Diagnosis of HIV Infection Theodoros Kelesidis, MD, PhD Assistant Professor of Medicine Attending Physician Ronald Reagan Medical Center Division of Infectious Diseases David Geffen School of Medicine February 12, 2014

HIV in the U.S. An estimated 1,148,200 persons in the United States live with HIV About 50,000 new HIV infections occur in the United States each year Each year, approximately 16-22 million persons in the United States are tested for HIV An estimated 38%-44% of all adults had been tested for HIV Approximately 1 in 5 (18%, or 207,600 persons) do not know they are HIV-infected. US CDC, 2012 http://www.cdc.gov/hiv/resources/factsheets/us.htm

Why provide HIV testing? Earlier detection leads to improved treatment outcomes HIV-infection status awareness is associated with reduced transmission risk behavior HIV-infected persons on treatment are less infectious

Human Immunodeficiency Virus RNA virus Surface envelope proteins Matrix proteins Capsule proteins RNA

Evolution of HIV infection

HIV tests Detect human antibodies to surface, matrix and capsule proteins Detect HIV antigen p24 (a nucleocapsid protein) and gp 120 and gp 41 (envelope proteins). Detect viral nucleic acid (NAT) a) RNA b) DNA integrated within cells Viral culture in patient PBMC

HIV antibody tests Enzyme immunoassays (EIA) 1st generation—IgG anti-HIV antibodies 2nd generation—synthetic antigen + HIV-2 3rd generation—IgM and IgG anti-HIV antibodies 4th generation—p24 HIV antigen + IgM and IgG anti-HIV antibodies Western blot Immunofluorescent assay

What is an ELISA test? ELISA = Enzyme-Linked Immuno Sorbent Assay. This technique is based on the lock and key theory of antibodies. Antibodies and antigens work like locks and keys. One antibody fits one antigen. Having the antibody means the antigen is also present. ELISA technique involves placing HIV antigens (locks) on the bottom of a microwell cup The microwell is then filled with the serum to be tested. If the appropriate anti-HIV antibodies are present (keys), they will stick to the antigens (locks).

What is an ELISA test? Since antibodies are proteins too, they themselves are also antigens. Scientist developed an anti-HIV antibody antibody. So this new antibody sticks to the back of the first antibody. This second antibody has an enzyme is attached to it. When a reactive substrate is added to the mix, the enzyme will turn the substrate a different color (usually red). If the serum to be tested contains anti-HIV antibodies, the liquid in the microwell will turn red.

HIV 1st Generation Antibody test

Problems with HIV 1st Generation Antibody test It only detects antibodies to the HIV 1 virus, not HIV 2. It only detects the IgG antibodies which can take some time to be produced in the body up to levels which are detectable testing window period. The antigen purification from viral lysates was not very good high level of false positives need for confirmation by Western Blot

HIV 2nd Generation Antibody test Includes HIV-2 antigen Uses synthetic antigens  better antigen production techniques that improved the false positive rate Same problems with 1rst generation tests

HIV 2nd Generation Antibody test Rapid test OraQuick Rapid HIV-1/2 Antibody Test Clearview HIV 1/2 Stat Pak Reveal G3 Rapid HIV-1 Antibody Test Uni-Gold Recombigen HIV Test Multispot HIV-1/HIV-2 Rapid Test Clearview Complete HIV 1/2

HIV 3rd Generation Antibody test The method of 3rd generation of HIV ELISA test is double antigen sandwich Detect all kinds of antibody of HIV (including IgM) Improved sensitivity and specificity as well. The main laboratory-based diagnostic ELISA test worldwide now. The anti-HIV IgM antibody would attach to the antigens. Now the thing about the IgM antibody is that it is like many keys attached to each other. In other words there are multiple antigen binding sites. This is very different from IgG that has just 1 antigen binding site. So what the scientist figured out how to do was to stick the enzyme and a HIV antigen together. So this antigen-enzyme conjugate will stick onto the other binding sites of the IgM antibody that has stuck onto the antigens in the microwell. The enzyme on the antigen then converts the substrate color thus enabling detection. Since the IgM antibody is ‘sandwiched’ between 2 antigens, the name ‘sandwich ELISA’ was coined.

