HCV-Specific Immune Responses in Noninjecting Drug Users
HCV-Specific Immune Responses in Noninjecting Drug Users
Fifty-seven NIDUs and 15 healthy controls, with average ages of 44 and 45 years, respectively, were enrolled in this study ( Table 1 ). The vast majority of NIDUs were Black (63%) or Hispanic (32%) as compared to the controls, 73% of whom were White. Sixty-eight percent of NIDUs had smoked crack compared with 37% whom had sniffed or snorted cocaine. Similar results were observed among those with HCV-specific antibody or cellular responses. Among those with positive serological responses, 73% indicated that they had smoked crack and 37% had sniffed or snorted cocaine. Similar trends were observed for patients who had detectable HCV-specific cellular responses.
Hepatitis C virus antibodies were detected in 11 out of 57 NIDUs (19.3%). Seven of these individuals had HCV infection, as indicated by HCV RNA positivity. The remaining four seropositive NIDUs had spontaneously resolved HCV infection in the past, as there was no detectable HCV RNA in their blood.
The ELISpot assay was performed in 51 NIDUs, and we found HCV-specific cellular immune responses in 5 (9.8%). These responses were relatively weak and narrow. In 4 individuals, we detected immune responses against two to six peptide mixes with ≤23 mean SFC/well. One subject developed immune responses to two peptide mixes with 76 and 137 mean SFC/well. None of the NIDUs with detectable cellular immunity was HCV seropositive. The ELISpot assay was not available in two seropositive individuals who spontaneously cleared HCV infection. None of the healthy controls had a positive ELISpot test. Of 51 NIDUs in whom both cellular and antibody immunity was measured, 14 (27.5%) were either seropositive or had detectable HCV-specific cellular immune responses, indicating previous exposure to the virus.
We analyzed potential differences in demographic and behavioural characteristics between NIDUs with HCV-specific antibody or cellular immunity and those that were negative on both Ab and ELISpot tests. We also compared seropositive NIDUs with those that were seronegative and those that were negative on both tests and NIDUs with positive HCV-specific cellular immunity with those that had negative ELISpot or were negative on both ELISpot and Ab tests. The results of these comparisons are presented in Table 2 . We did not find any associations between HCV-specific immune responses and recent noninjection drug use practices. However, subjects who were positive on either HCV Ab or ELISpot tests were more likely to report having more casual opposite sex partners in the last 6 months (P = 0.02), to report having casual sex partners of the opposite gender who had ever injected drugs (P = 0.03), to be male who had ever had sex with a male partner (P = 0.05), or to have bought sex (P = 0.03) in the past 6 months compared to subjects who did not have serologic or cellular responses. Similarly, when we compared seropositive subjects with those who are seronegative, seropositive NIDUs had significantly more casual opposite sex partners in the last 6 months (P = 0.02). NIDUs with a positive ELISpot reported significantly more casual opposite sex partners that have ever injected drugs compared with NIDUs with negative ELISpot (P = 0.01). We did not find any demographic differences between subjects with or without HCV-specific immune responses. The modest number of subjects, the multiple outcome measures (anti-HCV, ELISpot) and the inter-correlations among the sexual behaviour variables precluded meaningful multivariate analyses.
Results
Study Subjects
Fifty-seven NIDUs and 15 healthy controls, with average ages of 44 and 45 years, respectively, were enrolled in this study ( Table 1 ). The vast majority of NIDUs were Black (63%) or Hispanic (32%) as compared to the controls, 73% of whom were White. Sixty-eight percent of NIDUs had smoked crack compared with 37% whom had sniffed or snorted cocaine. Similar results were observed among those with HCV-specific antibody or cellular responses. Among those with positive serological responses, 73% indicated that they had smoked crack and 37% had sniffed or snorted cocaine. Similar trends were observed for patients who had detectable HCV-specific cellular responses.
Hepatitis C Virus Prevalence
Hepatitis C virus antibodies were detected in 11 out of 57 NIDUs (19.3%). Seven of these individuals had HCV infection, as indicated by HCV RNA positivity. The remaining four seropositive NIDUs had spontaneously resolved HCV infection in the past, as there was no detectable HCV RNA in their blood.
The ELISpot assay was performed in 51 NIDUs, and we found HCV-specific cellular immune responses in 5 (9.8%). These responses were relatively weak and narrow. In 4 individuals, we detected immune responses against two to six peptide mixes with ≤23 mean SFC/well. One subject developed immune responses to two peptide mixes with 76 and 137 mean SFC/well. None of the NIDUs with detectable cellular immunity was HCV seropositive. The ELISpot assay was not available in two seropositive individuals who spontaneously cleared HCV infection. None of the healthy controls had a positive ELISpot test. Of 51 NIDUs in whom both cellular and antibody immunity was measured, 14 (27.5%) were either seropositive or had detectable HCV-specific cellular immune responses, indicating previous exposure to the virus.
Associations Between Demographic and Behavioural Factors and HCV-specific Immune Responses
We analyzed potential differences in demographic and behavioural characteristics between NIDUs with HCV-specific antibody or cellular immunity and those that were negative on both Ab and ELISpot tests. We also compared seropositive NIDUs with those that were seronegative and those that were negative on both tests and NIDUs with positive HCV-specific cellular immunity with those that had negative ELISpot or were negative on both ELISpot and Ab tests. The results of these comparisons are presented in Table 2 . We did not find any associations between HCV-specific immune responses and recent noninjection drug use practices. However, subjects who were positive on either HCV Ab or ELISpot tests were more likely to report having more casual opposite sex partners in the last 6 months (P = 0.02), to report having casual sex partners of the opposite gender who had ever injected drugs (P = 0.03), to be male who had ever had sex with a male partner (P = 0.05), or to have bought sex (P = 0.03) in the past 6 months compared to subjects who did not have serologic or cellular responses. Similarly, when we compared seropositive subjects with those who are seronegative, seropositive NIDUs had significantly more casual opposite sex partners in the last 6 months (P = 0.02). NIDUs with a positive ELISpot reported significantly more casual opposite sex partners that have ever injected drugs compared with NIDUs with negative ELISpot (P = 0.01). We did not find any demographic differences between subjects with or without HCV-specific immune responses. The modest number of subjects, the multiple outcome measures (anti-HCV, ELISpot) and the inter-correlations among the sexual behaviour variables precluded meaningful multivariate analyses.