HIV核心抗原p24检测方法的建立及应用

ＨＩＶ感染的检测在预防ＡＩＤＳ传播方面有重要作用。本研究以重组抗原ｐＧ１免疫Ｂａｌｂ／ｃ小鼠，应用淋巴细胞杂交瘤技术建立了５株识别ＨＩＶ核心抗原ｐ２４的杂交瘤细胞株Ｄ３，１Ｈ１，２Ｇ１０，３Ｈ５和４Ｈ６。经鉴定这５株ＭｃＡｂ与其它病毒抗原无交叉反应，分别识别３个不同的抗原表位。应用两株识别不同表位的ＭｃＡｂ２Ｇ１０和３Ｈ５建立了检测ＨＩＶｐ２４抗原的夹心ＥＬＩＳＡ法，并初步检测了２４份ＨＩＶ抗体阳性血清。     

人源抗人免疫缺陷病毒1型噬菌体抗体库的构建及筛选

目的构建人免疫缺陷病毒１型（ＨＩＶ－１）特异性噬菌体抗体库，制备人源抗ＨＩＶ－１ｇｐ１２０单克隆抗体。方法以半巢式聚合酶链反应（ＰＣＲ）从ＨＩＶ－１感染者外周血单个核淋巴细胞中扩增抗体重链Ｆｄ和轻链（ｋ）基因，与噬菌体载体ｐＣｏｍｂ３连接，构建噬菌体抗体Ｆａｂ组合文库。对抗体库进行３轮吸附－洗脱－扩增的亲和选择后，以ＥＬＩＳＡ法筛选抗ＨＩＶ－１ｇｐ１２０噬菌体抗体，并进行ＤＮＡ序列分析和Ｆａｂ的可溶性表达。结果半巢式ＰＣＲ有效地扩增出Ｆｄ和ｋ基因，以此构建成容量为１９５×１０７的噬菌体抗体库。３轮亲和选择使特异性抗体得到高度富集，抗ＨＩＶ－１ｇｐ１２０噬菌体抗体阳性克隆占３２％。对一阳性克隆抗体基因ＣＨ１和ＣＬ部分ＤＮＡ序列进行了测定，并在大肠杆菌表达出可溶性Ｆａｂ。结论抗ＨＩＶ－１特异性噬菌体抗体库的构建和人源抗ＨＩＶ－１ｇｐ１２０单克隆抗体的制备为今后筛选抗ＨＩＶ中和抗体奠定了基础，具有重要的应用价值。     

抗HIVp24单链抗体的基因构建及序列测定

应用重组噬菌体抗体系统，从经过ＨＩＶ全蛋白裂解物及ｐ２４免疫过的鼠脾细胞ｍＲＮＡ中构建出组合单链抗体（ＳｃＦｖ）ｃＤＮＡ文库。ｃＤＮＡ文库克隆到噬菌粒载体ｐＣＡＮＴＡＢ５Ｅ，转化大肠杆菌ＴＧ１，得到２５×１０７个氨苄抗性菌落。通过噬菌体表面呈现，用ｐ２４蛋白对表达的重组噬菌体单链抗体文库进行两轮亲和富集获得一株特异性好的抗ｐ２４的噬菌体单链抗体。经ＥＬＩＳＡ鉴定，该噬菌体呈ｐ２４结合ＥＬＩＳＡ阳性的滴度小于１０７ｐｆｕ／ｍｌ。并对ＳｃＦｖ进行了序列分析，对今后的应用奠定了基础。     

