Effects of Human Metapneumovirus and Respiratory Syncytial Virus Antigen Insertion in Two 3′ Proximal Genome Positions of Bovine/Human Parainfluenza Virus Type 3 on Virus Replication and Immunogenicity

Abstract

A live attenuated bovine parainfluenza virus type 3 (PIV3), harboring the fusion (F) and hemagglutininneuraminidase (HN) genes of human PIV3, was used as a virus vector to express surface glycoproteins derived from two human pathogens, human metapneumovirus (hMPV) and respiratory syncytial virus (RSV). RSV and hMPV are both paramyxoviruses that cause respiratory disease in young children, the elderly, and immunocompromised individuals. RSV has been known for decades to cause acute lower respiratory tract infections in young children, which often result in hospitalization, while hMPV has only been recently identified as a novel human respiratory pathogen. In this study, the ability of bovine/human PIV3 to express three different foreign transmembrane surface glycoproteins and to induce a protective immune response was evaluated. The RNAdependent RNA polymerase of paramyxoviruses binds to a single site at the 3 end of the viral RNA genome to initiate transcription of viral genes. The genome position of the viral gene determines its level of gene expression. The promoter-proximal gene is transcribed with the highest frequency, and each downstream gene is transcribed less often due to attenuation of transcription at each gene junction. This feature of paramyxoviruses was exploited using the PIV3 vector by inserting the foreign viral genes at the 3 terminus, at position 1 or 2, of the viral RNA genome. These locations were expected to yield high levels of foreign viral protein expression stimulating a protective immune response. The immunogenicity and protection results obtained with a hamster model showed that bovine/human PIV3 can be employed to generate bivalent PIV3/RSV or PIV3/hMPV vaccine candidates that will be further evaluated for safety and efficacy in primates.Despite control of many infectious diseases in the industrialized world, acute viral respiratory tract infections remain a leading cause of illness and reason for hospitalization. Two paramyxoviruses, respiratory syncytial virus (RSV) and human parainfluenza virus type 3 (hPIV3), are the causative agents of acute respiratory diseases of infancy and early childhood, resulting in 20 to 25% of pneumonia and 45 to 50% of bronchiolitis in hospitalized children (8). In addition, a recently identified human metapneumovirus (hMPV) appears to be associated with lower respiratory tract infections in children (25). Preliminary epidemiological reports have estimated an hMPV disease incidence rate of 7 to 10% in young children (5,11,16,18,25). The symptoms of hMPV infections are similar to those caused by RSV and hPIV3, and hospitalizations of young children with acute lower respiratory tract infections are necessary in some cases (17). Recently, Greensill et al. reported the detection of hMPV in bronchoalveolar lavage fluids from 21 of 30 infants (70%) ventilated for RSV bronchiolitis (7).RSV remains one of the most common respiratory pathogens afflicting infants, the elderly, and immunocompromised individuals. Hospitalization and immunoglobulin treatment are of...

A serum-free Vero production platform for a chimeric virus vaccine candidate

“…Construction of the MEDI-534 virus has been previously detailed (Tang et al 2003). To generate the virus seed stock used for infection in all experiments, MEDI-534 obtained by plasmid rescue (Tang et al 2003) was added at multiplicity of infection (MOI) of 0.001 to T-225 flask cultures of Vero cells that had grown for 3 days in OptiPRO SFM.…”

“…Next, they inserted the RSV F gene into the bovine/ human PIV3 vector backbone so that the resulting chimeric virus-named MEDI-534--expresses the RSV F protein (Tang et al 2003). MEDI-534 functioned as a live, attenuated, bivalent vaccine in animal studies: hamsters and non-human primates immunized with MEDI-534 produced both hPIV3 hemagglutination-inhibiting and RSV-neutralizing serum antibodies and these animals demonstrated protection from challenges with hPIV3 and RSV (Tang et al 2003(Tang et al , 2004.…”

“…In all instances, Vero cells-originating from a continuous African green monkey kidney cell line-generated the highest virus titers. Subsequent experiments showed that the MEDI-534 virus maintained the RSV F gene inserts stably for up to 10 serial passages in Vero cells (Tang et al 2003). In addition to its ability to support MEDI-534 propagation, the Vero cell line also presents other advantages.…”

“…Furthermore, regulatory authorities have provided guidelines on the use of Vero cells for viral vaccine production (WHO 1987a, b). Based on these advantages, MedImmune Vaccines selected the Vero cell line for propagating MEDI-534 (Tang et al 2003(Tang et al , 2004.…”

Respiratory syncytial virus (RSV) fusion protein expressed by recombinant Sendai virus elicits B-cell and T-cell responses in cotton rats and confers protection against RSV subtypes A and B

“…Thus far, there has been no indication of a clear clinical vaccine success, either because (i) safety problems have surfaced, (ii) the immunogenicity of vaccines has been inadequate, or (iii) the studies have not reached completion. The challenge that remains is to strike an effective balance between the safety and immunogenicity of current RSV candidate vaccines [19][20][21][22][23][24].…”