Functional Impairment of Murine Dendritic Cell Subsets following Infection with Infective Larval Stage 3 of Brugia malayi

Abstract

Filarial parasites cause functional impairment of host dendritic cells (DCs). However, the effects of early infection on individual DC subsets are not known. In this study, we infected BALB/c mice with infective stage 3 larvae of the lymphatic filarial parasite Brugia malayi (Bm-L3) and studied the effect on fluorescence-activated cell sorter (FACS)-sorted DC subsets. While myeloid DCs (mDCs) accumulated by day 3 postinfection (p.i.), lymphoid DCs (LDCs) and CD8 ϩ plasmacytoid DCs (pDCs) peaked at day 7 p.i. in the spleens and mesenteric lymph nodes (mLNs) of infected mice. Increased tumor necrosis factor alpha (TNF-␣) but reduced interleukin 12 (IL-12) and Toll-like receptor 4 (TLR4), -6, and -9 and reciprocal secretion of IL-4 and IL-10 were also observed across all DC subsets. Interestingly, Bm-L3 increased the expression of CD80 and CD86 across all DC subsets but decreased that of major histocompatibility complex class II (MHC-II) on mDCs and pDCs, resulting in their impaired antigen uptake and presentation capacities, but maximally attenuated the T-cell proliferation capacity of only mDCs. Furthermore, Bm-L3 increased phosphorylated p38 (p-p38), but not p-ERK, in mDCs and LDCs but downregulated them in pDCs, along with differential modulation of protein tyrosine phosphatases SHP-1, TCPTP, PTEN, and PTP1B across all DC subsets. Taken together, we report hitherto undocumented effects of early Bm-L3 infection on purified host DC subsets that lead to their functional impairment and attenuated host T-cell response.KEYWORDS filariasis, myeloid dendritic cells, lymphoid dendritic cells, plasmacytoid dendritic cells, flow cytometry, MAP kinases, Toll-like receptors P arasites have evolved many diverse and novel strategies to evade the host immune response (1). These include dampening of the host's proinflammatory cytokine response, attenuating the functions of innate immune cells; generating regulatory T cells; and impairing the activation, maturation, and functions of host dendritic cells (DCs), leading to their functional impairment (2-9). Impairment of host Langerhans cells has also been reported during lymphatic filarial infections, which suggests that parasites not only interfere with the functions of Langerhans cells, but have also developed means to expertly evade antigen (Ag)-presenting cell (APC) detection in the host skin (1, 10). We recently documented the role of lung eosinophils and functional impairment of lung macrophages during filarial manifestation of tropical pulmonary eosinophilia (TPE) (11). This is important, as macrophages, along with DCs, not only are a heterogeneous group of APCs, but immature DCs circulate in the peripheral blood, where they capture, process, and present antigens (12). Also, encounter of DCs with the pathogen results in their maturation, characterized by increased expression of major histocom-

The TLR5 Agonist Flagellin Shapes Phenotypical and Functional Activation of Lung Mucosal Antigen Presenting Cells in Neonatal Mice

“…Notably, adult and neonatal CD11c pos cells demonstrated comparable cytokine production after stimulation with TLR5, RIG-I, and STING agonists, while there was no difference in the basal level of cytokine production. Based on these observations, we speculate that the low abundance or immature phenotype of migDCs and pDCs in the lung may contribute to the greater susceptibility to respiratory infection in early life (44).…”

In vivo neutralization of α4 and β7 integrins inhibits eosinophil trafficking and prevents lung injury during tropical pulmonary eosinophilia in mice

“…Even though the accumulation of inflammatory cells in the tissues contribute to a wide range of diseases, immune cell migration is also critically important for the delivery of protective host immune response. In this context, we recently described a mouse model of Tropical Pulmonary Eosinophilia that exhibited heavy accumulation of eosinophils in the lungs and showed how infective larvae‐3 of the filarial parasite Brugia malayi (Bm‐L3) differentially affects the recruitment pattern and causes functional impairment of various dendritic cell subsets . However, affect of inhibition of integrin molecules that regulate the migration of a particular cell involved in the pathogenesis of a disease without affecting the trafficking pattern of other leukocytes required for protection against foreign entities is poorly understood.…”

Infective Larvae of Brugia malayi Induce Polarization of Host Macrophages that Helps in Immune Evasion

“…CD11c positive cells were enriched from the spleens of uninfected and Bm-L3 infected mice at day 3 and day 7 post infection using CD11c magnetic beads as described earlier ( 6 ). Thereafter, CD11c positive cell fraction (containing mostly DCs and MΦs) was incubated with CD11b-PE-Cy7 and F4/80-Pacific Blue anti-mouse monoclonal antibodies for 20 min at 4°C and flow cytometric data were acquired on five-decade log-scale dot plots displaying forward scatter (FSC) area vs. side scatter area (SSC).…”

“…Splenic MΦs were identified using the gating strategy as described above. MΦs were sorted using a high-speed FACS Aria flow cytometer fitted with a 70 µm nozzle as described recently ( 6 – 8 ). Sorted MΦs were subjected to post-sort analysis to ascertain the purity of sorted cells and a small fraction was used to prepare cytospins.…”

“…In addition to this, asymptomatic individuals harbor another phenotype of MΦs known as the regulatory MΦs (Mregs), which are characterized by high amounts of IL-10 that lead to modified type 2 responses and contribute to enhanced parasite survival. We also recently reported functional impairment of host DC subsets and attenuated T-cell response during early Bm-L3 infection ( 6 ). However, mechanisms that regulate the polarization of host MΦs following Bm-L3 infection remain unanswered.…”