Quantitative detection of increasing HIV type 1 antibodies after seroconversion: a simple assay for detecting recent HIV infection and estimating incidence.
We have devised a simple enzyme immunoassay (EIA) that detects increasing levels of anti-HIV IgG after seroconversion and can be used for detecting recent HIV-1 infection. Use of a branched peptide that included gp41 immunodominant sequences from HIV-1 subtypes B, E, and D allowed similar detection of HIV-specific antibodies among various subtypes. Because of the competitive nature of the capture EIA, a gradual increase in the proportion of HIV-1-specific IgG in total IgG was observed for 2 years after seroconversion. This was in contrast to results obtained with the conventional EIA using the same antigen in solid phase, which plateaus soon after seroconversion. The assay was used to test 622 longitudinal specimens from 139 incident infections in the United States (subtype B) and in Thailand (subtypes B and E). The assay was also performed with an additional 8 M urea incubation step to assess the contribution of high-avidity antibodies. Normalized optical density (OD-n) was calculated (ODspecimen/ODcalibrator), using a calibrator specimen. An incremental analysis indicated that a cutoff of 1.0 OD-n and a seroconversion period of 160 days offered the best combination of sensitivity and specificity for classifying incident or long-term infections. The urea step increased the seroconversion period to 180 days with similar sensitivity and specificity. Separate analysis of B and E subtype specimens yielded the same optimal OD-n threshold and similar seroconversion periods. The assay was further validated in African specimens (subtypes A, C, and D) where the observed incidence was within 10% of the expected incidence. This assay should be useful for detecting recent HIV-1 infection and for estimating incidence among diverse HIV-1 subtypes worldwide.
Parekh
Bharat S
BS
Division of AIDS, STD, TB Laboratory Research, and Division of HIV/AIDS Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA. bparekh@cdc.gov
Kennedy
M Susan
MS
Dobbs
Trudy
T
Pau
Chou-Pong
CP
Byers
Robert
R
Green
Timothy
T
Hu
Dale J
DJ
Vanichseni
Suphak
S
Young
Nancy L
NL
Choopanya
Kachit
K
Mastro
Timothy D
TD
McDougal
J Steven
JS
D015492:AIDS Serodiagnosis / Q000379:methods*; D000595:Amino Acid Sequence; D002138:Calibration; D015483:HIV Antibodies / Q000097:blood*; D015700:HIV Envelope Protein gp41 / Q000737:chemistry; D015658:HIV Infections / Q000175:diagnosis* / Q000453:epidemiology / Q000276:immunology; D015497:HIV-1 / Q000276:immunology*; D006801:Humans; D007124:Immunoenzyme Techniques / Q000379:methods; D015994:Incidence; D008969:Molecular Sequence Data; D012680:Sensitivity and Specificity
D015483:HIV Antibodies; D015700:HIV Envelope Protein gp41