A Comparison of the Adaptive Immune Response between Recovered Anthrax Patients and Individuals Receiving Three Different Anthrax Vaccines

Several different human vaccines are available to protect against anthrax. We compared the human adaptive immune responses generated by three different anthrax vaccines or by previous exposure to cutaneous anthrax. Adaptive immunity was measured by ELISPOT to count cells that produce interferon (IFN)-γ in response to restimulation ex vivo with the anthrax toxin components PA, LF and EF and by measuring circulating IgG specific to these antigens. Neutralising activity of antisera against anthrax toxin was also assayed. We found that the different exposures to anthrax antigens promoted varying immune responses. Cutaneous anthrax promoted strong IFN-γ responses to all three antigens and antibody responses to PA and LF. The American AVA and Russian LAAV vaccines induced antibody responses to PA only. The British AVP vaccine produced IFN-γ responses to EF and antibody responses to all three antigens. Anti-PA (in AVA and LAAV vaccinees) or anti-LF (in AVP vaccinees) antibody titres correlated with toxin neutralisation activities. Our study is the first to compare all three vaccines in humans and show the diversity of responses against anthrax antigens.     

Subunit stoichiometry of retinal rod cGMP phosphodiesterase

The cyclic GMP phosphodiesterase of the retinal rod is composed of three distinct types of polypeptides: alpha (90 kDa), beta (86 kDa), and gamma (10 kDa). The gamma subunit has been shown to inhibit phosphodiesterase activity associated with alpha and beta. To investigate the subunit stoichiometry of the retinal phosphodiesterase, we have developed a panel of monoclonal and peptide antibodies that recognize individual phosphodiesterase subunits. By quantitative and immunochemical analysis of the purified subunits, we have shown that each phosphodiesterase molecule contains one copy each of alpha and beta subunit and two copies of gamma subunit. Moreover, gamma can be chemically cross-linked to both alpha and beta, but not to itself, suggesting that alpha and beta may each bind one gamma. The phosphodiesterase is fully activated when both copies of gamma were removed by proteolysis with trypsin. Upon recombination of the purified gamma subunit with the trypsin-activated phosphodiesterase containing alpha beta, the alpha beta gamma 2 stoichiometry is once again restored, with concomitant total inhibition of activity. Our results suggest that at least two activated transducin molecules are required to fully activate one molecule of phosphodiesterase in retinal rods.