From Talk to Action in Fighting AIDS in Developing 10 Countries

272). However, in contrast to previous published reports of a correlation between viral load and CTL magnitude when A2 restricted responses alone are studied, these more comprehensive studies failed to show any significant correlation. Other studies examined CTL epitope density in different regions of the virus, including p17 and Nef, and identified a clear correlation between predicted proteasomal cleavage sites and actual epitope boundaries (Yusim et al, Abstract 271). Such studies begin to address the issue of relative immunodominance of CTL responses, an issue of critical relevance to vaccine design. CD8+ cells have been shown to lyse infected cells but also to release soluble inhibitory factors that include beta chemokines that inhibit R5 viruses as well as other factor(s) that inhibit X4 viruses. The precise characterization of the elusive X4 inhibitory factor(s) remains to be determined. There was relatively little presented at the meeting relating to this response. Persons who are treated in the acute stage of infection appear to develop particularly robust CD8+ cell noncytotoxic activity, and the ability of this response to inhibit viral replication appears to be best when there is direct cell-to-cell contact (Chun et al, Abstract 504). However, full characterization of the factor remains elusive. In the past 2 years numerous publications have indicated a role for virus-specific CD4+ T helper cells in effective control of chronic HIV infection, and additional data at this meeting further support this notion, although not without persisting controversies. The relationship between CD4+ T helper cells and CTLs was further evidenced by a macaque immunization model, in which induction of CTLs was associated with the induction of strong CD4+ T helper cells directed against the virus (Belyakov, Abstract S5). Such relationships were also implied in studies of natural infection in humans (Imami et al, Abstract 158; Autran et al, Abstract 160). The delineation of this relationship between CD4+ T helper cell responses and CTL function should be important, since it will help to guide immunotherapeutic interventions for persons who are already infected. A number of studies addressed the important issue of what factors contribute to the lack of immune control in chronic infection. Insights into the lack of T helper cell responses to HIV in persons with chronic infection were provided by studies using proliferation assays, IFN-γ and interleukin 2 (IL-2) ELISPOT assays, and major Conference Highlights HIV Pathogenesis and Vaccine Development Volume 9 Issue 2 June 2001