A cell culture-derived whole-virus H5N1 vaccine induces long-lasting cross-clade protective immunity in mice which is augmented by a homologous or heterologous booster vaccination

Preclinical immunogenicity assessment of a cell-based inactivated whole-virion H5N1 influenza vaccine

In influenza vaccine development, Madin–Darby canine kidney (MDCK) cells provide multiple advantages, including large-scale production and egg independence. Several cell-based influenza vaccines have been approved worldwide. We cultured H5N1 virus in a serum-free MDCK cell suspension. The harvested virus was manufactured into vaccines after inactivation and purification. The vaccine effectiveness was assessed in the Wuhan Institute of Biological Products BSL2 facility. The pre- and postvaccination mouse serum titers were determined using the microneutralization and hemagglutination inhibition tests. The immunological responses induced by vaccine were investigated using immunological cell classification, cytokine expression quantification, and immunoglobulin G (IgG) subtype classification. The protective effect of the vaccine in mice was evaluated using challenge test. Antibodies against H5N1 in rats lasted up to 8 months after the first dose. Compared with those of the placebo group, the serum titer of vaccinated mice increased significantly, Th1 and Th2 cells were activated, and CD8+ T cells were activated in two dose groups. Furthermore, the challenge test showed that vaccination reduced the clinical symptoms and virus titer in the lungs of mice after challenge, indicating a superior immunological response. Notably, early after vaccination, considerably increased interferon-inducible protein-10 (IP-10) levels were found, indicating improved vaccine-induced innate immunity. However, IP-10 is an adverse event marker, which is a cause for concern. Overall, in the case of an outbreak, the whole-virion H5N1 vaccine should provide protection.

Influenza virus-like particles composed of conserved influenza proteins and GPI-anchored CCL28/GM-CSF fusion proteins enhance protective immunity against homologous and heterologous viruses

Influenza viruses cause significant morbidity and mortality and pose a substantial threat to public health. Vaccination represents the principle means of preventing influenza virus infection. Current vaccine approaches are hindered by the need to routinely reformulate vaccine compositions in an effort to account for the progressive antigenic changes that occur as influenza viruses circulate in the human population. In this study, we evaluated chimeric virus-like particle (cVLP) vaccines containing conserved elements of influenza proteins (HL5M2e (HA stem gene with 5M2e gene inserted) and NP), with or without glycosylphosphatidylinositol-anchored CCL28 (GPI-CCL28) and/or GM-CSF (GPI-GM-CSF) fusion proteins as molecular adjuvants. cVLPs elicited strong humoral and cellular immune responses against homologous and heterologous viruses, and improved survival following lethal challenge with both homologous and heterologous viruses. Inclusion of GPI-anchored adjuvants in cVLP vaccines augmented the generation of influenza-specific humoral and cellular immune responses in mice in comparison to the non-adjuvanted cVLP vaccines. VLPs containing GPI-anchored adjuvants reduced morbidity and improved survival to lethal challenge with homologous and heterologous influenza viruses. This work suggests that VLP vaccines incorporating conserved influenza virus proteins and GPI-anchored molecular adjuvants may serve as a platform for a broadly protective "universal" influenza vaccine.

H5N1 influenza virus-like particle vaccine protects mice from heterologous virus challenge better than whole inactivated virus

The highly pathogenic avian influenza (HPAI) H5N1 virus has become highly enzootic since 2003 and has dynamically evolved to undergo substantial evolution. Clades 2.3.2.1 and 2.3.4 have become the most dominant lineage in recent years, and H5N8 avian influenza outbreaks have been reported Asia. The current approach to generate influenza virus vaccines uses embryonated chicken eggs for large-scale production, although such vaccines have been poorly immunogenic to heterologous virus challenge. In the current study, virus-like particles (VLP) based on A/meerkat/Shanghai/SH-1/2012 (clade 2.3.2.1) and comprising hemagglutinin (HA), neuraminidase (NA), and matrix (M1) were produced using a baculovirus expression system to develop effective protection for different H5 HPAI clade challenges. Mice immunized with VLP demonstrated stronger humoral and cellular immune responses than mice immunized with whole influenza virus (WIV), with 20-fold higher IgG antibody titers against A/meerkat/Shanghai/SH-1/2012 after boost. Notably, the WIV vaccine group showed partial protection (80% survival) to homologous challenge, little protection (40% survival) to heterologous challenge, and 20% survival to H5N8 challenge, whereas all mice in the VLP+CFA group survived. These results provide insight for the development of effective prophylactic vaccines based on VLPs with cross-clade protection for the control of current H5 HPAI outbreaks in humans.

Longevity of Sm-p80-specific antibody responses following vaccination with Sm-p80 vaccine in mice and baboons and transplacental transfer of Sm-p80-specific antibodies in a baboon

Based on data obtained using vaccine efficacy studies in mice, hamsters, and baboons, the credentials of Sm-p80 as a first tier vaccine candidate for schistosomiasis have been well established. Sm-p80-based vaccine formulation(s) have consistently exhibited potent prophylactic efficacy in reducing adult worm burden following cercarial challenge and induce killing of established adult worms in chronic infection. This vaccine is protective against both intestinal and urinary schistosomiasis. In this study, the longevity of Sm-p80-specific antibody responses was studied in mice and in baboons. Robust antibody titers were detected in mice for up to 60 weeks following vaccination with Sm-p80 recombinant vaccine (Sm-p80 + GLA-SE). In the follow-up experiments to our published studies, Sm-p80-specific IgG was also detected in baboons 5-8 years following the initial vaccination with an Sm-p80 DNA vaccine. In one baboon, transfer of Sm-p80-specific antibody was detected in umbilical cord blood and in the baby. These long-lasting humoral immune response data coupled with the vaccine efficacy data in rodents and nonhuman primates further strengthens the case for Sm-p80 to be moved forward through development leading to human clinical trials.

Vero cell culture-derived pandemic influenza vaccines: preclinical and clinical development

Several subtypes of influenza A viruses with pandemic potential are endemic in bird populations throughout Asia, Africa and the Middle East, and evidence suggests that these viruses are adapting to the mammalian host. As emphasized by the high mortality rate of humans infected with H5N1 viruses, this situation presents a substantial risk to global human health. The Vero cell culture platform has been used to develop whole-virus influenza vaccines that provide broad cross-clade protection against viruses with pandemic potential, at low antigen doses, without the requirement for adjuvantation. The safety and immunogenicity of these vaccines has been demonstrated in studies with more than 10,000 individuals, including healthy adult and elderly subjects, children and various risk groups. These Vero cell-derived vaccines are licensed for prepandemic and pandemic use. The Vero platform is also being explored to develop next-generation live-attenuated and recombinant vaccines.