Insects combat infection by mounting powerful immune responses that are mediated by hemocytes, the fat body, the midgut, the salivary glands and other tissues. Foreign organisms that have entered the body of an insect are recognized by the immune system when pathogen-associated molecular patterns bind host-derived pattern recognition receptors. This, in turn, activates immune signaling pathways that amplify the immune response, induce the production of factors with antimicrobial activity, and activate effector pathways. Among the immune signaling pathways are the Toll, Imd, Jak/Stat, JNK, and insulin pathways. Activation of these and other pathways leads to pathogen killing via phagocytosis, melanization, cellular encapsulation, nodulation, lysis, RNAi-mediated virus destruction, autophagy and apoptosis. This review details these and other aspects of immunity in insects, and discusses how the immune and circulatory systems have co-adapted to combat infection, how hemocyte replication and differentiation takes place (hematopoiesis), how an infection prepares an insect for a subsequent infection (immune priming), how environmental factors such as temperature and the age of the insect impact the immune response, and how social immunity protects entire groups. Finally, this review highlights some underexplored areas in the field of insect immunobiology.

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Insect immunology and hematopoiesis.

American journal of physiology. Cell physiology

An unusual crustacean cardioactive peptide (CCAP) from the pericardial organs of the shore crab Carcinus maenas has been purified to homogeneity by a two-step reversed-phase HPLC procedure. Manual microsequencing using the 4-(N,N-dimethylamino)azobenzene 4'-isothlocyanate/ phenylisothiocyanate double-coupling technique and automat- ed gas-phase sequencing of the oxidized peptide revealed that CCAP is a nonapeptide (M, 957) of the sequence Pro-Phe- Cys-Asn-Ala-Phe-Thr-Gly-Cys-NH2. We have confirmed the sequence by chemical synthesis of the C-terminally amidated and nonamidated forms of the peptide. The presence of the amide group was indicated by lack of susceptibility to car- boxypeptidase A and Y treatment and was confrmed by the observation that the native CCAP comigrated with the amid- ated synthetic peptide on HPLC. Native and synthetic CCAP displayed high accelerating activity on a semi-isolated crab heart preparation, whereas the nonamidated synthetic peptide was of much lower potency. The effect of CCAP was both mno- and chronotropic. The two pericardial organs of one animal yielded 30-40 pmol of extractable CCAP. Its sequence does not resemble that of any known neuropeptide. However, a "mir- ror-image" similarity to vasopressin is conspicuous.

Unusual cardioactive peptide (CCAP) from pericardial organs of the shore crab Carcinus maenas (crustacean neuropeptide/amino acid sequence/cardioactive neurohormone/neurosecretion)

Recent advances in neuropeptide signaling in Drosophila, from genes to physiology and behavior.

The bed bug, Cimex lectularius, has re-established itself as a ubiquitous human ectoparasite throughout much of the world during the past two decades. This global resurgence is likely linked to increased international travel and commerce in addition to widespread insecticide resistance. Analyses of the C. lectularius sequenced genome (650 Mb) and 14,220 predicted protein-coding genes provide a comprehensive representation of genes that are linked to traumatic insemination, a reduced chemosensory repertoire of genes related to obligate hematophagy, host–symbiont interactions, and several mechanisms of insecticide resistance. In addition, we document the presence of multiple putative lateral gene transfer events. Genome sequencing and annotation establish a solid foundation for future research on mechanisms of insecticide resistance, human–bed bug and symbiont–bed bug associations, and unique features of bed bug biology that contribute to the unprecedented success of C. lectularius as a human ectoparasite.

/pdf/unique-features-of-a-global-human-ectoparasite-identified-4s0cllmqg6.pdf

Unique features of a global human ectoparasite identified through sequencing of the bed bug genome

We have reinvestigated the possible presence or absence of the pentapeptide proctolin in Rhodnius prolixus and report here the cloning of the proctolin cDNA. The transcript is highly expressed in the central nervous system (CNS) with some low expression associated with peripheral tissues. The proctolin prepropeptide encodes a single copy of proctolin along with a proctolin-precursor-associated peptide. We have biochemically identified proctolin in CNS extracts and shown its distribution using proctolin-like immunoreactivity. Immunostained processes are found on the salivary glands, female and male reproductive organs, and heart and associated alary muscles. Proctolin-like immunoreactive bipolar neurons are found on the lateral margins of the common oviduct and bursa. Proctolin is biologically active on R. prolixus tissues, stimulating increases in contraction of anterior midgut and hindgut muscles, and increasing heartbeat frequency. Contrary to the previous suggestion that proctolin is absent from R. prolixus, proctolin is indeed present and biologically active in this medically-important bug.

/pdf/the-proctolin-gene-and-biological-effects-of-proctolin-in-c1qv97ssvl.pdf

The Proctolin Gene and Biological Effects of Proctolin in the Blood-Feeding Bug, Rhodnius prolixus

The myosuppressin (MS) gene was cloned from a central nervous system (CNS) cDNA library of the hematophagous insect Rhodnius prolixus and is predicted to contain two introns and three exons. The mRNA transcribed from the myosuppressin gene encodes an 88 amino acid prepropeptide, which results in a mature decapeptide after post-translational modification. When compared with the myosuppressins isolated from other insects, the R. prolixus myosuppressin has a unique amino acid sequence (pQDIDHVFMRFamide), with isoleucine (I) in position 3 and methionine (M) in position 8. Reverse transcriptase (RT)-PCR shows that Rhopr-MS is expressed in the CNS and posterior midgut in R. prolixus and immunohistochemistry suggests that an RFamide-like peptide is present in endocrine-like cells in the midgut. Physiological assays using Rhopr-MS indicate that, despite the unusual M at position 8, it still retains myoinhibitory activity, inhibiting the frequency and reducing the amplitude of contractions in the anterior midgut and hindgut, and decreasing heart rate.

/pdf/an-unusual-myosuppressin-from-the-blood-feeding-bug-rhodnius-ubzty69bgx.pdf

Rosa da Silva

Papers

The Proctolin Gene and Biological Effects of Proctolin in the Blood-Feeding Bug, Rhodnius prolixus

An unusual myosuppressin from the blood-feeding bug Rhodnius prolixus.

Effects of crustacean cardioactive peptide on the hearts of two Orthopteran insects, and the demonstration of a Frank–Starling-like effect

The molecular characterization of the kinin transcript and the physiological effects of kinins in the blood-gorging insect, Rhodnius prolixus.

The regulation of cardiac activity by nitric oxide (NO) in the Vietnamese stick insect, Baculum extradentatum.