Evaluation of cytokines as adjuvants of infectious bovine keratoconjunctivitis vaccines

Randomized controlled field trial to assess the efficacy of an intranasal Moraxella bovis cytotoxin vaccine against naturally occurring infectious bovine keratoconjunctivitis

Background

Infectious bovine keratoconjunctivitis (IBK; pinkeye) is generally considered to be caused by corneal infections with Moraxella bovis. Previous studies demonstrated that M. bovis cytotoxin-specific mucosal immune responses in the bovine eye can be stimulated by intranasal vaccination with a recombinant M. bovis cytotoxin subunit adjuvanted with polyacrylic acid.

Methods

A randomized controlled field trial (two-arm parallel design with blinding) was conducted in beef steers in Northern California to determine if this vaccine could prevent naturally occurring IBK and/or reduce morbidity rates associated with this disease. Beef steers were vaccinated intranasally on days 0 and 21 with either a recombinant M. bovis cytotoxin subunit adjuvanted with polyacrylic acid (Vaccine group) or adjuvant alone (Control group). Eye examinations were performed on all steers every 7 days for 16 weeks to document the occurrence of IBK and to determine sizes of corneal ulcers. Serum and tear samples were collected on days 0, 42, and 112 from a subset of animals to measure changes in systemic and ocular immune responses to M. bovis cytotoxin.

Results

The cumulative proportion of steers that developed IBK after 16 weeks did not differ between groups. Variables related to disease severity were numerically lower in steers that received the experimental vaccine. IBK-affected Vaccine group steers had a significantly lower number of observation weeks with severe ulcers versus Control group steers. Cytotoxin-specific tear IgA was significantly higher in Vaccine group compared to Control group steers on day 112. Conclusion: Although the proportion of animals that developed corneal ulcers associated with IBK did not differ between groups, the lowered metrics of disease severity in vaccinated steers suggests that intranasal vaccination with recombinant M. bovis cytotoxin can reduce the severity of IBK in cattle.

The combination of vaccines and adjuvants to prevent the occurrence of high incidence of infectious diseases in bovine

As the global population grows, the demand for beef and dairy products is also increasing. The cattle industry is facing tremendous pressures and challenges. The expanding cattle industry has led to an increased risk of disease in cattle. These diseases not only cause economic losses but also pose threats to public health and safety. Hence, ensuring the health of cattle is crucial. Vaccination is one of the most economical and effective methods of preventing bovine infectious diseases. However, there are fewer comprehensive reviews of bovine vaccines available. In addition, the variable nature of bovine infectious diseases will result in weakened or even ineffective immune protection from existing vaccines. This shows that it is crucial to improve overall awareness of bovine vaccines. Adjuvants, which are crucial constituents of vaccines, have a significant role in enhancing vaccine response. This review aims to present the latest advances in bovine vaccines mainly including types of bovine vaccines, current status of development of commonly used vaccines, and vaccine adjuvants. In addition, this review highlights the main challenges and outstanding problems of bovine vaccines and adjuvants in the field of research and applications. This review provides a theoretical and practical basis for the eradication of global bovine infectious diseases.

Defining and Diagnosing Infectious Bovine Keratoconjunctivitis

Pinkeye and infectious bovine keratoconjunctivitis (IBK) are imprecise terms that describe diverse ocular diseases. Moraxella bovis is the major causative agent of IBK; however, disease epidemiology is not fully known. Not all cases referred to as pinkeye are of infectious origin, and not all IBK involve M bovis. This article suggests the term pinkeye should no longer be used, offers a case definition for IBK (a herd disease), and suggests describing ocular signs of IBK using existing clinical descriptors rather than resorting to novel scores. A new term "ocular moraxellosis" is defined as IBK from which Moraxella spp are demonstrated.

The Evidence Base for Prevention of Infectious Bovine Keratoconjunctivitis Through Vaccination

Pili and cytotoxins are important virulence factors and antigens for Moraxella spp. Local and systemic immunity may play a role in the body's response to infectious bovine keratoconjunctivitis (IBK). No evidence exists that eliminating the carrier state for IBK is possible or beneficial. Evidence for efficacious transfer of passive immunity from dams to calves is conflicting. Autogenous vaccines and commercial vaccines for putative pathogens for IBK have not yet shown efficacy in blinded randomized field trials. Study design features, such as randomization, blinding, diagnostic criteria, and use of a placebo, reduce the risk of bias in vaccine studies for IBK.

