Vaccines within vaccines: the use of adenovirus types 4 and 7 as influenza vaccine vectors

Immunogenicity and Protective Efficacy of Dose-Sparing Epigraph Vaccine against H3 Swine Influenza A Virus

Swine influenza A virus (IAV-S) is a highly prevalent and transmissible pathogen infecting worldwide swine populations. Our previous work has shown that the computationally derived vaccine platform, Epigraph, can induce broadly cross-reactive and durable immunity against H3 IAV-S in mice and swine. Therefore, in this study, we assess the immunogenicity and protective efficacy of the Epigraph vaccine at increasingly lower doses to determine the minimum dose required to maintain protective immunity against three genetically divergent H3 IAV-S. We assessed both antibody and T cell responses and then challenged with three H3N2 IAV-S derived from either Cluster IV(A), Cluster I, or the 2010.1 "human-like" cluster and assessed protection through reduced pathology, reduced viral load in the lungs, and reduced viral shedding from nasal swabs. Overall, we observed a dose-dependent effect where the highest dose of Epigraph protected against all three challenges, the middle dose of Epigraph protected against more genetically similar IAV-S, and the lowest dose of Epigraph only protected against genetically similar IAV-S. The results of these studies can be used to continue developing a broadly protective and low-dose vaccine against H3 IAV-S.

Novel and efficient method for the reconstruction of adenoviruses through isothermal assembly and its potential applications

Adenovirus based vectors are useful tools for vaccine development, gene therapy, and oncolytic virotherapy. Here we describe a novel approach for the genetic engineering of any portion of the adenovirus genome and the reconstruction of either fully replication competent or defective virions. This innovative strategy is rapid, effective and suitable for the manipulation of the entire genome broadening the spectrum of potential applications for the adenovirus system. Our strategy involved insertion of restriction enzyme recognition sequences absent in the native virus into the termini of the adenovirus genome in order to facilitate recovery. These restriction enzyme sites, together with the two inverted terminal repeats and packaging sequences, were synthesized and then subcloned into the pBR322 vector. The remaining internal portion of the adenovirus genome was separated and amplified via PCR into six segments, of which groups of two were joined together by PCR and then subcloned into pBR322 plasmids. During the PCR reaction, an overlap of 30-40 bp was added to the termini of the adjacent fragments, allowing for the subsequent isothermal assembly and correct orientation of all fragments. This approach allows for the genetic modification of each genomic fragment according to the specific research goals, (e.g., deletion, substitution, addition, etc.) To recreate the entire viral genome, the four engineered fragments (each comprised of two adenovirus genomic sections) as well as the pBR322 backbone, were reassembled into a single construct utilizing an isothermal assembly reaction. Finally, the reassembled plasmid containing the entire genome was linearized and transfected into HEK293 cells to recover the complete reconstructed adenoviral vector. Using this approach, we have successfully generated two recombinant reporter adenoviruses, one of human adenovirus serotype 14 and another of serotype 55. The E3 region was replaced by the reporter genes (GFP and Luciferase) to visualize and track the recovery process. Subsequent infection of A549 cells with these reconstructed adenovirus vectors demonstrated that they were replication competent. This method shortens the viral reconstruction process because the one-step isothermal assembly requires less than 4 days, and recombinant adenovirus recovery occurs within 10 days. This new method allows for single or multiple genetic modifications within any portion of the viral genome and can be used to construct or manipulate any adenovirus whose complete genome sequence is known.

The immunological impact of adenovirus early genes on vaccine-induced responses in mice and nonhuman primates

