A high infectious simian adenovirus type 23 vector based vaccine efficiently protects common marmosets against Zika virus infection

Marmosets as models of infectious diseases

Animal models of infectious disease often serve a crucial purpose in obtaining licensure of therapeutics and medical countermeasures, particularly in situations where human trials are not feasible, i.e., for those diseases that occur infrequently in the human population. The common marmoset (Callithrix jacchus), a Neotropical new-world (platyrrhines) non-human primate, has gained increasing attention as an animal model for a number of diseases given its small size, availability and evolutionary proximity to humans. This review aims to (i) discuss the pros and cons of the common marmoset as an animal model by providing a brief snapshot of how marmosets are currently utilized in biomedical research, (ii) summarize and evaluate relevant aspects of the marmoset immune system to the study of infectious diseases, (iii) provide a historical backdrop, outlining the significance of infectious diseases and the importance of developing reliable animal models to test novel therapeutics, and (iv) provide a summary of infectious diseases for which a marmoset model exists, followed by an in-depth discussion of the marmoset models of two studied bacterial infectious diseases (tularemia and melioidosis) and one viral infectious disease (viral hepatitis C).

Adenoviruses vectored hepatitis C virus vaccine cocktails induce broadly specific immune responses against multi-genotypic HCV in mice

BACKGROUND

Hepatitis C virus (HCV) vaccines are an urgent need to prevent hepatitis C and its further progression of hepatocellular carcinoma. Since the promising T cell based chimpanzee adenovirus and modified vaccinia virus Ankara vectorial HCV vaccines were failed in clinical phase II trial, the vaccine designs to improve protection efficacy in combination of cellular and humoral immunity have been hypothesized against multi-genotypic HCV.

METHODS

Eight HCV vaccine strains were constructed with two novel adenovirus vectors (Sad23L and Ad49L) encoding E1E2 or NS3-5B proteins of HCV genotype (Gt) 1b and 6a isolates, covering 80 % HCV strains prevalent in south China and south-east Asia. Eight HCV vaccine strains were grouped into Sad23L-based vaccine cocktail-1 and Ad49L-based vaccine cocktail-2 for vaccinating mice, respectively.

RESULTS

The immunogenicity of a single dose of 107-1010 PFU HCV individual vaccines was evaluated in mice, showing weak specific antibody to E1 and E2 protein but a dose-dependent T cell response to E1E2/NS3-5B peptides, which could be significantly enhanced by boosting with an alternative vector vaccine carrying homologous antigen. Prime-boost vaccinations with vaccine cocktail-1 and cocktail-2 induced significantly higher cross-reactive antibody and stronger T cell responses to HCV Gt-1b/6a. The high frequency of intrasplenic and intrahepatic NS31629-1637 CD8+ T cell responses were identified, in which the high proportion of TRM and TEM cells might play an important role against HCV infection in liver.

CONCLUSIONS

Prime-boost regimens with HCV vaccine cocktails elicited the broad cross-reactive antibody and robust T cell responses against multi-genotypic HCV in mice.

Characterization of Pre-Existing Neutralizing Antibody to Human Adenovirus Types 5 and 49 and Simian Type 23 in Chinese Population

Recombinant adenovirus vector has been widely used in vaccine development. Due to the pre-existing immunity of human adenovirus type 5 (HAd5) in humans, a range of rare human and chimpanzee adenovirus vectors have been developed. In the previous study, we constructed novel adenovirus vector Sad23L and Ad49L based on simian adenovirus type 23 (SAd23) and human adenovirus type 49 (HAd49), which were used in the development of ZIKV and COVID-19 vaccines. However, the levels of pre-existing neutralizing antibody (NAb) of HAd49 and SAd23 remain unclear in China. In this study, we measured NAbs titers of HAd5, HAd49, and SAd23 in 600 healthy blood donors from 6 regions across China. NAb titer of HAd49 or SAd23 was significantly lower than that of HAd5 (p < 0.001). There was no significant difference in seroprevalence and NAb titers of three adenoviruses between male and female donors. The seropositive rates of HAd5 and SAd23 increased with age growth in a positive correlation (p < 0.01), while in contrast to HAd5, HAd49, and SAd23 had a low level of pre-existing immunity in Chinese population, which suggested that Ad49L and Sad23L vectors could be used in vaccine development for humans.

