Gelatin Particle Agglutination Research Articles

Increasing seroprevalence but waning herd immunity against measles after elimination: Longitudinal seroepidemiology of measles in Osaka Prefecture, Japan, 2003–2020

Japan is one of the countries conducting longitudinal serosurveillance of vaccine-preventable diseases. We conducted surveillance of the local measles-specific antibody titer, calculated the effective reproduction number (Re), and compared data of four terms: term 1, 2003–2006 (before the introduction of the second shot of measles-containing vaccine); term 2, 2007–2010 (early term toward measles elimination); term 3, 2011–2014 (later term toward measles elimination); and term 4, 2015–2020 (after elimination of measles in Japan). Approximately 250 sera from volunteers aged 0 to ≥ 40 years were collected and examined for measles-specific IgG using the gelatin particle agglutination (PA) method annually from 2003 to 2020. Seroprevalence and the geometric mean of the PA antibody titer were examined by term. Re was calculated using the age-dependent proportion immune and contact matrix for each term. Of the 4,716 sera, 886 in term 1, 1,217 in term 2, 1,069 in term 3, and 1,544 in term 4 were collected. The seroprevalence gradually increased from term 1 (88.3% CI 86.0–90.3) to term 4 (95.7% CI 94.6–96.7), and the seroprevalence of term 1 was significantly lower than those of other terms (Fisher’s exact test, p < 0.001), with PA titer ≥ 16 as positive. By contrast, PA antibody titers significantly decreased from term 1 (median 1,024) to term 4 (median 256) (Mann–Whitney U test, p < 0.001). With the protection level (PA titer ≥ 128 and ≥ 256) as positive, Re gradually increased from term 1 (1.8 and 2.3) to term 4 (2.5 and 4.8, respectively). Waning levels of measles antibodies potentially increase the measles susceptibility in Osaka, Japan. This trend might imply a limitation of vaccine-induced immunity in the absence of a natural booster for wild strains after measles elimination. This study provides a cue for maintaining continuous measles elimination status in the future.

A seroepidemiologic study of a measles outbreak, Yamagata Prefecture, Japan, 2017: The estimation of spreaders using serological assays in a measles elimination setting

IntroductionIn regions where the endemic measles virus has been eliminated, early detection of contagious patients is important for preventing the spread of measles and sustaining elimination. To investigate whether serological assays can be used for the estimation of highly infectious patients with measles, we performed a seroepidemiologic study of a measles outbreak in Yamagata Prefecture, Japan, in 2017. MethodsWe tested plaque reduction neutralization (PRN), IgG avidity, and gelatin particle agglutination (PA) assays in 31 patients with measles, subdivided into two super-spreaders, three spreaders, and 26 non-spreaders. Simultaneously, these results were compared with the cycle threshold (Ct) of a semi-quantitative real-time reverse transcription PCR for the measles virus from throat swab specimens. ResultsIn the PRN assay, one super-spreader and two spreaders lacked protective antibodies. The IgG avidity assay showed that two super-spreaders and one spreader had low avidity. The PA assay indicated that two super-spreaders and two spreaders lacked protective antibodies. Comparison of the results of the three serological assays and Ct revealed that patients whose antibody titers were judged as low in the IgG avidity and PA assays showed low Ct (i.e., high viral load), whereas non-spreaders tended to show low viral load. ConclusionsOur preliminary seroepidemiologic analysis of a population of 31 patients with measles suggests that PA and IgG avidity assays may be used for the identification of super-spreader/spreader candidates. However, further investigations are necessary to validate the robustness of these serological assays in detecting contagious measles cases.

Comparison of multiple detection methods of Mycoplasma pneumoniae antibody for the early diagnosis of pediatric mycoplasma pneumonia

Mycoplasma pneumoniae pneumonia (MPP) is a common disease in infants and young children. MPP can also be a potential cause of healthcare-associated pneumonia. However, it is challenging to make an accurate diagnosis in a timely fashion. Our goal is to determine the assay consistencies of acridinium ester chemiluminescence immunoassay (AECLIA) and gelatin particle agglutination (GPA) test for the detection of Mycoplasma pneumoniae (MP) antibody. In this study, a total of 1404 children with suspected MPP were enrolled. Among them, 130 were diagnosed as MPP positive by mycoplasma culture, and 186 were negative. MP antibodies were detected by AECLIA, enzyme-linked immunosorbent assay (ELISA) and GPA. Consistency rates, differences among assays, and diagnosis performance were compared for the three methods. The independent χ2 test results of AECLIA and ELISA for the detection of MP-IgG and MP-IgM antibodies were χ2 = 29.210, P &lt; 0.001; χ2 = 9.081, P = 0.017, respectively, suggesting that the two detection methods are well correlated. Similar analyses were done for the comparison of AECLIA and GPA as well as the comparison of ELISA and GPA. The positive rates of these methods agree with epidemiology data and have good consistency. Thus, AECLIA with a much shorter assay time could be a better option for the screening of MPP.

