Immunity Against Malaria: an Atlas of the Mosquito Cellular Immune System at Single Cell Resolution

Malaria is a deadly, worldwide disease, yearly responsible for 219 million cases and over four hundred thousand deaths. The Anopheles gambiae species complex is the main African vector for the most virulent malaria parasite: Plasmodium falciparum. Mosquitos are not mere bystanders however, and rely on both humoral and cellular innate immune divisions to defeat invading pathogens. These efforts are coordinated by hemocytes, the insect equivalent to vertebrate’s white blood cells, circulating in the hemolymph within the insects’ body cavity. Yet, hemocyte biology is largely unknown, mainly due to the low number and fragility of mosquito immune cells. Here we dissect the Anopheles immune system under baseline and challenged conditions with single-cell RNA sequencing to identify previously unknown cell types, their gene signatures, and spatial-temporal localization in the mosquito. We profiled 5,292 individual Anopheles hemocytes 1,3 and 7 days after sugar-feeding, blood-feeding, or infection with Plasmodium berghei, as well as 3123 A. aegypti hemocytes. We identified 9 cell sub-types, including novel effector, phagocytic, and anti-microbial cell subtypes, in addition to dividing progenitor cells, validating the main cell types via correlative microscopy and morphology. And we described four lineages of hemocytes, showing them to be divided into two branches: oenocytoids and prohemocyte-granulocyte. We also found both blood-feeding and malaria infection to dramatically shift the composition of a mosquito’s immune system, activating effector and proliferating cells at days 1 and 3 before returning to baseline by day 7. Conversely, human P. falciparum appears to inactivate an important local effector subtype. Our work is the first comprehensive transcriptomic study of a whole insect immune system. It demonstrates hemocytes are a dynamic, diverse class of insect cells which complexity far exceeds what is currently described in the literature. Our methods and results will hopefully serve as a resource for many entomologists, and could prove useful in developing novel vector control strategies. Our website will ease data access and provide an intuitive way to visualise hemocyte information: https://hemocytes.cellgeni.sanger.ac.uk/NIH Oxford-Cambridge scholarship, the UCLA-Caltech MSTP, and the NIGMS T32 GM00804

Human seasonal coronavirus neutralization and COVID-19 severity.

Funder: UK Research and Innovation; Id: http://dx.doi.org/10.13039/100014013Funder: National Institute for Health Research; Id: http://dx.doi.org/10.13039/501100000272The virus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), responsible for the global coronavirus disease-2019 (COVID-19) pandemic, spread rapidly around the world causing high morbidity and mortality. However, there are four known, endemic seasonal coronaviruses in humans (HCoVs), and whether antibodies for these HCoVs play a role in severity of COVID-19 disease has generated a lot of interest. Of these seasonal viruses NL63 is of particular interest as it uses the same cell entry receptor as SARS-CoV-2. We use functional, neutralizing assays to investigate cross-reactive antibodies and their relationship with COVID-19 severity. We analyzed the neutralization of SARS-CoV-2, NL63, HKU1, and 229E in 38 COVID-19 patients and 62 healthcare workers, and a further 182 samples to specifically study the relationship between SARS-CoV-2 and NL63. We found that although HCoV neutralization was very common there was little evidence that these antibodies neutralized SARS-CoV-2. Despite no evidence in cross-neutralization, levels of NL63 neutralizing antibodies become elevated after exposure to SARS-CoV-2 through infection or following vaccination

Neutralisation Hierarchy of SARS-CoV-2 Variants of Concern Using Standardised, Quantitative Neutralisation Assays Reveals a Correlation With Disease Severity; Towards Deciphering Protective Antibody Thresholds.

The rise of SARS-CoV-2 variants has made the pursuit to define correlates of protection more troublesome, despite the availability of the World Health Organisation (WHO) International Standard for anti-SARS-CoV-2 Immunoglobulin sera, a key reagent used to standardise laboratory findings into an international unitage. Using pseudotyped virus, we examine the capacity of convalescent sera, from a well-defined cohort of healthcare workers (HCW) and Patients infected during the first wave from a national critical care centre in the UK to neutralise B.1.1.298, variants of interest (VOI) B.1.617.1 (Kappa), and four VOCs, B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma) and B.1.617.2 (Delta), including the B.1.617.2 K417N, informally known as Delta Plus. We utilised the WHO International Standard for anti-SARS-CoV-2 Immunoglobulin to report neutralisation antibody levels in International Units per mL. Our data demonstrate a significant reduction in the ability of first wave convalescent sera to neutralise the VOCs. Patients and HCWs with more severe COVID-19 were found to have higher antibody titres and to neutralise the VOCs more effectively than individuals with milder symptoms. Using an estimated threshold for 50% protection, 54 IU/mL, we found most asymptomatic and mild cases did not produce titres above this threshold