ABSTRACT
We identified novel neutralizing monoclonal antibodies against SARS-CoV-2 variants (including Omicron) from individuals received two doses of mRNA vaccination after they had been infected with wildtype. We named them MO1, MO2 and MO3. MO1 shows high neutralizing activity against authentic variants: D614G, Delta, BA.1, BA.1.1, BA.2, and BA.2.75 and BA.5. Our findings confirm that the wildtype-derived vaccination can induce neutralizing antibodies that recognize the epitopes conserved among the SARS-CoV-2 variants (including BA.5 and BA.2.75). The monoclonal antibodies obtained herein could serve as novel prophylaxis and therapeutics against not only current SARS-CoV-2 viruses but also future variants that may arise.
ABSTRACT
The VOC of SARS-CoV-2, Omicron (BA.1, BA.1.1, BA.2, or BA.3), is associated with an increased risk of reinfection. BA.2 has become the next dominant variant worldwide. Although BA.2 infection has been shown to be mild illness, its high transmissibility will result in high numbers of cases. In response to the surge of Omicron BA.1 cases, booster vaccination was initiated in many countries. But there is limited evidence regarding the effectiveness of a booster vaccination against BA.2. We collected blood samples from 84 physicians at Kobe University Hospital, Japan, in January 2022 [~]7 months after they had received two BNT162b2 vaccinations and [~]2 weeks after their booster vaccination. We performed a serum neutralizing assay against BA.2 using authentic virus. Although most of the participants had no or a very low titer of neutralizing antibody against BA.2 at 7 months after two BNT162b2 vaccinations, the titer increased significantly at 2 weeks after the booster vaccination.
ABSTRACT
The SARS-CoV-2 variant Omicron is now under investigation. We evaluated cross-neutralizing activity against Omicron in COVID-19 convalescent patients (n=23) who had received two doses of an mRNA vaccination (BNT162b2 or mRNA-1273). Surprisingly and interestingly, after the second vaccination, the subjects neutralizing antibody titers including that against Omicron all became seropositive, and significant fold-increases (21.1-52.0) were seen regardless of the subjects disease severity. Our findings thus demonstrate that at least two doses of mRNA vaccination to SARS-CoV-2 convalescent patients can induce cross-neutralizing activity against Omicron.
ABSTRACT
To investigate the induction of neutralizing antibodies against Omicron after two and three vaccine doses in recipients of different ages. Physicians at Kobe University Hospital who had received the second dose of the BNT162b2 mRNA vaccine. At 2 months after the second vaccinations, the positive rate of neutralizing antibody against Omicron was 28%, and the titer was significantly lower than those against other variants, 11.8-fold and 3.6-fold lower than those against D614G and Delta, respectively. Unlike Delta, that positive rates of neutralizing antibody against Omicron were low in all age groups, and there was no significant difference in titers among age groups. Seven months after the 2nd dose, the positive rate of neutralizing antibody against Omicron decreased to 6%, but after the booster,3rd vaccination, it increased to 100%, and the titer was much higher than those at 2 and 7 months post-vaccination, 32-fold and 39-fold respectively. The booster vaccination effect was also observed in the younger at 41-fold, middle-aged at 43-fold, and older at 27-fold groups compared to the 7-month titers. Surprisingly, higher-than-predicted titers of the neutralizing antibodies against Omicron were induced after the booster vaccination regardless of recipient age, while this effect was not observed after two doses, indicating the induction of antibodies against common epitopes by the booster vaccination. Three doses can be confidently recommended to suppress the pandemic.
ABSTRACT
BackgroundThe COVID-19 pandemic situation has been changing drastically worldwide due to the continuous appearance of SARS-CoV-2 variants and the roll-out of mass vaccination. Periodic cross-sectional studies during the surge of COVID-19 cases is essential to elucidate the pandemic situation. MethodsSera of 1,000 individuals who underwent a health check-up in Hyogo Prefecture Health Promotion Association clinics in Japan were collected in August and December 2021. Antibodies against SARS-CoV-2 N and S antigens were detected in the sera by an electrochemiluminescence immunoassay (ECLIA) and an enzyme-linked immunosorbent assay (ELISA), respectively. The seras neutralization activities for the conventional SARS-CoV-2 (D614G), Delta, and Omicron variants were measured. ResultsThe seropositive rates for the antibody against N antigen were 2.1% and 3.9% in August and December 2021 respectively, demonstrating a Delta variant endemic during that time; the actual infection rate was approximately twofold higher than the rate estimated based on the polymerase chain reaction (PCR)-based diagnosis. The anti-S seropositive rate was 38.7% in August and it reached 90.8% in December, in concordance with the vaccination rate in Japan. In the December cohort, 78.7% of the sera showed neutralizing activity against the Delta variant, whereas that against the Omicron was much lower at 36.6%. ConclusionsThese analyses revealed that herd immunity against SARS-CoV-2 including the Delta variant was established in December 2021, leading to convergence of the variants. The low neutralizing activity against the Omicron variant suggests the need for the further promotion of the prompt three-dose vaccination to overcome this variants imminent 6th wave in Japan. SummarySeroepidemiologic study of COVID-19 on December 2021 in Japan showed neutralizing antibodies for Delta were 78.7%, indicating the acquisition of herd immunity by mass vaccination leading to convergence while those for Omicron were only 36.6%, indicating need of booster vaccination.
