AIDS as a zoonosis? Confusion over the origin of the virus and the origin of the epidemics

Based on findings demonstrating the simian ancestry of HIV, AIDS has been reported to be a zoonosis. However, this theory has never been proved and must seriously be questioned. Several arguments show that HIV-AIDS is not a zoonosis. (i) If AIDS were a zoonosis, there must be evidence of AIDS being directly acquired from an animal species, as is rabies, a disease that is directly acquired from animals. (ii) Despite long-term and frequent human exposure to SIV-infected monkeys in Africa, only 11 cross-species transmission events are known, and only four of these have resulted in significant human-to-human transmission, generating HIV-1 groups M and O and HIV-2 groups A and B. The closest relatives of SIVcpz (HIV-1 group N) and of SIVsm (HIV-2 groups C-H) are extremely rare, with only six HIV-1 group N-infected patients and only single individuals known to be infected by HIV-2 groups C-H. SIV, while capable of cross-species transmission, is thus poorly adapted for disease and epidemic spread. If AIDS were a zoonosis that is capable of significant human-to-human spread, there would be a plethora of founder subtypes and groups. (iii) Human exposure to SIV is thousands of years old, but AIDS emerged only in the 20th century. If AIDS were a zoonosis that spread into the human population, it would have spread to the West during slave trade. (iv) Experimental transmission of SIVs to different species of monkeys is often well controlled by the new host, showing that the virus and not the disease is transmitted. Therefore, we conclude that cross-species transmission of SIV does not in itself constitute the basis for a zoonosis. Transmission per se is not the major requirement for the generation of the AIDS epidemic. All HIVs do derive from simian species, but AIDS does not qualify as a zoonosis and this explanation cannot in itself account for the origin of AIDS epidemic. It is important to distinguish AIDS from true zoonoses (e.g. rabies) because research is needed to understand the processes by which animal viruses cause sustained human-to-human transmission, epidemics and even pandemics. Much is known about emerging viruses, but almost nothing is known about emerging viral diseases.     

Factors Associated with Severe Human Rift Valley Fever in Sangailu,Garissa County,Kenya

BackgroundMosquito-borne Rift Valley fever virus (RVFV) causes acute, often severe, disease in livestock and humans. To determine the exposure factors and range of symptoms associated with human RVF, we performed a population-based cross-sectional survey in six villages across a 40 km transect in northeastern Kenya.Conclusions/SignificanceOur results demonstrate that a significant proportion of the population in northeastern Kenya has been infected with RVFV. Village and certain animal husbandry activities were associated with more severe disease. Older age, male gender, herder occupation, killing and butchering livestock, and poor visual acuity were useful markers for increased RVFV infection. Formal vision testing may therefore prove to be a helpful, low-technology tool for RVF screening during epidemics in high-risk rural settings.     

Virology of the family Togaviridae

Many pathogens important for medicine, veterinary medicine or public health belong to the genera alphavirus and rubivirus within the family Togaviridae. 29 species of alphaviruses have been reported, and most of them are arboviruses. Chikungnya virus re-emerged in Kenya in 2004 and the epidemics spread to the Indian Ocean islands and many countries in South Asia, South-East Asia and Europe. On the other hand, rubella virus, a sole member of the genus rubivirus, is the causative agent of rubella and congenital rubella syndrome (CRS). Because human is only a natural host of the virus and effective live attenuated vaccines are available, immunization activities are strengthened globally to eliminate rubella and CRS, together with measles.     

Persistence of Tanapox in Tana River Valley

Sera collected from inhabitants of the Tana River valley in 1971 were examined for antibody to tanapox virus. Neutralizing antibody was present in 16·3%. The levels of antibody and its presence in two children under the age of 10 years indicated that infection had been occurring in the area since the reported outbreak in 1962. A comparison of the incidence and distribution of antibodies in the same sera to West Nile virus revealed marked similarities suggesting that tanapox, like West Nile virus infections, might be transmitted in the same way—namely, by a culicine mosquito.     

