A prospective study of antibody responses to defined epitopes of human papillomavirus (HPV) type 16 in relationship to genital and anorectal presence of HPV DNA.

The aim of this study was to investigate whether antibody responses against synthetic peptides derived from genital human papillomavirus (HPV) proteins are associated with laboratory-proven genital and anorectal HPV infection. In this study, 158 heterosexual patients (110 women and 48 men) were followed prospectively. At each visit we collected serum samples as well as specimens from several sites in the anogenital area for detection of HPV type 6/11 (HPV-6/11), -16, -18, and -33 DNAs by PCR. Immunoglobulin A (IgA) and IgG responses against disrupted bovine papilloma virions and eight different synthetic peptides derived from HPV-6/11, -16, and -18 were determined for serum samples from the first and the last visits. The subjects attended the Municipal Sexually Transmitted Disease Clinic in Amsterdam, The Netherlands, two to seven times (mean, four times) at approximately 4-month intervals. Women were monitored over a period of 155 person-years, and men were monitored over 65 person-years. The magnitudes of the IgA responses against HPV-16 late protein epitopes L1:13, L1:31, and L2:49 were significantly higher in the sera from the last visit among the currently HPV DNA-positive participants than in HPV DNA-negative persons (P = 0.02). When the persons positive for any HPV type at any time during the follow-up period were compared with those who were negative at all times during the follow-up period, we also found a significant elevation of IgA responses against L1:31 and L2:49 (P = 0.04 and 0.01, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Predominance of serum antibodies to synthetic peptide stemming from HPV 18 open reading frame E2 in cervical adenocarcinoma.

AIMS: To determine if there are type specific differences in serum antibody responses to synthetic peptides derived from human papillomavirus (HPV) open reading frame (ORF) E2 in patients with cervical carcinoma. METHODS: Diagnostic phase sera from 88 age-matched women with cervical adenocarcinoma (AC), cervical squamous cell carcinoma (SC), ovarian cancer (OC) or no gynaecological malignancy were available. Serum IgG and IgA antibodies to synthetic peptides corresponding to a residue of HPV 6, 11, 16, and 18 ORF E2 18 amino acids long and a control peptide from mumps virus were determined by ELISA. RESULTS: Both IgA and IgG antibody positivity to the HPV 18 peptide were associated with increased risk (9.0-fold, confidence limits 1.5-199) for AC. IgA positivity to HPV 11, 16, and 18 peptides was associated with an increased risk for SC. However, the association of IgG antibodies to HPV 16 peptide with SC was not significant. IgA or IgG antibodies to HPV 6 or mumps virus peptides were not associated with increased risk for AC, SC, or OC. CONCLUSIONS: These results suggest a specific role for HPV 18 in AC. Differences in antibody responses to HPV peptide in AC and SC suggest immunopathogenetic differences between the two types of cervical carcinoma.     

人乳头状瘤病毒(HPV)16L1病毒样颗粒蛋白与HPV16L1基因联合免疫的体液免疫反应及其抗体的体外中和实验

目的用含有编码人乳头状瘤病毒(HPV)16L1和HPV16L1病毒样颗粒(VLP)蛋白联合免疫小鼠,与用HPV16L1重组表达质粒比较,观察VLP蛋白免疫对免疫小鼠产生抗体的增强作用,以及抗体的体外中和作用,寻找研制HPV16感染的预防性疫苗的有效途径。方法将c57BL／6小鼠,随机分为4组：Ⅰ组：pcDNA-L1(100μl/鼠),Ⅱ组：pcDNA—L1(70μl/鼠) HPV16K1 VLP,Ⅲ组：pcDNA3.1(100μl/鼠)空质粒,Ⅳ组：PBS缓冲液。质粒免疫3次,间隔3周。ELISA法检测其血清抗体,红细胞凝集实验和HPV16病毒样颗粒结合抑制实验体外检测抗体的中和活性。结果pcDNA-L1 HPV16L1 VLP较pcDNA—L1免疫组,3次免疫后的抗体水平均增高,尤其以第2次和第3次免疫后的抗体水平增加更显著。pcDNA—L1 HPV16L1 VLP联合免疫组血清的抑制活性高于pcDNA—L1免疫组,且．He[a细胞结合抑制实验染色呈阴性。结论HPV16L1 VLP联合免疫可以增加目的抗原的中和抗体产生,可能是HPV16有效预防性疫苗研制的更有希望的策略。     

