Fatal infection of a pet monkey with Human herpesvirus

Primates and pandemics: A biocultural approach to understanding disease transmission in human and nonhuman primates

Investigations into zoonotic disease outbreaks have been largely epidemiological and microbiological, with the primary focus being one of disease control and management. Increasingly though, the human-animal interface has proven to be an important driver for the acquisition and transmission of pathogens in humans, and this requires syncretic bio-socio-cultural enquiries into the origins of disease emergence, for more efficacious interventions. A biocultural lens is imperative for the examination of primate-related zoonoses, for the human-primate interface is broad and multitudinous, involving both physical and indirect interactions that occur due to shared spaces and ecologies. I use the case example of a viral zoonotic epidemic that is currently endemic to India, the Kysanaur Forest Disease, to show how biocultural anthropology provides a broad and integrative perspective into infectious disease ecology and presents new insights into the determinants of disease outbreaks. Drawing on insights from epidemiology, political ecology, primate behavioral ecology and ethnoprimatology, this paper demonstrates how human-primate interactions and shared ecologies impact infectious disease spread between human and nonhuman primate groups.

First report on herpesvirus in black-fronted titi (Callicebus nigrifrons) kept under human care

Keeping Neotropical primates in captivity puts them at great risk of illness because of their susceptibility to human herpesvirus. This is the first report on herpesvirus in Callicebus nigrifrons that developed clinical disease and was confirmed by immunohistochemical and RT-PCR. Diagnosis and prevention are essential for the conservation of species.

Callitrichine gammaherpesvirus 3 and Human alphaherpesvirus 1 in New World Primate negative for yellow fever virus in Rio de Janeiro, Brazil

BACKGROUND

Herpesvirus transmission between humans and non-human primate (NHP) can occur through contact scratches with lesions, infected saliva, and mainly through contaminated food. Therefore, cross-infection can lead to severe illness or even death for both the animal and human. In 2017, during the yellow fever (YF) outbreak in Brazil, species of the New World Primates (NWP) from Rio de Janeiro state, tested negative for yellow fever virus (YFV) detection.

OBJECTIVES

To evaluate herpesvirus in the population NWP in Rio de Janeiro.

METHODS

To investigate, liver samples of 283 NWP, from several regions of the state of Rio de Janeiro, were tested for the herpesvirus family using a Pan-polymerase chain reaction (Pan-PCR) and sequencing.

FINDINGS

34.6% (98/283) tested positive for at least one herpesvirus; 29.3% (83/283) tested positive to Human alphaherpesvirus 1 (HSV-1), this virus from humans can be lethal to New World monkey; 13% (37/283) were detected Callitrichine gammaherpesvirus 3 (CalHV-3), responsible for lymphoproliferative disease that can be fatal in NWP. In addition, CalHV-3 / HSV-1 co-infection was in 11.6% (33/283) of the samples.

MAIN CONCLUSIONS

Pan-herpesvirus was useful to identify species-specific herpesviruses and virus from human that can infect animals. Furthermore, during an outbreak of YF other infections should be monitored.

Fatal Human Alphaherpesvirus 1 Infection in Free-Ranging Black-Tufted Marmosets in Anthropized Environments, Brazil, 2012–2019

Human alphaherpesvirus 1 (HuAHV1) causes fatal neurologic infections in captive New World primates. To determine risks for interspecies transmission, we examined data for 13 free-ranging, black-tufted marmosets (Callithrix penicillata) that died of HuAHV1 infection and had been in close contact with humans in anthropized areas in Brazil during 2012–2019. We evaluated pathologic changes in the marmosets, localized virus and antigen, and assessed epidemiologic features. The main clinical findings were neurologic signs, necrotizing meningoencephalitis, and ulcerative glossitis; 1 animal had necrotizing hepatitis. Transmission electron microscopy revealed intranuclear herpetic inclusions, and immunostaining revealed HuAHV1 and herpesvirus particles in neurons, glial cells, tongue mucosal epithelium, and hepatocytes. PCR confirmed HuAHV1 infection. These findings illustrate how disruption of the One Health equilibrium in anthropized environments poses risks for interspecies virus transmission with potential spillover not only from animals to humans but also from humans to free-ranging nonhuman primates or other animals.

