The impact of viral dynamics on the clinical severity of infants with respiratory syncytial virus bronchiolitis

Abstract

The impact of dynamic respiratory syncytial virus (RSV) load on the clinical severity of hospitalized infants with bronchiolitis has not been clarified. Nasopharyngeal aspirates were obtained from 60 infants who were diagnosed with bronchiolitis within 96 hr of wheezing onset upon admission and on days 3, 5, and 7 in the hospital, and 17 respiratory viruses were detected. The RSV load was quantified by real-time qPCR for RSV subtypes A and B at different time points. Scoring criteria were used to evaluate the degree of severity. A total of 40 infants were determined to be RSV-positive, nine were identified as RSV subtype A (RSVA), and 31 were RSV subtype B (RSVB). The peak RSV load was observed upon admission, and the RSV load decreased significantly over time; in addition, this decrease began to have significant differences on day 5. There was a positive correlation between the RSV load and the clinical score (r(2) = 0.121 and P < 0.001). According to the clinical scores, the infants in the severe group tended to have higher RSV loads than those in the moderate and mild groups. Multivariate logistic regression models revealed that the viral load on day 3 was independently associated with the degree of severity. This study elucidated that a higher mean RSV load was associated with a more severe disease and a longer duration of hospitalization and symptoms. This study also clarified RSV replication in infants and provides a theoretical basis for specifying an anti-RSV therapy strategy.

Genomic Loads and Genotypes of Respiratory Syncytial Virus: Viral Factors during Lower Respiratory Tract Infection in Chilean Hospitalized Infants

“…In our study, we confirmed that a greater number of RSV genomic copies are found when sampling occurs early during the LRTI, being significantly lower when the samples are collected later than 3 days of onset of cough, the symptom we chose as a marker of LRTI. In agreement with the studies by Zhou et al [41] and El Saleeby et al [30], we found higher viral loads in the infants with severe LRTI with more than 3 days of lower respiratory tract symptoms, but not in infants with severe LRTI at 3 days or less of illness, suggesting a difference in the kinetics of viral clearance. We postulate that a delayed viral clearance is contributing to greater airway injury and longer duration of severe LRTI.…”

“…Recent publications have described associations between RSV loads and severity scores [40,41], duration of hospitalization [30,31], and Intensive Care Unit requirements [30]. Moreover, analyzes considering the days of symptoms prior to sample collection have shown that viral clearance is an important factor to consider [30,41], since significant differences are detected in genomic loads and their predictive capacity of severity depending on the date of sampling.…”

“…Moreover, analyzes considering the days of symptoms prior to sample collection have shown that viral clearance is an important factor to consider [30,41], since significant differences are detected in genomic loads and their predictive capacity of severity depending on the date of sampling. In our study, we confirmed that a greater number of RSV genomic copies are found when sampling occurs early during the LRTI, being significantly lower when the samples are collected later than 3 days of onset of cough, the symptom we chose as a marker of LRTI.…”

Viral Load Dynamics and Clinical Disease Severity in Infants With Respiratory Syncytial Virus Infection

“…Information in regard to the dynamics of VL in infants with RSV infection is also limited, possibly due to the difficulty of performing daily sampling in these young children [10,26,27]. Two different studies of different sample sizes evaluated VL in children with RSV LRTI during the first 3 days of hospitalization or every other day during the first week of hospital stay.…”

Antibody response to respiratory syncytial virus infection in children <18 months old

“…Previous studies have evidenced a positive correlation between the RSV load, the duration of virus elimination, and the clinical course of the disease. [21][22][23] Another study highlighted the poor role of antibody concentration in conditioning the severity of RSV disease because it showed that children with high levels of maternally derived neutralizing antibodies, despite having a reduced risk of infection, have disease with the same severity of children with a low antibody concentration when RSV infection occurs. 4 In this study, it was expected that the lack of an association between viral factors and immune response and the severity of the disease does not influence immune response.…”