# Presentation: 359821

## The Impact of HIV Vaccines and Rapid Tests on the Laboratory Diagnosis of HIV

**National Laboratory Training Network**
**12  March 2002**

- Nelson L. Michael, M.D, Ph.D.

## Acknowledgment

**Dr. Merlin Robb (rapid testing/Uganda; vaccine)**
**Dr. Jerome H. Kim (vaccine)**
**Hassan Zahwa (rapid testing)**
**Jennifer Malia (vaccine; rapid testing)**

## The Impact of HIV Vaccines on the Laboratory Diagnosis of HIV

## Molecular diagnostics (NAT)Challenges to the serodiagnostic algorithm

## Impact of HIV Vaccine Developmenton HIV Diagnosis

**Preventive HIV vaccines development is a public health imperative.**
**Number of uninfected volunteers exposed to experimental HIV vaccines is ********.**
**Complexity of HIV immunogens is ********.**
**“****Reservation” of HIV epitopes for serodiagnosis confounds vaccine development and is the wrong approach.**

## Impact of HIV Vaccine Developmenton HIV Diagnosis, cont..

**HIV diagnostic laboratories will be increasingly asked to distinguish HIV infection from serologic response to HIV vaccines = molecular diagnostics/nucleic acid testing (NAT).**
***We need to be ready.***

## Western blots from subjects with chronic HIV infection are “screaming hot”*

**Mandell, 4th Ed, Churchill**
**Livingstone, NY1995**

***RADM C. Schable**

## HIV-1 genomic organizationVaccine antigen complexity 

## Why not delete portions of HIV genes incorporated into HIV vaccines to “reserve” epitopes that would only be seen in natural HIV infection?

## Reservation of HIV epitopes for serodiagnosis is a faulty strategy

**Natural immune response to infection is disease delaying.**
**Vaccine development is hindered by imperfect understanding of the protective cellular and humoral immune response.**
**Make the best vaccine possible.**
**Let testers like us figure out how to diagnose in this setting.**

## Hypothesis:Complexity (valence) of HIV-1 antigens in experimental vaccines positively correlates with the broadness of induced Western blot reactivities

## Vaccine constructs

**Subunit**
**gp120 and gp160**
**ALVAC (canarypox vector)**
**vCP65 (rabies placebo)**
**vCP125 (gp160)**
**vCP205 (gp120, gp41, gag, pol)**
**vCP300 (gp120, gp41, gag, pol, nef)**

## AVEG Western blot results

**Blots performed on 41/42 EIA screened positives.**
**3 (7%) were negative**
**13 (32%) were indeterminate**
**25 (61%) met ASTPHLD/CDC WB criteria for reactive test result**
**23/25 (92%) of these false positive blots were from canarypox prime/gp120 boost study arms**

## Indeterminate Western blot profiles from Env subunit vaccination (RV124)

- _0.797_
- _0.193_
- _0.119_
- _0.741_
- _0.097_
- _0.080_

**S/C**

## Reactive Western blot profiles from multi-antigen vaccinia vector vaccination (RV124)

_**1.335**_
_**4.065**_
_**3.314**_
_**3.422**_
_**0.990**_
_**0.302**_

**S/C**

## Challenge: Molecular diagnostic tests must be capable of uniformly detecting prevalent HIV-1 subtypes

## Global Threat–Evolving RiskGeographic Distribution of HIV-1 Subtypes – 1990’s

***Global Threat–******Evolving Risk******Geographic Distribution of HIV-1 Subtypes – 1990’s***

**B****,A,D,E**

**B,****E****,****F,C**

**B****,A,C,D,E,F,G,H**

**A,C,D,****E,F,G,H**

**B**

**E****,B**

**C****,B,E**

## Evaluation of HIV-1 subtypeon viral load assays

## NAT for the blood supply  clinical use

**Chiron/GenProbe ProcleixTM HIV-1/HCV assay FDA approved on 28 Feb 2002.**
**FDA approval for blood banks will allow “off-label” clinical use of NAT for confirmatory testing.**

## Blood banks using minipooling--can clinical labs?

**Blood banks pool 8 to 16 samples prior to submitting to Procleix.**
**Procleix has a 95% sensitivity at 50 RNA copies/ml and 100% sensitivity at 100 copies/ml.**
**Isn’t this sensitive enough?**

## Slide 21

## Blood banks using minipooling--can clinical labs?

**Minipooling can miss samples with VL of 1-2 logs by dilution.**
**Patients in early second window period can have low RNA and no HIV-specific antibodies.**
**US Army blood banks do not minipool--nor will my clinical laboratory.**

