A 2-month field cohort study of SARS-CoV-2 in saliva of BNT162b2 vaccinated nursing home workers

peer reviewe

Développement et caractérisation d’un modèle murin de vaccins oraux par adénovirus réplicatifs

Oral vaccination offers many immunological and practical advantages. Nontheless immunize by per os administration necessitates to overcome oral tolerance mechanisms. Viral vectors, such as adenoviruses (AdVs) that potentially combine an efficient delivery system to a powerfull adjuvant effect could be an interesting approach in that regard. Since the 1970s, replication-competent human AdVs 4 and 7 have been used as oral vaccines to protect US soldiers against the severe respiratory diseases caused by these viruses. Though this succesfull application make replication-competent AdVs attractive candidates as oral vaccine vectors, this potential has been poorly studied until now. Such study is limited by the restrictive host specificity of AdVs that hamper human AdV replication in laboratory animals. Here, we used the mouse AdV type 1 (MAV-1) in BALB/c mice to establish a model of oral replication-competent AdV based vaccines. Firstly, we evaluated the protection confered by a MAV-1 oral infection against a respiratory challenge with the same virus. We showed that MAV-1 oral administration recapitulates in BALB/c mice the homologous protection observed in human with AdVs 4 and 7 vaccines. Beside, our results indicated that live oral MAV-1 vaccine better protected from a respiratory challenge than inactivated intramuscular vaccine. This protection was associated with the presence of MAV-1 specific antibodies and with a better recruitment of effector CD8 T cells. However, we also found that such oral replication-competent vaccine generated a subclinical, but systemic infection that spread all over the body, raising important safety questions. After showing that MAV-1 is a consistent model to study replication-competent oral AdV based homologous vaccines in mouse, we adapted this model to investigate oral replicative AdV vectors for heterologous vaccination. We constructed MAV-1 recombinants expressing either the entire hemagglutinine (HA) of influenza or the stalk domain of this protein which, as a more conserved region, could be a “universal” influenza antigen. We then vaccinated mice orally with these mutants to evaluate the protection confered against a subsequent intranasal influenza challenge. While the truncated HA vector did not generate a significant humoral or cellular immune response to influenza, a single oral immunization with the full-length HA vaccine generated influenza specific and neutralizing antibodies, and completely protected mice against clinical signs and viral replication. This data confirmed that replication competent AdVs could constitute a very efficient vaccine platform for oral immunization. Nontheless, further investigations are still needed to establish their safety and rationnaly exploit their potential. Finally, to better figure out the mechanisms underlying AdV oral infection, we generated a luciferase expressing MAV-1 allowing to study AdVs in vivo through bioluminescence imaging. Using this tool, we compared several route of MAV-1 infection, in BALB/c and SJL mice respectively described as relatively resistant and highly sensitive. This difference was confirmed by intraperitoneal administration which gave rise to an intense signal in the brain and nasal horns of SJL mice, while these organes remained non luminescent in BALB/c mice. On the contrary, intranasal and intramuscular administrations respectively generated local lung and muscle signals, regardless of the mouse strain. Surprisingly, in both murine strains, no signal was detected following oral administration. These data illustrate the importance of the route of entry in the fate of AdV infection and suggests that the mouse strain is determining for pathogenesis specifically in case of intraperitoneal administration. Moreover, though our work leaves outstanding issues about the oral MAV-1 infection processes, it also provides a very usefull model to further decipher this phenomenon. We established here an innovative host specific animal model for oral replication competent AdV vaccines. While confirming the potential of replication competent AdVs as oral vaccine platform, our study highlights a significant risk of systemic infection linked to these vaccines. A better understanding of AdV infection and immunization mechanisms is therefore mandatory to attempt to utilize this potential in safe conditions. Our model should constitute a precious tool for the future development of such vaccine platforms

A Single Oral Immunization with a Replication-Competent Adenovirus-Vectored Vaccine Protects Mice from Influenza Respiratory Infection.

peer reviewedThe development of effective and flexible vaccine platforms is a major public health challenge, especially in the context of influenza vaccines that have to be renewed every year. Adenoviruses (AdVs) are easy to produce and have a good safety and efficacy profile when administered orally, as demonstrated by the long-term use of oral AdV-4 and -7 vaccines in the U.S. military. These viruses therefore appear to be the ideal backbone for the development of oral replicating vector vaccines. However, research into these vaccines is limited by the ineffectiveness of human AdV replication in laboratory animals. The use of mouse AdV type 1 (MAV-1) in its natural host allows infection to be studied under replicating conditions. Here, we orally vaccinated mice with a MAV-1 vector expressing influenza hemagglutinin (HA) to assess the protection conferred against an intranasal challenge of influenza. We showed that a single oral immunization with this vaccine generates influenza-specific and -neutralizing antibodies and completely protects mice against clinical signs and viral replication, similar to traditional inactivated vaccines. IMPORTANCE Given the constant threat of pandemics and the need for annual vaccination against influenza and possibly emerging agents such as SARS-CoV-2, new types of vaccines that are easier to administer and therefore more widely accepted are a critical public health need. Here, using a relevant animal model, we have shown that replicative oral AdV vaccine vectors can help make vaccination against major respiratory diseases more available, better accepted, and therefore more effective. These results could be of major importance in the coming years in the fight against seasonal or emerging respiratory diseases such as COVID-19