Adenovirus (Ad) is being explored for use in the prevention and treatment of a variety of infectious diseases and cancers. Ad with a deletion in early region 3 (ΔE3) provokes a stronger immune response than Ad with deletions in early regions 1 and E3 (ΔE1/ΔE3). The ΔE1/ΔE3 Ads are more popular because they can carry a larger transgene and because of the deleted E1 (E1A and E1B), are perceived safer for clinical use. Ad with a deletion in E1B55K (ΔE1B55K) has been in phase III clinical trials for use in cancer therapy in the US and has been approved for use in head and neck tumor therapy in China, demonstrating that Ad containing E1A are safe for clinical use. We have shown previously that ΔE1B55K Ad, even while promoting lower levels of an inserted transgene, promoted similar levels of transgene-specific immune responses as a ΔE3 Ad. Products of the Ad early region 4 (E4) limit the ability of cells to mount an innate immune response. Using this knowledge, we deleted the Ad E4 open reading frames 1-4 (E4orf1-4) from the ΔE1B55K Ad. Here, we show that innate cytokine network genes are elevated in the ΔE4 Ad-infected cells beyond that of ΔE3 Ad-infected cells. Further, in immunized mice the IgG2a subclass was favored as was the IgG1 subclass in immunized nonhuman primates. Thus, Ad E4 impacts immune responses in cells, in immunized mice, and immunized nonhuman primates. These Ad may offer advantages that are beneficial for clinical use.Importance: Adenovirus (Ad) is being explored for use in the prevention and treatment of a variety of infectious diseases and cancers. Here we provide evidence in cells, mice, and nonhuman primates supporting the notion that Ad early gene-products limit specific immune responses. Ad constructed with deletions in early genes and expressing HIV envelope protein was shown to induce greater HIV-specific cellular immune responses and higher titer antibodies compared to the parental Ad with the early genes. In addition to eliciting enhanced immunity, the deleted Ad possesses more space for insertion of additional or larger transgenes needed for targeting other infectious agents or cancers.

Species D Adenoviruses as Oncolytic Viral Vectors

Oncolytic adenoviruses (Ad) have shown promising results in the therapeutic treatment of cancer. Ad type 5 (Ad5) is the most extensively utilized Ad type. However, several limitations exist to using Ad5 as an oncolytic virus, including high levels of anti-Ad5 neutralizing antibodies in the population, binding of the Ad5 hexon to blood coagulation factor X leading to liver sequestration and toxicity, and reduced expression of the primary receptor CAR on many tumors. Here, we use in vitro methods to explore the oncolytic potential of four alternative Ad types (Ad26, 28, 45, and 48) belonging to the species D Ad subgroup and developed replication-competent species D Ads expressing the human sodium iodide symporter protein (hNIS) for combination radiovirotherapy. We evaluated the species D Ad vectors transduction, replication, cytotoxicity, and gene expression in six different cancer cell lines. Species D Ads showed the greatest transduction and cytotoxic killing in the SKBR3 breast cancer cells, followed by 293, A549, and HepG2 cells, however the cytotoxicity was less than the wild type Ad5 virus. In contrast, species D Ads showed limited transduction and cytotoxicity in the Hela and SKOV3 cancer cell lines. These species D Ad vectors also successfully expressed the hNIS gene during infection leading to increased iodide uptake in multiple cancer cell lines. These results, the low seroprevalence of anti-species D antibodies, and the lack of binding to blood coagulation FX, support further exploration of species D Ads as alternative oncolytic adenoviruses against multiple types of cancer.

Oncolytic Virus with Attributes of Vesicular Stomatitis Virus and Measles Virus in Hepatobiliary and Pancreatic Cancers

Recombinant vesicular stomatitis virus (VSV)-fusion and hemagglutinin (FH) was developed by substituting the promiscuous VSV-G glycoprotein (G) gene in the backbone of VSV with genes encoding for the measles virus envelope proteins F and H. Hybrid VSV-FH exhibited a multifaceted mechanism of cancer-cell killing and improved neurotolerability over parental VSV in preclinical studies. In this study, we evaluated VSV-FH in vitro and in vivo in models of hepatobiliary and pancreatic cancers. Our results indicate that high intrahepatic doses of VSV-FH did not result in any significant toxicity and were well tolerated by transgenic mice expressing the measles virus receptor CD46. Furthermore, a single intratumoral treatment with VSV-FH yielded improved survival and complete tumor regressions in a proportion of mice in the Hep3B hepatocellular carcinoma model but not in mice xenografted with BxPC-3 pancreatic cancer cells. Our preliminary findings indicate that VSV-FH can induce potent oncolysis in hepatocellular and pancreatic cancer cell lines with concordant results in vivo in hepatocellular cancer and discordant in pancreatic cancer without the VSV-mediated toxic effects previously observed in laboratory animals. Further study of VSV-FH as an oncolytic virotherapy is warranted in hepatocellular carcinoma and pancreatic cancer to understand broader applicability and mechanisms of sensitivity and resistance.

