells that expressed CD25+ antigen was also significantly higher in the isol+/Ab- men than in the seronegative men. We conclude that isol+/Ab- men may be genetically and immunologically distinct from HIV-1 susceptible men. We hypothesize that activated CD8+ cells may have cleared HIV-1 infection in these men through genetically mediated influences of the TAP genes on the presentation of peptides by HLA class I molecules.

Comparison of the sensitivities of two non-isotopic reverse transcriptase (RT) assays for human immunodeficiency virus type 1 RT

The sensitivities of two reverse transcriptase (RT) assays, an enzyme-linked oligonucleotide sorbent assay (ELOSA)-RT assay and a non-radioisotopic (non-RI) RT assay were compared. For measuring recombinant HIV-1 RT, the ELOSA-RT assay was 8 times less sensitive in dilution endpoint and 16 times less sensitive in measurement of RT from pelleted HIV-1 than the non-RI RT assay. Higher level of interference by an RNA-DNA hybrid observed in the former assay may indicate that the reduction in sensitivity was due to the presence of viral RNA in the sample of pelleted virus. The ELOSA-RT assay was interfered with to a great extent than the non-RI RT assay by fetal bovine serum and thus may be unsuitable for measuring RT from HIV-1 in a culture supernatant.

Significance of human cytomegalovirus DNA detection in immunocompromised heart transplant patients

Peripheral blood samples (n= 1240), obtained at variable intervals from 483 heart transplantation (HTx patients under immunosuppressive therapy, and blood samples (n=1013) obtained upon blood donation from 1013 healthy anti-human cytomegalovirus (HCMV) positive blood donors, were tested for HCMV DNA by nested polymerase chain reaction (PCR). The detection limit of the nested PCR was determined to be less than 10 copies of the plasmid pRR 47, containing the HCMV immediate early gene. HCMV DNA was detected in 79 of 483 HTx patient (17%). To the contrary' HCMV DNA was only detected in 1 of 1013 anti-HCMV positive, healthy blood donors (0.1%). This PCR positive donor had recently contracted a primary HCMV infection. The rate of HCMV PCR positive immunosuppressed HTx patients in our study was lower than the rate of HCMV PCR positive healthy blood donors in previous reports in the literature. Blood samples (269 from 117 HTx patients) were assayed for HCMV DNA in peripheral blood leukocytes, HCMV DNA in plasma, and HCMV tegument protein 65 kDa (pp 65 antigen). Three laboratory diagnostic patterns were observed and related to clinical findings: (1) HCMV DNA only in leukocytes was observed in 26 patients, 7 of whom had HCMV disease, 5 of whom had graft rejection, and 14 of whom had no specific symptoms; (2) HCMV DNA both in leukocytes and in plasma (viremia) was observed in 3 patients, who were all symptomatic with HCMV disease; (3) HCMV DNA in leukocytes and in plasma (viremia) and pp 65 antigen were observed in 13 patients, all of whom were symptomatic (10 patients had HCMV disease, and 3 patients had graft rejection). A similar sequence of diagnostic patterns was observed in all symptomatic HCMV infections and reactivations in this study: HCMV DNA appeared first in peripheral blood leukocytes, then also in plasma, followed by pp 65 antigen detectable in peripheral blood leukocytes. Upon clinical recovery, these findings disappeared in reverse order. However, HCMV DNA remained detectable in peripheral blood leukocytes for several weeks. The detection of HCMV DNA in the peripheral blood is an exception, not the rule, even in severely immunosuppressed HTx patients. It indicates a pathological condition, albeit without clinical symptoms in some patients, and it is the earliest signal of HCMV replication. Of 42 patients in whom HCMV DNA was initially detected only in peripheral blood leukocytes, 16 patients progressed into viremia. Thus, HCMV-specific PCR performed on nucleic acid extracts from lysed peripheral blood is an appropriate method for the monitoring of HCMV infections in immunosuppressed HTx patients.

Bone allograft banking in South Australia

The South Australian Bone Bank had expanded to meet an increased demand for allograft bone. During a 5 year period from 1988 to 1992, 2361 allografts were harvested from 2146 living donors and 30 cadaveric donors. The allografts were screened by contemporary banking techniques which include a social history, donor serum tests for HIV-1, HIV-2, hepatitis B and C, syphilis serology, graft microbiology and histology. Grafts were irradiated with 25 kGy. The majority of grafts were used for arthroplasty or spinal surgery and 99 were used for tumour reconstruction. Of the donated grafts 336 were rejected by the bank. One donor was HIV-positive and two had false positive screens. There were seven donors with positive serology for hepatitis B, eight for hepatitis C and nine for syphilis. Twenty-seven grafts had positive cultures. Bone transplantation is the most frequent non-haematogenous allograft in South Australia and probably nationally. The low incidence of infectious viral disease in the donor population combined with an aggressive discard policy has ensured relative safety of the grafts. The frequency of graft rejection was similar to other bone banks but the incidence of HIV was lower.

