(a)<p>Isolates from corresponding mother-child pairs are indicated by the same number preceded by a letter: A for mothers and B for children. Time of sampling is indicated in parenthesis as months before (-), after (+) or within 1 week from (0) delivery/birth. </p><p>Pairs were grouped according to the mother's virus phenotype, i.e. first those carrying an R5<sup>narrow</sup>, than an R5<sup>broad</sup> and last an R5X4 virus.</p><p>Samples were used to infect U87.CD4 cells expressing wild type CCR5 or CXCR4, or one of the chimeric receptors FC-1, FC-2, FC-4b, FC-5, FC-6 or FC-7. Experiments were repeated twice. –, means no chimeric receptor is used.</p
