Passive immunization of macaques against SIV infection

Area of Science:

• Immunology
• Vaccinology
• Virology

Background:

• Passive immunization is a potential strategy for preventing viral infections.
• The efficacy of antibodies derived from vaccinated versus infected hosts for SIV prevention is not fully understood.

Purpose of the Study:

• To evaluate the protective potential of plasma and immunoglobulin from SIVmac vaccine-protected or infected monkeys against homologous SIV challenge in naive rhesus macaques.

Main Methods:

• Rhesus macaques received passive immunization with plasma from a SIVmac vaccine-protected monkey, or plasma/purified immunoglobulin from SIVmac-infected monkeys.
• Recipients were challenged intravenously with 10 AID50 of homologous cell-free SIVmac 4, 18, or 24 hours post-immunization.
• Protection was assessed by monitoring for infection and disease progression.

Main Results:

• Passive immunization with plasma from a SIVmac vaccine-protected monkey conferred complete or partial protection against homologous SIV challenge when administered 4 or 18 hours before exposure.
• Passive immunization with plasma or purified immunoglobulin from SIVmac-infected monkeys failed to protect recipients and was associated with enhanced infection and accelerated disease.
• Administration of anti-SIV immunoglobulin 24 hours post-challenge also appeared to enhance infection.

Conclusions:

• Antibodies generated through vaccination, but not those from natural infection, can confer protection against SIV challenge via passive immunization.
• The source and nature of antibodies are critical determinants of efficacy in passive immunization strategies for SIV.
• Further research is needed to understand the mechanisms behind antibody-mediated enhancement of SIV infection.