Anti-Spike Antibodies Present in the Milk of SARS-CoV-2 Vaccinated Mothers Are Complement-Activating

Area of Science:

• Immunology
• Virology
• Pediatrics

Background:

• Pneumonia is a leading cause of infant mortality globally.
• SARS-CoV-2 (COVID-19) infections can lead to severe illness.
• Antibodies against SARS-CoV-2 spike protein are produced after infection or vaccination.

Purpose of the Study:

• To investigate antibody-dependent complement activation by anti-SARS-CoV-2 spike protein immunoglobulins in breast milk.
• To determine if breast milk antibodies from vaccinated mothers can activate the complement system.
• To assess the potential protective role of complement activation against SARS-CoV-2 in newborns.

Main Methods:

• Collected serum and milk samples from 22 vaccinated, lactating healthcare and school workers.
• Tested for anti-SARS-CoV-2 spike protein IgG and IgA in serum and milk using ELISA.
• Measured complement pathway subcomponents (C1q, MBL, C3) and assessed in vitro complement activation by milk anti-spike immunoglobulins.

Main Results:

• Vaccinated mothers possess anti-SARS-CoV-2 spike protein IgG in both serum and breast milk.
• These milk-derived antibodies are capable of activating the complement system.
• Complement activation by maternal breast milk antibodies was demonstrated in vitro.

Conclusions:

• Breast milk from SARS-CoV-2 vaccinated mothers contains functional antibodies that can activate complement.
• This antibody-dependent complement activation may provide a protective mechanism for breastfed newborns against SARS-CoV-2 infection.
• Further research is warranted to fully elucidate the protective role of these findings in infant health.