Community Level Correlates of COVID-19 Booster Vaccine Hesitancy in the United States: A Cross-Sectional Analysis.

Introduction: Evidence exists that individual-level sociodemographic factors contribute to vaccine hesitancy, but it is unknown how community-level factors affect COVID-19 booster dose hesitancy. The current study aims to fill this knowledge gap by comparing data from a nationwide survey on COVID-19 vaccine hesitancy with a community-level indicator, i.e., the Distressed Communities Index (DCI). Methods: Attitudes toward vaccinations, vaccine literacy, COVID-19 vaccine confidence index, and trust were measured using a 48-item, psychometrically valid and reliable survey tool. In this study, 2138 survey participants residing in the United States were divided into quintiles of varying community distress levels based on their zip codes using the DCI. Data were analyzed through Chi-square, one-way ANOVA, and post hoc analysis with Tukey's test. Results: A significantly higher proportion of participants from the distressed communities had lower trust than their prosperous counterparts (26.6% vs. 37.6%, p < 0.001). On the contrary, participants from the prosperous communities had significantly higher vaccine confidence index scores than those in distressed communities (2.22 ± 1.13 vs. 1.70 ± 1.01, p < 0.001). Conclusions: These findings affirm the importance of developing community-level interventions to promote trust in COVID-19 vaccinations and increase booster dose uptake. From these results, future studies can examine the efficacy of various community-level interventions.

Teaching Skills Training for Pre-clinical Medical Students Through Weekly Problem-Based Learning Teaching Topic Presentations and Directed Feedback.

Problem: Medical students commonly encounter scenarios in which they are charged with teaching medical content, but studies find a paucity of teaching skills training especially in the pre-clerkship phase of undergraduate medical programs. Intervention: Videos lessons were created to instruct on five teaching skills identified as useful for presenting short lessons on medical topics: effective learning objectives, appropriate lesson complexity, audience engagement, relevance to practice, and resource selection. A rubric was generated to assess the performance level of each teaching skill. Context: First-year medical students viewed the video lessons and were instructed to implement these teaching skills for the creation and delivery of weekly learning issue (LI) presentations within a problem-based learning (PBL) course. PBL facilitators assessed students by using the rubric to assign a score of 0-2 corresponding to the level of skill performance. Impact: Scores in every dimension of our LI assessment rubric showed significant improvement above week 1 at the end of the initial 4 weeks of practice and assessment. Follow-up assessment showed durable performance and significant improvement for 3 out of 5 at weeks 8 and 12. Lessons Learned: Our novel framework was effective in fostering the adoption and implementation of five teaching skills among first-year medical students over a 4-week period, with most skills remaining durable over 12 weeks. Furthermore, end-of-course surveys showed that students found feedback received using the framework helpful in improving their LIs, and faculty reported that student LI presentation quality improved overall. Supplementary Information: The online version contains supplementary material available at 10.1007/s40670-023-01912-x.

Assessing Acceptability of COVID-19 Vaccine Booster Dose among Adult Americans: A Cross-Sectional Study.

Given the emergence of breakthrough infections, new variants, and concerns of waning immunity from the primary COVID-19 vaccines, booster shots emerged as a viable option to shore-up protection against COVID-19. Following the recent authorization of vaccine boosters among vulnerable Americans, this study aims to assess COVID-19 vaccine booster hesitancy and its associated factors in a nationally representative sample. A web-based 48-item psychometric valid survey was used to measure vaccine literacy, vaccine confidence, trust, and general attitudes towards vaccines. Data were analyzed through Chi-square (with a post hoc contingency table analysis) and independent-sample t-/Welch tests. Among 2138 participants, nearly 62% intended to take booster doses and the remaining were COVID-19 vaccine booster hesitant. The vaccine-booster-hesitant group was more likely to be unvaccinated (62.6% vs. 12.9%) and did not intend to have their children vaccinated (86.1% vs. 27.5%) compared to their non-hesitant counterparts. A significantly higher proportion of booster dose hesitant individuals had very little to no trust in the COVID-19 vaccine information given by public health/government agencies (55% vs. 12%) compared to non-hesitant ones. The mean scores of vaccine confidence index and vaccine literacy were lower among the hesitant group compared to the non-hesitant group. Compared to the non-hesitant group, vaccine hesitant participants were single or never married (41.8% vs. 28.7%), less educated, and living in a southern region of the nation (40.9% vs. 33.3%). These findings underscore the need of developing effective communication strategies emphasizing vaccine science in ways that are accessible to individuals with lower levels of education and vaccine literacy to increase vaccination uptake.

