Antibody Responses In Non-Severe SARS-CoV-2 Infections Are Driven By CD4+ T cells and Age.

SARS-CoV-2 infection causes a spectrum of clinical outcomes and diverse memory responses. Population studies indicate that viral neutralizing antibody responses are protective, but do not always develop post-infection. Other antiviral antibody effector functions, T-cell responses, or immunity to seasonal coronaviruses (OC43, 229E) have been implicated but not defined in all ages. Here, we identify that children and adult subjects generate polyfunctional antibodies to the spike protein after asymptomatic infection or mild disease, with some subjects developing cellular responses without seroconversion. Diversity in immunity was explained by two clusters distinguished by CD4+ T-cell cytokines, age, and antibodies to seasonal coronaviruses. Post-vaccination neutralizing responses were predicted by specific post-infection immune measures, including IL-2, spike-IgA, OC43-IgG1, 229E-IgM. We confirm a key role for CD4+ T cell cytokines in functionality of anti-spike antibodies, and show that antibody diversity is impacted by age, Th/Th2 cytokine biases, and antibody isotypes to SARS-CoV-2 and seasonal coronaviruses.

A sarbecovirus found in Russian bats uses human ACE2

Spillover of sarbecoviruses from animals to humans has resulted in outbreaks of severe acute respiratory syndrome SARS-CoVs and the ongoing COVID-19 pandemic. Efforts to identify the origins of SARS-CoV-1 and -2 has resulted in the discovery of numerous animal sarbecoviruses - the majority of which are only distantly related to known human pathogens and do not infect human cells. The receptor binding domain (RBD) on sarbecoviruses engages receptor molecules on the host cell and mediates cell invasion. Here, we tested the receptor tropism and serological cross reactivity for RBDs from two sarbecoviruses found in Russian horseshoe bats. While these two viruses are in a viral lineage distinct from SARS-CoV-1 and -2, one virus, Khosta-2, was capable of using human ACE2 to facilitate cell entry. Viral pseudotypes with a recombinant, SARS-CoV-2 spike encoding for the Khosta 2 RBD were resistant to both SARS-CoV-2 monoclonal antibodies and serum from individuals vaccinated for SARS-CoV-2. Our findings further demonstrate that sarbecoviruses circulating in wildlife outside of Asia also pose a threat to global health and ongoing vaccine campaigns against SARS-CoV-2 ONE SENTENCE SUMMARYEuropean bat coronaviruses that are only distantly related to SARS-CoV-2 but use the same cell entry route, escape the immune response against SARS-CoV-2 vaccines, driving the need for broader vaccines.

SARS-CoV-2 Seroprevalence Rates of Children in Louisiana During the State Stay at Home Order.

BACKGROUNDChildren ([≤]18 years) account for [~]20% of the US population but currently represent <2% of coronavirus disease 2019 (COVID-19) cases. Because infected children often have few or no symptoms and may not be tested, the extent of infection in children is poorly understood. METHODSDuring the March 18th-May 15th 2020 Louisiana Stay At Home Order, 1690 blood samples from 812 individuals from a Childrens Hospital were tested for antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein. Demographics, COVID-19 testing, and clinical presentation abstracted from medical records were compared with local COVID-19 cases. RESULTSIn total, 62 subjects (7.6%) were found to be seropositive. The median age was 11 years with 50.4% female. The presenting complaint of seropositive patients was chronic illness (43.5%). Only 18.2% had a previous positive COVID-19 PCR or antibody test. Seropositivity was significantly associated with parish (counties), race, and residence in a low-income area. Importantly, seropositivity was linearly correlated with cumulative COVID-19 case number for all ages by parish. CONCLUSIONIn a large retrospective study, the seropositivity prevalence for SARS-CoV-2 in children in Louisiana during the mandated Stay At Home Order was 7.6%. Residence location, race, and lower socioeconomic factors were linked to more frequent seropositivity in children and correlated to regional COVID-19 case rates. Thus, a significant number of children in Louisiana had SARS-CoV-2 infections that went undetected and unreported and may have contributed to virus transmission.