Characterization of a Species E Adenovirus Vector as a Zika virus vaccine

The development of a safe and efficacious Zika virus (ZIKV) vaccine remains a global health priority. In our previous work, we developed an Adenovirus vectored ZIKV vaccine using a low-seroprevalent human Adenovirus type 4 (Ad4-prM-E) and compared it to an Ad5 vector (Ad5-prM-E). We found that vaccination with Ad4-prM-E leads to the development of a strong anti-ZIKV T-cell response without eliciting significant anti-ZIKV antibodies, while vaccination with Ad5-prM-E leads to the development of both anti-ZIKV antibody and T-cell responses in C57BL/6 mice. However, both vectors conferred protection against ZIKV infection in a lethal challenge model. Here we continued to characterize the T-cell biased immune response observed in Ad4 immunized mice. Vaccination of BALB/c mice resulted in immune correlates similar to C57BL/6 mice, confirming that this response is not mouse strain-specific. Vaccination with an Ad4 expressing an influenza hemagglutinin (HA) protein resulted in anti-HA T-cell responses without the development of significant anti-HA antibodies, indicating this unique response is specific to the Ad4 serotype rather than the transgene expressed. Co-administration of a UV inactivated Ad4 vector with the Ad5-prM-E vaccine led to a significant reduction in anti-ZIKV antibody development suggesting that this serotype-specific immune profile is capsid-dependent. These results highlight the serotype-specific immune profiles elicited by different Adenovirus vector types and emphasize the importance of continued characterization of these alternative Ad serotypes.

Longitudinal quantification of adenovirus neutralizing responses in Zambian mother-infant pairs: Impact of HIV-1 infection and its treatment

Vaccination offers the most cost-effective approach to limiting the adverse impact of infectious and neoplastic diseases that reduce the quality of life in sub-Saharan Africa (SSA). However, it is unclear what vaccine vectors would be most readily implementable in the setting and at what age they should be applied for maximal efficacy. Adenoviruses (Ad) and Ad-based vectors have been demonstrated to induce effective humoral and cellular immune responses in animal models and in humans. However, because immunity associated with Ad infection is lifelong, there exists a debate as to whether pre-existing immunity might decrease the efficacy of Ad vectored vaccines. In order to begin to rationally develop vaccination strategies for SSA, we have quantified neutralizing antibodies (nAb) against Ad4, Ad5, Ad7, Ad26, Ad28, Ad45 and Ad48 in 67 adult women and their infants. We are the first to define the decay kinetics of transferred maternal nAb in infants as well as the apparent initiation of de novo Ad responses. Our findings demonstrate that in Zambian adults, robust nAb responses exist against each of the Ads tested and are efficiently transferred to newborns. With few exceptions, neither the HIV-1 infection status of the mothers or the antiretroviral therapy (ART) treatment of HIV-1 disease had significant impact on maternal Ad nAb responses or their transfer to infants. However, maternal Ad nAb decays in infants to a nadir at 12 months of age such that any of the seven Ad types could function as vaccine vectors. The definition of this 'window of opportunity' provides important foundational data for rational design and implementation of Ad vectors in this setting.

Characterization of a replication-competent vector encoding DsRed based on a human adenovirus type 4 a-like strain

Human adenovirus type 4 (HAdV4) is an etiological agent of acute respiratory disease (ARD) in pediatric and adult patients. HAdV4 strains can be divided into two major genomic clusters, namely prototype (p)-like viruses and a-like viruses. Here, the complete genome sequence of HAdV4 strain GZ01, isolated from a child with ARD in southern China, is first reported and analyzed. This strain was determined to be of the 4a1 genome-type based on in silico restriction profiles. Then, a replication-competent rAd4DsRed virus, containing the HAdV4 GZ01 infectious genome and expressing the reporter molecule DsRed, was generated and characterized. Recombinant rAd4DsRed can infect AD293, hamster, and mouse cells in which DsRed protein was expressed. No changes in antigenicity and genome replication were detected for rAd4DsRed and wild-type HAdV4. Mice immunized with rAd4DsRed was elicited a marked antibody response to DsRed. A rapid method of testing neutralizing antibodies against HAdV3 and HAdV4 was also established using a mixture of rAd4DsRed and rAd3EGFP. Our results provide the foundation to develop HAdV4 vaccines, potential vector platforms for vaccine and gene therapy, and rapid methods for serological and antiviral screening.

