Malaria vaccine and pregnancy

Pregnant women are at highest risk of malaria in the adult group and they contribute to the majority of deaths due to malaria. In a way malaria and pregnancy can be considered as mutually aggravating conditions which increase the risk of complications for both the mother and the baby.

Malaria in pregnant women

• Both P. vivax and P. falciparum malaria pose problems for both the foetus and mother but the risk is higher and more serious with the latter.  Besides this, non- immune, primi-gravidae (first time pregnancy) are usually the most affected as compared to multigravida (second or more pregnancy).
• Some of the complications of malaria during pregnancy are anaemia, fever illness, hypoglycaemia, cerebral malaria, pulmonary edema, puerperal sepsis and mortality (death due to severe malaria).
• The common complications of malaria in newborns are low birth weight, prematurity, IUGR, malaria illness and mortality. The risk of spontaneous abortion is also high (can occur in up to 60% of cases).

Role of Placenta, the NEW ORGAN of pregnancy in malaria

Risks of complications due to malaria are probably increased during pregnancy due to the altered immunity and availability of a new organ called placenta during pregnancy. According to some experts placenta in the primi-gravidae is responsible for increased complications. Placenta is the organ which supports the embryo when it starts developing inside the womb. It helps to transport oxygen and nutrients from the mother to the baby and the waste products from the foetus to the mother’s blood. However, on the downside, it also allows the parasites to by-pass the immunity of the mother and  to access the foetus or allows P. falciparum to multiply causing complications in the mother and foetus.

P. falciparum has the ability to adhere to red blood cells which leads to the development of severe malaria in children and adults. During pregnancy, P. falciparum can adhere to the placenta using an adhesion molecule called chondroitin sulfate A and hyaluronic acid. This causes the parasite to sequester along the surface of the placental membrane, interfere with oxygen and nutrient transport to the foetus and cause complications experienced by both the mother and her baby. With repeated pregnancy such as in the case of multi-gravidae, the placenta specific immunity develops which prevents the bonding of infected red blood cells to the placenta and thus decreases the risk of complications.

Vaccine against malaria in pregnancy: Despite intensive research, a general malaria vaccine appears to be a distant possibility, but a vaccine against placental malaria can be expected in the near future. In pregnant woman, the severity of malaria (that is pregnancy-associated malaria or PAM) is probably related to the ability of parasitized red blood cells to bind to chondroitin sulfate A (CSA) present on the placenta. After several pregnancies, the mother develops protective antibodies which prevent the binding of the infected red blood cells to placenta. A potential vaccination strategy for pregnancy-associated malaria is to develop this protective immunity, which will prevent the binding of infected red blood cells to the placenta. A recent study has shown that administration of excessive soluble CSA to pregnant women can significantly reduce the binding of parasitized red blood cells to placenta. But an excess of soluble CSA protein is highly nephrotoxic. It has been noted that the administration of chondroitinase AC can effectively reduce parasite adhesion by 95%. Further studies are needed before an effective vaccine or therapeutic approaches aimed at protecting women during their first pregnancies as well as their unborn foetuses can be developed.

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