Immune Reactions of Vector Insects to Parasites and Pathogens.

This overview initially describes insect immune reactions and then brings together present knowledge of the interactions of vector insects with their invading parasites and pathogens. It is a way of introducing this Special Issue with subsequent papers presenting the latest details of these interactions in each particular group of vectors. Hopefully, this paper will fill a void in the literature since brief descriptions of vector immunity have now been brought together in one publication and could form a starting point for those interested and new to this important area. Descriptions are given on the immune reactions of mosquitoes, blackflies, sandflies, tsetse flies, lice, fleas and triatomine bugs. Cellular and humoral defences are described separately but emphasis is made on the co-operation of these processes in the completed immune response. The paper also emphasises the need for great care in extracting haemocytes for subsequent study as appreciation of their fragile nature is often overlooked with the non-sterile media, smearing techniques and excessive centrifugation sometimes used. The potential vital role of eicosanoids in the instigation of many of the immune reactions described is also discussed. Finally, the priming of the immune system, mainly in mosquitoes, is considered and one possible mechanism is presented.

Reaching the Final Endgame for Constant Waves of COVID-19.

Despite intramuscular vaccines saving millions of lives, constant devastating waves of SARS-CoV-2 infections continue. The elimination of COVID-19 is challenging, but necessary in order to avoid millions more people who would suffer from long COVID if we fail. Our paper describes rapidly advancing and innovative therapeutic strategies for the early stage of infection with COVID-19 so that tolerating continuing cycles of infection should be unnecessary in the future. These therapies include new vaccines with broader specificities, nasal therapies and antiviral drugs some targeting COVID-19 at the first stage of infection and preventing the virus entering the body in the first place. Our article describes the advantages and disadvantages of each of these therapeutic options which in various combinations could eventually prevent renewed waves of infection. Finally, important consideration is given to political, social and economic barriers that since 2020 hindered vaccine application and are likely to interfere again with any COVID-19 endgame.

Dichotomous feedback: a signal sequestration-based feedback mechanism for biocontroller design.

We introduce a new design framework for implementing negative feedback regulation in synthetic biology, which we term 'dichotomous feedback'. Our approach is different from current methods, in that it sequesters existing fluxes in the process to be controlled, and in this way takes advantage of the process's architecture to design the control law. This signal sequestration mechanism appears in many natural biological systems and can potentially be easier to realize than 'molecular sequestration' and other comparison motifs that are nowadays common in biomolecular feedback control design. The loop is closed by linking the strength of signal sequestration to the process output. Our feedback regulation mechanism is motivated by two-component signalling systems, where a second response regulator could be competing with the natural response regulator thus sequestering kinase activity. Here, dichotomous feedback is established by increasing the concentration of the second response regulator as the level of the output of the natural process increases. Extensive analysis demonstrates how this type of feedback shapes the signal response, attenuates intrinsic noise while increasing robustness and reducing crosstalk.

Inhibition by Marine Algae of Chikungunya Virus Isolated From Patients in a Recent Disease Outbreak in Rio de Janeiro.

Chikungunya virus (CHIKV) infection is one of the most challenging re-emergent diseases caused by a virus, and with no specific antiviral treatment it has now become a major public health concern. In this investigation, 25 blood samples were collected from patients with characteristic CHIKV symptoms and submitted to a virus isolation protocol, which detected 3 CHIKV isolates. These samples were evaluated by sequencing for the characterization of the strains and any homology to viruses circulating in Brazil during a recent outbreak. These viruses were used for the development of antiviral assays. Subsequently, the inhibitory effects of seaweed extracts on CHIKV replication were studied. The marine species of algae tested were Bryothamnion triquetrum, Caulerpa racemosa, Laurencia dendroidea, Osmundaria obtusiloba, Ulva fasciata, and Kappaphycus alvarezii, all of which are found in different countries including Brazil. The results revealed high levels of CHIKV inhibition, including extracts of O. obtusiloba with inhibition values of 1.25 µg/mL and a selectivity index of 420. Viral inhibition was dependent on the time of addition of extract of O. obtusiloba to the infected cells, with the optimal inhibition occurring up to 16 h after infection. Neuron evaluations with O. obtusiloba were performed and demonstrated low toxicity, and in infected neurons we observed high inhibitory activity in a dose-dependent manner. These results indicate that the algal extracts may be promising novel candidates for the development of therapeutic agents against CHIKV infections.

Lipoproteins from vertebrate host blood plasma are involved in Trypanosoma cruzi epimastigote agglutination and participate in interaction with the vector insect, Rhodnius prolixus.

Chagas disease, infecting ca. 8 million people in Central and South America, is mediated by the protozoan parasite, Trypanosoma cruzi. The parasite is transmitted by the bite of blood sucking triatomine insects, such as Rhodnius prolixus, that had previously fed on parasite-infected vertebrate blood and voided their contaminated feces and urine into the wound. The stages of the parasite life cycle in both the insect vector and human host are well-known, but determinants of infection in the insect gut are complex and enigmatic. This paper examines the possible role of the R. prolixus gut agglutinins in the parasite life cycle. The results, derived from gut extracts made from R. prolixus fed on various diets with different vertebrate blood components, and cross adsorption experiments, showed for the first time that R. prolixus has two distinct gut agglutinins originating from their vertebrate blood meal, one for T. cruzi (the parasite agglutinin, PA) and the other for the erythrocytes (the hemagglutinin, HA). Again, uniquely, the results also demonstrate that these two agglutinins are derived, respectively, from the plasma and erythrocyte components of the vertebrate blood. Subsequent experiments, examining in more detail the nature of the plasma components forming the T. cruzi PA, used fractionated extracts of the vertebrate plasma (high density lipoprotein, HDL; low density lipoprotein, LDL, and delipidated plasma) in agglutination assays. The results confirmed the identity of the PA as a high density lipoprotein (HDL) in the plasma of the vertebrate blood meal which agglutinates parasites in the R. prolixus gut. In addition, the use of single or double labeled HDL in fluorescence and confocal microscopy showed the interaction of the labeled HDL with the parasite surface and its internalization at later times. Finally, results of T. cruzi parasitization of R. prolixus, incorporating various vertebrate blood components, resulted in highly significant increases in infectivity in the presence of HDL from the 2nd day of infection, thus confirming the important role of this molecule in T. cruzi infection of R. prolixus.

