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Acridine dyes, including proflavine and acriflavine, were commonly used as antiseptics before the advent of penicillins in the mid-1940s. While their mode of action on pathogens was originally attributed to their DNA intercalating activity, work in the early 1970s suggested involvement of the host immune responses, characterized by induction of interferon (IFN)-like activities through an unknown mechanism. We demonstrate here that sub-toxic concentrations of a mixture of acriflavine and proflavine instigate a cyclic-GMP-AMP (cGAMP) synthase (cGAS)-dependent type-I IFN antiviral response. This pertains to the capacity of these compounds to induce low level DNA damage and cytoplasmic DNA leakage, resulting in cGAS-dependent cGAMP-like activity. Critically, acriflavine:proflavine pre-treatment of human primary bronchial epithelial cells significantly reduced rhinovirus infection. Collectively, our findings constitute the first evidence that non-toxic DNA binding agents have the capacity to act as indirect agonists of cGAS, to exert potent antiviral effects in mammalian cells., (© The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.)

Background: Rhinoviruses frequently cause the common cold but have not been considered important causes of acute respiratory hospitalizations in children., Methods: A population-based surveillance study was performed among children <5 years of age who were hospitalized with respiratory symptoms or fever and who resided within counties encompassing Nashville, Tennessee, or Rochester, New York, from October 2000 through September 2001. Data collected included questionnaires, nasal and throat swabs for viral culture and polymerase chain reaction testing, and chart review. Rates of rhinovirus-associated hospitalizations were calculated., Results: Of 592 children enrolled, 156 (26%) were rhinovirus positive, representing 4.8 (95% confidence interval [CI], 4.3-5.2) rhinovirus-associated hospitalizations/1000 children. Age-specific rates per 1000 children were 17.6 (95% CI, 14.9-20.6) for 0-5-month-olds, 6.0 (95% CI, 5.0-7.0) for 6-23-month-olds, and 2.0 (95% CI, 1.6, 2.4) for 24-59-month-olds (P<.01). Children with a history of wheezing/asthma had significantly more rhinovirus-associated hospitalizations than those without a history (25.3/1000 children [95% CI, 21.6-29.5/1000 children] vs. 3.1/1000 children [95% CI, 2.7-3.5/1000 children])., Conclusions: Rhinoviruses were associated with nearly 5 hospitalizations/1000 children <5 years of age and were highest in children with a history of wheezing/asthma.

Rhinovirus (RV) infections can alter lower airway physiology and inflammation, yet the characteristics of RV replication in lower airway cells are incompletely understood. An RV serotype 16 (RV16)-specific monoclonal antibody was identified. Immunohistochemistry and an infectious center assay were used to quantitate the infectivity of RV16 in primary bronchial and adenoidal epithelial cells. The proportion of infectible epithelial cells increased with the inoculum but did not exceed 10%. Analysis of bronchial tissue samples infected ex vivo demonstrated a small subset of RV-infected cells in the epithelial layer. These data confirm previous reports that RV infects only a small subset of epithelial cells in upper airway tissues and indicate that lower airway epithelial cells have a similar susceptibility to RV infection. In confirming that RV can infect cells in the lower airway, these results suggest that lower airway dysfunction occurs through this mechanism in susceptible persons.

Rhinoviruses are important upper respiratory pathogens that are strongly associated with asthma exacerbations. However, the inflammatory response to rhinovirus infection is poorly understood. Interleukin (IL)-8 has been implicated in the pathogenesis of respiratory viral infections and asthma. Rhinovirus-induced IL-8 release and mRNA induction were examined in peripheral blood mononuclear cells (PBMC). Rhinoviruses induced IL-8 release for up to 7 days after inoculation onto PBMC. This was associated with an increase in IL-8 mRNA expression that peaked 48 h after exposure to the virus. IL-8 protein production was reduced by UV inactivation of the virus and abolished by preventing virus-receptor binding. Although rhinovirus replication was not demonstrated in PBMC, low-grade productive infection was shown in the human monocyte cell line THP-1. Rhinovirus induction of IL-8 in monocytes or airway macrophages may be important in the pathogenesis of rhinovirus-induced asthma exacerbation.

