Multicenter Safety and Immunogenicity Trial of an Attenuated Measles Vaccine for NHP

Abstract

Measles is a highly contagious viral disease in NHP. The infection can range from asymptomatic to rapidly fatal, resulting in significant morbidity and mortality in captive populations. In addition to appropriate quarantine practices, restricted access, the immunization of all personnel in contact with NHP, and the wearing of protective clothing including face masks, measles immunization further reduces the infection risk. Commercially available measles vaccines are effective for use in NHP, but interruptions in their availability have prevented the implementation of ongoing, consistent vaccination programs. This need for a readily available vaccine led us to perform a broad, multicenter safety and immunogenicity study of another candidate vaccine, MVac (Serum Institute of India), a monovalent measles vaccine derived from live Edmonston-Zagreb strain virus that had been attenuated after 22 passages on human diploid cells.

Figure 1.

Description of the study population. All subjects were rhesus macaques, except for those at site E, which were M. nemastrina.

Figure 2.

Seroconversion. All macaques were sampled at time 0. Subsets of rhesus macaques were sampled at 2, 3, 6, 12, and 15 mo after vaccination. Pigtailed macaques were sampled at 2 and 7 mo after vaccination.

Figure 3.

IgG antibody titers at (A) 3, (B) 6, and (C) 12 mo after vaccination with MVac determined for a subset of 40 rhesus macaques from group 1 site D that received a single vaccination and 40 rhesus macaques from group 2 site D that received 2 doses of vaccine. Because animals in both groups each had received only 1 dose of vaccine at the 3- and 6-mo time points, the groups are combined for those time points. The 2nd dose of vaccine was not admininistered to group 2 until after the collection of the 6-mo sample.

Figure 4.

Neutralization scores (ratio of sample to measles immune globulin control titer) at (A) 6 mo or (B) 12 mo after vaccination with MVac to a subset of 40 rhesus macaques from group 1 site D that received a single vaccination and 40 rhesus macaques from group 2 site D that received 2 doses of vaccine. Because animals in both groups each had received only 1 dose of vaccine at the 6-mo time point, the data are combined for that time points. The 2nd dose of vaccine was not administered to group 2 until after the collection of the 6-mo sample.