Dimeric Ankyrin with Inverted Module Promotes Bifunctional Property in Capturing Capsid to Impede HIV-1 Replication.

Several anti-HIV scaffolds have been proposed as complementary treatments to highly active antiretroviral therapy. AnkGAG1D4, a designed ankyrin repeat protein, formerly demonstrated anti-HIV-1 replication by interfering with HIV-1 Gag polymerization. However, the improvement of the effectiveness was considered. Recently, the dimeric molecules of AnkGAG1D4 were accomplished in enhancing the binding activity against HIV-1 capsid (CAp24). In this study, the interaction of CAp24 against the dimer conformations was elucidated to elaborate the bifunctional property. The accessibility of the ankyrin binding domains was inspected by bio-layer interferometry. By inverting the second module of dimeric ankyrin (AnkGAG1D4NC-CN), the CAp24 interaction KD was significantly reduced. This reflects the capability of AnkGAG1D4NC-CN in simultaneously capturing CAp24. On the contrary, the binding activity of dimeric AnkGAG1D4NC-NC was indistinguishable from the monomeric AnkGAG1D4. The bifunctional property of AnkGAG1D4NC-CN was subsequently confirmed in the secondary reaction with additional p17p24. This data correlates with the MD simulation, which suggested the flexibility of the AnkGAG1D4NC-CN structure. The CAp24 capturing capacity was influenced by the distance of the AnkGAG1D4 binding domains to introduce the avidity mode of AnkGAG1D4NC-CN. Consequently, AnkGAG1D4NC-CN showed superior potency in interfering with HIV-1 NL4-3 WT and HIV-1 NL4-3 MIRCAI201V replication than AnkGAG1D4NC-NC and an affinity improved AnkGAG1D4-S45Y.

The Occluded Epitope Residing in Spike Receptor-Binding Motif Is Essential for Cross-Neutralization of SARS-CoV-2 Delta Variant.

Concerns over vaccine efficacy after the emergence of the SARS-CoV-2 Delta variant prompted revisiting the vaccine design concepts. Monoclonal antibodies (mAbs) have been developed to identify the neutralizing epitopes on spike protein. It has been confirmed that the key amino acid residues in epitopes that induce the formation of neutralizing antibodies do not have to be on the receptor-binding domain (RBD)- angiotensin-converting enzyme 2 (ACE2) contact surface, and may be conformationally hidden. In addition, this epitope is tolerant to amino acid mutations of the Delta variant. The antibody titers against RBD in health care workers in Thailand receiving two doses of CoronaVac, followed by a booster dose of BNT162b2, were significantly increased. The neutralizing antibodies against the Delta variant suggest that the overall neutralizing antibody level against the Wuhan strain, using the NeutraLISA, was consistent with the levels of anti-RBD antibodies. However, individuals with moderate anti-RBD antibody responses have different levels of a unique antibody population competing with a cross-neutralizing mAb clone, 40591-MM43, determined by in-house competitive ELISA. Since 40591-MM43 mAb indicates cross-neutralizing activity against the Delta variant, this evidence implies that the efficiency of the vaccination regimen should be improved to facilitate cross-protective antibodies against Delta variant infections. The RBD epitope recognized by 40591-MM43 mAb is hidden in the close state.

Dynamic of anti-spike receptor binding domain (RBD) levels and short-term adverse events following a heterologous booster dose of BNT162b2 after two doses of CoronaVac in Thai health care workers.

BACKGROUND: CoronaVac was administered as the primary COVID-19 vaccine for Thai health care workers (HCWs) in early 2021 in response to the epidemic of new variants. This study aimed to evaluate the dynamic of humoral immune response as well as the short-term side effects resulting from the booster dose of BNT162b2 following completion of a CoronaVac double-dose in Thai HCWs. METHODS: This study was conducted at a teaching hospital in Northern Thailand during August and September 2021. The participants were 50 HCWs who were vaccinated with 2 doses of CoronaVac and were scheduled to receive a booster dose of BNT162b2. Anti-SARS-CoV-2 IgG antibodies levels and short-term side effects were assessed. The anti-RBD level was determined using Architect SARS-CoV-2 IgG II Quant (Abbott). RESULT: Of the 50 participants, 37 were female. The median age was 33.0 years old. The average time between the second CoronaVac shot and the BNT162b2 booster shot was 81.7 days (SD = 25.0). The median anti-SARS-CoV-2 IgG antibody level on booster vaccination date, as well as day 14, and day 28 after the booster were 335.5 AU/ml, 31,613.5 AU/ml, and 20,311.9 AU/ml, respectively. Fourteen days after the booster, 94% of participants had anti-SARS-CoV-2 IgG antibody levels higher than 50.0 AU/ml. Being female, higher log anti-SARS-CoV-2 IgG antibodies prior to booster vaccination, and longer interval between the second shot and the booster shot were found to be significantly associated with higher levels of anti-SARS-CoV-2 IgG antibodies at both day 14 and day 28 after the booster. There were no reports of serious adverse events. CONCLUSION: A booster dose of BNT162B2 promoted a high level of anti-SARS-CoV-2 IgG antibodies among HCWs who received 2 doses of CoronaVac. The time between the second CoronaVac shot and the booster shot should be at least three months. There were no severe adverse effects observed.