Feline immunodeficiency virus replicates in salivary gland ductular epithelium during the initial phase of infection

Feline immunodeficiency virus (FIV) antigen was detected by immunochemistry in salivary glands of cats experimentally inoculated with West Australian isolate T91. Six cats were inoculated subcutaneously with 1.0 ml of tissue culture supernatant fluid from a feline T-lymphoblastoid cell line (MYA-1) infected with T91. FIV antigens were detected in the interlobular ducts of the salivary gland of cats infected with FIV 2, 4 and 6 weeks previously. FIV antigen was not detected in the salivary glands of three FIV negative cats and one naturally infected cat. Further, FIV antigen was located only in interlobular duct epithelial cells. The distribution of FIV in the interlobular ducts confirms the important role of salivary glands as a major reservoir of FIV in the early phase of infection and strengthens suggestions that the salivary route is an important mode of transmission of FIV.

When to perform the final HIV antibody test following possible exposure

The senior consultant and senior health adviser in all genitourinary medicine clinics in the UK were sent a questionnaire on HIV testing practice in seven clinical scenarios. For each scenario the recommended time interval between possible exposure and final HIV antibody test varied from a minimum of 3 months to a maximum of over 5 years. The results show 2 broad patterns: when the contact was not someone known to be HIV positive the commonest recommended time interval was 3 months; for a known exposure to HIV the commonest recommendation was 6 months. Only 16 out of the 151 clinics replying had a written policy setting out the interval to elapse between possible exposure to HIV and the final test for HIV antibodies. Variation of practice within clinics is less where written policies exist. Some staff in clinics are recommending inappropriately long intervals before the final HIV test.

Detection of human immunodeficiency virus type 1 proviral DNA by PCR using an electrochemiluminescence-tagged probe

We have developed a rapid, pseudohomogeneous assay for the detection of PCR amplicons, based on the use of electrochemiluminescence generated from a Tris-bipyridine ruthenium(II) label. PCR amplification of highly conserved human immunodeficiency virus type 1 (HIV-1) gag gene sequences was performed with SK38 and SK39 primers, the latter of which was 5' biotinylated. Post-PCR reaction mixtures were combined with 10(12) copies of the SK19 probe-Tris-bipyridine ruthenium(II) conjugate, denatured by heating at 100 degrees C for 5 min, and hybridized at 55 degrees C for an additional 15 min. Hybridization to the biotinylated strand of the amplified DNA was determined by the addition of streptavidin-conjugated magnetic particles and analyzed by using an Origen-1 electrochemiluminescence analyzer. Our results demonstrated a sensitivity of fewer than five copies of HIV-1 (pre-PCR), by using either purified plasmid DNA containing one complete copy of the HIV-1 cDNA genome or lysed, proteinase K-treated 8E5 cells as the starting material. In an evaluation of actual clinical specimens (peripheral blood monocytes from both healthy and HIV-1-infected children), the electrochemiluminescent detection assay correlated 100% with both our standard method (solution hybridization with a radiolabeled probe followed by polyacrylamide gel electrophoresis [PAGE] and autoradiography) and a commercial method (Roche Amplicor). The electrochemiluminescent method was substantially easier to perform than either the PAGE or microtiter plate assays and was considerable faster to perform than either of these alternative formats.

Detection of HIV-1 proviral sequences in lymphocytes using a qualitative polymerase chain reaction assay

The performance and clinical relevance of a qualitative PCR-based assay for the detection of HIV-1 DNA sequences in peripheral blood mononuclear cells (PBMCs) was evaluated by two different laboratories. Four hundred and one samples were obtained from 397 individuals from different risk populations. All blood donors tested had negative results; positive signals were obtained from all infected patients. HIV-1 DNA was detected in 3 of 17 infants born to seropositive mothers; Western blot indeterminate blood donors and exposed health-care workers had negative results. Our results demonstrate that this PCR assay provides both sensitive and specific results and is suitable for testing large numbers of samples and for rapid identification of HIV-1 infection.

P24 antigen detection, viral isolation, DNA-PCR and in vitro antibody production for the diagnosis of HIV-1 latent infection in heterosexual women at high risk for HIV-1 infection

INTRODUCTION

The report of the existence of at-risk seronegative subjects, latently infected with HIV-1 and producing "in vitro" HIV-1 specific antibodies, prompted the authors to evaluate extensively twenty-five heterosexual HIV-1 seronegative women at high risk for HIV-1 infection.

