Dengue Virus Specific T-Cell Responses Correlated with Disease Severity

Dengue virus (DENV) is the cause of the most common mosquito-borne viral infection worldwide, and over half of the global population live in areas where there is intense dengue transmission putting them at risk of dengue infection.

Dengue virus causes 390 million infections annually, of which nearly a quarter are clinically apparent causing a spectrum of disease phenotypes ranging from mild dengue fever (DF) to dengue hemorrhagic fever (DHF). DHF is defined by a transient increase in vascular permeability resulting in plasma leakage, with high fever, bleeding, thrombocytopenia and haemoconcentration, which can lead to dengue shock syndrome (DSS).

Scientists at the University of Sri Jayewardenepura (Nugegoda, Sri Lanka) and their colleagues recruited 74 adult patients with acute dengue infection with between days four to eight of illness. Patients with ultrasound scan evidence of plasma leakage (those who had pleural effusions or ascites) were classified as having DHF, 45 patients had DHF and 29 patients had dengue fever (DF) of the 74 patients recruited for the study.

Acute dengue infection was confirmed in serum samples using polymerase chain reactions (PCR) and dengue antibody detection. Dengue antibody assays were completed using a commercial capture-IgM and IgG ELISA. RNA was extracted from the serum samples and multiplex quantitative real-time PCR was performed as previously described using the CDC real time PCR assay for detection of the dengue virus, and modified to quantify the DENV.

The team used ex vivo IFNγ ELISpot assays and determined the frequency of dengue viral peptide (DENV)-NS3, NS1 and NS5 responsive T cells in 74 adult patients with acute dengue infection and examined the association of responsive T cell frequency with the extent of viremia and clinical disease severity. The spots were enumerated using an automated ELISpot reader.

The team reported that found that total DENV-specific and DENV-NS3-specific T cell responses, were higher in patients with dengue fever (DF), when compared to those with dengue hemorrhagic fever (DHF). In addition, those with DF had significantly higher DENV-specific T cell responses on day four of infection compared to those who subsequently developed DHF. DENV peptide specific T cell responses inversely correlated with the degree of viremia, which was most significant for DENV-NS3 specific T cell responses. The frequency of T cell responses to NS1, NS5 and pooled DENV peptides, correlated with the degree of thrombocytopenia but had no association with levels of liver transaminases. In contrast, total DENV-IgG inversely correlated with the degree of thrombocytopenia and levels of liver transaminases.

The authors concluded that early appearance of DENV-specific T cell IFNγ responses before the onset of plasma leakage appears to associate with milder clinical disease and resolution of viremia, suggesting a protective role in acute dengue infection. The study was published on October 1, 2018, in the journal Public Library of Science Neglected Tropical Diseases.

Related Links:
University of Sri Jayewardenepura