Low HIV-1 proviral DNA burden detected by negative polymerase chain reaction in seropositive individuals correlates with slower disease progression.

During 1989, 316 members of a cohort of homosexual men were tested for HIV-specific DNA by the polymerase chain reaction (PCR) using a pair of gag-region primers. Of 125 HIV-seronegative subjects, 123 (98.4%) were PCR-negative while 158 (82.7%) of 191 HIV-seropositive subjects were PCR-positive. Fewer of the 33 subjects who were seropositive and PCR-negative were at Centers for Disease Control (CDC) stage IV than the seropositive, PCR-positive subjects (6 versus 25%; P = 0.030). The seropositive, PCR-negative group had higher mean CD4 counts (640 versus 490 x 10(6) cells/l; P = 0.006), higher CD4: CD8 ratios (0.92 versus 0.64; P = 0.004), lower immunoglobulin (Ig) G levels (1290 versus 1645 mg/dl; P = 0.002), lower IgA levels (168 versus 251 mg/dl; P less than 0.001), and lower C1q binding activity (8 versus 14%; P = 0.010) than the seropositive, PCR-positive subjects. The median rate of CD4 cell decline in the 3 years preceding the PCR sample was less marked in the seropositive, PCR-negative group than the seropositive, PCR-positive group (-58 versus -77 x 10(6) cells/l per year; P = 0.028). To control for duration of infection, we restricted the analysis to the subgroups of 11 seropositive, PCR-negative subjects and 34 seropositive, PCR-positive subjects who had seroconverted earlier in the cohort study. Both subgroups had similar durations of infection, yet the same pattern of differences persisted.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of a human immunodeficiency virus test algorithm utilizing a recombinant protein enzyme immunoassay.

Many truly human immunodeficiency virus (HIV) antibody-negative serum samples may be unnecessarily subjected to costly and time-consuming Western blots (immunoblots). An investigation was undertaken to evaluate the efficiency of using a recombinant protein-based enzyme immunosorbent assay (EIA; Cambridge BioScience [CBC] Recombigen HIV EIA) as an adjunct to whole viral lysate EIA. A total of 2,212 serum samples which had been screened by viral lysate EIA were tested by CBC EIA in parallel with the Western blot. The sensitivity and specificity of the CBC kit were 99.9 and 99.7%, respectively. Positive and negative predictive values were 99.7 and 99.9%, respectively. The high sensitivity of this kit and its high negative predictive value make it an attractive addition to an HIV testing algorithm by reducing the number of Western blot tests on truly antibody negative serum samples.

Laboratory diagnosis of the first cases of HIV-2 infection in Canada.

Until recently the geographic distribution of infection due to human immunodeficiency virus type 2 (HIV-2) had excluded North America. We report the first two cases of such infection in Canada. Both people came from endemic areas of western Africa and were asymptomatic. The results of a commercial enzyme immunoassay specific for HIV-1 antibody were positive in both cases, but those of the Western blot technique were indeterminate. The Western blot technique specific for HIV-2 antibody and the indirect fluorescent antibody test were used to verify the presence of HIV-2 antibody.

HTLV-III infection in Canada in 1985.

More than 25 000 serum specimens have been tested for antibody to human T-lymphotropic virus type III (HTLV-III) at the Laboratory Centre for Disease Control, Ottawa, since August 1984. In 1985 the prevalence rates of antibody positivity among selected risk groups were as follows: patients with Kaposi's sarcoma, 77%; patients with acquired immune deficiency syndrome (AIDS) or AIDS-related complex (ARC), 66%; patients with hemophilia, 65%; symptomatic homosexual men, 48%; cohabitants of patients with AIDS, ARC or antibody to HTLV-III, 24%; and intravenous drug abusers, 13%. No case of accidental parenteral exposure has resulted in seroconversion. Eight cases of AIDS, all in antibody-positive patients, have been associated with blood transfusions. A testing protocol based on risk-group information is proposed for diagnostic laboratories.

Comparison of measles antihemolysin test, enzyme-linked immunosorbent assay, and hemagglutination inhibition test with neutralization test for determination of immune status.

Sera were collected from 238 high-school students in Prince Edward Island for the determination of immune status before an anticipated measles outbreak. In addition, history of vaccination status and measles infection was obtained. In the subsequent outbreak, 28 students did contract measles. Specificity for hemagglutination inhibition (HI), antihemolysin (AH), and enzyme-linked immunosorbent assay (ELISA) was 100%, compared with the neutralization test. Corresponding sensitivity values for the tests were 66.0% (HI), 99.5% (AH), and 99.0% (ELISA). Predictive values for susceptibility were 26.9% (HI), 77.8% (AH), 75.7% (ELISA), 80% (neutralization), and 41.4% as determined by history of infection or vaccination. The predictive value for immunity as determined by history of previous infection or vaccination was 91.8%, compared with 100% for the four serological tests. No false-positive results were seen with any of these tests. Compared with the neutralization test, the HI test had 69 false-negative results, the AH had 1, and the ELISA test had 2. The AH and ELISA tests provided sensitive and specific alternatives to the commonly used HI test for immune status determination.

Single radial hemolysis test for rubella immunity and recent infection.

The single radial hemolysis (SRH) test was compared with the hemagglutination inhibition (HI) test for establishing rubella immune status and diagnosing recent infection. Correlation between mean SRH diameters and HI titers greater than or equal to 1:8 was high (R = 0.99). It is suggested that a level of greater than or equal to 5 IU represents low-level antibody and that greater than or equal to 15 IU is a conservative threshold for designation of immunity. Of 343 sera tested, only 1 false-positive was found by SRH with the 5 IU cutoff level. The SRH test could detect serum antibody levels as low as 2.5 IU, whereas 15 IU was generally the limit of resolution of the HI test. Data from sucrose density gradient fractionation of serum demonstrated that neither rubella-specific immunoglobulin M (IgM) nor early postinfection HI-reactive IgG was detected by SRH. However, diagnostic changes in antibody titer measured by SRH were in general greater than those measured by HI. The SRH test showed diagnostic titer changes in some sera containing specific IgM for which no such changes were detected by the HI test. A 2.5-mm difference in hemolytic zone diameters (a fourfold rise in international units) between acute- and convalescent-phase serum pairs was chosen as being of diagnostic significance. This difference was less than the minimum observed difference of 2.9 mm from 59 serum pairs showing diagnostic changes by HI and far exceeded (greater than 3.6 standard deviations) the within-test and individual variability seen for 95 pregnant women from whom samples were obtained during each trimester.