抗人免疫缺陷病毒1型gp120人源单链抗体的表达

目的研究人源抗人免疫缺陷病毒１型（ＨＩＶ－１）ｇｐ１２０单链抗体（ＳｃＦｖ）。方法以人工合成的ＨＩＶ－ｌｇｐ１２０Ｖ３环多肽为抗原，利用噬菌体抗体库技术，筛选含有抗－ｇｐ１２０ＳｃＦｖ基因的噬菌体，提取质粒，转化大肠杆菌ＨＢ２１５１，表达可溶性ＳｃＦｖ。结果经ＳＤＳ－ＰＡＧＥ和Ｗｅｓｔｅｒｎｂｌｏｔ分析，表达产物分子量为２８ｋＤ左右，且具有ｃ－ｍｙｃ活性；ＥＬＩＳＡ和Ｄｏｔｂｌｏｔ结果表明，可溶性ＳｃＦｖ具有较好的抗原结合活性和较强的特异性；竞争性ＥＬＩＳＡ实验结果进一步证明表达产物的特异抗－ｇｐ１２０活性。结论该技术便捷有效，可大量获得人源抗ＨＩＶ抗体片段，为进一步研究抗ＨＩＶ抗体的生物活性和ＨＩＶ感染诊治打下基础     

人巨细胞病毒单克隆抗体的研制检定和应用

采用人巨细胞病毒（ＨＣＭＶ）ＡＤ１６９株作为免疫原，制备出１３株鼠－鼠杂交瘤细胞系。对其中的６株进行了检定．免疫印迹试验结果表明：单克隆抗体（ＭｃＡｂ）７Ｂ４、７Ｄ７、７Ｅ１１、８Ｅ８和８Ｄ６相对应的ＨＣＭＶ多肽分子量分别为４６、１５０、３８、５１７２和６５ｋＤ．ＨＣＭＶ感染人胚肺二倍体细胞（２ＢＳ）后不同时间制成抗原片，与ＭｃＡｂ作间接免疫荧光试验。结果表明：ＭｃＡｂ８Ｂ８相应的病毒多肽为即刻早期抗原，其它５株ＭｃＡｂ相应的病毒多肽均为晚期抗原，６株ＭｃＡｂ等量混合后，标上辣根过氧化物酶，用于ＩｇＭ抗体捕获法ＥＬＩＳＡ（ＭａｃＥＬＩＳＡ）中，并与间接ＥＬＩＳＡ（ＩＥＬＩＳＡ）同时检测ＨＣＭＶ－ＩｇＭ．在未经选择的１００份脐带血中，两法均为阳性的３份，两法均为阴性的９４份；ＭａｃＥＬＩＳＡ阳性而ＩＥＬＩＳＡ阴性的２份血清的特异性试验证明，ＨＣＭＶ－ＩｇＭ确为阳性．ＩＥＬＩＳＡ阳性而ＭａｃＥＬＩＳＡ阴性的１份血清的特异性试验证明，它是由ＲＦ引起的假阳性。     

合成肽抗原抗人免疫缺陷病毒1/2型抗体酶联试剂盒的研制

根据人免疫缺陷病毒（ＨＩＶ）的基因结构和氨基酸序列，采用固相法合成了ＨＩＶ－１ｇｐ４１（ＳＰ１）、ｇｐ１２０（ＳＰ２）、ｐ２４（ＳＰ３）和ＨＩＶ－２ｇｐ３６（ＳＰ４）的４条多肽，混合包被酶标板做为固相抗原，采用间接酶联免疫吸附试验（ＥＬＩＳＡ），建立了检测抗－ＨＩＶ－１／２ＩｇＧ抗体的酶联诊断试剂盒。检测卫生部药品和生物制品检定所提供的４１份质控参比血清，其特异性、敏感性均为１００％，变异系数小于１０％。检测１８６份其它病种病人血清均为阴性，与华怡、巴斯德、金豪等公司的ＨＩＶ诊断试剂比较检测了９０份ＨＩＶ感染者和１４０份正常人血清，除与华怡试剂的阴、阳性及总符合率分别为９９２９％（１３９／１４０）、９８９０％（９０／９１）和９９５７％（２２９／２３０）外，其余均为１００％。３７℃放置４天后试剂的检测结果不受影响。     

