Antigen Detection Kit Research Articles

Clinical value of a rapid respiratory syncytial virus antigen detection in point-of-care testing

Objective: To evaluate the clinical value of a rapid respiratory syncytial virus (RSV) antigen detection in point-of-care testing (POCT). Method: A total of 209 specimens, including 78 throat swabs (TS) and 131 nasopharyngeal aspirates (NPAs), were collected from inpatients who visited the Children's Hospital Affiliated to the Capital Institute of Pediatrics and were diagnosed as acute respiratory infection from 5 January to 7 February, 2015. These specimens were tested for RSV by a rapid antigen detection kit which was compared with reverse transcription polymerase chain reaction (RT-PCR) and direct immunofluorescence assay (DFA) for RSV detection. Result: Compared with DFA for NPAs, the sensitivity and specificity of rapid antigen detection were 83.9% and 97.3%, respectively, with Kappa value of 0.86; Compared with RT-PCR, the sensitivity (NPAs, 74.2%; TS, 77.8%) and specificity (NPAs, 100.0%; TS, 92.0%) of rapid antigen detection were high, too, with Kappa value of 0.74 in NPAs and 0.62 in TS. However, the RSV positive rate of rapid antigen detection in TS (21.7%) from pediatric patients with acute lower respiratory tract infection was lower than that in NPAs (78.3%), as well as that of RT-PCR (7.3% in TS verse 78% in NPAs). The RSV rapid antigen detection kit can be finished in about 10 minutes. Conclusion: With characteristics of high specificity, high sensitivity, being rapid, efficient and easy to operate in comparison with DFA and RT-PCR, RSV rapid antigen detection in this study is suitable for POCT. For pediatric patients with acute respiratory tract infection, NPA was better than TS for RSV detection.

The Evaluation of the Sputum Antigen Kit in the Diagnosis of Pneumococcal Pneumonia.

Objective A previously developed sputum antigen detection kit for Streptococcus pneumoniae enabled the early diagnosis of pneumococcal pneumonia using sputum samples. We conducted a prospective study to compare the sensitivity of the sputum and urinary antigen kits. Methods Pneumonia patients who were treated from April 2014 to September 2015 were recruited for the present study. Patients with pneumococcal pneumonia who could not participate in the prospective arm of the study were analyzed in the retrospective arm. Results Nine of the 69 participants in the prospective study had pneumococcal pneumonia. The sputum antigen kit results correlated well with the sputum culture results. The sensitivity of the sputum antigen kit was 88.9% (8/9), which was higher than that of the urinary antigen kit (5/9; 55.6%). When patients from the retrospective arm of the study were included, the sensitivity of the sputum culture was 93.5% (29/31), which was significantly higher than that of the urinary antigen kit (19/31; 60.6%). False positives were obtained using the sputum antigen kit in four cases. Three of the four false positives were suspected to have resulted from the administration of antibiotics prior to the use of the kit; the remaining case likely occurred due to a false reaction to S. milleri-induced pyothorax. Conclusion Collectively, our findings suggest that the sputum antigen kit has a higher sensitivity for detecting S. pneumoniae than the urinary antigen kit. However, the prior administration of antibiotics can render the sputum culture results negative or lead to a false-positive result.

Comparative Sensitivities and Specificities of Four Rapid Influenza A Antigen Detection Kits for Detection of H1N1, H3N2 and H5N1

<p>Influenza viruses cause seasonal epidemics associated with high morbidity and mortality. Rapid diagnostic tests for the detection of pandemic influenza A virus are valuable for their ease using and accurate diagnosis of influenza. Many rapid influenza diagnostic kits were introduced recently. Hence, the sensitivities and specificities of them for testing influenza viruses need to monitor. In this study, the sensitivities and specificities of four diagnostic immunochromatographic assay kits for H1N1, H3N2, and H5N1 were evaluated. For the detection of the three H1N1, three H3N2 and one H5N1 virus line, rapid diagnostic tests exhibited excellent specificity (all positive). And no false-positive results were obtained. They differed in respect to the sensitivity, especially in the lower haemagglutinin titer. However, all of them achieve the requirements of National Institutes for food and drug Control (NIFDC). Commercial influenza immunochromatographic assay kits are useful tools for the rapid diagnosis of influenza. Nonetheless, confirmatory testing is always recommended.</p>