Molecular epidemiology of GB type C virus among individuals exposed to hepatitis C virus in Cameroon.

GB Virus Type C (GBV-C), a blood-borne flavivirus currently infects about one sixth of the world's population. Its transmission has been reported through parenteral, sexual and vertical routes. Unusually for RNA viruses, it exhibits a high degree of conservation of the polyprotein sequence. The geographical distribution of GBV-C suggests an African origin and a long-term co-evolution in the human population but without any known pathogenicity. The aim of this study was to describe the different sub-types of this virus in Southern Cameroon. We studied the genetic epidemiology of GBV-C among rural populations where many HIV-1 and HCV genotypes have been identified. Plasma samples of 345 subjects with evidence of HCV exposure were tested for GBV-C infection. To detect GBV-C RNA, reverse transcription followed by a nested PCR of 5'UTR were performed. Direct sequencing and phylogenetic studies using PHYLIP, PAUP* and SimPlot were carried out. In total, 31 GBV-C RNA-positive samples were detected giving a prevalence of 9.0% among HCV-exposed individuals. Phylogenetic analysis of the 5'UTR showed two distinct clusters: Genotype 1 and Genotype 2. Twenty-eight isolates (8.0%) clustered with Genotype 1 and 3 (1.0%) with Genotype 2. More than one genotype of GBV-C is prevalent in Cameroon of which GBV-C Genotype 1 is more common, confirming reports in the literature. Studying the near full-length genome sequences of GBV-C isolates from primates in this region may provide clues of viral recombination, evolution and origin.

Selection pressure from neutralizing antibodies drives sequence evolution during acute infection with hepatitis C virus.

BACKGROUND & AIMS: Despite recent characterization of hepatitis C virus-specific neutralizing antibodies, it is not clear to what extent immune pressure from neutralizing antibodies drives viral sequence evolution in vivo. This lack of understanding is particularly evident in acute infection, the phase when elimination or persistence of viral replication is determined and during which the importance of the humoral immune response has been largely discounted. METHODS: We analyzed envelope glycoprotein sequence evolution and neutralization of sequential autologous hepatitis C virus pseudoparticles in 8 individuals throughout acute infection. RESULTS: Amino acid substitutions occurred throughout the envelope genes, primarily within the hypervariable region 1 of E2. When individualized pseudoparticles expressing sequential envelope sequences were used to measure neutralization by autologous sera, antibodies neutralizing earlier sequence variants were detected at earlier time points than antibodies neutralizing later variants, indicating clearance and evolution of viral variants in response to pressure from neutralizing antibodies. To demonstrate the effects of amino acid substitution on neutralization, site-directed mutagenesis of a pseudoparticle envelope sequence revealed amino acid substitutions in hypervariable region 1 that were responsible for a dramatic decrease in neutralization sensitivity over time. In addition, high-titer neutralizing antibodies peaked at the time of viral clearance in all spontaneous resolvers, whereas chronically evolving subjects displayed low-titer or absent neutralizing antibodies throughout early acute infection. CONCLUSIONS: These findings indicate that, during acute hepatitis C virus infection in vivo, virus-specific neutralizing antibodies drive sequence evolution and, in some individuals, play a role in determining the outcome of infection.

