IMMUNITY INDUCED BY VACCINATION WITH RHIPICEPHALUS-APPENDICULATUS SALIVARY-GLAND ANTIGENS DOES NOT AUGMENT PROTECTIVE IMMUNITY ACQUIRED NATURALLY BY EXPOSING RABBITS TO ADULT TICKS
M. Nyindo et al., IMMUNITY INDUCED BY VACCINATION WITH RHIPICEPHALUS-APPENDICULATUS SALIVARY-GLAND ANTIGENS DOES NOT AUGMENT PROTECTIVE IMMUNITY ACQUIRED NATURALLY BY EXPOSING RABBITS TO ADULT TICKS, Journal of medical entomology, 33(4), 1996, pp. 559-565
A study was conducted using rabbits to ascertain the effects of immuni
ty induced with salivary gland antigens (SGA) on naturally acquired ho
st resistance, which was confirmed by exposing groups of rabbits to ad
ult Rhipicephalus appendiculatus (Neumann) ticks. A reciprocal experim
ent was conducted to establish the effect of naturally acquired resist
ance on vaccination with SGA. After the acquisition of resistance by e
ither method of vaccination, rabbits were then challenged with the 3 l
ife stages of the tick. Results of the experiment demonstrated 3 pheno
mena: infestation of rabbits with 60 adult ticks leads to high protect
ion in terms of reduction in the engorged weight against adult ticks,
larvae, and nymphs (88.6, 31.5, and 55.9%, respectively); vaccination
alone provides 53.9, 29.7, and 35.7% reduction in adult, larval, and n
ymphal ticks, respectively; and vaccination of rabbits already exposed
to adult tick infestation appeared to have no additive immunological
benefit above that already provided by adult ticks. Sodium dodecyl pol
yacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting analyses
revealed that antibodies with high avidity to SGA were directed to a
39-kDa polypeptide. This polypeptide was not revealed by sera from rab
bits that were first infested with adult ticks. Sera from rabbits that
were first vaccinated with SGA consistently reacted with the 39-kDa p
olypeptide. Sera from rabbits that were infested recognized strongly a
42-kDa polypeptide among 5 polypeptides in the SGA. Results of the ex
periment show that resistance resulting from adult tick infestation is
not augmented by immunity caused by vaccination with SGA.