Association between proinflammatory cytokines and lipid peroxidation in patients with severe dengue disease around defervescence.

OBJECTIVES: Proinflammatory cytokines and the oxidative stress response are reported to be involved in dengue viral disease. The present study investigated the correlation of proinflammatory cytokines and lipid peroxidation with dengue severity. METHODS: Clinical samples from 27 dengue fever (DF) cases, 30 dengue haemorrhagic fever (DHF) cases, and 24 dengue shock syndrome (DSS) cases were studied around defervescence, along with samples from 30 healthy controls. Plasma samples were analysed for tumour necrosis factor alpha (TNF-α) and interferon gamma (IFN-γ) by ELISA and for malondialdehyde (MDA) by thiobarbituric acid assay. RESULTS: Dengue-infected individuals had significantly higher levels of TNF-α, IFN-γ, and MDA in comparison to controls. The ratio of TNF-α to IFN-γ was significantly higher in DHF and DSS than in DF. A TNF-α/IFN-γ ratio value of 5.69 around defervescence predicted DHF and DSS with moderate accuracy and thus may serve as an indicator to study dengue severity. The study observed a significant positive correlation of lipid peroxides with TNF-α levels and the TNF-α/IFN-γ ratio in severe dengue cases. CONCLUSIONS: We propose that the oxidative stress response induced by the dengue virus may trigger the inflammatory cytokine responses in dengue severity and thereby contributes to the pathogenesis of the disease; however the interplay between the oxidative response and inflammatory activity in disease virulence needs further study.

Transferrin in the mosquito, Culex quinquefasciatus Say (Diptera: Culicidae), up-regulated upon infection and development of the filarial parasite, Wuchereria bancrofti (Cobbold) (Spirurida: Onchocercidae).

Transferrin is a defence protein known to be up-regulated upon infection of parasites/pathogens in Aedes aegypti mosquito. However, no information is available on its up-regulation in Culex quinquefasciatus, the vector of bancroftian filarial parasite. In the present study, enhancement of transferrin in C. quinquefasciatus infected with Wuchereria bancrofti is demonstrated through amplification of the specific mosquito transcript, its sequencing, cloning, and expression. By using two oligonucleotide primers, a 950-bp polymerase chain reaction product was obtained from the first strand cDNA made from RNA of C. quinquefasciatus infected with W. bancrofti. A 707-bp sequence encoding the mature portion of transferrin was confirmed by sequencing the product. This is the first report of transferrin expression in C. quinquefasciatus. The deduced amino acid sequence shared 85% homology with A. aegypti transferrin precursor molecule. Western blot analysis of haemolymph proteins of infected C. quinquefasciatus with antibodies raised against recombinant transferrin protein showed binding to a 66-kDa protein, confirming its identity as transferrin. Hence, this molecule also could be added to the list of immune molecules of C. pipiens group, such as the defensin, gambicin, and cecropin, which are already known.

Changes in the haemocyte population of the mosquito, Culex quinquefasciatus, following infection with the filarial parasite, Wuchereria bancrofti.

The mosquito Culex quinquefasciatus Say (Diptera: Culicidae) is the vector of the filarial parasite Wuchereria bancrofti (Cobbold) (Spirurida: Onchocercidae), which causes human bancroftian filariasis. Information on the mosquito humoral response against the filarial parasite during the process of its infection and development is important, as it decides the vector competence of the mosquito. Visible changes in the haemocyte population of mosquito, if any, will be an indicator of the possible humoral factors. The present study was aimed at investigating changes in the populations of various types of haemocytes of Cx. quinquefasciatus following infection with W. bancrofti. On day 2 post-feeding on microfilaraemic blood, the haemolymph perfusate of infected mosquitoes with L1 stage of the parasite showed 44.1% granulocytes, 42% prohaemocytes and 13.9% plasmatocytes, whereas that of the control mosquitoes fed on amicrofilaraemic blood showed 63.4% plasmatocytes, 22.2% prohaemocytes and 14.4% granulocytes. Differences in the population numbers of haemocyte types between the infected and control were significant (P > 0.05). However, the mosquitoes examined on day 6 post-feeding, when the parasite was in L2 stage, did not show any such changes. But, similar changes reappeared on day 12 in mosquitoes with L3 stage of the parasite. The observed haemocyte population changes indicate the possibility of some amount of humoral immune response, through the production of certain immune molecules, in Cx. quinquefasciatus infected with W. bancrofti. The nature and exact role of such a response on the filarial parasite development need further investigation.