基因免疫诱导9.1C3分子内影像类抗独特型抗体的产生

本文分别采用真核表达载体ｐＥＦ－ＢＯＳ及ｐＣＭＶ４构建含起始码和终止码的抗９．１Ｃ３分子单克隆抗体重链可变区基因重组表达质粒９．１Ｃ３ＶＨｐＥＦ－ＢＯＳ及９．１Ｃ３ＶＨｐＣＭＶ４，并将其分别免疫ＢＡＬＢ／ｃ小鼠。取免疫小鼠血清对Ｋ５６２细胞进行间接免疫染色和流式细胞仪分析表明，基因免疫小鼠体内可诱导９．１Ｃ３分子内影像类抗独特型抗体的产生。     

白细胞介素6单克隆抗体的研制

采用纯化的工程菌表达产物白细胞介素６免疫ＢＡＬＢ／Ｃ小鼠,取小鼠脾细胞与骨髓瘤细胞（ＳＰ２／０）在ＰＥＧ作用下进行融合,通过ＥＬＩＳＡ筛选并多次亚克隆,获得了１株能分泌抗ＩＬ－６单克隆抗体的杂交瘤细胞Ｉｃ－１．３．４．５。Ｗｅｓｔｅｒｎ ｂｌｏｔ显示：抗体结合抗原的分子量与ＩＬ－６相符,为特异性抗ＩＬ－６抗体。亚类鉴定表明：该细胞分泌的单克隆抗体为ＩｇＧ１亚类,ｋａｐｐａ型。染色体数目为１００条左     

从粪便及胃液中检测癌相关抗原GP87,CEA,S—Tn及尿激？…

为寻找胃癌普查的简便方法，冯抗消化道肿瘤单克隆抗体（ｍＡｂ）Ａｄｎａｂ－９，组合ＣＬ－３，ＧＳ－２和抗原激酶（ＵＰＡ）多克隆抗体，用ＥＬＩＳＡ直接法和酶免疫电泳法，检测了粪便标本１４４例和胃液标本１５３例中癌相关抗原ＧＰ８７，ＣＥＡ，Ｓ－Ｔｎ及ＵＰＡ。结果表明，以抗ＧＰ８７ｍＡｂ Ａｄｎａｂ－９检测时，粪便组的阳性率：胃癌为８７．９％，萎缩性胃炎（ＣＡＧ）为７４．１％，ＣＡＧ伴不典型增生（ＡＴＰ）     

艾滋病血清学诊断新方法的建立

以基因工程表达的人免疫缺陷病毒１型（ＨＩＶ－１）ｇｐ４１和ＨＩＶ－２型ｇｐ３６作为诊断抗原，将抗原机械喷制在硝基纤维素膜上，以辣根过氧化物酶结合的兔抗人ＩｇＧ作为标记抗体，建立了检测人血清中ＨＩＶ－１／２型抗体的免疫斑点法（ＩＤＡ）。用ＩＤＡ检测血清中的ＨＩＶ抗体，特异性和敏感性均达到国、内外ＥＬＩＳＡ检测水平，并完全达到对ＨＩＶ－１／２型抗体诊断试剂国家质控标准。     

同时检测HIV抗体及p24抗原快速诊断试剂的研制

目的：研制可同时检测HIV－1、HIV－2抗体及p24抗原的胶体金快速诊断试剂。方法：利用重组杆状病毒－昆虫细胞系统进行HIV－1 gp41及HIV－2 gp36抗原的高效表达，以免疫亲和层析法纯化抗原。抗－HIV p24单克隆抗体杂交瘤细胞株，并制备抗－HIV p24单克隆抗体。以硝酸基纤维膜为载体，以纯化的HIV－1 gp41、HIV－2 gp36抗原及抗p24抗体点膜，20nm胶体金颗粒／抗人IgG和抗－HIV p24单克隆抗体进行标记，对33份已知HIV感染者阳性血清及6份阴性血清进行检测。结果：通过重组杆状病毒－昆虫细胞系统进行HIV－1 gp41及HIV－2 gp36抗原的表达，可获取浓度为2．0mg/L的纯化抗原。从抗p24单克隆抗体杂交瘤细胞株中培养上清液，通过葡萄球菌蛋白A免疫亲和层析柱可得到1．5mg/L的纯化抗体。利用纯化的抗原抗体进行标记，对39份已知血清进行检测，与荷兰Organon公司HIV1＋2抗体、p24抗原、ELISA诊断试剂同时检测结果进行比较，证实有较强的特异性及敏感性。结论：同时检测HIV－1、HIV－2抗体及p24抗原快速诊断试剂的问世，可为HIV感染的诊断提供一个简便、可靠、敏感的方法。     

