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 Table of Contents  
JOURNAL SCAN
Year : 2021  |  Volume : 11  |  Issue : 4  |  Page : 192-194

Perinatal transmission of SARS-CoV-2 antibodies and the risk of infection


1 Department of Pediatrics, Sir Ganga Ram Hospital, New Delhi, India
2 Department of Obstetrics and Gynecology, Sir Ganga Ram Hospital, New Delhi, India

Date of Submission05-Aug-2021
Date of Decision08-Aug-2021
Date of Acceptance09-Aug-2021
Date of Web Publication21-Aug-2021

Correspondence Address:
Dinesh Kaul
Department of Paediatrics, Institute of Child Health, Sir Ganga Ram Hospital, Rajinder Nagar -110 060
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/cmrp.cmrp_78_21

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How to cite this article:
Kaul D, Gujral K. Perinatal transmission of SARS-CoV-2 antibodies and the risk of infection. Curr Med Res Pract 2021;11:192-4

How to cite this URL:
Kaul D, Gujral K. Perinatal transmission of SARS-CoV-2 antibodies and the risk of infection. Curr Med Res Pract [serial online] 2021 [cited 2021 Dec 8];11:192-4. Available from: http://www.cmrpjournal.org/text.asp?2021/11/4/192/324258


  Article Information Top


Poon LC, Leung BW, Ma T, Yu FN, Kong CW, Lo TK, et al. Relationship between viral load, infection to delivery interval and mother-to-child transfer of anti-SARS-CoV-2 antibodies. Ultrasound Obstet Gynecol 2021;57:974-8.

Published online on 02 April 2021 in Wiley Online Library (wileyonlinelibrary.com). https://doi. org/10.1002/uog0.23639.


  Background Top


Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection can affect all adults and children including pregnant and lactating women. In pregnant women, there is an increased risk of severe illness, various complications such as acute respiratory distress syndrome, need for ventilatory support and thromboembolic phenomenon can occur which may be detrimental. There is an increased risk of preterm births and other unfavourable outcomes related to pregnancy. The risk of perinatal transmission of infection to the neonate is possible during initial acute viral replicative phase of the illness.[1]

A co-relation between the duration of illness during pregnancy and the antibody response evoked over that time period has not been studied. It may be assumed that a higher viral load during pregnancy may lead to an increased risk of perinatal transmission in the neonate.

Women who are infected about 6–8 weeks prior to delivery will evoke a good SARS-CoV-2 IgG antibody response and thus, the perinatal transmission may be reduced. In contrast, women who acquire infection in 7–10 days before delivery have a shorter IgG response and less transfer of antibodies across the placental barrier.

The protection from infection for neonates is thought to be primarily dependent on the neonatal innate immune response and transplacental transfer of maternal IgG antibodies.


  Summary of the Study Top


In the backdrop of this question, the authors investigated SARS-CoV-2 viral load and infection-delivery interval with various anti-SARS-CoV-2 IgG levels measured in the maternal blood and cord blood samples of the neonates. The authors in this prospective case series study conducted across various hospitals in Hong Kong evaluated data of 20 women who had delivered from 27 March 2020 to 24 January 2021. In this duration of over 10 months, 14 women had recovered from COVID-19 and 6 had active infection at the time of delivery. All the women had evidence of confirmed SARS-CoV-2 infection (positive nasopharyngeal swabs or deep throat swabs/saliva SARS-CoV-2 reverse transcriptase–polymerase chain reaction (RT-PCR) test with serial cycle threshold, i.e. CT value). IgG and IgM estimation for SARS-CoV-2 antibodies was done in maternal and cord blood samples. The detection of antibodies directed against nucleocapsid and spike proteins was measured by special assays developed by Roche Diagnostics on a Cobas® e411 analyser and an ELISA kit from Immunodiagnostics Ltd., Hong Kong, respectively.

In addition to the antibody measurement, various parameters such as maternal viral load, CT values, infection to delivery interval, infection duration and gestational age at the time of diagnosis were measured. Transplacental transfer of antibodies ratio of IgG among maternal and cord samples was estimated for all pregnant women who had recovered or had active infection at the time of delivery.

Data analysis of the participants revealed that the median maternal age was 35.5 (interquartile range, 31–38.8) years and median gestational age of clinical manifestations was 32.7 (11.9–39.4) weeks. The median infection to delivery interval was 41.5 days (2–187 days) and the infection duration was 10 (1–48) days. The median gestational age at the time of delivery was 39.1 (32.4–40.7) weeks and the median seroconversion interval was 14 (1–19) days.