Side-by-Side Comparison of Gene-Based Smallpox Vaccine with MVA in Nonhuman Primates

Orthopoxviruses remain a threat as biological weapons and zoonoses. The licensed live-virus vaccine is associated with serious health risks, making its general usage unacceptable. Attenuated vaccines are being developed as alternatives, the most advanced of which is modified-vaccinia virus Ankara (MVA). We previously developed a gene-based vaccine, termed 4pox, which targets four orthopoxvirus antigens, A33, B5, A27 and L1. This vaccine protects mice and non-human primates from lethal orthopoxvirus disease. Here, we investigated the capacity of the molecular adjuvants GM-CSF and Escherichia coli heat-labile enterotoxin (LT) to enhance the efficacy of the 4pox gene-based vaccine. Both adjuvants significantly increased protective antibody responses in mice. We directly compared the 4pox plus LT vaccine against MVA in a monkeypox virus (MPXV) nonhuman primate (NHP) challenge model. NHPs were vaccinated twice with MVA by intramuscular injection or the 4pox/LT vaccine delivered using a disposable gene gun device. As a positive control, one NHP was vaccinated with ACAM2000. NHPs vaccinated with each vaccine developed anti-orthopoxvirus antibody responses, including those against the 4pox antigens. After MPXV intravenous challenge, all control NHPs developed severe disease, while the ACAM2000 vaccinated animal was well protected. All NHPs vaccinated with MVA were protected from lethality, but three of five developed severe disease and all animals shed virus. All five NHPs vaccinated with 4pox/LT survived and only one developed severe disease. None of the 4pox/LT-vaccinated animals shed virus. Our findings show, for the first time, that a subunit orthopoxvirus vaccine delivered by the same schedule can provide a degree of protection at least as high as that of MVA.     

Viral hepatitis A in lower Old World monkeys (possibility of use as a model for vaccine testing)

Morphological, virological and serological data characteristic of spontaneous hepatitis A in macaques and green monkeys have been presented. The disease similar to human hepatitis A was induced in M. iris macaques, with the virus isolated from spontaneously infected rhesus monkeys. Experimental model of hepatitis A in macaques is likely to be used for the testing of vaccines and antiviral preparations.     

Malaria epidemic early warning and detection in African highlands

Malaria epidemics have long been known to recur in the African highlands. Efforts to develop systems of early warning and detection for epidemics are outlined here with special emphasis on the Highland Malaria Project (HIMAL). This project has been conducting research on the operational implementation of a district-based surveillance and epidemic-monitoring system using a network of sentinel sites in four pilot districts of Kenya and Uganda. The potential use of weather monitoring as well as disease surveillance for effective early warning is being investigated.     

Congenital absence of the gallbladder; case report

The virus of human poliomyelitis has been demonstrated in excretions before onset of the disease, during the disease, and in convalescence. It may be confused with different viruses likely to be found in the same sources in clinical conditions resembling poliomyelitis.Immunologic differences between strains of poliomyelitis virus have been detected so that three types are now evident. The distribution of these types and their importance as causes of epidemics are not known. This multiplicity of immunologic types is an important factor in considering immunization of humans. Commercial manufacture of vaccines faces many technical problems. Recently the Coxsackie virus has been demonstrated in humans with a disease closely resembling poliomyelitis.     

Congenital Absence of the Gallbladder: Case Report

The virus of human poliomyelitis has been demonstrated in excretions before onset of the disease, during the disease, and in convalescence. It may be confused with different viruses likely to be found in the same sources in clinical conditions resembling poliomyelitis.Immunologic differences between strains of poliomyelitis virus have been detected so that three types are now evident. The distribution of these types and their importance as causes of epidemics are not known. This multiplicity of immunologic types is an important factor in considering immunization of humans. Commercial manufacture of vaccines faces many technical problems.Recently the Coxsackie virus has been demonstrated in humans with a disease closely resembling poliomyelitis.     

Hepatitis A

Hepatitis A is a disease of worldwide distribution which occurs in endemic and epidemic form and is transmitted primarily by person-to-person contact through the fecal-oral route. Common source epidemics due to contamination of food are relatively common, and water-borne epidemics have been described less frequently. The presumed etiologic agent of hepatitis A has now been visualized by immune electron microscopic (IEM) techniques in early acute-illness-phase stools of humans with hepatitis A as well as in chimpanzees experimentally infected with material known to contain hepatitis A virus. In addition, several new serologic tests for the detection of antibody against hepatitis A virus have been described. These include complement fixation and immune adherence techniques. Current data suggest that hepatitis A is caused by a single viral agent lacking the morphologic heterogeneity of hepatitis B viral components and that there may be relative antigenic homogeneity between strains of virus recovered from various parts of the world. Serologic studies to date also indicate that hepatitis A virus is not a major contributing cause in post-transfusion hepatitis.     

