Mosquito-borne viral diseases and potential transmission blocking vaccine candidates

Antidiabetic effects of two naphthoquinones from the branches and leaves of Tectona grandis and possible mechanism

Tectona grandis is a Dai medicine that plays an important role in traditional medicine in India, Myanmar, West Africa, and Yunnan Province in China. T. grandis was recorded as an anti-diabetic herb in the Ayurvedic Pharmacopoeia; however, its potential antidiabetic components and possible mechanisms of action have almostly not been described to far. To completely comprehend the pharmacological components and therapeutic potential of T. grandis, we isolated chemical components from the plant's leaves and branches, evaluated their antidiabetic activities, and explored the possible mechanisms of active compounds using molecular docking and network pharmacology. In this study, two new quinones (1-2) and eighteen known compounds (3-20) were isolated and identified from T. grandis. Except for the new quinones 1 and 2, compounds 4, 11-12, 14-15, 18-20 were separated from T. grandis for the first time. The naphthoquinones 1 and 3 showed significant antidiabetic activities in α-glucosidase inhibition assay (IC50: 92.52 ± 5.05 and 45.37 ± 1.50 μM, respectively), glucose uptake assay (Inhibition rate: 63.90 ± 1.04 % and 65.41 ± 1.96 %, respectively) and preadipocyte differentiation inhibition assay (Lipid droplet content decreased by 8.49 ± 0.71 % and 13.89 ± 0.29 %, respectively, compared to the model group). Our study also revealed that T. grandis might treat diabetes by targeting CASP3, ESR1, and PTGS2. This study provided important support for the traditional usage of T. grandis as an antidiabetic herb by identifying its antidiabetic components and possible mechanism.

Molecular characterization, expression and in-silico analysis of fibrinogen-related protein 1 (frep1) in malaria vector Anopheles stephensi

BACKGROUND

Fibrinogen-related protein 1 (frep1) is a member of the pattern-recognizing receptor family (PRR) which generates an innate immune response after recognizing the pattern associated molecular pattern (PAMP) that occurs on the surface of microorganisms. The main objective of this study is to characterize frep1 and its in-silico analysis in Anopheles stephensi.

METHODS AND RESULT

The DNA was extracted from female Anopheles stephensi. PCR was performed for complete analysis of frep1 using specific primers. The gene sequence of frep1 was identified by Sanger sequencing. The bioinformatics structure analysis approach revealed the presence of 3 exons and 4 introns in the frep1. The sequence of frep1 was submitted to NCBI GeneBank with accession number ON817187.1. Quantitative real-time PCR was performed to analyze frep1 expression. At the developmental stage, frep1 is highly expressed in the L1 stage, egg, and adult female mosquito. In addition, frep1 is highly expressed in the tissue fat body, midgut, and salivary gland. After blood-fed, an upregulation of frep1 at 48 h in the midgut, and downregulation in fat body were observed at different time intervals.

CONCLUSION

The genomic data of frep1 is encoded by 12,443 bp. The frep1 has a significant role in the early metamorphosis. Its expression in fat body and midgut suggests it could be important for fat metabolism and post-blood digestion. The conserved domain could be targeted for vector control. Further study is required to elucidate its function against malaria parasites to confirm its agonist role in malaria transmission.

Adenovirus vector-based vaccines as forefront approaches in fighting the battle against flaviviruses

Flaviviruses are arthropod-borne viruses (arboviruses) that have been recently considered among the significant public health problems in defined geographical regions. In this line, there have been vaccines approved for some flaviviruses including dengue virus (DENV), Japanese encephalitis virus (JEV), yellow fever virus (YFV), and tick-borne encephalitis virus (TBEV), although the efficiency of such vaccines thought to be questionable. Surprisingly, there are no effective vaccine for many other hazardous flaviviruses, including West Nile and Zika viruses. Furthermore, in spite of approved vaccines for some flaviviruses, for example DENV, alternative prophylactic vaccines seem to be still needed for the protection of a broader population, and it originates from the unsatisfying safety, and the efficacy of vaccines that have been introduced. Thus, adenovirus vector-based vaccine candidates are suggested to be effective, safe, and reliable. Interestingly, recent widespread use of adenovirus vector-based vaccines for the COVID-19 pandemic have highlighted the importance and feasibility of their widespread application. In this review, the applicability of adenovirus vector-based vaccines, as promising approaches to harness the diseases caused by Flaviviruses, is discussed.

