Madeleine F. Jennewein

MRNA vaccines were the first to be authorized for use against SARS-CoV-2 and have since demonstrated high efficacy against serious illness and death. However, limitations in these vaccines have been recognized due to their requirement for cold storage, short durability of protection, and lack of access in low-resource regions. We have developed an easily-manufactured, potent self-amplifying RNA (saRNA) vaccine against SARS-CoV-2 that is stable at room temperature. This saRNA vaccine is formulated with a nanostructured lipid carrier (NLC), providing stability, ease of manufacturing, and protection against degradation. In preclinical studies, this saRNA/NLC vaccine induced strong humoral immunity, as demonstrated by high pseudovirus neutralization titers to the Alpha, Beta, and Delta variants of concern and induction of bone marrow-resident antibody-secreting cells. Robust Th1-biased T-cell responses were also observed after prime or homologous prime-boost in mice. Notably, the saRNA/NLC platform demonstrated thermostability when stored lyophilized at room temperature for at least 6 months and at refrigerated temperatures for at least 10 months. Taken together, this saRNA delivered by NLC represents a potential improvement in RNA technology that could allow wider access to RNA vaccines for the current COVID-19 and future pandemics.

Boosterism could save lives: Postinfection immune protection against severe acute respiratory syndrome coronavirus 2 reinfection is not fully understood. It will be devastating if waves of new variants emerge that undermine natural immune protection. Stamatatos et al. investigated immune responsiveness 4 to 8 months after previously infected individuals were given a messenger RNA–based vaccine developed for the original Wuhan variant (see the Perspective by Crotty). Before vaccination, postinfection serum antibody neutralization responses to virus variants were variable and weak. Vaccination elevated postinfection serum-neutralizing capacity approximately 1000-fold against Wuhan-Hu-1 and other strains, and serum neutralization against the variant B.1.351 was enhanced. Although responses were relatively muted against the variant, they still showed characteristic memory responses. Vaccination with the Wuhan-Hu-1 variant may thus offer a valuable boost to protective responses against subsequent infection with variant viruses. Science , abg9175, this issue p. 1413 ; see also abj2258, p. 1392

SUMMARY: Pregnancy represents a unique tolerogenic immune state which may alter susceptibility to infection and vaccine-response. Here we characterized humoral immunity to seasonal influenza vaccine strains in pregnant and non-pregnant women. Pregnant women had reduced hemagglutinin subtype-1 (H1)-IgG, IgG1, and IgG2, hemagglutination inhibition and group 1 and 2 stem IgG. However, H1-specific avidity and FcγR1 binding increased. Influenza-antibodies in pregnancy had distinct Fc and Fab glycans characterized by di-galactosylation and di-sialylation. In contrast, agalactosylation and bisection were prominent outside of pregnancy. H1-specific Fc-functionality was moderately reduced in pregnancy, although likely compensated by stronger binding to cognate antigen and FcR. Multivariate analysis revealed distinct populations characterized by FcγR1 binding, H1-IgG levels, and glycosylation. Pooled sera from pregnant women exhibited longer retention in vivo . Our results demonstrate structural and functional modulation of humoral immunity during pregnancy in an antigen-specific manner towards reduced inflammation, increased retention in circulation, and efficient placental transport.

Integrating form and function for design: Antibodies are broadly used in therapies and as research tools because they can be generated against a wide range of targets. Efficacy can often be increased by clustering antibodies in multivalent assemblies. Divine et al. designed antibody nanocages from two components: One is an antibody-binding homo-oligomic protein and the other is the antibody itself. Computationally designed proteins drive the assembly of antibody nanocages in a range of architectures, allowing control of the symmetry and the antibody valency. The multivalent display enhances antibody-dependent signaling, and nanocages displaying antibodies against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein effectively neutralize pseudovirus. Science , this issue p. eabd9994

Antibodies are widely used in biology and medicine, and there has been considerable interest in multivalent antibody formats to increase binding avidity and enhance signaling pathway agonism. However, there are currently no general approaches for forming precisely oriented antibody assemblies with controlled valency. We describe the computational design of two-component nanocages that overcome this limitation by uniting form and function. One structural component is any antibody or Fc fusion and the second is a designed Fc-binding homo-oligomer that drives nanocage assembly. Structures of 8 antibody nanocages determined by electron microscopy spanning dihedral, tetrahedral, octahedral, and icosahedral architectures with 2, 6, 12, and 30 antibodies per nanocage match the corresponding computational models. Antibody nanocages targeting cell-surface receptors enhance signaling compared to free antibodies or Fc-fusions in DR5-mediated apoptosis, Tie2-mediated angiogenesis, CD40 activation, and T cell proliferation; nanocage assembly also increases SARS-CoV-2 pseudovirus neutralization by α-SARS-CoV-2 monoclonal antibodies and Fc-ACE2 fusion proteins. We anticipate that the ability to assemble arbitrary antibodies without need for covalent modification into highly ordered assemblies with different geometries and valencies will have broad impact in biology and medicine.

Gene based delivery of immunoglobulins promises to safely and durably provide protective immunity to individuals at risk of acquiring infectious diseases such as HIV. We used a rhesus macaque animal model to optimize delivery of naturally-arising, autologous anti-SIV neutralizing antibodies expressed by Adeno-Associated Virus 8 (AAV8) vectors. Vectored transgene expression was confirmed by quantitation of target antibody abundance in serum and mucosal surfaces. We tested the expression achieved at varying doses and numbers of injections. Expression of the transgene reached a saturation at about 2 x 10¹² AAV8 genome copies (gc) per needle-injection, a physical limitation that may not scale clinically into human trials. In contrast, expression increased proportionately with the number of injections. In terms of anti-drug immunity, anti-vector antibody responses were universally strong, while those directed against the natural transgene mAb were detected in only 20% of animals. An anti-transgene antibody response was invariably associated with loss of detectable plasma expression of the antibody. Despite having atypical glycosylation profiles, transgenes derived from AAV-directed muscle cell expression retained full functional activity, including mucosal accumulation, in vitro neutralization, and protection against repeated limiting dose SIVsmE660 swarm challenge. Our findings demonstrate feasibility of a gene therapy-based passive immunization strategy against infectious disease, and illustrate the potential for the nonhuman primate model to inform clinical AAV-based approaches to passive immunization. Antibodies are the humoral component of an immune response against an invading pathogen or vaccine immunogen. For challenging vaccine targets, as an alternative to active vaccination to induce the immune system to generate antibodies, current research is exploring the delivery of these proteins to populations at high risk of infection as prophylactics against infectious diseases, like HIV, RSV, and Ebola, amongst others. Passive vaccination via purified protein will require periodic reinjection to retain protective levels in subjects, adding a barrier to large scale coverage. Alternatively, delivery of antibodies using gene therapy may provide a one-time passive vaccination alternative. This strategy comes with its own hurdles, including anti-vector immunity, anti-drug immunity, physical limitations of vector uptake and the need to confirm antibody functionality. To date, many passive vaccinations strategies remain untested in humans. Non-human primate models of infection are frequently useful for predicting the success of vaccine candidates or concepts. Here, we characterize and optimize a rhesus macaque model for the delivery of anti-viral antibodies via the gene therapy vector adeno-associated virus. Lastly, we demonstrate the ability of the mAbs to protect against viral challenge. Our work demonstrates the feasibility and utility of vectored delivery of antibody transgenes in rhesus macaques. We hope this model of antibody delivery may be applied to various disease models in non-human primates and will inform clinical trial design of passive vaccination against infectious diseases.