Hepatitis C virus immune escape via exploitation of a hole in the T cell repertoire.

Hepatitis C virus (HCV) infection frequently persists despite eliciting substantial virus-specific immune responses. Thus, HCV infection provides a setting in which to investigate mechanisms of immune escape that allow for viral persistence. Viral amino acid substitutions resulting in decreased MHC binding or impaired Ag processing of T cell epitopes reduce Ag density on the cell surface, permitting evasion of T cell responses in chronic viral infection. Substitutions in viral epitopes that alter TCR contact residues frequently result in escape, but via unclear mechanisms because such substitutions do not reduce surface presentation of peptide-MHC complexes and would be expected to prime T cells with new specificities. We demonstrate that a known in vivo HCV mutation involving a TCR contact residue significantly diminishes T cell recognition and, in contrast to the original sequence, fails to effectively prime naive T cells. This mutant epitope thus escapes de novo immune recognition because there are few highly specific cognate TCR among the primary human T cell repertoire. This example is the first on viral immune escape via exploitation of a "hole" in the T cell repertoire, and may represent an important general mechanism of viral persistence.

Maternal neutralizing antibody and transmission of hepatitis C virus to infants.

To determine whether lower levels of hepatitis C virus (HCV)-specific neutralizing antibodies (nAb) are associated with an increased risk of mother-to-child transmission (MTCT) of HCV, HCV nAb titers were assessed in 63 mothers coinfected with HCV and human immunodeficiency virus (HIV) type 1. Of the mothers, 16 transmitted HCV to their infant, but no difference was detected between the ability of maternal plasma from transmitters and nontransmitters to neutralize heterologous HCV pseudoparticles (median nAb titer, 1:125 vs. 1:100; P = .23). In the setting of HIV/HCV coinfection, we found no evidence that HCV nAbs are associated with the prevention of MTCT of HCV.

Genetic divergence of hepatitis C virus: the role of HIV-related immunosuppression.

BACKGROUND: We tested the hypothesis that HIV-related immunosuppression alters the host-hepatitis C virus (HCV) interaction, resulting in fewer amino acid-changing substitutions in HCV viral variants. Higher HCV RNA levels in persons coinfected with HIV compared with HCV infection alone suggest increased viral replication. If this increase is dependent on decreased immune selective pressure, then a reduced rate of nucleotide changes resulting in amino acid replacements (nonsynonymous changes, dN) would be expected. METHODS: We investigated HCV envelope sequences over time in 79 persons with chronic HCV infection who were HIV negative (group 1) or HIV positive with (group 3) or without (group 2) severe immunodeficiency. We amplified a 1026-nt region of the HCV genome, which encodes a portion of the envelope glycoproteins E1 and E2, including hypervariable region-1 for direct sequence analysis. RESULTS: The overall divergence between paired sequences, dS, dN, and dN/dS, all showed no significant differences among the 3 groups. CONCLUSIONS: By measuring nucleotide substitutions in HCV sequences over time, we found no significant differences in the genetic divergence between HCV-monoinfected control subjects and HIV/HCV-coinfected subjects with various levels of immunodeficiency as measured by CD4+ T-cell counts.

Immunoglobulin allotypes influence IgG antibody responses to hepatitis C virus envelope proteins E1 and E2.