Oral Vaccination with Replication-Competent Adenovirus in Mice Reveals Dissemination of the Viral Vaccine beyond the Gastrointestinal Tract

Since the 1970s, replication-competent human adenoviruses 4 and 7 have been used as oral vaccines to protect U.S. soldiers against the severe respiratory diseases caused by these viruses. These vaccines are thought to establish a digestive tract infection conferring protection against respiratory challenge through antibodies. The success of these vaccines makes replication-competent adenoviruses attractive candidates for use as oral vaccine vectors. However, the inability of human adenoviruses to replicate efficiently in laboratory animals has hampered the study of such vectors. Here, we used mouse adenovirus type 1 (MAV-1) in mice to study oral replication-competent adenovirus-based vaccines. We show that MAV-1 oral administration provides protection that recapitulates the protection against homologous respiratory challenge observed with adenovirus 4 and 7 vaccines. Moreover, live oral MAV-1 vaccine better protected against a respiratory challenge than inactivated vaccines. This protection was linked not only with the presence of MAV-1-specific antibodies but also with a better recruitment of effector CD8 T cells. However, unexpectedly, we found that such oral replication-competent vaccine systemically spread all over the body. Our results therefore support the use of MAV-1 to study replication-competent oral adenovirus-based vaccines but also highlight the fact that those vaccines can disseminate widely in the body.IMPORTANCE Replication-competent adenoviruses appear to be promising vectors for the development of oral vaccines in humans. However, the study and development of these vaccines suffer from the lack of any reliable animal model. In this study, mouse adenovirus type 1 was used to develop a small-animal model for oral replication-competent adenovirus vaccines. While this model reproduced in mice what is observed with human adenovirus oral vaccines, it also highlighted that oral immunization with such a replication-competent vaccine is associated with the systemic spread of the virus. This study is therefore of major importance for the future development of such vaccine platforms and their use in large human populations.

A review of 65 years of human adenovirus seroprevalence

Introduction: Human adenovirus (HAdV)-derived vectors have been used in numerous pre-clinical and clinical trials during the last 40 years. Current research in HAdV-based vaccines focuses on improving transgene immunogenicity and safety. Because pre-existing humoral immunity against HAdV types correlate with reduced vaccine efficacy and safety, many groups are exploring the development of HAdV types vectors with lower seroprevalence. However, global seroepidemiological data are incomplete. Areas covered: The goal of this review is to centralize 65 years of research on (primarily) HAdV epidemiology. After briefly addressing adenovirus biology, we chronical HAdV seroprevalence studies and highlight major milestones. Finally, we analyze data from about 50 studies with respect to HAdVs types that are currently used in the clinic, or are in the developmental pipeline. Expert opinion: Vaccination is among the most efficient tools to prevent infectious disease. HAdV-based vaccines have undeniable potential, but optimization is needed and antivector immunity remains a challenge if the same vectors are to be administrated to different populations. Here, we identify gaps in our knowledge and the need for updated worldwide epidemiological data.

Efficacy of a T Cell-Biased Adenovirus Vector as a Zika Virus Vaccine

Zika virus (ZIKV) is a major public health concern due to the risk of congenital Zika syndrome in developing fetuses and Guillain-Barre syndrome in adults. Currently, there are no approved vaccines available to protect against infection. Adenoviruses are safe and highly immunogenic vaccine vectors capable of inducing lasting humoral and cellular immune responses. Here, we developed two Adenovirus (Ad) vectored Zika virus vaccines by inserting a ZIKV prM-E gene expression cassette into human Ad types 4 (Ad4-prM-E) and 5 (Ad5-prM-E). Immune correlates indicate that Ad5-prM-E vaccination induces both an anti-ZIKV antibody and T-cell responses whereas Ad4-prM-E vaccination only induces a T-cell response. In a highly lethal challenge in an interferon α/β receptor knockout mice, 80% of Ad5 vaccinated animals and 33% of Ad4 vaccinated animals survived a lethal ZIKV challenge, whereas no animals in the sham vaccinated group survived. In an infection model utilizing immunocompetent C57BL/6 mice that were immunized and then treated with a blocking anti-IFNAR-1 antibody immediately before ZIKV challenge, 100% of Ad4-prM-E and Ad5-prM-E vaccinated mice survived. This indicates that Ad4-prM-E vaccination is protective without the development of detectable anti-ZIKV antibodies. The protection seen in these highly lethal mouse models demonstrate the efficacy of Ad vectored vaccines for use against ZIKV.

