PubMed · 15088781
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J M Katz. 2003. Systemic and cellular immunity.. https://pubmed.ncbi.nlm.nih.gov/15088781/
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The immune system uses innate and adaptive immunity to recognize and combat foreign agents that invade the body, but these methods are sometimes ineffective against human papillomavirus (HPV). HPV has several mechanisms for avoiding the immune system. HPV infects, and multiplies in keratinocytes, which are distant from immune centers and have a naturally short lifespan. The naturally short life cycle of the keratinocyte circumvents the need for the virus to destroy the cell, which would trigger inflammation and immune response. In addition, HPV downregulates the expression of interferon genes. Despite viral immune evasion, the immune system effectively repels most HPV infections, and is associated with strong localized cell mediated immune responses. New prophylactic L1 virus-like protein vaccines for HPV 16 and 18 and HPV 6, 11, 16, and 18 are in phase 3 trials. Available data suggests that these vaccines are safe, produce high levels of antibodies, and are effective at preventing HPV infection.
Detection of genotype-specific human papillomavirus (HPV) capsid antibody in serum suggests past HPV infection. Also, these antibodies appear to correlate with vaccine-induced protection against infection, at least in animal models. However, each laboratory defines a reactive result differently and there is no agreed definition of what level of response indicates sero-reactivity. Standardization of assays for HPV capsid antibody will therefore assist with HPV vaccine development and epidemiology. This study was undertaken to investigate the specificity and sensitivity of assays in current use for measuring antibody to the major viral capsid protein L1 of HPV. Ten laboratories from 8 countries each analyzed 12 coded serum samples, which were derived from an uninfected woman, from naturally infected women and from individuals immunized with different vaccine candidates currently under clinical development. Study samples were assayed by methods in routine use in the participating laboratories. Nine assays were based on virus-like particles (VLPs) of 1 or more HPV genotypes. One laboratory used bacterially expressed major capsid protein L1 of HPV genotypes as antigen. There was considerable interlaboratory variation in estimated antibody levels. However, ranking of the potency of HPV 16 reactivity across the 12 test sera was consistent for all 10 laboratories. Expression of HPV 16 antibody levels relative to that of a single serum sample from an HPV16-infected woman considerably improved the interlaboratory assay comparability. Establishment of an International Standard for antibodies to HPV 16 would therefore facilitate the comparison of HPV antibody measurements between laboratories and assays.
The utility of EBV load as a tumor marker in nasopharyngeal carcinoma (NPC) patients suggests that it might also serve as a screening test for individuals who are at high risk for developing NPC. We previously demonstrated that unaffected individuals from high-risk families had elevated anti-EBV antibody levels compared to community controls. In this study, we measured EBV load using 2 different real-time PCR assays (targeting BamH1W and polymerase gene sequences, respectively) carried out in 2 independent research labs in serum samples from 19 untreated NPC cases, 11 healthy community controls and 100 unaffected individuals from families in which 2 or more individuals were affected with NPC. EBV genomes were detectable in 68% of NPC cases by the EBV BamH1W assay and in 74% by the EBV polymerase assay (kappa = 0.64). Patients with stage III or IV disease had significantly higher EBV load compared to those with stage I or II disease (p = 0.008). EBV DNA was detected in a single community control sample by the EBV BamH1W assay and in none of the samples by the EBV polymerase assay. Only one of 100 unaffected family members tested positive by both assays. An additional 14 were positive by only one of the 2 EBV load assays used and usually in only one of the duplicate wells tested, all with very low viral loads (3-50 copies/ml). In addition, EBV load did not correlate with EBV serology results (anti-VCA, anti-DNase, anti-EBNA-1) among these unaffected family members. In conclusion, our study suggests limited clinical utility of the EBV load test, in its current configuration, to screen individuals from high-risk families. Should a more sensitive or specific molecular assay be developed that is capable of detecting and distinguishing tumor-derived EBV genomes or gene products from true negatives, it could be evaluated as a possible screening tool for asymptomatic and early-stage NPC.