Distinctive anti-influenza properties of recombinant collectin 43

Abstract

Collectins play important roles in innate defence against viral, fungal and bacterial pathogens. CL-43, a bovine serum collectin, which appears to have evolutionarily evolved from surfactant protein D (SP-D), shows unique structural and functional properties. In the present study, we describe the initial characterization of a recombinant CL-43 expressed in mammalian cells. Like natural CL-43, the recombinant is secreted as trimeric forms that show a preference for mannose and N-acetyl mannosamine. The natural and recombinant proteins have significantly higher haemagglutination-inhibiting activity against influenza A virus (IAV) than recombinant trimeric forms of SP-D. In contrast with the more highly multimerized forms of SP-D, namely conglutinin or mannose-binding lectin, CL-43 did not induce viral or bacterial aggregation and did not enhance IAV-induced neutrophil H(2)O(2) generation. Like SP-D, CL-43 also strongly enhanced neutrophil uptake of IAV. However, the mechanism of this enhanced internalization is different from that of SP-D in that it did not require viral aggregation. These studies establish that the trimeric structure of CL-43 is specified by its primary sequence and indicate that this naturally occurring trimeric collectin has unique antiviral activities. These findings could facilitate the development of recombinant collectins with novel antimicrobial properties.

Respiratory innate immune proteins differentially modulate the neutrophil respiratory burst response to influenza A virus

“…Consistent with previous findings (4, 45), this effect was dependent on the presence of dodecameric or multimeric forms of SP-D. In the (4,20). Similarly, large IAV particles have been shown to be more effective at stimulating respiratory burst responses of phagocytic cells than small particles (42).…”

Porcine Pulmonary Collectins Show Distinct Interactions with Influenza A Viruses: Role of theN-Linked Oligosaccharides in the Carbohydrate Recognition Domain

“…4 shows that the addition of pSP-D caused aggregation of IAV as assessed by a time-dependent decrease in light transmission through a suspension of the Phil strain. The Phil IAV-aggregation curve for pSP-Dcon was similar to that of RrSP-D and RhSP-D when equal amounts of collectins were used (800 ng/ml) (34). Removal of the N-glycosylation in the CRD significantly reduced the viral aggregation activity of pSP-D.…”

“…After exposure of the MDCK cells to the IAV or IAV/collectin mixture for 30 min at 37°C, the cells were washed three times in serum-free DMEM containing 1% (w/v) penicillin-streptomycin. The monolayers were then incubated for 7 h at 37°C, whereafter they were washed, fixed, and FITC-labeled for IAV nucleoprotein as described (34). Fluorescent foci, which appeared to be single-infected cells in general, were counted, and results were expressed as percentage of control foci present after infection with collectin-treated virus as compared with untreated virus.…”

The Plant Virus Tomato Spotted Wilt Tospovirus Activates the Immune System of Its Main Insect Vector, Frankliniella occidentalis

“…Table 1 shows that WFT genes activated after TSWV infection included homologues of genes with reported or putative immune functions. These genes can be divided into the following categories: (i) those encoding proteins putatively involved in recognition and phagocytosis of insect-invading microorganisms, such as lectins (13,20,24,45), Jnk kinase (33), and complement-like proteins (13,24); (ii) those encoding Toll-like surface receptors (23), responsible for the activation of signal transduction pathways that trigger the innate immune response, such as Toll-3, which has been reported to participate in double-stranded RNA recognition in mammalian cells (1), and MyD88, which is required in the immune response against fungi and bacteria (44); (iii) those encoding proteins that participate in the subsequent Toll signaling cascade, such as Relish, 18w, Ikk␣, Spatzle, and Cactus (23,26,38); (iv) those encoding antimicrobial peptides, such as defensins A and D, cecropin B, and lysozyme C, a family whose members have been reported in immune responses against viruses, bacteria, and fungi (21); (v) those encoding cytokines that have potential roles in activating humoral responses, such as activin (9,24,40); (vi) those encoding members of the immunoglobulin superfamily of proteins, such as hemolin (43); (vii) those encoding storage proteins, such as larval serum protein 1␤, a protein similar to arylphorins and arylphorin receptors, whose specific immune function is unknown (5), and (viii) those encoding proteases, whose general role in insects' innate response, as well as many other functions, has also been reported (9,21,24,51). Figure 1 shows DNA macroarray hybridization results in selected areas of nylon membranes with some of the selected genes (those encoding defensin D, hemolin, Ikk kinase, and complement-like TEP1).…”