key: cord-0311717-emjxe48t
authors: Langel, Stephanie N.; Johnson, Susan; Martinez, Clarissa I.; Tedjakusuma, Sarah N.; Peinovich, Nadine; Dora, Emery G.; Kuehl, Philip J.; Irshad, Hammad; Barrett, Edward G.; Werts, Adam; Tucker, Sean N
title: Oral and intranasal Ad5 SARS-CoV-2 vaccines decrease disease and viral transmission in a golden hamster model
date: 2021-10-05
journal: bioRxiv
DOI: 10.1101/2021.10.03.462919
sha: f4e62278fc55bce6c296ddc165a7e8b76e12ef11
doc_id: 311717
cord_uid: emjxe48t

Transmission-blocking strategies that slow the spread of SARS-CoV-2 and protect against COVID-19 are needed. We have developed a shelf-stable, orally-delivered Ad5-vectored SARS-CoV-2 vaccine candidate that expresses the spike protein. Here we demonstrated that oral and intranasal SARS-CoV-2 vaccination of this candidate protected against disease in index hamsters, and decreased aerosol transmission to unvaccinated, naïve hamsters. We confirmed that mucosally-vaccinated hamsters had robust antibody responses. We then induced a post-vaccination infection by inoculating vaccinated index hamsters with SARS-CoV-2. Oral and IN-vaccinated hamsters had decreased viral RNA and infectious virus in the nose and lungs and experienced less lung pathology compared to mock-vaccinated hamsters post challenge. Naive hamsters exposed in a unidirectional air flow chamber to mucosally-vaccinated, SARS-CoV-2-infected hamsters had lower nasal swab viral RNA and exhibited less clinical symptoms of disease than control animals. Our data demonstrate that oral immunization is a viable strategy to decrease SARS-CoV-2 disease and aerosol transmission.

transmission. We have created a replication-defective, shelf-stable oral adenoviral 49 vector vaccine candidate expressing the spike (S) protein from SARS-CoV-2 (r-Ad-S) 50 that is designed to induce both systemic and mucosal immunity. Importantly, immune 51 activation via the intestine may represent an important organ for oral immunization as 52 antibody secreting plasmablasts and plasma cells can traffic from the gut to the nose, 53 trachea, and lung 9,10 . Prior work in a human influenza challenge study with the same 54 platform has shown an ability to limit viral RNA shedding of influenza virus 11 , 55 highlighting the utility of this vaccination strategy for respiratory viruses. 56 To study the potential impact of oral vaccination on transmission to naïve individuals, 57 we used a hamster infection and aerosol transmission system. We vaccinated index 58 hamsters with oral r-Ad-S, using intranasal (IN) r-Ad-S as a control for mucosal 59 stimulation, intramuscular spike protein (IM S) as a control for systemic stimulation, and 60 oral PBS as a mock control. We then infected animals, via IN delivery, with a high titer of SARS-CoV-2 in order to replicate a post-vaccination infection. One-day post viral 62 challenge, index hamsters were placed upstream of vaccine-naïve hamsters in a 63 chamber that allowed aerosol movement but not direct contact or fomite transmission. 64 We demonstrated that post-vaccination, the oral and IN r-Ad-S groups had higher week 7 ( Figure 1A ). To determine immunogenicity of these vaccines, serum was 80 collected at weeks 0, 3 and 6 post immunization. BAL was collected upon necropsy 81 (day 5 post-inoculation) ( Figure 1A ). Oral and IN r-Ad-S vaccinated groups had 82 significantly higher S-specific IgG antibody titers in serum at week 3 compared to mock-dosed hamsters; this was not true in IM S vaccinated hamsters ( Figure 1B ). Using a 84 surrogate virus neutralizing test (sVNT), serum from IN r-Ad-S hamsters had greater 85 ability to block binding of SARS-CoV-2 S to ACE-2 after the booster vaccination (week 86 6) compared to serum from mock-vaccinated hamsters ( Figure 1C ).

Serum anti-S IgA antibodies increased post-oral and IN r-Ad-S vaccination but not in IM 88 S or mock groups ( Figure 1D ). As expected from our oral immunization platform, oral r- the study compared to mock-vaccinated animals ( Figure 3B ). To quantify pulmonary 115 inflammation, lung weights were measured, and lungs were scored for gross pathology.

In index animals, lung weights (normalized to total body weight) ( Figure 3C ) and As a test of transmissibility, unvaccinated naïve hamsters were exposed to vaccinated, loads in all index animals was above 7.8x10 7 gene copies per swab (Figure 2A ).

In naïve hamsters exposed to the oral and IN r-Ad-S-immunized groups, SARS-CoV-2 134 RNA was significantly lower on days 1 and 3 compared to mock-immunized animals 135 ( Figure 4A ). The number of vaccine naïve animals with nasal swab viral RNA levels 136 above a threshold of 1x10 5 gene copies was also determined. On day 1 post exposure 137 of the index and naïve animals, there were 3 naïve hamsters (3/16) exposed to the oral 138 r-Ad-S index group that were above the threshold compared to eleven mock exposed 139 hamsters (11/16) (p=0.011, Fisher's exact test) ( Figure 4A , Extended data Table 1 ). The 140 naïve hamsters exposed to IN r-Ad-S index hamsters had 0 (0/16) animals above the 141 threshold which was not significantly different than oral, but significantly lower than 142 naïve animals exposed to aerosol from mock-vaccination animals (p=0.22, p<0.0001 by 143 Fisher's exact test respectively) ( Figure 4A , Extended data Table 1 ). On day 3, in the 144 oral exposed group, 11 (11/16) had nasal swab viral RNA levels above the threshold 145 compared to 16 (16/16) for the naïve exposed group (p=0.043 by Fisher's exact test) 146 ( Figure 4A , Extended data Table 1 ). The naïve animals exposed to IN index animals 147 had 6 (6/16) which was not significantly different than oral (p=0.16 by Fisher's exact 148 test) ( Figure 4A , Extended data Table 1 ). These data demonstrate decreased SARS- Figure 4E ). This is compared to naïve animals exposed additional phase 2 study using the vaccine candidate tested in this study and given as a 240 tablet will begin clinical studies shortly. In summary, the data presented here demonstrate that oral immunization is a viable strategy to decrease SARS-CoV-2 242 transmission and disease, and should be considered for vaccination efforts that 243 increase global immunity to SARS-CoV-2. were supplied with a certified diet, filtered municipal water, and dietary and 305 environmental enrichment. The study was powered to compare viral RNA loads in naïve 306 hamsters exposed to vaccinated, SARS-CoV-2 infected index animals between vaccine 307 groups, where beta was set to 0.2, alpha=0.05. Assuming an attack rate of 80% 308 infected in the placebo group and a vaccine efficacy of 70%, an N=15 was calculated 309 with continuity correction 27 . The study was rounded to 16 naïve, 4 index to maintain the 310 1:4 ratio. The study was not powered to directly compare index groups, but many 311 statistical significances were achieved with N=4.

All r-Ad-S vaccinations were given at a dose of 1e9 IU (1:100 of a human dose 11 ). Oral Each vaccine/index group had 4 animals, and matched with a corresponding N=16 321 naïve exposed animals (1:4 ratio of index to naïve, with 1 index animal exposed to 4 322 naïve in a chamber setup). All animals were sacrificed five-days post inoculation (index) 323 or aerosol chamber exposure (naïve) for terminal assays. 

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