A human papillomavirus type 16 vaccine by oral delivery of L1 protein

To establish an edible HPV16 vaccine, we constructed a recombinant HPV16 L1-expressing Schizosaccharomyces pombe yeast strain (HPV16L1 yeast). A preliminary study revealed that freeze-dried yeast cells could be delivered safely, and were digested in the mouse intestine. The freeze-dried HPV16 L1 yeast was administered orally as an edible vaccine, with or without the mucosal adjuvant heat-labile toxin LT (R192G), to 18 female BALB/c mice. After the third immunization, none of the mice that received the edible HPV16 vaccine showed specific antibody responses, whereas all of the positive controls that were administered intranasally with 5 μg of HPV16-virus-like particles (VLP) had serum IgG, and genital IgA and IgG that reacted with HPV16-VLP in enzyme-linked immunosorbent assays (ELISAs). When a suboptimal dose (1 μg) of HPV16-VLP was administered to all the mice, including the negative control mice, 50% of the mice that were pre-immunized with the edible HPV16 vaccine showed positive serum IgG responses, while none of the negative controls showed any response. Vaginal IgG and IgA antibodies were also elicited in 33 and 39%, respectively, of the mice that were given with the edible HPV16 vaccine and the intranasal boost. All of the antibodies reacted more strongly to intact HPV16-VLP than to denatured HPV16-L1 protein suggesting that the edible vaccine primes for antibody responses against conformation-dependent epitopes. The inclusion of adjuvant in the vaccine formulation marginally increased the genital IgA response (P = 0.06). HPV16-L1 protein in the yeast might induce tolerance in the vaccinated animals that could be recovered by intranasal boosting with a suboptimal dose of HPV-VLP. This freeze-dried yeast system may be useful as an oral delivery of HPV 16 L1 protein.     

Serological responses to human papillomavirus type 6 and 16 virus-like particles in patients with cervical neoplastic lesions.

Serum samples from 36 cervical carcinoma patients, 33 patients with high-grade squamous intraepithelial lesions, and 31 cytologically normal women were tested by enzyme-linked immunosorbent assay (ELISA) using human papilloma virus type 6 (HPV 6) and HPV 16 virus-like particles as antigens. Forty serum specimens from 1-year-old children were used to assign cutoff points. When serum samples from the subjects infected with HPV 16 were tested in an HPV 16 ELISA detecting immunoglobulin A (IgA), IgG, and IgM binding, 61% showed IgA, 44% showed IgG, and 39% showed IgM reactivity. Of HPV 6- or 11- or HPV 18-infected subjects. fewer than 17% showed IgA or IgG responses and 33% showed IgM reactivity. In contrast, 13% showed IgA, 10% showed IgG, and 16% showed IgM reactivity in the HPV DNA-negative controls. The results suggest that the IgA and IgG responses are HPV 16 specific and the IgM response is cross-reactive to different HPV types. On the other hand, the serological responses to HPV 6 did not differ in the patient and control groups. The percentages of patients positive for both IgA and IgG antibodies were significantly higher in the groups with high-grade squamous intraepithelial lesions (12% [4 of 33]; P = 0.04) and cancer (17% [6 of 36]; P = 0.02) than in the healty women (0% [0 of 31]), and the percentages for either IgA or IgG were higher for the cancer group (47% [17 of 36]; P = 0.01) than in the normal group (19% [6 of 31]). Most sera positive for IgA and IgG in the patient groups showed higher titers than those in the normal group. All these results suggest that high IgA and IgG responses are good indicators for estimating HPV 16 infection.     

Pre- and posttreatment serum antibody responses to HPV 16 E2 and HSV 2 ICP8 proteins in women with cervical carcinoma.