HIV 4th Generation Antibody test The method of 4th generation of HIV ELISA test is that HIV antigen and p24 antigen coat the vector simultaneously Detect the HIV P24 and HIV antibody in the sample at the same time. So, it could be used for detection for the samples of window period which shows positive in HIV P24 antigen tests but is not transformed into HIV infection. Not many people agree with this nomenclature because technically, it is identical to the 3rd generation ELISA test. Basically the 4th generation ELISA test is putting 2 different tests (i.e 3rd generation ELISA and P24 antigen test) onto the same test strip. Because the P24 antigen is produced even earlier than the IgM antibody, this reduces the testing window period even further

HIV Western blot Identifies antibodies against eight HIV-1 encoded proteins: p18, p24, p31, gp41, p51, p55, p65/66, gp120/p160. Criteria require antibodies against any two of the following HIV-1 proteins: p24, gp41, gp120/160. Specimens showing reactivity to HIV-1 protein(s), but not fulfilling the criteria for a positive result, are reported as Indeterminate. All indeterminate Western blots are further tested in supplemental HIV-1 and HIV-2 specific assays. A negative Western blot has no detectable bands, i.e. no antibodies reacting to either HIV-1 or non-HIV-1 proteins.

Reasons for false negative results Acute infection Failure to detect certain HIV subtypes EIAs in USA and Europe detect all M subtypes but do not consistently detect other groups (O, P) 4th generation can detect O subtypes more reliably The newly detected P subgroup can be detected only with nucleotide sequencing Immune dysfunction due to immunosuppression (e.g medications, malignancy) Delay in seroconversion following early initiation of antiretroviral therapy Fulminant HIV infection e.g presentation with OIs like PCP  

Reasons for indeterminate results Indeterminate tests usually result from a positive EIA and a single band on Western blot (usually p24). Causes of indeterminate results include partial seroconversion during acute HIV infection advanced HIV infection with decreased titers of p24 antibodies infection with HIV-2. Cross-reacting alloantibodies from pregnancy Autoantibodies (collagen-vascular diseases, autoimmune diseases, and malignancy) Receipt of an experimental HIV-1 vaccine Influenza vaccination  

HIV Immunofluorescent assay In an IFA test, HIV antigen is mixed with a fluorescent compound and then with a sample of the patient's blood. If HIV antibody is present, the mixture will fluoresce when examined under ultraviolet light.

HIV-RNA Qualitative Test Used to diagnose HIV infection Resolve indeterminate HIV-antibody results Diagnosis of neonatal HIV infection, in patients with indeterminate serologic tests, or in those who may be in the "window period" of HIV seroconversion HIV PCR  RNA – virus. DNA – pro-virus. There is more data for using the RNA as a diagnostic test. Also, RNA is detectable earlier than DNA

HIV-RNA Quantitation Used to monitor antiviral therapy and to predict disease progression in HIV infected persons. In conjunction with a positive DNA PCR or a reactive EIA, the RNA quantitation may be diagnostic. High levels of RNA are found during acute infection and in patients who are more likely to have disease progression. Inhibition of cell-free HIV, as reflected by RNA copy number, is associated with better CD4 response and clinical response in some patient populations. The dynamic range for HIV RNA detection by Real-Time PCR is 30 to 1,000,000 copies/mL of plasma. Often use in newborns and infants for early diagnosis

HIV-1 Proviral DNA Detection The detection of cell associated Human Immunodeficiency Proviral DNA by polymerase chain reaction (PCR) amplification is one of the most sensitive non-serologic methods for confirming HIV infection. This assay is recommended for confirming HIV infection in the neonate. HIV DNA PCR may also be used as a supplemental test to determine the significance of an indeterminate HIV Western Blot serology result.

HIV-1 Culture Culture is an extremely sensitive virologic method for documenting HIV infection, especially in neonates whose serologies are complicated by the presence of maternal antibody

HIV-1 Genotypic Resistance Assay The assay involves sequencing of the HIV pol gene, after which mutations in the gene can be compared to sequences known to confer resistance to different classes of antiretroviral drugs. The assay is most useful in patients who lose viral suppression on antiretroviral therapy and should be performed before switches in therapy are entertained.

Case 1 30 year old bisexual man comes into clinic He has had 15 lifetime partners, never been HIV-tested What test is appropriate?

Case 2 22 year old man who has sex with men, methamphetamine user Last tested HIV-negative 6 months ago History of syphilis What test is appropriate?

Case 3 46 year old man diagnosed with HIV-infected 6 years ago Has been on treatment for 3 years but has not had a check up in a year What test is appropriate?

Case 4 17 year old girl had a rapid HIV test that was positive She comes to clinic for testing What test is appropriate?

Case 5 17 year old girl had a rapid HIV test that was positive The ELISA test was indeterminate What test is appropriate?

Case 6 47 year old man has been on treatment for years but ran out of meds 1 year ago. About 6 months ago he restarted 2 medications he obtained from his partner. He has been losing weight and complains of fatigue and fevers What test is appropriate?

Case 7 6 week baby had an HIV-infected mother The mother receive treatment during pregnancy What test is appropriate for the baby?

Thank You tkelesidis@mednet.ucla.edu