Evaluation of Humoral Immunity Following COVID-19 in Pregnancy

Background

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), commonly known as Coronavirus
Disease-19 (COVID-19), is a global pandemic with 7,410,000 confirmed cases and 418,000 deaths
as of 13th June 2020. It is believed that SARS-CoV-2 shares 79.6% of its sequence identity
with SARS-CoV and resembles some clinical outcomes like viral pneumonia. However, it causes
milder symptoms in majority of people infected, and can be an asymptomatic infection in some
individuals. Just in the 21st century, we have seen three major coronavirus (CoV) outbreaks:
SARS-CoV, Middle East respiratory syndrome (MERS)-CoV, and the novel SARS-CoV-2, which have
resulted in many deaths and have posed a real threat to public health. In fact, during SARS
more pregnant women required intensive care and ventilation, and the number of deaths was
higher when compared to non-pregnant adults. This is partly because in pregnancy, the risk of
viral pneumonia is greater compared to the general population.

Understanding T and B cell mediated immunity in COVID-19 participants may hold the key to
developing better vaccines and efficient treatment plans. To date there is only one study
that has investigated circulatory T follicular helper cells (cTFH), which like there germinal
centre counterparts are a specialised effector cluster of differentiation 4 (CD4) T cell that
induces B cell activation, and differentiation into class-switched and antibody secreting
long-lasting plasmablasts. This study observed an increase in cTFH during pregnancy. However,
studies in older patients, which comprise another high risk group, have shown mixed results
with cTFH showing lower levels of activation. This will impact on long term antibody
production following infection or vaccination. We propose that circulatory cTFH, and B cells
may not be as activated in both pregnant women and patients with severe to critical patients
when compared with mild to moderate patients resulting in less or poorly functioning
anti-SARS-CoV-2 antibodies. Therefore, we expect in infected pregnant individuals the
development of long-term immunity may be worse when compared to non-pregnant people with
similar disease severity, making them more susceptible to re-infection. Compared to
influenza, which is another respiratory illness with significant morbidity in pregnancy and
has a current vaccination program, we expect that the same measures of immunity will be less
pronounced post COVID-19 infection. Furthermore, the development of long-term immunity will
be less effective in patients with severe illness, who for the most part, comprise a
particularly high-risk group including the elderly and patients with multiple comorbidities.
It is vital that we expand our knowledge of long-lasting immunity in individuals who have
recovered from COVID-19 to see how long these individuals are protected against re-infection
and whether they develop long lasting immunity. Moreover, there is no current research
establishing the parameters of seroprotective immunity. Previous research has suggested that
SARS-CoV specific Immunoglobin G (IgG) declines significantly within 2 years with some
reports showing a complete loss within 6 years in most SARS-CoV recovered patients. This may
equate to a loss of long-term protection. The investigators of this study propose measuring
SARS-CoV-2 specific IgG levels by doing memory B cell (Enzyme-Linked ImmunoSpot) ELISpots and
comparing the data with cTFH and B cell flow cytometry panels. The research team will be able
to profile the generation and persistence of protective antibodies produced by infected
individuals who go on to recover. The findings from this study will generate hypotheses to be
tested in larger studies of COVID-19 recovered pregnant patients, and also assist researchers
working trying to understand the effectiveness of the vaccines in pregnancy once these become
commercially available.

Research Question

In pregnant individuals who have recovered from COVID-19:

A. How long will their SARS-CoV-2 specific Immunoglobulin G (IgG) levels remain in peripheral
blood, what is the rate of decline and how does this compare to non-pregnant individuals?

B. How did their T cell mediated immune function differ from non-pregnant patients during the
infection?

C. How do their SARS-CoV-2 specific memory T cell differ when compared to severe to
non-pregnant patients' post-recovery?

D. How does antibody production, and B and T cell function post COVID-19 infection in
pregnancy compare with influenza infection and vaccination?

Hypothesis

The investigators hypothesise that pregnant patients with COVID-19 will develop a less robust
and measurable B-cell response when compared to influenza infected/vaccinated women and
non-pregnant individuals, and that their seroprotective antibody responses will decline by 12
months post infection.

Study Aims

A. Establish robust assays to measure SARS-CoV-2-specific IgG from individuals who have
recovered from COVID-19 infection and track these levels over a 12-month period to measure
any decline. In pregnancy, compare this to influenza antibodies produced after infection and
vaccination.

B. Measure frequency of activated cTFH, and antigen-secreting cells (ASCs) at days 7-14 of
symptom onset in pregnant patients with COVID-19 and compare with non-pregnant groups, and
pregnant influenza infected and influenza vaccinated. In addition, compare between
non-pregnant groups with mild to moderate symptoms when compared to severe to critical
patients.

C. Measure frequency of activated memory B cells at day 28 in pregnant patients with COVID-19
and compare with non-pregnant groups, and pregnant influenza infected and influenza
vaccinated. In addition, compare between non-pregnant groups with mild to moderate symptoms
when compared to severe to critical patients.

D. Measure frequency of CD4 and cluster of differentiation 8 (CD8) T cells in pregnant
patients with COVID-19 and compare with non-pregnant groups, and pregnant influenza infected
and influenza vaccinated. In addition, compare between non-pregnant groups with mild to
moderate symptoms when compared to severe to critical patients.

E. Quantify antigen-specific memory T cells and measure frequency of activated T cells in all
patient groups.

F. Quantification of SARS-CoV-2 viral load from infected participants.

Study Design

This study will be a prospective observational project to investigate the potential decline
of protective immunity in pregnancy after participants have recovered from SARS-CoV-2. The
research team will compare these findings with non-pregnant patients who have had COVID-19
and developed mild to moderate symptoms or severe to critical participants. Patients who go
on to join a SARS-CoV-2 vaccine trial will not be excluded but the vaccination date will be
recorded, and their results interpreted accordingly. In order to compare COVID-19 infection
with another respiratory infection and assess long term protective immunity with an
intervention already in place in this patient group designed to provide seroprotective
antibodies, the investigators will investigate influenza and influenza vaccine. Therefore,
data from pregnant patients will also be compared with influenza infected pregnant women and
those who have received the influenza vaccination.