The Changing Landscape of HIV Testing. Patricia Slev, PhD, D(ABCC) June 21, 2012

Transcription

1 The Changing Landscape of HIV Testing Patricia Slev, PhD, D(ABCC) June 21, 2012

2 Disclosure The speaker has nothing to disclose

3 Objectives Explain the principles and benefits of Ag/Ab combination HIV screening assays. Describe the new CDC HIV diagnostic algorithm. Understand the limitations of Western blot confirmation. Use screening and follow-up confirmatory tests appropriately.

4 Global HIV Epidemiology 1.3 million 0.23 million 1.6 million 0.76 million 0.38 million 22.5 million 1.6 million 0.80 million 4 million million WHO, UNAIDS. 07 AIDS epidemic update. Adapted from Siemens slide

5 Awareness of Serostatus Among People with HIV and Estimates of STD Transmission (US) ~25% Unaware of Infection Account for: ~54-70% of New Infections ~75% Aware of Infection ~30-46% of New Infections Marks et al. AIDS 2006 People Living with HIV/AIDS: 1,039,000-1,185,000 New Sexual Infections Each Year: ~32,000

6 CDC: Revised HIV Screening Recommendations

7 2006 CDC Guidelines Universal Testing Routine HIV voluntary, not based on risk Opt-Out option to decline, general consent for care includes HIV testing Prevention Counseling no longer required Population years old Venue inpatient services, ER, urgent care, STD clinics, substance abuse and correctional facilities

8 HIV Screening: American College of Physicians-2009 Screen all patients 13 years and older for HIV Retest high risk patients (per physician perception of need) Importance of screening pregnant women

9 Human Immunodeficiency Virus (HIV) Adapted from Siemens slide

10 HIV Types HIV-1 HIV-2 Groups Main New Outlier Subtypes Circulating Recombinant Forms (CRF)

11 HIV Distribution HIV-2 HIV O,N Francine E. McCutcham, Henry M. Jackson Foundation (Rockville, Maryland). IAVI Report, August 2003

12 Organization of HIV-1 RNA

13 Organization of HIV-1 RNA Reverse transcriptase

14 Organization of HIV-1 Capsid (p24) Reverse transcriptase

15 Organization of HIV-1 Lipid membrane gp41

16 Organization of HIV-1 gp41 gp120

17 Organization of HIV-1 gp120 gp160

18 Organization of HIV-2 gp105 gp36 HIV-2 causes AIDS but disease progression is slower, virus is less fit, and does not respond to certain drugs used to treat HIV-1 infection ada Adapted from Siemens slide

19 HIV Infection Course CD4+ count (cells/mm3) Primary infection Acute HIV syndrome Clinical latency CD4 Viral load (thousands) Viremia AIDS Weeks Years Adapted from Roche and Siemens slides

20 HIV Serological Response Typical response following infection 1 HIV p24 Antigen gag anti-hiv env anti-hiv pol anti-hiv HIV p24 Antigen Weeks following infection years

21 HIV Diagnostic Algorithm Screen traditional EIA/CIA rapid tests Confirmation Western blot (98%) IFA Prognosis and monitoring viral load nucleic acid amplification test (NAAT) Note: APTIMA, Genprobe (TMA format) approved in 2006 for diagnosis and confirmation

22 Immunoassay Generations IgG 1 st viral lysate IgG 2 nd recombinant /synthetic peptides HIV-2 +/- IgG IgM 3 rd HIV-2, O IgG 4 th IgM p24 antigen Immunology.Roit.1985 (IgG &I gm)

23 US FDA-Cleared Rapid Antibody Tests

24 Rapid Test Sensitivity Multispot Statpak Unigold Recombigen OraQuick HIV-1/2/0-3 rd gen(genetics Systems) Western Blot Louie B, et al. Assessment of Rapid Tests for Detection of Human Immunodeficiency Virus-Specific Antibodies in Recently Infected Individuals. Journal of Clinical Microbiology.2008

25 OraQuick Advance Synthetic gp-41 (HIV-1) Synthetic gp-36 (HIV-2) Goat anti-human IgG Photograph from CDC:

26 OraQuick Advance - Fingerstick Obtain a finger stick specimen Insert loop into vial and stir Photographs from CDC:

27 OraQuick Advance Oral Fluid Photographs from the CDC: Collect oral fluid specimens by swabbing gums with test device.

28 OraQuick Advance Photograph courtesy of the CDC:

29 Interpreting Results Reactive Control Positive HIV-1/2 Photograph from CDC:

30 Multispot HIV-1/HIV-2 Rapid Test Reactive Control HIV-1 HIV-1 Negative HIV-2 Reactive (HIV-1 & HIV-2) Detects and differentiates between HIV-1 and HIV-2

31 3 rd Generation Anti-HIV Assays Platforms ADVIA Centaur EHIV 1/2/0 (Siemens) Ortho VITROS anti-hiv 1 +2 Bio-Rad GS HIV-1/HIV-2 Plus O EIA Characteristics enzyme immunoassay (EIA) / (CIA) detect HIV infection at 22 days detect HIV 1/2 and O infection(depending on assay) detect HIV anti- HIV IgG and IgM antigen bridging assay format

32 Antigen Bridging Assay Format gp 41 Ag IgG/M High affinity Ag AE gp 41 AE p 24 Ag IgG/M High affinity Ag p 24 AE gp 36 Ag IgG/M Low affinity Ag gp 36 O peptide Ag IgG/M Low affinity Ag AE O peptide Adapted from Siemens slide

33 Serologic Detection of HIV Infection: 3 rd gen Relative concentration RNA (viral load) 3 rd gen HIV IgG HIV IgM HIV-1 infection years weeks months

34 Antigen/Antibody Combo (4 th Generation) HIV Detects both anti-hiv 1 and 2 antibodies and p24 antigen Does not distinguish between Ab+ or Ag+ Detects both HIV-1 and HIV-2, but does not discriminate 1 st FDA approved June 2010 (Abbott Diagnostics Architect Platform) 2 nd FDA approved July 2011 (Bio-Rad, manual or semiautomated) Improved detection of Acute HIV Testing Algorithm?

