Trans-generational immune priming in the mealworm beetle protects eggs through pathogen-dependent mechanisms imposing no immediate fitness cost for the offspring.

Immune-challenged mothers can improve their offspring immunity through trans-generational immune priming (TGIP). In insects, TGIP endows the offspring with lifetime immunity, including the eggs, which are likely exposed soon after maternal infection. Egg protection may rely on the transfer of maternal immune effectors to the egg or/and the induction of egg immune genes. These respective mechanisms are assumed to have early-life fitness costs of different magnitude for the offspring. We provide evidence in the mealworm beetle Tenebrio molitor that enhanced egg immunity following a maternal immune challenge is achieved by both of these mechanisms but in a pathogen-dependent manner. While previously found having late-life fitness costs for the offspring, TGIP here improved egg hatching success and early larval survival, in addition of improving offspring immunity. These results suggest that early-life of primed offspring is critical in the optimization of life history trajectory of this insect under trans-generational pathogenic threats.

Detrimental interactions of neonicotinoid pesticide exposure and bumblebee immunity.

Pesticides are well known to have a number of ecological effects. However, it is only now becoming understood that sublethal exposures may have effects on nontarget insects of conservation concern through interactions with immunity, thus increasing detrimental impacts in the presence of pathogens. Pesticides and pathogens are suggested to have played a role in recent declines of several wild bee pollinators. Compromised immunity from exposure to widely used neonicotinoids has been demonstrated in honeybees, but further research on interactions between neonicotinoids and immunity in other important bees is lacking. In this study, adult workers of the bumblebee Bombus impatiens received 6-day pulses of either low (0.7 ppb) or high (7 ppb) field realistic doses of the neonicotinoid imidacloprid prior to assaying immunity and survival following a nonpathogenic immune challenge. High-dose imidacloprid exposure reduces constitutive levels of phenoloxidase, an enzyme involved in melanization. Hemolymph antimicrobial activity initially increases in all groups following an immune challenge, but while heightened activity is maintained in unexposed and low imidacloprid dose groups, it is not maintained in the high exposure dose bees, even though exposure had ceased 6 days prior. Additionally, imidacloprid exposure followed by an immune challenge significantly decreased survival probability relative to control bees and those only immune challenged or imidacloprid exposed. A temporal lag for immune modulation and combinatorial effects on survival suggest that resource-based trade-offs may, in part, contribute to the detrimental interactions. These interactions could have health consequences for pollinators facing multiple stresses of sublethal neonicotinoid exposure and pathogens.

Effects of the probiotic Arthrobacter sp. CW9 on the survival and immune status of white shrimp (Penaeus vannamei).

UNLABELLED: The probiotic Arthrobacter sp. CW9 isolated from guts of white shrimp (Penaeus vannamei) was used to improve the survival rate, growth rate and immune status of white shrimp (P. vannamei). Arthrobacter sp. CW9 was added to the saline rearing water at 0, 10(5), 10(6) and 10(7) CFU ml(-1) once every 5 days during the 24-day breeding experiment. The probiotic group had significantly higher survival rates, mean shrimp weights, phenoloxidase activity, phagocytic activity and clearance efficiency compared with the control group (P < 0.05). Therefore, Arthrobacter sp. CW9 has both probiotic and immunostimulatory properties. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrates that Arthrobacter sp. CW9 has both probiotic and immunostimulatory properties. Such new strain therefore represents an alternative to the use of white shrimp (Penaeus vannamei) culture. New bacterial having both probiotic and immunostimulatory properties are the major novelty of this study. The results are of industrial relevance.

Ecological effects on gut bacterial communities in wild bumblebee colonies.

