canping-huang-phd-novel-virus-discovery-in-bat-isn-translation

The bat immune system is still not clearly understood. Being one of the earliest mammals
to evolve, the immune reaction of bats, both innate and adaptive, is recognizably different
from those of Glires and primates. Researchers are interested in changes to the bat immune
system during torpor and hibernation. Based on research on other mammals, hibernation
impacts the innate and adaptive immune system. It is assumed that the immune system of
bats is weakened during rest. Immunosuppression is common during hibernation. It is
beneficial for host energy preservation. Meanwhile, as most viruses have difficulty
replicating at low temperatures, the possibility of infection is low. Currently, the study of
bat immunology mostly focuses on orthologous genes that are shared with humans and
small rodents. The role these genes play in the innate immune system is critical. They
include interferon [166-168] , cytokine [169] , Toll like receptor [170] , STAT1 protein [171] and so
forth. Some research also focuses on their structure and function [172] . Research indicates
that the immune response of bats and of other animals that evolved later share some
similarity. For instance, Immunoglobulin G (IgG antibody), IgA and IgM can be purified
from the serum of the great fruit-eating bat Artibeus lituratus [173] . Macrophages, B-
lymphocytes, T- lymphocytes, and cells expressing surface Ig were found in the bone
marrow of Pteropus giganteus. These results suggest the evolution of lymph in bats and
other mammals was similar [174, 175] . Despite the findings from these gene comparison
studies, there are still slight differences between bats and other mammals, thus it is too
early to come to firm conclusions.
Bats have some distinct characteristics from the perspective of biology and ecology. These
make them the ideal host for viruses in the wild: 1. Bats are the oldest mammals. Viruses
that evolve in the body of bats can make use of highly conserved cell receptors to enhance
the transmission of viruses to other mammals. 2. Bats are the most widely distributed
group of mammals except humans. This provides a large “breeding ground” for viruses.
Diverse roosting sites and food sources, and the ability to travel long distances (some bats
can migrate several hundred kilometers to a hibernation site), create many opportunities
for bats to interact with other species at numerous different locations. This increases the
chance of cross-species transmission. 3. Bats live in multi-species groups. These high
densities facilitate the jumping of viruses from one bat species to another. This promotes
both virus longevity and virus attenuation. 4. Bats have a long life expectancy. Some bats
can live up to 25-35 years, which prolongs the potential timeframe of viral transmission.
Some bats are able to hibernate in wintertime and undergo daily torpor in other seasons,
both of which can lower energy consumption, body temperature and rate of metabolism.
Low body temperature and rate of metabolism slow down the growth of viruses inside the
bats.
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A partial translation into English of the PhD thesis: “Novel Virus Discovery in Bat and the Exploration of
Receptor of Bat Coronavirus HKU9” by Canping Huang, Chinese Center for Disease Control and Prevention,
2016. Translation completed for Independent Science News in March 2021.