In a large, multi-site, international trials organization such as the HIV Vaccine Trials Network, several steps of every trial have to be standardized to ensure that scientists can accurately interpret the results. If researchers want to meaningfully compare the immune responses induced by two different HIV vaccines the experimental procedures used to measure those responses have to be the same. The HVTN laboratory program, centered at VIDD and led by VIDD co-director Dr. Julie McElrath, performs assays for all HVTN clinical trials, generally looking for the participants’ immune responses to a candidate vaccine.
VIDD staff scientist Dr. Olivier Defawe is the co-manager of the Endpoints Laboratory at the Fred Hutchinson Cancer Research Center, a group that performs assays looking at immune responses to HVTN trial vaccines at the cellular level. Defawe and his group also work closely with the Research and Development lab, run by VIDD assistant member Dr. Nicole Frahm. Frahm’s lab works to develop new assays, and the Endpoints lab helps to qualify and validate these assays for standardized use in clinical trials.
“There’s quite a bit that happens behind the scenes here in the Lab Program Group,” Defawe said. “A lot happens between when the participant comes to the clinics and gives their blood and the final data point that people aren’t as aware of. There’s the processing of the sample, the shipment, repository, running the assay, running the statistical analysis, and then production of the reports.”
The Endpoints lab assays test whether a given vaccine is immunogenic, Defawe said, meaning whether it prompts its recipient’s immune cells to produce a response robust and specific enough to prevent HIV infection. Humans have a variety of immune cell types which can produce numerous types of immune signaling molecules. The characterization of how these cell types and molecules change in response to vaccination can help researchers understand the molecular basis behind successful or failed HIV vaccines.
In the last few years, many new types of assays have been developed, Defawe said. Before the Step trial, an HVTN trial of a candidate HIV vaccine by Merck that was halted in 2007, there were two cellular assays primarily performed in the lab. The ELISPOT assay as performed in the Endpoints lab looks for the production of one type of immune molecule, interferon gamma, by T cells as a marker of activation in response to vaccination. Intracellular cytokine staining, or ICS, looks at two to four immune markers at once and can differentiate among different types of T cells, separating CD4+ T cells, or T helper cells, from CD8+ T cells, or cytotoxic T cells.
After the Step trial was halted and researchers became more interested in investigating why that vaccine didn’t protect against HIV infection, labs started developing more detailed assays to study cellular immune responses. “There has been a big evolution in Endpoints assays,” Defawe said.
In addition to ICS and ELISPOT, the Endpoints lab is now looking at many other immune markers, and is adding assays to look at other immune cell types, such as B cells and natural killer cells. The lab has just started performing Luminex-based assays, which, unlike ELISPOT and ICS, can look at many different markers at once. “This kind of assay is useful when you don’t know exactly what you’re looking for,” Defawe said. “You can look at a lot of different markers, markers that indicate inflammation, markers for B cells, T cell activation, etc.”
Defawe started working for the HVTN nearly four years ago as a data manager for the immunogenicity data, standardizing the workflow for data between sample receipt at the lab repository and when the data is released from the Endpoints laboratory. After a year, he transitioned to lab manager of the Endpoints lab. Originally from Belgium, Defawe studied cardiovascular diseases through his doctoral work and postdoctoral fellowship, making a major career change to infectious diseases when he joined the Hutchinson Center because he wanted to be closer to clinical trials and applications that had the potential to help people.
New developments in the HIV vaccine field over the past few years have spurred researchers to set up more assays of the type performed in the Endpoints lab, Defawe said. The recent success of the Thai trial, a study of an HIV vaccine that provided partial protection against infection, has put more pressure on the field to understand humoral and cellular responses to candidate vaccines.
“There is a real need in the field for newer assays to try to better understand the immune response to a vaccine or product,” Defawe said. “So we in the Endpoints and R+D labs are working almost full time on developing new assays.”