Prevalence of Occult Hepatitis C Virus in Blood Donors in Zagazig City Blood Banks

Background: Egypt is reported as the country of highest incidence of HCV worldwide. The high rate of new cases reported require investigating uncommon sources of infection. Objectives: The study aimed to investigate the prevalence of occult hepatitis C infection (OCI) among blood donors from Zagazig city blood banks as a probable hidden source of transmission; and to evaluate HCV core Ag detection as a method for diagnosis of occult hepatitis C infection. Methodology: One hundred and forty blood donors from Zagazig university blood bank were incorporated into this study. Reverse transcription nested polymerase chain reaction from Peripheral Blood Monocyte (PBMC) and plasma obtained from subjects was done using HCV specific primers and HCV core antigen was detected using commercial ELISA kit. Results & Conclusion: HCV RNA was detected in PBMC extracted from 10 subjects (7.1 %). Two of them were also positive in plasma (1.4%). The overall incidence of OCI was 8/140 (5.7%). Out of them only one was also identified by ELISA HCV core antigen detection kit. The Comparison between ELISA technique for detection of HCV core antigen and nested PCR revealed sensitivity 30%, specificity 99.2% in PBMC and sensitivity 100%, specificity 98.6% in Plasma.

Evaluation of the rapid immunochromatographic ODK0501 assay for Streptococcus pneumoniae antigen detection with nasopharyngeal swabs: preliminary report.

BackgroundEarly identification and control of pathogenic bacteria are important in the treatment of pneumonia. Currently, two rapid antigen detection kits for pneumococcal pneumonia are available: one uses urine samples and the other, named RAPIRUN® S. pneumoniae, uses sputum samples. RAPIRUN® has shown high sensitivity with nasopharyngeal swab samples from pediatric patients. In this study, we investigated the performance of RAPIRUN® with nasopharyngeal swabs from adult patients.MethodsAll adult patients diagnosed with pneumonia from November 2011 to April 2012 in St. Luke’s International hospital were included in this cross-sectional study. Single sputum, nasopharyngeal swab, and urine samples obtained from patients were investigated using a rapid antigen detection kit. Sputum and blood cultures were also evaluated. We compared the characteristics of pneumococcal pneumonia patients diagnosed using RAPIRUN with a nasopharyngeal swab to those patients diagnosed using other methods. Sensitivity and specificity were also calculated.ResultsSeventeen out of 60 patients with pneumonia were diagnosed with pneumococcal pneumonia. In 4 out of the 17 cases, a positive test result was obtained using RAPIRUN with a nasopharyngeal swab. The sensitivity and specificity were 23.5 and 100 %, respectively.ConclusionRAPIRUN performed with nasopharyngeal swabs from adult patients exhibited lower sensitivity for the diagnosis of pneumococcal pneumonia than the other compared methods. The causative pathogen of pneumonia should be identified using not only sputum cultures or rapid antigen detection kits but also clinical features or gram staining of sputum.

Evaluation of the rapid immunochromatographic ODK0501 assay for Streptococcus pneumoniae antigen detection with nasopharyngeal swabs: preliminary report

Background: Early identification and control of pathogenic bacteria are important in the treatment of pneumonia. Currently, two rapid antigen detection kits for pneumococcal pneumonia are available: one uses urine samples and the other, named RAPIRUN® S. pneumoniae, uses sputum samples. RAPIRUN® has shown high sensitivity with nasopharyngeal swab samples from pediatric patients. In this study, we investigated the performance of RAPIRUN® with nasopharyngeal swabs from adult patients. Methods: All adult patients diagnosed with pneumonia from November 2011 to April 2012 in St. Luke’s International hospital were included in this cross-sectional study. Single sputum, nasopharyngeal swab, and urine samples obtained from patients were investigated using a rapid antigen detection kit. Sputum and blood cultures were also evaluated. We compared the characteristics of pneumococcal pneumonia patients diagnosed using RAPIRUN with a nasopharyngeal swab to those patients diagnosed using other methods. Sensitivity and specificity were also calculated. Results: Seventeen out of 60 patients with pneumonia were diagnosed with pneumococcal pneumonia. In 4 out of the 17 cases, a positive test result was obtained using RAPIRUN with a nasopharyngeal swab. The sensitivity and specificity were 23.5 and 100 %, respectively. Conclusion: RAPIRUN performed with nasopharyngeal swabs from adult patients exhibited lower sensitivity for the diagnosis of pneumococcal pneumonia than the other compared methods. The causative pathogen of pneumonia should be identified using not only sputum cultures or rapid antigen detection kits but also clinical features or gram staining of sputum.

