Age exacerbates SARS-CoV-2-induced blood-brain barrier leakage and neuropsychiatric dysfunction

Persistent cognitive impairment and neuropsychiatric disorders are prevalent sequelae of SARS-CoV-2-induced COVID-19 in middle-aged adults. To model age-related neurological vulnerability to COVID-19, we induced respiratory SARS-CoV-2 MA10 infections by nasal inoculation in young (2 months) and middle-aged (12 months) mice. We hypothesized that aging and SARS-CoV-2 synergistically damage the blood-brain barrier (BBB). Indeed, the combined action of aging and SARS-CoV-2 infection caused more fibrinogen leakage, T cell infiltration, and neuroinflammation in middle-aged SARS-CoV-2-infected mice than in similarly inoculated young adults. Mechanistically, SARS-CoV-2 exacerbated age-related increases in Caveolin-1 BBB transcellular permeability and loss of Wnt/{beta}-catenin ligands, with no apparent changes in tight junction proteins. Finally, SARS-CoV-2 infection induced age-dependent neuropsychiatric abnormalities including bradykinesia and obsessive-compulsive-like behavior. These observations indicate that cerebrovascular aging, including loss of Wnt suppression of Caveolin-1, heightens vulnerability to SARS-CoV-2-induced neuroinflammation and neuropsychiatric sequalae. Our work suggests that modulation of Wnt signaling or its downstream effectors at the BBB could be potential interventional strategies for Long COVID. HighlightsO_LITo our knowledge, we have for the first time used a small animal model to experimentally test the impact of age on SARS-CoV-2 neuropathology. C_LIO_LIAged mice were uniquely vulnerable to neuropsychiatric signs after SARS-CoV-2 infection C_LIO_LIMiddle-age increased gliosis, cerebrovascular inflammation, BBB permeability, and T cell infiltration in SARS-CoV-2 infected mice C_LIO_LIBBB permeability was related to loss of Wnt7a suppression of Caveolin-1 C_LI

Nucleocapsid-specific humoral responses improve the control of SARS-CoV-2

The spike protein of SARS-CoV-2 is a critical antigen present in all approved SARS-CoV-2 vaccines. This surface viral protein is also the target for all monoclonal antibody therapies, but it is unclear whether antibodies targeting other viral proteins can also improve protection against COVID-19. Here, we interrogate whether nucleocapsid-specific antibodies can improve protection against SARS-CoV-2. We first immunized mice with a nucleocapsid-based vaccine, and then transferred sera from these mice into naive mice. On the next day, the recipient mice were challenged intranasally with SARS-CoV-2 to evaluate whether nucleocapsid-specific humoral responses affect viral control. Interestingly, mice that received nucleocapsid-specific sera exhibited enhanced control of a SARS-CoV-2 infection. These findings provide the first demonstration that humoral responses specific to an internal coronavirus protein can help clear infection, warranting the inclusion of other viral antigens in next-generation SARS-CoV-2 vaccines and providing a rationale for the clinical evaluation of nucleocapsid-specific monoclonals to treat COVID-19. HighlightsA SARS-CoV-2 nucleocapsid vaccine elicits robust nucleocapsid-specific antibody responses. This nucleocapsid vaccine generates memory B cells (MBC). Nucleocapsid-specific humoral responses do not prevent SARS-CoV-2 infection. Nucleocapsid-specific humoral responses help control a SARS-CoV-2 infection.

SARS coronavirus vaccines protect against different coronaviruses

Although SARS-CoV-2 vaccines have shown efficacy against SARS-CoV-2, it is unclear if they can also protect against other coronaviruses that may infect humans in the future. Here, we show that SARS-CoV-2 vaccination in humans elicits cross-reactive antibodies against other coronaviruses. Our studies in mice demonstrate that SARS-CoV-2 vaccination protects against a common cold coronavirus, and that SARS-CoV-1 vaccination protects against SARS-CoV-2. Similarly, infection with a common cold coronavirus also conferred enhanced protection from subsequent infections with other coronaviruses. Mechanistically, both T cells and antibodies mediated cross-protection. This is the first direct demonstration that coronavirus-specific immunity can confer heterologous protection in vivo, providing a rationale for universal coronavirus vaccines. HighlightsO_LISARS-CoV-2 vaccination elicits cross-reactive antibody against other coronaviruses in humans. C_LIO_LICOVID-19 patients generate cross-reactive antibody against other coronaviruses. C_LIO_LIA SARS-CoV-1 vaccine protects against SARS-CoV-2. C_LIO_LIPrior coronavirus infections improve immune protection following heterologous coronavirus challenges. C_LI

A SARS CoV-2 nucleocapsid vaccine protects against distal viral dissemination

The SARS CoV-2 pandemic has killed millions of people. This viral infection can also result in substantial morbidity, including respiratory insufficiency and neurological manifestations, such as loss of smell and psychiatric diseases. Most SARS CoV-2 vaccines are based on the spike antigen, and although they have shown extraordinary efficacy at preventing severe lung disease and death, they do not always confer sterilizing immune protection. We performed studies in K18-hACE2 mice to evaluate whether the efficacy of SARS CoV-2 vaccines could be augmented by incorporating nucleocapsid as a vaccine antigen. We vaccinated mice with adenovirus-based vaccines encoding spike antigen alone, nucleocapsid antigen alone, or combined spike and nucleocapsid antigens. Mice were then challenged intranasally with SARS CoV-2, and acute viral loads were quantified at a proximal site of infection (lung) and a distal site of infection (brain). Interestingly, the spike-based vaccine conferred acute protection in the lung, but not in the brain. The spike-based vaccine conferred acute protection in the brain only if combined with the nucleocapsid-based vaccine. These findings suggest that nucleocapsid-specific immunity is important for the distal control of SARS CoV-2, warranting the inclusion of nucleocapsid in next-generation COVID-19 vaccines.

mRNA induced expression of human angiotensin-converting enzyme 2 in mice for the study of the adaptive immune response to severe acute respiratory syndrome coronavirus 2

The novel human coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a pandemic resulting in nearly 20 million infections across the globe, as of August 2020. Critical to the rapid evaluation of vaccines and antivirals is the development of tractable animal models of infection. The use of common laboratory strains of mice to this end is hindered by significant divergence of the angiotensin-converting enzyme 2 (ACE2), which is the receptor required for entry of SARS-CoV-2. In the current study, we designed and utilized an mRNA-based transfection system to induce expression of the hACE2 receptor in order to confer entry of SARS-CoV-2 in otherwise non-permissive cells. By employing this expression system in an in vivo setting, we were able to interrogate the adaptive immune response to SARS-CoV-2 in type 1 interferon receptor deficient mice. In doing so, we showed that the T cell response to SARS-CoV-2 is enhanced when hACE2 is expressed during infection. Moreover, we demonstrated that these responses are preserved in memory and are boosted upon secondary infection. Interestingly, we did not observe an enhancement of SARS-CoV-2 specific antibody responses with hACE2 induction. Importantly, using this system, we functionally identified the CD4+ and CD8+ peptide epitopes targeted during SARS-CoV-2 infection in H2b restricted mice. Antigen-specific CD8+ T cells in mice of this MHC haplotype primarily target peptides of the spike and membrane proteins, while the antigen-specific CD4+ T cells target peptides of the nucleocapsid, membrane, and spike proteins. The functional identification of these T cell epitopes will be critical for evaluation of vaccine efficacy in murine models of SARS-CoV-2. The use of this tractable expression system has the potential to be used in other instances of emerging infections in which the rapid development of an animal model is hindered by a lack of host susceptibility factors.