Serum antibodies to early proteins of human papillomavirus type 16 (HPV 16 E2 protein) and herpes simplex virus type 2 (HSV 2 ICP8) can be measured by ELISA. In the serum of 122 newly diagnosed cervical carcinoma patients and age-matched controls, enhanced IgA antibody levels to an HPV-16 E2 protein derived peptide no. 245 indicated a 9.5-fold (95% confidence limits 2.8-57.2) relative risk of cervical carcinoma. No significant risk was found with a corresponding HPV 6 E2 peptide or HSV 2 ICP8. To evaluate the HPV 16 E2 peptide as a possible tumor marker for cervical carcinoma serial postoperative serum samples were tested from 27 women with cervical carcinoma. Antibody responses to the HPV 16 E2 peptide depended on the clinical stage. Stage I and II patients showed decreasing posttreatment IgA and/or IgG antipeptide antibody levels. Stage III and IV patients initially showed decreasing antipeptide antibody levels followed by increasing levels. These patients also showed increasing IgG antibody levels to the HSV 2 ICP8. However, increasing antibody levels to the HPV 16 E2 peptide indicated significantly (P less than 0.05) worse 2-year disease free survival (recurring disease) than did stable or decreasing antibody levels. The results suggest that serum antipeptide antibodies to the HPV 16 E2 peptide no. 245 can be used for the monitoring of cervical carcinoma.     

Prospective study on the development of antibodies against human papillomavirus type 6 among patients with condyloma acuminata or new asymptomatic infection

The development over time of antibodies to human papillomavirus type 6 (HPV 6) was studied prospectively in a group of 26 condyloma patients receiving multiple treatments, as well as in 17 healthy subjects with a new HPV 6 infection. The condyloma patients provided serum samples during 2–12 visits over a period of 1–20 months, and the levels of IgA, IgG and IgM antibodies to HPV 6, 11 and 16 capsids, and to HPV 6-derived peptide antigens were determined. Among the capsid antibodies, the IgG and IgA responses against HPV 6 were the most prominent, whereas IgM was detected only in a few patients. During follow-up, seroconversion to HPV capsids was found in six patients and antibody peaks disappeared during follow-up in nine patients. There was no association between serology and cure of the wart. One hundred twenty subjects who reported multiple sexual partners, but found negative for HPV DNA at multiple anogenital and oral sites, provided serum samples and swabs for HPV DNA analysis at 2–7 visits during 4–74 months. Seventeen subjects acquired HPV 6 DNA and were included in the study. Serum IgA, IgG and IgM antibodies to HPV 6 capsids were induced concomitantly with the acquisition of viral DNA (P = 0.02, 0.002 and 0.006, respectively), and declined again when the viral DNA was no longer detectable. In conclusion, antibodies to HPV 6 did not predict the clinical course of condylomatous disease, but appear to be useful mainly as epidemiological markers of viral exposure. © 1995 Wiley-Liss, Inc.     

IgG antibodies to human papillomavirus 16, 52, 58, and 6 L1 capsids: case-control study of cervical intraepithelial neoplasia in Japan

In Japan, human papillomavirus (HPV) 16, 52, and 58 are most commonly associated with cervical intraepithelial neoplasia (CIN). By contrast, HPV6 is primarily associated with genital warts. This study was designed to evaluate the association between IgG antibody responses to common HPVs and the risk of CIN development within a Japanese population. CIN cases (n = 141) and controls (n = 109) were tested for cervical HPV DNA and serum IgG antibodies to L1 capsids of HPV16, 52, 58, and 6. Seropositivity to HPV16, 52, and 58 L1 capsids was significantly higher in CIN cases than in controls: 27%, 21%, and 31% versus 16%, 11%, and 11%, respectively (P < 0.05). HPV6 L1 seropositivity was not significantly associated with CIN lesions (P = 0.11). Presence of viral DNA for either HPV16, 52, or 58 correlated with a significant antibody response against the homologous L1 capsids but not heterologous L1 capsids. Furthermore, seropositivity to multiple types of HPV16, 52, and 58 was more strongly associated with an increased risk of CIN development than seropositivity to a single type (P for trend <0.001). These findings indicate that IgG antibodies to L1 capsids of HPV16, 52, and 58 represent an increased risk of CIN development, with antibodies to multiple types being indicative of a further increase in risk. The presence of CIN lesions in women with seropositivity to multiple types suggests that viral exposure to a given type may not be protective against infections by other types and subsequent CIN development.     

