Anti-RR reactivity was detected in 41 patients thorough treated with interferon-�� plus ribavirin (38%), but in none of the patients treated with either one of the two drugs (p=0.0001; Fisher’s exact test, Figure 2). In contrast, other IIF-HEp-2 patterns were more frequent in patients receiving only interferon-�� (52.2%) than in those treated with interferon-�� plus ribavirin (25%) and those treated only with ribavirin (33.3%) (p=0.01) (Figure 2). Accurate information on treatment was available for 21 patients with HIV/HCV co-infection. Anti-RR reactivity was detected in 5 of the 20 patients treated with interferon-�� plus ribavirin (20%), but not in the single patient treated only with interferon-��. Figure 2 Antibodies to rods and rings are predominantly observed in HCV patients undergoing treatment with interferon-�� plus ribavirin.

The apparent association of anti-RR reactivity and therapy with interferon-�� plus ribavirin was further strengthened by the analysis of serial samples of RR-positive patients before and after the beginning of treatment. For this analysis, anti-RR reactivity was compared in samples obtained before and each month after the beginning of treatment, and also in samples obtained after treatment had been discontinued. As observed in Figure 3A, all pre-treatment samples were anti-RR negative, and an increasing frequency of anti-RR was observed during the several months of treatment. Even after discontinuation of therapy with interferon-�� plus ribavirin, some anti-RR reactivity was maintained when evaluated up to one year later (Figure 3A).

All time-point groups after initiation of treatment showed higher frequency of anti-RR reactivity compared to pre-treatment samples (p<0.001; Pearson Chi-square test). In contrast, there was no difference in the frequency of other IIF-HEp-2 patterns in samples obtained before and after initiation of therapy with interferon-�� plus ribavirin (Figure 3B, p=0.727). In addition, no anti-RR reactivity was observed in the serial samples from 27 untreated patients. Treated patients showed no statistical difference regarding the frequency of anti-RR during the months on treatment (Figure 3A, p=0.705). Figure 3 Anti-RR reactivity occurs at varying intervals after the beginning of treatment. There was consistent information on the profile of therapeutic response for 125 patients, for whom no association was observed between the appearance of anti-RR and therapeutic response. The proportion of non-responders was equivalent (p=0.271; Pearson Chi-square test) in the 39 patients with anti-RR reactivity (77%), 40 patients with other IIF-HEp-2 patterns (60%), and 46 patients with negative IIF-HEp-2 Drug_discovery tests (67%, Figure 4A and 4B).