The worldwide seroprevalence of DENV, CHIKV and ZIKV infection: A systematic review and meta-analysis

BACKGROUND

As the three major arthropod-borne viruses, dengue virus (DENV), chikungunya virus (CHIKV), and zika virus (ZIKV) are posing a growing threat to global public health and socioeconomic development. Our study aimed to systematically review the global seroprevalences of these arboviruses from existing publications.

METHODS

Articles published between Jan 01, 2000 and Dec 31, 2019 in the databases of Embase, Pubmed and Web of Science were searched and collected. Countries or areas with known local presence of Aedes vector mosquitoes were included. Random effects model was utilized to estimate the pooled seroprevalences and the proportion of inapparent infection.

RESULTS

Out of 1375, a total of 133 articles involving 176,001 subjects were included for our analysis. The pooled seroprevalences of DENV, CHIKV and ZIKV were 38%, 25% and 18%, respectively; and their corresponding proportions of inapparent infections were 80%, 40% and 50%. The South-East Asia Region had the highest seroprevalences of DENV and CHIKV, while the Region of the Americas had the highest seroprevalence of ZIKV. The seroprevalences of DENV and CHIKV were similar when comparing developed and developing countries, urban and rural areas, or among different populations. In addition, we observed a decreased global seroprevalences in the new decade (2010-2019) comparing to the decade before (2000-2009) for CHIKV. For ZIKV, the positive rates tested with the nucleic acid detection method were lower than those tested with the antibody detection method. Lastly, numerous cases of dual seropositivity for CHIKV and DENV were reported.

CONCLUSIONS

Our results revealed a varied prevalence of arbovirus infections in different geographical regions and countries, and the inapparent infection accounted an unneglected portion of infections that requires more attention. This study will shed lights on our understanding of the true burden of arbovirus infections and promote appropriate vaccination in the future.

Vertebrate Responses against Arthropod Salivary Proteins and Their Therapeutic Potential

The saliva of hematophagous arthropods contains a group of active proteins to counteract host responses against injury and to facilitate the success of a bloodmeal. These salivary proteins have significant impacts on modulating pathogen transmission, immunogenicity expression, the establishment of infection, and even disease severity. Recent studies have shown that several salivary proteins are immunogenic and antibodies against them may block infection, thereby suggesting potential vaccine candidates. Here, we discuss the most relevant salivary proteins currently studied for their therapeutic potential as vaccine candidates or to control the transmission of human vector-borne pathogens and immune responses against different arthropod salivary proteins.

Developing a Vaccine to Block West Nile Virus Transmission: In Silico Studies, Molecular Characterization, Expression, and Blocking Activity of Culex pipiens mosGCTL-1

BACKGROUND

Mosquito galactose-specific C-type lectins (mosGCTLs), such as mosGCTL-1, act as ligands to facilitate the invasion of flaviviruses like West Nile virus (WNV). WNV interacts with the mosGCTL-1 of Aedes aegypti (Culicidae) and facilitates the invasion of this virus. Nevertheless, there is no data about the role of mosGCTL-1 as a transmission-blocking vaccine candidate in Culex pipiens, the most abundant Culicinae mosquito in temperate regions.

METHODS

Adult female Cx. pipiens mosquitoes were experimentally infected with a WNV infectious blood meal, and the effect of rabbit anti-rmosGCTL-1 antibodies on virus replication was evaluated. Additionally, in silico studies such as the prediction of protein structure, homology modeling, and molecular interactions were carried out.

RESULTS

We showed a 30% blocking activity of Cx. pipiens mosGCTL-1 polyclonal antibodies (compared to the 10% in the control group) with a decrease in infection rates in mosquitoes at day 5 post-infection, suggesting that there may be other proteins in the midgut of Cx. pipiens that could act as cooperative-receptors for WNV. In addition, docking results revealed that WNV binds with high affinity, to the Culex mosquito lectin receptors.

CONCLUSIONS

Our results do not support the idea that mosGCTL-1 of Cx. pipiens primarily interacts with WNV to promote viral infection, suggesting that other mosGCTLs may act as primary infection factors in Cx. pipiens.