Yellow fever surveillance challenge: Investigation of a marmoset non-autochthonous case

Yellow fever (YF) surveillance in Brazil is focused mainly on the detection of epizootic events regarding New World non-human primates (NWNHP). We present a challenging case of a Callitrichidae (Callithrix spp) kept as a domiciliated pet that lived in the urban area of São Paulo municipality and was positive to YF virus by RT-qPCR and immunohistochemistry. After investigation, it was the first occurrence of non-autochthonous YF case of NWNHP described, with probable place of infection in the North shore of São Paulo state. This case illustrates the importance of coordinated laboratorial and field actions, and risks posed by transit of wildlife.

Infectious Disease Risk Across the Growing Human-Non Human Primate Interface: A Review of the Evidence

Most of the human pandemics reported to date can be classified as zoonoses. Among these, there is a long history of infectious diseases that have spread from non-human primates (NHP) to humans. For millennia, indigenous groups that depend on wildlife for their survival were exposed to the risk of NHP pathogens' transmission through animal hunting and wild meat consumption. Usually, exposure is of no consequence or is limited to mild infections. In rare situations, it can be more severe or even become a real public health concern. Since the emergence of acquired immune deficiency syndrome (AIDS), nobody can ignore that an emerging infectious diseases (EID) might spread from NHP into the human population. In large parts of Central Africa and Asia, wildlife remains the primary source of meat and income for millions of people living in rural areas. However, in the past few decades the risk of exposure to an NHP pathogen has taken on a new dimension. Unprecedented breaking down of natural barriers between NHP and humans has increased exposure to health risks for a much larger population, including people living in urban areas. There are several reasons for this: (i) due to road development and massive destruction of ecosystems for agricultural needs, wildlife and humans come into contact more frequently; (ii) due to ecological awareness, many long distance travelers are in search of wildlife discovery, with a particular fascination for African great apes; (iii) due to the attraction for ancient temples and mystical practices, others travelers visit Asian places colonized by NHP. In each case, there is a risk of pathogen transmission through a bite or another route of infection. Beside the individual risk of contracting a pathogen, there is also the possibility of starting a new pandemic. This article reviews the known cases of NHP pathogens' transmission to humans whether they are hunters, travelers, ecotourists, veterinarians, or scientists working on NHP. Although pathogen transmission is supposed to be a rare outcome, Rabies virus, Herpes B virus, Monkeypox virus, Ebola virus, or Yellow fever virus infections are of greater concern and require quick countermeasures from public health professionals.

Viral Diseases of Common Marmosets

Common marmosets are highly susceptible to several viral pathogens that exist as latent or subclinical infections in their natural reservoir hosts but cause severe disease or death when interspecies transmission occurs. Examples of such viruses in marmosets are herpes simplex virus infections, parainfluenza virus 1 infections, and measles acquired from humans, Saimiriine herpesvirus 1 infection after transmission from squirrel monkeys, and infections with lymphocytic choriomeningitis virus originating from mice. Other relevant viral infections causing spontaneous disease in common marmoset colonies include cowpox virus infections and paramyxovirus saguinus infections. Callitrichine herpesvirus 3 is a newly recognized lymphocryptovirus that is associated with the development of intestinal lymphoproliferative disease in common marmosets. Most viral pathogens causing disease in common marmosets are potential zoonotic agents, and protective measures should be implemented when handling these small New World monkeys.

Molecular evolution of fibropapilloma-associated herpesviruses infecting juvenile green and loggerhead sea turtles

Chelonid Alphaherpesvirus 5 (ChHV5) has long been associated with fibropapillomatosis (FP) tumor disease in marine turtles. Presenting primarily in juvenile animals, FP results in fibromas of the skin, connective tissue, and internal organs, which may indirectly affect fitness by obstructing normal turtle processes. ChHV5 is near-universally present in tumorous tissues taken from affected animals, often at very high concentrations. However, there is also considerable asymptomatic carriage amongst healthy marine turtles, suggesting that asymptomatic hosts play an important role in disease ecology. Currently, there is a paucity of studies investigating variation in viral genetics between diseased and asymptomatic hosts, which could potentially explain why only some ChHV5 infections lead to tumor formation. Here, we generated a database containing DNA from over 400 tissue samples taken from green and loggerhead marine turtles, including multiple tissue types, a twenty year time span, and both diseased and asymptomatic animals. We used two molecular detection techniques, quantitative (q)PCR and nested PCR, to characterize the presence and genetic lineage of ChHV5 in each sample. We found that nested PCR across multiple loci out-performed qPCR and is a more powerful technique for determining infection status. Phylogenetic reconstruction of three viral loci from all ChHV5-positive samples indicated widespread panmixia of viral lineages, with samples taken across decades, species, disease states, and tissues all falling within the same evolutionary lineages. Haplotype networks produced similar results in that viral haplotypes were shared across species, tissue types and disease states with no evidence that viral lineages associated significantly with disease dynamics. Additionally, tests of selection on viral gene trees indicated signals of selection dividing major clades, though this selection did not divide sample categories. Based on these data, neither the presence of ChHV5 infection nor neutral genetic divergence between viral lineages infecting a juvenile marine turtle is sufficient to explain the development of FP within an individual.

