IgY antibodies for the immunoprophylaxis and therapy of respiratory infections

Abbas, Aymn Talat; El-Kafrawy, Sherif Aly; Sohrab, Sayed Sartaj; Azhar, Esam Ibraheem Ahmed

BRSV is an enveloped, negative-stranded, nonsegmented RNA virus that is the main cause of respiratory disease in young calves. 119 BRSV is closely related to human RSV (HRSV), which is the most common cause of lower respiratory tract infections in children worldwide. HRSV results in more than 3 million hospitalizations and an annual mortality rate of 66,000-199,000 in children under 5 years. 120 It has no licensed vaccine or effective treatment. 121 The similarity between the two viruses makes BRSV infection in calves a good animal model for studying HRSV. 122 Purified IgY preparations, obtained from hens immunized with BRSV, neutralized BRSV in vitro. First, a group of hens were immunized with six doses of immunogen containing 10 5 TCID 50 /ml BRSV at days 0, 18, 32, 56, 85, and 106. The second group were immunized with two doses containing 10 7 TCID50/ml BRSV at days 0 and 42. Vaccines were prepared with Freund's complete adjuvant for the first dose and Freund's incomplete adjuvant for the following doses. In the first group, birds began to respond after the third immunization and antibody titers increased to the maximum after the fifth immunization. In the second group, the antibodies were detectable after the first immunization, and high titers were detected after the second immunization. Notably, only two doses were needed to induce specific neutralizing antibodies in the second group, reducing suffering and stress of birds caused by repeated inoculation. 123 The specificity of the IgY obtained against BRSV in the second group, which presented the highest serum neutralizing antibody level, was evaluated by a dot blot assay. IgY antibodies were able to specifically recognize the virus at dilutions up to 1:20,480. Moreover, from the in vitro neutralization test, the highest neutralizing anti-IgY antibody titer was detected after the fifth immunization in the first group and after the second immunization in the second group. These findings suggest that the immune response could be improved by increasing the amount of the antigen used for inoculation. The study concluded that IgY technology is an attractive tool that could potentially be used for prophylaxis and/or treatment of respiratory disease caused by BRSV infection (Table 1) . 123