A novel method for rapid detection of Streptococcus pneumoniae antigens in blood.

In this study, we used "RAPIRUN(®)Streptococcus pneumoniae HS (otitis media/sinusitis) (RAPIRUN-HS)," a rapid S. pneumoniae antigen detection kit, to investigate methods for detecting S. pneumoniae antigens in blood of 32 bacterial pneumonia patients. We simultaneously performed PCR to detect S. pneumoniae in blood samples. The results of these tests were compared based on pneumonia severity, determined using the Pneumonia Severity Index (PSI) score classification. Four S. pneumoniae PCR-positive patients of the six severe pneumococcal pneumonia patients (PSI risk class IV/V) also tested positive using RAPIRUN-HS. Twenty-four mild to moderate pneumonia patients (PSI risk class I-III) were S. pneumoniae PCR-negative; of these, 21 tested negative using RAPIRUN-HS. The pneumococcal pneumonia patients testing positive using RAPIRUN-HS had low leukocyte counts and elevated C-reactive protein and procalcitonin levels, indicating that RAPIRUN-HS results were correlated with pneumonia severity. The time course evaluations of the laboratory tests for severe pneumococcal pneumonia patients showed that RAPIRUN-HS and S. pneumoniae PCR yielded positive results earlier than the changes in procalcitonin and IL-6. Thus, concomitant pneumococcal bacteremia was strongly suspected in patients testing positive using RAPIRUN-HS. In conclusion, RAPIRUN-HS may be useful for determining whether to admit patients into hospitals and selecting the appropriate antimicrobial agents.

Sensitivities of Respiratory Syncytial Virus Antigen-detection Kits Commercially Available in Japan

Respiratory syncytial virus (RSV) antigen-detection kits are used in clinical settings in Japan. Here, we compared the sensitivities of 12 different kits that are commercially available in Japan. Notably, these kits were developed based on the principle of immunochromatography. The comparison was performed using six different test specimens：standard laboratory strains of RSV subgroups A and B, and clinical specimens of nasal aspirates from patients infected with RSV subgroups A or B. The specimens were serially diluted with medium at half log concentration, and the dilutions were applied to the kit tests. The minimum detection limit was determined for each kit and for every specimen by investigating the maximum dilution rate for acquiring positive result. The absolute minimum detection limits were calculated based on the viral RNA copy number of the specimens and the maximum dilution rate ranged from 107 to 109 copies/mL, depending on the specimens and kits. Thus, the sensitivity was revealed to differ among the viral specimens examined using each kit and among the kits used to examine each viral specimen, though the difference was not significant and revealed a maximum of only 10 times. The results were compared with the geometric mean values of the results for all 12 kits which were separately calculated for all 6 specimens. Consequently, some kits with lower or higher sensitivities to all the tested specimens were identified, suggesting that some general differences in sensitivity exist among commercially available RSV antigen-detection kits, although the differences are not significant. Of course, selecting kit with a higher sensitivity would be preferable, but no large differences in sensitivity among the available kits examined in the current study. Therefore, other factors such as cost-effectiveness, convenience, time required for testing, etc., can be taken into account when selecting a kit for use in clinical settings.

Prevalence of canine Parvo virus infection in street dogs using rapid antigen detection Kit

Canine parvovirus is one of the most common infectious diseases of dogs. A study was carried out to diagnose the infection of canine parvovirus in street dogs from different places of Mymensingh Town. Rectal samples were collected from January to April, 2015. A total of 114 rectal swabs were collected conveniently from street dogs of Mymensingh. The samples were diagnosed using RapiGEN Canine Parvo Virus Ag Test Kit. The association of CPV infection with demographic variables was assessed by Chisquare test. The overall prevalence of CPV was 32.0% in dogs. The prevalence of parvovirus infection was found to be significantly higher in puppies and 6 months of age (58.3%) than those >24 months of age (p=0.005). The prevalence of canine parvovirus infection also varied significantly in different study area (p=0.003). The prevalence of canine parvovirus infection was higher in male (34.4%) than that in female (30.2%) but it was not statistically significant.Res. Agric., Livest. Fish.2(3): 459-464, December 2015

