The invention pertains to the use of VirB10 to immunize a host against an infection by a bacterium having T4SS. The invention provides a vaccine comprising VirB10, a fragment of VirB10, a polynucleotide encoding VirB10 or a polynucleotide encoding a fragment of VirB10 and a pharmaceutically acceptable carrier and/or adjuvant. The invention also provides a method of immunizing a host against an infection caused by a bacterium having T4SS, the method comprising administering to the host a vaccine of the invention. The vaccines and the methods of the invention can be used to immunize against infections caused by bacteria having T4SS in dogs, rabbits, cats, pigs, cattle, sheep, goats, deer, horses, rodents and humans.