MATERIAL AND METHODS

The capability of peripheral blood mononuclear cells from such subjects to produce "in vitro" HIV-1 specific antibodies after pokeweed-mitogen stimulation, was studied. Silent HIV-1 infection was investigated by HIV-1 DNA PCR, viral isolation and serum p24 Ag detection at entry and after 6 and 12 months.

RESULTS

Three seroconversions took place within 12 months, but no HIV-1 infections were found in the absence of detectable serum anti HIV-1 antibodies, even in subjects who apparently produced such antibodies in vitro. The antibodies produced in vitro by the seronegative women studied appeared of narrow specificity, reacting mainly with gp 160/120 envelope glycoproteins.

CONCLUSIONS

A strong concordance was found between the serological status and the other markers for HIV-1 infection, suggesting that the phenomenon of HIV-1 "latent infection" is a very rare event, if it occurs at all. Seronegative women sexually exposed to the virus may produce in vitro anti HIV-1 antibodies of narrow specificity in the absence of other signs of infection and this phenomenon might be related to an anamnestic response to the virus.

Clearance of HIV infection in a perinatally infected infant

BACKGROUND

We describe a child who was identified shortly after birth as infected with the human immunodeficiency virus type 1 (HIV-1), but whose infection appears to have completely cleared. Asymptomatic HIV-1 infection was diagnosed in the mother during the fourth month of pregnancy. The infant was delivered vaginally at 36 weeks, received no blood products, and was not breast-fed.

METHODS AND RESULTS

HIV-1 was detected by culture of the infant's peripheral-blood mononuclear cells at 19 and 51 days of age. Plasma from the infant was also culture-positive for HIV-1 at 51 days of age by DNA polymerase chain reaction (PCR). Nucleotide-sequence analysis of HIV-1 DNA showed extremely close homology of the cultures obtained 32 days apart, and forensic markers of genetic identity for the two cultures were identical. Hence, inadvertent viral contamination or error in the collection of specimens was highly unlikely. At 12 months of age the infant was seronegative for HIV-1, and numerous subsequent cultures and tests by PCR have also been negative for HIV-1. The child is five years of age at this writing, is HIV-seronegative, and remains well, with normal growth and development and no laboratory or clinical evidence of HIV-1 infection.

CONCLUSIONS

The infant we describe was infected perinatally with HIV-1, but the infection subsequently cleared and the infant remained without detectable HIV-1 infection five years later.

Direct detection of proviral gag segment of human immunodeficiency virus in peripheral blood lymphocytes by colorimetric PCR assay as a clinical laboratory tool applied to different at-risk populations

We used a colorimetric polymerase chain reaction (PCR)-based assay in kit form to detect directly human immunodeficiency virus type 1 (HIV-1) proviral gag sequences in peripheral blood cells from 68 healthy blood donors, 51 subjects at risk for HIV infection, 122 patients with HIV-1 infection, 11 patients with indeterminate Western blot (immunoblot) results, 4 blood donors HIV-1 positive by enzyme immunoassay, and 13 children born to HIV-1-seropositive mothers. The results obtained in the blood donors and HIV-1-infected patients demonstrated the high degree of diagnostic specificity and sensitivity of the PCR method. HIV-1 infection was excluded in 10 of the 11 patients with indeterminate Western blot results and in all four enzyme immunoassay-positive blood donors. A diagnosis of HIV infection was ruled out by negative PCR results in 5 of 13 children from seropositive mothers, which excluded vertical transmission of the infection in these cases; these children were younger than 3 months and had positive serological results. Two at-risk patients with negative serological results had positive PCR results. All results were confirmed by conventional PCR. In conclusion, colorimetric PCR, which is commercially available in kit form, is an easy and reliable technique that can be used to detect proviral HIV-1 genomes in blood cells, and despite the limitations owing to HIV genome variability, it is useful in the clinical setting for the diagnosis of HIV infection in selected categories of patients.

