Molecular analysis of Boophilus spp. (Acari: Ixodidae) tick strains

Boophilus spp. (Acari: Ixodidae) parasitize cattle and other farm and wild animals in tropical and subtropical regions of the world. Ticks belonging to the genus Boophilus have undergone evolutionary processes associated with habitat adaptation following biogeographical separation, resulting in strains with marked morphological differences. We have characterized at the molecular level B. microplus strains from Latin America and Australia, employing sequences derived from the bm86 coding region, an intron located within the bm86 gene, and DNA short tandem repeats (STR). A B. annulatus strain was employed for comparison. The results indicated that variation within the bm86 coding region is higher between B. microplus strains than between some B. microplus strains and B. annulatus. The sequence of the intron was not informative for phylogenetic analysis, varying among individuals of the same strain. Two STRs were identified in B. microplus (STRs BmM1 and BmM2) and one in B. annulatus (STR Ba1). Southern hybridization experiments with STRs BmM1 and BmM2 as a probe revealed the prevalence of dispersed moderately repeated DNA in the genome of B. microplus. The analysis of polymorphism at STR locus BmM1 evidenced differences within and between populations of B. microplus. These results support at the molecular level the existing differences between B. microplus strains and suggest tools to characterize these populations.

Analysis of enterovirus sequences recovered from the cerebrospinal fluid of patients with epidemic neuropathy

An outbreak of a previously unknown disease, termed epidemic neuropathy (EN), occurred in Cuba between 1991 and 1993. Although nutritional and oxidative stress in the population were rapidly associated with the disease, several findings were not compatible with such stress being the only cause. In the search for biological factors, samples of the cerebrospinal fluid (CSF) from patients with EN were studied and found to have a slowly progressing cytopathic effect (CPE) on VERO cells. Although the results of several studies indicate the presence of enteroviruses, the CPE and other physico-chemical characteristics are not typical of these viruses. Viral sequences have now been amplified from patients' CSF, using oligonucleotide primers homologous to the enterovirus 5' non-coding region. The sequences of the amplified region showed a high degree of variability (7%-69%) when compared with the coxsackievirus (Cox)A9 Griggs used as the reference strain. Furthermore, sequences differing by > 55% (58%-70%) were isolated from a single individual. These results indicate the generation in stressed individuals of enterovirus quasispecies with altered biological properties, and these could have played a major role in the neurological injury of EN.

A simulation study of the effects of acaricides and vaccination on Boophilus cattle-tick populations

This paper describes a simulation model to evaluate different control strategies for Boophilus microplus. The model combines a dynamic life-history module for tick-population dynamics with other modules for vaccination, sterile-hybrid larval release and use of acaricide dipping vats. The tick life-history module considers the cattle's nutritional level and allows for distribution of ticks by age at all stages of growth. Appropriately, the model was sensitive to host resistance and to host-nutritional status. The validity of the life-history module--as well as that of the vaccination and acaricide dipping--vats modules--was demonstrated by comparing simulated and real data for several geographical locations in Cuba and Brazil. Optimum tick-control strategies for the first year of vaccination were designed and the effect of long-term vaccination on tick population was also studied.

Optimal protein structure alignments by multiple linkage clustering: application to distantly related proteins

A fully automatic procedure for aligning two protein structures is presented. It uses as sole structural similarity measure the root mean square (r.m.s.) deviation of superimposed backbone atoms (N, C alpha, C and O) and is designed to yield optimal solutions with respect to this measure. In a first step, the procedure identifies protein segments with similar conformations in both proteins. In a second step, a novel multiple linkage clustering algorithm is used to identify segment combinations which yield optimal global structure alignments. Several structure alignments can usually be obtained for a given pair of proteins, which are exploited here to define automatically the common structural core of a protein family. Furthermore, an automatic analysis of the clustering trees is described which enables detection of rigid-body movements between structure elements. To illustrate the performance of our procedure, we apply it to families of distantly related proteins. One groups the three alpha + beta proteins ubiquitin, ferredoxin and the B1-domain of protein G. Their common structure motif consists of four beta-strands and the only alpha-helix, with one strand and the helix being displaced as a rigid body relative to the remaining three beta-strands. The other family consists of beta-proteins from the Greek key group, in particular actinoxanthin, the immunoglobulin variable domain and plastocyanin. Their consensus motif, composed of five beta-strands and a turn, is identified, mostly intact, in all Greek key proteins except the trypsins, and interestingly also in three other beta-protein families, the lipocalins, the neuraminidases and the lectins. This result provides new insights into the evolutionary relationships in the very diverse group of all beta-proteins.