A pilot study for prospective evaluation of antibody response in health care workers (HCWs) who had tested positive for SARS-CoV-2 infection

Antibody responses to SARSCOV-2 is usually detected in the patients’ blood within 8-14 days following theonset of COVID-19 symptoms. However, due to therecent emergence of this virus in the human population it is not yet knownhow long these Ab responses will be maintained or whether they willprovide protection from re-infection. Antibody responses to other human coronaviruses havebeen reported to wane over time. In particular, Aantibody responses targetingendemic human alpha and betacoronaviruses can last for as little as 12 weeks,whereas Abs to SARS-CoV and MERS can be detected in some individuals 12-34months after infection.It is important to understand the immune responsesfollowing infection to define parameters in which Aantibody tests can provide meaningful data.Although several cross-sectional studies of antibody responses arising fromSARS-CoV-2 infection have been reported, there is currently limited informationon the longevity of the antibody response.

 AimsTo understand the kinetics ofantibody development and try to understand the durability of the antibodyresponse.To understand the nature ofantibody expressed in asymptomatic individualsStudy design: Itwill be a prospective observational study on HCWs who were tested positive forSARS COV2 infections by RT PCRStudy population & Inclusion Criteria: At least 45 HCWs with positive RT PCR for COVID will be includedin the study.

ExclusionCriteria:

Samples that do not have sufficient volume to complete testing onthe VITROS® Immunodiagnostics system (i.e. less than 1.0 mL)

Grossly haemolysed, icteric or turbid samples, orsamples with visible particulates that are not getting removed even aftercentrifugation.

Samples which have been subjected to more than twofreeze thaw cycles.

Samples from patients for whomthe time between symptom onset and collection of samples cannot be determined.

Materials & Methods

Two sequential samples from HCWs in the convalescent phase will betaken for subjects enrolled in the study. Samples will be collected in a gap ofone month. Subjects who come negative for antibodies earlier will not befollowed up further.

Informed consent willbe taken from all subjects before enrolling into the study. Each subject willhave to sign a declaration form and fill up a questionnaire for exposurehistory, type of symptoms and risk factors. Disease will be categorized intomild, moderate and severe based on severity symptoms and requirement of oxygenor ventilator as per clinical management guidelines by MoHFW, Govt. of India.

**Clinical samples:**3 ml of serum sample will becollected from all subjects enrolled in the study who were positive for SARSCOV-2 RT-PCR.Forall the patient samples, the information viz., Date of Symptoms first observed,date of sample collection, the date of RTPCR showing positive shall also berecorded.

Detection of Antibody levels

The test will be done in-house using a kit approved by ICMR forsurveillance. The VITROS Immunodiagnostic Anti-SARS-CoV-2 IgG which is a chemiluminescence based assay, will be used for detection of IgG. Thesensitivity for samples collected >15 days of onset of symptoms is 90% andthe clinical specificity is 100% as mentioned in the kit literature.

We will also measure the neutralizing antibody levelsof all the subjects by using the the LIAISON® SARS-CoV-2 S1/S2 IgG test. The LIAISON® SARS-CoV-2 S1/S2IgG uses chemiluminescence immunoassay (CLIA) technology for the Quantitativedetermination of anti-S1 and anti-S2 specific IgG antibodies to SARS-CoV-2 inhuman serum or plasma samples.