Abstract:
Toll-Like receptors (TLR) are pattern recognition receptors; a component of the innate
immune system that are involved in the recognition of pathogen-associated molecular
patterns (PAMPs). Recent studies have show that TLRs are able to recognize microbial
components for pathogens causing sexual transmitted infections that increase the risk for
acquiring HIV-1 virus. TLR7/8 was recently shown to recognize guanine and uridine
rich ssRNA with sequence homology to ssRNA from the HIV-1 virus. This study tested
the cytokine responses to TLR agonists by cervical mononuclear cells (CMCs) from the
human female genital tract. The hypothesis for the study was that HIV-R women (HIV
negative >3years) have different cytokine responses in CMCs after TLR stimulation
compared to HIV susceptible (HIV negative <3 years) and HIV positive sex workers.
The TLR agonists used were Escherichia coli Lipopolysaccharide (TLR4 ligand),
ssRNA40/LyoVec (TLR 7/8 ligand) and Imiquimod (TLR7 ligand). The amount of
cytokine produced was measured from culture supernatants using cytokine bead arrays
and ELISA techniques. The main responses detected were TNF-, IL-10, IFN- and
IFN-α, with minor levels of IL-6, IL-5, IL-4, and IL- 2 responses. HIV-R women had
significantly lower TNF- responses to E. coli LPS compared to HIV susceptible
women p=0.0309, significantly lower TNF- to ssRNA40/LyoVec compared to HIV-P
women p=0.0043. A trend for lower TNF- responses in the CMCs from HIV-P women
compared to HIV-S women p=0.0752 was observed. Imiquimod stimulated significantly
higher TNF- responses in HIV-S compared to HIV-P women p=0.0226. HIV-R women
had significantly lower IL-10 responses to E. coli LPS compared to both HIV-P
xvi
p=0.0137 and HIV-S p=0.0196. HIV-R also had significantly lower IL-10 responses to
ssRNA40/LyoVec compared to HIV-P p=0.0276 and lower IL-10 responses to
Imiquimod compared to HIV-S p=0.0316. The IFN-γ response in HIV-P women was
significantly higher than HIV-S following stimulation with ssRNA p=0.0179 and
Imiquimod p=0.0032, and higher than HIV-R after Imiquimod stimulation p=0.0446.
Overall, CMCs from the genital tract of HIV-1 resistant women had lower
proinflammatory responses to TLR ligands compared to HIV susceptible women. The
two TLR7 signaling ligands ssRNA and Imiquimod stimulated different cytokine
profiles, which indicate the possibility of use of different TLR signaling agents in
immune-modulation to alter the cytokine profiles in the genital tract. These results help
improve the understanding of the innate cytokine responses by CMCs in the genital
mucosa, and may thus point to innate mechanisms that influence susceptibility to HIV-1
infection.
