Controlling HIV epidemics among injection drug users: eight years of Cross-Border HIV prevention interventions in Vietnam and China.

INTRODUCTION: HIV in Vietnam and Southern China is driven by injection drug use. We have implemented HIV prevention interventions for IDUs since 2002-2003 in Lang Son and Ha Giang Provinces, Vietnam and Ning Ming County (Guangxi), China. METHODS: Interventions provide peer education and needle/syringe distribution. Evaluation employed serial cross-sectional surveys of IDUs 26 waves from 2002 to 2011, including interviews and HIV testing. Outcomes were HIV risk behaviors, HIV prevalence and incidence. HIV incidence estimation used two methods: 1) among new injectors from prevalence data; and 2) a capture enzyme immunoassay (BED testing) on all HIV+ samples. RESULTS: We found significant declines in drug-related risk behaviors and sharp reductions in HIV prevalence among IDUs (Lang Son from 46% to 23% [p<0.001], Ning Ming: from 17% to 11% [p = 0.003], and Ha Giang: from 51% to 18% [p<0.001]), reductions not experienced in other provinces without such interventions. There were significant declines in HIV incidence to low levels among new injectors through 36-48 months, then some rebound, particularly in Ning Ming, but BED-based estimates revealed significant reductions in incidence through 96 months. DISCUSSION: This is one of the longest studies of HIV prevention among IDUs in Asia. The rebound in incidence among new injectors may reflect sexual transmission. BED-based estimates may overstate incidence (because of false-recent results in patients with long-term infection or on ARV treatment) but adjustment for false-recent results and survey responses on duration of infection generally confirm BED-based incidence trends. Combined trends from the two estimation methods show sharp declines in incidence to low levels. The significant downward trends in all primary outcome measures indicate that the Cross-Border interventions played an important role in bringing HIV epidemics among IDUs under control. The Cross-Border project offers a model of HIV prevention for IDUs that should be considered for large-scale replication.

Evaluation of an alternative HIV diagnostic algorithm using specimens from seroconversion panels and persons with established HIV infections.

BACKGROUND: The current algorithm for HIV diagnosis in the US involves screening with an immunoassay (IA) and supplemental testing with Western blot (WB) or immunofluorescence assay. Because of existence of more sensitive and specific FDA-approved assays that would also reduce the cost and turn-around time of testing compared to WB, several alternative algorithms have been evaluated. Recently, an alternative algorithm using a sensitive 3rd or 4th generation IA followed by an HIV-1 and HIV-2 discriminatory supplemental test on the initial IA-positive specimens was proposed. Concordant positive results indicate HIV-positive specimens and discordant results are resolved by nucleic acid amplification testing (NAAT). OBJECTIVES: To evaluate the sensitivity of assays during acute HIV infection and the performance of the current and an alternative algorithm using samples from HIV-1 seroconversion panels and persons with established HIV infections. STUDY DESIGN: To evaluate the algorithms in early infections, 26 HIV-1 seroconverters from the US were tested with three 3rd generation and one 4th generation IA, six rapid tests (RTs), one NAAT, and WB. Sensitivity and specificity of the algorithms were calculated by testing an additional 416 HIV-positive and 414 uninfected control samples with one 3rd generation and one 4th generation IA, four RTs, one NAAT, and WB. RESULTS: The individual assays evaluated became positive 5 (RT) to 26 days (NAAT) before WB was positive. Among seroconverters, the alternative algorithm detected significantly more infections than the current algorithm (103-134 versus 56, p<0.0001). Furthermore, the use of a 4th generation IA instead of a 3rd generation assay as the screen resulted in significantly higher detection of acute infections (p<0.0001). In contrast, the algorithms performed equally among specimens from established HIV-1 infections. CONCLUSIONS: This study demonstrated improved sensitivity of the alternative algorithm for detecting acute HIV-1 infections, while maintaining the ability to accurately detect established HIV-1 infections. Early detection is important as individuals can be highly infectious during acute infection. In addition, the alternative algorithm should reduce turn-around time by using a RT as the supplemental test has the potential to increase the number of test results returned.

