REFERENCES

1. Performance of commercially available HIV Rapid and HIV ELISA test kits on post HIV vaccination samples to evaluate Vaccine Induced Sero-Reactivity Paramesh Chetty 1, Gwynn Stevens1,Bashir Farah2, Irene Mwangi2, Stella Wangui2, Claudia Schmidt1, Dagna Laufer1, Omu Anzala2 1 International AIDS Vaccine Initiative (IAVI), New York, USA and 2 Kenyan AIDS Vaccine Initiative (KAVI), Nairobi Kenya BACKGROUND Phase 1 preventative HIV vaccine clinical trials enrol low risk HIV negative volunteers. Most HIV vaccine immunogenes encode proteins mainly from the env, gag, pol, and nef regions and are designed to induce the production of protective antibodies. The elicited vaccine induced antibodies (VISP) in the absence of HIV infection can confound the interpretation of standard HIV test kits’ results. Delineation of these seropositive results among vaccine recipients has resulted in the use of more complicated HIV testing algorithms and laboratory techniques, such as HIV-1 RNA detection. Determining the best suited HIV testing algorithm for a particular product/trial is crucial in distinguishing VISP from true HIV infection. METHODS HIV-uninfected study volunteers were randomised to receive either the Ad26-ENVA or Ad35-ENV product, or both products or placebo in a prime-boost regimen as in Table 1.  Samples stored from 32 vaccine and 8 placebo recipients at 2 months and 9 months post last vaccination were tested on 4 different HIV test kits at the KAVI research centre in Nairobi, Kenya. Details of the test kits can be found in Table 3. Samples from 2 months and 9 months post last vaccination visits were tested using the HIV Rapid test kits (Alere Determine HIV-1/2 and Trinity Uni-Gold HIV) and BioMerieuxVironostika HIV Ag/Ab Elisa kits. Samples only from 9 months post last vaccination were tested on the HIV ELISA Mini-Vidas HIV Duo Ultra (HIV5) Ag/Ab test kit and. Data for 2 months post last vaccination were already available for the Vironostika HIV Ag/Ab test kit as part of the on study HIV testing algorithm. Kanya AIDS Vaccine Initiative (KAVI) KAVI Laboratory Team Clinical Team (Left to right) I. Mwangi. B. Farah, S.Ogola, R. Chirchir And R. Langat • METHODS • Table 1: KAVI Section of Study Design Figure 1: Vaccine Inserts • Ad35-ENV: Recombinant adenovirus serotype 35 • vector vaccine is a recombinant replication- • incompetent product that encodes the HIV-1 subtype • Agp140 envgene. (Figure 1) • Ad26.ENV.01 (rAd26): Recombinant adenovirus • serotype 26 vector vaccine is a recombinant • replication-deficient product composed of an • adenovirus serotype 26 vector that encodes the HIV-1 • Clade A Env glycoprotein 140 (strain 92rw020)(Figure 1). • Table 3: Details of Kit Inserts • *Only available information from package insert • for Alere Determine HIV-1/2 is the sensitivity • Profile as listed below: • HIV-1 Positive 100% • HIV-2 Positive 100% • HIV-1 Subtype A-G 100% • HIV-1 Group O 100% • RESULTS • After un-blinding 31/32 of the vaccine recipients were shown to express VISR. The 31 volunteers that received the investigational product and expressed VISR had HIV-1 RNA PCR confirmatory tests conducted and all test results were undetectable for HIV-1 wild type infection. • Table 4. Comparison of test kit Results • Vaccine recipients showed higher percentages of reactive results using the 4th generation (BioMerieuxVironostika Ag/Ab and Mini-Vidas Ultra Duo Ag/Ab, 96.9%) versus 3rd generation (Alere Determine HIV 1/2, 37.5% & 9.4%; Trinity Uni-Gold HIV, 50% & 3.1%) HIV test kits (Table 4). • No placebo recipients showed any VISR. • VISR declined over time, possibly due to waning of the vaccine induced antibody titre. • . CONCLUSION • Selection of appropriate HIV test kits when developing a suitable HIV testing algorithm(s) to support a preventative HIV vaccine trial can be challenging. 3rd generation HIV Rapid test kits were much less sensitive, detecting VISR less often when compared to 4th Generation ELISA kits. Post vaccination samples from previous HIV vaccine trials with similar products are useful when designing HIV testing algorithms for subsequent trials. • The occurrence of VISR is dependent on the HIV gene inserts in both the test kit and the investigational product. • The above analysis indicated that HIV vaccines that carry the ENV gene tend to trigger VISR, particularly when using a 4th generation HIV ELISA test kit. • Optimally an HIV testing algorithm would include HIV test kits that only detect HIV-1 wild type infection and not VISR in a cost effective, timely manner to mitigate anxiety and potential social harm to the volunteer. In Kenya / Africa setting community based HIV testing is done using the HIV Rapid tests. • Collecting post-trial follow-up data on VISR is important to better characterize VISR persistence and to avoid potential VISR results through community-based HIV testing of volunteers. Table 2: Vaccination visits and HIV testing time points Figure 2: On study HIV testing Algorithm REFERENCES 1 Etienne Karita et al., Safety in a Phase 1 randomized, double-blind, placebo-controlled trial evaluating two adenovirus HIV vaccines in three different geographic regions (IAVI-B003/IPCAVD-004/HVTN091 trial) 2 Jill Gilmour et al., Immunogenicity of homologous and heterologous regimens of Ad26-EnvA.01 and Ad35-EnvA HIV vaccines in HIV-uninfected volunteers in the US and Africa ACKNOWLEDGEMENTS Thanks to all the dedicated trial participants, the staff at the clinical sites and immunology support laboratories. Thanks to EMMES and SCHARP for data analysis and clinical trial database support. The B003/IPCAVD004/HVTN091 clinical trial was conducted at theBrigham and Women's Hospital, Harvard Medical School, USA; Projet San Francisco, Rwanda; Zambia HIV Research Group, Zambia; Kenya AIDS Vaccine Initiative, Kenya; The Desmond Tutu HIV Centre Institute of Infectious Disease and Molecular Medicine Faculty of Health Sciences, South Africa; Perinatal HIV Research Unit, South Africa; The Aurum Institute for Health Research, South Africa; in collaboration with the Beth Israel Deaconess Medical Center, Harvard Medical School, USA;the Fred Hutchinson Cancer Research Center, USA; the HIV Vaccine Trial Network, USA; The Ragon Institute, USA; the National Institute of Allergy and Infectious Diseases, USA and Crucell Holland BV, Netherland.