Standardisation of primers and an algorithm for HIV-1 diagnostic PCR evaluated in patients harbouring strains of diverse geographical origin. The Belgian AIDS Reference Laboratories

Eight Belgian AIDS Reference Laboratories established a multicentre quality control to evaluate the performance of their diagnostic human immunodeficiency virus type 1 (HIV-1) DNA polymerase chain reaction (PCR). A set of Belgian and African HIV-1 seropositive and seronegative patient samples, collected in Belgium, and the British Medical Research Council (MRC) HIV-1 PCR reference reagent kit, containing plasmid HIV-1 DNA at several dilutions in human carrier DNA with appropriate negative controls, were tested by the laboratories. No false positive results were reported. All laboratories were able to detect one to two copies of HIV-1 DNA. Among the 17 Belgian and African HIV-1 seropositives, some laboratories reported up to four indeterminate results, mainly due to failure of the SK38-39, SK68-69 (Ou et al. (1988) Science 239, 295-297) and/or gag881-882 (Simmonds et al. (1990) J. Virol. 64, 864-872) primers and a poorly performing algorithm. Only the H1POL4235-4538 nested pol primer set, developed by one of the laboratories, correctly identified all the tested HIV-1 positive and negative samples. Consequently, the laboratories decided to evaluate these pol primers as a reference primer set and to standardise the testing algorithm. All laboratories achieved a sensitivity and specificity of 100% on testing 10 additional Belgian and African patient samples, when adapting a standardised algorithm based on three HIV-1 primer sets, one of which is the H1POL4235-4538 primer set.

Existing problems in the testing for infectious diseases

Current methods for testing donated blood for presence of infectious viral agents in the USA differ from those used in other countries because of the USA Food and Drug Administration's (FDA) control which inhibits rapid introduction of testing methods or improvements. Delays in FDA approval may occur because of concerns about methodology or the state of knowledge about the disease it is intended to detect as well as due to variability between manufacturers. Despite strict FDA control, testing problems continue to occur in the USA. No approved method detects infectious agents during the "window period," and variations in detection, i.e., false positives and false negatives (even with confirmatory testing), continue to occur. The effect of physical and chemical changes (e.g., various anticoagulants) on samples has not been thoroughly evaluated. Test performance problems include lapses in sample identification, failure to use routine laboratory controls, improper calculation and reporting of results, improper acceptance of test runs and failure to properly detect and retest samples when carryover from very reactive samples occurs. For these reasons, transfusion-related disease transmission continues to occur. The current USA emphasis on good manufacturing practices should provide continuous improvements.

Intravaginal inoculation of rhesus macaques with cell-free simian immunodeficiency virus results in persistent or transient viremia

The simian immunodeficiency virus (SIV)-rhesus macaque model of heterosexual human immunodeficiency virus transmission consists of atraumatic application of cell-free SIVmac onto the intact vaginal mucosa of mature female rhesus macaques. This procedure results in systemic infection, and eventually infected animals develop the clinical signs and pathologic changes of simian AIDS. To achieve 100% transmission with the virus stocks used to date, multiple intravaginal inoculations are required. The current titration study utilized two stocks of SIVmac and demonstrated that a single intravaginal dose of cell-free SIV can reliably produce infection in rhesus macaques. This study also demonstrated that some animals intravaginally inoculated with cell-free SIVmac develop transient viremia characterized by a limited ability to isolate virus from peripheral blood mononuclear cells and lymph node mononuclear cells and no seroconversion to SIV antigen. SIV could be isolated from the peripheral lymph nodes of transiently viremic animals only during periods of viremia and not at times when SIV was not detected in circulating mononuclear cells. Thus, peripheral lymphoid tissues were not reservoirs of infection in the transiently viremic animals. Taken together, these results suggest either that the SIV infection was cleared in the transiently viremic animals or that SIV infection is limited to a compartment of the genital mucosal immune system that cannot be assessed by monitoring SIV infection in peripheral blood mononuclear cells and peripheral lymphoid tissue.

Molecular methods: applications for clinical infectious diseases

The application of molecular biology to microbiology has led to a surge of new information about most infectious microorganisms, the pathogenesis of the infections they cause, and the specific microbial antigens involved in the immune response to these infections. The simultaneous application of the same techniques to diagnosis and epidemiology has also shown great promise, but these developments have not yet had a major effect on the routine practice of medicine. For some purposes, direct probe tests perform as well as other available methods. However, for most infections, these methods have not been proven sufficiently sensitive. The latest generation of highly sensitive diagnostics based on the polymerase chain reaction will overcome this technical obstacle and may revolutionize the management of many infections. Difficulties inherent in performing these tests will require special procedures and training in clinical laboratories to ensure that they are performed reliably. Nucleic acid-based methods for epidemiologic typing of microorganisms and for identification of noncultivatable pathogens are particularly useful for analysis of poorly cultivatable, dangerous, or otherwise untypeable microorganisms.

