Induction of type I interferon secretion through recombinant Newcastle disease virus expressing measles virus hemagglutinin stimulates antibody secretion in the presence of maternal antibodies

Newcastle Disease Virus Displaying an Ectodomain of Middle East Respiratory Syndrome Coronavirus Spike Protein Elicited Robust Humoral and Cellular Immunity in Mice

BACKGROUND

Middle East Respiratory Syndrome Coronavirus (MERS-CoV) causes severe respiratory illness in humans and currently lacks an approved vaccine. The Newcastle disease virus (NDV) vector is a well-established, safe, and effective platform for vaccine development. With recent advancements in stabilizing coronavirus spike proteins to enhance their antigenicity, this study aimed to determine whether modifications to the MERS-CoV spike protein could improve its presentation on NDV particles, allowing the resulting virus to be used as an inactivated vaccine.

METHODS

We codon-optimized the gene encoding the ectodomain of the MERS-CoV spike protein and incorporated modifications at the S1/S2 and S2' cleavage sites, along with a proline substitution at residues V1060-L1061. This modified spike gene was inserted into the NDV genome to create the NDV-SMERS virus. After purification and inactivation, the vaccine's immunogenicity was assessed in mice.

RESULTS

Mice immunized with the inactivated NDV-SMERS vaccine developed robust anti-spike IgGs, neutralizing antibodies, and cellular immune responses. The study demonstrated that modifications to the MERS-CoV spike protein were essential for its effective presentation on NDV particles. Additionally, the spike gene insert remained stable through five egg passages, confirming the vector's stability.

CONCLUSIONS

Engineering the MERS-CoV spike protein is crucial for its successful display on NDV particles. The strong immune responses elicited by the NDV-SMERS vaccine in mice highlight that NDV is a promising, safe, and effective platform for MERS-CoV vaccination.

Feasibility of Using a Type I IFN-Based Non-Animal Approach to Predict Vaccine Efficacy and Safety Profiles

Animal-based tests are used for the control of vaccine quality. However, because highly purified and safe vaccines are now available, alternative approaches that can replace or reduce animal use for the assessment of vaccine outcomes must be established. In vitro tests for vaccine quality control exist and have already been implemented. However, these tests are specifically designed for some next-generation vaccines, and this makes them not readily available for testing other vaccines. Therefore, universal non-animal tests are still needed. Specific signatures of the innate immune response could represent a promising approach to predict the outcome of vaccines by non-animal methods. Type I interferons (IFNs) have multiple immunomodulatory activities, which are exerted through effectors called interferon stimulated genes (ISGs), and are one of the most important immune signatures that might provide potential candidate molecular biomarkers for this purpose. This paper will mainly examine if this idea might be feasible by analyzing all relevant published studies that have provided type I IFN-related biomarkers for evaluating the safety and efficacy profiles of vaccines using an advanced transcriptomic approach as an alternative to the animal methods. Results revealed that such an approach could potentially provide biomarkers predictive of vaccine outcomes after addressing some limitations.

Whole blood gene expression signature in patients with obstructive sleep apnea and effect of continuous positive airway pressure treatment

The molecular mechanisms of obstructive sleep apnea (OSA), in particular the gene expression patterns in whole blood of patients with OSA, can shed more light on the underlying pathophysiology of OSA and suggest potential biomarkers. In the current study, we have enrolled thirty patients with untreated moderate-severe OSA together with 20 BMI, age, and sex-matched controls and 15 normal-weight controls. RNA-sequencing of whole blood and home sleep apnea testing were performed in the untreated state and after three and twelve months of continuous positive airway pressure (CPAP) treatment. Analysis of the whole blood transcriptome of the patients with OSA revealed a unique pattern of differential expression with a significant number of downregulated immune-related genes including many heavy and light chain immunoglobulins and interferon-inducible genes. This was confirmed by the gene ontology analysis demonstrating enrichment with the biological processes associated with various immune functions. Expression of these genes was recovered after three months of CPAP treatment. After 12 months of CPAP treatment, the overall gene expression profile returns to the initial, untreated level. In addition, we have confirmed the importance of choosing BMI-matched controls as a reference group as opposed to normal-weight healthy individuals based on the significantly different gene expression signatures between these two groups.

