Measles
has been on the rise globally. In 2019 there was a 300% global increase in
measles cases from January-March [1]. Measles is an ever growing problem worldwide, and recently it has been shown
that measles can weaken the immune system of any person who becomes infected.
In 2012 the World Health Organization created a plan called the Global Vaccine
Action Plan (GVAP). GVAP was tasked with eliminated measles in different
regions in the world with the goal of measles elimination by 2020 [2]. This plan is now
appearing to be more important than ever after papers such as Mina et al.
(2019) show further immune system deficits after measles virus infection. This
study studies blood plasma from a region in the Netherlands that had low
vaccination rates. The blood plasma was collected before and after patients had
been infected with the measles to study the change in antibodies. An antibody
is a protein that is part of the immune system. It can identify harmful
substances, generally called antigens (ie viruses and bacteria), and then
initiate an immune response to neutralize the invading particle [3].
After a person has been exposed to an antigen, either through infection or a
vaccine, the body creates memory cells which can target a single antigen to identify
and kill it. These memory cells remain circulating in the body after the
infection is gone so that if that antigen is to re-enter the body, the patient
does not get infected again by the same disease [4].
Mina et al. (2019) shows that it is these memory cells of the immune system
that get destroyed after measles virus infection, meaning that if a person was
infected with measles they would be at risk for other diseases they have
previously had (ie. chicken pox).
After
the blood plasma was collected VirScan was used. VirScan detects antibodies
that are present in the blood plasma and allows those to be sequenced to
determine what these antibodies are designed to specifically target.
Additionally they looked at the antibody epitope binding signal (EBS) which is
a measure of antibody concentration for each epitope. An epitope is the part of
the antigen that binds directly to the antigen, making it the part of the
antigen that dictates its specificity. Figure 1 shows the antibody
restructuring that occurs after measles infection. There is a decrease of ~20%
in antibody diversity after mild and severe measles infection (1B). After
measles vaccine however there is an increase in antibodies that target measles
and no other changes (1C). Figure 2A further shows a loss of epitopes after
infection. They found that the retained portion of the antibody repertoire
could represent a portion of B cells, which are the cells in the immune system
that produce antibodies, called long lived plasma cells (LLPC). Therefore,
measles, the authors suspect, is directly affecting the LLPCs because the
decrease in antibodies is too great to simply affect the body’s ability to
create new B cells.
 |
| Figure 1. shows changes in antibody diversity after measles infection |
 |
| Figure 2. Shows the amount of antibodies that are kept post-measles infection. |
After
it was seen that measles decreases the antibodies, EBS was done to further
study the antibodies that are lost. EBS showed that the more severe the measles
the greater the loss of immune memory is. Additionally, throughout all patients
with measles, the changes to the immune system were consistent. This shows that
measles is not somehow causing random death of some of these LLPCs, but instead
is specifically targeting specific immune system memory cells. Again, these
changes were not seen after a patient had received the MMR (Measles, Mumps,
Rubella) vaccine.
Finally,
the authors infected rhesus macaque monkeys with measles and looked at the
decrease in overall antibody diversity. They saw a decrease of ~26% in their
antibody repertoire. This decrease lasted approximately 5 months. This is seen
in Figure 3A (Figure 5A in the published paper) where they did EBS to show how
much of each antibody for each specific disease was lost.
 |
| Figure 3. Shows the percentages of antibody that are lost after measles virus infection. |
In
conclusion, the measles virus can have dangerous effects on the infected
patients immune system increases susceptibility towards other diseases that the
patient has either previously had or has previously been vaccinated for. After
measles virus infection there is a significant decrease in antibody diversity
and antibody binding signals due to an overall decrease in the number of memory
cells in the immune system. The authors additionally acknowledged that their
research may not show the full extent of the antibody decrease because most
antibodies have a half life of three weeks meaning that these tests could have
additionally picked up antibodies that are lingering after the body destroyed
the bulk of the memory cells. Vaccines appear to be the only way to remedy this
problem as the vaccines do not cause any negative changes to the immune system
and appear to only increase the number of antibodies that target measles,
therefore only increasing antibody diversity. The vaccines can then prevent
measles infection and keep more of the population healthy.
Works Cited:
[1] World Health Organization, New measles surveillance data for 2019 (2019); www.who.int/immunization/newsroom/measlesdata-2019/en/.
[2] A. Dabbagh et al., MMWR Morb. Mortal. Wkly. Rep. 67, 1323–1329 (2018).
[3] Antibody: MedlinePlus Medical Encyclopedia. https://medlineplus.gov/ency/article/002223.htm. Accessed 5 Dec. 2019.
[4]Regenerative Medicine Partnership in Education. http://sepa.duq.edu/regmed/immune/memory.html. Accessed 5 Dec. 2019.
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