Reference preparations in the standardisation of HIV-1 PCR--an international collaborative study

Following the recent developments in diagnostic polymerase chain reaction (PCR) technology, we have assessed a set of HIV-1 DNA reference standards using the first commercial diagnostic test kit for the detection of HIV-1 (Amplicor, Roche) in an international collaborative study. Nineteen laboratories in 11 countries analysed a set of ten (re-coded) HIV-1 DNA reference standards, whose performance had been validated in a previous collaborative study (Bootman and Kitchin, 1992). Results from the current study show that, using the diagnostic kit, 84% of laboratories (16/19) obtained correct diagnoses for all ten test samples. One additional laboratory failed only to detect the sample containing ten copies of target template. Test results from the remaining two laboratories were declared void in accordance with the Amplicor quality control guidelines.

Polymerase chain reaction detection of human immunodeficiency virus DNA in human periradicular lesions

Human immunodeficiency virus (HIV) has been previously reported to be present in the dental pulp of a patient with AIDS. The present report investigated the feasibility of polymerase chain reaction (PCR) amplification to detect the HIV proviral DNA in cells from periradicular lesions from an HIV-positive patient. The standard PCR amplification with 30 cycles and the nested PCR consisting of two 25-cycle amplifications were used. Samples from each reaction were separated by nondenaturing polyacrylamide gel electrophoresis and stained with ethidium bromide for visualization. Gels were electroblotted to nylon membranes, which were then fixed, denatured, and dried. Membranes were hybridized to specific radioactive oligonucleotide probes and placed next to Kodak XAR film for visualization of the HIV-specific bands. No evidence of HIV-specific reaction was observed in cells (negative control) or in two periradicular lesions from two HIV-negative patients. The ethidium bromide strains revealed that PCR amplification of DNA extracts from two lesions from the HIV-positive patient yielded PCR bands (with both primer pairs) which corresponded to HIV-specific bands of the expected size.

Detection of human immunodeficiency virus-1 nucleic acid on inactivated filter paper disks by polymerase chain reaction and microtiter plate assay

Human immunodeficiency virus type 1 (HIV-1) in cultured cells, peripheral blood samples and sera were adsorbed on filter paper disks and inactivated by heat or ethanol. Two procedures, the polymerase chain reaction (PCR) and microtiter plate assay (HMPA) were used to detect the nucleic acid. The sensitivity after different heat treatments with nested PCR for HIV-1 DNA (or nested reverse transcription-PCR for HIV-1 RNA) was identical regardless of whether the samples were examined immediately or one month later. Inactivation by ethanol treatment resulted in a slight loss of sensitivity. The HMPA proved to be as reliable and specific as the conventional PCR technique. We conclude that the heat-treated filter paper disk assay is suitable for identifying HIV nucleic acid in clinical samples sent to the laboratory from a distance, e.g. in an envelope.

Donor insemination and human immunodeficiency virus: a risk/benefit analysis

In 1988 the American Fertility Society revised its guidelines for the use of semen in donor insemination by stating that "the use of fresh semen for donor insemination is no longer warranted." Although the consequences of this recommendation include an approximate doubling of the patient's cost of treatment, a 50% reduction in both cycle fecundity and 3-month life-table pregnancy rates, a reduction in the number of pregnancies because of patient dropout, and an ethically troubling increase in physician income as a direct result of the diminished efficacy of treatment, an analysis of the risk of transmission of human immunodeficiency virus through donor insemination has not been presented. All available data suggest that neither safety nor efficacy need be sacrificed in the current practice of donor insemination by offering patients the choice of appropriately screened fresh or frozen sperm.

Capillary electrophoresis: detection of hybridization between synthetic oligonucleotides and HIV-1 genomic DNA amplified by polymerase-chain reaction

The polymerase chain reaction (PCR) is one of the most efficient techniques for measuring the viral load of HIV-infected samples. Determination of the specificity of PCR products is usually based on Southern blotting and hybridization of the amplified DNA to radioactive oligonucleotide probes specific for sequences comprised between the PCR primers. The recent introduction of capillary electrophoresis (CE) for identification of HIV-1 and HTLV-I PCR products appears interesting in light of its reproducibility, sensitivity and because it is fast and suitable for detection of DNA/DNA and DNA/RNA hybrids. We demonstrate that specific hybridization of a HIV-1 oligonucleotide probe to single-stranded DNA obtained by unbalanced PCR is detectable by capillary electrophoresis. This enabled us the application of a one-step, non-radioactive protocol to demonstrate the specificity of amplification of HIV-1 genomic sequences by PCR. This procedure is simple, reproducible and is suggested as an integral part of automated diagnostic systems based on the use of laboratory work stations for DNA isolation, preparation of PCR reactions and analysis of PCR products.

