The mechanism and pharmacodynamics of 2-((1H-indol-3-yl)thio/sulfinyl)-N-pheny acetamide derivative as a novel inhibitor against human respiratory syncytial virus.

Human respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infection worldwide. Until now, there are no licenced vaccines or effective antiviral drugs against RSV infections. In our previous work, we found 2-((1H-indol-3-yl)thio/sulfinyl)-N-pheny acetamide derivatives (4-49 C and 1-HB-63) being a novel inhibitor against RSV in vitro. Here, we explored the underlying mechanism of 2-((1H-indol-3-yl)thio/sulfinyl)-N-pheny acetamide derivatives to inhibit RSV replication in vitro and disclosed that 4-49 C worked as the inhibitor of membrane fusion and 1-HB-63 functioned at the stage of RSV genome replication/transcription. Yet, both of them could not inhibit RSV infection of BALB/c mice by using RSV-Luc, in vivo imaging and RT-qPCR analyses, for which it may be due to the fast metabolism in vivo. Our work suggests that further structural modification and optimisation of 2-((1H-indol-3-yl) thio/sulfinyl)-N-pheny acetamide derivative are needed to obtain drug candidates with effective anti-RSV activities in vivo.

Inhibitory effect of genetically engineered mesenchymal stem cells with Apoptin on hepatoma cells in vitro and in vivo.

Hepatocellular carcinoma (HCC) is an aggressive tumor and has become one of the most frequent causes of cancer death in the world. The rate of post-operative recurrence and metastasis are still high even though after surgical resection. It is a difficult problem with extraordinary importance for the clinical treatment. So stem cell therapy becomes one of the anti-tumor biotherapy methods which is exploring. Due to the feature of homing to tumor site and immunosuppressive, mesenchymal stem cells (MSCs) have the capacity of gene treatment to tumor as a vehicle. Apoptin derived from chicken anemia virus is one kind of protein with an inherent ability to lyse cancer cells while leaving normal cells unharmed. Adenovirus (Ad) vectors can be modified to deliver therapeutic genes with the advantages of low toxicity and high transfer capacity. Now it has not been reported that combining MSCs and Adenovirus with Apoptin are used in HCC treatment. This study intends to construct recombinant adenovirus which expresses Apoptin and then infects human bone marrow MSCs, and explore the migration of MSCs to the hepatoma cells and inhibitory effect of genetically engineered mesenchymal stem cells with Apoptin on hepatoma cells in vitro and in vivo. Our research successfully established the recombinant Ad which was constructed by Ad system, and obtained MSCs which could secrete Apoptin. We found that both the modified MSCs with Apoptin and their conditional medium significantly inhibited the proliferation of liver cancer cells HepG2, which provided a novel means and experimental basis for stem cell treatment for HCC. This study tries to search for a stem cell therapy for cancers, which will provide a new approach and experimental basis for the clinical treatment of cancer. At the same time, this research will also provide experimental basis for a novel in vivo drug delivery system through stem cells as vehicle, which will resolve immune rejection induced by repeated applications of drug directly delivered by Ad vectors and reduce the high cost of a large-scale production and purification of exogenous drugs.

[Construction and rescue of the minigenome of bovine parainfluenza virus type 3 based on T7 promoter expression system].

Objective: To establish a T7 promoter based reverse genetics system competent for the rescue of bovine parainfluenza virus type 3 (BPIV3). Methods: We constructed three helper plasmids of px8δT-PT1-bPIV3-NP, px8δT-PT1-bPIV3-P and px8δT-PT1-bPIV3-L and one minigenome plasmid of pSC11-bPIV3-EGFP containing open reading frame (ORF) of the enhanced green fluorescent protein (EGFP) and cis-acting elements including BPIV3 leader region, gene start (GS), gene end (GE) and trailer region. All these plasmids are under the control of T7 promoter and identified by restriction endonuclease analysis. We rescued the pSC11-bPIV3-EGFP by two different methods. Then, we observed the fluorescence expression over time with fluorescence microscopy. Results: We successfully constructed a reverse genetic system based 4 plasmids under the control of T7 promoter and finished the rescue operation to the minigenome of BPIV3. Conclusion: This system can be further applied to investigate the function of BPIV3 genome by deletion and mutation of its genes.

[Construction and identification of helper-dependent adenoviral vector encoding hemagglutinin protein of swin-origin influenza virus A H1N1].