A New Variant Among Newcastle Disease Viruses Isolated in the Democratic Republic of the Congo in 2018 and 2019

Newcastle disease (ND) is a highly transmissible and devastating disease that affects poultry and wild birds worldwide. Comprehensive knowledge regarding the characteristics and epidemiological factors of the ND virus (NDV) is critical for the control and prevention of ND. Effective vaccinations can prevent and control the spread of the NDV in poultry populations. For decades, the Democratic Republic of the Congo (DRC) has reported the impacts of ND on commercial and traditional poultry farming systems. The reports were preliminary clinical observations, and few cases were confirmed in the laboratory. However, data on the phylogenetic, genetic, and virological characteristics of NDVs circulating in the DRC are not available. In this study, the whole-genome sequences of three NDV isolates obtained using the next-generation sequencing method revealed two isolates that were a new variant of NDV, and one isolate that was clustered in the subgenotype VII.2. All DRC isolates were velogenic and were antigenically closely related to the vaccine strains. Our findings reveal that despite the circulation of the new variant, ND can be controlled in the DRC using the current vaccine. However, epidemiological studies should be conducted to elucidate the endemicity of the disease so that better control strategies can be implemented.

Newcastle Disease Virus as a Vaccine Vector for 20 Years: A Focus on Maternally Derived Antibody Interference

It has been 20 years since Newcastle disease virus (NDV) was first used as a vector. The past two decades have witnessed remarkable progress in vaccine generation based on the NDV vector and optimization of the vector. Protective antigens of a variety of pathogens have been expressed in the NDV vector to generate novel vaccines for animals and humans, highlighting a great potential of NDV as a vaccine vector. More importantly, the research work also unveils a major problem restraining the NDV vector vaccines in poultry, i.e., the interference from maternally derived antibody (MDA). Although many efforts have been taken to overcome MDA interference, a lack of understanding of the mechanism of vaccination inhibition by MDA in poultry still hinders vaccine improvement. In this review, we outline the history of NDV as a vaccine vector by highlighting some milestones. The recent advances in the development of NDV-vectored vaccines or therapeutics for animals and humans are discussed. Particularly, we focus on the mechanisms and hypotheses of vaccination inhibition by MDA and the efforts to circumvent MDA interference with the NDV vector vaccines. Perspectives to fill the gap of understanding concerning the mechanism of MDA interference in poultry and to improve the NDV vector vaccines are also proposed.

Evaluation on the efficacy and immunogenicity of recombinant DNA plasmids expressing S gene from porcine epidemic diarrhea virus and VP7 gene from porcine rotavirus

Porcine rotavirus (PoRV) and porcine epidemic diarrhea virus (PEDV) usually co-infect pigs in modern large-scale piggery, which both can cause severe diarrhea in newborn piglets and lead to significant economic losses to the pig industry. The VP7 protein is the main coat protein of PoRV, and the S protein is the main structural protein of PEDV, which are capable of inducing neutralizing antibodies in vivo. In this study, a DNA vaccine pPI-2.EGFP.VP7.S co-expressing VP7 protein of PoRV and S protein of PEDV was constructed. Six 8-week-old mice were immunized with the recombinant plasmid pPI-2.EGFP.VP7.S. The high humoral immune responses (virus specific antibody) and cellular immune responses (IFN-γ, IL-4, and spleen lymphocyte proliferation) were evaluated. The immune effect through intramuscular injection increased with plasmid dose when compared with subcutaneous injection. The immune-enhancing effect of IFN-α adjuvant was excellent compared with pig spleen transfer factor and IL-12 adjuvant. These results demonstrated that pPI-2.EGFP.VP7.S possess the immunological functions of the VP7 proteins of PoRV and S proteins of PEDV, indicating that pPI-2.EGFP.VP7.S is a candidate vaccine for porcine rotaviral infection (PoR) and porcine epidemic diarrhea (PED).

