In addition, it is known from the literature that class G immunoglobulins, isolated from the serum of patients infected with pneumococcus, neutralized the activity of streptococcal metallo-type IgA1 protease on the surface of bacterium S. pneumoniae [19], and immunization of mice with recombinant IgA1 protease from Streptococcus suis serotype 2 led to the formation of specific antibodies and provided complete protection of animals from infection with a lethal dose of this streptococcus [20]. Here, IGHA1 is linked to infection.