Oral Presentation Australasian Cytometry Society 2016 Annual Conference

DIVERGENT EXPRESSION OF CXCR5 AND CCR5 ON CD4+ T CELLS AND THE PARADOXICAL ACCUMULATION OF T FOLLICULAR HELPER (TFH) CELLS DURING HIV INFECTION (24079)

John Zaunders 1 , Yin Xu 2 , Michelle Bailey 2 , Kazuo Suzuki 1 , David A Cooper 2 , Stephen J Kent 3 , Paul Gorry 4 , Richard Harvey 1 , Stuart Turville 2 , Kersten Koelsch 2 , Anthony D Kelleher 2
  1. Centre for Applied Medical Research, St Vincent's Hospital, Darlinghurst, NSW, Australia
  2. Kirby Institute, UNSW , Sydney
  3. Microbiology and Immunology Dept, University of Melbourne, Melbourne, VIC, Australia
  4. School of Health and Biomedical Sciences, College of Science, Engineering and Health, RMIT University,, Bundoora, VIC, Australia

T follicular helper cells (Tfh) are expanded in lymphoid tissue during HIV-1 infection, but are also highly infected with HIV DNA, despite reportedly being CCR5-. We studied how Tfh cells are infected, but still increase relative to other CD4+ T-cells.

Tfh were studied from fine needle biopsies of lymph nodes (LN FNB) and by splenectomy and tonsillectomy from HIV-uninfected controls and HIV+ subjects. Tfh and germinal centre B cells were measured by multiparameter flow cytometry, and HIV DNA by qPCR. From SIV-infected macaque LN cells, and from human tonsil cells, CCR5+ and CCR5- subsets of PD-1intermediate pre-Tfh and PD-1high CXCR5+ Tfh were purified by cell sorting.

In LN FNB samples, Tfh were elevated 4.3-fold, and GC B cells 110-fold in untreated HIV+ subjects, compared to controls. Proviral HIV env DNA sequences from splenic Tfh were CCR5-using. In the macaque model, SIV-infected CCR5+ PD-1intermediate pre-Tfh could differentiate in vitro into SIV-infected PD-1high Tfh, but many Tfh also came from CCR5-negative pre-Tfh. Human tonsillar Tfh are largely CCR5-, and could not be infected in vitro with CCR5-using HIV, but surprisingly, median 39% of PD-1high Tfh expressed CCR5 at a low level, detected using optimized staining, and could be infected.

Altogether, the expansion of Tfh (leading to the huge increase in GC B cells) comes from both CCR5- and CCR5+ pre-Tfh. The latter can be infected, in addition to the small subset of CCR5low Tfh, leading to the significant HIV-1 DNA reservoir in Tfh in germinal centres, which is resistant to antiretroviral therapy.