Antigen Tests (p24)

“Among 37,164,054 units [of donated blood] screened, 12 were confirmed to be positive for HIV-1 RNA…only 2 of which were detected by HIV-1 p24 antigen testing”

“The p24 antigen test had specificity of 99.5%…[but] a lower sensitivity than HIV-1 RNA testing: 79%”

“HTLV-III [HIV] has been shown to be antigenically related to HTLV-I and HTLV-II by demonstrating cross-reactivity with antibodies to HTLV-I and HTLV-II core proteins, p24 and p19.”

“We did western blot tests for HIV-1…on serum samples from 77 patients with primary biliary cirrhosis, 126 patients with chronic liver disease, 48 patients with systemic lupus erythematosus, and 25 healthy volunteers. HIV-1 p24 gag seroreactivity was found in 27 (35%) of 77 patients with primary biliary cirrhosis, 14 (29%) of 48 patients with systemic lupus erythematosus, 14 (50%) of 28 patients with chronic viral hepatitis, and nine (39%) of 23 patients with either primary sclerosing cholangitis or biliary atresia, compared with only one (4%) of 24 patients with alcohol-related liver disease or alpha1-antitrypsin-deficiency liver disease, and only one (4%) of 25 healthy volunteers…The HIV-1…antibody reactivity found in patients with primary biliary cirrhosis and other biliary disorders may be attributable either to an autoimmune response to antigenically related cellular proteins or to an immune response to uncharacterised viral proteins that share antigenic determinants with these retroviruses. [Even though these are antibody tests, and this one antibody reaction does not result in an HIV diagnosis, this indicates that the protein known as p24 is not unique to HIV]”

“The sensitivity of p24 antigenemia was 59%”

“HIV-1 p24 antigen is present only transiently prior to seroconversion and later can be complexed by specific antibodies. HIV-1 p24 antigen testing should not be used in lieu of HIV-1 antibody testing as a screen for HIV-1 infection.”

“Routine testing for p24 antigen in settings other than blood and plasma centers as a method for diagnosing HIV infection is discouraged because the estimated average time from detection of p24 antigen to detection of HIV antibody is 6 days and not all recently infected persons have detectable levels of p24 antigen…p24-antigen tests alone should not be used for diagnosing HIV infection.”

“None of the 50 seronegative partners had p24 antigen in their serum. 22 (44%) of the seropositive partners had detectable p24 antigen.”

“p24 antigen was detected in 6 patients of group P [positive] and 2 patients of group N [HIV-negative].”

“At the time of delivery, HIV-1 p24 antigen was detected in serum from 16 of 108 [HIV+] women (15%)”

“In 81 (72%) of [HIV-]positive subjects p24 antigenaemia was found in subsequent checks for a median duration of 20 months. p24 antigenaemia was not associated with any clinical pattern.”

“There was no correlation between HIV-1 p24 antigen assay and syncytium [a special type of large cell with several nucleuses that is found only in cell cultures] formation assay results.”

“[The abstract states, without qualification, that] In the two didanosine groups, there were improvements in the number of CD4 cells and in p24 antigen levels, as compared with the zidovudine [AZT] group…[but later the paper states] Among the subjects initially positive for serum p24 antigen [fewer than half], significantly higher proportions of those in the 750-mg and 500-mg didanosine groups had p24 antigen levels that declined by at least 50%.”

“Of 61 infected children tested 46 (75%) had at least one positive test for antigen”

“Cryostat sections of human normal term placentae were …examined for HIV protein antigens gp120, p17, p24, and gp41. No evidence for gp41 was found. Antigens gp120 and p17 were identified in normal chorionic villi in vimentin-positive fibroblast-like cells and in endothelium, respectively. Antigen p24 was localized to HLA-DR positive cells that morphologically resembled macrophages in areas of villitis. [i.e. HIV proteins are found in uninfected human placentas!!]”

“HIV-1 p24 is the HIV-1 protein most prone to "false-positive" reactions”

“there were 16 sera from 30 viraemic patients which did not have detectable p24 antigen”

“there were 16 sera from 30 viraemic patients which did not have detectable p24 antigen (<5 pg/ml, Fig. 2). As a consequence, p24 antigen concentration and HIV-1 RNA did not correlate well.”

“The p24 antigen was negative in seronegative persons at high and low risk but positive in 6 of 92 HIV-1-seropositive individuals [who were also negative by DNA PCR]”

“Baseline serum p24 antigen levels were measured in 71 patients. At entry, 37 (52%) were positive for the antigen...and 34 (48%) were negative [yet all were positive for HIV antibodies]”

“of the children who got AIDS, 10 out of 13 (77%) had at least one position antigen test in the pre-AIDS period, compared with 20 out of 27 (74%) of antibody-positive infected children who did not get AIDS and who were followed for over 18 months”

“Of 515,494 donor samples tested for p24 antigen at the blood centers, 0.43% were initially reactive. Of these samples, only 18% were repeatedly reactive…Among the repeatedly reactive samples…retested at the central laboratory, 58% (representing 0.05% of the total population) were verified as repeatedly reactive.”

“205 subjects (of 406 tested (50%)) had detectable serum levels of HIV antigen before treatment [i.e. 50% were negative for HIV antigen, although positive for HIV antibodies]”

“lower levels of HIV p24 antigen…[was] significantly correlated with the risk of progression to AIDS”

“In only 45 percent of persons from whom we isolated plasma-associated HIV [by co-culture techniques] was p24 antigen detected in plasma or serum”

“no infants, including those who later had AIDS, were positive for serum antigen [p24] during the neonatal period”

“[4 frozen blood samples from DNCB-anergic seroconverters] were negative for p24 antigen”

“In comparison with antibody testing, antigen testing will only detect approximately 50% of AIDS, 30% of ARC [AIDS Related Complex] and 10% of asymptomatic HIV infections”

“The serum antigen assay [probably p24], carried out twice on each sample, was positive for 6 of the 21 (29%) samples from seropositive subjects…13 (76%) of the seventeeen HIV-DNA-positive subjects were negative for serum antigen”

“The HIV antigen [p24] test is probably not an adequate measure of infectivity…even though positive results are suggestive of high titres of circulating virus”

“The weak correlation between [erythrocyte sedimentation counts, which was correlated with progression to AIDS] and positive HIV antigenemia [positive p24 antigen test] is of interest”

“In a prospective study conducted from September 1993 through September 1995, a total of 305,989 donations were tested for p24 antigen; [1,348 were positive on the first p24 test, 144 of those were positive on at least 1 of 2 subsequent p24 tests and] 3 donors had both repeatedly reactive p24-antigen EIA screening-test results and positive neutralization results (two of whom were also HIV-antibody positive), and 223 donors had repeatedly reactive p24-antigen EIA screening-test results and negative neutralization results.”

“Whether the production of HIV antigen [p24 or p25] accurately reflects complete viral replication with the production of infectious virions is still to be investigated”

“Extensive accumulation of p24 and p41 occurred in the [HIV] virus preparation. Protein stains show that these molecules are the major components of the virus preparation. P24 and p41 may therefore be considered viral structural proteins [What? Just because there’s more of it, but no proof that it actually came from virus particles?]”