A Single Oral Immunization with Replication-Competent Adenovirus-Vectored Vaccine Induces a Neutralizing Antibody Response in Mice against Canine Distemper Virus.

peer reviewedCanine Distemper Virus (CDV) is a fatal and highly contagious pathogen of multiple carnivores. While injectable vaccines are very effective in protecting domestic animals, their use in the wild is unrealistic. Alternative vaccines are therefore needed. Adenovirus (AdV) vectors are popular vaccine vectors due to their capacity to elicit potent humoral and cellular immune responses against the antigens they carry. In parallel, vaccines based on live human AdV-4 and -7 have been used in U.S. army for several decades as replicative oral vaccines against respiratory infection with the same viruses. Based on these observations, the use of oral administration of replication competent AdV-vectored vaccines has emerged as a promising tool especially for wildlife vaccination. Developing this type of vaccine is not easy, however, given the high host specificity of AdVs and their very low replication in non-target species. To overcome this problem, the feasibility of this approach was tested using mouse adenovirus 1 (MAV-1) in mice as vaccine vectors. First, different vaccine vectors expressing the entire or part H or F proteins of CDV were constructed. These different strains were then used as oral vaccines in BALB/c mice and the immune response to CDV was evaluated. Only the strain expressing the full length CDV H protein generated a detectable and neutralizing immune response to CDV. Secondly, using this strain, we were able to show that although this type of vaccine is sensitive to pre-existing immunity to the vector, a second oral administration of the same vaccine is able to boost the immune response against CDV. Overall, this study demonstrates the feasibility of using replicating AdVs as oral vaccine vectors to immunize against CDV in wildlife carnivores

Replication of Brucella abortus and Brucella melitensis in fibroblasts does not require Atg5-dependent macroautophagy

BACKGROUND: Several intracellular bacterial pathogens have evolved subtle strategies to subvert vesicular trafficking pathways of their host cells to avoid killing and to replicate inside the cells. Brucellae are Gram-negative facultative intracellular bacteria that are responsible for brucellosis, a worldwide extended chronic zoonosis. Following invasion, Brucella abortus is found in a vacuole that interacts first with various endosomal compartments and then with endoplasmic reticulum sub-compartments. Brucella establishes its replication niche in ER-derived vesicles. In the past, it has been proposed that B. abortus passed through the macroautophagy pathway before reaching its niche of replication. However, recent experiments provided evidence that the classical macroautophagy pathway was not involved in the intracellular trafficking and the replication of B. abortus in bone marrow-derived macrophages and in HeLa cells. In contrast, another study showed that macroautophagy favoured the survival and the replication of Brucella melitensis in infected RAW264.7 macrophages. This raises the possibility that B. abortus and B. melitensis followed different intracellular pathways before replicating. In the present work, we have addressed this issue by comparing the replication rate of B. abortus and B. melitensis in embryonic fibroblasts derived from wild-type and Atg5(−/−) mice, Atg5 being a core component of the canonical macroautophagic pathway. RESULTS: Our results indicate that both B. abortus S2308 and B. melitensis 16M strains are able to invade and replicate in Atg5-deficient fibroblasts, suggesting that the canonical Atg5-dependent macroautophagic pathway is dispensable for Brucella replication. The number of viable bacteria was even slightly higher in Atg5(−/−) fibroblasts than in wild-type fibroblasts. This increase could be due to a more efficient uptake or to a better survival rate of bacteria before the beginning of the replication in Atg5-deficient cells as compared to wild-type cells. Moreover, our data show that the infection with B. abortus or with B. melitensis does not stimulate neither the conversion of LC3-I to LC3-II nor the membrane recruitment of LC3 onto the BCV. CONCLUSION: Our study suggests that like Brucella abortus, Brucella melitensis does not subvert the canonical macroautophagy to reach its replicative niche or to stimulate its replication. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12866-014-0223-5) contains supplementary material, which is available to authorized users

Oral vaccination with replication-competent adenovirus in mice reveals the 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 US 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 showed that MAV-1 oral administration recapitulates the protection against homologous respiratory challenge observed with adenoviruses 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 using MAV-1 to study replication-competent oral adenovirus-based vaccines but also highlight the fact that those vaccines could disseminate widely in the body.IMPORTANCE Replication-competent adenoviruses appear to be promising vectors for the development of oral vaccines in humans. However, study and development of these vaccines suffer from the lack of any reliable animal model. In this study, mouse adenovirus type 1 has been 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 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