Detection of Viruses and Mycoplasma pneumoniae in Hospitalized Patients with Severe Acute Respiratory Infection in Northern China, 2015-2016.

Severe acute respiratory infection (SARI) presents a huge disease and economic burden worldwide. The present study described the frequency and types of different infectious etiologies among hospitalized patients with SARI in Tianjin, China, during 2015 and 2016. Basic information, in addition to a throat or serum sample, was collected from SARI patients. Nine viruses were detected using reverse transcription polymerase chain reaction, and Mycoplasma pneumoniae was detected using the Serodia Myco II gelatin particle agglutination test. A total of 585 specimens from 2,290 SARI cases were collected. The most common infection (19.66%, 115/585) was M. pneumoniae, followed by influenza virus A/B (6.15%, 36/585), and respiratory syncytial virus (4.96%, 29/585). Identification of viral or M. pneumoniae infections was the highest in the pediatric medicine ward (74.84%, 119/159), followed by the intensive care unit (37.04%, 80/216) and respiratory medicine ward (34.29%, 72/210). M. pneumoniae was highest (38.71%, 24/62) in the 5-14-year age group. Influenza was the main infection in January 2015 and March 2016. The correlation coefficient for the proportion of hospitalized cases of SARI and the positive detection rate within the same week was 0.25. M. pneumoniae and influenza were the leading pathogens among hospitalized SARI patients. A continued surveillance of hospitalized cases of SARI can detect emerging diseases, such as avian influenza A (H7N9) virus and other respiratory disease outbreaks.

Comparison of anti-HTLV-1 antibody screening tests of clia, cleia, and pa by roc analysis using titer and logistic regression models for diagnosis of HAM/TSP

Background: Anti-HTLV-1 antibody screening test has changed from gelatin particle agglutination (PA) to the third generation chemiluminescent immunoassay (CLIA) and chemiluminescent enzyme immunoassay (CLEIA) in many institutions.

Measles elimination and immunisation: national surveillance trends in Japan, 2008-2015.

Measles elimination relies on vaccination programmes. In Japan, a major outbreak started in 2007. In response, 5-year two-dose catch-up vaccination programme was initiated in April 2008 for children 13-16-years-old. In this study, we analysed the epidemic curves, incidence rates for each age group, virus genotype, vaccination coverage and ratio of measles gelatin particle agglutination (PA) antibody using surveillance data for 2008-2015. Monthly case counts markedly decreased as vaccination coverage increased. D5, which is the endemic virus type, disappeared after 2011, with the following epidemic caused by imported viruses. Most cases were confirmed to have a no-dose or single-dose vaccination status. Although the incidence rate among all age groups ⩾5-years-old decreased during the study period, for children <5-years-old, the incidence rate remained relatively high and increased in 2014. The ratio of PA antibody (⩾1:128 titres) increased for the majority of age groups, but with a decrease for specific age groups: the 0-5 months and the 2-4, 14, 19 and most of the 26-55- and the 60-year-old groups (-1 to -9%). This seems to be the result of higher vaccination coverage, which would result in decreasing natural immunity booster along with decreasing passive immunity in infants whose mothers did not have the natural immunity booster. The 20-29- and 30-39-year-old age groups had higher number of cases, suggesting that vaccination within these age groups might be important for eliminating imported viruses.

