Insect Immunity Shows Specificity in Protection upon Secondary Pathogen Exposure

Abstract

Immunological memory in vertebrates, conferring lasting specific protection after an initial pathogen exposure, has implications for a broad spectrum of evolutionary, epidemiological, and medical phenomena . However, the existence of specificity in protection upon secondary pathogen exposure in invertebrates remains controversial . To separate this functional phenomenon from a particular mechanism, we refer to it as specific immune priming. We investigate the presence of specific immune priming in workers of the social insect Bombus terrestris. Using three bacterial pathogens, we test whether a prior homologous pathogen exposure gives a benefit in terms of long-term protection against a later challenge, over and above a heterologous combination. With a reciprocally designed initial and second-exposure protocol (i.e., all combinations of bacteria were tested), we demonstrate, even several weeks after the clearance of a first exposure, increased protection and narrow specificity upon secondary exposure. This demonstrates that the invertebrate immune system is functionally capable of unexpectedly specific and durable induced protection. Ultimately, despite general broad differences between vertebrates and invertebrates, the ability of both immune systems to show specificity in protection suggests that their immune defenses have found comparable solutions to similar selective pressures over evolutionary time.

Evidence for antiseptic behaviour towards sick adult bees in honey bee colonies

“…Deformed wing virus infected bees pose a threat for the colony as: (1) quite all the A. mellifera colonies are naturally infested by the Varroa destructor mite and the phoretic mites are able to horizontally transmit DWV to adult healthy bees when feeding on the bees' haemolymph (Santillán-Galicia et al, 2010); (2) DWV can be transmitted horizontally to larvae via larval food containing DWV (Gisder et al, 2009;Yue and Genersch, 2005); (3) the detection of DWV in the midgut content (Fievet et al, 2006) and bee faeces implies the possibility of a faecal-oral-route of transmission between adult bees. Even if handling sick individuals could increase horizontal transmission risk, there are evidence that this behaviour could be also trigger immunization of the hygenic individuals as demonstrate in termites (Traniello et al, 2002), in ants (Ugelvig and Cremer, 2007) and in bumblebee (Sadd and Schmid-Hempel, 2006). As consequence, removing sick nestmates from the colony could represent a better solution to counteract epidemics than leave them into the nest.…”

A summer heat wave decreases the immunocompetence of the mesograzer, Idotea baltica

“…Invertebrates rely exclusively on their innate immunity and lack a mechanistic homologue of the adaptive arm of the vertebrate immune system (Janeway and Medzhitov 2002), although some recent work suggests speciWcity upon secondary exposure to parasites and pathogens (Kurtz and Franz 2003;Sadd and Schmid-Hempel 2006;). The immune system of invertebrates can be divided into cellular and humoral defences.…”

Foster carers influence brood pathogen resistance in ants

“…Intercolony variation may emerge from differences in the innate immunity of colony members or differences in their microbiota. Alternatively, some colonies may have previously encountered this pathogen prior to collection, which could result in a more effective response upon secondary exposure [9,41,42; but see 33]. Further work is needed to elucidate the mechanisms underlying the large variation in pathogen resistance among colonies and the non-genetic transmission of resistance to the developing brood.…”