Seroprevalence of SARS-CoV-2 immunoglobulins in pregnant women and neonatal cord blood from a highly impacted region

COVID-19 IgG seropositivity and its determinants in occupational groups of varying infection risks in two Andean cities of Ecuador before mass vaccination

BACKGROUND

The COVID-19 pandemic has caused over 68.7 million infections and 1.35 million deaths in South America. There are limited data on SARS-CoV-2 seropositivity and its determinants from Andean countries prior to mass vaccinations against COVID-19.

OBJECTIVE

To estimate SARS-CoV-2 seropositivity and its determinants before vaccination in occupational groups of adults presumed to have different levels of exposure and associations with potential symptomatology.

METHODS

We measured seropositivity of anti-SARS-CoV-2 IgG antibodies in a cross-sectional study of vaccine-naïve adults aged 18 years and older, recruited within three occupational risk groups (defined as low [LR], moderate [MR], and high [HR]) between January and September 2021 in two Andean cities in Ecuador. Associations with risk factors were estimated using logistic regression.

RESULTS

In a sample of 882 adults, IgG seropositivity for the three different occupational risk groups was 39.9% (CI 95% 35.3-44.6), 74.6% (CI 95% 66.4-81.4), and 39.0% (CI 95% 34.0-44.4) for the HR, MR, and LR groups, respectively. History of an illness with loss of taste and/or smell was significantly associated with seropositivity in all occupational groups, with adjusted ORs of 14.31 (95%CI, 5.83-35.12; p<0.001), 14.34 (95%CI 3.01-68.42; p<0.001), and 8.79 (95%CI 2.69-28.72; p<0.001), for the HR, MR, and LR groups, respectively; while fever was significant for the LR group with an adjusted OR of 1.24 (95%CI, 1.11-4.57; p = 0.025) and myalgia for the HR group with an adjusted OR of 2.07 (95%CI, 1.13-3.81; p = 0.019).

CONCLUSION

Notable proportions of seropositivity were seen in all occupational groups between January and September 2021 prior to mass vaccination. Loss of taste and/or smell was strongly associated with presence of anti-SARS-CoV-2 IgG antibodies irrespective of presumed occupational exposure risk.

Seroprevalence and placental transfer of SARS-CoV-2 antibodies in unvaccinated pregnant women

PURPOSE

Pregnant women are at risk of severe SARS-CoV-2 infection, potentially leading to obstetric and neonatal complications. Placental transfer of antibodies directed to SARS-CoV-2 may be protective against neonatal COVID-19, but this remains to be studied. We aimed to determine the seroprevalence of SARS-CoV-2 antibodies in a population of unvaccinated pregnant women and to determine the placental transfer of these antibodies.

METHODOLOGY

A total of 1197 unvaccinated women with mostly unknown pre-study SARS-CoV-2 infection status, were tested at delivery for SARS-CoV-2 spike protein IgG antibodies during the first year of the pandemic. Umbilical cord samples were collected and assessed for seropositivity if the mother was seropositive. Maternal characteristics, pregnancy and neonatal outcomes and data on SARS-CoV-2 infection were extracted from medical records.

RESULTS

Specific IgG were detected in 258 women (21.6%). A significant placental transfer to the newborn was observed in 81.3% of cases. The earlier in the 2nd and 3rd trimesters that the mother had contracted the disease and the more symptomatic she was, the greater the likelihood of transplacental transfer of IgG to her newborn.

CONCLUSION

Approximately one in five women had detectable anti-SARS-CoV-2 spike protein IgG antibodies at delivery during the first year of the pandemic, and these antibodies were significantly transferred to their fetuses. This research provides further evidence to better understand the dynamics of the placental transfer of SARS-CoV-2 IgG antibodies from mothers to their newborns, which is necessary to improve vaccination strategies.

The dynamics and determinants of specific systemic and mucosal antibody responses to SARS-CoV-2 in three adult cohorts in the Ecuadorian Andes: a study protocol

Introduction

There are limited longitudinal data on the systemic and mucosal antibody responses to SARS-CoV-2 from Latin America, a region severely affected by COVID-19, and where vaccine strategies have been implemented during the evolving pandemic.

Objective

To evaluate determinants of seroprevalence and changes in levels of anti-SARS-CoV-2 antibodies longitudinally in adults with different levels of exposure to SARS-CoV-2 (defined a priori as low, medium, and high based on presumed occupational risk), in two Andean cities in Ecuador.

Methods

Longitudinal cohort study of 1,000 adults aged 18 years and older with questionnaire data and sample collection done at 0, 3, 6, and 12 months during the period 2020-2023. Observations collected included WHO-ISARIC questionnaire and peripheral blood and saliva samples for measurement of IgG and IgA antibodies, respectively. Planned analyses are tailored to the longitudinal nature of the outcomes defined by participants' antibody levels and aim at estimating their average trends with time since infection in each of the occupational groups, adjusted for demographics and calendar-time levels of SARS-CoV-2 infection in the general population. The latter reflect the impact of the national control measures such as vaccinations and movement restrictions.

Importance

Understanding the duration and the dynamics of waning immunity to SARS-CoV-2, in the context of exposures to emerging virus variants and immunization, will inform the implementation of targeted public health strategies in the Latin American region.