Assessment of BED HIV-1 incidence assay in seroconverter cohorts: effect of individuals with long-term infection and importance of stable incidence.

BACKGROUND: Performance of the BED assay in estimating HIV-1 incidence has previously been evaluated by using longitudinal specimens from persons with incident HIV infections, but questions remain about its accuracy. We sought to assess its performance in three longitudinal cohorts from Thailand where HIV-1 CRF01_AE and subtype B' dominate the epidemic. DESIGN: BED testing was conducted in two longitudinal cohorts with only incident infections (a military conscript cohort and an injection drug user cohort) and in one longitudinal cohort (an HIV-1 vaccine efficacy trial cohort) that also included long-term infections. METHODS: Incidence estimates were generated conventionally (based on the number of annual serocoversions) and by using BED test results in the three cohorts. Adjusted incidence was calculated where appropriate. RESULTS: For each longitudinal cohort the BED incidence estimates and the conventional incidence estimates were similar when only newly infected persons were tested, whether infected with CRF01_AE or subtype B'. When the analysis included persons with long-term infections (to mimic a true cross-sectional cohort), BED incidence estimates were higher, although not significantly, than the conventional incidence estimates. After adjustment, the BED incidence estimates were closer to the conventional incidence estimates. When the conventional incidence varied over time, as in the early phase of the injection drug user cohort, the difference between the two estimates increased, but not significantly. CONCLUSIONS: Evaluation of the performance of incidence assays requires the inclusion of a substantial number of cohort-derived specimens from individuals with long-term HIV infection and, ideally, the use of cohorts in which incidence remained stable. Appropriate adjustments of the BED incidence estimates generate estimates similar to those generated conventionally.

Determination of mean recency period for estimation of HIV type 1 Incidence with the BED-capture EIA in persons infected with diverse subtypes.

The IgG capture BED enzyme immunoassay (BED-CEIA) was developed to detect recent HIV-1 infection for the estimation of HIV-1 incidence from cross-sectional specimens. The mean time interval between seroconversion and reaching a specified assay cutoff value [referred to here as the mean recency period (ω)], an important parameter for incidence estimation, is determined for some HIV-1 subtypes, but testing in more cohorts and new statistical methods suggest the need for a revised estimation of ω in different subtypes. A total of 2927 longitudinal specimens from 756 persons with incident HIV infections who had been enrolled in 17 cohort studies was tested by the BED-CEIA. The ω was determined using two statistical approaches: (1) linear mixed effects regression (ω(1)) and (2) a nonparametric survival method (ω(2)). Recency periods varied among individuals and by population. At an OD-n cutoff of 0.8, ω(1) was 176 days (95% CL 164-188 days) whereas ω(2) was 162 days (95% CL 152-172 days) when using a comparable subset of specimens (13 cohorts). When method 2 was applied to all available data (17 cohorts), ω(2) ranged from 127 days (Thai AE) to 236 days (subtypes AG, AD) with an overall ω(2) of 197 days (95% CL 173-220). About 70% of individuals reached a threshold OD-n of 0.8 by 197 days (mean ω) and 95% of people reached 0.8 OD-n by 480 days. The determination of ω with more data and new methodology suggests that ω of the BED-CEIA varies between different subtypes and/or populations. These estimates for ω may affect incidence estimates in various studies.

Alternative algorithms for human immunodeficiency virus infection diagnosis using tests that are licensed in the United States.