Heterologous prime/boost immunization of rhesus monkeys by using diverse poxvirus vectors

As the diversity of potential immunogens increases within certain classes of vectors, the possibility has arisen of employing heterologous prime/boost immunizations using diverse members of the same family of vectors. The present study was initiated to explore the use of divergent pox vectors in a prime/boost regimen to elicit high-frequency cellular immune responses to human immunodeficiency virus type 1 envelope and simian immunodeficiency virus gag in rhesus monkeys. We demonstrated that monkeys vaccinated with a recombinant modified vaccinia virus Ankara (rMVA) prime/recombinant fowlpox virus (rFPV) boost regimen and monkeys vaccinated with a recombinant vaccinia virus prime/rFPV boost regimen developed comparable cellular immune responses that were greater in magnitude than those elicited by a homologous prime/boost with rMVA. Nevertheless, comparable magnitude recall cellular immune responses were observed in monkeys vaccinated with heterologous and homologous recombinant poxvirus following challenge with the CXCR4-tropic SHIV-89.6P. Consistent with this finding, comparable levels of containment of viral replication and CD4(+) T-lymphocyte preservation were seen in these groups of recombinant poxvirus-vaccinated monkeys. This study supports further exploration of combining recombinant vectors of the same family in prime/boost immunization strategies to optimize vaccine-elicited cellular immune responses.     

Rift Valley Fever Risk Map Model and Seroprevalence in Selected Wild Ungulates and Camels from Kenya

Since the first isolation of Rift Valley fever virus (RVFV) in the 1930s, there have been multiple epizootics and epidemics in animals and humans in sub-Saharan Africa. Prospective climate-based models have recently been developed that flag areas at risk of RVFV transmission in endemic regions based on key environmental indicators that precede Rift Valley fever (RVF) epizootics and epidemics. Although the timing and locations of human case data from the 2006–2007 RVF outbreak in Kenya have been compared to risk zones flagged by the model, seroprevalence of RVF antibodies in wildlife has not yet been analyzed in light of temporal and spatial predictions of RVF activity. Primarily wild ungulate serum samples from periods before, during, and after the 2006–2007 RVF epizootic were analyzed for the presence of RVFV IgM and/or IgG antibody. Results show an increase in RVF seropositivity from samples collected in 2007 (31.8%), compared to antibody prevalence observed from 2000–2006 (3.3%). After the epizootic, average RVF seropositivity diminished to 5% in samples collected from 2008–2009. Overlaying maps of modeled RVF risk assessments with sampling locations indicated positive RVF serology in several species of wild ungulate in or near areas flagged as being at risk for RVF. Our results establish the need to continue and expand sero-surveillance of wildlife species Kenya and elsewhere in the Horn of Africa to further calibrate and improve the RVF risk model, and better understand the dynamics of RVFV transmission.     

Subtypes of human immunodeficiency virus type 1 and disease stage among women in Nairobi, Kenya

In sub-Saharan Africa, where the effects of human immunodeficiency virus type 1 (HIV-1) have been most devastating, there are multiple subtypes of this virus. The distribution of different subtypes within African populations is generally not linked to particular risk behaviors. Thus, Africa is an ideal setting in which to examine the diversity and mixing of viruses from different subtypes on a population basis. In this setting, it is also possible to address whether infection with a particular subtype is associated with differences in disease stage. To address these questions, we analyzed the HIV-1 subtype, plasma viral loads, and CD4 lymphocyte levels in 320 women from Nairobi, Kenya. Subtype was determined by a combination of heteroduplex mobility assays and sequence analyses of envelope genes, using geographically diverse subtype reference sequences as well as envelope sequences of known subtype from Kenya. The distribution of subtypes in this population was as follows: subtype A, 225 (70.3%); subtype D, 65 (20.5%); subtype C, 22 (6.9%); and subtype G, 1 (0.3%). Intersubtype recombinant envelope genes were detected in 2.2% of the sequences analyzed. Given that the sequences analyzed represented only a small fraction of the proviral genome, this suggests that intersubtype recombinant viral genomes may be very common in Kenya and in other parts of Africa where there are multiple subtypes. The plasma viral RNA levels were highest in women infected with subtype C virus, and women infected with subtype C virus had significantly lower CD4 lymphocyte levels than women infected with the other subtypes. Together, these data suggest that women in Kenya who are infected with subtype C viruses are at more advanced stages of immunosuppression than women infected with subtype A or D. There are at least two models to explain the data from this cross-sectional study; one is that infection with subtype C is associated with a more rapid disease progression, and the second is that subtype C represents an older epidemic in Kenya. Discriminating between these possibilities in a longitudinal study will be important for increasing our understanding of the role of specific subtypes in the transmission and pathogenesis of HIV-1.     