High prevalence of HIV p24 antigen among HIV antibody negative prospective blood donors in Ile-Ife,Nigeria

Blood transfusion service centers in Nigeria screen donated blood for markers of HIV infection using antibody- (Ab) based rapid test and in some centers, positives are re-tested using Ab-based ELISA. Paucity of data exists on p24 antigen prevalence among HIV Ab-negative donors in Nigeria. This study aims at detecting HIV p24 antigen among prospective blood donors in Osun State, Nigeria. Prospective blood donors negative for HIV antibodies using Determine test kit were re-tested using BIORAD GENSCREEN Ultra Ag-Ab ELISA kit, a fourth-generation ELISA kit that detects HIV antibodies/p24 antigen. Of the 169 HIV Ab-negative prospective donors, 10 (5.9%) were positive for HIV p24 antigen and 70% (7/10) of them were in the age range 18–30 years. Results of this study show that blood transfusion is still one of the major routes of HIV transmission in Nigeria and a higher proportion is among youth. Inclusion of p24 antigen testing into the blood donor screening will help reduce transfusion associated HIV in Nigeria if Nucleic Acid Testing (NAT) of all blood donor samples is not affordable; also, HIV enlightenment programs tailored toward youth may help reduce this rate among donors since more young people donate blood in low/middle-income countries than in high-income countries.     

Performance evaluation of three automated human immunodeficiency virus antigen-antibody combination immunoassays

Three fourth-generation antigen/antibody combination assays (Elecsys, AxSYM, Architect HIV) and two third-generation (AxSYM, Centaur) HIV antibody immunoassays were evaluated. The evaluation panel of 479 samples included: nine tissue culture derived HIV-1 strains at four different p24 antigen concentrations (n=36), a p24 antigen sensitivity panel (n=10), 149 HIV-1 or HIV-2 confirmed antibody positive samples, ten anti-HIV-1 positive low titer samples, three seroconversion panels (n=21), and 253 HIV negative samples. The Architect had the best sensitivity for detection of HIV-1 antigen across eight HIV-1 subtypes, followed by the AxSYM while the Elecsys could not detect the highest antigen concentration evaluated (25 pg/mL) for eight of nine virus isolates. All assays showed 100% sensitivity for detection of HIV-1, group M, group O, and HIV-2 antibody positive samples. The Architect Ag/Ab Combo assay detected the first positive bleed of the three seroconversion panels and detected infection 4-26 days earlier than the third generation assays. Based on evaluation of 253 negative samples, assay specificity varied from 98.0% to 99.6%. The Architect HIV Ag/Ab Combo exhibited the best performance for specificity and detection of p24 antigen leading to closure of seroconversion window and demonstrating its utility for early diagnosis of HIV infection.     