Serodiagnosis of human immunodeficiency virus (HIV) infection in the United States has traditionally relied on a sequential two-test algorithm: an initial screen with an enzyme immunoassay (EIA) and reflex testing of EIA-reactive specimens with a more specific supplemental test such as Western blotting or immunofluorescence. The supplemental tests are tedious, subjective, and expensive. In addition, there have been major improvements in the performance and accuracy of the EIA tests as well as the introduction of rapid serologic tests (RT) and HIV nucleic acid amplification tests (NAAT). Related to these improvements is the possibility that alternative algorithms using combinations of currently approved HIV tests may function as well as if not better than the current algorithm, with more flexibility, improved accuracy, and lower cost. To this end, we evaluated the performance of 12 currently licensed tests and 1 in-house HIV test (6 EIA, 4 RT, and 3 NAAT) on panels of plasma samples from HIV-infected (n = 621 HIV type 1 [HIV-1] and 34 HIV-2) and uninfected (n = 513) people and of sequential specimens from people early in seroconversion (183 specimens from 15 patients). Test combinations were analyzed in two dual-test (sensitivity-optimized and specificity-optimized) algorithms and in a three-test (tie-breaking) algorithm, and performance was compared to the conventional algorithm. The results indicate that alternative algorithm strategies with currently licensed tests compare favorably with the conventional algorithm in detecting and confirming established HIV infection. Furthermore, there was a lower frequency of discordant or indeterminate results that require follow-up testing, and there was improved detection of early infection.

Improved HIV-1 incidence estimates using the BED capture enzyme immunoassay.

OBJECTIVE: To validate the BED capture enzyme immunoassay for HIV-1 subtype C and to derive adjustments facilitating estimation of HIV-1 incidence from cross-sectional surveys. DESIGN: Laboratory analysis of archived plasma samples collected in Zimbabwe. METHODS: Serial plasma samples from 85 women who seroconverted to HIV-1 during the postpartum year were assayed by BED and used to estimate the window period between seroconversion and the attainment of a specified BED absorbance. HIV-1 incidences for the year prior to recruitment and for the postpartum year were calculated by applying the BED technique to HIV-1-positive samples collected at baseline and at 12 months. RESULTS: The mean window for an absorbance cut-off of 0.8 was 187 days. Among women who were HIV-1 positive at baseline and retested at 12 months, a proportion (epsilon) 5.2% (142/2749) had a BED absorbance < 0.8 at 12 months and were falsely identified as recent seroconverters. Consequently, the estimated BED annual incidence at 12 months postpartum (7.6%) was 2.2 times the contemporary prospective estimate. BED incidence adjusted for epsilon was 3.5% [95% confidence interval (CI), 2.6-4.5], close to the 3.4% estimated prospectively. Adjusted BED incidence at baseline was 6.0% (95% CI, 5.2-6.9) and, like the prospective estimates, declined with maternal age. Unadjusted BED incidence estimates were largely independent of age; the pooled estimate was 58% higher than adjusted incidence. CONCLUSION: The BED method can be used in an African setting, but further estimates of epsilon and of the window period are required, using large samples in a variety of circumstances, before its general utility can be gauged.

Use of computer assisted and interactive cognitive training programmes with moderate to severely demented individuals: a preliminary study.

The purpose of this study was to investigate the potential effects of interactive cognitive training and computer-assisted programmes in reducing decline in older adults with dementia. The primary goal of this programme was to maintain participants' level of cognitive function. This study included six moderately to severely demented older adults living in a secured memory-impairment unit within an assisted living community. The participants were assessed with neuropsychological tests prior to, and immediately following, an intensive six-week cognitive training programme. The results showed that the participants improved significantly on measures of overall cognitive function, including short-term memory and cognitive failures. Caregiver reports also indicated significant improvement in the participants' behaviour signs and socialization. Additionally, these participants did not demonstrate significant decline on any of the measures from pre-test to post-test levels. This preliminary study indicates that a combined interactive cognitive training and individual-based computer training programme may effectively reduce decline and even improve some cognitive and behavioural functioning in demented older adults. A follow-up of the participants after four weeks of no training revealed some decline in some of the cognitive and behavioural measures, thus supporting the effectiveness of the training programmes.

Chimeric multiple antigenic peptides for simultaneous detection of specific antibodies to HIV-1 groups M, N, O, and HIV-2.