P265 Anti-NMDAR auto-immune encephalitis

for a week. MRI brain showed bilateral signal changes in thalami and in the brain stem suggestive of rhombencephalitis. Lumbar puncture (LP) showed 38 cells (98% lymphocytes). He received IV Cefatoxime and IV Acyclovir till CSF bacterial and viral cultures were negative. Blood Mp titre by gelatin particle agglutination test (GPAT) was 2560 (normal less than 40). He was treated with Clarithromycin and steroids for three weeks. Following extubation, he demonstrated mutism with extrapyramidal movements for 2 weeks which spontaneously resolved. At 3 months follow up, he is reported to be normal and back at school. Case 2: A sixteen-year old girl with retroviral infection on treatment presented with a five-day history of headache preceded by a cough of two weeks. She had bilateral papilloedema with no focal neurological signs. MRI brain was normal. LP revealed raised opening CSF pressure at 25 cm with normal cells, chemistry and cultures confirming the diagnosis of idiopathic intracranial hypertension. Blood Mp titre (GPAT) was 5120. She received a three week course of Clarithromycin. Follow up at 4 weeks showed normal fundoscopy with disappearance of headaches. Conclusion: Mp infection should be considered as a differential diagnosis in children with an unusual neurological presentation as the good outcome depends on early diagnosis and specific therapy.

An outbreak of mycoplasma pneumoniae pneumonia in a kindergarten

To study the epidemiological and clinical features of the mycoplasma pneumoniae pneumonia (MPP) that occurred in a single class of a kindergarten in Beijing in July 2006. The environment and the attendance record of the kindergarten from the beginning of August 2005 to the end of July 2006 were investigated, and the sick status of the children absent for illness were interviewed by face to face or telephone through their parents. The disease data of the in-patient children with MPP were collected through questionnaires and analyzed. Serological screening for MP was performed with the Serodia Myco II gelatin particle agglutination test (Fujirebio, Japan). In mid-July 2006, in a day-care kindergarten with 3 grade classes, 3 out of 25 six-year-old children in the top class were hospitalized within 4 days and diagnosed as MPP. A total of 8 children had the symptoms of fever and cough during late May and mid-July in 2006, 5 children conduct chest radiographs and all had pneumonia, all these five children showed antibody positive for MP, 3 of them showed a more than 4-fold increase in antibody titer to MP in serum. There were no pneumoniae cases in the other two classes during the same period, and no pneumoniae cases happened among the teachers in the top class and the parents of the 5 pneumoniae children. All the children were moved to this classroom temporarily with limited ventilation and sunshine in March 2006. After improvement of the ventilation in the classroom, no additional pneumoniae cases occurred in the top class till the early September 2006. The 5 MPP children showed neither sneeze and nasal obstruction, nor skin rash, earache and any other extrapulmonary complication, and their peripheral white blood cell count was in the normal range (3.9 - 7.7) x 10(9). The MPP outbreak in a kindergarten was caused by poor ventilation of the temporary classroom. MP infection in children is liable to cause pneumonia.

HLA profile in patients with AIDS and tuberculosis

Studies carried out in various populations have reported an association between some HLA specificities and susceptibility to tuberculosis. We investigated the class I and class II HLA profile in Brazilian patients of various ethnic backgrounds who had AIDS and tuberculosis. Twenty-two adult patients with AIDS and tuberculosis (Group I), 103 patients with AIDS without tuberculosis (Group II) and 423 healthy individuals not infected with HIV (Group III) were evaluated. Diagnosis of HIV infection was made by ELISA, confirmed by a gelatin particle agglutination test. Diagnosis of tuberculosis was made based on clinical/radiological presentation and direct bacilloscopy or clinical specimen cultures. Class I antigens were typed by microlymphotoxicity. Class II alleles were characterized by the polymerase chain reaction (PCR). Differences in frequency of HLA specificities between groups were found in the following antigens/alleles: Group I x Group II: HLA-A31 - p=0.026; HLA-B41 - p= 0.037; HLA-DRB1*10 - p=0.037; HLA-DQB1*5 - p=0.009. Group I x Group III (control): HLA-A31 - p = 0.000008; odds ratio (OR)=31.75; HLA-B41 - p=0.003; HLA-DQB1*5 - p=0.02. HLA-A31 and HLA-B41 antigens and the HLA-DRB1*10 and HLA-DQB1*05 alleles were over-represented in patients with AIDS and tuberculosis (Group I), suggesting that these HLA molecules are associated with susceptibility to tuberculosis in Brazilian patients with AIDS.