Antileukemic Properties of Sesquiterpene Lactones: A Systematic Review.

This review summarizes the reported molecular mechanisms underlying the antileukemic property of Sesquiterpene Lactones (SLs). This systematic review was registered in the PROSPERO database and conducted following the PRISMA Statements. The MeSH terms, Sesquiterpenes, Lactones and Leukemia were used in four databases (Pubmed, Web of Science, Scopus and Bireme). There were 281 studies selected, but after exclusions, due to replication (n = 172) or not following PECOS criteria (n = 24), 148 studies remained. Of the 148 articles, only 22 were submitted to quality assessment and were scored in high level if more than two techniques, to elucidate antileukemic properties, were described, and then data were extracted. The studies mostly used human leukemia cell lines including primary and established cells, with or without chemotherapy resistance. The SLs used were obtained principally from plants. The antileukemic properties of SLs were extracted from 22 high level studies. They included cell death induction, mainly by apoptosis, as well as cell differentiation, cell cycle disruption, leukemia cancer stem cell growth inhibition and NF-κB pathway inhibition; the latter is a promising therapeutic target for lymphoid malignancies. We concluded that, in spite of the necessity of better toxicological profile characterization of SLs, the antileukemic properties of these compounds support the proposal that the SLs are promising candidates for the treatment of leukemia.

Isolation of a larvicidal compound from Piper solmsianum C.DC. (Piperaceae).

The Aedes aegypti mosquito is one of the major vectors of arboviruses. These diseases have re-emerged and the insecticides used nowadays are toxic to mammals and environment and have only been effective in the short-term. In this context, natural products are an alternative. The genus Piper has many active compounds against arthropods, including neolignans. The present study evaluated the larvicidal potential of the n-hexanic extract of Piper solmsianum and eupomatenoid-6, identified by GC-MS and NMR techniques, from this extract against Ae. aegypti. The crude extract (100 µg/mL) killed 80% and 98.3% of larvae in the first and third day, respectively. Eupomatenoid-6 exhibited LD50 of 19.33 µM and LD90 of 28.68 µM and was then assayed in human fibroblast cells (MRC5), showing an IC50 of 39.30 µM with estimated LD50 of 42.26 mmol/kg. Our results indicate eupomatenoid-6 as a potent insecticide with relatively low toxicity for mammals.

Detection and preliminary physico-chemical properties of antimicrobial components in the native excretions/secretions of three species of Chrysomya (Diptera, Calliphoridae) in Brazil.

Antibiotic-resistant bacteria in hospitals and communities increasingly threaten public health in Brazil and the rest of the World. There is an urgent need for additional antimicrobial drugs. Calliphorid blowfly larvae are a rich source of antimicrobial factors but the potential of Neotropical species has been neglected. This preliminary study evaluates the antimicrobial activity of the native excretions/secretions of larvae of three species of Brazilian calliphorids, Chrysomya megacephala, Chrysomya albiceps and Chrysomya putoria. Native excretions/secretions were collected from third instar larvae, sterile filtered and tested for antibacterial activity against Staphylococcus aureus 9518, Escherichia coli K12 4401 and Serratia marcescens 365. Turbidometric assays were made in micro-plates, using an ELISA reader, with readings taken up to 22 h. Bacterial suspensions at the start and end of each experiment were also serially diluted, spread on nutrient agar plates and then colony forming units counted. The physico-chemical characteristics of the native excretions/secretions were also tested by freezing/thawing, boiling, and protease digestion. The native excretions/secretions of larvae from these three Chrysomya species significantly inhibited bacterial growth. Therefore, Brazilian calliphorid flies could potentially provide new classes of antibiotics.

Maggot therapy: the science and implication for CAM part II-maggots combat infection.

Maggot therapy employs the use of freshly emerged, sterile larvae of the common green-bottle fly, Phaenicia (Lucilia) sericata, and is a form of artificially induced myiasis in a controlled clinical situation. Maggot therapy has the following three core beneficial effects on a wound: debridement, disinfection and enhanced healing. In part II of this review article, we discuss clinical infections and the evidence supporting the potent antibacterial action of maggot secretions. Enhancement of wound healing by maggots is discussed along with the future of this highly successful, often controversial, alternative treatment.

Maggot Therapy: The Science and Implication for CAM Part I-History and Bacterial Resistance.

It is now a universally acknowledged fact that maggot therapy can be used successfully to treat chronic, long-standing, infected wounds, which have previously failed to respond to conventional treatment. Such wounds are typically characterized by the presence of necrotic tissue, underlying infection and poor healing. Maggot therapy employs the use of freshly emerged, sterile larvae of the common green-bottle fly, Phaenicia (Lucilia) sericata, and is a form of artificially induced myiasis in a controlled clinical situation. In this review article, we will discuss the role of maggots and their preparation for clinical use. Maggot therapy has the following three core beneficial effects on a wound: debridement, disinfection and enhanced healing. In part I we explore our current understanding of the mechanisms underlying these effects.