Performance characteristics of a combined hepatitis C virus core antigen and anti-hepatitis C virus antibody test in different patient groups

We evaluated the performance of a hepatitis C virus (HCV) antigen/antibody combination test [Murex HCV Antigen/Antibody Combination Test (Murex Ag/Ab test)] by comparing it with the current third-generation HCV antibody enzyme immunoassay (anti-HCV). A total of 403 serum samples were consecutively collected from four patient groups: healthy controls (n=100); HCV-infected patients (HCV?group, n=102); Human immunodeficiency virus (HIV)/HCV-infected patients (HIV/HCV group, n=100); and patients with uremia (uremia group, n=101). Performances were evaluated for the Murex Ag/Ab, anti-HCV, and HCV RNA in the HIV/HCV and uremia patient groups. In the HCV group, all 102 samples showed concordant positive and negative results for anti-HCV, Murex Ag/Ab, and HCV RNA tests. In the HIV/HCV group, all 100 samples were positive for both anti-HCV and Murex Ag/Ab tests, whereas 88 patients (88%) were HCV RNA positive. In the uremia group, 14 (69.0%) of the 23 anti-HCV-positive patients were HCV RNA positive, whereas 14 (77.8%) of the 18 Murex Ag/Ab-positive patients were HCV RNA positive. None of anti-HCV-negative or Murex Ag/Ab-negative patients were HCV RNA positive. Based on the HCV RNA assay, the sensitivities for both anti-HCV and Murex Ag/Ab assays were 100%, whereas the specificities of these two assays were 89.7% and 95.4%, respectively. With good sensitivity and specificity, the Murex Ag/Ab assay could be a useful alternative diagnostic tool, especially in immunocompromised populations, such as patients with uremia or those infected with HIV.     

Diagnosis of primary HIV-1 infection and duration of follow-up after HIV exposure. Karolinska Institute Primary HIV Infection Study Group

OBJECTIVE: To determine the sensitivity of 33 currently available and seven earlier tests for the detection of HIV or HIV antibody in primary HIV-1 infection, to estimate the duration of the 'window period' and the influence of early initiated antiretroviral treatment (ART). DESIGN: A prospective cohort study of 38 patients with primary HIV-1 infection. ART was initiated at a median time of 13 (range 0-23) days after the onset of symptoms in 10 patients. MAIN OUTCOME MEASURES: The time from infection to onset of symptoms and from onset of symptoms to the appearance of HIV antibody as measured by 36 different tests, and the start and duration of viraemia, as detected by four different tests. RESULTS: The illness appeared 13-15 days after infection in 12 of 15 determinable cases, and seroconversion was detected within 1-2 weeks after the onset of illness by 27 of 30 currently available tests for HIV antibody, in contrast to the 2-7 weeks or more needed by the old tests. HIV RNA appeared during the week preceding the onset of illness and was detected in all subsequent samples, except when ART had been initiated, which also induced a delay of the antibody response. CONCLUSION: Many tests for HIV or HIV antibody can now be employed for an early confirmation of primary HIV infection (PHI). Currently available screening tests proved much more sensitive than older tests, and seroconversion was usually detected within one month after infection. Consequently, in Sweden we now recommend only 3 months of follow-up after most cases of HIV exposure.     

A sensitive viral capture assay for detection of plasma viremia in HIV-infected individuals.

Human immunodeficiency virus was detected in the serum/plasma of individuals infected with human immunodeficiency virus (HIV) after capture of virions on microparticles coated with monoclonal antibodies to external and transmembrane proteins of HIV-1. We analyzed serial samples obtained from 6 individuals who seroconverted, 18 asymptomatic, and 12 AIDS patients. HIV-1 RNA was detected in all (29/29) seropositive samples and in 6 seronegative samples immediately preceding seroconversion. In contrast, HIV antigen was detected in 13/29 (45%) of seropositive samples. HIV-1 RNA was also detected in 3 antigen-negative samples from one individual 8-5 months prior to seroconversion and in one sample from another person 2 days before antigen positivity. The intensity of the polymerase chain reaction (PCR) signal paralleled the concentration of HIV antigen. Conversely, seropositive HIV antigen-negative samples gave a weaker PCR signal. HIV-1 RNA was detected in 10/18 (60%) samples from asymptomatic, HIV antigen-negative, individuals and in 11/12 (92%) specimens obtained from AIDS patients. The viral capture method may provide a sensitive, specific, and semiquantitative means of detecting circulating HIV at all stages of infection.     