麻疹ゼラチン粒子凝集 (PA) 抗体の特性-中和 (NT) 抗体及び血球凝集抑制 (HI) 抗体との比較並びにIgG avidityとの関連

Changes in gelatin particle agglutination (PA), hemagglutination inhibition (HI), and neutralization (NT) antibodies were compared using sera from 124 individuals collected between 3 weeks and 10 years after measles vaccination, and the relationship between these changes and IgG avidity was studied. PA, HI, and NT antibodies peaked 4-5 months after vaccination. The rate of increase in mean antibody titer from 0-1 months after vaccination to peak levels was 1.7-fold for NT, 1.5-fold for HI, and 7.4-fold for PA antibodies. Peak mean antibody titer was 2(11.8) for PA, 2(6.7) for NT and 2(6.7) for HI antibodies. After peaking PA antibodies changed in parallel with NT and HI antibody titers, and correlated strongly with both antibodies (r = 0.801 and 0.840). In contrast, NT and HI antibodies were consistent throughout the period. IgG avidity increased for 4-5 months following vaccination, peaking at 45%, and remaining constant at 40-50% for the next 10 years. PA antibody is strongly influenced by IgG avidity, unlike NT and HI antibodies. Due to the effects of IgG avidity, PA antibodies increase more significantly than NT and HI antibodies as IgG antibodies mature following vaccination, resulting in a weak correlation between PA and NT or HI antibodies. Following the increase in IgG avidity to maturation, PA antibodies correlated strongly with NT and HI antibodies. PA assay detected IgM antibodies against measles virus more efficiently than the NT test. The PA assay thus differs from conventional, commonly used NT and HI assays. PA assay is simple and rapid, making it very useful for detecting measles antibodies provided that its unique features are taken into accounts.

Unusual Finding of HTLV-I Infection among Amazonian Amerindians

Human T-cell lymphotropic virus type II is a retrovirus endemic in Amerindian communities throughout the American continent, although some Amerindian groups that apparently emerged from the same ethnic root as HTLV-II carriers do not secrete antibodies against the virus and show very low prevalence for human T-cell lymphotropic virus type I. In this study, sera from 487 Amazonian amerinds were screened for HTLV type I and II antibody by the gelatin particle agglutination assay and ELISA and confirmed by Western blot and indirect immunofluorescence assay. None was positive for HTLV type II. One young healthy male of Waiãpi ethnicity was reactive with HTLV-I and was confirmed by Western blot assay and indirect immunofluorescence test. The absence of HTLV type II infection among these Amerindian communities would suggest a behavior pattern distinct from other groups in the American continent. Also, the very low prevalence of HTLV type I infection among these ethnic groups probably indicates contamination by blood transfusion (external transmission route).

妊婦における麻疹中和抗体価, HI抗体価, PA抗体価の相関と各測定法の発症予防レベル

When measles antibody levels among pregnant women were measured with measles hemagglutinin inhibition (HI), 31% of subjects had negative HI antibody titers. When the same blood samples were tested with measles gelatin particle agglutination (PA) and neutralizing (NT), the percentages of those with negative antibody levels were 1% and 3%. We conducted the correlation between antibody titers measured by the three types of titration. Correlation between NT and HI antibody titers higher than 1:8 and that between NT and PA antibody titers were good, but 81% of subjects whose HI antibody titer was below 1:8 and all women with HI antibody of 1:8 were found to have NT antibody titer higher than 1:4. NT antibody titer higher than 1:4 was found in 95% of women having PA antibody titer of 1:256 and in 99% of those with PA antibody titer of 1:512. Based on the relationships to measles NT antibody level, the majority of subjects with HI antibody titer higher than 1:8 or PA antibody level higher than 1:512 was reasonably assumed to be protected against clinical measles. PA seemed superior to HI in finding subjects with insufficient immunity against measles, because the former detects weak immunity more efficiently than the latter.

Comparative Assessment of the Gelatin Particle Agglutination Test and an Enzyme-Linked Immunosorbent Assay for Diagnosis of Strongyloidiasis

The performances of the gelatin particle agglutination test (GPAT) and enzyme-linked immunosorbent assay (ELISA) for the diagnosis of strongyloidiasis with reference to the results of the agar plate culture technique (APCT) were evaluated with samples from 459 individuals from communities in northeast Thailand where strongyloidiasis is endemic. The prevalence of strongyloidiasis in five sample groups determined by GPAT varied between 29.3 and 61.5% (mean, 38.8%). ELISA and APCT, employed concurrently, gave lower prevalence rates of 27.5% (range, 21.6 to 42.1%) and 22.7% (range, 12.7 to 53.8%), respectively. By using APCT as the standard method, the sensitivity of GPAT was generally higher than that of ELISA (81 versus 73%). The specificity of GPAT was slightly lower than that of ELISA (74 versus 86%). The resulting GPAT titers exhibited positive linear relationships with the ELISA values (optical density at 490 nm) (P < 0.05), which suggests that the GPAT titer also reflects the levels of specific antibody comparable to those reflected by the ELISA values. Based on the relative ease and simplicity of use of the technique as well as the acceptable rates of sensitivity and specificity of the test, GPAT is more practical for screening for strongyloidiasis than the conventional ELISA.

