mRNA vaccines and hybrid immunity use different B cell germlines to neutralize Omicron BA.4 and BA.5

SARS-CoV-2 omicron BA.4 and BA.5, characterized by high transmissibility and ability to escape natural and vaccine induced immunity, are rampaging worldwide. To understand the escape mechanisms, we tested the neutralizing activity against omicron BA.4 and BA.5 of a panel of 482 human monoclonal antibodies that had been isolated from people who received two or three mRNA vaccine doses or from people that had been vaccinated after infection. None of the antibodies isolated after two vaccine doses neutralized omicron BA.4 and BA.5, while these variants were neutralized by approximately 15% of antibodies obtained from people that received three doses or had been vaccinated after infection. Remarkably, the antibodies isolated after three vaccine doses targeted mainly the receptor binding domain (RBD) Class 1/2 epitope region and were encoded by the IGHV1-69 and IGHV3-66 B cell germlines, while the antibodies isolated after infection recognized mostly the RBD Class 3 epitope region and the NTD, and were encoded by the IGHV2-5;IGHJ4-1 and IGHV1-24;IGHJ4-1 germlines. The observation that mRNA vaccination and hybrid immunity elicit a different immunity against the same antigen is intriguing and its understanding may help to design the next generation of therapeutics and vaccines against COVID-19.

COVID-19 mRNA third dose induces a unique hybrid immunity-like antibody response

The continuous evolution of SARS-CoV-2 generated highly mutated variants, like omicron BA.1 and BA.2, able to escape natural and vaccine-induced primary immunity1,2. The administration of a third dose of mRNA vaccines induces a secondary response with increased protection. We investigated, at single-cell level, the longitudinal evolution of the neutralizing antibody response in four donors after three mRNA doses3. A total of 4,100 spike protein specific memory B cells were single cell sorted and 350 neutralizing antibodies were identified. The third dose increased the antibody neutralization potency and breadth against all SARS-CoV-2 variants of concern as previously observed with hybrid immunity3. However, the B cell repertoire that stands behind the response is dramatically different. The increased neutralizing response was largely due to the expansion of B cell germlines poorly represented after two doses, and the reduction of germlines predominant after primary immunization such as IGHV3-53;IGHJ6-1 and IGHV3-66;IGHJ4-1. Divergently to hybrid immunity, cross-protection after a third dose was mainly guided by Class 1/2 antibodies encoded by IGHV1-58;IGHJ3-1 and IGHV1-69;IGHJ4-1 germlines. The IGHV2-5;IGHJ3-1 germline, which induced broadly cross-reactive Class 3 antibodies after infection or viral vector vaccination, was not induced by a third mRNA dose. Our data show that while neutralizing breadth and potency can be improved by different immunization regimens, each of them has a unique molecular signature which should be considered while designing novel vaccines and immunization strategies.

Structural insights of a highly potent pan-neutralizing SARS-CoV-2 human monoclonal antibody

As the coronavirus disease 2019 (COVID-19) pandemic continues, there is a strong need for highly potent monoclonal antibodies (mAbs) that are resistant against severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) variants of concern (VoCs). Here, we evaluate the potency of a previously described mAb J08 against these variants using cell-based assays and delve into the molecular details of the binding interaction using cryo-EM. We show that mAb J08 has low nanomolar affinity against VoCs, binds high on the receptor binding domain (RBD) ridge and is therefore unaffected by most mutations, and can bind in the RBD-up and -down conformations. These findings further validate the phase II/III human clinical trial underway using mAb J08 as a monoclonal therapy. One Sentence SummaryPotent neutralizing monoclonal antibody J08 binds SARS-CoV-2 spike independent of known escape mutations.

