In an effort to bring more consistency to comparisons of cell-mediated immunity in clinical trials of malaria vaccines, the PATH Malaria Vaccine Initiative (MVI) has teamed up with the International AIDS Vaccine Initiative (IAVI) and Imperial College London to establish a ‘reference’ laboratory for measuring immune responses.

Both IAVI and Imperial have a track record of developing validated human immunological assays, noted the US-based PATH (Program for Appropriate Technology in Health) MVI.

Under the collaborative agreement, IAVI and its laboratory partner at Imperial College London will focus on providing two types of assays for MVI and its collaborators as they move vaccine candidates into clinical trials.

These are the Interferon-gamma ELISpot assay and a multi-colour flow cytometry assay. The tests will be used to detect disease-fighting T-cells in the blood of volunteers following vaccination.

Lack of uniformity

In the past, noted MVI director Dr David Kaslow, malaria vaccine researchers have struggled to make direct comparisons between cellular immune responses elicited by different vaccines in humans, hampering their ability to prioritise vaccine candidates.

One problem has been the lack of uniform validated techniques and processes among the various laboratories used by MVI and its collaborators to evaluate T-cell immunity, MVI pointed out.

IAVI and its Human Immunology Laboratory at Imperial College London in the UK addressed similar challenges in the AIDS vaccine field by refining and validated specific assays to measure vaccine-induced, cell-mediated immunity.  

“Many of the methods and strategies employed in AIDS vaccine development could be of use in efforts to develop a malaria vaccine,” commented Margaret McGlynn, president and chief executive Officer of IAVI.  

Quantitative and qualitative

The assays to be developed by IAVI and Imperial for the PATH MVI will provide quantitative information, such as how many cells responded to the vaccine, as well as qualitative outcomes, such as the different cell types stimulated, explained Professor Gavin Screaton, head of the Department of Medicine at Imperial College London.  

According to Kaslow, the tests will help MVI to prioritise investments and will enable scientists to refine vaccine strategies by showing whether a particular formulation, delivery approach or vaccine adjuvant elicits a superior cell-mediated immune response.

At the same time, he stressed, malaria vaccine developers should continue performing their own tests to gauge immune responses.