Synthetic peptides have frequently replaced the more costly recombinant proteins or viral lysates as the antigens of choice for detection of antibodies to human immunodeficiency viruses. However, development of an assay that is sensitive to all the types and groups of HIV, including the divergent strains of HIV-1 group O, group N, and HIV-2, would require many peptides derived from different types and groups of HIV. Combining multiple peptide antigens may reduce the analytical sensitivity of the individual peptide due to the competition for binding to the solid surface when used in an enzyme immunoassay format. In this study, we developed and evaluated two chimeric multiple antigenic peptides (CMAP) for simultaneous detection of specific antibodies to HIV-1 groups M, N, O, and HIV-2. Both CMAPs correctly identified 304 known HIV positive serum or plasma specimens (260 HIV-1 group M of varying subtypes, 3 group O, and 41 HIV-2) and one chimpanzee serum specimen (group N) and all 66 known HIV negative specimens. CMAP performance was superior to the corresponding individual linear peptides or a linear peptide mixture. The results indicate that CMAPs are useful for the development of highly sensitive and specific assays for the detection of infections caused by HIV-1, including group M, N, and O, and HIV-2.

Comparison of HIV type 1 incidence observed during longitudinal follow-up with incidence estimated by cross-sectional analysis using the BED capture enzyme immunoassay.

The BED capture enzyme immunoassay (BED CEIA) for recent infection was developed for the estimation of HIV-1 incidence in a population from a single cross-sectional survey. To evaluate performance, we applied the assay to specimen sets obtained from a longitudinal cohort study, the AIDSVAX B/B vaccine trial, in which there was an independent and conventional measure of observed incidence. The BED CEIA was performed on specimens obtained during follow-up for seroconversion conducted every 6 months for 3 years. There was excellent agreement between the observed and BED-estimated incidence for all the intervals. The cumulative, annualized incidence observed in the cohort was 3.10 new infections per 100 person-years (95% CI, 2.57-3.63). The corresponding BED-estimated incidence was 2.91 (2.30-3.53). We also estimated the effect of varied prevalence on a fixed incidence. Because some specimens from persons with longer-term infection are classified as recent by the assay, this can inflate the incidence estimate. We quantify this effect and discuss potential mitigation by excluding certain specimens on clinical grounds, by relying on trend differences rather than absolute incidence estimates, by secondary confirmatory testing, or by analytic adjustments for misclassification. Cross-sectional HIV incidence estimation circumvents many of the drawbacks associated with longitudinal cohort studies, but there are test-specific limitations that should be considered in the design of population surveys.

Surveillance for HIV-1 incidence using tests for recent infection in resource-constrained countries.

Over the past few years, several assays have been developed for the purpose of estimating HIV-1 incidence from cross-sectional population surveys. The tests detect features of the evolving virological or immunological response to HIV-1 infection that distinguish recent from established infection. Surveillance programmes that collect specimens from population surveys for HIV-1 prevalence can apply some of these tests to the same specimen sets to estimate incidence. We describe these tests and discuss the principle and strategy for implementation of a testing programme for recent infection in surveillance settings. Test-specific prerequisites, such as calibration, validation, and quality assurance, and other test-specific performance characteristics that may influence interpretation, epidemiological considerations that may guide application, and practical operational considerations for implementation in surveillance settings are considered. When properly and judiciously applied, the capacity to estimate incidence from existing programmes that conduct surveillance for prevalent HIV-1 infection will enhance the capacity for more precise and timely analysis of the dynamics of the epidemic and the effectiveness of public health interventions.

Application of laboratory methods for estimation of HIV-1 incidence.