A model of genital herpes simplex virus Type 1 infection in Rhesus Macaques

BACKGROUND

Although HSV-2 is the major cause of genital lesions, HSV-1 accounts for half of new cases in developed countries.

METHODS

Three healthy SHIV-SF162P3-infected Indian rhesus macaques were inoculated with 4×108 pfu of HSV-1 twice, with the second inoculation performed after the vaginal mucosa was gently abraded with a cytobrush.

RESULTS

HSV-1 DNA was detected in vaginal swabs 5 days after the second but not the first inoculation in all three macaques. An increase in inflammatory cytokines was detected in the vaginal fluids of the animals with no or intermittent shedding. Higher frequency of blood α4 β7high CD4+ T cells was measured in the animals with consistent and intermitted shedding, while a decrease in the frequency of CD69+ CD4+ T cells was present in all animals.

CONCLUSIONS

This macaque model of genital HSV-1 could be useful to study the impact of the growing epidemic of genital HSV-1 on HIV infection.

Primates on display: Potential disease consequences beyond bushmeat

Human interactions with nonhuman primates vary tremendously, from daily cultural engagements and food commodities, to pet ownership and tourist encounters. These interactions provide opportunities for the exchange of pathogenic organisms (both zoonoses and anthroponoses). As exposures are not limited to areas where bushmeat usage continues to be a major problem, we must work to understand better our motivations for engaging in activities like owning primates as pets and having direct physical contact with wild primates within the context of nature-based tourism. These topics, and the theoretical potential for pathogen transmission, are reviewed in the present manuscript. This is followed by a case study utilizing 3845 survey responses collected from four international locations known for primate-based tourism, with results indicating that while a majority of people understand that they can give/get diseases to/from wild primates, a surprising percentage would still touch or feed these animals if given the opportunity. Many people still choose to touch and/or own primates, as their drive to bond with animals outweighs some basic health behaviors. Desires to tame, control, or otherwise establish emotional connections with other species, combined with the central role of touch for exploring our environment, necessitate the development of better communication and educational campaigns to minimize risks of emerging infectious diseases.

Understanding Primate Herpesviruses

Viruses related to the herpes simplex viruses of humans are present in all nonhuman primate (NHP) species tested and cross species transmission has been documented. The herpesvirus present in macaques, Herpes B virus (BV) rarely causes disease in its natural macaque host. However, when transmitted to a nonnative host, BV has occasionally caused severe and even fatal disease if not treated immediately. Here we present a comprehensive review of the taxonomy, molecular biology, physiology, epidemiology, diagnosis and treatment of BV. We also summarizes what is known about related herpesviruses of other NHP species and the zoonotic potential of these viruses.

Tales from the crypt and coral reef: the successes and challenges of identifying new herpesviruses using metagenomics

Herpesviruses are ubiquitous double-stranded DNA viruses infecting many animals, with the capacity to cause disease in both immunocompetent and immunocompromised hosts. Different herpesviruses have different cell tropisms, and have been detected in a diverse range of tissues and sample types. Metagenomics—encompassing viromics—analyses the nucleic acid of a tissue or other sample in an unbiased manner, making few or no prior assumptions about which viruses may be present in a sample. This approach has successfully discovered a number of novel herpesviruses. Furthermore, metagenomic analysis can identify herpesviruses with high degrees of sequence divergence from known herpesviruses and does not rely upon culturing large quantities of viral material. Metagenomics has had success in two areas of herpesvirus sequencing: firstly, the discovery of novel exogenous and endogenous herpesviruses in primates, bats and cnidarians; and secondly, in characterizing large areas of the genomes of herpesviruses previously only known from small fragments, revealing unexpected diversity. This review will discuss the successes and challenges of using metagenomics to identify novel herpesviruses, and future directions within the field.