1. Animal hosts harbour diverse and often specific bacterial communities (microbiota) in their gut. These microbiota can provide crucial services to the host such as aiding in digestion of food and immune defence. However, the ecological factors correlating with and eventually shaping these microbiota under natural conditions are poorly understood. 2. Bumblebees have recently been shown to possess simple and highly specific microbiota. We here examine the dynamics of these microbiota in field colonies of the bumblebee Bombus terrestris over one season. The gut bacteria were assessed with culture-independent methods, that is, with terminal restriction fragment length profiles of the 16S rRNA gene. 3. To further understand the factors that affect the microbiota, we experimentally manipulated field-placed colonies in a fully factorial experiment by providing additional food or by priming the workers' immune system by injecting heat-killed bacteria. We furthermore looked at possible correlates of diversity and composition of the microbiota for (i) natural infections with the microbial parasites Crithidia bombi and Nosema bombi, (ii) bumblebee worker size, (iii) colony identity, and (iv) colony age. 4. We found an increase in diversity of the microbiota in individuals naturally infected with either C. bombi or N. bombi. Crithidia bombi infections, however, appear to be only indirectly linked with higher microbial diversity when comparing colonies. The treatments of priming the immune system with heat-killed bacteria and additional food supply, as well as host body size, had no effect on the diversity or composition of the microbiota. Host colony identity had only a weak effect on the composition of the microbiota at the level of resolution of our method. We found both significant increases and decreases in the relative abundance of selected bacterial taxa over the season. 5. We present the first study on the ecological dynamics of gut microbiota in bumblebees and identify parasite infections, colony identity and colony age as important factors influencing the diversity and composition of the bacterial communities. The absence of an effect of our otherwise effective experimental treatments suggests a remarkable ability of the host to maintain a homoeostasis in this community under widely different environments.

Relationship between maternal transfer of immunity and mother fecundity in an insect.

Trans-generational immune priming (TGIP) corresponds to the plastic adjustment of offspring immunity as a result of maternal immune experience. TGIP is expected to improve mother's fitness by improving offspring individual performance in an environment where parasitism becomes more prevalent. However, it was recently demonstrated that maternal transfer of immunity to the offspring is costly for immune-challenged female insects. Thus, these females might not provide immune protection to all their offspring because of the inherent cost of other fitness-related traits. Females are therefore expected to adjust their investment to individual offspring immune protection in ways that maximize their fitness. In this study, we investigated how bacterially immune-challenged females of the mealworm beetle, Tenebrio molitor, provision their eggs with immune protection according to egg production. We found that immune-challenged females provide a variable number of their eggs with internal antibacterial activity along egg-laying bouts. Furthermore, within the first immune-protected egg-laying bout (2-4 days after the maternal immune challenge), the number of eggs protected was strongly dependent on the number of eggs produced. Immune-challenged females might therefore adjust their investment into TGIP and fecundity according of their individual perception of the risk of dying from the infection and the expected parasitic conditions for the offspring.

Facultative but persistent trans-generational immunity via the mother's eggs in bumblebees.

It is widely acknowledged that a mother, and the maternal environment, can have a profound effect on the phenotype of her offspring. For example, immunocompetent vertebrate mothers can pass on immune factors to their otherwise immune naïve offspring. Recently, it has also been demonstrated in invertebrates that maternal contact with pathogens and immune elicitors can have a positive impact on offspring resistance and immune system components. Here, using a cross-fostering design, we show that trans-generational immune priming in a social insect, similar to birds, takes place through factors in the eggs, with effects persisting into adult worker offspring. Additionally, eggs from immune-challenged mothers are imbued with increased internal antibacterial activity when they are laid.

Use of Arthrobacter davidanieli as a live vaccine against Renibacterium salmoninarum and Piscirickettsia salmonis in salmonids.

Arthrobacter davidanieli (proposed species nomenclature) is a non-pathogenic Gram-variable bacterium related to, but taxonomically distinct from, Renibacterium salmoninarum, the aetiological agent of bacterial kidney disease (BKD). We have demonstrated that vaccination with live A. davidanieli is effective against BKD in Atlantic salmon (Salmo salar) showing above 80 relative percent survival in experimental challenge trials. Good protection was also demonstrated in long-term field trials where Atlantic salmon were naturally exposed to R. salmoninarum challenge until 23 months after vaccination. The same vaccine, which is licensed in Canada against BKD has also proved effective in reducing mortality from experimental challenge of coho salmon (Oncorhynchus kisutch) with Piscirickettsia salmonis, the causative agent of piscirickettsiosis. Under field conditions in Chile, use of the vaccine led to a significant reduction in piscirickettsiosis mortality in coho salmon over 10 months following sea transfer. The vaccine strain is unique in that it is the first live organism to be licensed as a vaccine for use in aquaculture. Potential mechanisms of protection against the two taxonomically disparate pathogens are discussed.

Efficacy of cellular vaccines and genetic adjuvants against bacterial kidney disease in chinook salmon (Oncorhynchus tshawytscha).