鸡痘的诊断与防治技术研究

鸡痘是危害养鸡业发展的一种传染病,不分日龄大小均可发病,肉鸡和蛋鸡均可感染,发病期1—2周,雏鸡死亡率较高,可达5％～30％不等,近年来发病率和死亡率有上升趋势,并且免疫失败的病例时有发生。为了建立接种疫苗后抗体监测手段和研究感染鸡痘病毒后抗体产生规律,我们建立了间接     

A distinct African lentivirus from Sykes' monkeys.

Asymptomatic infection with simian immunodeficiency virus (SIV) has been demonstrated in African Sykes' monkeys (Cercopithecus mitis albogularis), and virus isolation confirmed infection with a novel SIV from Sykes' monkeys (SIVsyk). Macaques inoculated with SIVsyk became persistently infected but remained clinically healthy. We utilized polymerase chain reaction amplification to generate a full-length, infectious molecular clone of SIVsyk. The genome organization of SIVsyk is similar to that of the other primate lentiviruses, consisting of gag, pol, vif, vpr, tat, rev, env, and nef. A unique feature is the absence of the highly conserved NF-kappa B binding site in the long terminal repeat. SIVsyk is genetically equidistant from other primate lentiviruses. Thus, SIVsyk represents a new group that is distinct from the four previously recognized primate lentivirus groups: human immunodeficiency virus type 1 (HIV-1), SIV from sooty mangabeys (SIVsmm) and HIV-2, SIV from African green monkeys (SIVagm), and SIV from mandrills (SIVmnd). The genetic differences between SIVsyk and SIVagm, isolates derived from monkeys of the same genus, underscore the potential for other distinct SIVs which have yet to be isolated and characterized.     

Prevalence of avian pox virus and effect on the fledging success of Laysan Albatross

ABSTRACT.   Avian pox virus ( Poxvirus avium ) is a mosquito-borne disease that occurs worldwide in a variety of bird species, but little is known about its prevalence or effect on seabirds. We monitored prevalence of pox virus and its effect on fledging success of Laysan Albatross ( Phoebastria immutabilis ) on Oahu, Hawaii, from 2003 to 2007. Pox prevalence in albatross chicks averaged 88% in years with high rainfall and 3% in years with low rainfall. Diagnosis of pox virus was clinically confirmed in two birds by Muscovy Duck ( Cairina moschata ) fibrolast cultures. Severity of infection ranged from small wart-like nodules and lesions on the bill, face, eyes, tarsus, and feet, to large tumorous growths that completely covered both eyes and caused deformation of the bill and skull. Most chicks recovered from infection, and the fledging rate in pox epizootic years (82%) did not differ from that in years with low pox prevalence (80%) or the average fledging rate on Midway Atoll (86%). Three chicks with severe infections were resighted as healthy adults on Kauai and Oahu in 2007, confirming postfledging survival of at least some birds. The high recovery rate, fledging success, and postfledging survival indicate that Laysan Albatross have strong immunity to avian pox virus.     

痘病毒载体的应用

简单介绍痘病毒载体的实际应用。其原理是通过同源重组将外源DNA插入到痘病毒基因组的非实质区域,表达的外源蛋白能正确地进行修饰,并有较高的表达效率,可刺激机体产生免疫应答。痘病毒载体作为基因工程中的重要工具,其应用极其广泛,已成功地表达了来源于植物、动物,乃至人类的许多基因。     

Dynamics of annual influenza A epidemics with immuno-selection

 The persistence of Influenza A in the human population relies on continual changes in the viral surface antigens allowing the virus to reinfect the same hosts every few years. The epidemiology of such a drifting virus is modeled by a discrete season-to-season map. During the epidemic season only one strain is present and its transmission dynamics follows a standard epidemic model. After the season, cross-immunity to next year's virus is determined from the proportion of hosts that were infected during the season. A partial analysis of this map shows the existence of oscillations where epidemics occur at regular or irregular intervals. Received: 16 February 2001 / Revised version: 11 June 2002 / Published online: 28 February 2003 Key words or phrases: Infectious disease – Influenza drift – Cross-immunity – Seasonal epidemics – Iterated map