A recent study, currently available on the medRxiv* preprint server, is among the first to reveal the presence of antibodies against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in colostrum and to demonstrate elevated cytokine levels in colostrum from women exposed to the virus.
Current recommendations endorse breastfeeding for mothers infected with SARS-CoV-2, a causative agent of coronavirus disease (COVID-19), since the benefits of mother's milk are believed to outweigh potential risks of viral transmission to the infant.
Still, as the number of both pregnant and lactating women with SARS-CoV-2 increases, there is a dire need to expand limited yet existent research on immune response and specific antibodies in breast milk of infected women, but also in the colostrum (i.e., a nutrient-rich milky fluid produced in late pregnancy and few days after birth).
Available medical literature is pointing towards the conclusion that the transfer of cytokines via breast milk may indeed impact an infant's immune system, bestowing in turn protection against various allergies and infectious disease agents.
Furthermore, multiple studies to date have described a substantial increase in inflammatory cytokines in the bronchoalveolar lavage fluid and serum of COVID-19-infected individuals. Thus far, there are no published reports on the cytokine profiles in breast milk of women with COVID-19, we still cannot draw any parallels.
Consequently, researchers from the University of Massachusetts decided to appraise the presence of antibodies specific to SARS-CoV-2, as well as corresponding cytokines in colostrum from women who tested positive for the virus.
Antibodies and cytokines in colostrum
Between March and September 2020, the researchers obtained bilateral colostrum samples that were hand-expressed on spot cards within 48 hours of delivery from 15 new mothers who had previously tested positive for SARS-CoV-2, as well as one new mother who previously tested negative.
Furthermore, six participants also provided liquid bilateral colostrum (i.e., 5-10 milliliters from each breast into the container) within two days after providing the spot card samples. For comparison purposes, archived bilateral colostrum samples that were collected from 8 women (in the period between 2011 and 2013) were utilized as pre-COVID-19 controls.
All samples were tested for their reactivity to the receptor-binding domain of the SARS-CoV-2 spike glycoprotein with the use of enzyme-linked immunosorbent assay (ELISA) that captures IgG, IgM, and IgA antibodies.
Moreover, ten inflammatory cytokines (interferon-gamma, tumor necrosis factor-alpha, IL-1 beta, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-13) were appraised with the use of a novel multiplex electrochemiluminescent sandwich assay.
This study has shown that bilateral colostrum samples showed IgG, IgA, and IgM reactivity to the receptor-binding domain of SARS-CoV-2 in 73%, 73%, and 33% of the 15 COVID-19 mothers, respectively. On the other hand, colostrum samples from only two of the eight pre-pandemic controls had IgG and IgA reactivity to the receptor-binding domain.
In addition, COVID-19 mothers exhibited significantly higher levels of 9 of the 10 inflammatory markers (all except interferon-gamma) in comparison to the pre-COVID-19 controls. It has to be noted that analogous results were obtained with both the spot card-eluates and liquid samples.
"While there are some conflicting reports, the lack of increased interferon-gamma expression associated with COVID-19 is consistent with our findings in colostrum and needs further investigation", say study authors in this medRxiv paper.
No barriers for breastfeeding
In a nutshell, colostrum samples that were archived long before the pandemic were crucial controls for this study when used in conjunction with the analysis of bilateral samples. The similarities between results from the spot card and the liquid colostrum demonstrate the value of the spot card collection method.
"The evolution and duration of the antibody response, as well as dynamics of the cytokine response, remain to be determined," caution study authors. "Our results also indicate that future large-scale studies can be conducted with milk easily collected on paper spot cards," they add.
In any case, the detection of SARS-CoV-2-specific antibodies in women with diverse COVID-19 disease presentations provides objective data in favor of initiating breastfeeding, regardless of SARS-CoV-2 infection. These findings also facilitate future large-scale studies that may use milk collected on paper spot cards.
medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.