Fatal Human herpesvirus 1 (HHV-1) infection in captive marmosets (Callithrix jacchus and Callithrix penicillata) in Brazil: clinical and pathological characterization

Fatal Human herpesvirus 1 (HHV-1) was diagnosed in 12 captive marmosets (Callithrix jacchus and Callithrix penicillata) from metropolitan region of São Paulo, São Paulo State. Clinical signs were variable among the cases, but most affected marmosets presented signs associated with viral epithelial replication: oral, lingual and facial skin ulcers and hypersalivation, and viral replication in the central nervous system: prostration, seizure and aggressive behavior. Consistent microscopic findings were diffuse mild to severe nonsuppurative necrotizing meningoencephalitis with gliosis, vasculitis and neuronal necrosis. Additionally, in the brain, oral cavity, skin, adrenal gland and myoenteric plexus intranuclear inclusion bodies were present. Immunohistochemistry confirmed the presence of the HHV-1 antigen in association with lesions in the brain, oral and lingual mucosa, facial skin, adrenal gland and myoenteric plexus. HHV-1-specific polymerase chain reaction (PCR) analysis of the brain was carried out and the virus was detected in 7/8 infected marmosets. It is concluded that HHV-1 causes widespread fatal infection in marmosets.

Herpes simplex virus type 1 infection in two pet marmosets in Japan

An 8-month-old common marmoset (Callithrix jacchus) was presented with tic-like symptoms, and a 2-year-old pigmy marmoset (Callithrix pygmaea) was presented with dyspnea and hypersalivation. Both monkeys died within a few days, and necropsies were performed. Histopathological examinations revealed ulcerative stomatitis with epithelial cell swelling and eosinophilic intranuclear inclusion bodies in the oral epithelium of both cases. In the central and peripheral nervous systems, neuronal cell degeneration with intranuclear inclusion bodies was observed. Immunohistochemical examination using anti-herpes simplex virus type 1 antibody revealed virus antigens in both cases. Both animals had been kept as pets with limited exposure to the ambient environment except via their owners. Therefore, herpes simplex virus type-1 was probably acquired from close contact with their owners.

Herpes B virus gD interaction with its human receptor--an in silico analysis approach

Background

The glycoprotein D (gD) is essential for Herpes B virus (BV) entry into mammalian cells. Nectin-1, an HSV-1 gD receptor, is found to be the receptor which mediated BV induced cell-cell fusion, while HVEM does not mediate fusion by BV glycoprotein. However, the specific sequence and structural requirements of the BV gD for the recognition of and binding to Nectin-1 are unknown. Moreover, the 3D structures of BV gD and the BV gD-receptor complex have not been determined. In this study, we propose a reliable model of the interaction of the BV gD with receptor using bioinformatics tools.

Results

The three-dimensional structures of two BV gD-receptor complexes were constructed using homology modelling and docking strategy. Based on the models of these complexes, the BV gD receptor interaction patterns were calculated. The results showed that the interface between the BV gD and nectin-1 molecule is not geometrically complementary. The computed molecular interactions indicated that two terminal extensions were the main region of BV gD that binds to nectin-1 and that hydrophobic contacts between the two molecules play key roles in their recognition and binding. The constructed BV gD-HVEM complex model showed that this complex had a lower shape complementarity value and a smaller interface area compared with the HSV-1 gD-HVEM complex, and the number of intermolecular interactions between BV gD-HVEM were fewer than that of HSV-1 gD-HVEM complex. These results could explain why HVEM does not function as a receptor for BV gD.

Conclusion

In this study, we present structural model for the BV gD in a complex with its receptor. Some features predicted by this model can explain previously reported experimental data. This complex model may lead to a better understanding of the function of BV gD and its interaction with receptor and will improve our understanding of the activation of the BV fusion and entry process.

Herpes B virus utilizes human nectin-1 but not HVEM or PILRα for cell-cell fusion and virus entry

To investigate the requirements of herpesvirus entry and fusion, the four homologous glycoproteins necessary for herpes simplex virus (HSV) fusion were cloned from herpes B virus (BV) (or macacine herpesvirus 1, previously known as cercopithecine herpesvirus 1) and cercopithecine herpesvirus 2 (CeHV-2), both related simian simplexviruses belonging to the alphaherpesvirus subfamily. Western blots and cell-based enzyme-linked immunosorbent assay (ELISA) showed that glycoproteins gB, gD, and gH/gL were expressed in whole-cell lysates and on the cell surface. Cell-cell fusion assays indicated that nectin-1, an HSV-1 gD receptor, mediated fusion of cells expressing glycoproteins from both BV and CeHV-2. However, herpesvirus entry mediator (HVEM), another HSV-1 gD receptor, did not facilitate BV- and CeHV-2-induced cell-cell fusion. Paired immunoglobulin-like type 2 receptor alpha (PILRα), an HSV-1 gB fusion receptor, did not mediate fusion of cells expressing glycoproteins from either simian virus. Productive infection with BV was possible only with nectin-1-expressing cells, indicating that nectin-1 mediated entry while HVEM and PILRα did not function as entry receptors. These results indicate that these alphaherpesviruses have differing preferences for entry receptors. The usage of the HSV-1 gD receptor nectin-1 may explain interspecies transfer of the viruses, and altered receptor usage may result in altered virulence, tropism, or pathogenesis in the new host. A heterotypic cell fusion assay resulting in productive fusion may provide insight into interactions that occur to trigger fusion. These findings may be of therapeutic significance for control of deadly BV infections.