Immunoglobulin (Ig) GM and KM allotypes-genetic markers of gamma and kappa chains, respectively-are associated with the outcome of hepatitis C virus (HCV) infection, but the underlying mechanisms are not well understood. We hypothesized that GM and KM allotypes could contribute to the outcome of HCV infection by influencing the levels of IgG antibodies to the HCV glycoproteins E1E2. We serologically allotyped 100 African American individuals with persistent HCV infection for GM and KM markers and measured anti-E1E2 antibodies. Subjects with the GM 1,17 5,13 phenotype had significantly higher levels of anti-E1E2 antibodies than subjects who lacked this phenotype (p = 0.008). Likewise, subjects with the KM 1-carrying phenotypes had higher levels of anti-E1E2 antibodies than subjects who lacked these phenotypes (p = 0.041). Median titers were fourfold higher in persons expressing both GM 1,17 5,13 and KM 1-carrying phenotypes compared with those who lacked these phenotypes (p = 0.011). Interactive effects of these GM-KM phenotypes were previously found to be highly significantly associated with spontaneous HCV clearance. Results presented here show that Ig allotypes contribute to the interindividual differences in humoral immunity to the HCV epitopes, a finding that may provide a mechanistic explanation for their involvement in the outcome of HCV infection.

Liver enzyme flares and occult hepatitis B in persons with chronic hepatitis C infection.

BACKGROUND: Occult hepatitis B (HBV) has been reported in numerous clinical settings, but it remains unclear whether occult HBV contributes to liver damage. Given that typical chronic HBV infections often have periodic flairs in viral replication and liver damage, we hypothesized that occult HBV may also have flares in viral replication that are associated with increased liver enzymes. STUDY DESIGN: We screened hepatitis B surface antigen negative injection drug users with untreated chronic hepatitis C viral (HCV) infection for unexplained ALT/AST flares. To further enrich for individuals with possible occult HBV flares, we studied those individuals whose flares were associated with IgM antibodies to hepatitis B core antigen. Serum samples were assayed for HBV DNA and serologies were performed in serum collected 6 months before, at the time, and 6 months after the flare. HCV RNA levels were also determined. Controls consisted of individuals who also had ALT/AST flares but who were negative for IgM antibodies to hepatitis B core antigen. RESULTS: Seven study cases and eight control cases were identified. HBV DNA was detectable during the enzyme flares in 7/7 study cases versus 3/8 controls, p=0.026. HBV DNA levels during the flare were low, averaging 1943 +/- 2341 copies/ml, but were higher in study cases versus controls, p=0.002. No change in HCV levels was associated with the flares. CONCLUSIONS: In this population at high risk for occult HBV, AST/ALT flares can be associated with detection of HBV DNA. These findings may link occult hepatitis B to liver injury.

Complete genomes for hepatitis C virus subtypes 6f, 6i, 6j and 6m: viral genetic diversity among Thai blood donors and infected spouses.

In this study, the first complete genome sequences for hepatitis C virus (HCV) subtypes 6f, 6i, 6j and 6m, obtained from infected blood donors in Chiang Mai, Thailand, are reported. Pairwise genome-wide nucleotide similarities between some of these isolates were higher than the 75-80% value used previously to define different HCV subtypes. To investigate further, the entire genomes of four prototype isolates, Th602 (6i), Th553 (6j), B4/92 (6m) and D86/93 (6n), were sequenced. Pairwise comparison of these sequences gave a similar range of nucleotide similarities, thereby providing new information for HCV subtype classification. In order to study the hypothesis of interspousal HCV transmission, four additional complete HCV genome sequences were obtained from two infected Thai blood donors and their spouses, C-0044 and C-0046 (6f), and C-0192 and C-0185 (6m). Pairwise comparison of the sequences revealed that C-0044 and C-0046 share a nucleotide similarity of 98.1%, whilst C-0185 and C-0192 have a similarity of 97.8%. Several other studies of partial HCV sequences of different genomic regions from HCV-infected couples have shown nucleotide similarities ranging from 96.3 to 100%. The similarities of the complete genome sequences from the two couples in the current study are consistent with HCV transmission between spouses.

Effect of micronutrients and iron supplementation on hemoglobin, iron status, and plasma hepatitis C and HIV RNA levels in female injection drug users: a controlled clinical trial.

