A comparative study on the immune response of sheep to foot and mouth disease virus vaccine type Asia-1 prepared with different inactivants and adjuvants

Immunogenicity of imported foot-and-mouth vaccines in different species in Mongolia

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FMD vaccines were independently assessed using published international guidelines.

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Highest titres were seen with oil-adjuvanted vaccines with a 2 dose primary course.

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Lower titres were seen with aqueous vaccines requiring a boost after 3 months.

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It is unknown how the lower titres observed in camels correlate with protection.

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The results have important implications for vaccine policy in Mongolia.

Foot-and-mouth disease (FMD) is a high impact viral disease of livestock for which vaccines are extensively used in control. Mongolia has regular incursions of FMD virus that are typically limited to the eastern region although large epidemics are occasionally reported in the normally disease-free western areas. Vaccines are imported and form an important component of the control strategy. In 2015, post-vaccination monitoring guidelines were published by the FAO-OIE recommending approaches for assessing the appropriateness of imported vaccines including small-scale immunogenicity studies. This study used these recommended approaches to guide the use of vaccine adjuvant type and the need for a one or two dose primary course in the national control programme considering cattle, sheep and Bactrian camels and also whether these vaccines were appropriate for the FMD virus lineages considered high risk to Mongolia (A/ASIA/Sea-97; O/SEA/Mya-98; O/ME-SA/PanAsia; O/ME-SA/Ind-2001). The results of these immunogenicity studies indicated that in cattle and sheep, oil-adjuvanted vaccines led to higher and more persistent neutralisation titres that were satisfactory against the target lineages if a two-dose primary course was utilised. In contrast, aqueous-adjuvanted vaccines were associated with lower titres that likely required a booster after 3 months. Levels of antibodies in Bactrian camels were significantly lower although it is unknown how these may correlate with protection under experimental or field exposure conditions. The results of this study have implications for vaccine policy in Mongolia and suggest further studies on the role of Bactrian camels in the epidemiology of FMD are necessary to indicate if further research on FMD vaccines are needed in this species.

Immune responses of sheep to quadrivalent double emulsion foot-and-mouth disease vaccines: rate of development of immunity and variations among other ruminants

Despite representing the majority of the world's foot-and-mouth disease (FMD)-susceptible livestock, sheep and goats have generally been neglected with regard to their epidemiological role in the spread of FMD. In the present investigations, FMD virus quadrivalent double emulsion (Montanide ISA 206) vaccines were tested in sheep. The oil adjuvant elicited a better immune response at any time than did aluminum hydroxide gel vaccine, and the response developed quicker. The animals maintained their neutralizing antibody titers at >3 log(10) for the duration of the trial (90 days). Sheep were found to be late responders to serotypes A, C, and Asia-1; a clear upward shift in titer was observed at 60 days postvaccination. However, development of the immune response to serotype O in sheep was superior to that in cattle and goats.

Immune responses of goats against foot-and-mouth disease quadrivalent vaccine: comparison of double oil emulsion and aluminium hydroxide gel vaccines in eliciting immunity

The epidemiological role of small ruminants in foot-and-mouth disease (FMD) outbreaks has been generally neglected. Although, the disease in these species is sub-clinical in nature, their role as virus carriers represents a reservoir for further infection and spread of disease. Data on the usefulness of polyvalent FMD vaccine (FMDV) in goats is scant. Thus, the present study was undertaken to evaluate the benefits of a highly potent polyvalent FMDV in goats. In the present investigations, FMDV quadrivalent double oil emulsion (Montanide ISA 206) vaccines were tested in goats at reduced doses of 2 ml per animal (antigen payload 3.5 microg per serotype per dose). The oil adjuvant elicited superior immune response at any given period than aluminium hydroxide gel (AGS) vaccine and the rapidity of development of response was quicker. The duration of immunity also appeared to be maintained for long period. The differences in immune response between two adjuvant groups were statistically significant (P<0.05). The differences were apparent even in kinetics of immune response. Unlike cattle, goats were found to be late responders for oil-adjuvanted vaccine. Our results indicate possible universal usage of double oil emulsion vaccines for disease control programs irrespective of species of animals.

Early antibody responses of cattle for foot-and-mouth disease quadrivalent double oil emulsion vaccine

Foot-and-mouth disease (FMD) is an economically important disease of cloven-hoofed animals. The multiplicity of FMDV serotypes in animals poses a central problem in the policy of vaccination and is of much concern to health authorities. Hence it is the practice of vaccination with polyvalent vaccine for prophylactic measure. In the present report, we analysed the early antibody responses elicited by FMDV quadrivalent (FMDV O, A, C and Asia 1 serotypes) double emulsion (Montanide ISA 206) vaccines in cattle. We observed variations between various viral serotypes in eliciting early antibody response although neutralizing antibody response against all the four serotypes were detected as early as fourth day following vaccination. The duration of immunity also appeared to maintain for long period. The neutralizing antibody titres were maintained well above 2log(10) even after 6 months of vaccination irrespective of serotypes. Thus, allows the possibilities of two vaccinations per year for the maintenance of herd immunity.