Decreased microRNA-140-5p contributes to respiratory syncytial virus disease through targeting Toll-like receptor 4

The abnormal expression of miRNAs (miRs) has previously been reported in respiratory syncytial virus (RSV) disease. However, to the best of our knowledge, the expression of miR-140-5p in patients with an RSV infection has never been explored. Reverse transcription-quantitative polymerase chain reaction was performed to analyze the level of miR-140-5p in the blood and nasopharyngeal airway samples. ELISAs were performed to determine the levels of tumor necrosis factor α, interleukin (IL)-1β, IL-6 and IL-8. A dual luciferase reporter assay was also performed to investigate the possible target gene of miR-140-5p. The results demonstrated that the levels of miR-140-5p were significantly decreased in the nasal mucosal and peripheral blood samples of patients with RSV infection. It was also revealed that overexpression of miR-140-5p decreased the inflammatory responses, while inhibition of miR-140-5p enhanced the inflammatory responses. Additionally, three binding sites of miR-140-5p in the 3untranslated region (UTR) of Toll-like receptor (TLR)4 were identified and a dual luciferase reporter assay demonstrated that miR-140-5p significantly suppressed the relative luciferase activity of pmirGLO-TLR4-3UTR. Furthermore, the level of miR-140-5p was shown to be increased following interferon (IFN)α incubation. Notably, inhibition of miR-140-5p markedly attenuated IFNα-mediated downregulation of tumor necrosis factor α, and interleukin-1β, -6 and -8 in BEAS-2B cells. In summary, decreased miR-140-5p levels are involved in RSV-infection diseases primarily through targeting TLR4.

Recombinant NDV expressing cytokines or fliC confers a quick immune response against NDV challenge and resistance to maternal antibody

Currently, there are two major bottleneck problems which seriously affect prevention of the Newcastle disease (ND): interference of maternal antibody on NDV vaccination and slow production of neutralization antibody. To overcome these problems, in present study, four rNDV vaccine strains expressing bio-adjuvants chIL2, chIL15, chGM-CSF or fliC gene were constructed and rescued using reverse genetics approach. The HI antibody titers of SPF birds immunized with rNDV reached to 5.5log2, 4.7log2, 6.5log2 and 5.8log2, respectively at the 8th day post immunization, while the antibody titers of the parental virus and control were 3.3log2 and 1log2, respectively. The immunized chickens were challenged by 10⁴ELD₅₀ dose of the virulent NDV BJ strains at the 7th day post immunization. The protection rate of the four rNDVs bio-adjuvant groups was 100%, while the protection rate of the parental group was 80%. We also examined the anti-maternal antibody activity of these adjuvant vaccines by detection HI titer after vaccination of chickens with high (8.4log2) or low (5log2) maternal antibody levels. In chicken flock with higher maternal antibody, parental strain could not resist the influence of the maternal antibody and induce any notable change of HI antibody kinetics. However, both rClon30-chGM-CSF and rClon30-flic were able to resist the influence of the maternal antibody and maintained the HI antibody above the protection level during the 14day's experiment. In chicken flock with lower maternal antibody, the parental rclone30 strain could not induce HI titer to the protection level until the 14th day, but both rClon30-GM-CSF and clone30-fliC raised the HI antibody to above the protection level at the 7th day post vaccination.

Type I interferon related genes are common genes on the early stage after vaccination by meta-analysis of microarray data

The objective of this study was to find common immune mechanism across different kinds of vaccines. A meta-analysis of microarray datasets was performed using publicly available microarray Gene Expression Omnibus (GEO) and Array Express data sets of vaccination records. Seven studies (out of 35) were selected for this meta-analysis. A total of 447 chips (145 pre-vaccination and 302 post-vaccination) were included. Significance analysis of microarrays (SAM) program was used for screening differentially expressed genes (DEGs). Functional pathway enrichment for the DEGs was conducted in DAVID Gene Ontology (GO) database. Twenty DEGs were identified, of which 10 up-regulated genes involved immune response. Six of which were type I interferon (IFN) related genes, including LY6E, MX1, OAS3, IFI44L, IFI6 and IFITM3. Ten down-regulated genes mainly mediated negative regulation of cell proliferation and cell motion. Results of a subgroup analysis showed that although the kinds of genes varied widely between days 3 and 7 post vaccination, the pathways between them are basically the same, such as immune response and response to viruses, etc. For an independent verification of these 6 type I IFN related genes, peripheral blood mononuclear cells (PBMCs) were collected at baseline and day 3 after the vaccination from 8 Enterovirus 71(EV71) vaccinees and were assayed by RT-PCR. Results showed that the 6 DEGs were also upregulated in EV71 vaccinees. In summary, meta-analysis methods were used to explore the immune mechanism of vaccines and results indicated that the type I IFN related genes and corresponding pathways were common in early immune responses for different kinds of vaccines.