The Intrathecal Antibody Response in Multiple Sclerosis Brain Does Not React Against Measles Virus

liminarily identified as a phlebovirus transmitted by the sand fly Lutzomyia anthophora. RGV is not known to cause disease in humans, but it could be detected by assays designed for HRTV or other phleboviruses. The goal of this study was to determine antigenic cross-reaction between RGV and other phleboviruses. A commercially available ELISA based sand fly fever antigen detection kit was tested for the ability to detect RGV and other New and Old-World phleboviruses, including attenuated Rift valley fever virus (RVFV) strain MP12, Punta Toro virus (PTV), Toscana virus, Aguacate virus, Anhanga virus, Arumowot virus, and Chagres virus. Immunocytochemistry and Western blotting were used to detect cross reactions between RGV, MP12, and PTV using rabbit anti-RVFV nucleocapsid protein and glycoproteins GC and GN, mouse monoclonal anti-PTV, and sheep polyclonal anti-MP12. The ELISA test detected cross reactivity for all phleboviruses excluding RGV, but Western blotting detected the presumed RGV nucleocapsid protein (N) using rabbit anti-RVFV-N serum, RGV-infected cells were also identified when labeled with this antibody. Our findings demonstrate assay specific antigenic cross reactivity between these phleboviruses, thus further characterization of the molecular targets of the cross-reaction is required for proper interpretation of serological assays.

Further Characterization of Rio Grande Virus and Potential for Serological Cross Reactivity with other Phleboviruses

Members of the genus Phlebovirus (family Bunyaviridae ) are new and emerging disease pathogens of humans and animals. Newly identified viruses include Heartland virus (HRTV), Lone Star virus in the USA, and Severe Fever with Thrombocytopenia Syndrome virus in Asia. Assays to support surveillance, epidemiologic studies, and diagnosis of these viruses may also detect related viruses within the genus, confounding interpretation. Rio Grande virus (RGV) was isolated in 1973 from southern plains woodrats ( Neotoma micropus ) in the United States and has been preliminarily identified as a phlebovirus transmitted by the sand fly Lutzomyia anthophora . RGV is not known to cause disease in humans, but it could be detected by assays designed for HRTV or other phleboviruses. The goal of this study was to determine antigenic cross-reaction between RGV and other phleboviruses. A commercially available ELISA based sand fly fever antigen detection kit was tested for the ability to detect RGV and other New and Old-World phleboviruses, including attenuated Rift valley fever virus (RVFV) strain MP12, Punta Toro virus (PTV), Toscana virus, Aguacate virus, Anhanga virus, Arumowot virus, and Chagres virus. Immunocytochemistry and Western blotting were used to detect cross reactions between RGV, MP12, and PTV using rabbit anti-RVFV nucleocapsid protein and glycoproteins GC and GN, mouse monoclonal anti-PTV, and sheep polyclonal anti-MP12. The ELISA test detected cross reactivity for all phleboviruses excluding RGV, but Western blotting detected the presumed RGV nucleocapsid protein (N) using rabbit anti-RVFV-N serum, RGV-infected cells were also identified when labeled with this antibody. Our findings demonstrate assay specific antigenic cross reactivity between these phleboviruses, thus further characterization of the molecular targets of the cross-reaction is required for proper interpretation of serological assays.

Sequence Diversity of VP4 and VP7 Genes of Human Rotavirus Strains in Saudi Arabia.

Group A rotavirus is responsible for inducing severe diarrhea in young children worldwide. Rotavirus vaccines are used to control the disease in many countries. In the current study, the sequences of human rotavirus G and P types in Saudi Arabia are reported and compared to different relevant published sequences. In addition, the VP4 and VP7 genes of the G1P[8] strains are compared to different antigenic epitopes of the rotavirus vaccines. Stool samples were collected from children under 2 years suffering from severe diarrhea. Screening of the rotavirus-positive samples was performed with rapid antigen detection kit. RNA was amplified from rotavirus-positive samples by reverse transcriptase polymerase chain reaction assay for both VP4 and VP7 genes. Direct sequencing of the VP4 and VP7 genes was conducted and the obtained sequences were compared to each other and to the rotavirus vaccines. Both G1P[8] G1P[4] genotypes were detected. Phylogenetic analysis revealed that the detected strains belong to G1 lineage 1 and 2, P[8] lineage 3, and to P[4] lineage 5. Multiple amino acid substitutions were detected between the Saudi RVA strains and the commonly used vaccines. The current findings emphasize the importance of the continuous surveillance of the circulating rotavirus strains, which is crucial for monitoring virus evolution and helping in predicting the protection level afforded by rotavirus vaccines.

