Scientific Resources

To advance T cell-based HIV vaccine development,it is necessary to evaluate the immune correlates of a protective CD8(+) T-cell response. We have developed an assay that assesses the capacity ex vivo of HIV-specific CD8(+) T cells to suppress HIV-1 infection of autologous CD4(+) T cells. This assay directly reflects the ultimate effector function of CD8(+) T cells,the elimination of infected cells,and accurately differentiates the effective CD8(+) T-cell response in spontaneous HIV controllers from ineffective responses in other patients. In this article,we describe all the steps from cell purification to assessment of viral replication by HIV-p24 ELISA and analysis,along with conditions for cell culturing,and how to choose the viral infectious dose that gives the most reliable results. We also depict the conditions of a rapid assay on the basis of flow cytometry analysis of intracellular HIV-Gag products. These procedures take 14-17 d when the p24 ELISA assay is used,or 6 d with the intracellular Gag assay. View Publication

During persistent murine cytomegalovirus (MCMV) infection,the T cell response is maintained at extremely high intensity for the life of the host. These cells closely resemble human CMV-specific cells,which compose a major component of the peripheral T cell compartment in most people. Despite a phenotype that suggests extensive antigen-driven differentiation,MCMV-specific T cells remain functional and respond vigorously to viral challenge. We hypothesized that a low rate of antigen-driven proliferation would account for the maintenance of this population. Instead,we found that most of these cells divided only sporadically in chronically infected hosts and had a short half-life in circulation. The overall population was supported,at least in part,by memory T cells primed early in infection,as well as by recruitment of naive T cells at late times. Thus,these data show that memory inflation is maintained by a continuous replacement of short-lived,functional cells during chronic MCMV infection. View Publication

Gag-specific CD4 proliferative responses correlate inversely with HIV-1 RNA levels in infected adults,and robust responses are characteristic of long-term nonprogressive infection. However,strong responses are seldom detected in adult subjects with progressive infection and are not generally reconstituted on highly active antiretroviral therapy (HAART). To date,the role of HIV-1-specific Th responses in children has not been thoroughly examined. We characterized Gag-specific CD4 responses among 35 perinatally infected subjects,including 2 children who spontaneously control viremia without antiretroviral therapy,21 children with viral loads (VL) of textless400 on HAART,and 12 viremic children. Gag-specific Th activity was assessed by lymphoproliferative assay,and responses were mapped using overlapping Gag peptides in an IFN-gamma ELISPOT. Robust proliferative responses were detected in the children exhibiting spontaneous control of viremia,and mapping of targeted Gag regions in one such subject identified multiple epitopes. Among children textgreateror=5 years old,14 of 17 subjects with VL of textless400 on HAART demonstrated a significant p24 proliferative response (median p24 stimulation index,20),in contrast with only 1 of 9 viremic children (median p24 stimulation index,2.0; p = 0.0008). However,no subject younger than 5 years of age possessed a significant response,even when viremia was fully suppressed. When compared with adults with VL of textless400 on HAART,Th responses among children with VL of textless400 were both more frequent (p = 0.009) and of greater magnitude (p = 0.002). These data suggest that children may have a greater intrinsic capacity to reconstitute HIV-1-specific immunity than adults,and may be excellent candidates for immune-based therapies. View Publication