Estimating HIV-1 incidence (rate of new HIV-1 infections) in various populations is important to understand the current status of transmission dynamics, identify high-risk populations, monitor prevention efforts and target resources on programmes that are most effective in reducing transmissions. Recent developments in our ability to detect and distinguish recent and longterm HIV-1 infections using laboratory tests have made the measurement of HIV-1 incidence realistic and practical. These approaches most commonly rely on the properties of early HIV-1 antibodies after seroconversion as characterized by their levels, antibody avidity/affinity or antibody classes/subclasses or epitope specificity. The sensitive/less-sensitive testing strategy provided simple laboratory tools to detect recent seroconversion in a cross-sectional population. These assays are based on differences in antibody titres in recent versus long-term infections and have been used for sometime for estimating population incidence. However, recent work demonstrated limitations of this approach which included subtype-dependent performance and significant variability of "window periods", precluding its use in many areas of the world. Recently an IgG-Capture BED-EIA was developed in our laboratory which detects the increasing HIV-IgG as proportion of total IgG following seroconversion and can be used to detect recent seroconversion. The format of the assay, which includes a multi-subtype derived antigen, allows high consistency and similar "window periods" in different subtypes. This assay is now available commercially and is made specifically for population estimates of HIV-1 incidence. Due to the presence of divergent HIV-1 subtypes and the rapidly expanding HIV epidemic, it is important that the method selected is robust, performs similarly in different subtypes and is widely applicable for meaningful incidence estimates, trend analysis and comparison between populations.

Performance characteristics of the immunoglobulin G-capture BED-enzyme immunoassay, an assay to detect recent human immunodeficiency virus type 1 seroconversion.

Recently, we developed an immunoglobulin G (IgG)-capture BED-enzyme immunoassay (BED-CEIA) to identify recent human immunodeficiency virus (HIV) type 1 (HIV-1) seroconversion for use in incidence estimates. We have established an algorithm for its use; developed quality control reagents to monitor the assay; and evaluated its performance for interrun, intrarun, and operator variability. Analysis of 144 individual plates, which involved multiple plate lots and several operators over more than a year, indicated that the coefficients of variation (CVs) were between 10 and 15% for raw optical density (OD) values in the dynamic range between 0.5 and 2.0 OD units; the CVs decreased to 5 to 10% when the OD was normalized (OD-n; OD-n = specimen OD/calibrator OD). The intrarun CVs were generally in the range of 5 to 10% for specimens with ODs <0.5 and less than 5% for specimens with ODs >0.5. The level of concordance between multiple plate lots (n = 6) and multiple operators (n = 7) was quite high (R(2) > 0.9). Comparison of the results of the initial and the confirmatory tests with specimens with OD-n values

Characterization of human immunodeficiency virus type-1 from HIV-1 seropositive cases with undetectable viremia.

BACKGROUND: Human immunodeficiency virus type 1 (HIV-1) viral load has become a standard of care among HIV-1-infected patients; however, a small number of patients have undetectable viral load even though they have never been treated. METHODS: By using RT-PCR and DNA-PCR, and followed by sequencing and phylogenetic analyses, a detailed molecular characterization was carried out from five HIV-1-seropositive patients who had undetectable viral load by commercially available ultrasensitive viral load assays. RESULTS: Of the four patients whose plasmas were available, viral RNAs were detected in three of them by using an in-house RT-PCR in at least one of the three regions (integrase, protease or envgp41). The fourth patient had positive RT-PCR signals in these regions only when RNA isolated from the supernatant of cocultivated patient PBLs with PHA-stimulated HIV-1 negative donor PBLs was used. Further analysis of DNA extracted from the PBMCs revealed that four of the five patients had detectable proviral sequences in at least two of the three regions. The fifth patient had only positive PCR results in all three regions when DNA isolated from PHA-stimulated patient's PBLs was used. Phylogenetic analysis of protease and envgp41 regions revealed that three patients were infected with subtype B viruses while the remaining two patients were infected with subtype C and CRF02_AG viruses. These subtypes coincided with geographic origin and known molecular epidemiology of HIV-1 infection. CONCLUSION: These data provide evidence that both subtype B and non-B HIV-1 infection can result in undetectable viral load in HIV-1-infected patients and that efforts should continue to further characterize these viruses.

Performance of the OraQuick and Hema-Strip rapid HIV antibody detection assays by non-laboratorians.