The estimation of anti-SARS-CoV-2 antibodies (qualitative and quantitative methods) in 20 women revealed seropositive status in 15 (75%); 2 women had active infection and 13 had recovered from infection.

It was evident from the study that the risk of perinatal transmission (mother to neonate) was negligible. There were 13 neonates born to seropositive mothers, who had recovered at the time of delivery. All the 13 neonates tested negative for SARS-CoV-2 RT-PCR test done on nasopharyngeal samples and none of the concordant cord blood samples had any detectable IgM antibodies; 12 neonates had detectable anti-SARS-CoV-2 IgG antibodies.

The transplacental transfer ratio of IgG was calculated as cord serum IgG concentration divided by maternal serum IgG concentration. The median transplacental transfer ratio of IgG antibodies between the maternal and cord sera samples was 1.3 (0.9–1.6). It was observed that there was no co-relation between infection-to-delivery interval and anti-SARS-CoV-2 IgG concentration in maternal and cord sera. However, it was observed that there was a positive co-relation between IgG concentration in maternal serum and the viral load AUC (area under the curve); r = 0.5109, P = 0.0310). A negative co-relation was observed between transfer ratio and viral load AUC; r = −0.4757, P = 0.0409.

The authors concluded that in pregnant women who had recovered from the infection, anti-SARS-CoV-2 IgG antibodies at the time of delivery increased with the detectable viral load during the duration of pregnancy. The antibodies decreased with an increase in the duration of infection to delivery interval.


  Commentary Top


This study has highlighted some pertinent aspects regarding the perinatal transmission of SARS-CoV-2 infection. It seems that women who are infected in first or second trimester of pregnancy evoke a good immune response in terms of production of IgG antibodies against various proteins of the virus.

One of the important observations of this study was seen in pregnant women who had recovered from COVID-19. Higher viral load during the infection and shorter infection-to-delivery interval correlated with higher anti-SARS-CoV-2 IgG concentrations in maternal serum at delivery. The median transplacental transfer ratio of anti-SARS-CoV-2 IgG antibodies was 1.3 and it decreased with increasing viral load AUC. The viral load AUC indicates the total quantum of viruses shed over the duration of infection. It was also observed that the IgG concentration was higher in the cord blood as compared to the maternal blood. This is true for other viral infections such as measles, HIV and CMV.[2],[3]

In a similar study conducted among 72 mother/neonate dyads (who were seropositive at the time of delivery), it was observed that the transfer ratio of anti-SARS-CoV-2 IgG correlated positively with the interval between the onset of infection and delivery.[4] This is in contrast to the study under review where no significant change in transplacental transfer ratio was observed with increasing infection to delivery interval. The exact molecular mechanisms responsible for the transplacental transfer of IgG antibodies in SARS-CoV-2 infection would be an interesting aspect of research; FcR glycosylation in trophoblastic cells and increased expression of FCGR3A may be an important factor in this process.[5]

The authors conclude that high viral load during SARS-CoV-2 infection is associated with a higher concentration of SARS-CoV-2 IgG antibodies in recovered mothers; however, it does not affect the transplacental transfer of IgG antibodies to the foetuses. The neonates are unlikely to be infected.

The impact of vaccines on perinatal transmission needs to be studied as various COVID-19 vaccines have been approved in pregnant women. The vaccine-induced immune response is likely going to change the scenario of mother-to-baby transfer of anti-CoV-2 IgG.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Pregnant and Recently Pregnant People. CDC. Available from: https://www.cdc.gov>2019-ncov. [Last accessed on 2021 Jul 24].  Back to cited text no. 1
    
2.
Gonçalves G, Cutts FT, Hills M, Rebelo-Andrade H, Trigo FA, Barros H. Transplacental transfer of measles and total IgG. Epidemiol Infect 1999;122:273-9.  Back to cited text no. 2
    
3.
Martinez DR, Fong Y, Li SH, Yang F, Jennewein MF, Weiner JA, et al. Fc characteristics mediate selective placental transfer of IgG in HIV-infected women. Cell 2019;178:190-201.e11.  Back to cited text no. 3
    
4.
Flannery DD, Gouma S, Dhudasasia MB, Mukhopadhya S, Pfeifer MR, Wordford EC, et al. Maternal and neonatal cord blood SARS-CoV-2 antibodies and placental transfer ratio. JAMA Pediatr 2021. [doi: 10.1001/jamapediatrics. 2021.0038].  Back to cited text no. 4
    
5.
Atyeo C, Pullen KM, Bordt EA, Fischinger S, Burke J, Michell A, et al. Compromised SARS-CoV-2-specific placental antibody transfer. Cell 2021;184:628-42.e10.  Back to cited text no. 5
    




 

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