ABSTRACT
The situation of the COVID-19 pandemic in Japan is drastically changing in the 2nd year, 2021, due to the appearance of SARS-CoV-2 variants of concern and the roll-out of mass vaccination. In addition to PCR diagnosis, periodic seroepidemiologic surveillance is important to analyze the epidemic situation. In this study, we analyzed the rate of seropositivity for the SARS-CoV-2 N and S antigens in Hyogo prefecture, Japan in August 2021. Sera collected from people who received a health check-up in a clinic of the Hyogo Prefecture Health Promotion Association were subjected to analysis of reactivity to the SARS-CoV-2 N and S antigens by electrochemiluminescence immunoassay (ECLIA) and enzyme-linked immunosorbent assay (ELISA), respectively. For a total 1,000 sera, the positive rates to N and S antigens were 2.1% and 38.7%, respectively. The infectious rate estimated by serological analysis based on the presence of the anti-N antibody was 2.5-fold higher than the value reported based on PCR-based analysis, and it increased five-fold compared to the rate determined by our previous seroepidemiologic study in October, 2020. The anti-S positive rate was almost consistent with the vaccination rate in this area. The observed high anti-S antibody level in the seropositive population may indicate that the mass vaccination in Japan is being performed smoothly at this time point, although the infectious rate has also increased.
ABSTRACT
In March 2021, Japan is facing a 4th wave of SARS-CoV-2 infection. To prevent further spread of infection, sera cross-neutralizing activity of patients previously infected with conventional SARS-CoV-2 against novel variants is important but is not firmly established. We investigated the neutralizing potency of 81 COVID-19 patients sera from 4 waves of pandemic against SARS-CoV-2 variants using their authentic viruses. Most sera had neutralizing activity against all variants, showing similar activity against B.1.1.7 and D614G, but lower activity especially against B.1.351. In the 4th wave, sera-neutralizing activity against B.1.1.7 was significantly higher than that against any other variants, including D614G. The cross-neutralizing activity of convalescent sera was effective against all variants but was potentially weaker for B.1.351.
ABSTRACT
BackgroundCOVID-19 patients show a wide clinical spectrum ranging from mild respiratory symptoms to severe and fatal disease, and older individuals are known to be affected more severely. Neutralizing antibody for viruses is critical for their elimination, and increased cytokine/chemokine levels are thought to be related to COVID-19 severity. However, the trend of the neutralizing antibody production and cytokine/chemokine levels during the clinical course of COVID-19 patients with differing levels of severity has not been established. MethodsWe serially collected 45 blood samples from 12 patients with different levels of COVID-19 severity, and investigated the trend of neutralizing antibody production using authentic SARS-CoV-2 and cytokine/chemokine release in the patients clinical courses. ResultsAll 12 individuals infected with SARS-CoV-2 had the neutralizing antibody against it, and the antibodies were induced at approx. 4-10 days after the patients onsets. The antibodies in the critical and severe cases showed high neutralizing activity in all clinical courses. Most cytokine/chemokine levels were clearly high in the critical patients compared to those with milder symptoms. ConclusionNeutralizing antibodies against SARS-CoV-2 were induced at a high level in the severe COVID-19 patients, indicating that abundant virus replication occurred. Cytokines/chemokines were expressed more in the critical patients, indicating that high productions of cytokines/chemokines have roles in the disease severity. These results may indicate that plasma or neutralizing antibody therapy could be a first-line treatment for older patients to eliminate the virus, and corticosteroid therapy could be effective to suppress the cytokine storm after the viral genomes disappearance.