Using the premarital examination for population-based surveillance for HIV in China: a pilot study.

All couples attending the premarital examination at four selected sites in Zhejiang and Yunnan provinces in China were included in this study. Blood from 9952 individuals was tested for HIV-1 using a gelatin particle agglutination technique. There were no HIV-positive individuals in Zhejiang. In Yunnan, 28 of 3742 individuals were positive, a prevalence of 0.75%. The premarital examination should be used for voluntary counselling and testing and anonymous surveillance for HIV in high prevalence areas.

Using the premarital examination for population-based surveillance for HIV in China

Using the premarital examination for population-based surveillance for HIV in China

Human T cell leukaemia/lymphoma virus infection in pregnant women in the United Kingdom: population study

Objective: To assess the prevalence of human T cell leukaemia/lymphoma virus (HTLV) infection in pregnant women in the United Kingdom.Design: Population study.Subjects: Guthrie card samples from babies born in 1997-8.Samples...

Plasma hydroxy metronidazole/metronidazole ratio in anti-HCV carriers with and without apparent liver disease

Aims To evaluate plasma hydroxy-metronidazole/metronidazole ratio as a dynamic liver function test in HCV-infected individuals with/without liver disease, in the absence of liver cirrhosis. Methods Metronidazole was administered intravenously in healthy volunteers, asymptomatic anti-HCV-positive blood donors, and in chronic hepatitis C patients. Serology to HCV was determined by a second generation assay and confirmed by gelatin particle agglutination test using recombinant antigens C22-3 and C200. Plasma concentration of metronidazole and hydroxy-metronidazole was measured by high performance liquid chromatography in samples collected 5, 10, 20 and 30 min following the end of metronidazole infusion. Results Chronic hepatitis C patients had abnormal liver enzymes, while healthy volunteers and anti-HCV-positive blood donors had normal liver biochemistry tests. Plasma metronidazole concentration was similar in all groups studied. Plasma hydroxy-metronidazole/metronidazole ratio was significantly reduced in HCV-infected subjects, an effect observed 10 min after the end of drug infusion. Conclusions Metronidazole clearance is impaired in anti-HCV-positive blood donors and chronic hepatitis C patients, indicating that HCV is capable of affecting liver function at early stages of the disease. The metronidazole clearance test can detect impaired liver function in HCV-infected individuals even in the absence of liver cirrhosis.

Phylogenetic Analysis of Simian T-lymphotropic Virus Type I (STLV-I) in Common Chimpanzees (Pan troglodytes): Evidence for Interspecies Transmission of the Virus between Chimpanzees and Humans in Central Africa

Serum and peripheral blood leukocytes from the chimpanzees (Pan troglodytes) of the colony of the Laboratory of Central Nervous System Studies, National Institute of Neurological Disorders and Stroke, NIH, were tested for the presence of STLV-I-specific antibodies and proviral DNA. Antibodies were determined by gelatin particle agglutination and Western blot (WB) assays utilizing HTLV-I antigens. Proviral DNA was detected by four PCR assays targeting three different regions of STLV-I genome: the fragments of theenvandpolgenes andLTR.Twenty of twenty-two DNA samples from WB-positive animals were PCR positive. None of the DNA samples from WB-negative (n= 5) and WB-indeterminate (n= 4) animals was PCR positive. The results of the nested and double nestedenvPCR tests were fully concordant; the seminestedLTRPCR test was much less sensitive. The DNA sequences from theenv(483 bp) and thepol(200 bp) genes andLTR(705 bp) were determined for six, two, and two chimpanzee STLV-I isolates, respectively. Phylogenetic analysis revealed that chimpanzee STLV-I isolates can be attributed to three clades. The first of these clades (SS-PTR1/CSA) included STLV-I isolates from the chimpanzees and West African subspecies of African green monkeys (Cercopithecus a. sabaeus). The other clades (S-PTR2 and S-PTR3) included STLV-I isolates only from chimpanzees. However, both S-PTR2 and S-PTR3 clustered together with Central African HTLV-I comprising the human/simian clade (HS-HSA/PTR). This pattern of phylogenetic clustering suggests that interspecies transmission of STLV-I occurred between chimpanzees and African green monkey subspecies as well between chimpanzees and human populations in Central Africa.

