Protective Immunity and Safety of a Genetically Modified Influenza Virus Vaccine

Abstract

Recombinant influenza viruses are promising viral platforms to be used as antigen delivery vectors. To this aim, one of the most promising approaches consists of generating recombinant viruses harboring partially truncated neuraminidase (NA) segments. To date, all studies have pointed to safety and usefulness of this viral platform. However, some aspects of the inflammatory and immune responses triggered by those recombinant viruses and their safety to immunocompromised hosts remained to be elucidated. In the present study, we generated a recombinant influenza virus harboring a truncated NA segment (vNA-Δ) and evaluated the innate and inflammatory responses and the safety of this recombinant virus in wild type or knock-out (KO) mice with impaired innate (Myd88 -/-) or acquired (RAG -/-) immune responses. Infection using truncated neuraminidase influenza virus was harmless regarding lung and systemic inflammatory response in wild type mice and was highly attenuated in KO mice. We also demonstrated that vNA-Δ infection does not induce unbalanced cytokine production that strongly contributes to lung damage in infected mice. In addition, the recombinant influenza virus was able to trigger both local and systemic virus-specific humoral and CD8+ T cellular immune responses which protected immunized mice against the challenge with a lethal dose of homologous A/PR8/34 influenza virus. Taken together, our findings suggest and reinforce the safety of using NA deleted influenza viruses as antigen delivery vectors against human or veterinary pathogens.

Influenza A Virus as a Predisposing Factor for Cryptococcosis

“…Our previous study showed that the IAV load in lungs peaked at about the fourth day after infection and that IAV was cleared by day 10 (Barbosa et al, 2014 ). Therefore, our data strongly suggested a link between high viral replication and increased susceptibility to Cg during acute influenza infections.…”

“…Our preliminary findings showed that a deleterious effect of co-infection was evident only in mice exposed to IAV 3 days before inoculation with Cg. Notably, day 3 of IAV infection coincides with high levels of virus in infected lungs (Ayala et al, 2011 ; Pan et al, 2013 ; Barbosa et al, 2014 ). The importance of active viral multiplication in this predisposition to severe pulmonary cryptococcal disease was demonstrated by treatment with the antiviral oseltamivir, which delayed mortality of mice co-infected.…”

“…Madin-Darby Canine Kidney (MDCK) cells were maintained at 37°C and 5% CO 2 in complete Dulbecco's modified Eagle Medium (DMEM; SIGMA). Virus stocks of the mouse-adapted influenza A/PR8/34 (H1N1) virus were prepared and titrated on MDCK cells as previously described (Barbosa et al, 2014 ). C. gattii (Cg) VGII, strain L27/01 (UFMG-CM-Y6141) was cultured on Sabouraud's Dextrose Agar (SDA) by 48 h at 37°C (Santos et al, 2014 ).…”

“…They were then inoculated intranasally (i.n.) with 20 μL of 1 × 10 3 plaque-forming units (PFU)/animal of IAV diluted in PBS (0.1 LD 50 ) or mock infected with PBS (Barbosa et al, 2014 ) and/or inoculated intratracheally (i.t.) with 30 μL of 1 × 10 4 colony-forming units (CFU)/animal of Cg or PBS (controls) (Ferreira et al, 2015 ).…”

Developing accurate models of the human airways

“…Intranasal delivery of a peptide vaccine for the major cause of respiratory disease in young children, the respiratory syncytial virus, has shown promise in animal models, but these have yet to be tested in humans [47]. Similarly, intranasal immunisation of mice with genetically modified, recombinant influenza virus was shown to drive protective humoral and cellular antiviral immune responses and was effective even in immunocompromised host animals [48]. Pulmonary delivery has proved more successful for human disease control for measles, although here the immune responses are dependent on the formulation, with dry powder eliciting lower immunity than intramuscular injections (in an animal model) and the age of the population, since clinical trials using nebulised liquid vaccine was shown to be less effective in younger children [49]…”