Thomas P. Leist

Role of tumor necrosis factor in Listeria resistance of nude mice

The effects of sheep anti-murine recombinant tumor necrosis factor-alpha (TNF-α) on resistance to Listeria monocytogenes infection were studied in T cell-deficient nu/nu mice. The sheep anti-TNF-α antibody preparation was specific for TNF since it neutralized 300 U of recombinant murine TNF-α in vitro at a dilution of up to 1/1,000 but did not neutralize 32 U of interferon (IFN)-α, -β or 32 U of IFN-γ in vitro at a 1/20 dilution. When tested in vivo in sublethally Listeria-infected nu/nu or T cell-competent C57BL/6 or ICR mice, a single treatment of 0.2 ml anti-TNF-α given intraperitoneally on either day -1,0 or +1 resulted in the death of mice by day 5–7 due to the uncontrolled growth of Listeria; bacterial counts in spleen and liver were increased on days 3–5 by a factor of 10–1,000 in these organs. When examined histologically, organs from mice with the anti-TNF-α treatment contained more, and considerably bigger, lesions that exhibited central necrosis. The enhancing effect of anti-TNF-α on Listeria infection seemed greater early during Listeria infection on days 1–6 when compared to later phases of the infection around days 6–10. From the data presented we conclude that in addition to other lymphokines, such as IFN-γ, TNF-α is of importance during the entire course of a Listeria infection in nu/nu mice.

Antibodies to synthetic polypeptides corresponding to hydrophilic regions of human interferon gamma

Synthetic polypeptides corresponding to hydrophilic regions of human interferon gamma (HuIFN gamma) based on the amino acid sequence of HuIFN gamma inferred from its cDNA sequence were used to produce antibodies in rabbits which reacted with the polypeptides and which might also be expected to recognise native HuIFN gamma. Groups of 3 or 4 rabbits were immunised with synthetic polypeptides corresponding to HuIFN gamma amino acid sequences 1-20, 1-59, 24-59, 36-59 and 87-96 which included major hydrophilic domains of the IFN gamma molecule. All the rabbits produced antibodies which recognised the polypeptide immunogen, but to date only 1 of 4 rabbits immunised with polypeptide 24-59 and 1 of 3 rabbits immunised with polypeptide 1-59 have produced antibodies which also recognise native HuIFN gamma. The positively reacting antiserum from the rabbit immunised with polypeptide 24-59 could only be shown to weakly bind to HuIFN gamma, whereas the positively reacting antiserum from the rabbit immunised with polypeptide 1-59 was shown to both weakly bind to HuIFN gamma and weakly neutralise its in vitro antiviral effect. The results so far obtained suggest that the amino acid sequences close to the N-terminus are important for biological activity.