Evaluation of the Replication, Pathogenicity, and Immunogenicity of Avian Paramyxovirus (APMV) Serotypes 2, 3, 4, 5, 7, and 9 in Rhesus Macaques

Khattar, Sunil K.; Nayak, Baibaswata; Kim, Shin-Hee; Xiao, Sa; Samal, Sweety; Paldurai, Anandan; Buchholz, Ursula J.; Collins, Peter L.; Samal, Siba K.

The hemagglutination inhibition (HI) titer is expressed as the mean reciprocal log 2 (6 standard errors of the mean) of the highest serum dilution causing complete inhibition of four HA units of the indicated APMV, except for APMV-5, which was evaluated by neuraminidase inhibition (NI) assay. All the values are averages from three independent experiments. The mean serum HI titers in all the day 0 serum samples were 0. The serum neutralizing antibody titers were expressed as mean reciprocal log 2 of the serum dilution resulting in complete neutralization of infection in 50% of the wells (mean 6 standard errors of the mean). The limit of detection is 0. The mean neutralizing antibody titers in all the day 0 serum samples were 0. 1 The antibody response to APMV-5 was evaluated by NI assay as described in Materials and Methods. The NI titer is expressed as the mean reciprocal log 2 (6 standard errors of the mean) of the highest serum dilution causing neuraminidase inhibition. doi:10.1371/journal.pone.0075456.t004 Figure 1 . Analysis of the reactivity of sera from rhesus macaques collected following infection with the indicated APMVs, evaluated by Western blotting against purified virus of the homologous APMV strain. Virus representing each of the indicated APMV strains was rAPMV-2 (type 1 Africa), and possibly a marginal increase in the case of rAPMV-4/Fc-BC, and an apparent decrease in replication in the case of rAPMV-7/Fcs-5B. With respect to the absence of clinical disease, the mutants remained as attenuated as their wt parents. However, a larger study would be required to confirm these preliminary observations. A single inoculation via combined intranasal and intratracheal routes in rhesus macaques with wt APMV-2, wt APMV-3, wt APMV-7, rAPMV-7/Fcs-5B and wt APMV-9 induced substantial HI antibody titer, whereas serum HI antibody responses induced by rAPMV-2 (type 1 Africa), wt rAPMV-4, rAPMV-4/Fc-BC, and wt APMV-5 was low. The HI titers correlated either completely or partially with the level of shedding from the lower respiratory tract except in the case of wt APMV-5, for which no shedding was observed but a low level of NI titer was produced. To date, APMV-5 has only been isolated from budgerigars, which are thought to be its natural host [24] . These observations indicated that this virus probably is strongly host restricted.