Seroprevalence of Neutralizing Antibodies to Human Adenovirus Type 4 and 7 in Healthy Populations From Southern China

Human adenoviruses type 4 (HAdV4) and 7 (HAdV7) are two major respiratory pathogens and sporadically cause outbreaks of acute respiratory diseases. The neutralizing antibody (nAb) response to these two adenoviruses in civilian populations, which is important for dissecting previous circulations and predicting potential outbreaks, remains largely unknown. In this study, we generated replication-competent HAdV4 and HAdV7 reporter viruses expressing secreted-alkaline-phosphatase (SEAP), and established neutralization assays to investigate the seroprevalence of pre-existing nAb in healthy volunteers from Hunan Province, southern China. The seropositivity rates are 58.4 and 63.8% for anti-HAdV4 nAb and anti-HAdV7 nAb, respectively. High nAb titers (> 1000) were frequently detected in HAdV4-seropositive individuals, whereas most HAdV7-seropositive volunteers had moderate nAb titers (201-1000). The seropositivity rates of anti-HAdV4 nAb and anti-HAdV7 nAb increase with age, with individuals younger than 20 exhibiting the lowest seropositivity rates. Both seropositivity rates and nAb titers are comparable between different sex groups. Notably, HAdV4-seropositive individuals tend to be HAdV7-seropositive and vice versa. Because HAdV4 antisera showed no neutralizing activity to HAdV7 whereas HAdV7 antisera cannot neutralize HAdV4, a subgroup of individuals might be susceptible to infection by HAdV4 and HAdV7 and thus generate nAb to both of them. These results revealed the continuous circulation of HAdV4 and HAdV7 and the lack of protective immunity in more than 35% of people, which emphasized the surveillance of these two HAdVs and the development of prophylactic vaccines.

Seroepidemiological investigation of HAdV-4 infection among healthy adults in China and in Sierra Leone, West Africa

An apparent increase in the frequency of human adenovirus type 4 (HAdV-4) infections among general populations has been observed over the past 10 years. However, available epidemiological data that may reflect previous viral circulation and assist in predicting potential outbreaks are sparse, particularly in mainland China and Africa. In this study, a convenient neutralization assay for use in the surveillance of historical HAdV-4 infections was established based on a recombinant luciferase-expressing virus. Subsequently, the neutralizing antibodies (nAbs) of 1013 healthy adult serum samples from China and Sierra Leone were evaluated. Our results showed that over 50% of the participants from China and nearly 70% of donors from Sierra Leone had detectable nAbs against HAdV-4 despite the few infection cases officially reported in these regions. Furthermore, the prevalence of nAbs to HAdV-4 is lower than that to HAdV-5, and both varied by geographic location. In addition, the seropositive rates of both HAdV-4 and HAdV-5 nAbs increased with age. However, the nAbs stimulated by HAdV-4 remained stable at low (≤200) levels among the different age groups, whereas moderate (201–1000) or high (>1000) nAb levels were produced by HAdV-5 and tended to decrease with age. These results elucidate the human humoral immune response against HAdV-4 and revealed that this virus may be an underestimated causative agent of respiratory disease among adults in China and West Africa, demonstrating the importance of HAdV-4 surveillance and providing useful insights for the future development of HAdV-4-based vaccines.

Replicating Single-Cycle Adenovirus Vectors Generate Amplified Influenza Vaccine Responses

Head-to-head comparisons of conventional influenza vaccines with adenovirus (Ad) gene-based vaccines demonstrated that these viral vectors can mediate more potent protection against influenza virus infection in animal models. In most cases, Ad vaccines are engineered to be replication-defective (RD-Ad) vectors. In contrast, replication-competent Ad (RC-Ad) vaccines are markedly more potent but risk causing adenovirus diseases in vaccine recipients and health care workers. To harness antigen gene replication but avoid production of infectious virions, we developed "single-cycle" adenovirus (SC-Ad) vectors. Previous work demonstrated that SC-Ads amplify transgene expression 100-fold and produce markedly stronger and more persistent immune responses than RD-Ad vectors in Syrian hamsters and rhesus macaques. To test them as potential vaccines, we engineered RD and SC versions of adenovirus serotype 6 (Ad6) to express the hemagglutinin (HA) gene from influenza A/PR/8/34 virus. We show here that it takes approximately 33 times less SC-Ad6 than RD-Ad6 to produce equal amounts of HA antigen in vitro SC-Ad produced markedly higher HA binding and hemagglutination inhibition (HAI) titers than RD-Ad in Syrian hamsters. SC-Ad-vaccinated cotton rats had markedly lower influenza titers than RD-Ad-vaccinated animals after challenge with influenza A/PR/8/34 virus. These data suggest that SC-Ads may be more potent vaccine platforms than conventional RD-Ad vectors and may have utility as "needle-free" mucosal vaccines.

