Biology subjects

Garcia-Nicolas, O.

Publications and source records attributed to Garcia-Nicolas, O..

5 recordsLinked to original sources

bioRxiv2025

An RNA replicon vaccine encoding HA and NA prevents shedding of antigen-drifted 2009 pandemic H1N1 influenza virus in the pig model

Seasonal influenza viruses escape the human immune response by antigenic drift, i.e. the positive selection of point mutations that prevent the binding of inhibitory antibodies to the influenza antigens HA and NA. The efficacy of seasonal influenza vaccines can be less than 50% if the selected influenza vaccine strain does not match the antigenic characteristics of the circulating seasonal influenza virus. In this study, we used the porcine model to evaluate the efficacy of an RNA replicon vaccine encoding the HA and NA antigens of A/Hamburg/4/2009 (H1N1) (H1N1HH4/09) in inducing cross-reactive immunity. We found that a single intramuscular immunization with this vaccine elicited high levels of antibodies with H1N1HH4/09-neutralizing activity and potent N1-sialidase inhibition. A second immunization with the same H1/N1 RNA replicon particles or with a live-attenuated influenza vaccine (LAIV) based on a modified H1N1HH4/09 virus boosted the inhibitory activity of the immune sera against the antigen-drifted A/Victoria/2570/2019 (H1N1) (H1N1Vic/19) strain. Interestingly, vaccination elicited N1-specific antibodies that also inhibited the activity of avian N1 sialidase and potently inhibited the replication of A/cattle/Texas/063224-24-1/2024 (H5N1) (H5N1Tex/24) in vitro. When challenged nasally with a H1N1HH4/09 /H1N1Vic/19 6:2 reassortant virus encoding the HA and NA antigens of H1N1Vic/19, immunized pigs did not shed infectious virus while the control animals did, suggesting that homologous prime/boost vaccination with H1/N1 replicon particles can block virus replication in the upper respiratory tract as efficiently as the heterologous RNA replicon prime/LAIV boost immunization regimen. In conclusion, RNA replicons encoding both HA and NA either used alone or in combination with LAIV mediate protection against antigen-drifted influenza viruses and reduce the risk of vaccination breakthroughs due to antigen mismatch. Furthermore, this vaccine may also limit the infection by zoonotic H5N1 viruses.

microbiology↗

bioRxiv2025

Correlates of protection against African swine fever virus identified by a systems immunology approach

African swine fever virus (ASFV) causes a fatal hemorrhagic disease in domestic pigs and wild boars, which poses severe threats to the global pork industry. Despite the promise of live attenuated vaccines (LAVs), their narrow margin between efficacy and residual virulence presents major safety challenges. This study bridges a critical knowledge gap in ASF vaccinology by identifying innate and adaptive correlates of protection. This was achieved by using an established model with two groups of pigs differing in baseline immunological status (farm and specific pathogen-free [SPF]). The animals were immunized with an attenuated ASFV strain and subsequently challenged with a related, highly virulent genotype II strain. By applying a systems immunology approach, we correlated kinetic data, including serum cytokines, blood transcription modules (BTMs), T-cell responses, and antibody levels, with clinical outcomes to track protective and detrimental immune responses to the virus over time. Key innate correlates of protection included early and sustained IFN- response, activation of antigen presentation BTMs, and controlled IL-8 levels during immunization. Lower baseline immune activation observed in SPF pigs in steady state was linked to increased protection. Adaptive correlates encompassed cell cycle, plasma cell, and T-cell BTM responses lasting until day 15 post-immunization. Consequently, an effective response from ASFV-specific Th cells prior to challenge indicated protection. After the challenge, an early IFN- response, along with low levels of pro-inflammatory cytokines and a strong induction of memory Th and Tc cells, correlated with improved clinical outcomes. The model highlights the critical role of host-specific factors in vaccine efficacy and provides a valuable framework for optimizing ASFV vaccine design while distinguishing between protective and detrimental immune responses.

immunology↗

bioRxiv2024

Intramuscular prime/intranasal boost vaccination to induce sterilizing immunity against influenza A virus infection

