Fariya Yaqub Baig (2009-VA-240)
Effects Of Physico-Chemical Properties Of Diluents On The Infectivity Titers Of Freez Dried Ppr Virus Vaccine - 2016. - 51p.;
6.1. Introduction.
Peste des Petits Ruminants (PPR) is a febrile viral disease of sheep and goats. The disease is
responsible for low productivity in small ruminants and great economic losses to the farmers in
Africa and Asia including Pakistan. There is no specific treatment for PPR and prevention is only
possible through the use of live attenuated vaccines. Being an enveloped virus, PPRV is heat
sensitive. Poor immunological responses have been observed after the vaccination of PPR.
Reasons may be disturbance in maintenance of cold chain, improper handling and route of
vaccination as well as reconstitution in inappropriate diluents. Physiochemical properties
(temperature, pH, osmotic pressure, salinity and UV light) of diluents effects the infectivity of
PPR freeze dried vaccine as live virus vaccines work properly after reconstitution within the
recommended time interval.
6.2. Experimental Design.
Effect of three diluents (normal saline, phosphate buffer saline and distilled water)
adjusted to various pH conditions (5.00, 6.00. 7.00, 8.00, and 9.00) on the infectivity of PPRV
was evaluated. Contents of the freeze dried PPR vaccine vials were diluted with one ml of the
respective diluent adjusted to above mentioned pH conditions. Virus infectivity from the vials
was measured immediately following reconstitution. One set of vials was kept at room
temperature (25 ºC ±2) and virus infectivity was measured afterwards at 30, 60, and 120 minutes
as described in the section 3.3.2. While other set of the vials was kept at refrigerated temperature
(4 ºC ±2) and virus infectivity was measured at 30, 60, 120, and 180 minutes as described in the
Summary
46
section 3.3.2. The change in pH of each vial following reconstitution was also measured
accordingly. Each set of experiment was repeated three times independently.
6.3. Results.
PBS and NS gave equivalent results and proved better than distilled water to restore the
infectivity of PPRV. For a better comparison of virus stability in the PPR freeze dried vaccine
following reconstitution in various diluents adjusted to various pH conditions the infectivity titer
of the virus in the vaccines were measured at various time points. The serial data thus obtained
was analyzed by linear regression model to calculate T-90 values (Time required for 90 %
reduction in virus infectivity). The higher T-90 values indicate better stability of the virus at a
designated condition. At both of the temperatures the T-90 values were equivalent and relatively
higher for all of the diluents adjusted to pH 7.00 and 8.00 while these values are lower at extreme
pH conditions. Minimum T-90 values (126± 56) were observed at pH 9.00 in normal saline kept
at ambient temperature while maximum T-90 (448 ± 49.7) values were observed at pH 7.00 in
phosphate buffer saline kept at refrigerated temperature.
6.4. Conclusion.
Results of the present study suggest that virus infectivity in the live attenuated PPRV vaccine can
be better stabilized following reconstitution in PBS adjusted to neutral or slightly alkaline pH.
Chilled vaccine diluent is preferable to the one kept at room temperature and vaccine should be
administered within 30 minutes of reconstitution.
Microbiology
2645-T
Effects Of Physico-Chemical Properties Of Diluents On The Infectivity Titers Of Freez Dried Ppr Virus Vaccine - 2016. - 51p.;
6.1. Introduction.
Peste des Petits Ruminants (PPR) is a febrile viral disease of sheep and goats. The disease is
responsible for low productivity in small ruminants and great economic losses to the farmers in
Africa and Asia including Pakistan. There is no specific treatment for PPR and prevention is only
possible through the use of live attenuated vaccines. Being an enveloped virus, PPRV is heat
sensitive. Poor immunological responses have been observed after the vaccination of PPR.
Reasons may be disturbance in maintenance of cold chain, improper handling and route of
vaccination as well as reconstitution in inappropriate diluents. Physiochemical properties
(temperature, pH, osmotic pressure, salinity and UV light) of diluents effects the infectivity of
PPR freeze dried vaccine as live virus vaccines work properly after reconstitution within the
recommended time interval.
6.2. Experimental Design.
Effect of three diluents (normal saline, phosphate buffer saline and distilled water)
adjusted to various pH conditions (5.00, 6.00. 7.00, 8.00, and 9.00) on the infectivity of PPRV
was evaluated. Contents of the freeze dried PPR vaccine vials were diluted with one ml of the
respective diluent adjusted to above mentioned pH conditions. Virus infectivity from the vials
was measured immediately following reconstitution. One set of vials was kept at room
temperature (25 ºC ±2) and virus infectivity was measured afterwards at 30, 60, and 120 minutes
as described in the section 3.3.2. While other set of the vials was kept at refrigerated temperature
(4 ºC ±2) and virus infectivity was measured at 30, 60, 120, and 180 minutes as described in the
Summary
46
section 3.3.2. The change in pH of each vial following reconstitution was also measured
accordingly. Each set of experiment was repeated three times independently.
6.3. Results.
PBS and NS gave equivalent results and proved better than distilled water to restore the
infectivity of PPRV. For a better comparison of virus stability in the PPR freeze dried vaccine
following reconstitution in various diluents adjusted to various pH conditions the infectivity titer
of the virus in the vaccines were measured at various time points. The serial data thus obtained
was analyzed by linear regression model to calculate T-90 values (Time required for 90 %
reduction in virus infectivity). The higher T-90 values indicate better stability of the virus at a
designated condition. At both of the temperatures the T-90 values were equivalent and relatively
higher for all of the diluents adjusted to pH 7.00 and 8.00 while these values are lower at extreme
pH conditions. Minimum T-90 values (126± 56) were observed at pH 9.00 in normal saline kept
at ambient temperature while maximum T-90 (448 ± 49.7) values were observed at pH 7.00 in
phosphate buffer saline kept at refrigerated temperature.
6.4. Conclusion.
Results of the present study suggest that virus infectivity in the live attenuated PPRV vaccine can
be better stabilized following reconstitution in PBS adjusted to neutral or slightly alkaline pH.
Chilled vaccine diluent is preferable to the one kept at room temperature and vaccine should be
administered within 30 minutes of reconstitution.
Microbiology
2645-T