Enhanced mucosal and systemic immunogenicity of human papillomavirus-like particles encapsidating interleukin-2 gene adjuvant

Here, we report the enhanced mucosal and systemic immunogenicity of human papillomavirus type (HPV) 16 L1 virus-like particles (VLP) encapsidating a cytokine genetic adjuvant. Plasmid DNA expressing interleukin-2 (pIL2) was encapsidated in VLP using the reassembly property of VLP from disassembled L1 capsomeres. pIL2 in reassembled VLP showed stability against DNase I, indicating encapsidation. After intramuscular immunization into mice, the highest vaginal and salivary HPV16 L1-specific IgA titers were observed in pIL2-encapsidated VLP, followed by VLP plus pIL2 in separate plasmid, and VLP alone. Similar to mucosal responses, serum IgG, IgG1, and IgG2a antibody titers were the highest in the group treated with pIL2-encapsidated VLP. Moreover, the adjuvanticity of pIL2 encapsidated in VLP was stronger in IgG2a antibody relative to IgG1 antibody. Our results indicate that the encapsidation of a genetic cytokine adjuvant pIL2 would be beneficial for more effective induction of mucosal and systemic immune responses to VLP vaccines.     

Antibodies against papillomavirus antigens in cervical secretions from condyloma patients.

Samples of cervical secretions and serum from 30 women with genital condylomas and 30 age-matched controls were tested for the presence of immunoglobulin A (IgA) and IgG antibodies against a panel of papillomavirus-derived antigens. The same cervical samples were also analyzed for presence of human papillomavirus (HPV) DNA by Southern blotting and polymerase chain reaction. By Southern blotting HPV DNA was detected in 8 of 30 patients with condylomas and 2 of 30 controls, and by the polymerase chain reaction HPV DNA was detected in 14 of 30 patients with condylomas and 5 of 30 controls. A total of 18 of 29 patients with condylomas and 8 of 28 controls had IgA antibodies in cervical secretions to an E2 synthetic peptide, and 17 of 29 patients with condylomas and 5 of 28 controls had local IgA antibodies to an E7 peptide (P < 0.025 and P < 0.005, respectively). The results suggest that measurement of local antibody production against selected HPV antigens may be useful in the study of HPV immunology and, possibly, for the diagnosis of HPV infection.     

HPV31型L2保守中和表位可诱发广谱中和抗体

目的研究人乳头瘤病毒31型(HPV31)次要外壳蛋白L2保守中和表位的免疫活性及诱发抗体的中和范围。方法合成法获得HPV31 L2 aa.17-40多肽,用EDC法偶联KLH,联合弗氏佐剂免疫新西兰大白兔,用假病毒中和实验检测免疫血清对来自α4、α7、α9、α10及β1亚属的多个HPV型别的中和抗体。结果 HPV31 L2-KLH偶联肽可在新西兰大白兔体内诱发针对至少17种HPV型别的广谱中和抗体,其中HPV31的中和抗体滴度最高,HPV5/45/57的次之。结论首次发现HPV31 L2保守中和表位免疫血清具有广谱中和活性,为基于该表位的广谱HPV疫苗研发奠定了基础。     

HPV L1 C-末端保守序列短肽诱导HPV多型别交叉抗体的初步研究

通过对HPV L1序列进行比对,发现HPV L1 C-末端存在长30个氨基酸残基的保守序列短肽;出于检测短肽是否可以诱生HPV多种型别交叉抗体的目的,将该序列短肽加弗氏佐剂用于日本大耳白兔和BALB/c小鼠免疫,然后用ELISA方法检测此免疫动物血清及其分泌物中的IgG抗体滴度,发现此免疫动物体内已诱生出高滴度的血清IgG抗体(>1∶20000);再用ELISA、免疫组织化学和Western blot的方法对此诱生血清抗体与HPV阳性宫颈癌细胞株的反应情况进行检测,发现这些短肽抗血清可与16、18型HPV L1很好地进行反应,其对照组呈现阴性。这一研究结果表明短肽可以诱生HPV多种型别交叉抗体。它对后续研发HPV L1广谱疫苗或检测试剂盒具有重要意义。     

Detection of antibodies to L1, L2, and E4 proteins of human papillomavirus types 6, 11, and 16 by ELISA using synthetic peptides

Antibodies against eight synthetic peptides spanning different epitopes located on L1, L2, and E4 proteins of human papillomavirus (HPV) types 16, 6, and 11 were examined in sera from 73 women infected by HPV and from 139 healthy controls. Only three of these peptides were reactive. Two located on proteins L2 and E4 of HPV 16 seem type specific since antibodies to these peptides were detected, respectively, in 21% and 15% of the HPV 16 infected patients and in 2.5% and none of women infected by other HPVs. The third peptide located on the L1 protein of HPV 6 bears a common epitope since antibodies to this peptide were detected not only in 85% of women infected by HPV 6 or 11, but also in 82% of women infected by other HPVs, and in 74% and 71% of the control groups (10–12-year-old children and adults, respectively). In conclusion, none of the peptides investigated seems useful to develop ELISAs for serological diagnosis of HPV infection. © 1995 Wiley-Liss, Inc.     