Rapid HIV antibody tests (RT) now permit HIV screening in settings where laboratory personnel may not be available. This study assessed the ability of 99 individuals with no laboratory experience to conduct two RT, OraQuick and Hema-Strip; these results were compared with those generated by laboratory professionals. All participants received written instructions and one-half also received a short demonstration. Error rates ranged from 2.1% to 4.6% with or without a demonstration. However, the number of invalid tests was greatly reduced when participants received a demonstration. Appropriate RT training for non-laboratorians and continued monitoring of HIV RT performance in non-laboratory settings is recommended.

Applying public health strategies to primary immunodeficiency diseases: a potential approach to genetic disorders.

Primary immunodeficiency (PI) diseases are a group of primarily single-gene disorders of the immune system. Approximately 100 separate PI diseases have been described, but <20 probably account for >90% of cases. Although diverse, PI diseases share the common feature of susceptibility to infection and result in substantial morbidity and shortened life spans. Most important, prompt diagnosis and treatment can now lead to life-saving treatment and result in marked improvements in the quality and length of life for persons with PI diseases. In November 2001, a workshop was convened by CDC in Atlanta, Georgia, to discuss ways to improve health outcomes among persons with PI disease. A multidisciplinary panel of persons knowledgeable in PI diseases and public health met to identify and discuss public health strategies that can be applied to PI diseases and possibly for other genetic disorders. A systematic assessment based on the established public health framework was applied to the growing group of PI diseases, whose diverse genetic mutations span multiple components of the immune system but all lead to increased incidence and severity of infections. During the meeting, specialists in clinical immunology, public health, genetics, pediatrics, health communication, and ethics from state and federal agencies, academic centers, professional organizations, and advocacy foundations discussed the four components of the public health framework as they relate to PI diseases. These four components include 1) public health assessment (application of traditional public health methods to assess the occurrence and impact of PI diseases on communities); 2) population-based interventions (development, implementation, and evaluation of screening tests administered to newborns and clinical algorithms for early recognition of symptomatic persons to facilitate the earliest possible diagnosis and treatment for PI diseases); 3) evaluation of screening and diagnostic tools (to ensure their quality and appropriateness for identification of patients with PI diseases); and 4) communication (communication with and information dissemination to health-care providers and the public to facilitate prompt and appropriate diagnosis and intervention). The working group's deliberations focused on challenges and opportunities, priority research questions, and recommendations for future action for these four components. These recommendations, developed by workshop participants, will be useful to medical and public health professionals who are evaluating methods to increase recognition of PI diseases and other genetic disorders.

A critical evaluation of enzyme immunoassay kits for detection of antinuclear autoantibodies of defined specificities. III. Comparative performance characteristics of academic and manufacturers' laboratories.

OBJECTIVE: To analyze the performance of different commercial enzyme immunoassay (EIA) kits for measuring antinuclear antibodies (ANA) specific for dsDNA, SSB/La, Sm, and Scl-70. METHODS: EIA kits for detection of ANA from 9 commercial manufacturers were evaluated. The manufacturers were advised that they would be sent coded sera containing mixtures of the Arthritis Foundation/Centers for Disease Control reference reagents, and that they were to use their own test kits to analyze the antibody specificities of these sera and to report the data, in optical density (OD) units or their equivalent. Independently, 12 investigators in academic institutions who have done research in this field agreed to participate in a parallel study. The concentration of the antibodies and the specificities were blinded to the analysts and the coefficients of variation (CV) were computed for each participant. RESULTS: There were statistically significant differences between laboratories in terms of CV for all 9 kits tested. With the exception of one kit, there were no significant CV differences between the various autoantibody kits provided by each manufacturer and, with the exception of kits from 2 manufacturers, there were no significant differences between the various antibody kits in terms of reproducibility (CV). From the point of view of interlaboratory variability, manufacturers could be separated into either a high or low performance group. CONCLUSION: We found a disconcertingly large range of performance characteristics in the various laboratories, which could be quite detrimental in routine utilization of EIA ANA kits. Clinicians should be aware of the performance issues raised in our study, and should know and be involved in how their service laboratory assesses its own performance and the performance of commercial testing systems utilized. Manufacturers and clinical laboratories need to exercise constant quality assurance and surveillance of kit performance in the hands of medical laboratory technologists involved in routine testing.

