MRKAd5 HIV vaccine generated neutralizing antibodies to Ad5 capsid proteins more efficiently than to Ad5 fiber.

<p>The titers of Nab to Ad5, Ad5 F35, Ad35 and Ad35 F5 were determined in Ad5 seronegatives and Ad5 seropositives following vaccinations. The minimum detectable titer is at 1∶12 serum dilution and the maximum titer is at the end point dilution to achieve 90% neutralization of the vector. The development of Nab in baseline seronegatives (<b>A</b>) or seropositives (<b>B</b>) at 4 weeks after each vaccination was also shown. <b>A</b> (lower panel) and <b>B</b> (lower panel) show the Nab targets in these sera, excluding sera samples with high anti-Ad35 Nab titers which confound the categorization of the Nab target. (<b>C</b>) Direct comparison of the titer of Nabs to Ad5, or Ad5 capsid, or Ad5 fiber between baseline seronegatives and seropositives. Day 0: pre-vaccination; Week 4: 4 weeks after the first vaccination; Week 8: 4 weeks after the second vaccination; Week 30: 4 weeks after the third vaccination.</p

Seroprevalence of Ad14, Ad28 and Ad41 in HIV-infected, Ad5 seropositive and HIV-uninfected, Ad5 seropositive participants is similar.

*<p>Fisher's exact test.</p

Seroprevalence of Ad35 in HIV-infected, Ad5 seropositive participants is lower compared to that in HIV-uninfected, Ad5 seropositive participants.

*<p>values used for Fisher's exact test, p = 0.002.</p

Pre-existing anti-Ad5 fiber neutralizing antibodies reduced immune responses generated by MRKAd5 HIV-1 gag/pol/nef vaccine, especially HIV specific CD8+ immune responses.

<p>Median (25%–75% percentile),</p>*<p>: p<0.05;</p>**<p>: p<0.01,</p>***<p>: p<0.001.</p

Pre-existing anti-Ad5 capsid neutralizing antibodies reduced immune responses generated by MRKAd5 HIV-1 gag/pol/nef vaccine, especially HIV-specific CD8+ immune responses.

<p>Median (25%–75% percentile),</p>*<p>: p<0.05;</p>**<p>: p<0.01,</p>***<p>: p<0.001.</p

Pre-existing anti-Ad5 neutralizing antibodies reduced immune responses generated by MRKAd5 HIV-1 gag/pol/nef vaccine, especially HIV-specific CD8+ immune responses.

<p>Median (25%–75% percentile),</p>*<p>: p<0.05;</p>**<p>: p<0.01,</p>***<p>: p<0.001.</p