Zoonotic diseases of primates

A zoonotic disease is transmissible from vertebrate animals to humans. This article focuses on pertinent zoonotic diseases that have to be taken into consideration when working with nonhuman primate (NHP) species. Many factors may influence the occurrence of these diseases. Human and NHPs share many similarities, not only anatomically but also physiologically. NHP are valuable models for many human infectious diseases; therefore, staff can be exposed to many potential pathogens. In general, the disease state of a primate can range from asymptomatic carrier to death from infection.

Natural zoonotic infections of two marmosets and one domestic rabbit with herpes simplex virus type 1 did not reveal a correlation with a certain gG-, gI- or gE genotype

Infections with herpes simplex virus type 1 (HSV-1) are not restricted to humans but infrequently may be transmitted to certain animal species, in some cases resulting in severe disease, including encephalitis and death. Recent studies demonstrate that humanderived HSV-1 field isolates can be typed according to their gG- gIand gE gene sequences. We investigated whether HSV-1 infections of animals were predominantly caused by a certain genotype. Isolates derived from two marmosets and one domestic rabbit, however, revealed different genotypes. Despite the very limited number of investigated animal-derived HSV-1 strains, this result does not point towards the existence of certain HSV-1 genotypes with a higher potential of being transmitted to animals.

The development of small primate models for aging research

Nonhuman primate (NHP) aging research has traditionally relied mainly on the rhesus macaque. But the long lifespan, low reproductive rate, and relatively large body size of macaques and related Old World monkeys make them less than ideal models for aging research. Manifold advantages would attend the use of smaller, more rapidly developing, shorter-lived NHP species in aging studies, not the least of which are lower cost and the ability to do shorter research projects. Arbitrarily defining "small" primates as those weighing less than 500 g, we assess small, relatively short-lived species among the prosimians and callitrichids for suitability as models for human aging research. Using the criteria of availability, knowledge about (and ease of) maintenance, the possibility of genetic manipulation (a hallmark of 21st century biology), and similarities to humans in the physiology of age-related changes, we suggest three species--two prosimians (Microcebus murinus and Galago senegalensis) and one New World monkey (Callithrix jacchus)--that deserve scrutiny for development as major NHP models for aging studies. We discuss one other New World monkey group, Cebus spp., that might also be an effective NHP model of aging as these species are longer-lived for their body size than any primate except humans.

Monkey B virus (Cercopithecine herpesvirus 1)

Macaques are a particularly valuable nonhuman primate model for a wide variety of biomedical research endeavors. B virus (Cercopithecine herpesvirus 1; BV) is an alpha-herpesvirus that naturally infects conventional populations of macaques. Serious disease due to BV is rare in macaques, but when transmitted to humans, BV has a propensity to invade the central nervous system and has a fatality rate greater than 70% if not treated promptly. The severe consequences of human BV infections led to the inclusion of BV in the original NIH list of target viruses for elimination by development of specific pathogen-free rhesus colonies. In macaques and especially in humans, diagnosis of BV infection is not straightforward. Furthermore, development and maintenance of true BV specific pathogen-free macaque colonies has proven dif cult. In this overview we review the natural history of BV in macaques, summarize what is known about the virus at the molecular level, and relate this information to problems associated with diagnosis of BV infections and development of BV-free macaque colonies.