Hybrid immunity improves B cell frequency, antibody potency and breadth against SARS-CoV-2 and variants of concern

To understand the nature of the antibody response to SARS-CoV-2 vaccination, we analyzed at single cell level the B cell responses of five naive and five convalescent people immunized with the BNT162b2 mRNA vaccine. Convalescents had higher frequency of spike protein specific memory B cells and by cell sorting delivered 3,532 B cells, compared with 2,352 from naive people. Of these, 944 from naive and 2,299 from convalescents produced monoclonal antibodies against the spike protein and 411 of them neutralized the original Wuhan SARS-CoV-2 virus. More than 75% of the monoclonal antibodies from naive people lost their neutralization activity against the B.1.351 (beta) and B.1.1.248 (gamma) variants while this happened only for 61% of those from convalescents. The overall loss of neutralization was lower for the B.1.1.7 (alpha) and B.1.617.2 (delta) variants, however it was always significantly higher in those of naive people. In part this was due to the IGHV2-5;IGHJ4-1 germline, which was found only in convalescents and generated potent and broadly neutralizing antibodies. Overall, vaccination of seropositive people increases the frequency of B cells encoding antibodies with high potency and that are not susceptible to escape by any of the four variants of concern. Our data suggest that people that are seropositive following infection or primary vaccination will produce antibodies with increased potency and breadth and will be able to better control SARS-CoV-2 emerging variants.

Extremely potent human monoclonal antibodies from convalescent Covid-19 patients

Human monoclonal antibodies are safe, preventive and therapeutic tools, that can be rapidly developed to help restore the massive health and economic disruption caused by the Covid-19 pandemic. By single cell sorting 4277 SARS-CoV-2 spike protein specific memory B cells from 14 Covid-19 survivors, 453 neutralizing antibodies were identified and 220 of them were expressed as IgG. Up to 65,9% of monoclonals neutralized the wild type virus at a concentration of >500 ng/mL, 23,6% neutralized the virus in the range of 100 - 500 ng/mL and 9,1% had a neutralization potency in the range of 10 - 100 ng/mL. Only 1,4% neutralized the authentic virus with a potency of 1-10 ng/mL. We found that the most potent neutralizing antibodies are extremely rare and recognize the RBD, followed in potency by antibodies that recognize the S1 domain, the S-protein trimeric structure and the S2 subunit. The three most potent monoclonal antibodies identified were able to neutralize the wild type and D614G mutant viruses with less than 10 ng/mL and are good candidates for the development of prophylactic and therapeutic tools against SARS-CoV-2. One Sentence SummaryExtremely potent neutralizing human monoclonal antibodies isolated from Covid-19 convalescent patients for prophylactic and therapeutic interventions.

Identification of neutralizing human monoclonal antibodies from Italian Covid-19 convalescent patients

In the absence of approved drugs or vaccines, there is a pressing need to develop tools for therapy and prevention of Covid-19. Human monoclonal antibodies have very good probability of being safe and effective tools for therapy and prevention of SARS-CoV-2 infection and disease. Here we describe the screening of PBMCs from seven people who survived Covid-19 infection to isolate human monoclonal antibodies against SARS-CoV-2. Over 1,100 memory B cells were single-cell sorted using the stabilized prefusion form of the spike protein and incubated for two weeks to allow natural production of antibodies. Supernatants from each cell were tested by ELISA for spike protein binding, and positive antibodies were further tested for neutralization of spike binding to receptor(s) on Vero E6 cells and for virus neutralization in vitro. From the 1,167 memory B specific for SARS-CoV-2, we recovered 318 B lymphocytes expressing human monoclonals recognizing the spike protein and 74 of these were able to inhibit the binding of the spike protein to the receptor. Finally, 17 mAbs were able to neutralize the virus when assessed for neutralization in vitro. Lead candidates to progress into the drug development pipeline will be selected from the panel of neutralizing antibodies identified with the procedure described in this study. One Sentence SummaryNeutralizing human monoclonal antibodies isolated from Covid-19 convalescent patients for therapeutic and prophylactic interventions.