Abstract: In order to investigate immune protection against swine-origin influenza virus (S-OIV) A H1N1, the helper-dependent adenovirus vector (HDAd) system was exploited to construct recombinant HDAd encoding hemagglutinin (HA). The HA gene was synthesized and cloned to the HDAd backbone. Then, the HDAd/HA DNA molecules were transfected into 293Cre4 cells with calcium phosphate. The cells were infected by helper virus 16 hours after the transfection. The 293Cre4 cells were coinfected with HDAd/HA and the helper virus for large-scale preparation of HDAd/HA. The HDAd/HA was obtained and purified twice with CsCI density ultracentrifugation and observed morphologically under transmission electron microscope, and the expression of HA protein was analyzed with RTPCR. Recombinant HDAd/HA expressing HA protein was successfully constructed which could pave the way for in vivo investigation on immunogenicity and efficacy against S-OIV A H1N1 infection.

A novel helper-dependent adenovirus-based cell culture model for Hepatitis C virus replication and production.

BACKGROUND: By using the hepatitis C virus (HCV) genotype 2a JFH-1 or its chimeric strains, a HCV infection system has been previously developed through several methods- such as in vitro-transcribed JFH1-RNA transfection or stable transfection of the JFH1 cDNA into human hepatoma Huh-7 cell line or its derivatives. However, other reliable methods for delivery of the HCV genome into cells are still worth trying. The helper-dependent adenovirus (HDAd) is devoid of all viral coding sequences and has a package capacity of 37 kb, which is suitably large for the delivery of the HCV genome. Here we report a new method for delivery of the HCV genome into Huh-7 and HepG2 cells by using the HDAd vector. RESULTS: Our results demonstrated that the infection of Huh-7 cells with the HDAdJFH1 virus led to efficient HCV replication and virion production. We found that the HCV viral RNA levels could reach 107 copies per milliliter (ml) in the culture medium. HDAdJFH1-infected Huh-7 cells could be cultured for 8 passages with the culture medium remaining infectious for naïve Huh-7 cells throughout this period. This infection system proved effective for evaluating the anti-HCV effects of IFN-α in Huh-7 cells. Co-infection of HepG2 cells with the HDAdJFH1 and HDAdmiR-122 virus also resulted in HCV expression and replication. CONCLUSION: This is the first report of an HDAd-based strategy for HCV replication and production in vitro.

Intranasal immunization with a helper-dependent adenoviral vector expressing the codon-optimized fusion glycoprotein of human respiratory syncytial virus elicits protective immunity in BALB/c mice.

BACKGROUND: Human respiratory syncytial virus (RSV) is a serious pediatric pathogen of the lower respiratory tract. Currently, there is no clinically approved vaccine against RSV infection. Recent studies have shown that helper-dependent adenoviral (HDAd) vectors may represent effective and safe vaccine vectors. However, viral challenge has not been investigated following mucosal vaccination with HDAd vector vaccines. METHODS: To explore the role played by HDAd as an intranasally administered RSV vaccine vector, we constructed a HDAd vector encoding the codon optimized fusion glycoprotein (Fsyn) of RSV, designated HDAd-Fsyn, and delivered intranasally HDAd-Fsyn to mice. RESULTS: RSV-specific humoral and cellular immune responses were generated in BALB/c mice, and serum IgG with neutralizing activity was significantly elevated after a homologous boost with intranasal (i.n.) application of HDAd-Fsyn. Humoral immune responses could be measured even 14 weeks after a single immunization. Immunization with i.n. HDAd-Fsyn led to effective protection against RSV infection on challenge. CONCLUSION: The results indicate that HDAd-Fsyn can induce powerful systemic immunity against subsequent i.n. RSV challenge in a mouse model and is a promising candidate vaccine against RSV infection.

Immunogenicity in Mice Immunized with Recombinant Adenoviruses Expressing Varicella-Zoster Virus Envelope Glycoprotein E.

Herpes zoster (HZ) is a disease caused by the reactivation of latent varicella-zoster virus (VZV). The subunit vaccine, Shingrix®, and live attenuated vaccine, Zostavax®, could be used as an HZ vaccine that prevents HZ from being developed due to the reactivation of latent VZV in the sensory ganglia due to aging, stress or immunosuppression. In this study, the recombinant adenoviruses rChAd63/gE expressing glycoprotein E (gE) of VZV based on chimpanzee adenovirus serotype 63 (ChAd63) were constructed and investigated for the immunogenicity of different immune pathways in C57BL/6 mice. The results showed similar CD4+ T and CD8+ T cell responses to Shingrix® were induced in mice vaccinated using rChAd63/gE via different immune pathways. This study elucidates that recombinant adenoviruses expressing VZV gE could be appropriate for further development as a new HZ vaccine candidate via different immune pathways.