IMPORTANCE

Most adenovirus vaccines that are being tested are replication-defective adenoviruses (RD-Ads). This work describes testing newer single-cycle adenovirus (SC-Ad) vectors that replicate transgenes to amplify protein production and immune responses. We show that SC-Ads generate markedly more influenza virus hemagglutinin protein and require substantially less vector to generate the same immune responses as RD-Ad vectors. SC-Ads therefore hold promise to be more potent vectors and vaccines than current RD-Ad vectors.

Unique safety issues associated with virus-vectored vaccines: Potential for and theoretical consequences of recombination with wild type virus strains

In 2003 and 2013, the World Health Organization convened informal consultations on characterization and quality aspects of vaccines based on live virus vectors. In the resulting reports, one of several issues raised for future study was the potential for recombination of virus-vectored vaccines with wild type pathogenic virus strains. This paper presents an assessment of this issue formulated by the Brighton Collaboration.

To provide an appropriate context for understanding the potential for recombination of virus-vectored vaccines, we review briefly the current status of virus-vectored vaccines, mechanisms of recombination between viruses, experience with recombination involving live attenuated vaccines in the field, and concerns raised previously in the literature regarding recombination of virus-vectored vaccines with wild type virus strains. We then present a discussion of the major variables that could influence recombination between a virus-vectored vaccine and circulating wild type virus and the consequences of such recombination, including intrinsic recombination properties of the parent virus used as a vector; sequence relatedness of vector and wild virus; virus host range, pathogenesis and transmission; replication competency of vector in target host; mechanism of vector attenuation; additional factors potentially affecting virulence; and circulation of multiple recombinant vectors in the same target population. Finally, we present some guiding principles for vector design and testing intended to anticipate and mitigate the potential for and consequences of recombination of virus-vectored vaccines with wild type pathogenic virus strains.

Efficient induction of cross-presentating human B cell by transduction with human adenovirus type 7 vector

Although human autologous B cells represent a promising alternative to dendritic cells (DCs) for easy large-scale preparation, the naive human B cells are always poor at antigen presentation. The safe and effective usage record of human adenovirus type 7 (HAdV7) live vaccines makes it attractive as a promising vaccine vector candidate. To investigate whether HAdV7 vector could be used to induce the human B cells cross-presentation, in the present study, we constructed the E3-defective recombinant HAdV7 vector encoding green fluorescent protein (GFP) and carcinoembryonic antigen (CEA). We demonstrated that naive human B cells can efficiently be transduced, and that the MAPKs/NF-κB pathway can be activated by recombinant HAdV7. We proved that cytokine TNF-α, IL-6 and IL-10, surface molecule MHC class I and the CD86, antigen-processing machinery (APM) compounds ERp57, TAP-1, and TAP-2. were upregulated in HAdV7 transduced human B cells. We also found that CEA-specific IFNγ expression, degranulation, and in vitro and ex vivo cytotoxicities are induced in autologous CD8(+) T cells presensitized by HAd7CEA modified human B cells. Meanwhile, our evidences clearly show that Toll-like receptors 9 (TLR9) antagonist IRS 869 significantly eliminated most of the HAdV7 initiated B cell activation and CD8(+) T cells response, supporting the role and contribution of TLR9 signaling in HAdV7 induced human B cell cross-presentation. Besides a better understanding of the interactions between recombinant HAdV7 and human naive B cells, to our knowledge, the present study provides the first evidence to support the use of HAdV7-modified B cells as a vehicle for vaccines and immunotherapy.