Virus detection and cytokine profile in relation to age among acute exacerbations of childhood asthma

BackgroundLittle information is available regarding eosinophil activation and cytokine profiles in relation to age in virus-induced bronchial asthma. We therefore explored the association between age, respiratory viruses, serum eosinophil cationic protein (ECP), and cytokines/chemokines in acute exacerbations of childhood asthma. MethodsWe investigated viruses in nasal secretions from 88 patients with acute exacerbation of childhood asthma by using antigen detection kits and/or RT-PCR, followed by direct DNA sequencing analysis. We also measured peripheral eosinophil counts, and the serum levels of ECP and 27 types of cytokines/chemokines in 71 virus-induced acute asthma cases and 13 controls. ResultsViruses were detected in 71(80.7%) of the 88 samples. The three major viruses detected were rhinoviruses, RS viruses, and enteroviruses; enteroviruses were found to be dominant in patients aged ≥3 years. There was no change in the levels of rhinoviruses and RS viruses between the two age groups, defined as children aged <3 years and children aged ≥3 years. Serum concentrations of ECP, IL-5, and IP-10 were significantly elevated in virus-induced acute asthma cases compared with controls. Serum ECP values were significantly higher in patients with virus-induced asthma at age ≥3 years compared with those aged <3 years. Among the 27 cytokines/chemokines, serum IP-10 was significantly higher in virus-induced asthma in patients <3 years than in those ≥3 years. Serum ECP and IL-5 production correlated significantly with age, whereas serum IP-10 showed an inverse correlation with age. ConclusionsAge-related differences in cytokine profiles and eosinophil activation may be related to virus-induced acute exacerbations of childhood asthma.

Prevalence study and genetic typing of bovine viral diarrhea virus (BVDV) in four bovine species in China.

To determine the nationwide status of persistent BVDV infection in different bovine species in China and compare different test methods, a total of 1379 serum samples from clinical healthy dairy cattle, beef cattle, yaks (Bos grunniens), and water buffalo (Bubalus bubalis) were collected in eight provinces of China from 2010 to 2013. The samples were analyzed using commercial antibody (Ab) and antigen (Ag) detection kits, and RT-PCR based on the 5’-UTR and Npro gene sequencing. Results showed that the overall positive rates for BVDV Ab, Ag and RT-PCR detection were 58.09% (801/1379), 1.39% (14/1010), and 22.64% (146/645), respectively, while the individual positive rates varied among regions, species, and farms. The average Ab-positive rates for dairy cattle, beef cattle, yaks, and water buffalo were 89.49% (298/333), 63.27% (248/392), 45.38% (236/520), and 14.18% (19/134), respectively, while the Ag-positive rates were 0.00% (0/116), 0.77% (3/392), 0.82% (3/368), and 5.97% (8/134), respectively, and the nucleic acid-positive rates detected by RT-PCR were 32.06% (42/131), 13.00% (26/200), 28.89% (52/180), and 19.40% (26/134), respectively. In addition, the RT-PCR products were sequenced and 124 5’-UTR sequences were obtained. Phylogenetic analysis of the 5’-UTR sequences indicated that all of the 124 BVDV-positive samples were BVDV-1 and subtyped into either BVDV-1b (33.06%), BVDV-1m (49.19%), or a new cluster, designated as BVDV-1u (17.74%). Phylogenetic analysis based on Npro sequences confirmed this novel subtype. In conclusion, this study revealed the prevalence of BVDV-1 in bovine species in China and the dominant subtypes. The high proportion of bovines with detectable viral nucleic acids in the sera, even in the presence of high Ab levels, revealed a serious threat to bovine health.