The acquired immune deficiency syndrome: an overview for the emergency physician, Part 1

The acquired immune deficiency syndrome (AIDS) was recognized as a distinct entity in 1981. It began as a medical curiosity affecting only several dozen individuals in a restricted segment of the U.S. population. In the 12 years since its description, AIDS has become a pandemic affecting tens of millions with cases reported from all major countries. The illness is caused by a retrovirus, termed human immunodeficiency virus (HIV). It is a blood-borne disease with sexual, parenteral, and perinatal modes of transmission. Infection with the virus can be determined by a number of serologic techniques as well as viral culture. The pathophysiology of illness is incompletely understood, but is in large part related to destruction of helper, CD4 lymphocytes. This results in immune dysfunction and the development of a variety of opportunistic infections and malignancies. A great deal has been learned over the last decade, with important advances in treatment. Zidovudine (AZT) remains the most important agent in slowing progression of the disease and has resulted in prolonging survival. All organ systems can be affected by HIV, and many clinical manifestations are protein. Fever, weight loss, and diarrhea are often encountered general symptoms. The skin is frequently involved, with Kaposi's Sarcoma the most common malignancy and a variety of fungi and viruses the most frequent cause of infection. The lung is involved in the majority of patients, with Pneumocystis Carinii (PCP) and mycobacteria emerging as the most important pathogens. A variety of treatments have demonstrated efficacy for PCP. The risk of PCP is related to the decay in CD4 lymphocytes so that prophylactic treatment is recommended when CD4 counts fall below 200. Mycobacterial infection with multiresistant organisms has complicated the management of these infections and poses new risks to health care workers. Part 1 of this two-part series on AIDS discusses the pathophysiology and clinical expression, epidemiology, laboratory testing, and the general clinical manifestations of AIDS, as well as dermatologic, pulmonary, and cardiac symptoms. Part 2 will discuss the gastrointestinal, neurologic, and ocular symptoms, as well as the treatment and management of the AIDS patient.

CD4+ lymphocytopenia due to common variable immunodeficiency mimicking AIDS

There are an increasing number of published reports of patients with acquired immunodeficiency without evidence of HIV infection, who have been labelled as having "idiopathic CD4+ lymphocytopenia". The case is reported here of a young man who presented with Pneumocystis carinii pneumonia (PCP), CD4+ lymphopenia, and hypogammaglobulinaemia attributable to common variable immunodeficiency (CVID). The presentation of this condition, with many of the clinical and laboratory features of AIDS, highlights CVID as a diagnosis to be considered in the differential diagnosis of CD4+ lymphocytopenia.

Reporting recent sexual practices: gay men's disclosure of HIV risk by questionnaire and interview

AIDS-related research relies primarily on self-reports of sexual practices. Therefore, determining which data collection methods yield more candid information is critical. Data from a study of gay men's sexual adaptations to the AIDS epidemic provided an opportunity to explore the congruence of data collected using a self-administered questionnaire with data from an unstructured face-to-face interview designed to facilitate report of sexual risk behavior. We examined (i) the concordance of questionnaire and unstructured interview risk ratings when the two data sources are scored for the same 16 sexual behaviors; (ii) the concordance of questionnaire ratings and ratings obtained when all information on recent sexual practices available from the unstructured interview is considered; (iii) the relationship between serostatus and both concordance patterns between methods; and (iv) the difference by serostatus of reported risk level within method. Riskiest behaviors were reported on the questionnaire for all serostatus groups. Riskier behaviors were more likely to be reported on the questionnaire while more characteristic, safer behaviors were discussed in interview, regardless of HIV serostatus. The advantages of a combined methods--questionnaire/interview--strategy for sexual practice research are discussed.

Detection of human immunodeficiency virus type 1 by PCR before seroconversion in high-risk individuals who remain seronegative for prolonged periods

HIV-1 seronegative patients at high risk for HIV infection were followed up. In 1990 PCR was positive for HIV DNA sequences in samples of 17 seronegative patients who continued to report for surveillance of HIV infection. There was clear evidence of seroconversion in four of these 17 seronegative patients, while in one patient an indeterminate result for HIV was repeatedly obtained in different samples. The other 12 patients continue to be seronegative without any evidence of HIV infection except the presence of provirus in peripheral blood mononuclear cells. It is important to apply the PCR technique together with tests to detect other virological and immunological markers, in order to identify seronegative carriers and thus avoid HIV transmission by them.