Human herpes virus 8 (HHV8) serology in allogeneic bone marrow transplant recipients.

Human herpes virus 8 (HHV8) may be sexually transmitted, but transmission via blood cells has not yet been excluded. We used a modified immunofluorescence assay to detect Ab to HHV8 latency-associated nuclear Ag in sera of 200 allogeneic BMT recipients and their related donors. In control subjects, Ab were found in 85% of patients with AIDS-related Kaposi sarcoma (n = 52), 34% of HIV-1 infected subjects without Kaposi sarcoma (n = 56) and 9. 5% of blood donors (n = 42). Among BMT donors, 14.5% were HHV8+, while 10% of recipients were positive before, and 18% after BMT. In the 176 HHV8-negative recipients at BMT, there was no relationship between post-BMT seroconversion, which occurred in 26 cases (15%), and the donor's serological status. Of note, 10 HHV8+ recipients before BMT became negative post-BMT. Outcome of BMT was not influenced by prior HHV8 seropositivity, seroconversion or seroreversion of recipients. That HHV8 seropositivity among blood donors from the Paris area was comparable to that of BMT donors and recipients before BMT indicates that these patients had not been at risk of HHV8 by blood products received before BMT, although post-BMT HHV8 seroconversion probably corresponded to contamination by blood transfusions rather than by the BMT.     

Diagnostic value of specific IgM antibodies in primary HIV infection

Sequential serum samples from 55 homosexual men with primary HIV infection were tested for IgM anti-HIV. An early IgM response was found in 27 out of 55 (49%). In five cases IgM anti-HIV was detected 1-3 1/4 months prior to IgG anti-HIV seroconversion, as detected by a commercially available ELISA, but in no case was IgM detected prior to IgG anti-HIV seroconversion, as detected by the more sensitive GACRIA (IgG antibody captive radio-immunoassay, see Subjects and methods) and immunoblot assays. In 22 out of 23 men (96%) the primary IgM response did not persist beyond 3 months. HIV antigenaemia was found before HIV antibody seroconversion in 6 out of 55 (11%) and concomitant with HIV antibody seroconversion in 8 out of 55 (15%) subjects. A 'flu-like' illness that might be ascribed to primary HIV infection was found in 37 out of 50 men (74%). A blood sample was taken from 11 men during or within 2 weeks of the illness: no serological markers of HIV infection were detected in four subjects, HIV antigen, IgM and IgG anti-HIV were detected in another four, HIV antigen was the only marker of HIV infection in two subjects, and in one subject, IgM and IgG anti-HIV were detected but not HIV antigen. These results indicate that no conclusive value can be attached to a negative IgM test in suspected primary HIV infection, and that any role for IgM anti-HIV testing in blood donor screening is highly questionable.     

Viral gene expression, antibody production and immune complex formation in human immunodeficiency virus infection

Human immunodeficiency virus (HIV) antigen (HIV-Ag) in polyethylene glycol (PEG) precipitates and supernatants and HIV antibodies (HIV-Ab) to core and envelope antigens were studied in serial serum samples of three HIV-Ab seroconverters and 11 HIV-Ab seropositive men with a mean follow-up time of 16.1 months. In five men not progressing beyond persistent generalized lymphadenopathy (PGL) and two progressing to AIDS, HIV-Ag was detected once in 'free' configuration before HIV-Ab seroconversion and persistently or intermittently 'complexed' thereafter; in six of these men HIV core antibodies were continuously present with a declining level in one. In two men not progressing beyond PGL and five progressing to AIDS HIV-Ag was detected 'complexed' before HIV-Ab seroconversion once and persisted predominantly in 'free' configuration thereafter, while no HIV core antibody was detected in six of these men and a declining level in one. HIV-Ag was detected in 37% (14 out of 38) of HIV core antibody seropositive samples, mostly in 'complexed' form, while HIV-Ag was detected in 86% (43 out of 50) of HIV core antibody seronegative samples, mostly in both 'complexed' and 'free' configuration. Antibodies to HIV envelope antigen were detected in all HIV-Ab seropositive samples. These results indicate that the level of HIV-Ag expression is the primary determinant of detectability of HIV core antigens as well as antibodies. Enhancement of HIV-Ag expression, in a significant number of cases associated with clinical deterioration, appears to lead to clearance of HIV core antibodies in immune complexes, while HIV envelope antibody levels remain relatively unaffected.     

Antibody to hepatitis C virus in post-transfusion hepatitis.

