The Zika virus in the maternal serum, possible evidence of infection of the foetus

A study carried out by professionals of Vall d'Hebron Barcelona Hospital Campus notes that the prolonged presence of the Zika virus RNA in maternal serum can be an indicator of infection of the foetus. A fact that, in turn, can play an important role in the continued presence of the virus in the mother. The work, led by Dr. Anna Suy, associate physician of the Perinatal Infections Unit of the Obstetrics Service at Vall d'Hebron and one of the principal investigators of the research group in Maternal and Foetal Medicine at Vall d'Hebron Research Institute (VHIR), is published by the magazine New England Journal of Medicine.

The research focuses on the case of a pregnant woman infected in one of the countries of South America affected by the Zika virus epidemic during week 9 of gestation. She suffered a rash on the trunk and extremities, and tested positive for Zika in serum samples PCR RNA Zika virus. The positive result remained for 89 days, i.e. 107 days after the onset of symptoms, at week 29 of gestation. Tests on urine, vagina and endocervix were negative.

Ultrasound tests conducted at week 12 and 15 of gestation revealed no abnormalities in the foetus. Instead, neurosonografías made from week 20, did show problems in brain development. These indications were confirmed through the MRI tests performed. The foetus showed no other abnormalities. The PCR RNA Zika virus tests in amniotic fluid were positive. In fact, the viral load in the sample of amniotic fluid was higher than the viral load in maternal serum.

The delivery took place the 37th week of pregnancy. At this time, RNA PCR testing in maternal serum, urine, amniotic fluid, placenta, membranes and umbilical cord were negative. The newborn, who had microcephaly, also was negative in all tests.

Feedback between the placenta and the mother

The signatories of the study indicate that the data confirm previous studies indicating the possibility that the continued presence of the Zika virus in the blood of the mother can be attributed to its replication in the foetus or placenta. To do this, they are based on three aspects. First, the fact that the viral load in the amniotic fluid was higher than the maternal serum. Second, that the virus is kept stable in maternal blood for 14 weeks go down suddenly and not gradually, and finally to the presence in the blood simultaneously with neutralized antibodies and viral RNA. At the same time, another indicator is that no virus RNA was detected in the urine of the mother, contrary to what is indicated by the current literature.

Finally, the authors suspect that the negative results in their PCR tests indicate that neonatal infection occurred during prenatal life, therefore it is possible that the immune system was able to develop antibodies to Zika before birth.

Participants in the study are Dr. Anna Suy, Dr. Elena Sulleiro of the Microbiology Service, Dr. Carlota Rodó, from the Obstetrics Service, Dr. Élida Vázquez, Head of Department of Paediatric Radiology, Dr. Cristina Bocanegra and Dr. Israel Molina, of the Infectious Diseases and PROSICS, Dr. Juliana Esperalba of the Microbiology Service, Dr. Paz Sánchez-Seco, from the National Centre for Microbiology, Dr. Hèctor Boix, from the Neonatology Service, Dr. Tomàs Pumarola, Head of the Microbiology Service, and Dr. Elena Carreras, Head of the Obstetrics Service. All of them are also researchers from different groups of VHIR.

Vall d'Hebron Barcelona Hospital Campus

The Vall d'Hebron Campus consists of the Vall d'Hebron University Hospital, Vall d'Hebron Research Institute (VHIR), the Vall d'Hebron Institut of Oncology (VHIO) and the Centre for Multiple Sclerosis of Catalonia (Cemcat). The new projected represents a new way of working and do, where research, teaching and clinical practice walk together in the same direction, to join efforts and grow, be more useful, more productive and more effective.