New Automated Chemiluminescence Immunoassay for Simultaneous but Separate Detection of Human Immunodeficiency Virus Antigens and Antibodies

The recently launched Liaison XL Murex HIV Ab/Ag assay (DiaSorin S.p.A) uses chemiluminescence immunoassay technology for the combined qualitative determination of p24 antigen of HIV-1 and specific antibodies to both HIV-1 and HIV-2. We studied 571 serum samples from those submitted to our laboratory for HIV screening. The samples were divided into 3 subsets: subset A, 365 samples collected prospectively during 1 week; subset B, 158 samples from confirmed HIV-positive patients; and subset C, 48 samples with a positive screening result but a negative or indeterminate confirmatory test result. Our standard screening/confirmatory algorithm was used as a reference. In subset A (prospective), 5 samples were positive and 360 negative by the standard procedure. Liaison XL Murex HIV Ab/Ag correctly identified all 5 positive samples (100%) and 357 negative samples (99.2%). In subset B (confirmed positive), all 158 positive samples were in total agreement in both procedures. In subset C (screen positive only), Liaison XL Murex HIV Ab/Ag yielded accurate results in 42 out of 48 samples (87.5%). Global sensitivity and specificity for Liaison XL Murex HIV Ab/Ag (all subsets included) were 98.3% and 98.5%, respectively. Considering only nonselected prospective samples and confirmed positive samples (subsets A and B), the corresponding sensitivity and specificity values were 100% and 99.2%, respectively. The new fully automated HIV screening test showed high sensitivity and specificity compared to our standard algorithm. Its added advantage of being able to detect HIV-1 and HIV-2 antibodies and p24 antigen separately could prove useful in the diagnosis of early infections.     

Evaluation of a newly developed HIV antigen test

A new monoclonal antibody-based enzyme immunoassay (Innogenetics) for the detection and quantification of p24 core antigens of HIV-1 (group M and group O) and of HIV-2 was evaluated on 2745 serum samples and 18 culture supernatants and compared with a reference (Coulter) HIV-1 p24 antigen assay. Positive results were confirmed by neutralization with the reagents of the respective tests. As demonstrated by dilution series of HIV cocultures, the new test recognizes p24 antigen of the most common HIV genetic subtypes, including group O and HIV-2. Titres ranged from 729 to 531441. Therefore p24 antigen assay is but very weakly reactive with HIV-2 (titres from 9 to 81). The new test is considerably more sensitive than the reference. In a population of 365 follow-up samples from 86 different patients, representing all stages of infection, the new test detected p24 antigen at least once in 52% (45/86) of these patients, whereas the reference was positive in 31% (27/86). The newly designed test detected antigen in 40% (145/365) of the samples, while the reference was positive in 21% (75/365). In a group of PCR and/or culture positive neonates, 33% (9/27) of the samples were positive with the new test versus 18% (5/27) with the reference. The specificity of the new test, as determined on 2,000 blood donor samples, was 99.65% (initially), 99.80% (after repetition), and 100% (with neutralization). The reference scored 99.95%, 100%, and 100%, respectively. In 300 seronegative samples from persons at risk, the initial specificity of the new test was 98.67% (the reference, 99.00%). With neutralization, both assays were 100% specific. J. Med. Virol. 53:31–35, 1997. © 1997 Wiley-Liss, Inc.     

Comparative study of 2 commercial tests for the detection of HIV-1 antigens in blood and cerebrospinal fluid using immunoenzymology

The authors have carried out, on 150 sera of patients seropositive for the human immunodeficiency virus type I (HIV I) and 11 cerebrospinal fluid of which 5 were patient infected by the HIV I, a comparative study of two commercial tests for the detection of HIV I antigen (Diagnostic Pasteur and Abbott laboratories). A much greater sensitivity was obtained with the specificity being practically identical for the sera with the two tests (100% with Abbott laboratories test, 96.11% with the diagnostic Pasteur test). 4 sera appeared "false negatives" with the Abbott Laboratories test; their optical density was situated between 80 and 100 p. cent of the cut-off level value, whereas that of the "real" negatives was situated between 30 and 60 p. cent of the cut-off level value. 10 of the 11 cerebrospinal fluids appeared false positive with the Diagnostic Pasteur. This seems to be connected with an insufficiency of saturation of protein receptors in the wells. The Diagnostic Pasteur test is not adapted for the detection of HIV I antigen in the body fluids with a weak protein concentration. Contrary to the results obtained with the Encavor test (Abbott laboratories) the analysis in western-blot does not show an inverse prevalence of anti p24 GAG antibodies with regard to antigen HIV I in seropositive patients. On the other hand, the statistical analysis of the positive HIV I sera which are at the same time antigen HIV I positive and antibodies HIV I positive suggests an earlier disappearance of anti p17 GAG antibodies than of anti p24 GAG antibodies.     