Two Novel Adenovirus Vectors Mediated Differential Antibody Responses via Interferon-α and Natural Killer Cells

Recombinant adenovirus vectors have been widely used in vaccine development. To overcome the preexisting immunity of human adenovirus type 5 (Ad5) in populations, a range of chimpanzee or rare human adenovirus vectors have been generated. However, these novel adenovirus vectors mediate the diverse immune responses in the hosts. In this study, we explored the immune mechanism of differential antibody responses to SARS-CoV-2 S protein in mice immunized by our previously developed two novel simian adenovirus type 23 (Sad23L) and human adenovirus type 49 (Ad49L), and Ad5 vectored COVID-19 vaccines. Sad23L-nCoV-S and Ad5-nCoV-S vaccines induced the low level of interferon-α (IFN-α) and the high level of antigen-specific antibody responses in wild-type and IFN-α/β receptor defective (IFNAR-/-) C57 mice, while Ad49L-nCoV-S vaccine induced the high IFN-α and low antibody responses in C57 mice but the high antibody response in IFNAR-/- mice. In addition, the high antibody response was detected in natural killer (NK) cells-blocked but the low in follicular helper T (TFH) cells -blocked C57 mice immunized with Ad49L-nCoV-S vaccine. These results showed that Ad49L vectored vaccine stimulated IFN-α secretion to activate NK cells, and then reduced the number of TFH cells, generation center (GC) B cells and plasma cells, and subsequently reduced antigen-specific antibody production. The different novel adenovirus vectors could be selected for vaccine development according to the need for either humoral or cellular or both immune protections against a particular disease. IMPORTANCE Novel adenovirus vectors are an important antigen delivery platform for vaccine development. Understanding the immune diversity between different adenoviral vectors is critical to design the proper vaccine against an aim disease. In this study, we described the immune mechanism of Sad23L and Ad49L vectored vaccines for raising the equally high specific T cell response but the different level of specific antibody responses in mice. We found that Ad49L-vectored vaccine initiated the high IFN-α and activated NK cells to inhibit antibody response via downregulating the number of CD4+ TFH cells leading to the decline of GC B cells and plasma cells.

Vaccination of cats with Sad23L-nCoV-S vaccine candidate against major variants of SARS-CoV-2

Cats are susceptible to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and risk transmitting viruses to naive cats or humans. Here, based on our novel adenovirus-vectored COVID-19 vaccine, the immunogenicity of Sad23L-nCoV-S vaccine was evaluated in cats by prime-boost vaccinations. Five cats were primed with a dose of 10⁸ plaque-forming units (PFUs) Sad23L-nCoV-S vaccine and then boosted with an equal dose of same vaccine at a 4-week interval. Cat serum neutralizing antibody (NAb) titers (the sample dilution at which 50% inhibitory concentration [IC₅₀]) were measured as IC₅₀ 15,849 to wild-type strain, IC₅₀ 6,591 to Alpha, IC₅₀ 2,315 to Beta, IC₅₀ 2,744 to Gamma, IC₅₀ 1,848 to Delta, and IC₅₀ 318 to Omicron variants of pseudotyped SARS-CoV-2 viruses at week 6 post-prime vaccination. All NAb levels to these five variants were ≥IC₅₀ 49 from vaccinated cats at week 10, while 48.8% to Delta and 100% to Omicron variants were <IC₅₀ 10 from human vaccinees at week 2 or 4 after receiving two injections of the inactivated SARS-CoV-2 vaccines. Robust T cell response of interferon (IFN)-γ to S peptides were detected in vaccinated cats. It was concluded that Sad23L-nCoV-S vaccine could be a promising vaccine candidate against SARS-CoV-2 infection in cats by prime or plus boost vaccinations.

A nanoenzyme linked immunochromatographic sensor for rapid and quantitative detection of SARS-CoV-2 nucleocapsid protein in human blood

