FIGURE 5.

Detection of p24 protein from rectal pinch biopsies. (A) Recovery of recombinant p24 spiked into biopsy lysate at 0.02 and 0.1 pg/mL, respectively, is comparable to recovery from buffer as the matrix after IP concentration. (B) Recovery was comparable between buffer and uninfected rectal lysate matrix when using p24 protein recovered from a viremic donor-derived sample as the protein source for spike-in. (C) Cells isolated from a viremic rectal biopsy were lysed and run in standard p24 Simoa or IP-Simoa. The p24 was enriched by the volume reduction during IP and shows linear signal after dilution supporting signal specificity. (D) Reprocessing of rectal biopsies (n = 3) for p24 after lysis revealed that a single extraction yielded >96% of the p24 contained within the biopsy. There was no detectable p24 in solution after IP, indicating complete capture of p24 onto the beads. (E) Comparing measured CD4 protein from HIV-negative and HIV-positive, ART-suppressed rectal biopsies showed no significant difference in CD4 level, implying that similar numbers of CD4⁺ cells were present and lysed from each group. (F) Using the same lysates as in (E), p24 was measurable in several of the HIV⁺ donor biopsy samples (five of nine) after IP-Simoa and not in biopsies from HIV-negative donors (p < 0.05, n = 6). See Materials and Methods for statistical analysis.