English

BACKGROUND: Malaria is the most important protozoan disease in India. The mortality and morbidity associated with this disease is considerably high whereas only limited diagnostic modalities are available in India. AIMS: To compare the conventional peripheral smear examination with Quantitative buffy coat (QBC) and rapid antigen detection kits. MATERIALS & METHODS: In the present study a total of 200 patients with clinically suspected malaria are screened with various techniques including conventional peripheral smear examinations with Giemsa, Leishman and JSB stain and newer modalities like Quantitative buffy coat testing and rapid antigen detection kits detecting PLDH. RESULTS: Among all these methodologies QBC test has shown highest sensitivity and antigen detection kit showed least sensitivity in the diagnosis of malaria.

Case Report and Literature Review: Podoconiosis in Southwestern Uganda

Aims: This report presents one confirmed and two suspected cases of podoconiosis in the Kabale region of southwestern Uganda. Podoconiosis has not previously been described in Uganda outside of the eastern region bordering Kenya. The aim of this case report is to increase awareness of the condition in order to enhance prevention and treatment efforts. Case Study Dwek et al.; IJTDH, 9(3): 1-7, 2015; Article no.IJTDH.17672 2 Presentation of Cases: Podoconiosis is associated with chronic barefoot exposure to red volcanic soil, with greater prevalence in high-altitude, impoverished areas of the tropics. This report describes one confirmed case and two suspected cases. Case 1 was confirmed by a negative filarial antigen detection test. Cases 2 and 3 had negative filarial smears, but antigen detection kits were not available onsite at the time. However, the altitude at which all three patients live (>1500 masl) makes filarial disease unlikely. Discussion: Podoconiosis has not been previously reported in the region, and thus may be underdiagnosed due to a low index of suspicion among clinicians. Using adequate footwear is an important component of prevention. However, limited financial resources present a significant barrier to the use of footwear. Understanding community attitudes towards causes and risk factors is also integral to effective prevention. Conclusion: Podoconiosis has a high potential for elimination, as it is preventable and treatable in the early stages with consistent use of footwear and regular foot-washing. In addition, increased awareness among physicians and clinicians of the presence of the disease in this area can lead to early detection and treatment.

Usefulness of The Pneumococcal Antigen Detection Kit in Acute Rhinosinusitis

Usefulness of The Pneumococcal Antigen Detection Kit in Acute Rhinosinusitis

病院調理従事者におけるノロウイルス対策 &amp;mdash;迅速抗原検査とリアルタイムPCR検査の比較&amp;mdash;

病院調理従事者におけるノロウイルス対策 &amp;mdash;迅速抗原検査とリアルタイムPCR検査の比較&amp;mdash;

A phylogenetically distinct Middle East respiratory syndrome coronavirus detected in a dromedary calf from a closed dairy herd in Dubai with rising seroprevalence with age

Middle East respiratory syndrome coronavirus (MERS-CoV) was detected by monoclonal antibody-based nucleocapsid protein-capture enzyme-linked immunosorbent assay (ELISA), RNA detection, and viral culture from the nasal sample of a 1-month-old dromedary calf in Dubai with sudden death. Whole genome phylogeny showed that this MERS-CoV strain did not cluster with the other MERS-CoV strains from Dubai that we reported recently. Instead, it formed a unique branch more closely related to other MERS-CoV strains from patients in Qatar and Hafr-Al-Batin in Saudi Arabia, as well as the MERS-CoV strains from patients in the recent Korean outbreak, in which the index patient acquired the infection during travel in the eastern part of the Arabian Peninsula. Non-synonymous mutations, resulting in 11 unique amino acid differences, were observed between the MERS-CoV genome from the present study and all the other available MERS-CoV genomes. Among these 11 unique amino acid differences, four were found in ORF1ab, three were found in the S1 domain of the spike protein, and one each was found in the proteins encoded by ORF4b, ORF5, envelope gene, and ORF8. MERS-CoV detection for all other 254 dromedaries in this closed dairy herd was negative by nucleocapsid protein-capture ELISA and RNA detection. MERS-CoV IgG sero-positivity gradually increased in dromedary calves with increasing age, with positivity rates of 75% at zero to three months, 79% at four months, 89% at five to six months, and 90% at seven to twelve months. The development of a rapid antigen detection kit for instantaneous diagnosis is warranted.

Isolation and biological characterization of human immunodeficiency virus type 1 from Cubans asymptomatic patients

Isolation and biological characterization of human immunodeficiency virus type 1 from Cubans asymptomatic patients