To date, few cytokines have been described from insects or insect cells. Examples

include a growth-blocking peptide present in hemolymph of larvae of the insect armyworm Pseudaletia separata parasitized by the wasp Apanteles kariyai. The growth-blocking peptide has repressive activity against juvenile hormone esterase [17]. Another growth-blocking peptide (GBP) from Lepidopteran insects regulates larval growth, cell proliferation, and immune cell (plasmatocyte) stimulation [18]. These cytokines belong to what is called the ENF multifunctional peptide family that is characterized by the unique ENF amino acid consensus sequence at their N termini [19]. One of these ENF peptides has been reported to be induced by viral infection in silkworms [20] and another from moth larvae has been reported to stimulate aggregation Ferroptosis inhibitor and directed movement of phagocytic hemocytes [21]. By contrast, the non-ENF cytokine, astakine was actually required for infectivity of white spot syndrome virus in haematopoietic cells of the freshwater

crayfish, Pacifastacus leniusculus [22]. Another group of insect cytokine-like peptides that have antiviral activity are called alloferons [23]. These peptides are composed of 12-13 amino acids and they can stimulate natural cytotoxicity of human peripheral blood lymphocytes, induce interferon synthesis in mouse and human models, and enhance antiviral and antitumor activity in mice. Although the effect of these substances on FK228 cell line insect cells has not been reported, it is possible that viprolaxikine may be an alloferon-like substance. If so, it would be the

first alloferon-like substance reported to be produced in an insect cell culture rather than in whole insects. If so, this insect system might constitute a simple model for studying alloferon induction and alloferon control mechanisms in insect cells. Another antiviral protein (AVP) has been described from C6/36 cells persistently infected with Sindbis virus [24]. It was purified to homogeneity and found to be a very hydrophobic peptide of 3200 kDa [25]. When only one clone (U4.4) of naïve C6/36 cells is Molecular motor exposed to AVP for 48 h, the cells not only became refractory to infection by Sindbis virus but also continuously produced AVP and remained refractory to Sindbis virus upon subsequent passage, i.e., they became permanently altered by a single exposure to AVP. AVP had no protective activity against Sinbis virus in BHK-21 mammalian cells [26] and the actual amino acid sequence has not been reported. The requirement for 48 h pre-exposure to obtain protection against Sindbis virus is similar to the requirement of pre-incubation with viprolaxikine for DEN-2 protection in C6/36 cells.