Enhanced mucosal and systemic immune responses following intravaginal immunization with human papillomavirus 16 L1 virus-like particle vaccine in thermosensitive mucoadhesive delivery systems

To develop more potent and convenient mucosal human papillomavirus (HPV) vaccines, we tested the effect of thermosensitive mucoadhesive vaginal vaccine delivery systems on the local and systemic antibody responses to HPV 16 L1 virus-like particles (VLP). HPV 16 L1 VLP expressed from recombinant baculovirus-infected Sf21 insect cells were delivered in phosphate-buffered saline (PBS) or thermosensitive mucoadhesive delivery systems, composed of poloxamers (Pol) and varying amounts of polyethylene oxide (PEO). Pol/PEO-based vaginal vaccine delivery systems existed in liquid form at room temperature, but gelled at 37 degrees C. The mucoadhesiveness of Pol/PEO-based delivery systems increased with PEO, but the formulations with PEO higher than 1.0% were too viscous to be administered into the vagina. Vaccine vehicles affected the vaginal and salivary immune responses to HPV 16 L1 VLP intravaginally administered into mice. At 42 days after the first intravaginal immunization of HPV 16 L1 VLP with cholera toxin, vaginal and salivary IgA titers were the highest in the group given in Pol/PEO 1.0% vehicle followed by Pol/PEO 0.4% and PBS vehicles. Intravaginal coadministration of HPV 16 L1 VLP and cholera toxin in Pol/PEO 1.0% showed 31- and 39-fold higher titers compared to the PBS-based HPV 16 L1 VLP groups administered by intravaginal and intramuscular routes, respectively. Following intravaginal administration, Pol/PEO 1.0%, but not Pol/PEO 0.4%, showed significantly higher HPV 16 L1 VLP-specific serum IgG titers as compared to the PBS vehicle. Our results indicate that the use of in situ-gelling vaginal vaccine delivery systems with increased mucoadhesiveness would be beneficial for more effective induction of mucosal and systemic immune responses to intravaginally administered HPV 16 L1 VLP vaccines.     

Mucosal immune responses to meningococcal group C conjugate and group A and C polysaccharide vaccines in adolescents

Previous studies in children have shown that Haemophilus influenzae type b (Hib) polysaccharide conjugate vaccines can reduce nasopharyngeal carriage of H. influenzae and provide herd immunity and suggest that this effect is mediated through mucosal antibodies. As this phenomenon may operate in other invasive bacterial infections which are propagated by nasopharyngeal carriage, mucosal antibody responses to meningococcal C conjugate and A/C polysaccharide vaccines were investigated. A total of 106 school children aged 11 to 17 years were randomized to receive a single dose of either conjugate or polysaccharide vaccine in an observer-blind study. Before and at 1, 6, and 12 months after immunization, samples of unstimulated saliva were collected and assayed by enzyme-linked immunosorbent assay for group C polysaccharide-specific immunoglobulin A (IgA), IgA1, IgA2 and secretory component, IgG antibodies, and total IgG and IgA. A subset of serum samples were also assayed for specific IgA and IgG antibodies. The concentrations of specific IgA and IgG in saliva were expressed both as nanograms per milliliter and as nanograms per microgram of total IgA or IgG. One month after immunization, significant increases in antibody titers (both IgA and IgG) were observed in saliva in both groups. There were significant subsequent falls in antibody titers by 6 months. Anti-meningococcal C-specific secretory component and IgA antibody titers were closely correlated (r = 0.85, P < 0.001), but there was no significant correlation between salivary and serum IgA titers, suggesting that IgA antibodies are locally produced. Significant correlation was found between salivary and serum IgG titers (r = 0.52, P < 0.01), suggesting that salivary IgG may be serum derived. Compared with polysaccharide vaccine, the conjugate vaccine induced significantly higher salivary IgG responses (P < 0.05), although there were no significant differences between salivary IgA responses to the two vaccines. The conjugate vaccine induced greater salivary IgG responses than a polysaccharide vaccine. Both vaccines induced significant salivary IgA antibodies. Further studies are needed to establish the functional significance of these mucosal responses.     

