TeachableMedicalNews article 03202020

Teachable moment in classrooms:

  1. cellular basis of life chapter – receptor mediated endocytosis
  2. cellular basis of life chapter – fusion of endosome with lysosome
  3. cellular basis of life chapter – enzymes inside the lysosome require low pH
  4. microbiology – coronaviruses receptors on cell membranes
  5. microbiology – coronaviruses and their release into the cytoplasm

The news item:  A possible treatment of COVID 19 patients made the news recently:

Chloroquine, an old malaria drug, may help treat novel coronavirus, doctors say

According to early research, an old malaria drug called chloroquine might also work for the new coronavirus.

The article mentions the drug chloroquine, and that it blocks the attachment of the virus to cultured cells.  This latter point is inaccurate, so read on to find out the truth.

So, Why Do I Care??  Have you been living under a rock in the last two months??? The coronavirus, SARS-CoV-2, responsible for the COVID 19 disease has so far infected over 200,000 people, and caused over 10,000 deaths worldwide.   The virus attacks the respiratory system, and it may cause pneumonia and respiratory failure. The drug chloroquine and hydroxychloroquine hold promise as a possible treatment to lower the intensity, and perhaps, the mortality of the virus.

Plain English, Please!!! First, let’s look at what it takes for SARS-CoV-2 virus to infect our cells. This coronavirus, like all other viruses, must use the resources (nutrients, energy, enzymes) of the host cell to make new infectious viruses.  The infection has two parts to it.  Part 1 is the virus getting into the cell, and so, the virus sticks to the cell, like a Velcro ball sticks to the Velcro-covered paddle in a toss-and-catch yard game. Then the virus is pulled into the cell inside a microscopic bag called the endosome.  Part 2 is to release the genetic material of the virus from the endosome into the cell, and that gives the virus control of the resources of the host cell.

Second, let’s look at what chloroquine does to our cells. Chloroquine moves into our cells, and gets trapped inside the endosomes and in the organelles called lysosomes.  Endosomes and lysosomes naturally have low (acidic) pH, but after chloroquine accumulates inside, the pH value rises, and the endosomes and lysosomes become less acidic inside.

Third, let’s look at why chloroquine blocks infection of our cells. As it turns out coronaviruses need that acidic pH in the endosome and lysosome for part 2 of the infection.  When the virus is inside the endosome, the genetic material of the virus is still wrapped inside its own envelope.  Imagine the virus as burrito where the tortilla wrap is the envelope, and the filling of the burrito is the genetic material of the virus. The acidic pH helps to break open the tortilla, and to push the burrito filling into the rest of the cell.  The burrito filling then in the perfect place to hijack the cell resources and forces the cell to make new coronaviruses.  The chloroquine-filled endosome and lysosome no longer has an acidic pH, so the tortilla is not broken up, so the genetic material cannot be released inside the cell, so the cell cannot be hijacked.  And by that the coronavirus infection is defeated.

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