Markers of human T lymphotropic virus type I in patients with cancer of uterine cervix in Amazon, Brazil

Human T lymphotropic virus type I(HTLV-I) has been implicated in various human diseases. Serum samples of 390 Brazilian Amazonians with cancer of various types were tested for HTLV-I antibodies by Gelatin particle agglutination test, Enzyme linked immunosorbent assay and Western blotting. Of 134 sera from patients with cancer of uterine cervix, 4 were positive by all the methods. Three of these were from non-transfused patients. DNA was extracted from 2 of 4 seropositive sera that gave strong reactions and were analyzed by PCR-SSCP for HTLV-I sequences. One was positive for all HTLV-I genes tested while the other one was positive for LTR and tax and negative for gag. In view of a possible pathway of the virus by sexual contact, the involvement of HTLV-I in cervical cancer warrants further studies.

More reliable diagnosis of infection with human immunodeficiency virus type 1 (HIV-1) by detection of antibody IgGs topol andgag proteins of HIV-1 and p24 antigen of HIV-1 in urine, saliva, and/or serum with highly sensitive and specific enzyme immunoassay (immune complex transfer enzyme immunoassay): A review

Ultrasensitive enzyme immunoassays (immune complex transfer enzyme immunoassays) were developed for antibody IgGs to HIV-1 using recombinant reverse transcriptase (rRT), p17 (rp17), and p24 (rp24) as antigens. Antibody IgGs were reacted with 2,4-dinitrophenyl-recombinant antigens and recombinant antigen-beta-D-galactosidase conjugates, and the immune complexes formed, comprising the three components, were trapped onto polystyrene beads coated with (anti-2,4-dinitrophenyl group) IgG. After washing, the immune complexes were eluted from the polystyrene beads with excess of epsilon N-2,4-dinitrophenyl-L-lysine and were transferred to clean polystyrene beads coated with (antihuman IgG gamma-chain) IgG. beta-D-Galactosidase activity bound to the last polystyrene beads was assayed by fluorometry. By transfer of the immune complexes from one solid phase to another, the nonspecific binding of the beta-D-galactosidase conjugates was minimized and the sensitivity was markedly improved. The immune complex transfer enzyme immunoassays using rRT, rp17, and rp24 as antigens were 300-1,000-fold, 1,000-3,000-fold, and 30-100-fold, respectively, more sensitive than Western blotting for the corresponding antigens and 10-300-fold more sensitive than a conventional ELISA and a gelatin particle agglutination test. For urine (100 microliters), whole saliva (1 microliter), and serum (1 microliter) samples, the sensitivity and specificity of the immune complex transfer enzyme immunoassay using rRT as antigen were both 100%. However, for urine samples in which the specific activities of antibody IgG to RT, p17, and p24 were much lower than those in serum samples probably due to degradation by the kidney, a longer assay of bound beta-D-galactosidase activity or/and a concentration process for urine was required. The use of more than 1 microliter of whole saliva was recommended for reliable diagnosis of the infections, whereas 1 microliter of serum was sufficient for the purpose. The positivity with rRT as antigen could be confirmed by demonstration of antibody IgGs to p17 and p24 in most of the urine, whole saliva, and serum samples. In HIV-1 seroconversion serum panels, antibody IgG to p17 was detected as early as or even earlier than antibodies to HIV-1 by a conventional ELISA or/and a gelation particle agglutination test, whereas antibody IgGs to RT and p24 were detected as early as or later than antibody IgG to p17. Thus the uses of rRT and rp17 as antigens were advantageous over that of the other antigens for randomly collected serum samples probably long after the infection and serum samples at early stages of the infection, respectively. On the basis of these results and other reports, the immune complex transfer enzyme immunoassay was developed for simultaneous detection of p24 antigen and antibody IgGs to RT and p17 in a single assay tube, and the window period (8 weeks, although widely variable), during which diagnosis of HIV-1 infection is not possible due to the absence of detectable antibodies to HIV-1, was shortened by 2 weeks. As a result, the simultaneous detection made possible not only as early diagnosis as that by detection of p24 antigen, but also as reliable diagnosis as that by detection of antibodies to HIV-1. Finally, the immune complex transfer enzyme immunoassay has been recently improved so as to be performed within shorter periods of time (2-3 hr) with higher sensitivity, and testing many samples has become easy.