MyD88 and TLR2, but not TLR4, are required for host defense against Cryptococcus neoformans

Abstract

We investigated here the potential role of Toll-like receptors (TLR) and the adaptor protein MyD88 in innate immunity responses to Cryptococcus neoformans, a pathogenic encapsulated yeast. Peritoneal macrophages from MyD88 -/-or TLR2 -/-mice released significantly less TNF-a, compared with wild-type controls, after in vitro stimulation with whole yeasts. In contrast, no differences in TNF-a release were noted between macrophages from C3H/HeJ mice, which have a loss of function mutation in TLR4, relative to C3H/HeN controls. When MyD88-or TLR2-deficient mice were infected with low doses of the H99 serotype A strain, all of the control animals, but none of MyD88 -/-and only 38% of the TLR2 -/-animals survived, in association with higher fungal burden in the mutant mice. Both MyD88 -/-and TLR2 -/-animals showed decreased TNF-a, IL12p40 and/or IFN-c expression in various organs during infection. No difference in susceptibility to experimental cryptococcosis was found between C3H/HeJ mice and C3H/HeN controls. In conclusion, our data indicate that TLR2 and MyD88, but not TLR4, critically contribute to anti-cryptococcal defenses through the induction of increased TNF-a, IL-12 and IFN-c expression.

Deoxynucleic Acids from Cryptococcus neoformans Activate Myeloid Dendritic Cells via a TLR9-Dependent Pathway

“…In contrast, TLR4 was reported to sense glucuronoxylomannan, a major component of the polysaccharide capsule of Cn, in Chinese hamster ovary cells (15). Thus, the role of TLR2 and TLR4 in recognition of Cn remains to be fully understood, and some other TLR may be involved when considered along with the previous findings that the host-protective response was impaired in MyD88 Ϫ/Ϫ mice (12,13). The unmethylated CpG motif-containing DNA from prokaryotic microorganisms such as bacteria and viruses is known to trigger host immune responses by interacting with TLR9 (16 -18), which is distributed in the endosomal compartments (19,20).…”

“…Using mice genetically lacking MyD88 or TLR2 (MyD88 Ϫ/Ϫ or TLR2 Ϫ/Ϫ mice), it was revealed that MyD88 plays a critical role while TLR2 plays a relatively limited role in the response to Cn (12). In another study (13), TLR2…”

Type I IFN Signaling Is Crucial for Host Resistance against Different Species of Pathogenic Bacteria

“…For the quantification of IFN-␣4 and IFN-␤ mRNA, real-time quantitative RT-PCR assays were conducted, in duplicate, with an Applied Biosystems 7500 (Applied Biosystems), as described (37). PCR conditions were as follows: 50°C, 30 min; 95°C, 10 min; (95°C, 15 s; 60°C, 1 min) ϫ 40 cycles.…”

“…Real-time PCR data were normalized in each individual sample by the level of ␤-actin expression. Gene expression was measured by the comparative cycle threshold method (⌬⌬C T ) and was reported as the n-fold difference relative to the normalized expression of unstimulated samples (37). Primers and TaqMan MGB probes for ␤-actin, IFN-␣4, and IFN-␤ have been previously described (38,39) and were purchased from Applied Biosystems.…”

O papel de receptores de imunidade inata βGR, MR, TLR2 e TLR4 no reconhecimento da Candida albicans por monócitos humanos estimulados com polissacarídeos extraídos do cogumelo Agaricus brasiliensis

“…Cryptococcus neoformans (Yauch et al, 2004;Biondo et al, 2005). Contudo, outros trabalhos sugerem que o TLR2 e TLR4 não contribuem com a resposta do hospedeiro contra esse patógeno (Nakamura et al, 2006).…”