Status of circulating immune complexes, IL8 titers and cryoglobulins in patients with dengue infection

Dengue, a serious viral infection caused by the mosquito vector, Aedes aegyptii, affects about 390 million people annually from more than 125 countries across the globe. However, until now, there is no reliable clinical or laboratory indicator to accurately predict the development of dengue severity. Here, we explored critical pathophysiological determinants like IL8, circulating immune complex (CIC) and cryoglobulin in dengue-infected patients for identification of novel dengue severity biomarker(s). Totally, 100 clinically suspected dengue cases were tested by NS1 ELISA and MAC ELISA for dengue virus aetiology. For control, 49 healthy volunteers were included. Blood profiling (complete hemogram and liver function test) of patient population were done using automated cell counter and standard auto analyzer based biochemical analysis. Serum CIC was quantified by PEG precipitation. Serum cryoglobulins were estimated by Folin assay. Levels of serum IL-8 were assessed by standard sandwich ELISA kits. Patient CIC were further characterized by SDS Gel electrophoresis. Forty per cent of the cases tested positive, of which 11 patients had severe clinical manifestation. The mean ±SEM of cryoglobulin concentration for DHF, DF, and HC were 1.30 ± 0.31, 0.59 ± 0.08 and 0.143 ± 0.009 μg/μl, respectively. Thus, DHF and DF patients have shown 9- and 2.2-fold increase in cryoglobulin levels; and 18- and 5-fold increased CIC, respectively compared to HC patients. The mean ±SEM of CIC-PEG index for DHF, DF and HC were 491 ± 41.22, 146 ± 14.19 and 27.98 ± 2.56, respectively. Raised levels of IL8 titers were also found in all 11 DHF patients. Peak levels of CIC, cryoglobulin and IL8 titers were associated with thrombocytopenia. SDS PAGE analysis of CIC from DHF revealed the presence of at least six protein bands that were not observed in samples from DF and HC. Prediction efficacy of IL8, CIC and cryoglobulin for DHF was determined using the receiver operator characteristic curve (ROC). The area under the curve was 1.00 for IL8, 0.99 for CIC and 0.74 for cryoglobulins. Overall, the results suggest that CIC, IL-8 and cryoglobulins may serve as important laboratory parameters to monitor dengue infection progression.