Tracking of Mutational Signature of SARS-CoV-2 Omicron on Distinct Continents and Little Difference was Found.

The Omicron variant is currently ravaging the world, raising serious concern globally. Monitoring genomic variations and determining their influence on biological features are critical for tracing its ongoing transmission and facilitating effective measures. Based on large-scale sequences from different continents, this study found that: (i) The genetic diversity of Omicron is much lower than that of the Delta variant. Still, eight deletions (Del 1-8) and 1 insertion, as well as 130 SNPs, were detected on the Omicron genomes, with two deletions (Del 3 and 4) and 38 SNPs commonly detected on all continents and exhibiting high-occurring frequencies. (ii) Four groups of tightly linked SNPs (linkage I-IV) were detected, among which linkage I, containing 38 SNPs, with 6 located in the RBD, increased its occurring frequency remarkably over time. (iii) The third codons of the Omicron shouldered the most mutation pressures, while the second codons presented the least flexibility. (iv) Four major mutants with amino acid substitutions in the RBD were detected, and further structural analysis suggested that the substitutions did not alter the viral receptor binding ability greatly. It was inferred that though the Omicron genome harbored great changes in antigenicity and remarkable ability to evade immunity, it was immune-pressure selected. This study tracked mutational signatures of Omicron variant and the potential biological significance of the SNPs, and the linkages await further functional verification.

Comparative analysis of human respiratory syncytial virus evolutionary patterns during the COVID-19 pandemic and pre-pandemic periods.

The COVID-19 pandemic has resulted in the implementation of strict mitigation measures that have impacted the transmission dynamics of human respiratory syncytial virus (HRSV). The measures also have the potential to influence the evolutionary patterns of the virus. In this study, we conducted a comprehensive analysis comparing genomic variations and evolving characteristics of its neutralizing antigens, specifically F and G proteins, before and during the COVID-19 pandemic. Our findings showed that both HRSV A and B exhibited an overall chronological evolutionary pattern. For the sequences obtained during the pandemic period (2019-2022), we observed that the HRSV A distributed in A23 genotype, but formed into three subclusters; whereas the HRSV B sequences were relatively concentrated within genotype B6. Additionally, multiple positively selected sites were detected on F and G proteins but none were located at neutralizing antigenic sites of the F protein. Notably, amino acids within antigenic site III, IV, and V of F protein remained strictly conserved, while some substitutions occurred over time on antigenic site Ø, I, II and VIII; substitution S389P on antigenic site I of HRSV B occurred during the pandemic period with nearly 50% frequency. However, further analysis revealed no substitutions have altered the structural conformations of the antigenic sites, the vial antigenicity has not been changed. We inferred that the intensive public health interventions during the COVID-19 pandemic did not affect the evolutionary mode of HRSV.

Purification of human respiratory syncytial virus fusion glycoprotein.

Human respiratory syncytial virus (RSV) fusion glycoprotein (F) elicits neutralizing antibodies to RSV and has therefore attracted much attention as a suitable candidate antigen in the development of gene-based vaccines against RSV infections. However, a major obstacle in vaccine development has been the problem of antigen purification. To address this problem, we have developed a new method that combines sucrose gradient ultracentrifugation and a two-step chromatographic process, to purify RSV F from RSV particles propagated in HEp-2 cells. Analysis of the fractions produced using this method showed recovery of a functional homodimer with a molecular weight of 140 kDa, and 54% preservation of the original F.

Evolutionary Pattern Comparisons of the SARS-CoV-2 Delta Variant in Countries/Regions with High and Low Vaccine Coverage.

It has been argued that vaccine-breakthrough infections of SARS-CoV-2 would likely accelerate the emergence of novel variants with immune evasion. This study explored the evolutionary patterns of the Delta variant in countries/regions with relatively high and low vaccine coverage based on large-scale sequences. Our results showed that (i) the sequences were grouped into two clusters (L and R); the R cluster was dominant, its proportion increased over time and was higher in the high-vaccine-coverage areas; (ii) genetic diversities in the countries/regions with low vaccine coverage were higher than those in the ones with high vaccine coverage; (iii) unique mutations and co-mutations were detected in different countries/regions; in particular, common co-mutations were exhibited in highly occurring frequencies in the areas with high vaccine coverage and presented in increasing frequencies over time in the areas with low vaccine coverage; (iv) five sites on the S protein were under strong positive selection in different countries/regions, with three in non-C to U sites (I95T, G142D and T950N), and the occurring frequencies of I95T in high vaccine coverage areas were higher, while G142D and T950N were potentially immune-pressure-selected sites; and (v) mutation at the N6-methyladenosine site 4 on ORF7a (C27527T, P45L) was detected and might be caused by immune pressure. Our study suggested that certain variation differences existed between countries/regions with high and low vaccine coverage, but they were not likely caused by host immune pressure. We inferred that no extra immune pressures on SARS-CoV-2 were generated with high vaccine coverage, and we suggest promoting and strengthening the uptake of the COVID-19 vaccine worldwide, especially in less developed areas.

