- During pregnancy, a woman's immunity is naturally suppressed so
that her body does not mount an immune response and reject the fetus,
which may be perceived as a foreign entity.
- Zika virus infection further lowers already weak immunity, thus
enabling the virus to spread and cause serious harm to the fetus.
virus infection in pregnancy is particularly serious since the organism
severely suppresses the mother's already weak immune system (almost similar to
HIV), helping the virus to multiply and spread, thereby increasing the risk of
harm to the fetus with resultant birth defects.
current study was conducted by the Keck School of Medicine of USC under
Dr Jae Jung, Distinguished Professor and chair of the Department of Molecular
Microbiology and Immunology at the Keck School of Medicine and the findings
appear in Nature Microbiology
in August 2017.
‘Mosquito borne illnesses are on the rise due to global warming and climate change and need to be urgently addressed to protect the health of the population, especially the pregnant woman and the fetus.’
Clinical Trials Have Not Included Pregnant Women - Correcting This Lapse
One of the main reasons that lots of funds and effort is being
invested in Zika virus research and vaccine development is because of the
severe harm it causes to the fetus during pregnancy
. However, none of the
Phase I clinical trials have included pregnant women, which is rather
surprising according to senior author Dr Jung.
"The Zika virus vaccines in
development seem to be highly effective, but they are being tested among
non-pregnant women with different body chemistry compared to pregnant
women," Jung said. "It's feasible the recommended vaccine dose -- though
effective for non-pregnant women -- may not be potent enough for pregnant women
because their bodies are more tolerant of viruses."
The Zika Virus In Blood Samples Of Pregnant Women
The research team tested the effects of
African and Asian Zika virus strains in blood samples of healthy men,
non-pregnant women and pregnant women between 18-39 years. The blood samples
were analyzed when the infection was at the peak.
- The study included
the blood of 30 pregnant patients
(10 from each trimester) diagnosed
with the Asian Zika virus
- The virus was seen to target the CD14 surface marker
positive blood monocytes (a type of white blood cell) which transform to macrophages in
the tissues of the body under appropriate conditions. These cells are
essentially scavenging cells that swallow viruses, bacteria and cellular
debris and ensure that the infection is overcome and body remains healthy.
- The virus promotes the conversion of these white cells to M2
macrophages which indicate to the immune system that the threat is over
and turns down the immunity allowing the immune system to relax.
- This false M2 signal to the immune system enables the Zika virus to
rapidly replicate and spread and cause serious maternal and fetal
harm; the levels of immunity suppressing M2 macrophages is already high in
a pregnant woman (to prevent rejection of the fetus) and Zika virus
infection further incapacitates the already weak immunity.
- The Asian Zika virus strain was found to be much more malicious than
the African strain. The African Zika virus strain suppressed the
immunity by about 10 percent. On the contrary, for expectant mothers
infected by the Asian Zika virus, nearly 70 percent of the immune system
- The Asian strain's immunosuppressive effect was
significantly higher in the first and second trimester of pregnancy in
comparison to non-pregnant women. However in the third trimester, the
effect on the blood of pregnant versus non-pregnant women remained the
Earlier studies by others have shown that
Zika virus infection during the first and second trimesters of pregnancy is associated
with increased incidence of fetal abnormalities.
Of The Study
- The blood samples of infected
pregnant women showed markedly
higher expression of the ADAMTS9 and FN1 genes, known to be associated
with pregnancy complications, namely underweight newborns and prolonged or
complicated baby delivery by hyper expression of ADAMTS9 gene and uterine
abnormalities leading to unusually small babies and pre-eclampsia (high
maternal blood pressure) by increased FN1 gene expression.
- The findings of the study establish
the known fact that Zika virus
infection in Pregnancy,
especially in the first and second trimesters is serious both for the
mother and the baby.
- The study highlights the importance of controlling mosquito
borne diseases which are on the rise and can cause severe maternal and
fetal mortality and morbidity.
Though fetal microcephaly (small fetal
head) has been reported widely leading to brain damage, other equally grave
birth defects have been reported such as formation
of calcium clumps in the brain of newborns
that results in brain damage and
developmental delays, underscoring the need
for urgent preventive and control measures to limit spread of Zika virus
In conclusion, Dr Suan-Sin Foo, lead
author of the study and a research associate in the Jae Jung Lab opines that
the findings of the current study should be an eye opener to initiate appropriate
measures to protect the health of the pregnant woman and the fetus from this