Structure-based design of a quadrivalent fusion glycoprotein vaccine for human parainfluenza virus types 1-4.

Parainfluenza virus types 1-4 (PIV1-4) are highly infectious human pathogens, of which PIV3 is most commonly responsible for severe respiratory illness in newborns, elderly, and immunocompromised individuals. To obtain a vaccine effective against all four PIV types, we engineered mutations in each of the four PIV fusion (F) glycoproteins to stabilize their metastable prefusion states, as such stabilization had previously enabled the elicitation of high-titer neutralizing antibodies against the related respiratory syncytial virus. A cryoelectron microscopy structure of an engineered PIV3 F prefusion-stabilized trimer, bound to the prefusion-specific antibody PIA174, revealed atomic-level details for how introduced mutations improved stability as well as how a single PIA174 antibody recognized the trimeric apex of prefusion PIV3 F. Nine combinations of six newly identified disulfides and two cavity-filling mutations stabilized the prefusion PIV3 F immunogens and induced 200- to 500-fold higher neutralizing titers in mice than were elicited by PIV3 F in the postfusion conformation. For PIV1, PIV2, and PIV4, we also obtained stabilized prefusion Fs, for which prefusion versus postfusion titers were 2- to 20-fold higher. Elicited murine responses were PIV type-specific, with little cross-neutralization of other PIVs. In nonhuman primates (NHPs), quadrivalent immunization with prefusion-stabilized Fs from PIV1-4 consistently induced potent neutralizing responses against all four PIVs. For PIV3, the average elicited NHP titer from the quadrivalent immunization was more than fivefold higher than any titer observed in a cohort of over 100 human adults, highlighting the ability of a prefusion-stabilized immunogen to elicit especially potent neutralization.

Synthesis of human parainfluenza virus 4 nucleocapsid-like particles in yeast and their use for detection of virus-specific antibodies in human serum.

The aim of this study was to produce human parainfluenza virus type 4 (HPIV4) nucleocapsid (N) protein in yeast Saccharomyces cerevisiae expression system, to explore its structural and antigenic properties and to evaluate its applicability in serology. The use of an optimized gene encoding HPIV4 N protein amino acid (aa) sequence GenBank AGU90031.1 allowed high yield of recombinant N protein forming nucleocapsid-like particles (NLPs) in yeast. A substitution L332D disrupted self-assembly of NLPs, confirming the role of this position in the N proteins of Paramyxovirinae. Three monoclonal antibodies (MAbs) were generated against the NLP-forming HPIV4 N protein. They recognised HPIV4-infected cells, demonstrating the antigenic similarity between the recombinant and virus-derived N proteins. HPIV4 N protein was used as a coating antigen in an indirect IgG ELISA with serum specimens of 154 patients with respiratory tract infection. The same serum specimens were tested with previously generated N protein of a closely related HPIV2, another representative of genus Rubulavirus. Competitive ELISA was developed using related yeast-produced viral antigens to deplete the cross-reactive serum antibodies. In the ELISA either without or with competition using heterologous HPIV (2 or 4) N or mumps virus N proteins, the seroprevalence of HPIV4 N-specific IgG was, respectively, 46.8, 39.6 and 40.3% and the seroprevalence of HPIV2 N-specific IgG-47.4, 39.0 and 37.7%. In conclusion, yeast-produced HPIV4 N protein shares structural and antigenic properties of the native virus nucleocapsids. Yeast-produced HPIV4 and HPIV2 NLPs are prospective tools in serology.

Local production of inflammatory mediators during childhood parainfluenza virus infection.

OBJECTIVE: To describe the clinical manifestations of parainfluenza virus (PIV) infection and to characterize biochemical markers of PIV disease severity. PATIENTS AND METHODS: We reviewed the medical records of 165 children who had a nasal wash culture positive for PIV at our institution between 1998 and 2008. Nasal wash samples were assayed for 26 inflammatory mediators using Luminex bead proteomics. RESULTS: A total of 153 patients, ages 2 weeks to 12 years, with single virus infection were included in our final analysis. Fifty-two patients were infected with PIV1, 19 with PIV2, 74 with PIV3, and 8 with PIV4. Lower respiratory tract infection (LRTI) was diagnosed in 67 (44%) patients, 21 (14%) had laryngotracheobronchitis, and 49 (32%) had an upper respiratory infection other than laryngotracheobronchitis. LRTI was diagnosed in 54% of patients infected with PIV3, 35% of those infected with PIV1, 26% of those with PIV2, and 50% of those with PIV4. Compared with uninfected control patients, PIV-infected patients had higher nasal wash concentrations of interleukin-6, CX-chemokine ligand 8 (CXCL8 or interleukin-8), CCL3 (macrophage inflammatory protein-1alpha), CCL4 (macrophage inflammatory protein-1beta), CXCL9 (monokine induced by interferon gamma), and CCL5 (regulated upon activation, normal T cell expressed and secreted (RANTES). Patients with LRTI, moderate or severe illness, and PIV 1 or 3 (respirovirus) infection had higher nasal wash concentrations of CXCL8 when compared with patients with upper respiratory infection, mild illness, or PIV 2 and 4 (rubulavirus) infection (P < 0.05). CONCLUSIONS: PIV infection causes a spectrum of illnesses associated with the expression and release of several proinflammatory mediators. Of note, elevated concentrations of CXCL8 in nasal wash samples are associated with more severe forms of PIV disease.

Current status of vaccines for parainfluenza virus infections.

Parainfluenza viruses (PIV) have been generally disregarded as pathogens in spite of their importance in pediatric lower respiratory illness. Because PIVs account for 17% of hospitalized illness associated virus isolation, the development of PIV vaccine would be a major advance in preventing lower respiratory tract infection in infants and young children. We will review in detail several PIV vaccine candidates and recent newer approaches to PIV vaccine development. Intranasally administered bovine PIV3 (bPIV3) vaccine and cold-adapted PIV3 vaccine have been evaluated throughout the pediatric age spectrum. BPIV3 does not give a robust response to the heterotypic human strain although seroconversion rate to bPIV3 is 57-65%. However, bPIV3 vaccine is being used as an attenuated backbone for insertion of human PIV3 hemagglutinin-neuraminidase and fusion (F) proteins and a surface protein, F, of respiratory syncytial virus. The effectiveness of this vaccine against both PIV3 and RSV challenge has been demonstrated in African green monkeys. The cold-adapted PIV3 vaccine has been extensively evaluated and is safe and immunogenic in seronegative children with a seroconversion rate of 79%. These promising candidates deserve to enter into efficacy trials both for their ability to prevent PIV3 disease and as a model of protection against respiratory illness by mucosal vaccination.