The protective immunity induced by intranasally inoculated serotype 63 chimpanzee adenovirus vector expressing human respiratory syncytial virus prefusion fusion glycoprotein in BALB/c mice.

Human respiratory syncytial virus (RSV) is a ubiquitous pediatric pathogen causing serious lower respiratory tract disease worldwide. No licensed vaccine is currently available. In this work, the coding gene for mDS-Dav1, the full-length and prefusion conformation RSV fusion glycoprotein (F), was designed by introducing the stabilized prefusion F (preF) mutations from DS-Cav1 into the encoding gene of wild-type RSV (wtRSV) F protein. The recombinant adenovirus encoding mDS-Cav1, rChAd63-mDS-Cav1, was constructed based on serotype 63 chimpanzee adenovirus vector and characterized in vitro. After immunizing mice via intranasal route, the rChAd63-mDS-Cav1 induced enhanced neutralizing antibody and F-specific CD8+ T cell responses as well as good immune protection against RSV challenge with the absence of enhanced RSV disease (ERD) in BALB/c mice. The results indicate that rChAd63-mDS-Cav1 is a promising mucosal vaccine candidate against RSV infection and warrants further development.

A polymorphism in CALHM1 is associated with temporal lobe epilepsy.

A recent study suggests that the P86L polymorphism (rs2986017) in the calcium homeostasis modulator 1 (CALHM1) gene interferes with calcium homeostasis and increases amyloid ß (Aß) levels. Moreover, in vitro and in vivo data show that both calcium homeostasis and high levels of Aß play an important role in the induction and maintenance of epileptic seizures in hippocampus, indicating CALHM1 might play a potential role in pathophysiological pathways involved in temporal lobe epilepsy (TLE). The aim of this study was to investigate the genetic contribution of CALHM1 to TLE. Five single-nucleotide polymorphisms (SNPs) of CALHM1 were selected and genotyped using polymerase chain reaction restriction fragment length polymorphism in 560 patients with TLE and 401 healthy controls. We found a positive association between rs11191692 and TLE, but a negative result between rs2986017 and TLE. The rs11191692-A allele frequency was found in 32.4% of the patients and in 26.2% of control subjects (OR=1.35, 95% CI=1.10-1.65, uncorrected P=0.003, corrected P=0.015). Furthermore, the positive association between rs11191692 and TLE independent of apolipoprotein E ε4 was supported by five SNPs haplotype analysis. The results of this study provide the first evidence that the SNP rs11191692 in CALHM1 confers highly increased susceptibility to TLE.

[Antibody responses induced by mucosal DNA vaccine encoding the codon-optimized F protein of human respiratory syncytial virus (RSV) delivered with attenuated Salmonella typhimurium].

OBJECTIVE: In order to investigate antibody responses by musosal DNA vaccines encoding the codon-optimized F protein of human respiratory syncytial virus (RSV) delivered with attenuated Salmonella typhimurium aroA strain SL7207 (SL7207) via intranasal or intragastric routes. METHODS: After the codon-optimized F gene was synthesized, we constructed eukaryotic expression plasmid pcDNA3.1/Fsyn and transformed it into SL7207 to get recombinant SL7207 of SL7207/pcDNA3.1/Fsyn. Then, SL7207/pcDNA3.1/Fsyn was exploited to evaluate its immunogenicity in BALB/c mice administered intranasally or intragastrically. The resultant serum and mucosal antibody responses were analyzed by indirect ELISA. RESULTS: Compared with intragastric immunization group, intranasal immunization group achieved higher level of RSV specific serum IgG and secretion IgA (SIgA) (P < 0.05). Moreover, F protein expressed by the codon-optimized F gene of Fsyn was of elevated immunogenicity, compared with wild type F (Fwt) (P < 0.05). CONCLUSION: Intranasal immunization and codon optimization approaches can improve antibody responses of RSV DNA vaccine delivered by attenuated Salmonella typhimurium aroA strain SL7207.

