Molecular cloning and expression of human parainfluenza virus type 1 L gene

Immunogenicity and Therapeutic Efficacy of a Sendai-Virus-Vectored HSV-2 Vaccine in Mouse and Guinea Pig Models

BACKGROUND

To date, there is no licensed vaccine for preventing herpes simplex virus type 2 (HSV-2). The current treatment to address the infection and prevent its transmission is not always satisfactory.

METHODS

We constructed two recombinant vectors, one encoding HSV-2 glycoprotein D (gD, SeV-dF/HSV-2-gD) and one encoding HSV-2-infected cell protein 27 (ICP27, SeV-dF/HSV-2-ICP27), based on a replication-defective Sendai virus through reverse genetics, collectively comprising a combinatorial HSV-2 therapeutic vaccine candidate. The immunogenicity and proper immunization procedure for this vaccine were explored in a murine model. The therapeutic effect that helps prevent recurrent HSV-2 disease was evaluated in HSV-2-infected guinea pigs.

RESULTS

Both a robust humoral immune response and a cellular immune response, characterized by the neutralizing antibody titer and the IFN-γ level, respectively, were elicited in BALB/c mice. A further study of cellular immunogenicity in mice revealed that T lymphocytes were successfully enhanced with the desirable secretion of several cytokines. In HSV-2-seropositive guinea pigs, vaccination could reduce the severity of HSV-2 in terms of recurrent lesions, duration of recurrent outbreak, and frequency of recurrence by 58.66%, 45.34%, and 45.09%, respectively, while viral shedding was also significantly inhibited in the vaccine-treated group compared to the group treated with phosphate-buffered saline.

CONCLUSIONS

The replication-defective recombinant Sendai viruses conveying HSV-2-gD and ICP27 proteins showed great immunogenicity and potential for preventing recurrent HSV-2 disease.

Distinct Chronic Post-Viral Lung Diseases upon Infection with Influenza or Parainfluenza Viruses Differentially Impact Superinfection Outcome

Chronic obstructive pulmonary disease (COPD) and asthma remain prevalent human lung diseases. Variability in epithelial and inflammatory components that results in pathologic heterogeneity complicates the development of treatments for these diseases. Early childhood infection with parainfluenza virus or respiratory syncytial virus is strongly associated with the development of asthma and COPD later in life, and exacerbations of these diseases correlate with the presence of viral RNA in the lung. Well-characterized animal models of postviral chronic lung diseases are necessary to study the underlying mechanisms of viral-related COPD and asthma and to develop appropriate therapies. In this study, we cross-analyzed chronic lung disease caused by infection with Sendai virus (SeV) or influenza A virus in mice. Differences were observed in lesion composition and inflammatory profiles between SeV- and influenza A virus-induced long-term lung disease. In addition, a primary SeV infection led to worsened pathologic findings on secondary heterologous viral challenge, whereas the reversed infection scheme protected against disease in response to a secondary viral challenge >1 month after the primary infection. These data demonstrate the differential effect of primary viral infections in the susceptibility to disease exacerbation in response to a different secondary viral infection and highlight the usefulness of these viral models as tools to understand the underlying mechanisms that mediate distinct chronic postviral lung diseases.

Emerging gene therapies for cystic fibrosis

Introduction: Cystic fibrosis (CF) remains a life-threatening genetic disease, with few clinically effective treatment options. Gene therapy and gene editing strategies offer the potential for a one-time CF cure, irrespective of the CFTR mutation class. Areas covered: We review emerging gene therapies and gene delivery strategies for the treatment of CF particularly viral and non-viral approaches with potential to treat CF. Expert opinion: It was initially anticipated that the challenge of developing a gene therapy for CF lung disease would be met relatively easily. Following early proof-of-concept clinical studies, CF gene therapy has entered a new era with innovative vector designs, approaches to subvert the humoral immune system and increase gene delivery and gene correction efficiencies. Developments include integrating adenoviral vectors, rapamycin-loaded nanoparticles, and lung-tropic lentiviral vectors. The characterization of novel cell types in the lung epithelium, including pulmonary ionocytes, may also encourage cell type-specific targeting for CF correction. We anticipate preclinical studies to further validate these strategies, which should pave the way for clinical trials. We also expect gene editing efficiencies to improve to clinically translatable levels, given advancements in viral and non-viral vectors. Overall, gene delivery technologies look more convincing in producing an effective CF gene therapy.

