A study by Long et al., recently published in the renowned scientific journal "Nature" (https://doi.org/10.1038/s41591-020-0965-6), strongly emphasizes why it is necessary, during and after the corona pandemic, to use readily available and efficiently performed antibody tests such as enzyme-linked immunosorbent assays (ELISA).

In the study mentioned above, Chinese researchers around Long and Huang compared samples from the megacity Chongqing. They examined samples of 74 patients with and without symptoms. After an infection, the body generates an immune response to eliminate a pathogen. The immune system first produces IgM and IgA antibodies. Once the pathogen is recognized and fought, IgG antibodies are produced. IgG antibodies offer some protection against future SARS-CoV-2 infections and are detected in the blood as so-called antibody titers. These IgG antibodies form the memory of the immune system for many years. Vaccines work similarly by teaching the immune system to produce antibodies to protect against specific pathogens.

Quantitative antibody tests that target neutralizing antibodies are among the most important tools for clinicians to determine a titer that reflects the value of a protective immune response to infection. Thus, the titer required for an effective vaccine can easily be determined using our SRS-CoV-2 AESKULISAs.

Long et al. have investigated this fact by measuring IgM and IgG levels in patient samples using ELISA. Even though the sample of patients is small, the study shows no insignificant decrease in antibodies in the patient group with mild to mild symptoms. Only 62.2 percent of patients in the group without symptoms still had antibodies in their blood a few weeks after infection. In the group of symptomatic patients, 78.4 percent still had antibodies in their blood.

After approximately eight weeks, follow-up examinations showed that the antibody concentration in the blood of the symptom-free patients decreased by 81.1 percent. In the group of symptomatic patients, the decrease was only 62.2 percent. The group of Long and Huang also identified patients positive for SARS-CoV-2 by ELISA, who had previously been categorized as negative by RT-PCR. An examination of the samples for cytokines involved in the immune reaction, including G- and M-CSF, IL2, IL6, CCL2, IFN-γ, shows that patients with symptoms had a higher value of these proteins, which indicates a stronger immune response.

Even though the study mentioned above only involved a comparatively small sample, the results cast doubt on previous assumptions that strong symptoms represent a high risk of infection and that anyone who has survived an infection is immune to future infections.

At Imperial College London, Professor Altmann confirms the present study, stating that most infected people show only mild or no symptoms at all. The crucial question is whether they have sustained protective immunity. For him, it is an essential but also worrying point, that many patients in the study showed a significant drop in antibody concentration only 6-7 weeks after the disease's onset. Long et al. write that the decrease in IgG and neutralizing antibodies in early convalescence will influence the immune strategy and serological investigations.

That is precisely where AESKU sees the primary clinical utility of its quantitaive AEKULISA SARS-CoV-2 tests and offers six different kits for detection and monitoring of the immune status.