Fue Vang

Human Rhinovirus Species and Season of Infection Determine Illness Severity

RATIONALE Human rhinoviruses (HRVs) consist of approximately 160 types that cause a wide range of clinical outcomes, including asymptomatic infections, common colds, and severe lower respiratory illnesses. OBJECTIVES To identify factors that influence the severity of HRV illnesses. METHODS HRV species and types were determined in 1,445 nasal lavages that were prospectively collected from 209 infants participating in a birth cohort who had at least one HRV infection. Questionnaires were used during each illness to identify moderate to severe illnesses (MSI). MEASUREMENTS AND MAIN RESULTS Altogether, 670 HRV infections were identified, and 519 of them were solitary infections (only one HRV type). These 519 viruses belonged to 93 different types of three species: 49 A, 9 B, and 35 C types. HRV-A (odds ratio, 8.2) and HRV-C (odds ratio, 7.6) were more likely to cause MSI compared with HRV-B. In addition, HRV infections were 5- to 10-fold more likely to cause MSI in the winter months (P < 0.0001) compared with summer, in contrast to peak seasonal prevalence in spring and fall. When significant differences in host susceptibility to MSI (P = 0.004) were considered, strain-specific rates of HRV MSI ranged from less than 1% to more than 20%. CONCLUSIONS Factors related to HRV species and type, season, and host susceptibility determine the risk of more severe HRV illness in infancy. These findings suggest that anti-HRV strategies should focus on HRV-A and -C species and identify the need for additional studies to determine mechanisms for seasonal increases of HRV severity, independent of viral prevalence, in cold weather months.

Improved Molecular Typing Assay for Rhinovirus Species A, B, and C

ABSTRACT Human rhinoviruses (RVs), comprising three species (A, B, and C) of the genus Enterovirus, are responsible for the majority of upper respiratory tract infections and are associated with severe lower respiratory tract illnesses such as pneumonia and asthma exacerbations. High genetic diversity and continuous identification of new types necessitate regular updating of the diagnostic assays for the accurate and comprehensive detection of circulating RVs. Methods for molecular typing based on phylogenetic comparisons of a variable fragment in the 5′ untranslated region were improved to increase assay sensitivity and to eliminate nonspecific amplification of human sequences, which are observed occasionally in clinical samples. A modified set of primers based on new sequence information and improved buffers and enzymes for seminested PCR assays provided higher specificity and sensitivity for virus detection. In addition, new diagnostic primers were designed for unequivocal species and type assignments for RV-C isolates, based on phylogenetic analysis of partial VP4/VP2 coding sequences. The improved assay was evaluated by typing RVs in >3,800 clinical samples. RVs were successfully detected and typed in 99% of the samples that were RV positive in multiplex diagnostic assays.

Molecular identification and quantification of human rhinoviruses in respiratory samples.

PCR-based molecular assays have become standard diagnostic procedures for the identification and quantification of human rhinoviruses (HRVs) and other respiratory pathogens in most, if not all, clinical microbiology laboratories. Molecular assays are significantly more sensitive than traditional culture-based and serological methods. This advantage has led to the recognition that HRV infections are common causes for not only upper airway symptoms but also more severe lower respiratory illnesses. In addition, molecular assays improve turnaround time, can be performed by technicians with ordinary skills, and can easily be automated. This chapter describes two highly sensitive and specific PCR-based methods for identifying and quantifying HRVs. The first is a two-step PCR method for the detection and typing of HRV. The second is a pan-HRV real-time quantitative (q) PCR method for measuring viral loads in respiratory samples.