OBJECTIVE: To evaluate the prevalence of antibodies to hepatitis C virus (anti-HCV), their relation to outcome, and the seroconversion rate in patients with post-transfusion non-A, non-B hepatitis. DESIGN: Retrospective analysis of prospectively collected serum specimens. SETTING: A referral-based university hospital. PATIENTS: Sixty-three consecutive patients who developed non-A, non-B post-transfusion hepatitis after open-heart surgery. All patients had follow-up with serial serum testing and clinical evaluation. The mean (+/- SD) duration of follow-up after hepatitis onset was 81 +/- 33 months (range, 13 to 132 months). Seventeen patients recovered after acute-phase illness, whereas 46 developed chronic disease which, in 30 cases, was confirmed histologically. MAIN RESULTS: Of 32 patients tested before transfusion, 1 (3.1%) had anti-HCV. Fifty-nine (93%) patients were anti-HCV positive during acute-phase hepatitis: Patients with "early" seroconversion (less than 15 days after hepatitis onset) did not differ from those with "late" seroconversion (greater than 60 days after onset) in epidemiologic, clinical, and biochemical features. The rate of anti-HCV positivity during acute-phase illness was not significantly different among patients who recovered (76%) compared with those who developed chronic disease (95%). At 6 to 12 months, patients whose disease resolved had lower antibody activity than those with progressive disease. Further, during long-term follow-up (1 to 9 years), 53% of patients whose disease resolved but only 6.9% of patients who had progressive disease became anti-HCV negative. CONCLUSIONS: Hepatitis C virus is the major cause of post-transfusion hepatitis in Italy. The time to anti-HCV seroconversion varies widely after hepatitis onset and is not significantly associated with acute-phase features or outcome of disease.     

GENSCREENULTRA HIV抗原抗体酶联免疫诊断试剂盒的敏感性评价

目的评价BIO-RAD公司开发研制的人类免疫缺陷病毒（HIV1＋2）抗原抗体酶联免疫诊断试剂盒（GENSCREEN~ ULTRA HIVAg-Ab）,对不同来源样本检测的敏感性。方法以法国生物梅里埃公司生产的HIV1＋2抗原/抗体ELISA检测试剂为参比试剂,分别使用评价试剂和参比试剂检测621例样本,分析两种试剂检测HIV抗原/抗体的敏感性。结果评价试剂和参比试剂检测502份HIV感染者/AIDS患者临床血浆标本均为阳性,符合率为100%,敏感性为100%。评价试剂和参比试剂检测92份HIV分离培养上清液,评价试剂检出89份阳性、参比试剂检出31份阳性,表明评价试剂检测HIV-1p24抗原的敏感性高于参比试剂。另外,又检测了27份HIV抗原系列稀释样本,计算出评价试剂检测HIV抗原的敏感性是参比试剂的4～8倍。结论评价试剂检测HIV抗体的效果与参比试剂相同,检测HIV-1p24抗原的敏感性高于参比试剂。     

The immunological and clinical outcome of HIV infection: 31 months of follow-up in a cohort of homosexual men

T-cell subsets, antibodies (Ab) against human immunodeficiency virus (HIV) and clinical status were evaluated during a 31 (24-35) month follow-up study of homosexual men. The study group included 50 homosexual men, with many sexual partners, who by 1982-83 were without symptoms and had a prevalence of HIV Ab of 38%. Among the men who were seropositive on the initial investigation a significant decrease occurred in the absolute number of CD4+ lymphocytes (p less than 0.01). 88% of these men experienced a decrease, and by follow-up 59% had CD4+ lymphocytes below the normal range. Also the men who seroconverted during the study had a significant decrease in CD4+ lymphocytes, while no changes were observed in the seronegative group. None of the subgroups had significant changes in CD8+ lymphocyte number. AIDS or AIDS related complex developed in 33% of the men seropositive at inclusion. None of these clinical syndromes developed in the seroconverting or the seronegative group. The men who eventually developed clinical symptoms did not differ significantly from the healthy HIV Ab positive persons, with respect to lifestyle parameters, presence of lymphadenopathy and isolation of cytomegalovirus. However, they had significantly lower CD4+ cells and CD4/CD8 ratio (p less than 0.01) at inclusion. It is concluded that in the majority of persons infected with HIV, phenotypic T-cell alterations will occur with a latency of years, but it remains to be seen if the alterations necessarily will result in clinical manifestations. Further, T-cell subset determination among healthy HIV Ab positive persons will provide prognostic information.     