35 Antigen/Antibody Combination Assay Format Bentsen et al. Journal of Clinical Virology. 2011

36 Serologic Detection of HIV Infection: 4 th gen Relative concentration RNA (viral load) p24 4 th gen HIV IgG HIV IgM HIV-1 infection weeks months years Detects infection at weeks, 5 days earlier than 3 rd gen

37 Confirmation for HIV-1 Infection All repeatedly reactive EIA/CIA screening assay results must be confirmed POC results are considered preliminary positive results and must also be confirmed Confirmation for HIV-1 Infection Indirect Immunofluorescence (IFA) Western Blot

38 Western Blot HIV Antigens 5 RNA 3 gag sor env pol tat orf p 40/55 p65/51 p31 gp160 p18 p24 gp41 gp120

39 Western Blot Pattern Interpretations Nine characteristic HIV antibody bands Cardinal: p24, gp41, and gp120/160 (combined) Noncardinals: p18, p31, p51, p55, p65 Positive = at least 2 of the 3 cardinals Negative = no bands present (FDA criteria) Indeterminate = anything that does not meet + or interpretation p18 p24 p31 p40 p55 gp 120 HIV bands gp41 p65 gp160

40 False Positive Immunoassay Results Vaccinations flu, rabies HIV vaccine trials Autoimmune disease Liver disease Undefined cross reactivity

41 Western Blot Indeterminate Indeterminate results may be due to infected but in the window advanced disease, AIDS HIV vaccinated infected with HIV-2 uninfected, cross reactivity viral or non-viral bands, recent flu and rabies vaccinations, multiple pregnancies, recipients of multiple transfusions, autoimmune disease study followed 99 blood donors 91 stable indeterminate Western blot patterns over 30 months Indeterminate results require follow-up repeat Western blot NAAT

42 HIV-2 Testing Persons at risk for HIV-2 infection include Sex partners of a person from a country where HIV-2 is endemic Sex partners of a person known to be infected with HIV-2 People who received a blood transfusion or a nonsterile injection in a country where HIV-2 is endemic People who shared needles with a person from a country where HIV-2 is endemic or with a person known to be infected with HIV-2 Children of women who have risk factors for HIV-2 infection or are known to be infected with HIV-2 HIV-2 testing also is indicated for People with an illness that suggests HIV infection (such as an HIV-associated opportunistic infection) but whose HIV-1 test result is not positive People for whom HIV-1 Western blot exhibits the unusual indeterminate test band pattern of gag (p55, p24, or p17) plus pol (p66, p51, or p32) in the absence of env (gp160, gp120, or gp41) CDC

43 Sensitivity of HIV Assays

44 Detecting HIV Infection and Current Assays Masciotra et al. Journal of Clinical Virology 2011.

45 HIV Algorithms

46 Current Algorithm Issues Detecting Acute HIV infection increased sensitivity with 4 th gen, Ag/Ab Combo Western Blots insensitive compared to current screening assays indeterminate/inconclusive Diagnosing HIV-2 infection

47 CDC Proposed Algorithm

48 Acute HIV Detection Masciotra et al. Journal of Clinical Virology 2011.

49 HIV-1 vs HIV-2 and Western Blot Nasrullah et al. Journal of Clinical Virology 2011.

50 HIV-2 Infection Misclassification by Western Blot Nasrullah et al. Journal of Clinical Virology 2011.

51 GS Ag/Ab Combo and Long Standing HIV Infection Bentsen et al. Journal of Clinical Virology 2011.

52 Acute HIV and GS HIV Combo Ag/Ab Bentsen et al. Journal of Clinical Virology 2011

53 GS HIV Combo Ag/Ab Specificity Bentsen et al. Journal of Clinical Virology 2011.

54 Architect Ag/Ab Combo Chavez et al. Journal of Clinical Virology 2011

55 Multispot Torian et al. Journal of Clinical Virology 2011.

56 Comparison of Algorithms Masciotra et al.journal of Clinical Virology 2011.

57 CDC Proposed Algorithm

58 New Algorithm Benefits Increased detection of acute HIV infection Ag/Ab Combo Assay NAAT confirmation of acute HIV infection Eliminate inconclusive/indeterminate results eliminating the Western Blot Decrease turn around time & linkage to care replacing Western blot with Multispot Increased detection of HIV-2 infection replacing Western blot with Multispot

59 New Algorithm Challenges Only two platforms currently available for Ag/Ab Combo assays Multispot is a rapid test, originally approved as a screening assay There is only one qualitative molecular assay approved for HIV diagnosis (Aptima) that is not widely available and not automated Quantitative or viral load HIV assays are widely utilized but none is approved for diagnosis If a laboratory is using an antigen/antibody combo assay for screening then confirmation by Western blot is insufficient because it only detects anti-hiv antibody

60 Thank you!