Rescue of Sendai Virus from Cloned cDNA

Sendai virus (SeV) is a non-segment negative-sense RNA virus that naturally infects and causes pneumonia in mice. As a prototypic member of the family Paramyxoviridae, SeV has been characterized well, and these studies revealed numerous traits of paramyxovirus biology. The reverse genetics system to rescue SeV was first established in 1995. The virus was rescued from a cloned cDNA that contains full genome sequence flanked by T7 promoter and hepatitis delta virus ribozyme. To rescue SeV, it is necessary to infect cells with a recombinant vaccinia virus vTF7.3 that expresses T7 RNA polymerase, and transfect with the SeV full genome cDNAs together with supporting plasmids encoding NP, P, and L genes under the T7 promoter. Synthesized viral RNA by T7 RNA polymerase will be encapsidated with NP and associated with a polymerase complex composed of P and L. The polymerase complex transcribes and replicates the genome, and produces progeny virions. Rescued SeV needs to be plaque purified to exclude vTF7.3 from viral stock. Reverse genetics system of SeV is relatively efficient compared to other paramyxoviruses, but alternative approaches to rescue poorly growing mutant viruses are also available.

First-in-Human Evaluation of the Safety and Immunogenicity of an Intranasally Administered Replication-Competent Sendai Virus-Vectored HIV Type 1 Gag Vaccine: Induction of Potent T-Cell or Antibody Responses in Prime-Boost Regimens

Background. We report the first-in-human safety and immunogenicity assessment of a prototype intranasally administered, replication-competent Sendai virus (SeV)–vectored, human immunodeficiency virus type 1 (HIV-1) vaccine.

Methods. Sixty-five HIV-1–uninfected adults in Kenya, Rwanda, and the United Kingdom were assigned to receive 1 of 4 prime-boost regimens (administered at 0 and 4 months, respectively; ratio of vaccine to placebo recipients, 12:4): priming with a lower-dose SeV-Gag given intranasally, followed by boosting with an adenovirus 35–vectored vaccine encoding HIV-1 Gag, reverse transcriptase, integrase, and Nef (Ad35-GRIN) given intramuscularly (S_LA); priming with a higher-dose SeV-Gag given intranasally, followed by boosting with Ad35-GRIN given intramuscularly (S_HA); priming with Ad35-GRIN given intramuscularly, followed by boosting with a higher-dose SeV-Gag given intranasally (AS_H); and priming and boosting with a higher-dose SeV-Gag given intranasally (S_HS_H).

Results. All vaccine regimens were well tolerated. Gag-specific IFN-γ enzyme-linked immunospot–determined response rates and geometric mean responses were higher (96% and 248 spot-forming units, respectively) in groups primed with SeV-Gag and boosted with Ad35-GRIN (S_LA and S_HA) than those after a single dose of Ad35-GRIN (56% and 54 spot-forming units, respectively) or SeV-Gag (55% and 59 spot-forming units, respectively); responses persisted for ≥8 months after completion of the prime-boost regimen. Functional CD8⁺ T-cell responses with greater breadth, magnitude, and frequency in a viral inhibition assay were also seen in the S_LA and S_HA groups after Ad35-GRIN boost, compared with those who received either vaccine alone. SeV-Gag did not boost T-cell counts in the AS_H group. In contrast, the highest Gag-specific antibody titers were seen in the AS_H group. Mucosal antibody responses were sporadic.

Conclusions. SeV-Gag primed functional, durable HIV-specific T-cell responses and boosted antibody responses. The prime-boost sequence appears to determine which arm of the immune response is stimulated.

Clinical Trials Registration. NCT01705990.

Critical role of Rab11a-mediated recycling endosomes in the assembly of type I parainfluenza viruses

Paramyxoviruses replicate in the cytoplasm of infected cells and newly synthesized viral nucleocapsids (vRNPs) are transported to the plasma membrane to be incorporated into progeny virions. In this study, we analyzed the impact of the Rab11-mediated recycling pathway in Sendai virus (SeV) and human parainfluenza virus type 1 (hPIV1) vRNP transport. We found that suppression of Rab11 expression caused vRNP aggregation in the cytoplasm and reduced progeny virion formation. Overexpression of constitutively active Rab11Q70L, but not dominant negative Rab11S25N co-localized with vRNP, showing that vRNP specifically recognizes the GTP-bound active form of Rab11. Moreover, Rab11Q70L co-localized with the dominant negative tails of all three subtypes of myosins, Va, Vb, and Vc, while SeV and hPIV1 vRNPs co-localized with only myosin Vb and Vc. These results highlight the critical role of Rab11 in vRNP trafficking, and suggest a specificity in the recycling endosomes parainfluenza viruses utilize for virus assembly.