ELISA、胶体硒和免疫试鸭验检测HIV抗体结果分析

目的 复检和确认初筛HIV抗体阳性血清，并对比分析试验结果。方法 对初筛阳性血清，用胶体硒和ELISA试验复检，任一复检试验阳性的血清再用westernblot（WB）试验确认。结果 224份初筛阳性血清经复检84份阳性，WB确认61份HIV—1抗体阳性，不确定10份，阴性13份。以WB结果为标准，ELISA、胶体硒法的阳性符合率分别为84．72％和82．43％。ELISA的敏感性为100％，特异性为96．84％，胶体硒法的敏感性为100％，特异性为95．03％。阳性、不确定和阴性组血清EI，ISA平均S／CO分别为20．550，2．244和1．434。ELISA和胶体硒法复检同时阳性，在阳性组、不确定组、阴性组分别为100％（61／61），10％（1／10）和0（0／13）。结论 胶体硒和ELISA复检可排除大部分初筛假阳性，但两种复检试验均存在一定的假阳性。3种试验的不符情况仅出现在HIV抗体阴性和不确定组，确定HIV感染依赖于WB确认试验。     

Evaluation of a sensitive/less-sensitive testing algorithm using the 3A11-LS assay for detecting recent HIV seroconversion among individuals with HIV-1 subtype B or E infection in Thailand

The development of a serologic algorithm to determine recent HIV seroconversion, using sensitive/less-sensitive testing strategies, has generated widespread interest in applying this approach to estimate HIV-1 incidence in various populations around the world. To evaluate this approach in non-B subtypes, longitudinal specimens (n = 522) collected from 90 incident infections among injecting drug users in Bangkok (subtype B infection, n = 18; subtype E infection, n = 72) were tested by the 3A11-LS assay. Standardized optical density (SOD) was calculated, using median values, and the window period between seroconversion as determined by sensitive and less sensitive tests was estimated by a maximum-likelihood model described previously. Our results show that the mean window period of the 3A11-LS assay was 155 days (95% CI, 128-189 days) for subtype B but was 270 days (95% CI, 187-349 days) for subtype E specimens from Thailand. About 4% of individuals with incident subtype E infections remained below the threshold (SOD of 0.75), even 2 years after seroconversion. Among the patients with clinical AIDS and declining antibodies, none of the 7 individuals with subtype B, but 10 (8.7%) of 115 with subtype E infections, were misclassified as recent infections. Lowering the cutoff to an SOD of 0.45 for subtype E specimens resulted in a mean window period of 185 days (95% CI, 154-211 days), with all individuals seroconverting, and reduced the number of subtype E-infected patients with AIDS who were misclassified as having recent infection to 2.6%. Our results demonstrate that the 3A11-LS assay has different performance characteristics in detecting recent infections among individuals infected with subtypes B or E. Determining appropriate cutoffs and mean window periods for other HIV-1 subtypes will be necessary before this approach can be reliably implemented in settings where non-B subtypes are common.     

Decline in CD4+ cell numbers reflects increase in HIV-1 replication

Changes in CD4+ cell numbers were studied in relation to the presence of HIV-1 antigen (HIV-1-Ag) in serum from homosexual men followed prospectively. During 30 months of follow-up the mean CD4+ cell number (x 10(9) per liter) was stable in 134 at entry HIV-1 antibody (HIV-1-Ab) seropositives, who remained HIV-1-Ag negative (from 0.59 to 0.62) and declined in 38 at entry HIV-1-Ab seropositives who were persistently HIV-1-Ag positive (from 0.43 to 0.34). In sera of 9 of 65 HIV-1-Ab seroconverters HIV-1-Ag was detected only once, 3 months before or concomitantly with antibody seroconversion. Another 11 men became persistently HIV-1-Ag positive with antibody seroconversion or 2-6 weeks thereafter. A decline in CD4+ cell numbers was seen between 6 months before and the moment of HIV-1-Ab seroconversion, independently of duration and level of antigen expression. This indicates initial HIV-1 replication in both HIV-1-Ag negatives and positives. Following antibody seroconversion, HIV-1-Ag negatives had higher CD4+ cell numbers than HIV-1-Ag positives. Similarly to those who were HIV antigenemic from entry of the study, the HIV-1-Ab seroconverters who concomitantly with seroconversion or shortly thereafter became HIV-1 antigenemic showed a steady and significant (p = 0.01) decline in CD4+ cell numbers. In those who remained HIV-1-Ag negative after antibody seroconversion, CD4+ cell numbers were stable during follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)     