Human immunodeficiency virus (HIV) nef-specific cytotoxic T lymphocytes in noninfected heterosexual contact of HIV-infected patients

We report on the detection of HIV-specific cytotoxic T lymphocytes (CTL) among 23 regular partners of HIV-infected individuals. 15 of the 46 individuals enrolled in the study were positive for HLA-A2.1 typing. Among the 23 contacts studied, 7 were seropositive and 16 were seronegative on repeated tests. None of the 16 seronegative contacts were positive for p24 antigenemia nor were they positive by the lymphocytes coculture assay, although, in two instances HIV-1 DNA could be detected by PCR (in one case using a gag SK 38/39 primer, and in the other using a primer for the pol P3/P4 primer). These two individuals remained seronegative for 18 and 36 mo, respectively. HIV-specific cytotoxicity was performed in the 15 HLA-A2.1 subjects (7 indexes, 2 seropositive contacts, and 6 seronegative contacts) and in 4 HLA-matched HIV negative donors. CTL specific for env, gag, or nef proteins could not be detected in unstimulated bulk cultures of peripheral blood lymphocytes in any of the six seronegative contacts. However, using a limiting dilution assay we found an usually high frequency of HIV nef-specific CTL precursors (CTLp) for HIV env and gag was very similar to that observed in seronegative HLA-matched healthy donors. Because no presence of HIV could be demonstrated in these individuals, these findings argue against the possibility of a silent HIV infection and suggest that a CTL response against nef may be involved in a rapid and effective clearance of the virus after sexual exposure.

Polymerase chain reaction: basic concepts and clinical applications in dermatology

The polymerase chain reaction (PCR) has been extensively used in basic science research, and the clinical potential of PCR is only now beginning to be realized. The PCR is based on the fundamental DNA replication process that occurs in every living cell. PCR is essentially an in vitro adaptation of the in vivo DNA copying process. Because PCR is so efficient at amplifying even picogram quantities of DNA, contamination with even trace amounts of nucleic acids can lead to the generation of unwanted DNA sequences and false-positive test results. Despite this, there has been rapid growth in the use of PCR in biomedical research and clinical diagnostics. PCR is the most sensitive test for herpes simplex virus, varicella-zoster virus, and human papillomavirus infections. Other diagnostic uses, including tests for genetic diseases, cancers, and other infectious diseases, are evolving.

Microplate-based DNA hybridization assays for detection of human retroviral gene sequences

Nonisotopic, microwell-based DNA hybridization assays for the specific detection of human immunodeficiency virus type 1 (HIV-1) gag, human T-cell lymphotropic virus type I (HTLV-I) pol, and HTLV-II pol DNA sequences were evaluated. The performances of these detection kits (Gene Detective enzyme oligonucleotide assays; Cellular Products, Inc., Buffalo, N.Y.) were assessed by using clinical samples whose infection status were established by amplification by PCR and then liquid hybridization detection by using virus-specific probes. Peripheral blood mononuclear cell lysates from 59 HIV-1-, 35 HTLV-I-, and 19 HTLV-II-infected individuals and from 15 healthy blood donors were used as substrates for PCR amplification. The results of the study demonstrated a clinical sensitivity of 100%. In addition, the enzyme oligonucleotide assays were able to detect 1 to 10 proviral copies subsequent to PCR amplification, indicating an analytical sensitivity comparable to that of liquid hybridization.

AIDS and the neurosurgeon--an update

Over the past decade, acquired immunodeficiency syndrome (AIDS) has become the leading public health crisis in the United States, Western Europe, and Africa. Despite improvements in the diagnosis and treatment of AIDS-related disorders, the number of people infected with the human immunodeficiency virus (HIV-1) continues to grow, requiring a greater proportion of limited financial, medical, and human resources. Since nearly one half of symptomatic AIDS patients have neuropathologic disease, clinicians must be aware of the myriad neurologic manifestations of AIDS and use the most effective methods to diagnose and treat them. The work-up of the AIDS patient with neurologic symptoms includes a careful history and physical examination, laboratory studies, and radiographic imaging. Gadolinium-enhanced magnetic resonance (MR) imaging has become the radiographic screening study of choice. MR imaging can be used to predict which patients should undergo stereotactic biopsy before an empirical trial of antitoxoplasmosis therapy. Any patient with a mass lesion that does not respond to empirical therapy for toxoplasmosis should also undergo biopsy to exclude another treatable disorder. While the number of patients with neurological complications can be expected to increase in the near future, better imaging techniques may obviate the need for biopsy in many of these patients. The increasing threat of HIV-1 infection in the workplace requires meticulous care both in and out of the operating room to minimize accidental exposure of health-care workers.