Independent structural domains in paramyxovirus polymerase protein

All enzymatic activities required for genomic replication and transcription of nonsegmented negative strand RNA viruses (or Mononegavirales) are believed to be concentrated in the viral polymerase (L) protein. However, our insight into the organization of these different enzymatic activities into a bioactive tertiary structure remains rudimentary. Fragments of Mononegavirales polymerases analyzed to date cannot restore bioactivity through trans-complementation, unlike the related L proteins of segmented NSVs. We investigated the domain organization of phylogenetically diverse Paramyxovirus L proteins derived from measles virus (MeV), Nipah virus (NiV), and respiratory syncytial virus (RSV). Through a comprehensive in silico and experimental analysis of domain intersections, we defined MeV L position 615 as an interdomain candidate in addition to the previously reported residue 1708. Only position 1708 of MeV and the homologous positions in NiV and RSV L also tolerated the insertion of epitope tags. Splitting of MeV L at residue 1708 created fragments that were unable to physically interact and trans-complement, but strikingly, these activities were reconstituted by the addition of dimerization tags to the fragments. Equivalently split fragments of NiV, RSV, and MeV L oligomerized with comparable efficiency in all homo- and heterotypic combinations, but only the homotypic pairs were able to trans-complement. These results demonstrate that synthesis as a single polypeptide is not required for the Mononegavirales polymerases to adopt a proper tertiary conformation. Paramyxovirus polymerases are composed of at least two truly independent folding domains that lack a traditional interface but require molecular compatibility for bioactivity. The functional probing of the L domain architecture through trans-complementation is anticipated to be applicable to all Mononegavirales polymerases.

Intranasal Sendai viral vector vaccination is more immunogenic than intramuscular under pre-existing anti-vector antibodies

Viral vectors are promising vaccine tools for eliciting potent cellular immune responses. Pre-existing anti-vector antibodies, however, can be an obstacle to their clinical use in humans. We previously developed a Sendai virus (SeV) vector vaccine and showed the potential of this vector for efficient CD8(+) T-cell induction in macaques. Here, we investigated the immunogenicity of SeV vector vaccination in the presence of anti-SeV antibodies. We compared antigen-specific CD8(+) T-cell responses after intranasal or intramuscular immunization with a lower dose (one-tenth of that in our previous studies) of SeV vector expressing simian immunodeficiency virus Gag antigen (SeV-Gag) between naive and pre-SeV-infected cynomolgus macaques. Intranasal SeV-Gag immunization efficiently elicited Gag-specific CD8(+) T-cell responses not only in naive but also in pre-SeV-infected animals. In contrast, intramuscular SeV-Gag immunization induced Gag-specific CD8(+) T-cell responses efficiently in naive but not in pre-SeV-infected animals. These results indicate that both intranasal and intramuscular SeV administrations are equivalently immunogenic in the absence of anti-SeV antibodies, whereas intranasal SeV vaccination is more immunogenic than intramuscular in the presence of anti-SeV antibodies. It is inferred from a recent report investigating the prevalence of anti-SeV antibodies in humans that SeV-specific neutralizing titers in more than 70% of people are no more than those at the SeV-Gag vaccination in pre-SeV-infected macaques in the present study. Taken together, this study implies the potential of intranasal SeV vector vaccination to induce CD8(+) T-cell responses even in humans, suggesting a rationale for proceeding to a vaccine clinical trial using this vector.

Host specificity of the anti-interferon and anti-apoptosis activities of parainfluenza virus P/C gene products

Human parainfluenza virus type 1 (HPIV-1) and Sendai virus (SeV) are highly homologous in structure and sequence, whilst maintaining distinct host ranges. These viruses express accessory proteins from their P/C gene that are known to have activities against innate immunity. The accessory proteins expressed from the P/C gene of these viruses are different. In addition to the nested set of C proteins, SeV expresses V protein from edited P mRNA, which is not expressed by HPIV-1. This study evaluated the host specificity and role of the P/C gene products in anti-interferon (IFN) and anti-apoptosis activity by characterizing a recombinant SeV, rSeVhP, in which the SeV P/C gene was replaced with that of HPIV-1. Unlike SeV, rSeVhP infection strongly activated IFN regulatory transcription factor (IRF)-3 and nuclear factor-kappaB, resulting in an increased level of IFN-beta induction compared with SeV in murine cells. In contrast, activation of IRF-3 was not observed in rSeVhP-infected human A549 cells. rSeVhPSV, which expressed SeV V protein from an inserted gene in rSeVhP, induced less IFN-beta than rSeVhP, suggesting that V contributes to the suppression of IFN production in murine cells. Furthermore, rSeVhP induced apoptotic cell death in murine but not in A549 cells. These data indicate the functional difference in P/C gene products from SeV and HPIV-1 in antagonizing IFN induction and apoptosis, which is likely to be one of the major factors for pathogenicity in specific hosts.

