Numerous studies of human populations in Europe and Asia have revealed a concordance between their extant genetic structure and the prevailing regional pattern of geography and language. For native South Americans, however, such evidence has been lacking so far. Therefore, we examined the relationship between Y-chromosomal genotype on the one hand, and male geographic origin and linguistic affiliation on the other, in the largest study of South American natives to date in terms of sampled individuals and populations. A total of 1,011 individuals, representing 50 tribal populations from 81 settlements, were genotyped for up to 17 short tandem repeat (STR) markers and 16 single nucleotide polymorphisms (Y-SNPs), the latter resolving phylogenetic lineages Q and C. Virtually no structure became apparent for the extant Y-chromosomal genetic variation of South American males that could sensibly be related to their inter-tribal geographic and linguistic relationships. This continent-wide decoupling is consistent with a rapid peopling of the continent followed by long periods of isolation in small groups. Furthermore, for the first time, we identified a distinct geographical cluster of Y-SNP lineages C-M217 (C3*) in South America. Such haplotypes are virtually absent from North and Central America, but occur at high frequency in Asia. Together with the locally confined Y-STR autocorrelation observed in our study as a whole, the available data therefore suggest a late introduction of C3* into South America no more than 6,000 years ago, perhaps via coastal or trans-Pacific routes. Extensive simulations revealed that the observed lack of haplogroup C3* among extant North and Central American natives is only compatible with low levels of migration between the ancestor populations of C3* carriers and non-carriers. In summary, our data highlight the fact that a pronounced correlation between genetic and geographic/cultural structure can only be expected under very specific conditions, most of which are likely not to have been met by the ancestors of native South Americans.

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Five neutralizing monoclonal antibodies (nMAbs) obtained against type A5 Spain-86 foot-and-mouth disease virus were used to generate a series of neutralization-resistant variants. In vitro and in vivo assays showed that the variants were fully refractory to neutralization by the selecting nMAb. On the basis of cross-neutralization and binding assays, two neutralizing antigenic sites have been located on the virus surface; one, located near the C-terminus of VP1, displayed a linear epitope, and the second, located on VP2, displayed two conformational epitopes. Nucleotide sequencing of RNA of the parental and variant capsid protein-coding region P1 has placed the amino acid changes at position 198 of VP1 for the first site and at positions 72 and 79 of VP2 for the related epitopes in the second site. The relative importance of these two sites in the biological properties of foot-and-mouth disease virus is discussed.

The in vitro viral lymphoproliferative response of pigs vaccinated against foot-and-mouth disease virus (FMDV) has been characterized. Peripheral blood mononuclear cells from immunized animals up to 1 year post-immunization (p.i.) showed a time-dependent FMDV-specific response, as assayed by virusspecific cellular blastogenesis. The optimum viral concentration decreased with time (around 20 weeks p.i.), and the response was faster and weaker. Lymphoproliferation appeared to be mainly due to CD4 + T cells. The response was heterotypic, being induced by all FMDV serotypes tested (C, A and O) after only two vaccinations with FMDV of serotype C (C-$8). Each individual structural protein assessed (VP1, VP2 and VP3) induced proliferation, with VP3 and VP1 being more effective stimulators. In vitro serum neutralization activity and FMDV-specific IgG production were found to be active even at 1 year p.i.

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