The establishment of a simple, low-cost, high-sensitive and rapid immunoassay for detecting SARS-CoV-2 antigen in human blood is an effective mean of discovering early SARS-CoV-2 infection and controlling the pandemic of COVID-19. Herein, a smartphone based nanozyme linked immunochromatographic sensor (NLICS) for the detection of SARS-CoV-2 nucleocapsid protein (NP) has been developed on demand. The system is integrated by disposable immunochromatography assay (ICA) and optical sensor devices. Immunoreaction and enzyme-catalyzed substrate color reaction were carried out on the chromatographic strip in a device, of which the light signal was read by a photometer through a biosensor channel, and the data was synchronously transmitted via the Bluetooth to the app in-stored smartphone for reporting the result. With a limit of detection (LOD) of 0.026 ng/mL NP, NLICS had the linear detection range (LDR) between 0.05 and 1.6 ng/mL NP, which was more sensitive than conventional ICA. NLICS took 25 min for reporting results. For detection of NP antigen in clinical serum samples from 21 COVID-19 patients and 80 healthy blood donor controls, NLICS and commercial enzyme linked immunosorbent assay (ELISA) had 76.2% or 47.6% positivity, and 100% specificity, respectively (P = 0.057), while a good correlation coefficient (r = 0.99) for quantification of NP between two assays was obtained. In conclusion, the NLICS was a rapid, simple, cheap, sensitive and specific immunochromatographic sensing assay for early diagnosis of SARS-CoV-2 infection.

A Self-Biomineralized Novel Adenovirus Vectored COVID-19 Vaccine for Boosting Immunization of Mice

SARS-CoV-2 has caused more than 3.8 million deaths worldwide, and several types of COVID-19 vaccines are urgently approved for use, including adenovirus vectored vaccines. However, the thermal instability and pre-existing immunity have limited its wide applications. To circumvent these obstacles, we constructed a self-biomineralized adenovirus vectored COVID-19 vaccine (Sad23L-nCoV-S-CaP) by generating a calcium phosphate mineral exterior (CaP) based on Sad23L vector carrying the full-length gene of SARS-CoV-2 spike protein (S) under physiological condition. This Sad23L-nCoV-S-CaP vaccine was examined for its characteristics of structure, thermostability, immunogenicity and avoiding the problem of preexisting immunity. In thermostability test, Sad23L-nCoV-S-CaP could be stored at 4 °C for over 45 days, 26 °C for more than 8 days and 37 °C for approximately 2 days. Furthermore, Sad23L-nCoV-S-CaP induced higher level of S-specific antibody and T cell responses, and was not affected by the pre-existing anti-Sad23L immunity, suggesting it could be used as boosting immunization on Sad23L-nCoV-S priming vaccination. The boosting with Sad23L-nCoV-S-CaP vaccine induced high titers of 10^5.01 anti-S1, 10^4.77 anti-S2 binding antibody, 10^3.04 pseudovirus neutralizing antibody (IC₅₀), and robust T-cell response of IFN-γ (1466.16 SFCs/10⁶ cells) to S peptides, respectively. In summary, the self-biomineralization of the COVID-19 vaccine Sad23L-nCoV-S-CaP improved vaccine efficacy, which could be used in prime-boost regimen for prevention of SARS-CoV-2 infection in humans.

Prime-boost vaccination of mice and rhesus macaques with two novel adenovirus vectored COVID-19 vaccine candidates

ABSTRACTCOVID-19 vaccines are being developed urgently worldwide. Here, we constructed two adenovirus vectored COVID-19 vaccine candidates of Sad23L-nCoV-S and Ad49L-nCoV-S carrying the full-length gene of SARS-CoV-2 spike protein. The immunogenicity of two vaccines was individually evaluated in mice. Specific immune responses were observed by priming in a dose-dependent manner, and stronger responses were obtained by boosting. Furthermore, five rhesus macaques were primed with 5 × 10⁹ PFU Sad23L-nCoV-S, followed by boosting with 5 × 10⁹ PFU Ad49L-nCoV-S at 4-week interval. Both mice and macaques well tolerated the vaccine inoculations without detectable clinical or pathologic changes. In macaques, prime-boost regimen induced high titers of 10^3.16 anti-S, 10^2.75 anti-RBD binding antibody and 10^2.38 pseudovirus neutralizing antibody (pNAb) at 2 months, while pNAb decreased gradually to 10^1.45 at 7 months post-priming. Robust T-cell response of IFN-γ (712.6 SFCs/10⁶ cells), IL-2 (334 SFCs/10⁶ cells) and intracellular IFN-γ in CD4⁺/CD8⁺ T cell (0.39%/0.55%) to S peptides were detected in vaccinated macaques. It was concluded that prime-boost immunization with Sad23L-nCoV-S and Ad49L-nCoV-S can safely elicit strong immunity in animals in preparation of clinical phase 1/2 trials.