UPDATE: It seems that SARS Cov II might bind to other receptors than just the previously thought ACE2.
"COVID-19, the novel coronavirus disease caused by SARS-CoV-2 and outbroken at the end of 2019 in Wuhan, China,1 becomes a worldwide pandemic. SARS-CoV-2 belongs to the betacoronavirus genus and has 79.5% identity to SARS-CoV. SARS-CoV-2 uses angiotensin-converting enzyme 2 (ACE2) as its host entry receptor.
2 The clinical manifestations of COVID-19 include pneumonia, diarrhea, dyspnea, and multiple organ failure. Interestingly, lymphocytopenia, as a diagnostic indicator, is common in COVID-19 patients. Xiong et al. found upregulation of apoptosis, autophagy, and p53 pathways in PBMC of COVID-19 patients.3 Some studies reported that lymphocytopenia might be related to mortality, especially in patients with low levels of CD3+, CD4+, and CD8+ T lymphocytes.4,5 Lymphocytopenia was also found in the Middle East respiratory syndrome (MERS) cases.
MERS-CoV can directly infect human primary T lymphocytes and induce T-cell apoptosis through extrinsic and intrinsic apoptosis pathways, but it cannot replicate in T lymphocytes.
6 However, it is unclear whether SARS-CoV-2 can also infect T cells, resulting in lymphocytopenia.
To address this question, we evaluated the susceptibility of T lymphocytes to SARS-CoV-2 infection."
SARS-CoV-2 infects T lymphocytes through its spike protein-mediated membrane fusion
from 12 Apr
‘Renting is cheaper than buying’ as Covid-19 batters Hong Kong property
from Jan / Feb 2020
Reduction and Functional Exhaustion of T Cells in Patients with Coronavirus Disease 2019 (COVID-19)
This might explain previous observations re.
1. Covid19 attacking the immune system - early discussion of similarity to HIV (Feb) - NOTE: this is not saying the Cov19 virus has spliced HIV sequences!
2. Covid19 attacking other organs - liver, heart
3. Covid19 attacking blood cells - discussions suggesting it is a blood rather than a respiratory disease.
4. Covid19 being worse for the immune depressed
5. Why HIV antivirals have been effective treatments
6. Why Anti-malaria drugs are effective treatments
New studies suggest that other protein binding (CD147) binding takes place which allows for Covid to attack T-cells.
What does this all mean?
It is a possible explanation as to why the effects of Covid19 are so varied and why it spreads so quickly.
Hopefully there will be more discussions about this in the coming days.
EDIT: reddit discussion