HIV type 1 incidence estimates by detection of recent infection from a cross-sectional sampling of injection drug users in Bangkok: use of the IgG capture BED enzyme immunoassay.

Development of serologic tests to detect recent HIV-1 infection has generated worldwide interest in applying this approach to estimate incidence. We previously devised an IgG-capture BED-EIA (or BED-CEIA) that detects increasing levels of anti-HIV IgG following seroconversion to identify recent infection and to estimate incidence among persons infected with diverse HIV-1 subtypes worldwide. Injection drug users (IDUs; n = 1969) were screened in 1996 for participation in a prospective cohort study. Serum specimens from 594 IDUs were HIV-1 seropositive (30.2%) and were tested with the BED-CEIA. The proportion of recent infections and estimated incidence by different epidemiological risk factors were compared with incidence data measured from the prospective cohort. Of 594 HIV-1-seropositive specimens, 113 (19%) were identified as recent infections. Overall, the estimated annual incidence among persons screened was 17.3%/year (95% CI, 12.8-24.2%/year) compared with 9.0%/year (95% CI, 6.7-11.9%/year) measured from the prospective cohort during the same time period. Estimated incidence was higher among younger aged and unemployed IDUs as well as among those who injected more frequently, confirming previously reported risk factors from this prospective cohort. As persons screened from a cross-sectional sampling probably have higher risk for HIV than selected uninfected individuals who choose to participate and receive risk reduction counseling in a longitudinal cohort study, use of this or other serologic testing strategies to identify populations with high incidence (such as for HIV vaccine trials) may overestimate incidence measured from prospective cohorts.

Human immunodeficiency virus (HIV) seropositivity among uninfected HIV vaccine recipients.

Since 1987, >10,000 individuals worldwide have received immunizations with human immunodeficiency virus (HIV) preventive vaccine constructs. Many constructs elicit antibodies detected by standard serologic tests (enzyme immunoassays, rapid tests, and Western blots) and result in vaccine recipients' serum being identified as reactive and indicative of HIV infection. To determine the frequency of vaccine-induced HIV antibody among uninfected HIV vaccine trial participants and to identify factors associated with these results, serum samples from HIV-uninfected participants from selected United States phase I/II HIV-1 vaccine trials were tested with 6 serologic screening tests. Reactive specimens were tested by use of Western blot. Overall, 490 serum specimens from 461 vaccine recipients were tested; 100 (20.4%) reacted on at least 1 serologic test, and 65 (13%) were determined to be positive by Western blot. Canarypox or vaccinia vaccine recipients' serum with or without HIV envelope glycoprotein (gp120 or gp160) boosts accounted for all positive Western blot results; no positive Western blot results were obtained from gp120 subunit recipients. The potential for vaccine recipients being misclassified as HIV infected increased with vaccine complexity.

Guidelines for performing single-platform absolute CD4+ T-cell determinations with CD45 gating for persons infected with human immunodeficiency virus. Centers for Disease Control and Prevention.

These guidelines were developed by CDC for laboratorians who perform immunophenotyping for detection and enumeration of CD4+ T-cells and other lymphocyte subsets in persons infected with human immunodeficiency virus (HIV). The guidelines describe single-platform technology (SPT), a process in which absolute counts of lymphocyte subsets are measured from a single tube by a single instrument. SPT incorporates internal calibrator beads of known quantity in the analysis of specimens by three- or four-color flow cytometry. With CD45 gating, the relative numbers of beads and lymphocyte subsets are enumerated, and their absolute numbers and percentage values are calculated. This report supplements previous recommendations published in 1997 (CDC. 1997 revised guidelines for performing CD4+ T-cell determinations in persons infected with human immunodeficiency virus [HIV]. MMWR 1997;46[No. RR-2]) that describe dual-platform technology, a method in which absolute counts are derived from measurements obtained from two instruments--a flow cytometer and hematology analyzer. The new recommendations address concerns specific to the implementation of SPT as well as other general topics such as laboratory safety and specimen handling.