Immunological relationship between herpes simplex virus and B virus

Questioning the Extreme Neurovirulence of Monkey B Virus (Macacine alphaherpesvirus 1)

Monkey B virus (Macacine alphaherpesvirus 1; BV) occurs naturally in macaques of the genus Macaca, which includes rhesus and long-tailed (cynomolgus) monkeys that are widely used in biomedical research. BV is closely related to the human herpes simplex viruses (HSV), and BV infections in its natural macaque host are quite similar to HSV infections in humans. Zoonotic BV is extremely rare, having been diagnosed in only a handful of North American facilities with the last documented case occurring in 1998. However, BV is notorious for its neurovirulence since zoonotic infections are serious, usually involving the central nervous system, and are frequently fatal. Little is known about factors underlying the extreme neurovirulence of BV in humans. Here we review what is actually known about the molecular biology of BV and viral factors affecting its neurovirulence. Based on what is known about related herpesviruses, areas for future research that may elucidate mechanisms underlying the neurovirulence of this intriguing virus are also reviewed.

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.

Detection and differentiation of primate alpha-herpesviruses by PCR

A rapid method for detection and differentiation of 5 primate alpha-herpesviruses (human herpes simplex virus types 1 and 2 [HSV1, HSV2], green monkey simian agent 8, baboon herpesvirus 2 [HVP2], and macaque B virus [BV]) was developed utilizing the polymerase chain reaction (PCR). PCR primers were located in conserved regions of the gene encoding the glycoprotein B, which flanks an intervening region that is highly divergent among the 5 viruses. Amplified PCR products from the 5 viruses were readily differentiated by their unique restriction enzyme digestion patterns. No variation in digestion patterns was noted among strains of HSV1, HSV2, or HVP2. One clinical isolate of BV exhibited variation in a single restriction site, but its overall restriction pattern remained typical of BV. This method (PCR/RFLP) allowed the presence of herpesvirus DNA in clinical swabs from primates to be readily detected and the virus unambiguously identified.

Relatedness of glycoproteins expressed on the surface of simian herpes-virus virions and infected cells to specific HSV glycoproteins

The antigenic relatedness of the surface glycoprotein antigens of six herpesviruses indigenous to human and nonhuman primates was examined. Binding of anti-viral sera to viral antigens expressed on the surface of infected cells demonstrated that the surface antigens of herpes simplex virus type 1 (HSV 1), HSV 2, simian agent 8 (SA8), and Herpesvirus simiae (B virus) exhibit extensive cross-reactivity. Surface antigens of two viruses isolated from South American primates, H. saimiri 1 (HVS 1) and H. ateles 1 (HVA 1), were comparatively more virus-specific in their antigenic reactivity. Endpoint neutralization tests performed in the presence and absence of complement confirmed these results. Immunoprecipitation of viral proteins was used to identify those representing cross-reactive surface antigens. A glycoprotein of approximately 110,000-125,000 Daltons (110-125 k) was immunoprecipitated from cells infected with each of the six primate herpesvirus by antisera to each of the viruses. Using monospecific antisera, these glycoproteins were shown to be antigenically related to the gB glycoproteins of HSV. Although these glycoproteins were antigenically conserved among all six viruses, antibodies to the gB glycoproteins did not cross-neutralize heterologous viruses. A glycoprotein of approximately 60-70 k was precipitated from HSV 1, HSV 2, SA8, and B virus infected cells by antisera to each of these four viruses. These SA8 and B virus glycoproteins were shown to be antigenically related to the gD glycoproteins of HSV 1 and HSV 2 and to be involved in cross-neutralization among these viruses. Antisera to HVS 1 and HVA 1 did not recognize these gD glycoproteins nor was a glycoprotein of similar molecular weight precipitable from HVS 1 or HVA 1 infected cells by antisera to the other four viruses. Southern blot hybridizations using probes for HSV glycoprotein genes confirmed the conservation of the gB glycoproteins among all the simian viruses and of the gD gene in SA8 and B virus. A glycoprotein of approximately 75-80 k was, however, precipitated from HVS 1 and HVA 1 infected cells by antisera to either of these two viruses. In addition, at least one glycoprotein which appeared to be predominantly virus-specific in its reactivity was identified for five of the viruses.

Simian alphaherpesviruses and their relation to the human herpes simplex viruses

Biochemical and immunological properties of structural and non-structural polypeptides of the human simplex viruses (HSV1 and HSV2) and four related herpesviruses of non-human primates [Herpesvirus simiae (B virus), H. cercopithicus (SA8), H. saimiri 1 (HVS 1), and H. ateles 1 (HVA 1)] were compared. Using a radioimmunoassay (RIA), the presence of antigenic determinants shared among all six viruses was demonstrated. The relative degree of antigenic cross-reactivity among these viruses was further assessed by competition RIA. Antigenically, HSV 1 and HSV 2 were most closely related to each other although both SA 8 and B virus were also very closely related to HSV 1. Considerably less cross-reactivity existed between either HVS 1 or HVA 1 and the other four primate herpesviruses. Cross-hybridization between simian and human herpesvirus genomes demonstrated that extensive homology exists between each of the simian viruses and both HSV1 and HSV 2. Viral polypeptides bearing common antigenic determinants were identified by immune precipitation of infected cell polypeptides and by immunoblotting. Among the polypeptides of HSV which were recognized by antisera to simian viruses were the VP 5 and p40 proteins, both of which are structural components of the virion nucleocapsid. Using recombinant plasmids containing sequences of the HSV 1 VP5, p40, DNA polymerase, major DNA binding protein, and TK enzyme genes, homologous sequences were detected in all four simian viruses. Together, these results demonstrate that HSV 1, HSV 2, SA 8, and B virus form a closely related sub-group of the primate herpesviruses; HVS 1 and HVA 1 are also related to the other four primate herpesviruses, albeit more distantly.