Detection by immunofluorescence of a new “core-like” Ag/Ab system in liver and serum of patients with NANB hepatitis

ABSTRACT— Using direct immunofluorescence, a nuclear antigen was found in liver of chronic hepatitis patients with circulating NANBe Ag or anti-NANBe, and selected sera from either group were used as source of conjugates. The new Ag/Ab system was designated NANBc Ag and anti-NANBc since it behaved like the core Ag of HBV. N ANBc Ag was detected in coded frozen liver biopsies from patients with chronic persistent 15/25 (60 %) or active 27/50 (54 %) hepatitis and cryptogenic cirrhosis 16/30 (53.3%) devoid of HBV markers. Only 2/30 alcoholic cirrhosis cases (7%) used as controls were positive (p≤0.001). The homologous anti-NANBc antibody was always detectable by indirect immunofluorescence in the patients' serum when N ANBc Ag was found in the liver. It was also found in 11/135 (8%) additional cases without any other NANB marker. A correlation was observed between coded detection of the NANBc Ag/Ab system by immunofluorescence and demonstration of NANBe Ag or anti-NANBe by immunodiffusion. In acute post-transfusion NANB hepatitis, anti-NANBc was first detectable 14 days after transfusion and persisted as long as ALT remained elevated, or longer. IgM anti-NANBc present at onset became associated with an increasing proportion of IgG after the 28th day. The prevalence of anti-NANBc in sporadic NANB hepatitis (11/50 = 22%) was significantly lower (p≤0.001) than in cases with parenteral exposure such as post-transfusion, occupational or drug addict hepatitis (47/72 = 65%). Immunofluorescent tests for NANBc Ag and Ab are promising assays for the serological diagnosis of NANB hepatitis.     

Rapid confirmation of HIV infection.

OBJECTIVE: To investigate the utility of a prototype rapid confirmatory HIV assay which offers specific results in 5 min and has applications in a variety of important testing situations. METHODS: The performance of the rapid confirmatory assay was assessed with 849 blood samples, including serum, plasma, venipuncture whole blood, and peripheral blood collected via fingerstick. Included were over 700 HIV Western blot (WB)-confirmed antibody positive sera, and others which were classified as negative or indeterminate by WB. The analytic sensitivity of the rapid confirmatory assay was assessed using 13 HIV-1 seroconversion panels, and all results were compared to those of an FDA-licensed WB reference test. RESULTS: The rapid test exhibited 100% concordance with the reference test when testing HIV-1 WB-confirmed positive samples, and 92.3% concordance with samples having WB-inconclusive results. The sensitivity for confirming recent seroconversion was as good, or better than, the FDA-licensed HIV-1 WB in 10/13 panels. The rapid assay performed accurately with whole blood collected from fingerstick, and exhibited excellent precision and reproducibility. CONCLUSION: We conclude that this rapid HIV confirmatory assay, the first of its kind, demonstrates proof of principle for the accurate confirmation of HIV-1 infection and offers important advantages in public health and clinical testing venues.     

Investigation of a new HIV-1 p24 antigen detection kit based on the enzyme-linked fluorescent immunoassay

We investigated the performance of the new p24 antigen detection kit (VIDAS HIV p24) with the conventional antigen kit (HIV-1 Ag monoclonal; Abbott). The new kit is an enzyme-linked fluorescent immunoassay (ELFA) and all of the assay steps are performed automatically by the VIDAS instrument within 100 minutes. With the seven HIV-1 seroconversion panels, three seroconversions were detected on an average of 6.8 days earlier with ELFA than the conventional EIA kit. ELFA showed negative results for all of the 11 false positive samples by the combined (p24, anti-HIV) detection kit (VIDAS HIV DUO). The results obtained suggest that ELFA are very useful for an earlier diagnosis of HIV infection and re-test for false positive samples by other HIV diagnosis kits.     