BACKGROUND: Iron deficiency is common among female injection drug users, but it is unclear whether iron supplementation can reduce anemia and improve iron status without increasing plasma hepatitis C virus (HCV) or HIV RNA levels. METHODS: We conducted a phase 3, double-blind, randomized, controlled clinical trial of daily micronutrients with 18 mg of iron (iron group) versus micronutrients without iron (control group) for 12 months among hepatitis C-positive female injection drug users in Baltimore, Maryland. The main outcome measures were hemoglobin, markers of iron status, plasma HCV RNA, plasma HIV RNA, and liver enzymes at 6 and 12 months of follow-up. RESULTS: Four hundred fifty-eight women (320 HIV-negative and 138 HIV-positive) enrolled in the trial. There were no significant differences in the proportion of women with anemia, ferritin<30 ng/mL, log10 plasma HCV RNA, or log10 plasma HIV RNA between treatment groups at enrollment. The proportion with anemia in the iron and control groups, respectively, was 20.7% versus 31.3% (P=0.026) at 6 months and 26.2% versus 30.4% (P=0.5) at 12 months; with ferritin<30 ng/mL, the proportion was 29.2% versus 55.5% (P<0.0001) at 6 months and 26.2% versus 46.9% (P=0.0018) at 12 months. In the iron and control groups, respectively, mean log10 plasma HCV RNA (IU/mL) was 5.2 versus 5.2 (P=0.86) at 6 months and 5.4 versus 5.3 (P=0.6) at 12 months. Among HIV-positive subjects, mean log10 plasma RNA (copies/mL) in the iron and placebo groups, respectively, was 3.8 versus 3.7 (P=0.75) at 6 months and 3.7 versus 4.1 (P=0.19) at 12 months. There were no significant differences in liver enzyme levels between the treatment groups at enrollment, 6 months, and 12 months. CONCLUSIONS: A daily micronutrient supplement with iron can reduce anemia and improve iron status in female injection drug users without increasing plasma HCV or HIV RNA levels or altering liver enzymes.

Progression of fibrosis during chronic hepatitis C is associated with rapid virus evolution.

Hepatic fibrosis is the primary mediator of disease due to chronic infection with hepatitis C virus (HCV). HCV exists as a quasispecies in each infected individual, and longitudinal viral sequence changes may reveal viral dynamics and the selection pressures applied by the host immune system. Thus, we hypothesized that patterns of sequence change might reveal the immunopathogenesis of fibrosis progression. We tested this hypothesis by studying individuals enrolled in a prospective study of chronic HCV-related hepatic fibrosis with little or no fibrosis at first biopsy (stage 0 or 1) and a second planned liver biopsy sample obtained 4 years later. Serum was obtained from five individuals with fast progression (FP; defined as a >2-stage change between visits) and 10 carefully matched individuals with slow progression (SP; defined as a <2-stage change between visits). We sequenced multiple cloned hemigenomic cDNAs from each person spanning six genes (core through NS3). Phylogenetic analysis revealed temporal shifts in phylogenetic clustering over time, suggesting frequent quasispecies replacement rather than simple diversification. In addition, mixed infections were detected in three subjects, with coexistence in two subjects (one FP, one SP) of subtypes 1a and 1b throughout the 4-year biopsy interval. Subjects with FP had a higher rate of evolution than subjects with SP, with a preponderance of synonymous changes, suggesting purifying selection, except in hypervariable region 1, where positive selection pressure is frequently detected. Thus, in a small but carefully matched cohort we found evidence for rapid neutral evolution of HCV in persons with rapid progression of hepatic fibrosis, suggesting higher turnover of infected cells.

CD4+ T cell-dependent reduction in hepatitis C virus-specific humoral immune responses after HIV infection.