The most commonly used influenza vaccines are made from inactivated viruses and are administered via the intramuscular route. Although these vaccines can protect from severe lower respiratory tract disease, they do not completely prevent virus replication in the upper respiratory tract, and this may lead to virus excretion and dissemination. Therefore, nasally administered live-attenuated influenza vaccines (LAIV) that induce mucosal immunity have been developed, but finding an optimal balance between sufficient attenuation and immunogenicity remained challenging. These problems apply to both human and swine influenza vaccines. We have recently developed an LAIV candidate based on the 2009 pandemic H1N1 virus which encodes a truncated NS1 protein and lacks PA-X protein expression (NS1(1-126)-{Delta}PAX). This virus showed a blunted replication and elicited a strong innate immune response. In the present study, we took advantage of the pig animal model to evaluate this vaccine candidate in vivo and to identify a strategy for its improvement. Nasal infection of pigs with the NS1(1-126)-{Delta}PAX LAIV candidate did not cause disease but was associated with prolonged virus shedding from the upper respiratory tract. To increase safety of the vaccine candidate, we developed a novel prime/boost vaccination strategy consisting of a haemagglutinin-encoding propagation-defective vesicular stomatitis virus replicon vaccine for primary immunization via the intramuscular route, and the NS1(1-126)-{Delta}PAX LAIV for secondary immunization via the nasal route. This immunization strategy significantly reduced LAIV shedding, increased the production of specific serum IgG, neutralizing antibodies, Th1 memory cells, and induced virus-specific mucosal IgG and IgA. Of particular note, the immune response induced by this vaccination strategy completely blocked replication of the homologous challenge virus in the respiratory tract, indicating that sterilizing immunity was achieved. In summary, our novel intramuscular prime/intranasal boost vaccine combines the features of high efficacy and safety which are urgently needed to combat influenza epidemics and pandemics. Author summaryInactivated influenza vaccines which are administered intramuscularly are safe but offer only limited protection. In addition, they do not adequately prevent virus transmission by infected individuals. On the other hand, nasally administered live-attenuated influenza vaccines induce a mucosal immune response, which can effectively prevent primary infection and virus excretion. However, live-attenuated vaccines might not be sufficiently immunogenic if they are too attenuated or they trigger a robust immune response but are still too virulent. To overcome this challenge, we have developed a novel prime/boost vaccination strategy consisting of an initial intramuscular immunization with a propagation-defective RNA virus vector and a subsequent nasal immunization with a modified influenza virus that has lost its ability to counteract the hosts innate immune response. Using the pig model, we demonstrate that this approach elicited a more robust immune response both systemically and at mucosal surfaces. Importantly, replication of the vaccine virus in the respiratory tract was reduced, and challenge virus remained undetectable. In summary, our innovative vaccine, which combines intramuscular and intranasal routes of application, demonstrates high efficacy and safety and represents a valuable tool to control influenza epidemics and pandemics.

immunology↗

bioRxiv2024

Fitness adaptations of Japanese encephalitis virus in pigs following vector-free serial passaging

Japanese encephalitis virus (JEV) is a zoonotic mosquito-transmitted Flavivirus circulating in birds and pigs. In humans, JEV can cause severe viral encephalitis with high mortality. Considering that vector-free direct virus transmission was observed in pigs, JEV introduction into an immunologically naive pig population could result in a series of direct transmissions disrupting the alternating host cycling between vertebrates and mosquitoes. To assess the potential consequences of such a realistic scenario, we passaged JEV ten times in pigs. This resulted in higher in vivo viral replication, increased shedding, and stronger innate immune responses in pigs. Nevertheless, the viral tissue tropism remained similar and frequency of direct transmission was not enhanced. Next generation sequencing showed single nucleotide deviations in 10% of the genome during passaging. In total, 25 point mutations were selected to reach a frequency of at least 35% in one of the passages. From these, six mutations resulted in amino acid changes located in the precursor of membrane, the envelope, the non-structural 3 and the non-structural 5 proteins. In a competition experiment with two lines of passaging, the mutation M374L in the envelope protein and N275D in the non-structural protein 5 showed a fitness advantage in pigs. Altogether, the interruption of the alternating host cycle of JEV caused a prominent selection of viral quasispecies as well as selection of de novo mutations associated with fitness gains in pigs, albeit without enhancing direct transmission frequency. Author summaryJapanese encephalitis virus (JEV) represents a major health threat in parts of Asia and Oceania. Primary vertebrate hosts are birds and pigs, but human infection also occurs and can cause severe encephalitis with high mortality. Like other Flaviviruses transmitted by insect bites, JEV requires replication in alternating cycles between mosquitoes on one side and birds or pigs on the other side. However, we previously reported that direct transmissions between pigs in absence of mosquitos can occur. Considering the increased risks for such events after the spread of JEV to a new region with immunologically naive pigs, the present study was performed to understand if and how a series of direct transmissions would promote JEV adaptations to pigs and change virus-host interactions. Pigs infected with JEV passaged ten times showed enhanced clinical symptoms and stronger antiviral immune response, but luckily no increase in direct transmission was observed. Nevertheless, genomic analysis demonstrated a complete change in dominant virus variants, as well as selection of six viral amino acid changes. This indicates that interruptions of the alternating lifestyle of JEV causes a strong evolutionary pressure, which through fitness adaptations can change the viral characteristics.

microbiology↗

bioRxiv2020

No evidence for human monocyte-derived macrophage infection and antibody-mediated enhancement of SARS-CoV-2 infection

Vaccines are essential to control the spread of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and to protect the vulnerable population. However, one safety concern of vaccination is the possible development of antibody-dependent enhancement (ADE) of SARS-CoV-2 infection. The potential infection of Fc receptor bearing cells such as macrophages, would support continued virus replication and inflammatory responses, and thereby potentially worsen the clinical outcome of COVID-19. Here we demonstrate that SARS-CoV-2 and SARS-CoV-1 neither infect human monocyte-derived macrophages nor induce inflammatory cytokines in these cells, in sharp contrast to Middle East respiratory syndrome (MERS) coronavirus and the common cold human coronavirus 229E. Furthermore, serum from convalescent COVID-19 patients neither induced enhancement of SARS-CoV-2 infection nor innate immune response in human macrophages. These results support the view that ADE may not be involved in the immunopathological processes associated with COVID-19, however, more studies are necessary to understand the potential contribution of antibodies-virus complexes with other cells expressing FcR receptors.

immunology↗