DNA adjuvants and whole bacterial cell vaccines against bacterial kidney disease (BKD) were tested in juvenile chinook salmon. Whole cell vaccines of either a nonpathogenic Arthrobacter spp. or an attenuated Renibacterium salmoninarum strain provided limited prophylactic protection against acute intraperitoneal challenge with virulent R. salmoninarum, and the addition of either synthetic oligodeoxynucleotides or purified R. salmoninarum genomic DNA as adjuvants did not increase protection. However, a combination of both whole cell vaccines significantly increased survival among fish naturally infected with R. salmoninarum, and the surviving fish treated with the combination vaccine exhibited reduced levels of bacterial antigens in the kidney. This is the first demonstration of a potential therapeutic effect of a whole cell vaccine against BKD.

Response of furniture factory workers to work-related airborne allergens.

The aim of this work was to determine the reactivity of furniture factory workers to microbial allergens associated with wood dust. Allergological examinations by skin and precipitin tests were performed in 48 workers employed in a factory producing furniture from fibreboards and chipboards, and in 32 healthy urban dwellers not exposed to organic dusts (referents). The skin test was performed by the intradermal method with the saline extracts of the cultures of 3 microbial species (Rahnella sp., Arthrobacter globiformis, Aspergillus fumigatus) associated with wood dust. Skin reactions were recorded after 20 minutes, 8 hours and 24 hours and graded 1-4, depending on the diameter of the reaction. The agar-gel test for the presence of precipitins in serum was performed with the extracts of 15 microbial isolates. The furniture factory workers showed a high skin response to the extracts of environmental microbes. The frequency of early grade 2 reactions (diameter 10 mm) to the extract of Rahnella sp. was 64.6% among furniture workers, being significantly higher (p < 0.001) compared to reference group (18.7%). High frequencies of grade 2 reactions in furniture workers were also found with the extracts of A. globiformis and A. fumigatus (52.1% and 62.5%, respectively). The frequencies of grade 2 delayed (after 8 h) and late (after 24 h) reactions to Rahnella sp. in furniture workers were non-specifically high (97.9%/93.7%) while the response rates to A. globiformis and A. fumigatus were much lower (10.4%/25.0%, and 4.2%/37.5%, respectively). In agar-gel test for detection of precipitins, in most cases very low percentages of positive reactions (0-2.1%) were noted in furniture factory workers. The only exception was a high percentage of positive reactions (27.1%) to the antigen of Pseudomonas maltophilia, which was significantly greater in furniture workers compared to the reference group (p < 0.01). The obtained results suggest that early allergic reactions to microorganisms associated with wood dust are common among workers of furniture industry, which may increase a potential risk of work-related disease in this occupational group.

Immunodiffusion studies of ribosomes in classification of mycobacteria and related taxa.

Ribosomal preparations consisting of crude ribosomes (CR), 30S subunits (30S) and 16S core particles (16S) from four strains of the species Mycobacterium bovis (BCG), Mycobacterium fortuitum, Mycobacterium phlei and Mycobacterium smegmatis were analyzed by immunodiffusion technique for taxonomical purposes. The ribosomal preparations tested contained several interspecies cross-reacting precipitinogens. The number of precipitinogens demonstrated at the homologous reactions was generally larger than the number of precipitinogens shown at the heterologous reactions indicating a probable presence of species-specific antigens in ribosomes. The largest number of possible species-specific precipitinogens was demonstrated when crude ribosomal preparations were studied. However, such precipitinogens were also shown in the 30S subunits and they were individually analyzed. The 16S core particles were dominated by cross-reacting precipitinogens. The number of ribosomal precipitinogens shared by M. phlei and M. smegmatis was large indicating a close taxonomical relationship between these two species. Apart from the four mycobacterial strains studied, 15 other strains representing the genera Mycobacterium, Arthrobacterium, Corynebacterium, Kurthia, Nocardia and Rhodococcus were included in the study. The presence of intergenerically cross-reacting precipitinogens in the ribosomal preparations was demonstrated.

Inabilities as an immunoadjuvant of cell walls of the group B peptidoglycan types and those of arthrobacters.

The cell walls from several bacterial species whose peptidoglycans are the group B types (Schleifer and Kandler) and those of two arthrobacters were shown to be inactive or only weakly active as an immunoadjuvant in both induction of delayed-type hypersensitivity and stimulation of circulating antibody levels to ovalbumin when administered to guinea pigs as a water-in-oil emulsion, in sharp contrast to the adjuvant-active cell walls of the group A peptidoglycan types which were previously studied. The possible reason for the inabilities as an adjuvant of these cell walls was discussed in relation to the chemical structures of peptidoglycans.