The ability to rapidly identify immune cell subsets such as CD4 cells, which became possible around the same time as the onset of the HIV/AIDS pandemic, was one of the greatest advances in clinical and diagnostic immunology. The evolution of this global pandemic and the subsequent development of treatment strategies to prolong the life of infected individuals mean that it is now more crucial than ever that we develop affordable, reliable and accurate methods for the enumeration of CD4 cells. Here, we provide an overview of the historical developments in CD4 enumeration technologies that are related to HIV infection, and summarize the current technological challenges that must be overcome to meet the needs of those living with HIV infection.Recent figures from the World Health Organization (WHO) indicate that almost 33.2 million people are living with HIV infection worldwide, and over two-thirds of infected individuals are present in developing countries with limited resources (FIG. 1). In the region that has been hardest hit by AIDS -sub-Saharan Africa -the prevalence rate of HIV infection is 39%, yet only 17% of the HIV-infected individuals in this region had access to life-saving antiretroviral (ARV) therapy in 2007. Globally, more than 50% of those infected with HIV are women. Furthermore, recent reports from the WHO state that 1,800 babies are born with HIV every day because their mothers cannot access the necessary drugs or healthcare treatment. It is predicted that between 2008 and 2010 there will be 45 million new infections in resourceconstrained and middle-income countries if no additional preventative methods are introduced.It is now well recognized that, in the majority of cases, the development of AIDS parallels the decline in CD4 + T cells, which play a vital role in the regulation of the immune response. HIV specifically targets and binds to the CD4 antigen and chemokine receptor 5 (CCR5) or CXC chemokine receptor 4 (CXCR4) on CD4 + T cells to replicate, ultimately causing the destruction and deterioration of the immune system. The monitoring of CD4 + T cells during the course of HIV infection is therefore a crucial component in the monitoring of disease progression and the response to ARV therapy.Over the past 25 years there have been major technological advances in the ways that CD4 + T cells are enumerated, with flow cytometry now generally regarded as the predicate technique. During this period, flow cytometry has progressed from large, expensive and complex fluorescence-activated cell sorting (FACS) machines that require highly specialized operating personnel, to smaller, more affordable bench-top instruments that can be used by individuals

No abstract

No abstract