A Fellows South African Experience

Jessica Radzio is an Associate Service Fellow with the HIV Drug Resistance and Chemoprophylaxis Activity in the Laboratory Branch of the Division of HIV/AIDS Prevention (DHAP) at the CDC headquarters in Atlanta. Her current work is centered on evaluating the efficacy of antiretroviral pre-exposure prophylaxis (PrEP) in preventing HIV transmission using macaque models. She recently came to CDC South Africa as an International Experience and Technical Assistance (IETA) Fellow with the South African Laboratory Branch. To follow is a first-hand account of her experience in South Africa.

After a few months of working out details and ironing out logistics, I’m thrilled to be working here in South Africa during my IETA assignment. This has been my first experience working outside of the US and I’m quite grateful the CDC has provided me this opportunity. My situation is unique in that I’ve had the chance to be involved with the Lab Branch at the CDC office in Pretoria as well as with the basic science being conducted at the National Institute for Communicable Diseases (NICD, part of the NHLS) here in Johannesburg. The work being conducted at the AIDS unit of NICD focuses on cutting edge immunology and drug resistance. Research here spans vulnerabilities in the immune escape of HIV during the course of infection to evaluating and monitoring resistance patterns locally and around the country using the newest technologies including ultra-deep sequencing. I am fortunate enough to have been invited here by the Lab Branch and joined the resistance group led by Dr. Gillian Hunt.

Integrase Inhibitors

During my stint here, I have been tasked with helping the resistance group develop and improve their current genotypic and phenotypic assays to evaluate the susceptibility of HIV-1 to antiretroviral integrase inhibitors. Integrase inhibitors are the latest class of compounds to be added to the treatment arsenal. The integrase enzyme is an ideal drug target because it is required during the life cycle of HIV-1 for the integration of provirus into the host DNA and no human homolog for this enzyme exists. Once the provirus is integrated into the host cell’s genome, it will be copied along with the cell’s own DNA causing a life-long infection of that cell. Because inhibitors of integrase are completely independent in their activity compared to all other antiretroviral drug classes (reverse transcriptase, protease, maturation and entry inhibitors), multidrug-resistant virus is still susceptible to them. To date, three integrase inhibitors have been licensed and approved by the FDA: raltegravir, dolutegravir and elvitegravir. While these compounds have proven to be superior to other regimens in first-line therapy1, cost has kept them from being widely used here in South Africa. However, a recent agreement between ViiV Healthcare and Medicines Patent Pool allows the early development of generic dolutegravir to be made available, presumably cutting down the typical 5-10 years the world must wait for quality generic compounds after US approval2.

Developing and Improving Assays

The drug resistance lab in the AIDS Unit at NICD routinely performsgenotypic and phenotypic assays to evaluate resistance mutations in both the protease and reverse transcriptase genes of HIV-1. Genotyping begins with the amplification of the gene of interest, followed by a sequencing reaction. With the help of Dr. Hunt’s expert team, I was able to adapt the amplification and sequencing protocols specific for the integrase gene developed by Dr. Chunfu Yang’s group at headquarters to meet their needs. To complement this assay, I have had the opportunity to work with Dr. Adrian Basson, a researcher who has developed an in-house pseudovirus phenotypic assay to evaluate the replication capacity of HIV-1 in the presence of reverse transcriptase or protease inhibitors. The current system cannot be used to evaluate integrase inhibitors, because the original clone was created from sequences of both subtypes B and C. While most of the sequence is subtype C, the integrase gene contained a majority of subtype B sequence. To adapt this viral vector system to evaluate replication capacity in the presence of integrase inhibitors for clones from this region (where subtype C is most prominent), I amplified the subtype C integrase gene from a wild-type construct and used it to replace the subtype B integrase in the original viral expression vector. Additionally, I designed primers for a method known as site-directed mutagenesis to introduce drug resistance mutations into the integrase gene for Dr. Basson to use in his studies evaluating the effects of integration inhibitors on HIV-1 subtype C. Having these two assays available in the local NICD lab facility will allow the group to screen for integrase mutations and phenotypic resistance for future studies.1. Messiaen, P., et al. Clinical use of HIV integrase inhibitors: a systematic review and meta-analysis. PloS one 8, e52562 (2013).

2. Burrone, E. & Perry, G. Affordability of new HIV treatments. Lancet 384, 853 (2014).