Values represent the titers of neutralizing antibodies against the vectors and subtypes indicated in each column. Four-fold serial dilutions of sera from mice injected with recombinant AAV serotypes 1 to 6 were incubated with the same viruses in all possible combinations, and residual virus infectivity was determined (see “Materials and methods” for details). Three independent samples were analyzed per group. Antibody titers are given as reciprocals of the highest sera dilutions that caused a decrease in vector infectivity of at least 50%. Boldface values indicate titers of neutralizing antibodies against the same serotype with which the mice were initially injected. Abbreviations as in Table 1.