BACKGROUND: Human immunodeficiency virus (HIV) infection adversely affects all stages of hepatitis C virus (HCV) infection, leading to increased rates of viral persistence, higher levels of HCV viremia, and accelerated progression of HCV-related liver disease. These disease interactions may result in part from impairment of B cell function, which is CD4(+) T cell dependent. METHODS: To determine the effect of HIV infection on B cell function, we compared HCV antibody levels and specificities in 29 HCV-infected persons before and after they acquired HIV and assessed the temporal correlation of these changes with overall CD4(+) T lymphocyte counts. RESULTS: The pre-HIV infection HCV antibody titer was a predictor of the subsequent titer for all antigens, and decreasing CD4(+) T cell numbers was strongly associated with a decrease in anti-HCV titers for several antigens. CD4(+) T cells counts of <500 cells/mm(3) were significantly associated with lower HCV antibody end-point titers. Higher HCV end-point titers were associated with fewer years from HIV infection and, for Core antigen, current drug use. CONCLUSIONS: HCV-specific antibody production is impaired by HIV infection, and loss of antibody production depends on CD4(+) T cell depletion. However, the decrease in titers is less significant in those who continue to actively inject drugs.

No association between hepatitis C virus seropositivity and acute myocardial infarction.

Recent studies have linked hepatitis C virus (HCV) infection with carotid atherosclerosis. We investigated the association between HCV seropositivity and acute myocardial infarction using a well-established cohort of young men in the US military and found no evidence to support this association.

Hepatitis C infection among drug users in northern Thailand.

Illicit drug users are commonly infected with hepatitis C virus (HCV) and human immunodeficiency virus (HIV). We evaluated the prevalence, incidence, and risk behaviors associated with HCV infection in 1,859 drug users in northern Thailand. The HCV prevalence was 27.3%: 86.0% among drug injectors (IDUs) and 5.3% among those who did not inject. Sexual behavior was not significantly associated with HCV among IDUs or drug users who used but didn't inject illicit drugs; only injection behaviors were independently associated with HCV in multivariate analysis. Among men, a history and increasing frequency of injecting drugs, older age, and a history of incarceration were associated with HCV infection. Among 514 opiate users who were HCV and HIV seronegative at baseline, 41 incident HCV infections and 6 HIV infections occurred on follow-up; the HCV incidence was 5.43/100 person-years; it was 44.3/100 person-years in IDUs and 1.9/100 person-years in non-injectors. HCV and HIV among drug users in Thailand are common and primarily associated with injection behavior.

Predictors of hepatitis C virus RNA levels in a prospective cohort study of drug users.

High levels of hepatitis C virus (HCV) RNA are associated with a poor response to treatment of chronic hepatitis C, and a substantial reduction in HCV RNA levels predicts a favorable treatment response. We prospectively studied time-dependent and time-independent predictors of HCV RNA levels in 264 drug users with chronic HCV infection. Interviews on medical history and high-risk behaviors, phlebotomy for HIV viral load, serum HCV RNA levels as measured by the COBAS Amplicor HCV Monitor (Roche Diagnostics, Branchburg, NJ), and a lymphocyte subset assay were performed. Factors associated with HCV RNA levels over time were analyzed using a linear mixed model. Nearly 70% of the participants were men, two thirds were Hispanic, and the mean age was 46 years. HCV RNA levels increased over time. Older age (P < 0.001), HIV seropositivity (P = 0.03), and HCV nongenotype 1 (P = 0.05) were predictors of higher HCV RNA levels on multivariate analysis. Among 142 HIV-seropositive participants, a detectable HIV-1 viral load (P < 0.001) and recent alcohol use (P = 0.02) were predictors of higher HCV RNA levels. The predictors of higher HCV RNA levels found in this longitudinal study are consistent with those of prior cross-sectional studies. Further studies are warranted to determine if treatment of alcohol use affects HCV RNA levels.

Binding and internalization of glucuronoxylomannan, the major capsular polysaccharide of Cryptococcus neoformans, by murine peritoneal macrophages.