Comparing the Primary and Recall Immune Response Induced by a New EV71 Vaccine Using Systems Biology Approaches

Three inactivated EV71 whole-virus vaccines have completed Phase III clinical trials in mainland China, with high efficacy, satisfactory safety, and sustained immunogenicity. However, the molecular mechanisms how this new vaccine elicit potent immune response remain poorly understood. To characterize the primary and recall responses to EV71 vaccines, PBMC from 19 recipients before and after vaccination with EV71 vaccine are collected and their gene expression signatures after stimulation with EV71 antigen were compared. The results showed that primary and recall response to EV71 antigen have both activated an IRF7 regulating type I interferon and antiviral immune response network. However, up-regulated genes involved in T cell activation regulated by IRF1, inflammatory response, B-cell activation and humoral immune response were only observed in recall response. The specific secretion of IL-10 in primary response and IL-2,IP-10,CCL14a, CCL21 in recall response was consistent with the activation of immune response process found in genes. Furthermore, the expression of MX1 and secretion of IP-10 in recall response were strongly correlated with NTAb level at 180d after vaccination (r = 0.81 and 0.99). In summary, inflammatory response, adaptive immune response and a stronger antiviral response were indentified in recall response.

Success of measles virotherapy in ATL depends on type I interferon secretion and responsiveness

Adult T cell leukemia/lymphoma (ATL) is a highly aggressive CD4+/CD25+ T-cell malignancy caused by human T cell lymphotropic virus type 1 (HTLV-1). Previous studies in the MET-1 cell/NOD/SCID mouse model of ATL demonstrated that MET-1 cells are very susceptible to measles virus (MV) oncolytic therapy. To further evaluate the potential of MV therapy in ATL, the susceptibility of several HTLV-1 transformed CD4+ T cell lines (MT-1, MT-2, MT-4 and C8166-45) as well as HTLV-1 negative CD4+ T cell lines (Jurkat and CCRF-CEM) to infection with MV was tested in vitro. All cell lines were permissive to MV infection and subsequent cell death, except MT-1 and CCRF-CEM cells which were susceptible and permissive to MV infection, but resistant to cell death. The resistance to MV-mediated cell death was associated with IFNβ produced by MT-1 and CCRF-CEM cells. Inhibition of IFNβ rendered MT-1 and CCRF-CEM cells susceptible to MV-mediated cell death. Cells susceptible to MV-induced cell death did not produce nor were responsive to IFNβ. Upon infection with Newcastle Disease Virus (NDV), MT-1 and CCRF-CEM but not the susceptible cell lines up-regulated pSTAT-2. In vivo, treatment of tumors induced by MT-1 cell lines which produce IFNβ demonstrated only small increases in mean survival time, while only two treatments prolonged mean survival time in mice with MET-1 tumors deficient in type I interferon production. These results indicate that type I interferon production is closely linked with the inability of tumor cells to respond to type I interferon. Screening of tumor cells for type I interferon could be a useful strategy to select candidate patients for MV virotherapy.

Alpha/beta interferon receptor signaling amplifies early proinflammatory cytokine production in the lung during respiratory syncytial virus infection

Type I interferons (IFNs) are produced early upon virus infection and signal through the alpha/beta interferon (IFN-α/β) receptor (IFNAR) to induce genes that encode proteins important for limiting viral replication and directing immune responses. To investigate the extent to which type I IFNs play a role in the local regulation of inflammation in the airways, we examined their importance in early lung responses to infection with respiratory syncytial virus (RSV). IFNAR1-deficient (IFNAR1^−/−) mice displayed increased lung viral load and weight loss during RSV infection. As expected, expression of IFN-inducible genes was markedly reduced in the lungs of IFNAR1^−/− mice. Surprisingly, we found that the levels of proinflammatory cytokines and chemokines in the lungs of RSV-infected mice were also greatly reduced in the absence of IFNAR signaling. Furthermore, low levels of proinflammatory cytokines were also detected in the lungs of IFNAR1^−/− mice challenged with noninfectious innate immune stimuli such as selected Toll-like receptor (TLR) agonists. Finally, recombinant IFN-α was sufficient to potentiate the production of inflammatory mediators in the lungs of wild-type mice challenged with innate immune stimuli. Thus, in addition to its well-known role in antiviral resistance, type I IFN receptor signaling acts as a central driver of early proinflammatory responses in the lung. Inhibiting the effects of type I IFNs may therefore be useful in dampening inflammation in lung diseases characterized by enhanced inflammatory cytokine production.