Prevalence of enzootic simian viruses among urban performance monkeys in Indonesia

Animal reservoirs are the most important sources of emerging infectious diseases that threaten human populations. Global travel and tourism bring ever-increasing numbers of humans into contact with animals, increasing the likelihood of cross species transmission of infectious agents. Non-human primates come into contact with humans in a variety of contexts and may harbor infectious agents with zoonotic potential. We investigated the prevalence of infection with enzootic simian viruses among 20 urban performance monkeys (Macaca fascicularis) in Jakarta, Indonesia. This report documents for the first time evidence of infection with four simian viruses in urban performance monkeys. Simian foamy virus was detected by PCR in 52.9% of the macaques. Antibodies to simian retrovirus were detected in 10.5% of the macaques. Antibodies to Cercopithecine Herpesvirus 1, were detected in 5.3% of the macaques. Similarly, antibodies to simian T-cell lymphotropic virus were detected in 5.3% of the macaques. No evidence of infection with simian immunodeficiency virus was detected in these macaques. These results suggest that urban performance monkeys are a reservoir for enzootic simian viruses known to be capable of infecting humans.

Specific detection and identification of herpes B virus by a PCR-microplate hybridization assay

Herpes B virus DNA was specifically amplified by PCR, targeting the regions that did not cross-react with herpes simplex virus (HSV). The amplified products, which were shown to be highly genetic polymorphisms among herpes B virus isolates, were identified by microplate hybridization with probes generated by PCR. The products immobilized in microplate wells were hybridized with the biotin-labeled probes derived from the SMHV strain of herpes B virus. The amplified products derived from the SMHV and E2490 strains of herpes B virus were identified by microplate hybridization. PCR products amplified from the trigeminal ganglia of seropositive cynomolgus macaques were identified as herpes B virus DNA. The utility of the PCR-microplate hybridization assay for genetic detection and identification of the polymorphic region of herpes B virus was determined.

Cloning and expression of the complement receptor glycoprotein C from Herpesvirus simiae (herpes B virus): protection from complement-mediated cell lysis

Simian herpes B virus (SHBV) is the herpes simplex virus (HSV) homologue for the species MACACA: Unlike in its natural host, and unlike other animal herpesviruses, SHBV causes high mortality in accidentally infected humans. SHBV-infected cells, like those infected with HSV-1 and equine herpesvirus types 1 and 4, express complement C3 receptor activity. To study immunoregulatory functions involved in susceptibility/resistance against interspecies transmission, the SHBV glycoprotein C (gC(SHBV)) gene (encoding 467 aa) was isolated. Sequence analysis revealed amino acid identity with gC proteins from HSV-2 (46.9 %), HSV-1 (44.5 %) and pseudorabies virus (21.2 %). Highly conserved cysteine residues were also noted. Similar to gC(HSV-2), gC(SHBV) is less glycosylated than gC(HSV-1), resulting in a molecular mass of 65 kDa if expressed in replication-deficient vaccinia virus Ankara. Stable transfectants expressing full-length gC(SHBV) on the cell surface induced C3 receptor activity and were substantially protected from complement-mediated lysis; no protection was observed with control constructs. This suggests that expression of the gC homologues on infected cell surfaces might also contribute to the survival of infected cells in addition to decreased virion inactivation. Interestingly, soluble gC(SHBV) isolated from protein-free culture supernatants did not interfere with the binding of the alternative complement pathway activator properdin to C3b, which is similar to our findings with gC(HSV-2) and could be attributed to major differences in the amino-terminal portion of the protein with extended deletions in both gC(SHBV) and gC(HSV-2). Binding of recombinant gC(SHBV) to polysulphates was observed. This, together with the heparin-sensitivity of the gC(SHBV)-C3 interaction on the infected cell surface, suggests a role in adherence to heparan sulphate, similar to the gC proteins of other herpesviruses.

Role of viruses in human evolution

The study of viral molecular genetics has produced a considerable body of research into the sequences and phylogenetic relationships of human and animal viruses. A review of this literature suggests that humans have been afflicted by viruses throughout their evolutionary history, although the number and types have changed. Some viruses show evidence of long-standing intimate relationship and cospeciation with hominids, while others are more recently acquired from other species, including African monkeys and apes while our line was evolving in that continent, and domesticated animals and rodents since the Neolithic. Viral selection for specific resistance polymorphisms is unlikely, but in conjunction with other parasites, viruses have probably contributed to selection pressure maintaining major histocompatibility complex (MHC) diversity and a strong immune response. They may also have played a role in the loss in our lineage of N-glycolylneuraminic acid (Neu5Gc), a cell-surface receptor for many infectious agents. Shared viruses could have affected hominid species diversity both by promoting divergence and by weeding out less resistant host populations, while viruses carried by humans and other animals migrating out of Africa may have contributed to declines in other populations. Endogenous retroviral insertions since the divergence between humans and chimpanzees were capable of directly affecting hominid evolution through changes in gene expression and development.