Studies show that pan-salvecovirus nanobodies may promote the development of hyperimmunity

With the emergence of severe acute respiratory coronavirus 2 (SARS-CoV-2) and concerns about its variants, scientists are looking forward to completely preventing the spread of the respiratory virus.New research published in bioRxiv* Preprint servers have been found to show strong affinity for all salvecovirus clade and neutralized SARS-CoV-2 receptor binding domains when the pan-salvecovirus nanobody is applied. The result is “superimmunity” against salvecoviruses containing the Omicron mutant.

Study: Hyperimmunity with widely protected Nanobodies against salvecovirus. Image Credit: Juan Gaertner / Shutterstock

Researchers point out that preventing future virus outbreaks requires prophylactic methods that combine protection and cost-effective technologies. They suggest that small, multiple routes of administration with Nanobodies are attractive complements to vaccines, small molecule drugs, and monoclonal antibody therapies.

the study

Lama was given a recombinant vaccine containing the SARS-CoV-2 receptor binding domain-Fc fusion protein. Blood samples were collected 2 months after the first dose and 3 boosts. Lama then collected another set of blood samples after being given four more boosters in two months.

Blood samples after booster immunization showed antibodies with higher affinity for the receptor binding domain of SARS-CoV-2 compared to the first immunized blood sample. In addition, strong neutralizing efficacy was observed against the original SARS-CoV-2 strain, along with alpha and lambda variants.

Booster shots increased the ability to neutralize beta, delta, and severe acute respiratory coronavirus (SARS-CoV). To the surprise of the researchers, the vaccine booster showed increased binding affinity for the receptor binding domain and broad neutralizing efficacy against a range of salvecoviruses.

Next, researchers investigated the use of broad-spectrum pan-Salvecovirus nanobodies to help inhibit Salvecovirus. They found that 100 Nanobodies showed strong affinity for the SARS-CoV-2 receptor binding domain and also showed cross-reactivity with other salvecoviruses. For example, 42% of Nanobodies bound to four different salvecoviruses and neutralized SARS-CoV-2 at low doses of less than 500 nanomoles.

Nanobodies are composed of multiple clusters and have various physicochemical properties such as isoelectric points and hydrotherapy. The three largest nanobody clusters contained at least three salvecovirus-bound neutralizers.

The binding affinities of 17 Nanobodies were tested against 5 SARS-CoV-2 variants (including Omicron) and 18 other Salvecovirus receptor binding domains. All Nanobodies showed strong binding to the mutant. Of the 17 Nanobodies bound to the four salvecoviruses, 16 showed broad activity against all salvecoviruses studied. These Nanobodies were also very specific for salvecovirus and did not show cross-reactivity with high concentrations of human total protein extract.

Group ANb 2-67 showed exceptional efficacy against SARS-CoV-2 and its variants.

Nanobodies have withstood aerosolization without compromising their activity, thus exhibiting high durability and stability.

Researchers have discovered five different epitope classes on the SARS-CoV-2 receptor binding domain through epitope clustering. Nanobodies did not overlap with the mutations observed at alpha, beta, delta, lambda, gamma, and omicron, and Nanobodies covered more than 85% of the receptor binding domain residues.

In addition, Nanobodies appeared to be fixed to a 3-up conformation. Despite the different epitopes, the small Nanobodies allow three copies to bind to the spike trimer at the same time.

Throughout the study, researchers observed an overexpression of a particular class of Nanobodies known as Class II. The ones collected after the first immunization show high diversity, but the Class II Nanobodies collected after the booster shots are more convergent. These Nanobodies share conserved hydrophobic core epitopes with regions stabilized by disulfide bonds.

Class IIB Nanobodies form two large clusters and have the highest breadth and potency against salvecovirus. Nanobodies form hydrophobic interactions that strongly bind to conserved charged residues via electrostatic interactions.

Class III Nanobodies destabilize Spike protein, And their structure include targeting rare non-RBS epitopes that slightly overlap with Nb17. Nb17 was collected after the first blood sample and was effective against the mutant. Beyond Nb17, other Class III Nanobodies function through recognition motifs that shift towards smaller conserved epitopes.

Class IV Nanobodies operate via different scaffold orientations and sequence-specific coupling networks. They share a highly conserved and mysterious epitope that is accessible only in receptor-binding domain upconformations.

Class V Nanobodies target receptor binding domains via conserved epitopes that are embedded in peplomers and are located in regions that partially overlap the binding motifs of Class IV Nanobodies.

Continuous immunization produced antibodies that targeted various conservative sites on the receptor-binding domain. The application of ultra-high affinity Nanobodies has also been shown to have a neutralizing effect.

The pansalvecovirus nanobody may neutralize the virus by sterically interfering with the receptor-binding domain and the binding of human ACE2 glycan N322.

Compared to previous Nanobodies, Pansalvecovirus Nanobodies target small, flat, or convex areas.

*Important Notices

bioRxiv publishes unpeer-reviewed preliminary scientific reports and should not be considered definitive, guide clinical / health-related behaviors, or be treated as established information.