## The Impact of HIV Rapid Tests on the Laboratory Diagnosis of HIV

## Outline

**Rationale for rapid HIV diagnostics**
**Retrospective evaluation of rapid serum tests**
**Algorithm development & “corporate will”**

## Rationale for rapid HIV diagnostics

## National importance of rapid diagnostics

**Impact on high prevalent/low return rate settings:**
** ******** ****true negative, ******** true positive**
** ******** ****false positive?**
**Occupational post-exposure prophylaxis (PEP) decisions.**
**Perinatal antiretroviral drug Rx decisions.**

***MMWR 47****:****211-215 (1998)***

**Notes:**
Col John Hess the director of Blood Research Det, former Letterman Commander.

##  Military importance of rapid diagnostics

**All issues for civilian community**
**TriCare**
**Humanitarian assistance**
**Blood supply emergency screening.**
**Somalia, Bosnia, Kenya/Tanzania embassy bombings, *****USS Cole***
**Combat casualties testing.**

**Notes:**
Col John Hess the director of Blood Research Det, former Letterman Commander.

##  Civil-military importance of rapid diagnostics

**Local blood supply demand high (trauma)**
**Transportation interrupted (blood, test kits, ARVs)**
**Increased occupational exposure (rescue & recovery)**
**Smallpox attack response**
**Live attenuated vaccine...**
**...****highly dangerous to HIV+ and...**
**...****.HIV+ vaccine-induced smallpox cases enhance epidemic**

**Notes:**
Col John Hess the director of Blood Research Det, former Letterman Commander.

##  Civil-military importance of rapid diagnostics

**Need to pre-position rapid HIV tests devices and ARVs for civil-military emergencies?**
**Need FDA approved devices**
**Need recognized testing algorithm (APHL, WR_x0008__x0008_AIR, CDC, etc.)**
**Need training and awareness and engagement of state, local and federal public health laboratories prior to implementation.**

**Notes:**
Col John Hess the director of Blood Research Det, former Letterman Commander.

##  WRAIR/CDC collaboration on HIVrapid diagnostics: approach

**CDC: Prospective testing in areas of high HIV prevalence (intended use).**
**WRAIR: Retrospective testing of pedigreed serum archive.**
**FDA: WRAIR retrospective testing as substitute for low risk HIV population testing (e.g., blood banks)?**

**Notes:**
Col John Hess the director of Blood Research Det, former Letterman Commander.

## Retrospective evaluation of rapid serum tests

## Retrospective testing at WRAIR

**Serum panels are archived by EIA reactivity**
**All new panels are re-tested by EIA/WB**
**WRAIR is blinded to clinical data**
**Test devices were generally tested on unique panels**
**Retrospective testing is not “intended use”**

## Results

## Performance Modifiers

**Determine testing in Rakai, Uganda.**
**Use of single gp41 ID domain peptide for OraQuick.**

## Rakai, Uganda (Determine)

**Total specimens tested = 321**
**Tests censored = 120**
**EIA+/no WB f/u = 118 (data censored)**
**EIA-/QNS for Determine =2 (data censored)**
**Tests evaluated = 201**

**True pos = 21**
**False neg = 0**
**False pos = 17**
**True neg = 163**
**Sensitivity= 100%**
**Specificity = 90.6%**
**PPV+ = 63.4% (14% PP)**
**PPV-  = 100%**

## Algorithm development &“corporate will”

## Algorithm development

**Several rapid tests look technically promising**
**Corporate sponsors are moving toward FDA approval**
**WRAIR moving to algorithm testing on pedigreed serum panels**
**Retrospective testing is not “intended use”**

## “Strawman”

**Posit: Multiple rapid tests will yield equivalent performance compared with EIA/WB algorithms.**
**Sensitive screening & specific confirmatory test(s).**
**Algorithms will differ based on HIV prevalence, performance modifiers, and cost-benefit analysis.**

## Challenge to Industry

**Rapid HIV testing technology is robust.**
**Cost barriers to FDA approval reduce corporate will to pursue U.S. licensure of HIV rapid tests.**
**Non-FDA approved HIV rapid tests will have no market value in the U.S. or where federal dollars support overseas health care delivery.**

## Serial algorithm panel

**N = 400 pedigreed sera (23 R, 377 NR)**
**Two different rapid tests screen**
**Concordant NR = NR, final**
**Concordant R & discordant pair third rapid test.**
**100% accurate**
**Moving to N = 3,000**

## Summary

**HIV vaccines will confound the screening EIA and Western blot.**
**Nucleic acid testing can dissect infection from vaccine response with careful interpretation.**
**HIV rapid tests are a public health priority.**
**HIV rapid tests are needed for civil defense.**
***HIV rapid tests implementation must be coordinated at ALL levels of government.***