Free and antibody-complexed antigen and antibody profile in apparently healthy HIV seropositive individuals and in AIDS patients

The pattern of free and antibody-complexed HIV antigen and the antibody profile were investigated retrospectively in 305 serum samples taken from 22 AIDS patients before and during the development of AIDS and from 40 apparently healthy seropositive individuals. Most AIDS patients were found positive for both free and complexed antigen and had high gp41 antibody titres but low or undetectable p24 antibody. Four different patterns of HIV antigenaemia were observed: 1) positive for both free and complexed antigen; 2) negative for free HIV antigen at first, but always positive for complexed antigen; 3) positive for free antigen without complexed antigen; and 4) negative for both free and complexed antigen. The development of immune complexes preceded the appearance of free antigen and might reflect the ongoing viral replication with antigen excess and binding of anticore antibodies. No correlation was found between the development of AIDS symptoms and either the duration of free antigen positivity or the level of antigenaemia. A different pattern was observed in apparently healthy seropositive individuals: 90% of whom had high antibody titres to p24 and gp41 and were persistently negative for free and complexed HIV antigen. This study demonstrates that testing HIV markers in sequentially collected serum samples from HIV seropositive individuals is a useful and simple tool for early identification of persons at risk of developing AIDS.     

Evaluation of a simultaneous HIV antigen and antibody detection test in Korean population

Current diagnosis of human immunodeficiency virus (HIV) infection relies on the detection of anti-HIV antibodies by enzyme-linked immunosorbent assay (ELISA). Recently, kits detecting both p24 antigenemia and anti-HIV/anti-HIV2 antibodies have been developed. Thus, it is necessary to compare those kits developed as such. The aim of this study was to evaluate the diagnostic efficiency of a simultaneous detection test of p24 antigen and anti-HIV1/2 antibodies in a low prevalence area. Eight hundred and four randomly selected sera proven negative for HIV infection and 110 sera from 54 patients diagnosed as HIV infected, obtained between 1999 and 2000, were used for this study. One commercial lot of panels composed of consecutive sera obtained from known HIV-infected patient was included. Anti-HIV1/2 antibodies were detected by two different commercial ELISA kits, one from Korean and the other from German manufacturer. P24 antigen test was performed by ELISA. The simultaneous HIV antigen and antibody detection test was carried out. In the meantime, HIV RNA PCR and anti-HIV and anti-HIV2 western blot assays were also performed to confirm the test results in cases the test results didn't agree. The simultaneous detection kit showed 100% sensitivity and 99.6% specificity. Furthermore, the test displayed the possibility of earlier diagnosis than conventional anti-HIV1/2 ELISA with the results obtained from a group of consecutive panel sera infected with HIV. From these results, we concluded that the simultaneous HIV antigen and antibody detection test can be applied as a substitute clinical screening test in the place of conventional anti-HIV1/2 ELISA, and there is the probable benefit of early diagnosis.     

Evaluation of the analytic performance of blood collection tubes (BD Vacutainer SST) for the screening of anti-HIV, anti-HTLV, anti-HCV, anti-HBc, anti-CMV antibodies, and of HBs, P24 HIV antigens, and of alanine aminotransferase]