Human parainfluenza virus type 1 but not Sendai virus replicates in human respiratory cells despite IFN treatment

Sendai virus (SeV) and human parainfluenza virus type I (hPIV1) are highly homologous but have distinct host ranges, murine versus human. To identify the factors that affect the host specificity of parainfluenza viruses, we determined the infectivity and anti-IFN activities of SeV and hPIV1 in human and murine culture cells. SeV infected normal human lung MRC-5 and murine lung MM14.Lu or MLg2908 cells efficiently. Infection with SeV induced the release of IFN-beta into culture medium in MRC-5 cells at similar levels with that of cells infected with hPIV1. SeV or hPIV1 infections, as well as expression of SeV or hPIV1 C proteins, inhibited the nuclear localization of STAT1 induced by IFN-beta, suggesting that both SeV and hPIV1 C proteins block the IFN Jak/STAT pathway in MRC-5 cells. Pretreatment of MRC-5 cells with IFN suppressed replication of SeV and hPIV1 at an early stage of infection. However, hPIV1 overcame this suppression while SeV did not. SeV replication was restored in IFN-beta pretreated murine MM14.Lu cells, suggesting SeV anti-IFN activity is species specific. These results suggest that SeV is less effective than hPIV1 in overcoming antiviral activity in human cells, which could be one of the factors that restrict the host range of SeV.

Recombinant Sendai virus as a novel vaccine candidate for respiratory syncytial virus

Respiratory syncytial virus (RSV) is among the most important and serious pediatric respiratory diseases, and yet after more than four decades of research an effective vaccine is still unavailable. This review examines the role of the immune response in reducing disease severity; considers the history of RSV vaccine development; and advocates the potential utility of Sendai virus (a murine paramyxovirus) as a xenogenic vaccine vector for the delivery of RSV antigens. The immunogenicity and protective efficacy of RSV-recombinant Sendai virus vectors constructed using reverse genetics is examined. RSV-recombinant Sendai virus is easy to grow (i.e., achieves extremely high titers in eggs), is easy to administer (intranasal drops), and elicits both B- and T-cell responses leading to protection from RSV challenge in a small-animal model. Unmodified Sendai virus is currently being studied in clinical trials as a vaccine for its closely related human cognate (human parainfluenza virus type 1). Sendai virus may prove an enormously valuable vaccine platform, permitting the delivery of recombinants targeting important pediatric respiratory pathogens, RSV chief among them.

Recombinant Sendai virus expressing the G glycoprotein of respiratory syncytial virus (RSV) elicits immune protection against RSV

Although RSV causes serious pediatric respiratory disease, an effective vaccine does not exist. To capture the strengths of a live virus vaccine, we have used the murine parainfluenza virus type 1 (Sendai virus [SV]) as a xenogeneic vector to deliver the G glycoprotein of RSV. It was previously shown (J. L. Hurwitz, K. F. Soike, M. Y. Sangster, A. Portner, R. E. Sealy, D. H. Dawson, and C. Coleclough, Vaccine 15:533-540, 1997) that intranasal SV protected African green monkeys from challenge with the related human parainfluenza virus type 1 (hPIV1), and SV has advanced to clinical trials as a vaccine for hPIV1 (K. S. Slobod, J. L. Shenep, J. Lujan-Zilbermann, K. Allison, B. Brown, R. A. Scroggs, A. Portner, C. Coleclough, and J. L. Hurwitz, Vaccine, in press). Recombinant SV expressing RSV G glycoprotein was prepared by using reverse genetics, and intranasal inoculation of cotton rats elicited RSV-specific antibody and elicited protection from RSV challenge. RSV G-recombinant SV is thus a promising live virus vaccine candidate for RSV.