Glucuronoxylomannan (GXM), the major component of the capsular polysaccharide of Cryptococcus neoformans, is essential to virulence of the yeast. Previous studies found that the interaction between GXM and phagocytic cells has biological consequences that may contribute to the pathogenesis of cryptococcosis. We found that GXM binds to and is taken up by murine peritoneal macrophages. Uptake is dose and time dependent. Examination of the sites of GXM accumulation by immunofluorescence microscopy showed that the pattern was discontinuous and punctate both on the surfaces of macrophages and at intracellular depots. Although resident macrophages showed appreciable accumulation of GXM, uptake was greatest with thioglycolate-elicited macrophages. A modest stimulation of GXM binding followed treatment of resident macrophages with phorbol 12-myristate 13-acetate, but treatment with lipopolysaccharide or gamma interferon alone or in combination had no effect. Accumulation of GXM was critically dependent on cytoskeleton function; a near complete blockade of accumulation followed treatment with inhibitors of actin. GXM accumulation by elicited macrophages was blocked by treatment with inhibitors of tyrosine kinase, protein kinase C, and phospholipase C, but not by inhibitors of phosphatidylinositol 3-kinase, suggesting a critical role for one or more signaling pathways in the macrophage response to GXM. Taken together, the results demonstrate that it is possible to experimentally enhance or suppress binding of GXM to macrophages, raising the possibility for regulation of the interaction between this essential virulence factor and binding sites on cells that are central to host resistance.

Humoral immune response in acute hepatitis C virus infection.

BACKGROUND: There is little information on the timing, magnitude, specificity, and clinical relevance of the antibody response to acute hepatitis C virus (HCV) infection. We investigated the specificity, titer, and neutralizing potential of antibody responses to acute infection by examining 12 injection drug users before, during, and after infection. METHODS: Seroconversion was defined as incident detection of HCV-specific antibodies by using a commercially available enzyme-linked immuosorbent assay (ELISA). HCV protein-specific antibody responses were measured using recombinant antigens in an ELISA. For neutralization assays, plasma was incubated with human immunodeficiency virus (HIV)-HCV H77 or control HIV-murine leukemia virus (MLV) pseudotype virus and then allowed to infect Hep3B hepatoma cells. RESULTS: The mean time to HCV seroconversion was 6 weeks after the onset of viremia. Antibody responses to nonstructural proteins were detected before responses to the structural proteins, and antibodies to both were primarily restricted to the immunoglobulin G1 (IgG1) subclass. The maximum median end point titers for antibody responses to structural and nonstructural proteins were 1 : 600 and 1 : 6400, respectively. Antibodies that neutralized a retroviral pseudotype bearing HCV 1a envelope glycoproteins were detected at seroconversion in only 1 subject and at 6-8 months after seroconversion in 3 subjects. The delayed appearance of neutralizing antibodies was consistent with the late development of antibodies specific for the viral envelope glycoproteins, which are believed to mediate virus neutralization. CONCLUSION: The humoral immune response to acute HCV infection is of relatively low titer, is restricted primarily to the IgG1 subclass, and is delayed. A better understanding of why production of neutralizing antibody is delayed may improve efforts to prevent HCV infection.

Divergent and convergent evolution after a common-source outbreak of hepatitis C virus.

The genomic sequences of viruses that are highly mutable and cause chronic infection tend to diverge over time. We report that these changes represent both immune-driven selection and, in the absence of immune pressure, reversion toward an ancestral consensus. Sequence changes in hepatitis C virus (HCV) structural and nonstructural genes were studied in a cohort of women accidentally infected with HCV in a rare common-source outbreak. We compared sequences present in serum obtained 18-22 yr after infection to sequences present in the shared inoculum and found that HCV evolved along a distinct path in each woman. Amino acid substitutions in known epitopes were directed away from consensus in persons having the HLA allele associated with that epitope (immune selection), and toward consensus in those lacking the allele (reversion). These data suggest that vaccines for genetically diverse viruses may be more effective if they represent consensus sequence, rather than a human isolate.