Kinetics of viremia and NS1 antigenemia are shaped by immune status and virus serotype in adults with dengue

Abstract

Background: Dengue is a major public health problem in tropical and subtropical countries. Exploring the relationships between virological features of infection with patient immune status and outcome may help to identify predictors of disease severity and enable rational therapeutic strategies.

Methods: Clinical features, antibody responses and virological markers were characterized in Vietnamese adults participating in a randomised controlled treatment trial of chloroquine.

Results: Of the 248 patients with laboratory-confirmed dengue and defined serological and clinical classifications 29 (11.7%) had primary DF, 150 (60.5%) had secondary DF, 4 (1.6%) had primary DHF and 65 (26.2%) had secondary DHF. DENV-1 was the commonest serotype (57.3%), then DENV-2 (20.6%), DENV-3 (15.7%) and DENV-4 (2.8%). DHF was associated with secondary infection (Odds ratio = 3.13, 95% CI 1.04-12.75). DENV-1 infections resulted in significantly higher viremia levels than DENV-2 infections. Early viremia levels were higher in DENV-1 patients with DHF than with DF, even if the peak viremia level was often not observed because it occurred prior to enrolment. Peak viremias were significantly less often observed during secondary infections than primary for all disease severity grades (P = 0.001). The clearance of DENV viremia and NS1 antigenemia occurs earlier and faster in patients with secondary dengue (P<0.0001). The maximum daily rate of viremia clearance was significantly higher in patients with secondary infections than primary (P<0.00001).

Conclusions: Collectively, our findings suggest that the early magnitude of viremia is positively associated with disease severity. The clearance of DENV is associated with immune status, and there are serotype dependent differences in infection kinetics. These findings are relevant for the rational design of randomized controlled trials of therapeutic interventions, especially antivirals.

Figure 1. Magnitude of DENV viremia by illness day.

Levels of DENV-1, -2, -3 and -4 genome equivalent cDNA copies per millilitre were determined in serial plasma samples from patients with A) primary DF (n = 26), B) secondary DF (n = 144) and C) secondary DHF (n = 64). Data are median and IQR. *** P<0.001 ** 0.001<P<0.01 * 0.01<P<0.05 t 0.05<P<0.1. Data from patients with DENV-1 and -2 primary DHF (n = 3 and n = 1 respectively) and DENV-4 secondary DHF (n = 1) are not displayed because the number of these patients was too small for statistical analysis. The numbers below the graph indicate the numbers of patients at each time point. The dashed line represents the assay limit of detection.

Figure 2. Magnitude of DENV-1 viremia by illness day.

Levels of DENV-1 genome equivalent cDNA copies per millilitre were determined in serial plasma samples from DENV-1 infected patients with primary DF (n = 15), primary DHF (n = 3), secondary DF (n = 91) and secondary DHF (n = 33). Data are median and IQR. *** P<0.001 ** 0.001<P<0.01 * 0.01<P<0.05 t 0.05<P<0.1. The numbers below the graph indicate the numbers of patients at each time point (2 per patient for most of the time points). The dashed line represents the assay limit of detection.

Figure 3. Time to resolution of DENV viremia.

Kaplan-Meyer survival analysis of time to resolution of plasma viremia in all viremic A) or DENV-1 only B) patients.

Figure 4. Time to resolution of NS1 antigenemia.

Kaplan-Meyer survival analysis of time to resolution of NS1 antigenemia in all viremic A) or DENV-1 only B) patients. Two patients NS1 negative at enrolment were later positive and for the purposes of analysis were considered positive at the time of enrolment.

Figure 5. Fever clearance time.

Kaplan-Meyer survival analysis of fever clearance time in all viremic patients. Two patients afebrile at enrolment developed fever soon after and for the purposes of analysis were considered febrile at the time of enrolment.

Figure 6. Profile of haematological parameters and viremia in DENV-1 infected patients.

Medians of viremia levels, WBC and platelet counts, hemoconcentration, and percentages of lymphocytes and neutrophils were determined in serial plasma samples from DENV-1 infected patients with A) primary DF, B) secondary DF, C) primary DHF and D) secondary DHF. The numbers below the graph indicate the numbers of patients at each time point. For reasons of clarity, error bars are not shown.