Yes, It’s possible that saliva can detect antibodies to the SARS-COV-2 virus that causes the COVID-19, says a new study.
After mRNA vaccination, salivary Immunoglobulin G (IgG) antibody levels were found to be related to IgG titers in blood serum in immunocompromised groups 3 to 4 weeks after vaccination.
Immunocompromised patients have lower antibody responses than healthy people. They must be monitored on a frequent basis since they are at a high risk of getting serious COVID-19 infection.
According to the findings of the study, collecting saliva samples may provide a safe and convenient technique to test immunity in this vulnerable population.
The study
The study included 404 immunocompromised patients and 82 healthy volunteers. At the time of the trial, all participants were found to have no SARS-CoV-2 antibodies in their blood and did not test positive for SARS-CoV-2 infection.
The Pfizer-BioNTech vaccine was administered to all patients in two doses. Saliva and serum samples were obtained prior to vaccination, 10 days later, 21 days later, and 35 days later. The second vaccine dosage was administered three weeks following the first.
IgG levels were tested since previous studies indicated that the Pfizer-BioNTech vaccine elicited greater IgG levels in saliva than IgA levels.
Throughout the trial, 1,870 saliva samples and 1,829 serum samples were obtained. The majority of subjects had normal saliva flow. Patients with CLL or primary immunodeficiencies, on the other hand, had a reduced saliva flow rate.
IgG responses in saliva
After the first vaccine shot, all patients had IgG antibodies in their saliva samples.
People with HIV experienced a 12-fold increase in IgG reactivity in saliva, while healthy patients had a 12-fold rise. People with HIV experienced a 53-fold increase after the second dose, whereas healthy patients experienced a 74-fold increase.
In salivary samples taken 35 days following the initial dose, more than 90% of HIV patients and healthy patients had an IgG response.
There was a moderate 3-fold increase in IgG reactivity in saliva 21 days after vaccination in individuals who received allogeneic hematopoietic stem cell transplantation (HSCT)/chimeric antigen receptor T (CAR-T) cell treatment. However, IgG reactivity increased from 3-fold to 50-fold following the second dose, indicating a powerful immunological response.
Weak humoral responses were seen in persons with chronic lymphocytic leukaemia (CLL), organ transplants, and primary immunodeficiencies. IgG levels in saliva were not detectable in these groups until two weeks following the second vaccination. In addition, they had lower anti-Spike-f and anti-S1 salivary responses than persons with HIV or HSCT/CAR-T. According to the experts, the poor response to vaccination may be attributable to illness or immunosuppressants.
Findings
IgG reactivity in saliva samples was shown to be marginally related to IgG levels 10 days after the initial vaccination dose. However, the correlation between IgG levels in saliva and serum became stronger after the second dose and 2 weeks later.
Spike-f or S1 IgG reactivity in salivary samples was highly related with serum anti-S1 antibody titers 2 weeks after the second dosage in patients with CLL, HSCT/CAR-T, and primary immunodeficiency.
Following complete vaccination, people living with HIV demonstrated a moderate correlation between IgG levels in saliva and serum.
Being younger than 60 years old was associated with higher serum SARS-CoV-2 specific IgG antibody titers.
Some Limitations
The researchers did not examine antibody isotypes or their neutralising power against SARS-CoV-2. Several SARS-CoV-2 variants, including Delta, have spike protein mutations that allow them to avoid or weaken neutralizing antibodies.
SARS-CoV-2 immunity is more than just neutralizing antibodies. Local memory B and T cell immunity is critical in the fight against SARS-CoV-2. The existence of B and T cells in saliva samples, on the other hand, was not investigated in the current investigation.
Furthermore, participants in the research were tested for humoral immunity after receiving the Pfizer-BioNTech vaccine, although how this compares to other coronavirus vaccines is unknown.
Source: The study was published on medRxiv server that publishes preliminary scientific reports.
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