Genetic diversity and molecular evolution of human respiratory syncytial virus A and B.

Human respiratory syncytial viruses (RSVs) are classified into two major groups (A and B) based on antigenic differences in the G glycoprotein. To investigate circulating characteristics and phylodynamic history of RSV, we analyzed the genetic variability and evolutionary pattern of RSVs from 1977 to 2019 in this study. The results revealed that there was no recombination event of intergroup. Single nucleotide polymorphisms (SNPs) were observed through the genome with the highest occurrence rate in the G gene. Five and six sites in G protein of RSV-A and RSV-B, respectively, were further identified with a strong positive selection. The mean evolutionary rates for RSV-A and -B were estimated to be 1.48 × 10-3 and 1.92 × 10-3 nucleotide substitutions/site/year, respectively. The Bayesian skyline plot showed a constant population size of RSV-A and a sharp expansion of population size of RSV-B since 2005, and an obvious decrease 5 years later, then became stable again. The total population size of RSVs showed a similar tendency to that of RSV-B. Time-scaled phylogeny suggested a temporal specificity of the RSV-genotypes. Monitoring nucleotide changes and analyzing evolution pattern for RSVs could give valuable insights for vaccine and therapy strategies against RSV infection.

Biological Significance of the Genomic Variation and Structural Dynamics of SARS-CoV-2 B.1.617.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants have been emerging and circulating globally since the start of the COVID-19 pandemic, of which B.1.617 lineage that was first reported in India at the end of 2020, soon became predominant. Tracing genomic variations and understanding their impact on the viral properties are the foundations for the vaccine and drug development and for the mitigation measures to be taken or lifted. In this study, 1,051 near-complete genomes and 1,559 spike (S) sequences belonging to the B.1.617 were analyzed. A genome-wide spread of single nucleotide polymorphisms (SNPs) was identified. Of the high frequency mutations identified, 61% (11/18) involved structural proteins, despite two third of the viral genome encoding nonstructural proteins. There were 22 positive selection sites, mostly distributed across the S protein, of which 16 were led by non-C to U transition and should be of a special attention. Haplotype network revealed that a large number of daughter haplotypes were continually derived throughout the pandemic, of which H177, H181 H219 and H286 from the ancestor haplotype H176 of B.1.617.2 were widely prevalent. Besides the well known substitutions of L452R, P681R and deletions of E156 and F157, as well as the potential biological significance, structural analysis in this study still indicated that new amino acid changes in B.1.617, such as E484Q and N501Y, had reshaped the viral bonding network, and increasingly sequenced N501Y mutant with a potential enhanced binding ability was detected in many other countries in the follow-up monitoring. Although we can't conclude the properties of all the mutants including N501Y thoroughly, it merits focusing on their spread epidemically and biologically.

Synthesis and antiviral activity of a series of novel quinoline derivatives as anti-RSV or anti-IAV agents.

We report herein the synthesis of a series of novel quinoline derivatives, based on the lead compound 1a, identified from a rRSV-mGFP high-throughput screening assay. Our results revealed that target compounds 1b, 1g-h, 1af and 1ah (IC50 = 3.10-6.93 µM) had good in vitro activity against RSV, which were better than 1a and ribavirin. In addition, we found that compound 1g displayed the lower cytotoxicity (CC50: 2490.33 µM) and the highest selective index (SI = 673.06), suggesting its promising potential as a candidate for further development. On the other hand, compounds 1a, 1m, 1v, 1ad-1af and 1ah-1ai (IC50s: 1.87-14.28 µM) were more active against IAV than or comparable to ribavirin (IC50: 15.36 ± 0.93 µM). Particularly, the most active compound 1ae (IC50: 1.87 ± 0.58 µM) was found to be 8.2-fold more potent than the reference drug, which could inhibit the virus transcription and replication cycle at an early stage.

Evaluation of the Safety and Immune Efficacy of Recombinant Human Respiratory Syncytial Virus Strain Long Live Attenuated Vaccine Candidates.

