Abstract
”An HIV-1 vaccine may be the first vaccine that is studied, moved forward, and ultimately licensed based on a cellular response.”
Automation of the quantitative assays used to assess the human cellular immunological responses to vaccines and other immunotherapeutic treatments would facilitate their use in clinical trials. This special issue of JALA presents five manuscripts on the automation of cellular immunology assays and sample handling. Cellular immunology has changed dramatically over the last decade, moving from analysis that is qualitative and very cumbersome to more quantitative assays that are easily transferable to automation. Two arms of the adaptive immune response play a role in fighting and clearing infections: the humoral and cellular arms. The cellular immune response can be further subdivided into a CD4 or CD8 lymphocyte response. Recently, our understanding of the cellular immune response has increased considerably. And, as already noted, our ability to measure the cellular immune response has likewise changed. Many of these changes are a result of the dire need for an HIV-1 vaccine. Vaccines are the most cost-effective means of controlling infection. Indeed, through an extensive vaccination program, smallpox has been eliminated, and polio will likely be eradicated within the next decade. Many of the current vaccines are live attenuated, and while they most likely induce a protective cellular immune response, they have been studied and licensed based on antibody responses. An HIV-1 vaccine may be the first vaccine that is studied, moved forward, and ultimately licensed based on a cellular response.
Historically, it was believed we would have a vaccine for HIV-1 shortly after the virus was isolated. However, it soon became apparent that this would not be the case. Based on a great deal of circumstantial evidence and studies performed in primates, it seemed clear that the cellular immune response plays an important role in controlling HIV-1 viral replication. With this knowledge, researchers and pharmaceutical companies began development of vaccines that would induce HIV-1-specific cellular immune responses. The assay used to assess these first vaccines was the qualitative cytotoxic chromium release assay. This assay was burdensome, radioactivity was needed, and a fair amount of in vitro manipulation of samples was necessary. We needed assays that were easier, more reliable, and translated from lab to lab. Scientists rose to the challenge to develop techniques that were reliably quantitative and repeatable.
Two of the most significant methods to be developed recently include measurement of IFN-gamma by either flow cytometry or ELISPOT analysis. IFN-gamma is produced by both CD8 and CD4 lymphocytes and is considered an accurate surrogate marker of the cellular immune response. Two manuscripts presented here provide data and a review of these techniques and their potential for automation: “Automation of Cytokine Flow Cytometry Assays” and “Automation of the Elispot Technique: Past, Present and Future.” In addition, a third manuscript by Cox et al. describes sample handling. In the manuscript “Automating Procedures for Processing, Cryopreservation, Storage and Manipulation of Human Peripheral Blood Mononuclear Cells,” Dr. Cox describes sample handling and cryopreservation. Blood for most immunology studies are drawn at several time points over the course of a clinical study. To minimize interassay variation, cryopreserved samples should be tested side by side in a single assay.
Unlike the sera used for antibody analysis, sample processing for cellular assays is much more sensitive. Handling cells is more labor intensive, and Browning presents a manuscript describing automation of sample handling: “The Labor Shortage, Patient Safety and Length of Stay: New Era of Change Agents Prompts Process Improvements Through Lab Automation.” Browning describes automation in hospital laboratories: a tool that can be used to help the laboratory contribute to a hospital's economic viability. In rethinking the tenets of lab operations, a new archetype can emerge that serves economic imperatives without sacrificing our responsibilities for improved patient care.
Finally, a paper presented by Mattoussi et al. describes the use of quantum dots. Quantum dots allow cell labeling without disturbing cell growth, and quantum dots can label a number of cellular proteins simultaneously with distinctive emission colors with minimal nonspecific binding. Quantum dots certainly provide a potential future means of detecting certain immune-specific cells and hold a great deal of potential for automation.
As methods for analysis of the cellular immune response were being developed for HIV-1, almost simultaneously these assays were applied to vaccines and treatments for a number of diseases and conditions, including cancer treatments, autoimmunity, and allergies. So, while HIV-1 may have propelled forward the development of new methods of measuring the cellular immune responses, the applications are wide ranging.