IMPORTANCE The initial response to viral infection is characterized by the production of interferons (IFNs). One group of IFNs, the type I IFNs, are produced early upon virus infection and signal through the IFN-α/β receptor (IFNAR) to induce proteins important for limiting viral replication and directing immune responses. Here we examined the importance of type I IFNs in early responses to respiratory syncytial virus (RSV). Our data suggest that type I IFN production and IFNAR receptor signaling not only induce an antiviral state but also serve to amplify proinflammatory responses in the respiratory tract. We also confirm this conclusion in another model of acute inflammation induced by noninfectious stimuli. Our findings are of relevance to human disease, as RSV is a major cause of infant bronchiolitis and polymorphisms in the IFN system are known to impact disease severity.

Synergistic induction of interferon α through TLR-3 and TLR-9 agonists stimulates immune responses against measles virus in neonatal cotton rats

Immunization of neonates is problematic because of the immaturity of their immune system and the presence of maternal antibodies, both of which affect B cell responses. We tested the effects of co-administration of measles vaccine with a combination of TLR-3 (pI:C) and TLR-9 (ODN2216, optimized for human TLR-9) agonists on the ability to induce an effective immune response in neonatal cotton rats. TLR-9 expression in cotton rat lymphocytes was at the same low level as in human lymphocytes, which is in contrast to mice that express higher levels. TLR-3 expression levels were comparable between cotton rats, mice, and humans. A combination of TLR-3 and TLR-9 agonists synergistically induced high levels of type I interferon in neonatal spleen cells and higher levels of IL-10 as compared to adult spleen cells. Previously, it was shown that type I interferon stimulates B cell generation and antibody secretion in vitro and in vivo, and that IL-10 has immunomodulatory effects. The simultaneous induction of both type I interferon and IL-10 indicated that this immunization regimen could be both effective and safe. Neonatal cotton rats did not generate neutralizing antibodies after measles vaccination in the first week of life (although a T cell response was detectable). However, co-administration of the TLR-3 and TLR-9 agonist combination with measles vaccine in neonatal cotton rats induced neutralizing antibody responses comparable to those after adult immunization. This immunization regimen was also effective in neonatal cotton rats in the presence of natural maternal antibodies, although antibody titers were lower than those after immunization in the absence of maternal antibodies.

The cotton rat (Sigmodon hispidus) as an animal model for respiratory tract infections with human pathogens

Respiratory viral infection is a great human health concern, resulting in disease, death and economic losses. Cotton rats (Sigmodon hispidus) have been particularly useful in the study of the pathogenesis of human respiratory virus infections, including the development and testing of antiviral compounds and vaccines. In this article, the authors outline the advantages of the cotton rat compared with the mouse as a model for infection with measles virus, respiratory syncytial virus, influenza virus, human parainfluenza virus and human metapneumovirus. From the literature and their own experience, the authors summarize guidelines for handling, maintaining and breeding cotton rats. In addition, they offer technical tips for carrying out infection experiments and provide information about the large array of immunological assays and reagents available for the study of immune responses (macrophages, dendritic cells, T cells, B cells, antibodies, chemokines and cytokines) in cotton rats.

Rescue of recombinant Newcastle disease virus from cDNA

Newcastle disease virus (NDV), the prototype member of the Avulavirus genus of the family Paramyxoviridae(1), is a non-segmented, negative-sense, single-stranded, enveloped RNA virus (Figure 1) with potential applications as a vector for vaccination and treatment of human diseases. In-depth exploration of these applications has only become possible after the establishment of reverse genetics techniques to rescue recombinant viruses from plasmids encoding their complete genomes as cDNA(2-5). Viral cDNA can be conveniently modified in vitro by using standard cloning procedures to alter the genotype of the virus and/or to include new transcriptional units. Rescue of such genetically modified viruses provides a valuable tool to understand factors affecting multiple stages of infection, as well as allows for the development and improvement of vectors for the expression and delivery of antigens for vaccination and therapy. Here we describe a protocol for the rescue of recombinant NDVs.