Eleven young adults with experimental rhinovirus infection (cases) and six noninfected saline-challenged young adults (controls) underwent nasal washings and symptom evaluations at 2-hour intervals for 24 hours after intranasal challenge. The mean and median periods to the first recovery of virus were 11.3 hours and 10 hours, respectively. Geometric mean rhinovirus titers in cases reached 10(0.2) log10 TCID50 (50% tissue culture infective dose)/0.1 mL at 10 hours and rose to 10(1.0) log10 TCID50/0.1 mL at 18 hours. Nine (82%) of 11 cases and one (16.7%) of six controls had colds. Mean total symptom scores for cases became significantly higher than those for controls at 16 hours. Sore or scratchy throat appeared between 10 and 12 hours in cases, but nasal obstruction and rhinorrhea first appeared at 2 hours, thus suggesting some nasal irritation from the viral inoculum pool. The incubation period of experimental rhinovirus infection is similar to that in cell culture. Nasal and pharyngeal symptoms began early in infection.

Dichloroflavan was found to stabilize rhinovirus 1B to inactivation by heat at 56 degrees C or by acid at pH 4.6 to 5.0. The effects of dichloroflavan, arildone and sodium dodecyl sulphate on uncoating of virus in M.HeLa cells were compared by examining the production of sub-viral particles separated on sucrose density gradients; the development of photoresistance by neutral red labelled virus. All three compounds significantly reduced but did not completely suppress the production of sub-viral particles. They also affected the uncoating of neutral red labelled virus, although dichloroflavan appeared to delay rather than prevent this process. A variant of rhinovirus 1B, isolated by growth in the presence of dichloroflavan, showed increased resistance to inhibition by arildone and SDS as well as dichloroflavan, suggesting a similar site of action for the three compounds.

The compound 2-amino-1-(isopropyl sulfonyl)-6-benzimidazole phenyl ketone oxime (LY122771-72) at a concentration of 0.2 microgram/ml completely inhibited rhinovirus replication in human embryonic nasal organ cultures, although in the absence of virus the compound did not inhibit ciliary activity when used at a concentration of 25 micrograms/ml. When added 26 hr after infection, the compound stopped rhinovirus production in organ cultures that had already started to release virus. Five rhinovirus types available for infection of volunteers and six recently obtained clinical isolates were shown to be more sensitive to LY122771-72 in tissue culture than the rhinovirus type 31 used in the organ culture experiments. These results suggest that this potential antiviral drgu should be evaluated in humans.

The prophylactic effect of low doses of human leukocyte interferon (HuIFN-alpha) against infection with rhinovirus was measured in double-blind, placebo-controlled studies with volunteer subjects. An antihistamine (chlorpheniramine) was given before administration of single or multiple doses of HuIFN-alpha but saturated cotton pledget or by aerosol; volunteers were then challenged with rhinovirus. When the results for all groups were combined, a lower frequency of respiratory illness was demonstrated in the HuIFN-alpha-treated volunteers (20 of 39 vs. 11 of 38, P less than 0.05). A significant improvement in mean symptom scores was found only in the volunteers who received HuIFN-alpha by cotton pledget. The total numbers of isolates of rhinovirus and seroconversions were similar for HuIFN-alpha-treated and control volunteers. No significant side effects were noted in the HuIFN-alpha-treated volunteers. Higher concentrations or improved methods of delivery of HuIFN-alpha will be necessary for improving the clinical efficacy of HuIFN-alpha against viral infections in the respiratory system.

Communicability of rhinovirus type 16 or type 55 was studied in 24 childless couples; on partner (the donor) was infected with laboratory-grown virus. Initially, both partners lacked antibody to the challenge agent. Rates of transmission between partners were 41% and 33% for type 16 and type 55, respectively. These rates are similar to those determined in epidemiologic studies of natural rhinovirus infection. Although the mucosa of the anterior nares was shown to be highly susceptible to infection (less than one 50% tissue culture infective dose [TCID50]), transmission rarely occurred unless (1) at least 1,000 TCID50 of virus was recovered from the donor's nasal washing, (2) the donor had virus on his hands and anterior nares, (3) he was at least moderately symptomatic, and (4) he spent many hours with his spouse. Since person-to-person transfer of rhinovirus was so dependent upon time spent together and shedding of large amounts of virus by the donor, it seems possible that the chain of infection could be interrupted by environmental manipulation.