Herpesvirus simiae (B virus): replication of the virus and identification of viral polypeptides in infected cells

The events and products of replication of Herpesvirus simiae (B virus) in Vero cells were studied. The time course of the synthetic events of DNA replication and protein synthesis were found to be similar to the processes of the herpes simplex viruses and SA 8. Infectious progeny virus were detected by 4 hours post infection and were first found extracellularly between 6 and 8 hours post infection (PI). As in the case of SA 8, all cell lines tested were permissive for lytic infection by B virus. Analyses of B virus-infected cells by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) revealed approximately 50 infected cell polypeptides (ICP) ranging in molecular weight from about 26,000 to 239,000 daltons. The kinetics of synthesis of the ICPs were also identified. At least nine glucosamine-containing glycopeptides were noted ranging from 133,000 to 29,000 daltons.

Serological survey for SV5, measles and herpes simplex infections in newly-imported cynomolgus monkeys

On 592 cynomolgus monkeys of newly-imported 14 different groups, sero-epidemiological follow-up surveys of natural infections with SV5, measles (MV) and herpes simplex (HSV) were conducted both at the time of arrival and at the end of the 9-week quarantine period at Tsukuba Primate Center for Medical Science (TPC). At the time of arrival, the positive rate of antibodies against these viruses greatly varied with different countries of origin. As regards SV5, the positive rate ranged widely from 0 to 94.9% among different import-groups, being markedly low in the Philippine monkey groups. The positive rate of MV antibody was generally very high, varying from 11.1 to 78.2% in almost all import-groups except two groups from Indonesia in which no positive case was detected. Concerning HSV, every import-group had a very high positive rate though the average antibody titer was not so high. Generally, the positive rates of SV5 and MV markedly increased by the end of quarantine period. Especially, MV positive rate reached 100% in almost all of the import-groups. However, two Indonesian groups showed no increase of SV5 and MV positive rates during the quarantine period. No increase of SV5 positive rate was detected either with any of three Philippine groups. As for HSV, the positive rate remained unchanged or rather decreased during the quarantine period in almost all groups except two Indonesian groups having shown a significant increase.

Induction of skin resistance to vaccinia virus in rabbits by vaccinia-soluble early antigens

The immunological role of vaccinia-soluble early antigen was examined in rabbits. The antigens were prepared from HeLa cells infected with a conditional lethal mutant of vaccinia virus, which induces in these cells early antigens including those responsible for surface immunofluorescence of infected cells, but not viral DNA and late protein syntheses. Immunization of rabbits with the antigens in Freund's complete adjuvant induced complement-fixing antibody but neither detectable circulating neutralizing antibody nor any detectable level of inhibitory substance or interferon in the skin of the animals. When immunized animals were inoculated intradermally with vaccinia virus, multiplication of virus in the skin was greatly inhibited, being accompanied by an earlier appearance as well as an accelerated wane of the local reactions. The resistance could not be transferred passively by the serum of immunized animals to normal rabbits. Immunization of rabbits with the antigens without the adjuvant not only failed to inhibit but, contrariwise, enhanced the multiplication of intradermally inoculated vaccinia virus, inducing heavy skin lesions and exalted virus multiplication.

Surface antigens produced by Herpesviruses Varicella-Zoster virus

Surface antigen(s) was demonstrated by the mixed agglutination technique on cell cultures infected with varicella-zoster virus (V-Z). The reactions appeared to be specific for V-Z, and no cross-reaction was obtained with herpes simplex virus (HSV). V-Z surface antigen had similar physicochemical properties to that of HSV. It was stable to heating at 56 C and treatment with 1% Formalin, 2,4-dinitrophenol, and periodate, whereas it was undetectable after exposure to acetone or ethanol. Antibodies detecting surface antigen were present in high titer in sera from varicella or herpes zoster patients and paralleled titers obtained by the complement fixation test.

Sero-epidemiological survey on Yaba and 1211 virus infections among several species of monkeys

The distribution of neutralizing antibody to Yaba virus and 1211 agent in the sera of three Asian and one African monkey species was examined.Cynomolgus (Macaca irus), bonnet (M. radiata) and rhesus (M. mulatta) monkeys possessed antibody to Yaba virus at incidences of 19.9, 8.4 and 0%, respectively. In African green monkeys (Cercopithecus aethiops) the incidence was as high as 76.4%.As for 1211 agent, no Asian monkeys had neutralizing antibody and 5.5% of African green monkey sera neutralized the virus.