Absence of prolonged immunosilent infection with human immunodeficiency virus in individuals with high-risk behaviors

PURPOSE

The presence in some individuals of a prolonged phase of infection with human immunodeficiency virus type 1 (HIV-1) before seroconversion remains controversial. This study was undertaken to determine with a sensitive in vitro amplification technique, the polymerase chain reaction (PCR), whether seronegative individuals with high-risk behaviors could harbor HIV-1 sequences in their peripheral blood mononuclear cells (PBMCs) and remain seronegative for more than 6 months.

PATIENTS AND METHODS

Seronegative individuals who engaged in unprotected anogenital intercourse with HIV-1-infected partners or with more than 10 individuals per year, and seronegative individuals who shared needles with seropositive partners, were recruited prospectively over 18 months. HIV-1 DNA and RNA sequences were detected in PBMCs of these individuals with three PCR assays using SK38/SK39, SK145/SK431, and SK68/SK69. Seronegative but PCR-positive patients were also evaluated with p24 antigen capture assay, radioimmunoprecipitation assay, and Western blot. The latter patients were followed prospectively to reproduce PCR-positive results and monitor serologic responses.

RESULTS

Sixty-one men and 18 women, with an average age of 34.1 +/- 7.6 years, were recruited: 56 were homosexual men, 18 were heterosexual women, and 5 were heterosexual men. Amplification reactions for HIV-1 of 104 PBMC specimens from 79 patients with negative or indeterminate serologies revealed that 4 patients (5.1%) were positive with PCR for HIV-1 DNA and RNA at the time of enrollment. Positive amplification reactions could not be reproduced in prospective samples for one patient. The analysis of a variable human genomic locus in this patient's PBMCs demonstrated that the first PCR-positive sample and following PCR-negative samples originated from different patients, suggesting a specimen mix-up. Two of the three PCR-positive seronegative patients had symptoms suggestive of acute retroviral disease. Sera from all three patients contained p24 antigen. Two patients seroconverted within 1 month whereas one patient could not be followed prospectively.

CONCLUSION

Prolonged infection with HIV-1 without seroconversion was not found in our population of patients at very high risk for HIV-1 infection. All PCR-positive patients seroconverted in less than 1 month.

Amplification and detection of a single molecule of human immunodeficiency virus RNA

Detection of plasma viremia in human immunodeficiency virus type 1 (HIV-1)-infected people is indispensable for the diagnosis of seronegative infection as well as for the evaluation of virus activities in vivo. The direct detection of HIV-1 RNA in circulation has been performed by means of reverse transcription followed by polymerase chain reaction (RT-PCR). As an attempt to establish a highly sensitive assay, we evaluated the effects of two-step amplification with nested primers and double priming of reverse transcription on the sensitivity of RT-PCR. The sensitivity of two-step amplification was 100 times higher than that of one-step amplification. The double priming of reverse transcription further increased the sensitivity of the following two-step amplification 100 times, which appeared to be enough to detect HIV-1 RNA from as little as a 2.2 x 10(-4) TCID50 unit equivalent of culture supernatant of HIV-1-infected cells and a single molecule of HIV-1 gag complementary RNA synthesized by in vitro transcription. By use of this most sensitive assay, we successfully detected HIV-1 RNA in serum or plasma from all 22 patients with acquired immune deficiency syndrome (AIDS) or AIDS-related complex (ARC) and 13 out of 14 untreated asymptomatic carriers. Of 43 asymptomatic carriers under the treatment with interferon-alpha or azidothymidine, 17 cases showed negative results, indicating that the virus activity was suppressed by the therapeutics. We also noted the inhibitory effect of heparin on RT-PCR.

Eye protection for the vascular surgeon

Contamination occurring during vascular surgery was studied prospectively using a surgical mask incorporating a Splashguard visor. Over a 16-week period 78 vascular procedures were included; 44 were of < 2 h duration and 34 were of > or = 2 h. Contamination on both mask and visor from blood spots was recorded at the end of each procedure. Overall, 51 per cent of principal surgeons' visors were contaminated, with contamination of the mask itself in 32 per cent. When two surgeons were operating the contamination rate for the second was also high: 36 per cent for the visor and 42 per cent for the mask. Assistants had a contamination rate of 36 per cent for the visor and 13 per cent for the mask. The lowest rate of contamination occurred for the visor and mask of the scrub nurse, 10 and 4 per cent respectively. For emergency procedures the duration of operation had no influence on the frequency of contamination. However, for the principal surgeon elective operations of < 2 h duration were less likely to involve contamination than those of > or = 2 h (P < 0.035). Blood contamination of visors and masks is common in vascular surgery but rarely appreciated by the surgeon. Routine eye protection should be considered in vascular surgery, in particular for emergency and prolonged elective procedures.