Presence of antibody reactive with synthetic peptide derived from L2 open reading frame of human papillomavirus types 6b and 11 in human sera.

Nine oligopeptides corresponding to segments of different open reading frame (ORF) proteins of human papillomavirus (HPV) 6b and HPV-16 were prepared and tested for reactivity with human sera in enzyme-immunoassay (ELISA). Of these only heptadecapeptide derived from L2 ORF of HPV-6b, and encoded also by L2 ORF of HPV 11, was reactive with some human sera. Over 400 human sera of different origin were tested for the presence of antibody to this antigen. While less than 15% of sera from healthy subjects or cervical carcinoma patients were found antibody positive, sera from the majority of condylomata accuminata (CA) patients were reactive. The antibody titres varied from 1:10 (initial serum dilution) to 1:80; in this respect there was no marked difference between sera from CA patients and the other subjects. The prevalence of antibody was higher among promiscuous than nonpromiscuous women. This is in line with the assumption that sexual intercourse is the most important route of HPV 6 and 11 transmission.     

Magnitude of serum and intestinal antibody responses induced by sequential replicating and nonreplicating rotavirus vaccines in gnotobiotic pigs and correlation with protection

A sequential mucosal prime-boost vaccine regimen of oral attenuated (Att) human rotavirus (HRV) priming followed by intranasal (i.n.) boosting with rotavirus protein VP2 and VP6 rotavirus-like particles (2/6-VLPs) has previously been shown to be effective for induction of intestinal antibody-secreting cell (ASC) responses and protection in gnotobiotic pigs. Because serum or fecal antibody titers, but not intestinal ASC responses, can be used as potential markers of protective immunity in clinical vaccine trials, we determined the serum and intestinal antibody responses to this prime-boost rotavirus vaccine regimen and the correlations with protection. Gnotobiotic pigs were vaccinated with one of the two sequential vaccines: AttHRV orally preceding 2/6-VLP (VLP2x) vaccination (AttHRV/VLP2x) or following VLP2x vaccination (VLP2x/AttHRV) given i.n. with a mutant Escherichia coli heat-labile toxin (mLT) as adjuvant. These vaccines were also compared with three i.n. doses of VLP+mLT (VLP3x) and one and three oral doses of AttHRV (AttHRV1x and AttHRV3x, respectively). Before challenge all pigs in the AttHRV/VLP2x group seroconverted to positivity for serum immunoglobulin A (IgA) antibodies. The pigs in this group also had significantly higher (P < 0.05) intestinal IgA antibody titers pre- and postchallenge and IgG antibody titers postchallenge compared to those in the other groups. Statistical analyses of the correlations between serum IgM, IgA, IgG, and virus-neutralizing antibody titers and protection demonstrated that each of these was an indicator of protective immunity induced by the AttHRV3x and the AttHRV/VLP2x regimens. However, only IgA and not IgM or IgG antibody titers in serum were highly correlated (R2 = 0.89; P < 0.001) with the corresponding isotype antibody (IgA) titers in the intestines among all the vaccinated groups, indicating that the IgA antibody titer is probably the most reliable indicator of protection.     

Significance of specific Epstein-Barr virus IgA and elevated IgG antibodies to viral capsid antigens in nasopharyngeal carcinoma patients