Synergistic induction of interferon α through TLR-3 and TLR-9 agonists identifies CD21 as interferon α receptor for the B cell response

Maternal antibodies inhibit seroconversion and the generation of measles virus (MeV)-specific antibodies (both neutralizing and non-neutralizing antibodies) after vaccination whereas T cell responses are usually unaffected. The lack of seroconversion leaves individuals susceptible to vaccine-preventable infections. Inhibition of antibody secretion is due to the inhibition of B cells through a cross-link of the B cell receptor with the inhibitory FcγIIB receptor (CD32) by maternal antibody/vaccine complexes. Here, we demonstrate that a combination of TLR-3 and TLR-9 agonists induces synergistically higher levels of type I interferon in vitro and in vivo than either agonist alone. The synergistic action of TLR-3 and TLR-9 agonists is based on a feedback loop through the interferon receptor. Finally, we have identified CD21 as a potential receptor for interferon α on B cells which contributes to interferon α-mediated activation of B cells in the presence of maternal antibodies. The combination leads to complete restoration of B cell and antibody responses after immunization in the presence of inhibitory MeV-specific IgG. The strong stimulatory action of type I interferon is due to the fact that type I interferon uses not only the interferon receptor but also CD21 as a functional receptor for B cell activation.

Maternal antibodies provide protection against infection with pathogens early in life but also interfere with vaccination. This interference is caused by a vaccine/maternal antibody complex which links the B cell receptor to the inhibitory CD32 molecule. Here, we show that this cross-link results in impaired B cell activation and proliferation which is correlated with diminished antibody responses. We also found that induction of large amounts of type I interferon restores the neutralizing antibody response in the presence of maternal antibodies. The best induction of type I interferon was accomplished by a combination of known activators of interferon secretion (a combination of TLR-3 and TLR-9 agonists). The strong stimulation by interferon is due to the previously unappreciated role of CD21 as functional receptor for interferon alpha. Our findings demonstrate that the dual receptor usage of type I interferon receptor and CD21 is crucial for B cell activation in the presence of maternal antibodies. This study suggests that measles vaccine, and potentially other vaccines, may induce optimal antibody responses when they are reconstituted with TLR-3 and TLR-9 agonists and thus these agonists may have great potential for clinical use.

Oncolytic Newcastle disease virus for cancer therapy: old challenges and new directions

Newcastle disease virus (NDV) is an avian paramyxovirus, which has been demonstrated to possess significant oncolytic activity against mammalian cancers. This review summarizes the research leading to the elucidation of the mechanisms of NDV-mediated oncolysis, as well as the development of novel oncolytic agents through the use of genetic engineering. Clinical trials utilizing NDV strains and NDV-based autologous tumor cell vaccines will expand our knowledge of these novel anticancer strategies and will ultimately result in the successful use of the virus in the clinical setting.

Newcastle disease virus expressing human immunodeficiency virus type 1 envelope glycoprotein induces strong mucosal and serum antibody responses in Guinea pigs

Human immunodeficiency virus type 1 (HIV-1) is transmitted mainly through mucosal sites. Optimum strategies to elicit both systemic and mucosal immunity are critical for the development of vaccines against HIV-1. We therefore sought to evaluate the induction of systemic and mucosal immune responses by the use of Newcastle disease virus (NDV) as a vaccine vector. We generated a recombinant NDV, designated rLaSota/gp160, expressing the gp160 envelope (Env) protein of HIV-1 from an added gene. The gp160 protein expressed by rLaSota/gp160 virus was detected on an infected cell surface and was incorporated into the NDV virion. Biochemical studies showed that gp160 present in infected cells and in the virion formed a higher-order oligomer that retained recognition by conformationally sensitive monoclonal antibodies. Expression of gp160 did not increase the virulence of recombinant NDV (rNDV) strain LaSota. Guinea pigs were administered rLaSota/gp160 via the intranasal (i.n.) or intramuscular (i.m.) route in different prime-boost combinations. Systemic and mucosal antibody responses specific to the HIV-1 envelope protein were assessed in serum and vaginal washes, respectively. Two or three immunizations via the i.n. or i.m. route induced a more potent systemic and mucosal immune response than a single immunization by either route. Priming by the i.n. route was more immunogenic than by the i.m. route, and the same was true for the boosts. Furthermore, immunization with rLaSota/gp160 by any route or combination of routes induced a Th1-type response, as reflected by the induction of stronger antigen-specific IgG2a than IgG1 antibody responses. Additionally, i.n. immunization elicited a stronger neutralizing serum antibody response to laboratory-adapted HIV-1 strain MN.3. These data illustrate that it is feasible to use NDV as a vaccine vector to elicit potent humoral and mucosal responses to the HIV-1 envelope protein.