Epidemiologic and virologic study of hepatitis C virus infections in Morocco

OBJECTIVES: We prospectively studied 783 consecutive Moroccan patients to define: 1) the prevalence of anti-hepatitis C virus (HCV) antibody (Ab), 2) the prevalence of other viral infections: HBs Ag, anti-HAV IgM, anti-HGV, HGV RNA, 3) the risk factors of spreading HCV infection, and 4) the distribution of HCV genotypes. RESULTS: 60/783 (7.7%) patients had anti-HCV Ab (48 H/12 F), 26 (3.3%) HBs Ag, and 3 (0.3%) IgM anti-HAV. Anti-HGV Ab was found in 11/60 (18.3%) anti-HCV positive patients, and 6/38 (15.8%) anti-HCV negative patients. 2/22 (9%) serum anti-HCV positive and anti-HGV negative patients were positive for HGV RNA. The 60 HCV positive patients rarely had other viral infections: 3 (5%) HBs Ag, 11 (18.3%) anti-HGV positive, 2 (9%) HGV RNA positive, and none had anti-HBc, IgM anti-HAV, or anti-HIV. HCV positive patients had more often undergone transfusion of blood products (21.7 vs 5.5%; P < 0.0001), and dental treatment (55% vs 8.3%; p < 0.0001). Patients with anti-HCV Ab frequently had hepatitis lesions on liver biopsy, i.e. chronic active hepatitis (n = 44) or cirrhosis (n = 16). HCV RNA was positive in 45/60 (75%) anti-HCV positive patients. HCV genotypes were: 1b (n = 21, 47%), 2a/2c (n = 13, 29%), 1a (n = 6, 13%), et 3 (n = 1, 2%). CONCLUSIONS: In our Moroccan population, the prevalence of HCV was high (7.7%). Other viral infections (HBV, HAV, HGV) were rare.     

Hemorrhagic sequelae of immune thrombocytopenic purpura in human immunodeficiency virus-infected hemophiliacs

Clinical bleeding tendency and tests of immune function were studied prospectively in 11 human immunodeficiency virus (HIV)-infected hemophiliacs with immune thrombocytopenic purpura (ITP) and a platelet count less than 50,000/microL. These 11 patients represented 13% of a well-characterized cohort of 87 HIV + hemophiliacs. ITP developed a mean 3.5 years after seroconversion, mean platelet count at presentation was 36,000/microL (range 15,000 to 49,000/microL), and the mean age at seroconversion was 37.1 years. Nine patients (82%) suffered bleeding complications, including four with intracranial hemorrhage, which was fatal in three. At the onset of ITP, five had AIDS and six were asymptomatic. Mean T4 lymphocyte count at onset of ITP was 126 +/- 32/microL (range 5 to 267/microL). Sustained treatment responses occurred with intravenous gammaglobulin (2 of 2), one of whom spontaneously remitted, and with zidovudine (1 of 2), but not with steroids (0 of 6) or danazol (0 of 3). In conclusion, 13% of a cohort of HIV + hemophiliacs has developed ITP with platelets less than 50,000/microL, a significant proportion of whom (82%) have experienced bleeding complications. It is recommended that treatment for ITP in HIV + hemophiliacs be instituted once the platelet count falls below 50,000/microL in order to avoid serious hemorrhagic sequelae.     

Levels of soluble CD8 antigen and circulating immune complexes in intravenous drug abusers: relationships to HIV antibody serology

A total of 36 intravenous drug abusers (IVDA) were studied for circulating immune complexes (CIC) and serum soluble CD8 antigen (sCD8). None had symptoms or signs of AIDS-related complex or AIDS. sCD8 levels were significantly higher in 18 patients who had HIV antibody (Ab) compared with 18 patients who were HIV Ab negative (1640 +/- 578 virus 804 +/- 264 U/ml, p less than 0.0001). In HIV Ab+ patients but not in HIV Ab- patients, sCD8 levels significantly correlated with percentages and absolute numbers of activated CD3+DR+ peripheral blood mononuclear cells (p = 0.0024 and 0.0183, respectively). Also in HIV Ab+ patients, CIC levels were significantly greater for both anti-C3 binding (13.1 +/- 11.1 versus 2.9 +/- 3.4 micrograms/ml, p = 0.002) and C1q binding (23.5 +/- 20.2 versus 6.3 +/- 4.3 micrograms/ml, p = 0.001) CIC. Serum C4 concentrations were lower in the HIV Ab+ patient group (33.9 +/- 10.1 versus 41.6 +/- 12.4 mg/dL, p = 0.043). In the seropositive group, IgG levels were higher (2206 +/- 859 versus 1615 +/- 645 mg/dl) and total CD4 cell counts were lower (757 +/- 344 versus 1172 +/- 402 cells per mm3), but at a less significant level (p = 0.024 and 0.005, respectively), than that seen for sCD8 and C1q CIC differences. These results suggest that elevations of both the lymphocyte activation marker sCD8 and antigen nonspecific CIC characterize earlier stages of HIV infection in IVDA.