Members of rhinovirus C (RV-C) species are more likely to cause wheezing illnesses and asthma exacerbations compared with other rhinoviruses. The cellular receptor for these viruses was heretofore unknown. We report here that expression of human cadherin-related family member 3 (CDHR3) enables the cells normally unsusceptible to RV-C infection to support both virus binding and replication. A coding single nucleotide polymorphism (rs6967330, C529Y) was previously linked to greater cell-surface expression of CDHR3 protein, and an increased risk of wheezing illnesses and hospitalizations for childhood asthma. Compared with wild-type CDHR3, cells transfected with the CDHR3-Y529 variant had about 10-fold increases in RV-C binding and progeny yields. We developed a transduced HeLa cell line (HeLa-E8) stably expressing CDHR3-Y529 that supports RV-C propagation in vitro. Modeling of CDHR3 structure identified potential binding sites that could impact the virus surface in regions that are highly conserved among all RV-C types. Our findings identify that the asthma susceptibility gene product CDHR3 mediates RV-C entry into host cells, and suggest that rs6967330 mutation could be a risk factor for RV-C wheezing illnesses.

Background Epidemiological studies provide evidence of differential virulence of rhinovirus (RV) species. We recently reported that RV-A and RV-C induced more severe illnesses than RV-B, suggesting that the biology of RV-B might be different from RV-A or RV-C. Objective To test the hypothesis that RV-B has lower replication and induces lesser cytokine responses than RV-A or RV-C. Methods We cloned full-length cDNA of RV-A16, A36, B52, B72, C2, C15 and C41 from clinical samples, and grew clinical isolates of RV-A7 and B6 in cultured cells. Sinus epithelial cells were differentiated at air-liquid interface. We tested for differences in viral replication in epithelial cells after infection with purified viruses (108 RNA copies) and measured virus load by quantitative RT-PCR. We measured lactate dehydrogenase (LDH) concentration as a marker of cellular cytotoxicity, and cytokine/chemokine secretion by multiplex ELISA. Results At 24 hours post infection, virus load of RV-B (RV-B52, B72, or B6) in adherent cells was lower than that of RV-A or RV-C. The growth kinetics of infection indicated that RV-B types replicate more slowly. Furthermore, RV-B released less LDH than RV-A or RV-C, and induced lower levels of cytokines and chemokines such as CXCL10, even after correction for viral replication. RV-B replicates to lower levels also in primary bronchial epithelial cells. Conclusions Our results indicate that RV-B types have lower and slower replication, and lower cellular cytotoxicity and cytokine/chemokine production compared to RV-A or RV-C. These characteristics may contribute to reduced severity of illnesses that has been observed with RV-B infections. Clinical implications RV-B types replicate at a lower rate and produce less cytokine/chemokine compared to RV-A or RV-C, which may contribute to the clinical observation that RV-B causes less severe illnesses. Capsule summary RV-B types replicate more slowly and to lower levels, and less cytokine/chemokine production compared to RV-A or RV-C. These characteristics may contribute to reduced severity of illnesses that has been observed with RV-B infections.

Information about the basic biological properties of Human rhinovirus C (HRV-C) viruses is lacking due to difficulties with culturing these viruses. Our objective was to develop a cell culture system to grow HRV-C. Epithelial cells from human sinuses (HSEC) were differentiated at air-liquid interface (ALI). Differentiated cultures supported 1-2 logs growth of HRV-C15 as detected by quantitative RT-PCR. Two distinguishing features of HRVs are acid lability and optimal growth at 33–34°C. We used this system to show that HRV-C15 is neutralized by low pH (4.5). In contrast to most HRV types, replication of HRV-C15 and HRV-C41 was similar at 34 and 37°C. The HSEC ALI provides a useful tool for quantitative studies of HRV-C replication. The ability of HRV-C to grow equally well at 34°C and 37°C may contribute to the propensity for HRV-C to cause lower airway illnesses in infants and children with asthma.

Orally administered recombinant attenuated Salmonella vaccines (RASV) elicit humoral and mucosal immune responses against the immunizing antigen. The challenge in developing an effective vaccine against a virus or an intracellular bacterium delivered by RASVs is to introduce the protective antigen inside the host cell cytoplasm for presentation to MHC-I molecules for an efficient cell mediated immune response. To target the influenza nucleoprotein (NP) into the host cell cytosol, we constructed a regulated delayed lysis in vivo RASV strain χ11246(pYA4858) encoding influenza NP with a chromosomal deletion of the sifA gene to enable it to escape from the endosome prior to lysis. Oral immunization of mice with χ11246(pYA4858) (SifA−) with 3 booster immunizations resulted in complete protection (100%) against a lethal influenza virus (rWSN) challenge (100 LD50) compared to 25% survival of mice immunized with the isogenic χ11017(pYA4858) (SifA+) strain. Reducing the number of booster immunizations with χ11246(pYA4858) from 3 to 2 resulted in 66% survival of mice challenged with rWSN (100 LD50). Immunization with χ11246(pYA4858) via different routes provided protection in 80% orally, 100% intranasally and 100% intraperitoneally immunized mice against rWSN (100 LD50). A Th1 type immune response was elicited against influenza NP in all experiments. IFN-γ secreting NP147–155 specific T cells were not found to be correlated with protection. The role of antigen-specific CD8+ T cells remains to be determined. To conclude, we showed that Salmonella can be designed to deliver antigen(s) to the host cell cytosol for presumably class I presentation for the induction of protective immune responses.

Influenza virus has a set of ribonucleoproteins (RNPs) consisting of viral RNAs, influenza virus polymerase subunits, and nucleoprotein. Intracellular reconstitution of the whole set of RNPs via plasmid transfection results in the generation of influenza virus. By the use of reverse genetics and dual promoters, we constructed a 23.6-kb eight-unit plasmid that contains all the required constituents to generate influenza virus in chicken cells. Our "one-plasmid" system generated higher titers of influenza virus in chicken cells than the "eight-plasmid" system, enabling a simpler approach for generating vaccine seeds. Our study identified plasmid size as a potential limiting factor affecting transfection efficiency and hence the influenza viral yield from chicken cells.