The feasibility of using elevated Epstein-Barr virus (EBV) specific-IgG antiviral capsid antigen (VCA) and IgA anti-VCA antibody levels as an aid in diagnosis of nasopharyngeal carcinoma (NPC) was analyzed by determination of serum antibody titers to EBV in 54 NPC patients, 114 healthy blood donors, and 40 family members by the immunoperoxidase assay (IPA). No significant difference was found in the prevalence rate of EBV IgG anti-VCA antibodies (titer greater than or equal to 20) between the patient group and the control and family groups (100% vs 92% and 90%, respectively). The prevalence rate of elevated EBV IgG anti-VCA titers (greater than or equal to 80, greater than or equal to 160, greater than or equal to 320, greater than or equal to 640) was significantly higher in the NPC patients than in controls. For example, at an IgG titer of greater than or equal to 320, the prevalence rate was 82% in the NPC patient group and 1.7% in the controls (P less than 0.0001). The prevalence of EBV IgA anti-VCA antibodies (greater than or equal to 10) was significantly higher in the NPC patients than in control and family groups (82% vs 6.1% and 0%, respectively). The prevalence rate for elevated EBV IgA anti-VCA (greater than or equal to 20) was found to be significantly higher (P less than 0.0001) in NPC patients than in the control group (70% vs. 1.7%). A significantly high proportion (P = 0.0004) of NPC patients who had serum EBV IgA anti-VCA titers of less than 20 had elevated IgG titers to VCA greater than or equal to 320 (21% vs 1.7% among controls). It appears that testing for IgG antibodies at a serum dilution of 1:320 and for IgA antibodies at a dilution of 1:20 by the IPA technique comprises the best combination for the differentiation between NPC patients and health controls (91% vs 3.4%), and it is suggested that these be used as screening markers for NPC patients.     

Predominant immunoglobulin A response to phase II antigen of Coxiella burnetii in acute Q fever

Diagnosis of acute Q fever is usually confirmed by serology, on the basis of anti-phase II antigen immunoglobulin M (IgM) titers of >/=1:50 and IgG titers of >/=1:200. Phase I antibodies, especially IgG and IgA, are predominant in chronic forms of the disease. However, between January 1982 and June 1998, we observed anti-phase II antigen IgA titers of >/=1:200 as the sole or main antibody response in 10 of 1,034 (0.96%) patients with acute Q fever for whom information was available. In order to determine whether specific epidemiological or clinical factors were associated with these serological profiles, we conducted a retrospective case-control study that included completion of a standardized questionnaire, which was given to 40 matched controls who also suffered from acute Q fever. The mean age of patients with elevated phase II IgA titers was significantly higher than that usually observed for patients with acute Q fever (P = 0.026); the patients were also more likely than controls to live in rural areas (P = 0.026) and to have increased levels of transaminase in blood (P = 0.03). Elevated IgA titers are usually associated with chronic Q fever and are directed mainly at phase I antigens. Although the significance of our findings is unexplained, we herein emphasize the fact that IgA antibodies are not specific for chronic forms of Q fever and that they may occasionally be observed in patients with acute disease. Moreover, as such antibody profiles may not be determined by most laboratories, which test only for total antibody titers to phase I and II antigens, the three isotype-specific Ig titers should be determined as the first step in diagnosing Q fever.     

Purified hexameric Epstein-Barr virus-encoded BARF1 protein for measuring anti-BARF1 antibody responses in nasopharyngeal carcinoma patients

WHO type III nasopharyngeal carcinoma (NPC) is highly prevalent in Indonesia and 100% associated with Epstein-Barr virus (EBV). NPC tumor cells express viral proteins, including BARF1, which is secreted and is considered to have oncogenic and immune-modulating properties. Recently, we found conserved mutations in the BARF1 gene in NPC isolates. This study describes the expression and purification of NPC-derived BARF1 and analyzes humoral immune responses against prototype BARF1 (B95-8) and purified native hexameric BARF1 in sera of Indonesian NPC patients (n = 155) compared to healthy EBV-positive (n = 56) and EBV-negative (n = 16) individuals. BARF1 (B95-8) expressed in Escherichia coli and baculovirus, as well as BARF1-derived peptides, did not react with IgG or IgA antibodies in NPC. Purified native hexameric BARF1 protein isolated from culture medium was used in enzyme-linked immunosorbent assay (ELISA) and revealed relatively weak IgG and IgA responses in human sera, although it had strong antibody responses to other EBV proteins. Higher IgG reactivity was found in NPC patients (P = 0.015) than in regional Indonesian controls or EBV-negative individuals (P < 0.001). IgA responses to native BARF1 were marginal. NPC sera with the highest IgG responses to hexameric BARF1 in ELISA showed detectable reactivity with denatured BARF1 by immunoblotting. In conclusion, BARF1 has low immunogenicity for humoral responses and requires native conformation for antibody binding. The presence of antibodies against native BARF1 in the blood of NPC patients provides evidence that the protein is expressed and secreted as a hexameric protein in NPC patients.