Can human IgG subclasses distinguish between confirmed and unconfirmed SARS-CoV-2 infections?

Background: Immunoglobulin G (IgG) subclasses play a crucial role in the immune response to viral infections. While total IgG levels can generally provide an indication on the immune response, specific IgG subclasses can offer more detailed information about nature of the immune response and stage of the infection. Herein, we addressed the value of both total (t) and SARS-CoV-2-specific (s) IgG-subclasses in distinguishing between infection-confirmed virus-qRT-PCR-positive (IC; V-qRT-PCR-P) and infection-unconfirmed virus-qRT-PCR-unchecked (IU; V-qRT-PCR-UC) Egyptians.

Results: Both the t-IgG2 and 4 means were significantly higher (SH) among the IU subjects, whereas, the s-IgG1 and 3 means were SH among the IC ones. On the gender levels, both the t-IgG2 and 4 means were SH among the IU females, whereas, the mean of the s-IgG1 was SH among the IC females. The t-IgG4 mean was SH among the IU males, whereas, both means of the s-IgG1 and 3 were SH among the IC males. Significant positive correlations (SPC) were recorded between both the t-IgG1 and 3 with the symptom grades (SG) among the IU humans (r = 0.200 and 0.253, respectively). Also, SPC was noticed between the s-IgG2 and the SG among the IU females (r = 0.6782). SPC was recorded between both the t-IgG1 and the s-IgG2 with the SG among the IU males (r = 0.794 and 0.373, respectively). SPC was noticed between the t-IgG3 and the age among the IC males (r = 0.779).

Conclusion: Although the limitation of the small studied sample size, our results suggest some total and SARS-CoV-2-specific IgG-subclasses as both supplemental and gender-specific immune markers to distinguish between confirmed and unconfirmed SARS-CoV-2 infections.