Mycoplasma bovis induces various clinical
manifestations in cattle, such as mastitis, arthritis, and pneumonia.
We have evaluated the immunoreactivity of three variable surface
proteins (Vsps) of M. bovis, namely VspA, VspB, and VspC,
with sera collected from herds with mycoplasmosis or from cattle
experimentally infected with M. bovis. Western blot
analysis revealed that the Vsps are the predominant antigens recognized
by the host humoral response during M. bovis infection. The
immunoreactivity of VspA, VspB, and VspC with host antibodies was
independent of the clinical manifestations, the geographical origin of
the M. bovis isolates, the mode of infection, and the
animal’s history. Moreover, the results showed that Vsp-specific host
antibodies can be detected about 10 days after experimental infection
and for up to several months. The full-length or truncated versions of
the VspA product were overexpressed in Escherichia coli as
fusion proteins (FP-VspA). Recombinant products showed strong
immunoreactivity with the Vsp-specific monoclonal antibodies 1A1 and
1E5, with the corresponding epitopes localized at the VspA N-terminal
and C-terminal ends, respectively. Anti-M. bovis sera of
cattle naturally or experimentally infected also strongly recognized
the full-length FP-VspA. The seroreactivity of sera collected from
cattle between 6 and 10 days after experimental infection was weaker
with truncated versions of VspA lacking the 1E5 epitope than with the
full-length VspA or the truncated versions lacking the 1A1 epitope.
Overall, the results indicate that the Vsps, despite their inter- and
intraclonal variability, may be applied as target antigens in
serodiagnostic assays for epidemiological studies.