Characterisation of immune responses in healthy foals when a multivalent vaccine protocol was initiated at age 90 or 180 days.

This research focuses on comparing the immune response of foals after receiving a multivalent vaccine either at 90 days or 180 days of age. The results show that foals as young as 90 days can effectively activate their immune system with this vaccine, despite the presence of maternal antibodies, which could suggest earlier vaccination may be viable in higher-risk situations.

Research Objective

The main aim of the study was to understand how a foal’s immune system responds to a multivalent vaccine protocol when administered at either 90 days or 180 days of age. It was desired to know if earlier administration of the vaccine could still bring about effective immunity, given that most vaccination protocols are usually delayed till 6 months to prevent interference by maternal antibodies.

• In the realm of equine health, most vaccination protocols are initiated when the foal reaches six months of age.
• This is to avoid interference caused by maternal antibodies.
• However, this delay could leave foals susceptible to diseases before vaccination commences.

Methodology

The researchers used a randomised block design for the experiment in which 12 healthy foals, who had received colostral transfer, were used. These foals were divided into two groups, one of which received the multivalent vaccine at 90 days (the treatment group), the other at 180 days (the control group).

• Colostral transfer refers to the transfer of a mother’s first milk, called colostrum, which is rich in antibodies and nutrients.
• The multivalent vaccine protocol consisted of a three-dose series followed by a booster vaccine at 11 months.

Results

The immune responses observed in both groups were largely comparable. Measures of cellular immunity – specific expressions of CD4+,CD8+, interleukin-4, interferon-γ, and granzyme B – were similar in response to multiple disease antigens. Both groups also demonstrated significant increase in antigen-specific immunoglobulin G expression after receiving the booster at 11 months.

• CD4+, CD8+, interleukin-4, interferon-γ, and granzyme B are all indicators of immune system activity.
• The antigens used in the research were from a variety of diseases including eastern equine encephalomyelitis, western equine encephalomyelitis, West Nile virus, tetanus toxoid, equine influenza and equine herpesvirus-1/4.
• The increase in immunoglobulin G expression signifies the activation of ‘memory’ immune responses.

Conclusions

The results showed that young foals, even those as young as three months, are capable of activating their immune responses effectively when given a series of three injections of a multivalent vaccine, regardless of the presence of maternal antibodies. The study therefore suggests that early vaccination might be a plausible option in situations where foals are at high risk and hence, require immunity earlier than conventional protocols allow.

• This discovery could have significant implications for high-risk situations where early onset of immunity in foals might be vital.
• However, the researchers caution that immune activation does not necessarily equal protection against diseases and further research would be needed to explore the protective effects of the vaccine protocol used.