Human respiratory syncytial virus (RSV) infection is the leading cause of lower respiratory tract illness (LRTI), and no vaccine against LRTI has proven to be safe and effective in infants. Our study assessed attenuated recombinant RSVs as vaccine candidates to prevent RSV infection in mice. The constructed recombinant plasmids harbored (5' to 3') a T7 promoter, hammerhead ribozyme, RSV Long strain antigenomic cDNA with cold-passaged (cp) mutations or cp combined with temperature-sensitive attenuated mutations from the A2 strain (A2cpts) or further combined with SH gene deletion (A2cptsΔSH), HDV ribozyme (δ), and a T7 terminator. These vectors were subsequently co-transfected with four helper plasmids encoding N, P, L, and M2-1 viral proteins into BHK/T7-9 cells, and the recovered viruses were then passaged in Vero cells. The rescued recombinant RSVs (rRSVs) were named rRSV-Long/A2cp, rRSV-Long/A2cpts, and rRSV-Long/A2cptsΔSH, respectively, and stably passaged in vitro, without reversion to wild type (wt) at sites containing introduced mutations or deletion. Although rRSV-Long/A2cpts and rRSV-Long/A2cptsΔSH displayed  temperature-sensitive (ts) phenotype in vitro and in vivo, all rRSVs were significantly attenuated in vivo. Furthermore, BALB/c mice immunized with rRSVs produced Th1-biased immune response, resisted wtRSV infection, and were free from enhanced respiratory disease. We showed that the combination of ΔSH with attenuation (att) mutations of cpts contributed to improving att phenotype, efficacy, and gene stability of rRSV. By successfully introducing att mutations and SH gene deletion into the RSV Long parent and producing three rRSV strains, we have laid an important foundation for the development of RSV live attenuated vaccines.

Intranasal vaccination with a helper-dependent adenoviral vector enhances transgene-specific immune responses in BALB/c mice.

Helper-dependent adenoviral (HDAd) vectors were developed primarily for genetic disease therapy by deleting all coding regions for attenuating the host cellular immune response to adenovirus (Ad) and long-lasting gene expression. Recently Harui et al. reported that HDAd vaccine could stimulate superior transgene-specific cytotoxic T lymphocyte (CTL) and antibody responses via the intraperitoneal route, compared to first-generation adenoviral (FGAd) vaccine. This prompted us to explore the potential of HDAd as a vaccine vector administrated intranasally. In this study, we prepared HDAd and FGAd vectors expressing enhanced green fluorescent protein (EGFP), respectively, and compared their efficacy in mice. Mice were immunized intranasally with 5x10(9) vp HDAd or FGAd vector particles. Despite stimulating similar anti-Ad antibody responses with FGAd vaccine in the prime/boost strategy, HDAd vector expressing EGFP displayed superior transgene-specific serum IgG, mucosal IgA and cellular immune response, with the characterization of balanced or mixed Th1/Th2 CD4+ T-cell responses. Meanwhile, a single dose of intranasal (i.n.) vaccine of HDAd-EGFP induced a serum IgG response with more efficacy than FGAd-EGFP. In addition, i.n. boost immunization enhanced transgene-specific humoral and cellular responses, compared to single i.n. HDAd-EGFP immunization. Our results suggest that HDAd has potential for a mucosal vaccine vector via i.n. route, which will be useful for the development of vaccines against respiratory viruses, such as respiratory syncytial virus and influenza virus.

A prime-boost vaccination strategy using attenuated Salmonella typhimurium and a replication-deficient recombinant adenovirus vector elicits protective immunity against human respiratory syncytial virus.

Human respiratory syncytial virus (RSV), for which no clinically approved vaccine is available yet, is globally a serious pediatric pathogen of the lower respiratory tract. Several approaches have been used to develop vaccines against RSV, but none of these have been approved for use in humans. An efficient vaccine-enhancing strategy for RSV is still urgently needed. We found previously that oral SL7207/pcDNA3.1/F and intranasal FGAd/F were able to induce an effective protective immune response against RSV. The heterologous prime-boost immunization regime has been reported recently to be an efficient vaccine-enhancing strategy. Therefore, we investigated the ability of an oral SL7207/pcDNA3.1/F prime and intranasal (i.n.) FGAd/F boost regimen to generate immune responses to RSV. The SL7207/pcDNA3.1/F prime-FGAd/F boost regimen generated stronger RSV-specific humoral and mucosal immune responses in BALB/c mice than the oral SL7207/pcDNA3.1/F regimen alone, and stronger specific cellular immune responses than the i.n. FGAd/F regimen alone. Histopathological analysis showed an increased efficacy against RSV challenge by the heterologous prime-boost regimen. These results suggest that such a heterologous prime-boost strategy can enhance the efficacy of either the SL7207 or the FGAd vector regimen in generating immune responses in BALB/c mice.