Centralized Consensus Hemagglutinin Genes Induce Protective Immunity against H1, H3 and H5 Influenza Viruses

With the exception of the live attenuated influenza vaccine there have been no substantial changes in influenza vaccine strategies since the 1940’s. Here we report an alternative vaccine approach that uses Adenovirus-vectored centralized hemagglutinin (HA) genes as vaccine antigens. Consensus H1-Con, H3-Con and H5-Con HA genes were computationally derived. Mice were immunized with Ad vaccines expressing the centralized genes individually. Groups of mice were vaccinated with 1 X 10¹⁰, 5 X 10⁷ and 1 X 10⁷ virus particles per mouse to represent high, intermediate and low doses, respectively. 100% of the mice that were vaccinated with the high dose vaccine were protected from heterologous lethal challenges within each subtype. In addition to 100% survival, there were no signs of weight loss and disease in 7 out of 8 groups of high dose vaccinated mice. Lower doses of vaccine showed a reduction of protection in a dose-dependent manner. However, even the lowest dose of vaccine provided significant levels of protection against the divergent influenza strains, especially considering the stringency of the challenge virus. In addition, we found that all doses of H5-Con vaccine were capable of providing complete protection against mortality when challenged with lethal doses of all 3 H5N1 influenza strains. This data demonstrates that centralized H1-Con, H3-Con and H5-Con genes can be effectively used to completely protect mice against many diverse strains of influenza. Therefore, we believe that these Ad-vectored centralized genes could be easily translated into new human vaccines.

Immunogenicity and efficacy in mice of an adenovirus-based bicistronic rotavirus vaccine expressing NSP4 and VP7

NSP4 and VP7 are important functional proteins of rotavirus. Proper combination of viral gene expression is favorable to improving the protection effect of subunit vaccine. In the present study, We evaluated the immunogenicity and efficacy of the bicistronic recombinant adenovirus (rAd-NSP4-VP7) and two single-gene expressing adenoviruses (rAd-NSP4, rAd-VP7). The three adenovirus vaccines were used to immunize mice by intramuscular or intranasal administration. The data showed significant increases in serum antibodies, T lymphocyte subpopulations proliferation, and cytokine secretions of splenocyte in all immunized groups. However, the serum IgA and neutralizing antibody levels of the rAd-NSP4-VP7 or rAd-VP7 groups were significantly higher than those of the rAd-NSP4, while the splenocyte numbers of IFN-γ secretion in the rAd-NSP4-VP7 or rAd-NSP4 groups was greater than that of the rAd-VP7. Furthermore, the efficacy evaluation in a suckling mice model indicated that only rAd-NSP4-VP7 conferred significant protection against rotavirus shedding challenge. These results suggest that the co-expression of NSP4 and VP7 in an adenovirus vector induce both humoral and cell-mediated immune responses efficiently, and provide potential efficacy for protection against rotavirus disease. It is possible to represent an efficacious subunits vaccine strategy for control of rotavirus infection and transmission.

CD46-mediated transduction of a species D adenovirus vaccine improves mucosal vaccine efficacy

The high levels of preexisting immunity against Adenovirus type 5 (Ad5) have deemed Ad5 unusable for translation as a human vaccine vector. Low seroprevalent alternative viral vectors may be less impacted by preexisting immunity, but they may also have significantly different phenotypes from that of Ad5. In this study we compare species D Ads (26, 28, and 48) to the species C Ad5. In vitro transduction studies show striking differences between the species C and D viruses. Most notably, Ad26 transduced human dendritic cells much more effectively than Ad5. In vivo imaging studies showed strikingly different transgene expression profiles. The Ad5 virus was superior to the species D viruses in BALB/c mice when delivered intramuscularly. However, the inverse was true when the viruses were delivered mucosally via the intranasal epithelia. Intramuscular transduction was restored in mice that ubiquitously expressed human CD46, the primary receptor for species D viruses. We analyzed both species C and D Ads for their ability to induce prophylactic immunity against influenza in the CD46 transgenic mouse model. Surprisingly, the species D vaccines again failed to induce greater levels of protective immunity as compared with the species C Ad5 when delivered intramuscularly. However, the species D Ad vaccine vector, Ad48, induced significantly greater protection as compared with Ad5 when delivered mucosally via the intranasal route in CD46 transgenic mice. These data shed light on the complexities between the species and types of Ad. Our findings indicate that more research will be required to identify the mechanisms that play a key role in the induction of protective immunity induced by species D Ad vaccines.