Influence of Some Physical Factors on Survival of Marek's Disease Vaccine Virus

Abstract

Cell-associated Marek's disease (MD) vaccine was suspended at dilutions normally used for vaccination in seven commercially available diluents and in tryptose phosphate broth. The stability of diluted vaccines was determined by assay in cell cultures subjected to 0 to 37 C for 0 to 90 minutes. Optimum holding temperatures for MD vaccine virus survival varied with the specific diluents employed. Some diluents afforded greatest survival when dilution was at 0 C and held at 0 C, while others performed best when dilution was at 25 C followed by cooling and holding at 0 C. Diluents which allowed greatest survival when tested at 37 C also performed well under other temperature regimes. Spectinomycin dihydrochloride pentahydrate and various buffering compounds were added to commercial diluents used for diluting MD vaccine. Additives producing osmolality of 745 mOsm/kg and higher markedly reduced vaccine virus survival. The adverse effects of high osmotic pressure were accentuated by extended holding time, elevated incubation temperature, and physical manipulations including mechanical mixing or expressing through a syringe and needle. Satisfactory MD vaccine virus survival was afforded by a commercial diluent especially formulated to accommodate the pH osmolality changes produced by adding spectinomycin dihydrochloride pentahydrate.

Evaluation of Factors That Influence Dose Variability of Marek's Disease Vaccines

“…Osmotic pressure in the diluent was manipulated from 0 to 1000 mOsm/kg by addition of 0 to 3.18% sodium chloride respectively. There was a correlation between increased osmotic pressure and decreased virus survival [229]. Pressures above 475 mOsm/kg severely depressed virus survival, where the normal range of commercial diluents was 288 to 372 mOsm/kg [229].…”

“…Despite limitations such as procedural differences (thawing the vaccine under cold running water rather than with a room temperature water bath) and testing commercial diluents available at the time, the study gives insights into those factors affecting MD vaccines viability. The results showed that temperature plays a role on virus survival and that holding the vaccine diluent at 0 degrees Celsius was optimal regardless of initial diluent temperatures into which the vaccine was reconstituted [229]. The temperature of the diluent to which the vaccine was added also played a role, though some diluents performed best when vaccine was mixed at 25 degrees C and others when mixed at 0 degrees C. In a different study [230], it was found that reconstituting the vaccine in a refrigerated diluent (4 degrees C) rather than a room temperature diluent could lower the titers by 20%.…”

Marek’s Disease and Differential Diagnosis with Other Tumor Viral Diseases of Poultry

“…Therefore, MD vaccines are administered to chicks at hatch by subcutaneous or intramuscular inoculation or in ovo at ED18 via amniotic or intraembryonic route (Sharma and Burmester, 1982). Other factors such as mixing with antibiotics (Colwell et al, 1975;Eidson et al, 1978), joint administration with other vaccines (Rosenberger, 1983), or long delays in vaccination after reconstitution can also decrease vaccine titers. Only viable infected cells are capable of transmitting the vaccine virus, so handling is of crucial importance for a vaccine to retain its efficacy (Halvorson and Mitchell, 1979).…”

Thermal Stability of Vaccines

“…For example, vaccine particles grown in culture at specific ionic strengths may reequilibrate when introduced into solutions of different ionic strength resulting in osmotic swelling or contraction that diminishes the integrity of the vaccine. Marek's disease vaccine has been shown to be extremely sensitive to osmotic changes with an osmolarity of 745 mOsm/kg markedly reducing vaccine virus survival 24…”