Ethics and Dissemination

This study will observe the bioethical principles of the Declaration of Helsinki. Informed written consent will be obtained. Samples from participants will be stored for up to three years after which they will be destroyed. The study protocol was approved by the Ecuadorian Ministry of Public Health Ethics Committee for COVID-19 Research. Antibody results will be provided to participants and participating institutions and to the national health authorities.

Serologic evolution and follow-up to IgG antibodies of infants born to mothers with gestational COVID

BACKGROUND

It is known that SARS-CoV-2 antibodies from pregnant women with SARS-CoV-2 infection during pregnancy cross the placenta but the duration and the protective effect of these antibodies in infants is scarce.

METHODS

This prospective study included mothers with SARS-COV-2 infection during pregnancy and their infants from April 2020 to March 2021. IgG antibodies to SARS-CoV-2 spike protein were performed on women and infants at birth and at two and six months during follow-up. Anthropometrical measures and physical and neurological examinations and a clinical history of symptoms and COVID-19 diagnosis were collected. Simple linear regression was performed to compare categorical and continuous variables. To compare the mother's and infant's antibody titers evolution, a mixed linear regression model was used. A predictive model of newborn antibody titers at birth has been established by means of simple stepwise linear regression.

RESULTS

51 mother-infant couples were included. 45 (90%) of the mothers and 44 (86.3%) of the newborns had a positive serology al birth. These antibodies were progressively decreasing and were positive in 34 (66.7%) and 7 (13.7%) of infants at 2 and 6 months, respectively. IgG titers of newborns at birth were related to mothers' titers, with a positive moderate correlation (Pearson's correlation coefficient: 0.82, p < 0,001). Fetal/maternal antibodies placental transference rate was 1.3 (IQR: 0.7-2.2). The maternal IgG titers at delivery and the type of maternal infection (acute, recent, or past infection) was significantly related with infants' antibody titers at birth. No other epidemiological or clinical factors were related to antibodies titers. Neurodevelopment, psychomotor development, and growth were normal in 94.2% of infants in the third follow-up visit. No infants had a COVID-19 diagnosis during the follow-up period.

CONCLUSIONS

Transplacental transfer of maternal antibodies is high in newborns from mothers with recent or past infection at delivery, but these antibodies decrease after the first months of life. Infant's IgG titers were related to maternal IgG titers at delivery. Further studies are needed to learn about the protective role of maternal antibodies in infants.

Single-center serological surveillance of SARS-CoV-2 in pregnant patients presenting to labor and delivery

OBJECTIVE

To measure maternal/fetal SARS-CoV-2 antibody levels.

METHODS

A prospective observational study of eligible parturients admitted to the hospital for infant delivery was conducted between April and September 2020. SARS-CoV-2 antibody levels were measured in maternal and umbilical cord specimens using an in-house ELISA based on the receptor-binding domain (RBD) of the spike protein. Among SARS-CoV-2 seropositive patients, spike RBD antibody isotypes (IgG, IgM, and IgA) and ACE2 inhibiting antibodies were measured.

RESULTS

In total, 402 mothers were enrolled and spike RBD antibodies in 388 pregnancies were measured (336 maternal and 52 cord specimens). Of them, 19 were positive (15 maternal, 4 cord) resulting in a seroprevalence estimate of 4.8% (95% confidence interval 2.9-7.4). Of the 15 positive maternal specimens, all had cord blood tested. Of the 15 paired specimens, 14 (93.3%) were concordant. Four of the 15 pairs were from symptomatic mothers, and all four showed high spike-ACE2 blocking antibody levels, compared to only 3 of 11 (27.3%) from asymptomatic mothers.

CONCLUSION

A variable antibody response to SARS-CoV-2 in pregnancy among asymptomatic infections compared to symptomatic infections was found, the significance of which is unknown. Although transfer of transplacental neutralizing antibodies occurred, additional research is needed to determine how long maternal antibodies can protect the infant against SARS-CoV-2 infection.

Maternal-foetal transfer of severe acute respiratory syndrome coronavirus 2 antibodies among women with and those without HIV infection

In pregnant women, antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein cross the placenta and can be detected in cord-blood at the time of delivery. We measured SARS-CoV-2 full-length antispike IgG in blood samples collected from women living with HIV (WLWHIV) and without HIV when presenting for labour, and from paired cord-blood samples. Antispike IgG was measured in maternal blood at delivery on the Luminex platform. Cord-blood samples from newborns of women in with detectable antispike IgG were analysed. The IgG geometric mean concentrations (GMCs) and the percentage of cord-blood samples with detectable antispike IgG were compared between WLWHIV and without HIV. A total of 184 maternal and cord-blood pairs were analysed, including 47 WLWHIV and 137 without HIV. There was no difference in antispike GMCs between WLWHIV and without HIV [157 binding antibody units (BAU)/ml vs. 187 BAU/ml; P  = 0.17)]. Cord-blood samples from newborns of WLWHIV had lower GMCs compared with those without HIV (143 vs. 205 BAU/ml; P  = 0.033). Cord-to-maternal blood antibody ratio was 1.0 and similar between the two HIV groups. In WLWHIV, those who were 30 years old or less had lower cord-to-maternal blood antibody ratio (0.75 vs. 1.10; P  = 0.037) and their newborns had lower cord-blood GMCs (94 vs. 194 BAU/ml; P  = 0.04) compared with the older women. Independently of maternal HIV infection status, there was efficient transplacental transfer of antispike antibodies. The GMCs in cord-blood from newborns of WLWHIV were lower than those in HIV-unexposed newborns.