The spectrum of bicyclic antiautomorphisms of directed triple systems

AbstractA transitive triple, (a,b,c), is defined to be the set {(a,b),(b,c),(a,c)} of ordered pairs. A directed triple system of order v, DTS(v), is a pair (D,β), where D is a set of v points and β is a collection of transitive triples of pairwise distinct points of D such that any ordered pair of distinct points of D is contained in precisely one transitive triple of β. An antiautomorphism of a directed triple system, (D,β), is a permutation of D which maps β to β−1, where β−1={(c,b,a)|(a,b,c)∈β}. In this paper we complete the necessary and sufficient conditions for the existence of a directed triple system of order v admitting an antiautomorphism consisting of two cycles

Postattachment Neutralization of Papillomaviruses by Monoclonal and Polyclonal Antibodies

AbstractPostattachment neutralization of papillomaviruses (PVs) was analyzed in three PV-infectivity models: (i) the BPV-1-induced focus-forming assay using C127 cells; (ii) in vitro abortive infection of rabbit RK-13 and Sf1Ep cells with CRPV; and (iii) HPV11-induced morphological transformation of human foreskin chips in the athymic mouse xenograft system. In each assay system, aliquots of infectious virus were added to the appropriate target cells and incubated at 37°, followed at various postinfection time intervals with neutralizing monoclonal antibodies (N-MAbs) that target surface conformational epitopes. In all three model systems, the N-MAbs were able to neutralize PV infection when added as late as 8 hr after addition of infectious PV to host cells. These results imply that papillomaviruses attach to but do not penetrate inside host cells for a significant period of time and that the bound virus is thus still susceptible to neutralization by neutralizing antibodies