The Laboratory of Viral Diseases Immunology (Laboratoire d'Immunologie des Maladies Virales) of the Northern Region Blood Bank (Etablissement Fran?ais du Sang Nord de France) performs between 180.000 and 200.000 viral blood qualifications per year. The use of a serum gel separator evacuated tube should contribute to improve the quality of the pre-analytical phase. However, it must not impact negatively the analytical performances. We evaluated such tube within our specific environment and with the various reagents used in routine. The open study compared the BD Vacutainer plain tube (7 mL, non siliconised) with the BD Vacutainer SST tube (6 mL siliconised with serum gel separator) against the anti-HIV, anti-HTLV, anti-HCV, anti-HBc, anti-HBs, anti-CMV antibodies, the HBs, HIV P24 antigen and the alanine aminotransferase. The study objectives were to find potential gel interference; to verify the diagnostic sensitivity, reagents specificity, and reproducibility. The results analysis show: equivalent performances with the anti-HIV Ab (Anti HIV 1/2 recombinant--Biotest et Genscreen HIV 1/2--Sanofi), anti HIV WB Ab (New Lav Blot 1--Sanofi), anti-HBs Ab (Enzygnost anti-HBs micro--Behring), anti-HBc Ab (HBc Elisa Test System--Ortho), anti-CMV Ab (Enzygnost anti-CMV IgG + M--Behring) kits; lower performances with: The Vironostika HIV Uni Form II plus 0--Organon kit with a -3.5% signal decrease around the ratio R = 2.7 for positive anti-HIV Ab. The Elisa test System 3 Ag HBs-Ortho kit with an increase of the mean ratio of the negative Ag HBs samples; better performances with: the Vironostika HIV 1 Antigen--Organon kit with a +10% signal increase around the threshold ratio R = 1 for positive Ag HIV samples. This deserves further study to verify that the specificity is maintained. The HTLV Type 1 et 2 EIA--Ortho kit with +8% signal increase around the ratio R = 2 for positive anti-HTLV Ab samples without change of the specificity. The Ortho HCV 3.0 Elisa Test System and HTLV Type 1 et 2 EIA kits with a clear and significant improvement of the reproducibility of the anti-HCV and anti-HTLV Ab screenings. The results of this evaluation, together with the intrinsic BD SST tube characteristics, lead to the conclusion that its use would contribute to improve the quality. Because of the specificities of each laboratory, a change of tube type, as with any other material or reagent, request a close monitoring of the first results to confirm the absence of negative effects.     

Optimized virus disruption improves detection of HIV-1 p24 in particles and uncovers a p24 reactivity in patients with undetectable HIV-1 RNA under long-term HAART

HIV-1 p24 antigen (p24) measurement by signal amplification-boosted ELISA of heat-denatured plasma is being evaluated as an alternative to HIV-1 RNA quantitation in resource-poor settings. Some observations suggested that virion-associated p24 is suboptimally detected using Triton X-100-based virus dissociation buffer (kit buffer). A new reagent (SNCR buffer) containing both denaturing and non-denaturing detergents was therefore developed and evaluated. The SNCR buffer increased the measured p24 concentration about 1.5- to 3-fold in HIV-negative plasma reconstituted with purified HIV-1 particles, while not increasing the background. Among 127 samples of HIV-1-positive patients with moderate to high concentrations of HIV-1 RNA the increase was about threefold across the entire concentration range (P < 0.0001). Specificity before neutralization among prospectively tested clinical samples ruled HIV-negative was 828 of 845 (98.0%) for the SNCR buffer and 464 of 479 (96.9%) for kit buffer. Specificity after confirmatory neutralization of reactive samples or a follow-up test was 100% with either buffer. Surprisingly, the SNCR buffer revealed a p24 reactivity in 115 of 187 samples (61.5%) from adult patients exhibiting undetectable HIV-1 RNA below 5 copies/ml for a duration of 6-30 months under HAART (3.7% with kit buffer). The rate of p24 reactivity in these patients did not decrease with duration of HAART. In conclusion, the SNCR buffer improves the detection of particle-associated HIV-1 p24, thereby increasing the measured p24 concentration in samples with medium to high HIV-1 RNA. It also uncovers the presence of a p24 reactivity, whose identity remains to be determined, in a significant fraction of samples with undetectable HIV-1 RNA under long-term HAART.