HIV-1/HIV-2 Plus O EIA

The Alinity s HIV Ag/Ab Combo assay is a chemiluminescent microparticle immunoassay (CMIA) used for the simultaneous qualitative detection of human immunodeficiency virus (HIV) p24 antigen and antibodies to HIV type 1 (HIV-1 group M and group O) and/or type 2 (HIV-2) in human serum and plasma specimens on the Alinity s System.

The Alinity s HIV Ag/Ab Combo assay is intended to screen individual human donors, including volunteer donors of whole blood and blood components, and other living donors for the presence of anti-HIV-1/HIV-2 and HIV-1 p24 antigen. The assay is also intended for use in testing serum and plasma specimens to screen organ donors when specimens are obtained while the donor’s heart is still beating, and in testing serum specimens to screen cadaveric (non-heart-beating) donors. It is not intended for use on cord blood specimens.

About HIV

Acquired immunodeficiency syndrome (AIDS) is caused by 2 types of human immunodeficiency viruses, HIV type 1 (HIV-1) and HIV type 2 (HIV-2). Collectively, these 2 types of human immunodeficiency virus are designated HIV.1-4 HIV is a major global health issue, accounting for more than 35 million deaths globally to date. An estimated 36.9 million people are living with HIV, and each year 1.8 million people are newly infected and 940 000 people die globally.⁵ HIV is a member of the genus lentivirus in the family Retroviridae.^{1, 2, 6} Retroviruses use a viral encoded reverse transcriptase to transcribe viral RNA into DNA. The use of an error prone reverse transcriptase for viral replication leads to high mutation rates and recombination which are the drivers of HIV genetic diversity.^{6, 7}

HIV-1 is classified into 4 groups: M (major), N (non-M, non-O), O (outlier), and P.8-12 HIV-1 group M is composed of genetic subtypes (A, B, C, D, F, G, H, J, and K), circulating recombinant forms (CRFs), and unique recombinant forms (URFs).^{7, 10, 13}

HIV-1 group M viruses have spread throughout the world to cause the global AIDS pandemic. However, the geographic distribution and regional predominance of HIV-1 subtypes, CRFs, and URFs vary.^{13, 14} HIV-1 subtype B is globally widespread in most parts of the world.13-15 The prevalence of non-subtype B strains is on the rise across the USA, and a significant percentage of new HIV-1 infections in Europe are caused by non-B subtype strains.^15-17 HIV-1 groups N, O, and P are endemic to west central Africa and are relatively

rare.^{8, 9, 11, 12, 18, 19} However, group O infections have been identified in Europe and the USA.^{17, 20, 21} HIV-2 is similar to HIV-1 in its structural morphology, genomic organization, cell tropism, in vitro cytopathogenicity, transmission routes, and ability to cause AIDS.4 HIV-2 is composed of 8 genetic subtypes (A, B, C, D, E, F, G and H).²²

HIV-2 infections have lower transmission rates, lower viral titers, and a longer latency period with slower disease progression than HIV-1.²³ HIV-2 is endemic to West Africa, and international spread has been limited.^23-25 HIV-2 infections have been identified in North America and Europe at a low prevalence compared to HIV-1.^{17, 23-25}

HIV is transmitted by sexual contact, exposure to blood or blood products, and prenatal or perinatal infection of a fetus or newborn.²⁴ During early infection, the first marker to be detected in HIV infected individuals is the HIV RNA followed several days later by the HIV-1 core protein p24 antigen. Several days after the appearance of the HIV-1 p24 antigen, antibodies against HIV are detectable.²⁶ HIV RNA levels peak prior to antibody seroconversion, and then decline to steady state levels. HIV-1 p24 antigen levels also peak prior to seroconversion and then become undetectable consistent with the immune complexing of the antigen with the emerging antibodies.²⁶ After seroconversion, antibodies against HIV are nearly always detected in HIV infected asymptomatic individuals and AIDS patients.^{26, 27}

HIV antigen and antibody combination assays are used to identify individuals infected with HIV and to prevent transmission of the virus to recipients of blood, blood components, cells, tissues, and organs. In addition, these assays are used as an aid in the diagnosis of HIV infection. Alinity s HIV Ag/Ab Combo uses HIV-1 p24 antibodies as reagents to detect HIV-1 p24 antigen prior to seroconversion, thereby decreasing the seroconversion window and improving early detection of HIV infection. The assay also detects antibodies to HIV-1 groups M and O, and HIV-2.

This assay is a two-step immunoassay for the qualitative detection of HIV-1 p24 antigen, antibodies to HIV-1 (group M and group O), and/or antibodies to HIV-2 in human serum and plasma using chemiluminescent microparticle immunoassay (CMIA) technology. Sample, HIV-1/HIV-2 antigen and HIV-1 p24 antibody (mouse IgG, monoclonal) coated paramagnetic microparticles, and assay diluent are combined and incubated. The HIV-1 p24 antigen and HIV-1/HIV-2 antibodies present in the sample bind to the HIV-1/HIV-2 antigen and HIV-1 p24 antibody coated microparticles. The mixture is washed.

HIV-1 antigens, HIV-1/HIV-2 synthetic peptides, and HIV-1 p24 antibody acridinium-labeled conjugate is added to create a reaction mixture and incubated. Following a wash cycle, Pre-Trigger and Trigger Solutions are added. The resulting chemiluminescent reaction is measured as relative light units (RLU). There is a direct relationship between the amount of HIV antigen and/or antibodies in the sample and the RLU detected by the system optics.

The presence or absence of HIV-1 p24 antigen and/or HIV-1/HIV-2 antibodies in the sample is determined by comparing the chemiluminescent RLU in the reaction to the cutoff RLU determined from an active calibration.

Test performed by Eurofins DPT, 6933 S. Revere Parkway, Centennial, CO 80112.

This test has been cleared or approved for diagnostic use by the U.S. Food and Drug Administration. See package insert for more information.