Genetically altered stable non reverting aromatic dependent (aro)Salmonella typhimurium,strain SL1479 was administrated intramuscularly tohealthy pregnant guinea pigs as alive vaccine. Twenty one pregnant guinea pigswere divided into two groups, the first group (15 animals) was vaccinated twicewith 1ml containing 17 C.f.U /ml approximately fourth and second week preparturitionand the second group (6 animals) injected with 1ml trypticase soybroth (TSB) as a control group.Adverse reaction to vaccination were not observed in the pregnant guineapigs, which parturated normally. The vaccine induced humoral and cellularimmune response as measured by tube agglutination test and delayed typehypersensitivity(DTH)-skin test in the immunized dams and transfer of thisresponse to the newborns, which revealed a high titers ofO(somatic)&H(flagller) agglutination titers and positive delayed typehypersensitivity(DTH)- skin test.The newborn overcome the challenge with virulent Salmonellatyphimurium at 3,6 &8 weeks of age, compared with the controlnewborn which died. These results revealed the efficacy of theprenatal vaccination with aro Salmonella typhimurium to transfer thepassive immunity to the newborn.

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The present study bases on evaluate the immune responses due to experimental infection of (BALB/c) mice by Salmonella hadar .The experiment was carried out on eighty mice of both genders with age range (6 -8) weeks old, the mice were divided randomly into three groups (group A:-contain 20 mice were administrated orally with infectious dose (1.5×10 7 C.F.U\ml) ,group B:-contain 40 mice were administrated orally with LD 50 dose (1.5×10 9 C.F.U\ml) and groupC:-contain 20 mice which inoculated orally with 1 ml of PBS (pH=7.2) and consider as control group).The study has noticed that the experimentally infected mice are able to induce humoral immune response which represented by producing antibody against Salmonella hadar and this production was elevated after two weeks of administration and reach the peak after four weeks post infection then decline sharply after passage of six weeks post infection in both groups (A and B) but the titration of the antibodies in group B was higher on that recorded in group A.It is obvious that S. hadar is able to induce cellular immune response during experimental infection with infectious dose and LD 50 dose and the results of delayed type hypersensitivity have showed increases in the thickness of the right footpads of the mice of both groups (A and B) and the highest mean of the thickness was after 24 hours post immunization.Finally, we concluded that Salmonella hadar in infected the host was able to induce both humoral and cellular immune responses and these responses are dose dependent.