Systemic and ocular immune responses in cattle following intranasal vaccination with precipitated or partially solubilized recombinant Moraxella bovis cytotoxin adjuvanted with polyacrylic acid

OBJECTIVE To evaluate changes in systemic and ocular antibody responses of steers following intranasal vaccination with precipitated or partially solubilized recombinant Moraxella bovis cytotoxin (MbxA). ANIMALS 13 Angus steers with ages ranging from 318 to 389 days and weights ranging from 352 to 437 kg. PROCEDURES Steers were assigned to receive 500 μg of a precipitated (MbxA-P; n = 5) or partially solubilized (MbxA-S; 5) recombinant MbxA subunit adjuvanted with polyacrylic acid. A control group (n = 3) received the adjuvant alone. Each steer received the assigned treatment (1 mL/nostril) on days 0 and 28. Serum and tear samples were collected on days 0 (before vaccination), 14, 28, 42, and 55. Changes in MbxA-neutralizing antibody titers and MbxA-specific IgG concentrations in serum and tears and changes in MbxA-specific IgA concentrations in tears were measured. RESULTS Mean fold changes in MbxA-specific IgG concentration in serum and tears and MbxA-neutralizing antibody titer in tears for the MbxA-P group were significantly greater than those for the MbxA-S and control groups. Mean serum MbxA-neutralizing antibody titer did not differ among the 3 groups. Although the mean fold change in tear MbxA-specific IgA concentration differed significantly among the groups in the overall analysis, post hoc comparisons failed to identify any significant pairwise differences. CONCLUSIONS AND CLINICAL RELEVANCE Systemic and ocular immune responses induced by intranasal administration of the MbxA-P vaccine were superior to those induced by the MbxA-S vaccine. Additional research is necessary to determine whether the MbxA-P vaccine can prevent naturally occurring infectious bovine keratoconjunctivitis.

Mucosal immunization of calves with recombinant bovine adenovirus-3 coexpressing truncated form of bovine herpesvirus-1 gD and bovine IL-6

Previous studies have suggested an important role of the cytokine adjuvant IL-6 in the induction of mucosal immune responses in animals, including mice. Here, we report the in vivo ability of bovine adenovirus (BAdV)-3 expressing bovine (Bo) IL-6, to influence the systemic and mucosal immune responses against bovine herpesvirus (BHV)-1 gDt in calves. To co-express both antigen and cytokine, we first constructed a recombinant BAdV-3 expressing chimeric gDt.BoIL-6 protein (BAV326). Secondly, we constructed another recombinant BAdV-3 simultaneously expressing gDt and BoIL-6 using IRES containing a bicistronic cassette gDt-IRES.IL-6, (BAV327). Recombinant proteins expressed by BAV326 and BAV327 retained antigenicity (gDt) and biological activity (BoIL-6). Intranasal immunization of calves with recombinant BAV326, BAV327 or BAV308 (gDt alone) resulted in demonstrable levels of gDt-specific IgG responses in sera and IgA response in nasal secretions, in all animals. In addition, all calves developed complement-independent neutralizing antibody responses against BHV-1. However, no significant difference could be observed in the induction of systemic or mucosal immune response in animals immunized with recombinant BAV326 or BAV327 co-expressing BoIL-6. Moreover, there was no difference in the protection against BHV-1 challenge particularly in the amount of virus excretion in the nasal cavity in calves immunized with BAV326, BAV327 or BAV308. These data suggest that the BoIL-6 had no modulating effect on the induction of gDt specific mucosal and systemic immune responses in calves.

Ocular immune responses in steers following intranasal vaccination with recombinant Moraxella bovis cytotoxin adjuvanted with polyacrylic acid

Infectious bovine keratoconjunctivitis (IBK) caused by Moraxella bovis is the most common eye disease of cattle. The pathogenesis of M. bovis requires the expression of pili that enable the organism to attach to the ocular surface and an RTX (repeats in the structural toxin) toxin (cytotoxin or hemolysin), which is cytotoxic to corneal epithelial cells. In this pilot study, ocular mucosal immune responses of steers were measured following intranasal (i.n.) vaccination with a recombinant M. bovis cytotoxin adjuvanted with polyacrylic acid. Beef steers were vaccinated with either 500 μg (n = 3) or 200 μg (n = 3) of recombinant M. bovis cytotoxin plus adjuvant. Control group steers (n = 2) were vaccinated with adjuvant alone, and all steers were given a booster on day 21. Antigen-specific tear IgA and tear IgG, tear cytotoxin-neutralizing antibody responses, and serum cytotoxin-neutralizing antibody responses were determined in samples collected prevaccination and on days 14, 28, 42, and 55. Changes in tear antigen-specific IgA levels from day 0 to days 28, 42, and 55 were significantly different between groups; however, in post hoc comparisons between individual group pairs at the tested time points, the differences were not significant. Our results suggest that i.n. vaccination of cattle with recombinant M. bovis cytotoxin adjuvanted with polyacrylic acid effects changes in ocular antigen-specific IgA concentrations. The use of intranasally administered recombinant M. bovis cytotoxin adjuvanted with polyacrylic acid could provide an alternative to parenteral vaccination of cattle for immunoprophylaxis against IBK.