Sequence analysis of the Washington/1964 strain of human parainfluenza virus type 1 (HPIV1) and recovery and characterization of wild-type recombinant HPIV1 produced by reverse genetics

A complete consensus sequence was determined for the genomic RNA of human parainfluenza virus type 1 (HPIV1) strain Washington/20993/1964 (HPIV1 WASH/64), a clinical isolate that previously was shown to be virulent in adults. The sequence exhibited a high degree of relatedness to both Sendai virus, a PIV1 virus recovered from mice, and human PIV3 (HPIV3) with regard to cis-acting regulatory regions and protein-coding sequences. This consensus sequence was used to generate a full-length antigenomic cDNA and to recover a recombinant wild-type HPIV1 (rHPIV1). Interestingly, the rHPIV1 could be rescued from full-length antigenomic rHPIV1 cDNA using HPIV3 support plasmids, HPIV1 support plasmids, or a mixture thereof. The replication of rHPIV1 in vitro and in the respiratory tract of hamsters was similar to that of its biologically derived parent virus. The similar biological properties of rHPIV1 and HPIV1 WASH/64 in vitro and in vivo, together with the previous demonstration of the virulence of this specific isolate in humans, authenticates the rHPIV1 sequence as that of a wild-type virus. This rHPIV1 can now be used to study the biological properties of HPIV1 and as a substrate to introduce attenuating mutations for the generation of live-attenuated HPIV1 vaccine candidates.

The long noncoding region of the human parainfluenza virus type 1 f gene contributes to the read-through transcription at the m-f gene junction

Sendai virus (SV) and human parainfluenza virus type 1 (hPIV1) have genomes consisting of nonsegmented negative-sense RNA in which the six genes are separated by well-conserved intergenic (IG) sequences and transcriptional start (S) and end signals. In hPIV1-infected cells, transcriptional termination at the M-F gene junction is ineffective; a large number of M-F read-through transcripts are produced (T. Bousse, T. Takimoto, K. G. Murti, and A. Portner, Virology 232:44-52, 1997). In contrast, few M-F read-through transcripts are detected in SV-infected cells. Sequence analysis indicated that the hPIV1 IG and S sequences in the M-F junction differ from those of SV. Furthermore, the hPIV1 F gene contains an unusually long noncoding sequence. To identify the cis-acting elements that prevent transcriptional termination at the M-F junction, we rescued recombinant SV (rSVhMFjCG) in which its M-F gene junction was replaced by that of hPIV1. Cells infected with rSVhMFjCG produced an abundance of M-F read-through transcripts; this result indicated that the hPIV1 M-F junction is responsible for inefficient termination. When one or both of the IG and S sites in rSVhMFjCG were replaced by those of SV, the efficiency of transcriptional termination increased but not to the level observed in wild-type SV-infected cells. Deletion of most of the long noncoding region of the hPIV1 F gene in rSVhMFjCG in addition to the mutations in IG and S signals resulted in efficient termination that was equivalent to the level observed in wild-type virus-infected cells. Therefore, the long noncoding sequence of the hPIV1 F gene contains cis-acting element(s) that affects transcriptional termination. Our evaluation of the effect of inefficient transcriptional termination on viral replication in culture revealed that cells infected with rSVhMFjCG produced less F protein than cells infected with wild-type SV and that assembly of the recombinant SV in culture was less efficient. These phenotypes seem to be responsible for the extended survival of mice infected with rSVhMFjCG.

Two regions of the P protein are required to be active with the L protein for human parainfluenza virus type 1 RNA polymerase activity

The paramyxovirus P protein is an essential component of the viral RNA polymerase composed of P and L proteins. In this study, we characterized the physical and functional interactions between P and L proteins using human parainfluenza virus type 1 (hPIV1) and its counterpart Sendai virus (SV). The hPIV1 P and SV L proteins or the SV P and hPIV1 L proteins formed complexes detected by anti-P antibodies. Functional analysis using the minigenome SV RNA containing CAT gene indicated that the hPIV1 P--SV L complex, but not the SV P--hPIV1 L complex, was biologically active. Mutant SV P or hPIV1 P cDNAs, which do not express C proteins, showed the same phenotype with wild-type P cDNAs, indicating that C proteins are not responsible for the dysfunction of SV P--hPIV1 L polymerase complex. Using the chimeric hPIV1/SV P cDNAs, we identified two regions (residues 387--423 and 511--568) on P protein, which are required for the functional interaction with hPIV1 L. These regions overlap with a previously identified domain for oligomer formation and binding to nucleocapsids. Our results indicate that in addition to a P--L binding domain, hPIV1 L requires a specific region on P protein to be biologically functional as a polymerase.