Natural Killer Cells Do Not Attenuate a Mouse-Adapted SARS-CoV-2-Induced Disease in Rag2-/- Mice.

This study investigates the roles of T, B, and Natural Killer (NK) cells in the pathogenesis of severe COVID-19, utilizing mouse-adapted SARS-CoV-2-MA30 (MA30). To evaluate this MA30 mouse model, we characterized MA30-infected C57BL/6 mice (B6) and compared them with SARS-CoV-2-WA1 (an original SARS-CoV-2 strain) infected K18-human ACE2 (K18-hACE2) mice. We found that the infected B6 mice developed severe peribronchial inflammation and rapid severe pulmonary edema, but less lung interstitial inflammation than the infected K18-hACE2 mice. These pathological findings recapitulate some pathological changes seen in severe COVID-19 patients. Using this MA30-infected mouse model, we further demonstrate that T and/or B cells are essential in mounting an effective immune response against SARS-CoV-2. This was evident as Rag2-/- showed heightened vulnerability to infection and inhibited viral clearance. Conversely, the depletion of NK cells did not significantly alter the disease course in Rag2-/- mice, underscoring the minimal role of NK cells in the acute phase of MA30-induced disease. Together, our results indicate that T and/or B cells, but not NK cells, mitigate MA30-induced disease in mice and the infected mouse model can be used for dissecting the pathogenesis and immunology of severe COVID-19.

DNA analysis reveals non-falciparum malaria in the Democratic Republic of the Congo.

BACKGROUND: The World Health Organization (WHO) attributes the entirety of malaria infection and transmission in the Democratic Republic of the Congo (DRC) to Plasmodium falciparum, one of the several species of malaria known to infect humans. Recent studies have put forth some evidence that transmission of Plasmodium vivax may also be occurring in the DRC. As interventions and treatments differ between malaria species, it is crucial to maintain the most accurate understanding of malaria species diversity in each region. METHODS: Blood samples were taken from aymptomatic children 0-5 years old living in three regions of the DRC in 2014. For this study, samples were taken from a larger pool of samples, collected as part of a population-based survey in three regions. Plasmodium infection was screened for using nested polymerase chain reaction (PCR) assays and species were confirmed by cloning and DNA sequencing. RESULTS: Of 336 samples screened by PCR, 62.2% (n=209) initially tested positive for P. falciparum and 14.6% (n=49) initially tested positive for P. vivax. Sanger sequencing was performed on PCR-positive Plasmodium samples to confirm identity of Plasmodium species. Sequencing showed Plasmodium malariae in one blood sample and Plasmodium ovale in another sample. Plasmodium vivax was detected in 12/65 cases (18.5%). Overall, 14/65 sequenced cases (21.5%) were infected with a non-falciparum malaria. 330bp 18s P. vivax DNA sequences were obtained. CONCLUSIONS: This study reveals Plasmodium vivax and other non-falciparum malaria across several regions of the DRC, and enforces the importance of further testing and more precise diagnostics when testing for and treating malaria in the DRC. Here, we find a higher proportion of cases of P. vivax malaria than found in previous studies. This is the most robust DNA sequencing of Plasmodium vivax in the DRC to date.