Perfil de gestantes em tratamento para a infecção pelo vírus da imunodeficiência humana / Profile of pregnant women under treatment for human immunodeficiency virus infection / Perfil de las mujeres embarazadas reciben tratamiento para la infección por el virus de inmunodeficiencia humana

Justificativa e Objetivos: A via de transmissão predominante em casos de HIV/aids pediátrica continua sendo a transmissão vertical. Sendo a infecção pelo HIV uma doença crônica e controlável, o acompanhamento do tratamento da mãe e seu filho são fundamentais. O objetivo foi verificar o perfil de gestantes portadoras do HIV atendidas em um Hospital público da região central do Rio Grande do Sul, e o momento em que ocorreu o diagnóstico da infecção. Métodos: Foi realizado um estudo descritivo, do tipo transversal, retrospectivo, com 46 gestantes recebendo terapia antirretroviral (TARV) para o HIV durante o período de janeiro a dezembro de 2015 junto a sua Unidade dispensadora de medicamentos. Os dados foram obtidos através da consulta no Sistema de Controle Logístico de Medicamentos, junto à farmácia hospitalar, e através de consulta em prontuários clínicos. Resultados: A média da idade no período da gestação foi de 29 anos (± 5,9), apenas 24% teve o diagnóstico fora de período gestacional, e a maioria (69,6%) sabia ser portadora do HIV antes da gestação atual, sendo que apenas 11,6% estavam esperando o primeiro filho. A maioria das gestantes recebeu TARV por mais de seis meses de gestação (60,9%). O pré-natal não foi realizado adequadamente em 19,6% destas gestantes resultando em TARV insatisfatória. Conclusão: Sendo o HIV uma infecção silenciosa, a gestação torna-se um momento oportuno para diagnóstico desta infecção. É necessária maior sensibilização quanto à importância de um pré-natal precoce e de adesão a TARV, buscando minimizar os riscos da transmissão vertical do HIV.(AU)

Background and Objectives: The predominant transmission route in cases of HIV/pediatric aids continues to be vertical transmission. Since HIV infection is a chronic and controllable disease, monitoring the treatment of the mother and her child is fundamental. The objective was to verify the profile of HIV- positive pregnant women attended at a public hospital in the central region of Rio Grande do Sul, and when it was made the diagnosis. Methods: A descriptive, cross-sectional, retrospective study was carried out with 46 pregnant women undergoing antiretroviral treatment (ART) for HIV during the period from January to December 2015. Data were obtained through the consultation in the Logistic Control System of Medications, in the hospital pharmacy, and in the medical records. Results: The mean age of the gestation period was 29 years old (± 5,9). Only 24% had the diagnosis outside the gestational period, and the majority (69,6%) knew to be HIV positive before the current gestation, with only 11, 6% expecting the first child. The majority of pregnant women received ART for more than 6 months of gestation (60.9%). Prenatal care was not adequately performed in 19.6%, and these pregnant women were not adequately treated. Conclusion: Since HIV is a silent infection, gestation becomes an opportune moment for the diagnosis of this infection. However, greater awareness of the importance of early prenatal care and adherence to ART is needed, in order to minimize the risk of vertical transmission of HIV.(AU)

Justificación y objetivos: La vía de transmisión predominante en casos de HIV/sida pediátrica sigue siendo la transmisión vertical. Siendo la infección por el VIH una enfermedad crónica y controlable, el seguimiento del tratamiento de la madre y su hijo son fundamentales. El objetivo fue verificar el perfil de gestantes portadoras del VIH atendidas en un Hospital público de la región central de Rio Grande do Sul, y cuando se realizó el diagnóstico. Métodos: Se realizó un estudio descriptivo ,en sección transversal, retrospectivo de 46 mujeres embarazadas que reciben terapia antirretroviral (HAART) para el VIH durante el período de enero a diciembre 2015. Los datos se obtuvieron mediante la consulta del Sistema de Gestión Logística de medicamentos en la farmacia hospitalaria y por medio de consultas en los registros clínicos. Resultados: El promedio de edad en el período de gestación fue de 29 años, sólo el 24% tuvo el diagnóstico fuera del período gestacional, y la mayoría (69,6%) sabía ser portadora del VIH antes de la gestación actual, siendo que sólo 11, 6% estaba embarazada del primer hijo. La mayoría de las mujeres embarazadas recibieron HAART durante más de seis meses de embarazo (60,9%). El prenatal no fue realizado adecuadamente en el 19,6%, quedando estas gestantes sin HAART. Conclusiones: Siendo el VIH una infección silenciosa, la gestación se convierte en un momento oportuno para el diagnóstico de esta infección. Sin embargo, es necesaria una mayor concientización en cuanto a la importancia de un pre-natal precoz y de adhesión a HAART.(AU)