Project 8

HIV-1 spread in complex cell systems

Fackler, Oliver
Dept. of Infectious Diseases – Virology

Summary Project description 2nd funding period

The goal of this project is to develop new ex vivo and in vivo experimental models and study aspects of HIV
spread and pathogenesis that are not accessible to experimental manipulation in classical cell culture models.
During the first funding period we established (i) ex vivo CD4 T lymphocyte cultures in 3D collagen that allow
long-term quantitative assessment of parameters governing HIV spread and (ii) an immunocompetent adoptive
transfer mouse model for investigations of HIV evasion strategies from humoral immune responses of the host.
To assess the relationship between cell motility and virus spread in the 3D collagen system, a workflow for
particle tracking and image processing was developed together with the Rohr and Hamprecht groups.
Quantitative kinetic analyses revealed that the extracellular environment restricts HIV spread by cell-free
infection, promotes survival of infected cells and shapes modes and efficacy of HIV spread towards motilitybased,
cell-associated virus transfer. Through iterative cycles of experimentation and mathematical modeling,
these data allowed the establishment of two mathematical models describing the dynamics of virus replication
and cell motility/virus transfer together with the Schwarz and Graw laboratories. Work in the immunocompetent
mouse model established that the HIV-1 protein Nef potently suppresses the helper function of CD4 T cells
and thereby impairs production of antigen-specific antibodies. Building on the generation of these experimental
systems and the key findings made, we will pursue two specific aims in the next funding period. Specific aim
1 will seek to determine the molecular mechanisms by which the 3D environment shapes cell-associated HIV
transmission. By including antigen-presenting cells in the 3D culture system, we will study the relationship
between T cell activation and virus spread in 3D, including ultrastructural analyses of cell-cell contacts
mediating virus spread and cell activation in collaboration with Kräusslich and Funaya/Schwab. Specific aim 2
will address which steps of humoral immunity are affected by the viral Nef protein and dissect the underlying
molecular mechanisms. Applying advanced microscopy and mathematical modeling to these recently
established ex vivo and in vivo model systems will provide new insights into physiological determinants of HIV
pathogenesis.